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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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19 pages, 7052 KiB

Open AccessEditor’s ChoiceArticle

Simulation Analysis of Skew Collision of Needle Roller Bearing Used in Precision Cycloid Reducer

by Yue Sun, Ying-Hui Zhang and Wei-Dong He

Machines 2023, 11(4), 419; https://doi.org/10.3390/machines11040419 - 24 Mar 2023

Cited by 2 | Viewed by 1617

In order to improve the service life of the needle roller bearing used in a precision cycloid reducer, and to reveal the skew and collision phenomenon of the needle roller bearing, based on the force analysis of the transmission mechanism of the cycloid [...] Read more.

In order to improve the service life of the needle roller bearing used in a precision cycloid reducer, and to reveal the skew and collision phenomenon of the needle roller bearing, based on the force analysis of the transmission mechanism of the cycloid reducer and considering the friction between the cycloid wheel, needle roller, cage, and crank shaft, the dynamic contact between the rolling bodies is simulated by the Hertz elastic contact, where the contact between the cage pocket hole and needle roller is equivalent to the spring and damping, and a nonlinear dynamic model of the needle roller bearing is established. The influence of different load and cage clearances on the deflection impact of the rotating needle roller bearing is calculated. The results show that the inclination of rollers is different under different pocket clearances, and the larger the pocket gap, the greater the fluctuation of the roller inclination angle; the action force of the crank shaft on the roller suppresses the deflection of the roller; the impact force of the roller on the cage has periodicity, which is consistent with the impact force of the crank shaft on the roller. The impact force of the cage is different under different loads, and the greater the load, the more rollers there are in the bearing area, the larger the impact force is, and the smaller the impact force of the rollers in the middle of the bearing zone is, compared with that of the rollers on the two sides; when the load is small, a pocket cage gap of 0.3 mm is selected, and when the load is heavy, a pocket cage gap of 0.2 mm is selected in order to make the bearing run more smoothly. Full article

(This article belongs to the Section Machine Design and Theory)

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23 pages, 11426 KiB

Open AccessEditor’s ChoiceArticle

Design and Experimental Validation of a Rapidly Deployable Folding Floating Bridge Based on Rigid-Flexible Combination

by Chenxin Wang, Haiyue Hu and Jin Gan

Machines 2023, 11(4), 415; https://doi.org/10.3390/machines11040415 - 23 Mar 2023

Viewed by 2311

As a temporary means of water transportation, floating bridges play an important role in the military and other fields. However, traditional floating bridges have limitations such as large size, heavy weight, and slow construction time. In this paper, we propose a rigid-flexible composite [...] Read more.

As a temporary means of water transportation, floating bridges play an important role in the military and other fields. However, traditional floating bridges have limitations such as large size, heavy weight, and slow construction time. In this paper, we propose a rigid-flexible composite folding floating bridge. The main structure of the floating bridge consists of three layers: the bridge deck, airbag, and water bag. The floating bridge units are connected by flexible connectors to allow for pre-connection and folding of the bridge, reducing storage and transportation space, and improving construction efficiency. The proposed floating bridge also has a complete engineering application design and has been checked for safety and reliability (including the strength, buoyancy, and bearing capacity of the connections). We used AQWA software to simulate and analyze the anchorage scheme of the floating bridge and its response to wave loads and conducted a ballast test on a floating bridge model to verify its feasibility as a main bearing body. The results show that the floating bridge we designed has the advantages of being lightweight, having fewer consumables, having a small storage and transportation space, and being able to be constructed quickly. Full article

(This article belongs to the Section Machine Design and Theory)

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14 pages, 4185 KiB

Open AccessEditor’s ChoiceArticle

Detection for Disc Cutter Wear of TBM Using Magnetic Force

by Jialin Han, Hongjiang Xiang, Qiuyue Feng, Jiangbo He, Rong Li and Wensheng Zhao

Machines 2023, 11(3), 388; https://doi.org/10.3390/machines11030388 - 15 Mar 2023

Cited by 2 | Viewed by 1847

To replace the worn-out cutter of tunnel boring machines timely, it is crucial to inspect the cutter’s wear. In this work, a novel detection method based on magnetic force is proposed to overcome the drawback of nonlinearity in current detecting technology. The principle [...] Read more.

To replace the worn-out cutter of tunnel boring machines timely, it is crucial to inspect the cutter’s wear. In this work, a novel detection method based on magnetic force is proposed to overcome the drawback of nonlinearity in current detecting technology. The principle is that the magnetic force between the cutter and the permanent magnet linearly decreases with increasing wear. Firstly, the magnetic force is investigated by the finite element simulation to find the optimal placement of the permanent magnet to realize both high linearity and sensitivity. Secondly, a highly-sensitive force sensor with an S shape is designed to measure the magnetic force. The four strain gauges in the force sensor are combined into a Wheatstone bridge to suppress the common-mode effect, such as temperature. Experimental testing on the magnetic force is performed to verify the feasibility of the detection method. The testing result shows that the magnetic force linearly decreases with the increasing wear loss at a rate of −793 mN/mm. The accuracy of the detecting method approaches 1 mm, which is of the same order of magnitude as those in previous studies. Full article

(This article belongs to the Special Issue Tool Wear in Machining)

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30 pages, 11343 KiB

Open AccessEditor’s ChoiceArticle

The Viability of a Grid of Autonomous Ground-Tethered UAV Platforms in Agricultural Pest Bird Control

by Joshua Trethowan, Zihao Wang and K. C. Wong

Machines 2023, 11(3), 377; https://doi.org/10.3390/machines11030377 - 11 Mar 2023

Cited by 3 | Viewed by 2136

Pest birds are a salient problem in agriculture all around the world due to the damage they can cause to commercial or high-value crops. Recent advancements in Unmanned Aerial Vehicles (UAVs) have motivated the use of drones in pest bird deterrence, with promising [...] Read more.

Pest birds are a salient problem in agriculture all around the world due to the damage they can cause to commercial or high-value crops. Recent advancements in Unmanned Aerial Vehicles (UAVs) have motivated the use of drones in pest bird deterrence, with promising success already being demonstrated over traditional bird control techniques. This paper presents a novel bird deterrence solution in the form of tethered UAVs, which are attached and arranged in a grid-like fashion across a vineyard property. This strategy aims to bypass the power and endurance limitations of untethered drones while still utilising their dynamism and scaring potential. A simulation model has been designed and developed to assess the feasibility of different UAV arrangements, configurations, and strategies against expected behavioural responses of incoming bird flocks, despite operational and spatial constraints imposed by a tether. Attempts at quantifying bird persistence and relative effort following UAV-induced deterrence are also introduced through a novel bird energy expenditure model. This aims to serve as a proxy for selecting control techniques that reduce future foraging missions. The simulation model successfully isolated candidate configurations, which were able to deter both single and multiple incoming bird flocks using a centralised multi-UAV control strategy. Overall, this study indicates that a grid of autonomous ground-tethered UAV platforms is viable as a bird deterrence solution in agriculture, a novel solution not seen nor dealt with elsewhere to the authors’ knowledge. Full article

(This article belongs to the Special Issue Advances and Applications in Unmanned Aerial Vehicles)

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20 pages, 6534 KiB

Open AccessEditor’s ChoiceArticle

Observer-Based Controller Using Line Integral Lyapunov Fuzzy Function for TS Fuzzy Systems: Application to Induction Motors

by Rabiaa Houili, Mohamed Yacine Hammoudi, Mohamed Benbouzid and Abdennacer Titaouine

Machines 2023, 11(3), 374; https://doi.org/10.3390/machines11030374 - 10 Mar 2023

Viewed by 1633

This paper deals with the stabilization problem of a nonlinear system described by a Takagi–Sugeno fuzzy (TSF) model with unmeasurable premise variables via a robust controller. Applying the sector nonlinearity techniques, the nonlinear system is represented by a decoupled fuzzy model. Then, we [...] Read more.

This paper deals with the stabilization problem of a nonlinear system described by a Takagi–Sugeno fuzzy (TSF) model with unmeasurable premise variables via a robust controller. Applying the sector nonlinearity techniques, the nonlinear system is represented by a decoupled fuzzy model. Then, we design a robust observer-based controller for the obtained fuzzy system by utilizing the differential mean value approach. The observer and controller gains are obtained by the separation principle, in which the problem is solved in the sum of linear matrix inequalities (LMIs). The paper presents two main contributions: A state feedback controller is designed using differential mean value (DMVT) which ensures robust stabilization of the nonlinear system. Additionally, the Luenberger observer is extended to the Takagi–Sugeno fuzzy models. The second contribution is to reduce conservatism in the obtained conditions, a non-quadratic Lyapunov function (known as the line integral Lyapunov fuzzy candidate (LILF)) is employed. Two examples are provided to further illustrate the efficiency and robustness of the proposed approach; specifically, the Takagi–Sugeno fuzzy descriptor of an induction motor is derived and a robust observer-based controller applied to the original nonlinear system. Full article

(This article belongs to the Special Issue 10th Anniversary of Machines—Feature Papers in Electrical Machines and Drives)

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16 pages, 6332 KiB

Open AccessEditor’s ChoiceArticle

Modeling and Analysis of a Novel 3R Parallel Compliant Mechanism

by Lanqing Pan, James W. Zhang, Dan Zhang and Hongyan Tang

Machines 2023, 11(3), 375; https://doi.org/10.3390/machines11030375 - 10 Mar 2023

Cited by 2 | Viewed by 1869

This paper presents and investigates a new three-rotation (3R) parallel compliant mechanism that uses compliant rods to achieve three rotations. The mechanism is designed for use in pointing devices or as a spatial parallel manipulator. The mobility analysis is based on the Cosserat [...] Read more.

This paper presents and investigates a new three-rotation (3R) parallel compliant mechanism that uses compliant rods to achieve three rotations. The mechanism is designed for use in pointing devices or as a spatial parallel manipulator. The mobility analysis is based on the Cosserat rod model and Lagrangian dynamics equations. The dynamics equations are then effectively solved using the back-propagation neural network and chaos-enhanced accelerated particle swarm optimization. After studying the mobility of the moving platform, a simplified model is proposed and used for kinematic analysis. The analysis of motion includes discussions on forward kinematics, inverse kinematics, singularities, and the workspace. Furthermore, experiments with a prototype are conducted to verify the accuracy and stability of the mobility analysis and the simplified model. Full article

(This article belongs to the Section Automation and Control Systems)

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18 pages, 9443 KiB

Open AccessEditor’s ChoiceArticle

Yaw Rate Prediction and Tilting Feedforward Synchronous Control of Narrow Tilting Vehicle Based on RNN

by Ruolin Gao, Haitao Li, Ya Wang, Shaobing Xu, Wenjun Wei, Xiao Zhang and Na Li

Machines 2023, 11(3), 370; https://doi.org/10.3390/machines11030370 - 9 Mar 2023

Cited by 1 | Viewed by 1705

The synchronous control of yaw motion and tilting motion is an important problem related to the lateral stability and energy consumption of narrow tilting vehicles. This paper proposes a method for the tilting control of narrow tilting vehicles: tilting feedforward synchronous control. This [...] Read more.

The synchronous control of yaw motion and tilting motion is an important problem related to the lateral stability and energy consumption of narrow tilting vehicles. This paper proposes a method for the tilting control of narrow tilting vehicles: tilting feedforward synchronous control. This method utilizes a proposed novel prediction method for yaw rate based on a recurrent neural network. Meanwhile, considering that classical recurrent neural networks can only predict yaw rate at a given time, and that yaw rate prediction generally needs to analyze a large amount of computer vision data, in this paper, the yaw rate is represented by a polynomial operation to predict the continuous yaw rate in the time domain; this prediction is realized using only the driving data of the vehicle itself and does not include the data generated by computer vision. A prototype experiment is provided in this work to prove the advantages and feasibility of the proposed tilting feedforward synchronous control method for narrow tilting vehicles. The proposed tilting feedforward synchronous control method can ensure the synchronous response of the yaw motion and the tilting motion of narrow tilting vehicles. Full article

(This article belongs to the Special Issue Adaptive and Optimal Control of Vehicles)

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25 pages, 10110 KiB

Open AccessEditor’s ChoiceArticle

Frame Angular Velocity Control Design of SGCMG for Unmanned Two-Wheeled Motorcycle

by Bao Chen, Xiang Fei, Yiming Fan, Yuanhong Dan and Zehao Huang

Machines 2023, 11(3), 371; https://doi.org/10.3390/machines11030371 - 9 Mar 2023

Viewed by 1606

In contrast to driverless cars and other three-wheeled and four-wheeled motorcycle vehicles, driverless two-wheeled motorcycles have the problem of maintaining balance. In this paper, we propose the design of an SGCMG frame angular velocity controller to realize the balance control of the motorcycle [...] Read more.

In contrast to driverless cars and other three-wheeled and four-wheeled motorcycle vehicles, driverless two-wheeled motorcycles have the problem of maintaining balance. In this paper, we propose the design of an SGCMG frame angular velocity controller to realize the balance control of the motorcycle under static and dynamic working conditions. Meanwhile, since the roll angular acceleration of the actual body movement of the cross roll cannot be obtained directly, this paper proposes a Kalman filtering method based on the nonlinear dynamics model of the motorcycle to obtain a reliable angular acceleration signal. First, we modeled the dynamics of the motorcycle by analyzing the various types of moments generated by the motorcycle equipped with the SGCMG under static and dynamic conditions; Then, the design of the angular velocity control of the SGCMG frame was carried out with the feedback and through MATLAB/Simulink simulation to restore various types of actual working conditions to verify the controller has good robustness; Finally, we have completed the test of the controller using the above filtering method on the real vehicle with an embedded system and compared the effect with other controllers, obtained the results that the body is stable and balanced under static conditions and the applied load can automatically find a new balance point, so as to prove the effectiveness of the designed control. Full article

(This article belongs to the Special Issue Noise and Vibration Control in Dynamic Systems)

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14 pages, 4422 KiB

Open AccessEditor’s ChoiceArticle

Design and Verification of Adaptive Adjustable Output Control on Micro Spray Gun

by Jiun-Hung Lin, Chih-Hong Chen and Shih-Tsang Tang

Machines 2023, 11(3), 354; https://doi.org/10.3390/machines11030354 - 4 Mar 2023

Viewed by 1686

The general spray gun is used for industrial large-area spraying, and there is less demand for different pressures and the accuracy of spraying pressure, so mechanical pressure regulators are mostly used. However, as the demand for artistic innovation continues to grow, it promotes [...] Read more.

The general spray gun is used for industrial large-area spraying, and there is less demand for different pressures and the accuracy of spraying pressure, so mechanical pressure regulators are mostly used. However, as the demand for artistic innovation continues to grow, it promotes the advent of the micro spray gun. The micro spray gun is currently commonly known as an airbrush. The micro spray gun is mainly used for fine drawing, so it must provide different pressures with high precision pressures, but the existing mechanical regulators cannot meet this requirement. For these unmet requirements, this study proposed a solution for PID (proportional-integral-derivative) control micro spray gun system. The results showed that the PID control could effectively provide various stable output pressures of the micro spray gun. The pressure-varying range of 30 kPa could rapidly return to the target value in 10 s (the usual spraying time). The proposed solution then presents better spraying effects. Full article

(This article belongs to the Topic Designs and Drive Control of Electromechanical Machines)

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23 pages, 1293 KiB

Open AccessEditor’s ChoiceArticle

Robust Control of UAV with Disturbances and Uncertainty Estimation

by Domenico Bianchi, Stefano Di Gennaro, Mario Di Ferdinando and Cuauhtémoc Acosta Lùa

Machines 2023, 11(3), 352; https://doi.org/10.3390/machines11030352 - 3 Mar 2023

Cited by 12 | Viewed by 3132

In this work, a nonlinear estimator-based robust controller is designed for the position and yaw control of a quadrotor with uncertainty estimation. This controller ensures the tracking of desired references in the presence of parameters variation and external disturbances, making use of high-order [...] Read more.

In this work, a nonlinear estimator-based robust controller is designed for the position and yaw control of a quadrotor with uncertainty estimation. This controller ensures the tracking of desired references in the presence of parameters variation and external disturbances, making use of high-order sliding mode (HOSM) estimators to estimate these perturbations that can be canceled by the control, thus improving the dynamic behavior of the controlled system. Its performance is evaluated making use of a Simcenter Amesim quadrotor based on physical models generated from experimental data in a co-simulation framework with Matlab–Simulink used to implement the designed controller with FPGA implementation. A challenging and generic maneuver with time-varying wind disturbances and uncertainty model parameters is considered. Full article

(This article belongs to the Special Issue Robust Control of Robotic and Complex Mechatronic Systems)

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23 pages, 9344 KiB

Open AccessEditor’s ChoiceArticle

Online Estimation of Three-Directional Tire Forces Based on a Self-Organizing Neural Network

by Guiyang Wang, Shaohua Li and Guizhen Feng

Machines 2023, 11(3), 344; https://doi.org/10.3390/machines11030344 - 2 Mar 2023

Cited by 2 | Viewed by 1749

The road friction coefficient and the forces between the tire and the road have a significant impact on the stability and precise control of the vehicle. For four-wheel independent drive electric vehicles, an adaptive tire force calculation method based on the improved Levenberg–Marquarelt [...] Read more.

The road friction coefficient and the forces between the tire and the road have a significant impact on the stability and precise control of the vehicle. For four-wheel independent drive electric vehicles, an adaptive tire force calculation method based on the improved Levenberg–Marquarelt multi-module and self-organizing feedforward neural networks (LM-MMSOFNN) was proposed to estimate the three-directional tire forces of four wheels. The input data was provided by common sensors amounted on the autonomous vehicle, including the inertial measurement unit (IMU) and the wheel speed/rotation angle sensors (WSS, WAS). The road type was recognized through the road friction coefficient based on the vehicle dynamics model and Dugoff tire model, and then the tire force was calculated by the neural network. The computational complexity and storage space of the system were also reduced by the improved LM learning algorithm and self-organizing neurons. The estimation accuracy was further improved by using the Extended Kalman Filter (EKF) and Moving Average (MA). The performance of the proposed LM-MMSOFNN was verified through simulations and experiments. The results confirmed that the proposed method was capable of extracting important information from the sensors to estimate three-directional tire forces and accurately adapt to different road surfaces. Full article

(This article belongs to the Section Vehicle Engineering)

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25 pages, 19710 KiB

Open AccessEditor’s ChoiceArticle

Nonlinear Dynamic Characteristics of Deep Groove Ball Bearings with an Improved Contact Model

by Wentao Shan, Yu Chen, Xiuying Wang, Chengtao Yu, Kai Wu and Zhenhua Han

Machines 2023, 11(3), 340; https://doi.org/10.3390/machines11030340 - 1 Mar 2023

Cited by 4 | Viewed by 3121

In this paper, the nonlinear dynamic response of deep groove ball bearings with clearance was studied numerically. The imperfect connections with the clearance of raceways and rolling balls were established by the contact elements. In order to describe the contact characteristics accurately, a [...] Read more.

In this paper, the nonlinear dynamic response of deep groove ball bearings with clearance was studied numerically. The imperfect connections with the clearance of raceways and rolling balls were established by the contact elements. In order to describe the contact characteristics accurately, a hysteresis damping coefficient was introduced into the Hertz contact model, which represented the dissipative term during the contact–impact process. The tangential force of the contact bodies was obtained based on a modified Coulomb friction model. Then, the dynamic analysis model of the deep groove ball bearings with clearance was built. Meanwhile, the experimental test platform of the deep groove ball bearings with various operation conditions was built and the dynamic simulation was utilized as the demonstrative case to conduct the investigation. The numerical results revealed that the existence of clearance would change the motion trajectory of a rolling ball and the appearance of the different movement states (free, contact, and penetration). In addition, the contact characteristics and sliding features would be changed with the variations in the operation conditions and structural characteristics. Full article

(This article belongs to the Special Issue Friction and Lubrication of Mechanical Drive Train Components)

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19 pages, 2211 KiB

Open AccessEditor’s ChoiceArticle

Minimum Dynamic Cable Tension Workspace Generation Techniques and Cable Tension Sensitivity Analysis Methods for Cable-Suspended Gangue-Sorting Robots

by Peng Liu, Hongwei Ma, Xiangang Cao, Xuhui Zhang, Xuechao Duan and Zhen Nie

Machines 2023, 11(3), 338; https://doi.org/10.3390/machines11030338 - 1 Mar 2023

Cited by 2 | Viewed by 1287

The separation of gangues from coals with robots is an effective and practicable means. Therefore, a cable-suspended gangue-sorting robot (CSGSR) with an end-grab was developed in our early work. Due to the unidirectional characteristic, the flexibility of cables, and the dynamic impact of [...] Read more.

The separation of gangues from coals with robots is an effective and practicable means. Therefore, a cable-suspended gangue-sorting robot (CSGSR) with an end-grab was developed in our early work. Due to the unidirectional characteristic, the flexibility of cables, and the dynamic impact of pick-and-place gangues, one of the significant issues with the robots is robustness under internal and external disturbances. Cable tensions, being the end-grab’s constraints, have a crucial effect on the robustness of the CSGSR while disturbances are on. Two main issues related to the CSGSR, as a result, are addressed in the present paper: minimum dynamic cable tension workspace generation and a sensitivity analysis method for the dynamic cable tensions. Firstly, the four cable tensions and minimum dynamic cable tension while the end-grab was located at an arbitrary position of the task space were obtained with the dynamics of the CSGSR. In addition, with the dynamics of the CSGSR, a minimum dynamic cable tension workspace (MDCTW) generating approach is presented, where the minimum dynamic cable tensions are greater than a preset value, therefore ensuring the robustness of the end-grab under the disturbances. Secondly, a method for dynamic cable tension sensitivity (DCTS) of the robots is proposed with grey relational analysis, by which the influence degree of the end-grab’s positions on the four dynamic cable tensions and the minimum dynamic cable tensions was considered. Finally, the effectiveness of the proposed MDCTW generation algorithm and the DCTS analysis method were examined through simulation on the CSGSR, and it was indicated that the proposed MDCTW generation algorithm and the DCTS analysis method were able to provide theoretical guidance for pick-and-place trajectory planning and generation of the end-grab in practice. Full article

(This article belongs to the Special Issue Development and Applications of Parallel Robots)

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21 pages, 5538 KiB

Open AccessEditor’s ChoiceReview

Review on Wearable System for Positioning Ultrasound Scanner

by Lailu Li, Lei Zhao, Rayan Hassan and Hongliang Ren

Machines 2023, 11(3), 325; https://doi.org/10.3390/machines11030325 - 24 Feb 2023

Cited by 7 | Viewed by 6952

Although ultrasound (US) scan or diagnosis became widely employed in the 20th century, it still plays a crucial part in modern medical diagnostics, serving as a diagnostic tool or a therapy process guide. This review provides information on current wearable technologies and applications [...] Read more.

Although ultrasound (US) scan or diagnosis became widely employed in the 20th century, it still plays a crucial part in modern medical diagnostics, serving as a diagnostic tool or a therapy process guide. This review provides information on current wearable technologies and applications used in external ultrasound scanning. It offers thorough explanations that could help build upon any project utilizing wearable external US devices. It touches on several aspects of US scanning and reviews basic medical procedure concepts. The paper starts with a detailed overview of ultrasound principles, including the propagation speed of sound waves, sound wave interactions, image resolution, transducers, and probe positioning. After that, it explores wearable external US mounts and wearable external US transducers applied for sonograph purposes. The subsequent section tackles artificial intelligence methods in wearable US scanners. Finally, future external US scan directions are reported, focusing on hardware and software. Full article

(This article belongs to the Section Automation and Control Systems)

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16 pages, 7118 KiB

Open AccessEditor’s ChoiceArticle

Typical Fault Modeling and Vibration Characteristics of the Turbocharger Rotor System

by Jiahao Wang, Huabing Wen, Haiyu Qian, Junhua Guo, Junchao Zhu, Jiwei Dong and Hua Shen

Machines 2023, 11(2), 311; https://doi.org/10.3390/machines11020311 - 20 Feb 2023

Cited by 2 | Viewed by 1550

To study the typical failure mechanism (rotor unbalance, rotor friction, and rotor crack) and vibration characteristics of the turbocharger rotor system, a rotor system dynamics simulation model was established by an improved four-node aggregate parameter method. The geometric and physical characteristics of the [...] Read more.

To study the typical failure mechanism (rotor unbalance, rotor friction, and rotor crack) and vibration characteristics of the turbocharger rotor system, a rotor system dynamics simulation model was established by an improved four-node aggregate parameter method. The geometric and physical characteristics of the rotor system under three failure states and its dynamics under operation were analyzed. Thus, a typical failure dynamics simulation model of the rotor system was established. On this basis, the output failure simulation signal was extracted using the Hu invariant moment feature extraction method to analyze the system vibration characteristics under each typical failure state of the rotor system. The results show that the model in this paper can effectively reduce the computational volume and computational time, and the errors of numerical simulation were less than 3%. When an unbalance fault occurred in the rotor system, the shaft trajectory was “0” shaped and the response spectrum was dominated by 1X. When the rotor system was frictional, the shaft trajectory was a slightly concave “8” shape, and the response spectrum was dominated by 0.5X. When the rotor system was cracked, the axial trajectory was a “vortex”, and the response spectrum was dominated by 0.5X. Thus, the study of typical failure mechanism and vibration characteristics of a turbocharger rotor system by simulation calculation is effective and has good research prospects, providing an important technical reference for dynamic analysis and fault diagnosis of the rotor system. Full article

(This article belongs to the Special Issue Rotor Dynamics and Rotating Machinery)

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21 pages, 14290 KiB

Open AccessEditor’s ChoiceArticle

Semi-Active Vibration Control of Seat Suspension Equipped with a Variable Equivalent Inertance-Variable Damping Device

by Guangrui Luan, Pengfei Liu, Donghong Ning, Guijie Liu and Haiping Du

Machines 2023, 11(2), 284; https://doi.org/10.3390/machines11020284 - 14 Feb 2023

Cited by 7 | Viewed by 2397

The seat suspension has a significant influence on riding comfort in many practical applications, such as heavy duty vehicles, military vehicles, and high-speed crafts. This paper proposes a seat suspension equipped with a variable equivalent inertance-variable damping (VEI–VD) device and a novel semi-active [...] Read more.

The seat suspension has a significant influence on riding comfort in many practical applications, such as heavy duty vehicles, military vehicles, and high-speed crafts. This paper proposes a seat suspension equipped with a variable equivalent inertance-variable damping (VEI–VD) device and a novel semi-active vibration control strategy. The VEI–VD device can control its equivalent inertance and damping by controlling two external resistors in its electric circuit. Especially, the VEI part of the device can store and release vibration energy via the inside flywheel, which enables the seat suspension to have a four-quadrant controllable capability in the available force–velocity diagram, similar to an active system. First, the dynamic model of the VEI–VD device is built, and a prototype is developed and tested to identify the model parameters and verify its characteristics. Then, a semi-active vibration control method is proposed for the VEI–VD seat suspension. The control method uses a sliding mode controller to acquire the desired control force for reducing vibration; then, according to the desired force and system states, the VEI–VD device is tuned by a force-tracking scheme to generate a real force. In the numerical validation, the vibration transmissibility of VEI–VD seat suspension around its natural frequency is tested with different states. The effectiveness of force-tracking control strategies for different types of suspensions is verified. In the random excitation test, the root means square acceleration of the VEI–VD seat is reduced by 30.72% compared with a passive seat. The VEI–VD seat suspension shows great potential in applications. Full article

(This article belongs to the Special Issue Low-Frequency Vibration Control with Advanced Technologies)

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19 pages, 6920 KiB

Open AccessEditor’s ChoiceArticle

Vision-Based Robotic Object Grasping—A Deep Reinforcement Learning Approach

by Ya-Ling Chen, Yan-Rou Cai and Ming-Yang Cheng

Machines 2023, 11(2), 275; https://doi.org/10.3390/machines11020275 - 12 Feb 2023

Cited by 11 | Viewed by 6473

This paper focuses on developing a robotic object grasping approach that possesses the ability of self-learning, is suitable for small-volume large variety production, and has a high success rate in object grasping/pick-and-place tasks. The proposed approach consists of a computer vision-based object detection [...] Read more.

This paper focuses on developing a robotic object grasping approach that possesses the ability of self-learning, is suitable for small-volume large variety production, and has a high success rate in object grasping/pick-and-place tasks. The proposed approach consists of a computer vision-based object detection algorithm and a deep reinforcement learning algorithm with self-learning capability. In particular, the You Only Look Once (YOLO) algorithm is employed to detect and classify all objects of interest within the field of view of a camera. Based on the detection/localization and classification results provided by YOLO, the Soft Actor-Critic deep reinforcement learning algorithm is employed to provide a desired grasp pose for the robot manipulator (i.e., learning agent) to perform object grasping. In order to speed up the training process and reduce the cost of training data collection, this paper employs the Sim-to-Real technique so as to reduce the likelihood of damaging the robot manipulator due to improper actions during the training process. The V-REP platform is used to construct a simulation environment for training the deep reinforcement learning neural network. Several experiments have been conducted and experimental results indicate that the 6-DOF industrial manipulator successfully performs object grasping with the proposed approach, even for the case of previously unseen objects. Full article

(This article belongs to the Special Issue Recent Trends and Interdisciplinary Applications of AI & Robotics)

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15 pages, 8627 KiB

Open AccessEditor’s ChoiceArticle

Sizing of a Traction Switched Reluctance Motor for an Electric Refuse-Collecting Vehicle Application

by Alexander Forsyth, Francisco Juarez-Leon and Berker Bilgin

Machines 2023, 11(2), 274; https://doi.org/10.3390/machines11020274 - 11 Feb 2023

Cited by 1 | Viewed by 2171

Refuse-collecting vehicles are significant polluters due to their expected drive cycles involving frequent stops and long idle periods. Electric refuse-collecting vehicles, still in their infancy, promise to address this through the replacement of internal combustion engines with batteries and electric traction motors. Today, [...] Read more.

Refuse-collecting vehicles are significant polluters due to their expected drive cycles involving frequent stops and long idle periods. Electric refuse-collecting vehicles, still in their infancy, promise to address this through the replacement of internal combustion engines with batteries and electric traction motors. Today, typical motors for these vehicles involve heavy use of rare earth permanent magnets, which are subject to high price volatility, environmentally damaging mining practices, and occupational health hazards associated with refinement. The switched reluctance motor, which makes use of no permanent magnets, is a suitable substitute. This type of motor technology offers several advantages such as simple and robust construction, the ability to operate at high speeds and high temperature conditions, fault tolerance capability, and lower production costs in comparison with other technologies. This paper focuses on the design process of a switched reluctance motor for a battery electric refuse-collecting vehicle. The designed motor has a 36/24 outer rotor configuration, and its electrical and mechanical characteristics are based on the commercial traction motor TM4 SUMO HD HV3500-9P. The performance of the motor is evaluated using simulation tools such as JMAG and MATLAB/Simulink. Full article

(This article belongs to the Section Electrical Machines and Drives)

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21 pages, 5642 KiB

Open AccessEditor’s ChoiceArticle

Design of a High-Gap Plant Protection Machine (HGPM) with Stepless Variable Speed and Power Adjustable Function

by Zengbin Cai, Dongbo Xie, Tao Liu, Peiyu Hu, Hongji Liu and Quan Zheng

Machines 2023, 11(2), 265; https://doi.org/10.3390/machines11020265 - 10 Feb 2023

Viewed by 1686

The passing performance and driving stability performance of HGPM in an unstructured environment will directly affect the quality of HGPM operation. This paper designs an HGPM power chassis transmission system in order to address the problem of poor adaptability of existing plant protection [...] Read more.

The passing performance and driving stability performance of HGPM in an unstructured environment will directly affect the quality of HGPM operation. This paper designs an HGPM power chassis transmission system in order to address the problem of poor adaptability of existing plant protection machines to complex working conditions in the field, especially in the middle and late stage of plant protection operation of tall crops, which cannot pass smoothly due to the obstruction of vision and special road conditions resulting in insufficient traction of the whole machine. The system is theoretically analyzed based on hydrostatic transmission and a time-sharing four-wheel drive splitter; then, based on Solidworks and RecurDyn software, the HGPM is modeled in three dimensions, and the dynamic simulation of working conditions such as climbing, crossing the ridge, and opening the road during field operation is carried out. The simulation results show that the 2H mode can climb over a slope with an angle in the range of 0−25° and a ridge with height in the range of 0−100 mm, the 4H mode can climb over a slope with an angle in the range of 0−35° and a ridge with height in the range of 0−320 mm, with relatively stable body speed and the wheel rotation angular speed converging faster under the open road condition. Finally, prototype performance tests were conducted. The test results show that 4H mode can smoothly pass the ridge with a ridge height of 320 mm and a slope of 26°, while 2H mode has a sharp drop in speed to 0 after a short fluctuation. 4H mode achieves a more rapid convergence of longitudinal wheel stability compared to 2H mode. The developed chassis drive system of a new type of HGPM meets the design requirements and provides a reference for the dynamic chassis design of HGPM. Full article

(This article belongs to the Section Machine Design and Theory)

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25 pages, 7703 KiB

Open AccessEditor’s ChoiceArticle

Hard Milling Process Based on Compressed Cold Air-Cooling Using Vortex Tube for Sustainable and Smart Manufacturing

by Luka Celent, Dražen Bajić, Sonja Jozić and Marko Mladineo

Machines 2023, 11(2), 264; https://doi.org/10.3390/machines11020264 - 10 Feb 2023

Cited by 5 | Viewed by 2035

Improving machining performance and meeting the requirements of sustainable production at the same time represents a major challenge for the metalworking industry and scientific community. One approach to satisfying the above challenge is to apply different types of cutting fluids or to optimise [...] Read more.

Improving machining performance and meeting the requirements of sustainable production at the same time represents a major challenge for the metalworking industry and scientific community. One approach to satisfying the above challenge is to apply different types of cutting fluids or to optimise their usage during the machining process. The fact that cutting fluids are well known as significant environmental pollutants in the metalworking industry has encouraged researchers to discover new environmentally friendly ways of cooling and lubricating in the machining process. Therefore, the main goal is to investigate the influence of different machining conditions on the efficiency of hard machining and find a sustainable solution towards smart manufacturing. In the experimental part of the work, the influence of various machining parameters and conditions on the efficiency of the process was investigated and measured through the surface roughness, tool wear and cutting force components. Statistical data processing was carried out, and predictive mathematical models were developed. An important achievement is the knowledge of the efficiency of compressed cold air cooling for hard milling with the resulting lowest average flank wear of 0.05 mm, average surface roughness of 0.28 µm, which corresponds to grinding procedure roughness classes of N4 and N5, and average tool durability increase of 26% compared to dry cutting and conventional use of cutting fluids. Becoming a smart machining system was assured via technological improvement achieved through the reliable prediction of tool wear obtained by radial basis neural networks modelling, with a relative prediction error of 3.97%. Full article

(This article belongs to the Special Issue Advances in Smart Manufacturing and Industry 4.0)

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29 pages, 7778 KiB

Open AccessEditor’s ChoiceArticle

Robot Navigation in Crowded Environments: A Reinforcement Learning Approach

by Matteo Caruso, Enrico Regolin, Federico Julian Camerota Verdù, Stefano Alberto Russo, Luca Bortolussi and Stefano Seriani

Machines 2023, 11(2), 268; https://doi.org/10.3390/machines11020268 - 10 Feb 2023

Viewed by 2698

For a mobile robot, navigation in a densely crowded space can be a challenging and sometimes impossible task, especially with traditional techniques. In this paper, we present a framework to train neural controllers for differential drive mobile robots that must safely navigate a [...] Read more.

For a mobile robot, navigation in a densely crowded space can be a challenging and sometimes impossible task, especially with traditional techniques. In this paper, we present a framework to train neural controllers for differential drive mobile robots that must safely navigate a crowded environment while trying to reach a target location. To learn the robot’s policy, we train a convolutional neural network using two Reinforcement Learning algorithms, Deep Q-Networks (DQN) and Asynchronous Advantage Actor Critic (A3C) and develop a training pipeline that allows to scale the process to several compute nodes. We show that the asynchronous training procedure in A3C can be leveraged to quickly train neural controllers and test them on a real robot in a crowded environment. Full article

(This article belongs to the Section Robotics, Mechatronics and Intelligent Machines)

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19 pages, 8580 KiB

Open AccessEditor’s ChoiceArticle

Dynamics Modeling and Redundant Force Optimization of Modular Combination Parallel Manipulator

by Aimin Jiang, Hasiaoqier Han, Chunyang Han, Shuai He, Zhenbang Xu and Qingwen Wu

Machines 2023, 11(2), 247; https://doi.org/10.3390/machines11020247 - 7 Feb 2023

Cited by 2 | Viewed by 1283

The limb-driving force mutation of the modular combination parallel manipulator (MCPM) affects the alignment process of optical axis. In this paper, a novel optimization method based on the force mutation penalty term is proposed to solve the problem of driving force mutation. The [...] Read more.

The limb-driving force mutation of the modular combination parallel manipulator (MCPM) affects the alignment process of optical axis. In this paper, a novel optimization method based on the force mutation penalty term is proposed to solve the problem of driving force mutation. The kinematics and dynamics models of the manipulator are established using a modularization idea, reducing the complexity of the modeling process, and verified using co-simulation. Moreover, particle swarm optimization (PSO) is applied as an optimization tool. The effectiveness of the proposed method is confirmed by comparing it with the minimize-the-maximum and Moore–Penrose (M–P) methods, which are widely used to solve parallel manipulators with redundant drives. Full article

(This article belongs to the Section Machine Design and Theory)

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30 pages, 56743 KiB

Open AccessEditor’s ChoiceArticle

Fault Diagnosis of Rotating Machinery Based on Two-Stage Compressed Sensing

by Xianglong You, Jiacheng Li, Zhongwei Deng, Kai Zhang and Hang Yuan

Machines 2023, 11(2), 242; https://doi.org/10.3390/machines11020242 - 6 Feb 2023

Cited by 5 | Viewed by 1922

Intelligent on-site fault diagnosis and professional vibration analysis are essential for the safety and stability of rotating machinery operation. This paper represents a fault diagnosis scheme based on two-stage compressed sensing for triaxial vibration data, which realizes fault diagnosis for rotating machinery based [...] Read more.

Intelligent on-site fault diagnosis and professional vibration analysis are essential for the safety and stability of rotating machinery operation. This paper represents a fault diagnosis scheme based on two-stage compressed sensing for triaxial vibration data, which realizes fault diagnosis for rotating machinery based on compressed data and data reconstruction for professional vibration analysis. In the 1st stage, the triaxial vibration signals are compressed using a pre-designed hybrid measurement matrix; these compressed data can be used both for time-frequency transform and for vibration data reconstruction. In the 2nd stage, the frequency spectra of the triaxial vibration signals are fused and further compressed using another pre-designed joint measurement matrix, which inhibits the high-frequency noises simultaneously. Finally, the fused spectra are employed as feature vectors in sparse-representation-based classification, where the proposed batch matching pursuit (BMP) algorithm is utilized to calculate the sparse vectors. The two-stage compression scheme and the BMP algorithm minimize the computational cost of on-site fault diagnosis, which is suitable for edge computing platforms. Meanwhile, the compressed vibration data can be reconstructed, which provides evidence for professional vibration analysis. The method proposed in this study is validated by two practical case studies, in which the accuracies are 99.73% and 96.70%, respectively. Full article

(This article belongs to the Special Issue Fault Detection, Diagnosis and Prognostics of Machines: Applications and Advances)

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15 pages, 6973 KiB

Open AccessEditor’s ChoiceArticle

Shock Absorption for Legged Locomotion through Magnetorheological Leg-Stiffness Control

by Matthew Daniel Christie, Shuaishuai Sun, Lei Deng, Haiping Du, Shiwu Zhang and Weihua Li

Machines 2023, 11(2), 236; https://doi.org/10.3390/machines11020236 - 6 Feb 2023

Cited by 3 | Viewed by 1688

The objective of this study was to evaluate the performance of a magnetorheological-fluid-based variable stiffness actuator leg under high impact forces through optimal tuning and control of stiffness and damping properties. To achieve this, drop testing experiments were conducted with the leg at [...] Read more.

The objective of this study was to evaluate the performance of a magnetorheological-fluid-based variable stiffness actuator leg under high impact forces through optimal tuning and control of stiffness and damping properties. To achieve this, drop testing experiments were conducted with the leg at various drop heights and payload masses. The results showed that while lower stiffness and higher damping can lead to lower impact forces and greater energy dissipation, respectively, optimal control can also protect the leg from deflecting beyond its functional range. Comparison with a rigid leg with higher damping showed a 57.5% reduction in impact force, while a more compliant leg with lower damping results in a 61.4% reduction. These findings demonstrate the importance of considering both stiffness and damping in the design of legged robots for high impact force resistance. This simultaneously highlights the efficacy of the proposed magnetorheological-fluid-based leg design for this purpose. Full article

(This article belongs to the Special Issue Low-Frequency Vibration Control with Advanced Technologies)

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25 pages, 2415 KiB

Open AccessEditor’s ChoiceArticle

Dynamic Launch Trajectory Planning of a Cable-Suspended Translational Parallel Robot Using Point-to-Point Motions

by Deng Lin and Giovanni Mottola

Machines 2023, 11(2), 224; https://doi.org/10.3390/machines11020224 - 3 Feb 2023

Cited by 3 | Viewed by 1460

In the last decade, cable-suspended parallel robots have attracted significant interest due to their large workspaces and high dynamic performances. However, a significant drawback is that cables must always be in tension to control the motion. Using launch motions to reach a target [...] Read more.

In the last decade, cable-suspended parallel robots have attracted significant interest due to their large workspaces and high dynamic performances. However, a significant drawback is that cables must always be in tension to control the motion. Using launch motions to reach a target can enlarge the workspace of such robots. For a spatial translational cable robot suspended by six pairwise-parallel cables, an analytical method for planning point-to-point dynamic trajectories is proposed. Using a second-order Bézier curve trajectory, the mechanism starts from a static condition, passes through intermediate points, and finally launches an object towards a target. According to the kinematic constraint conditions on the position, the velocity and acceleration of the end-effector at a prescribed point, the parametric expressions for a dynamically-feasible trajectory can be determined. The feasibility of the trajectory is analyzed under the constraint that cable tensions must be positive at all times. By changing the position of the end point of the trajectory and the total motion time, the kinematic conditions on the position and velocity as well as the feasibility constraint can be satisfied. Finally, our point-to-point dynamic launch trajectories are verified by simulations and experiments. Full article

(This article belongs to the Section Machine Design and Theory)

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16 pages, 10453 KiB

Open AccessEditor’s ChoiceArticle

Experimental Study on Tribological and Leakage Characteristics of a Rotating Spring-Energized Seal under High and Low Temperature

by Dengyu Liu, Jun Zhao, Shuangxi Li, Xinni Zhao and Lele Huang

Machines 2023, 11(2), 221; https://doi.org/10.3390/machines11020221 - 3 Feb 2023

Cited by 3 | Viewed by 2125

A spring-energized seal, whose PTFE plastic shell has excellent self-lubrication and a low temperature stability, is used widely in liquid fuel valves’ rotating end-face seals. However, in practical application, temperature has a larger effect on not only the physical and tribological properties of [...] Read more.

A spring-energized seal, whose PTFE plastic shell has excellent self-lubrication and a low temperature stability, is used widely in liquid fuel valves’ rotating end-face seals. However, in practical application, temperature has a larger effect on not only the physical and tribological properties of materials, but also on the leakage performance of spring-energized rings. Thus, a high and low temperature sealing test of the spring-energized seal that applies to an engine was carried out. In this paper, the leakage characteristics, friction torque and wear characteristics of a spring-energized ring under different temperatures were studied. The friction torque at high temperature was less than that at normal temperature, and a low temperature could effectively reduce the wear amount of PTFE material. In order to study the influence of temperature on PTFE filled with graphite, the friction and wear test of PTFE-2 was carried out. The results showed that the amount of wear of PTFE-2 was only 27.8% of that at the normal temperature but the friction coefficient was three times larger when the temperature was −45 °C. Full article

(This article belongs to the Special Issue Selected Papers from CITC2022)

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21 pages, 9307 KiB

Open AccessEditor’s ChoiceArticle

Flow Regulation of Low Head Hydraulic Propeller Turbines by Means of Variable Rotational Speed: Aerodynamic Motivations

by Dario Barsi, Robert Fink, Peter Odry, Marina Ubaldi and Pietro Zunino

Machines 2023, 11(2), 202; https://doi.org/10.3390/machines11020202 - 1 Feb 2023

Cited by 3 | Viewed by 2268

To date, hydraulic energy is still, among the renewable ones, the most widespread and most exploited to produce electricity. With the current trend to exploit any renewable source available, the limits for the economic convenience of hydroelectric power plants have significantly changed, making [...] Read more.

To date, hydraulic energy is still, among the renewable ones, the most widespread and most exploited to produce electricity. With the current trend to exploit any renewable source available, the limits for the economic convenience of hydroelectric power plants have significantly changed, making it interesting and convenient to use even small heads and low flow rates. In the specific applications of hydraulic turbines operating with low heads, the Kaplan turbine plays the predominant role among the available machines, also given the possibility of carrying out an “on cam” regulation, acting simultaneously on the geometry of the rotor and distributor rows, thus allowing a wide flow rate adjustment range. However, for applications characterized by very low heads and low available powers, it may not be convenient to use complex regulating devices. For this reason, these plants usually use axial machines characterized by a partial regulation (of the distributor or of the rotor), significantly reducing the operating range of the machine compared to the case of double regulation. In the last decade, the development of reliable and less expensive permanent magnet generators and power electronic converters and related new control strategies has paved the way for the concept of regulating hydraulic turbines by means of variable rotational speed. This regulation principle is based on the possibility of acting in the case of using synchronous permanent magnets electric generators and electronic power converters and on the variation of the rotational speed of the machine while keeping the grid frequency constant. The concept can be applied both to pure propellers with fixed a rotor and fixed distributor and to hydraulic axial turbines with regulation based on the modification of the variable guide vane opening angle. Although this new regulation approach, even in the case of the combined guide vane and rotational speed regulation, does not allow to recover most of the energy losses due to the variation of the operating conditions as effectively as the Kaplan double regulation does, the variation of the rotation speed, coupled with the variation of the opening of the distributor row, allows to reduce the tangential kinetic energy losses generated at the turbine exit during the off-design operations of a fixed blade opening angle rotor. At the same time, this type of regulation offers a simple and thus low-cost solution. The present study develops the theory underlying this regulation concept, based on the use of the turbomachinery fundamental equations, and reports the results of the off-design CFD analysis carried out for different combinations of rotation speeds and openings of the distributor, showing the improvement of the hydraulic efficiency over a large range of operating conditions with respect to the single regulation approach. Full article

(This article belongs to the Special Issue 10th Anniversary of Machines—Feature Papers in Turbomachinery)

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19 pages, 2959 KiB

Open AccessEditor’s ChoiceArticle

Smartphone-Based Indoor Floor Plan Construction via Acoustic Ranging and Inertial Tracking

by Chuize Meng, Shan Jiang, Mengning Wu, Xuan Xiao, Dan Tao and Ruipeng Gao

Machines 2023, 11(2), 205; https://doi.org/10.3390/machines11020205 - 1 Feb 2023

Viewed by 1458

The lack of indoor floor plans is one of the major obstacles to ubiquitous indoor location-based services. Dedicated mobile robots with high-precision sensors can measure and produce accurate indoor maps, but the deployment remains low for the public. Computer vision techniques are adopted [...] Read more.

The lack of indoor floor plans is one of the major obstacles to ubiquitous indoor location-based services. Dedicated mobile robots with high-precision sensors can measure and produce accurate indoor maps, but the deployment remains low for the public. Computer vision techniques are adopted by some existing smartphone-based methods to build the 3D point cloud, which have the cost of a quantity of the efforts of image collection and the risk of privacy issues. In this paper, we propose BatMapper-Plus which adopt acoustic ranging and inertial tracking to construct precise and complete indoor floor plans on smartphones. It emits acoustic signals to measure the distance from the smartphone to a neighbouring wall segment, and produces accessible areas by surrounding the building during walking. It also refines the constructed indoor floor plan to eliminate scattered segments, and identifies connection areas, including stairs and elevators among different floors. In addition, we propose an LSTM-based dead-reckoning model which is trained by outdoor IMU readings and GPS records, and use it to infer the step length during indoor walking, thereby improving the floor plan quality. We also elaborate how to use the constructed map for indoor navigation, i.e., a Dynamic Time Warping algorithm which automatically matches current inertial readings and historical sensory data during map construction to produce fine-grained walking guidance. To show our effectiveness compared with the state-of-the-art, we carry out extensive experiments in a teaching building and a residential building. It proves that our method is efficient without any privacy concerns and texture/illumination limitations. Full article

(This article belongs to the Section Robotics, Mechatronics and Intelligent Machines)

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22 pages, 7191 KiB

Open AccessEditor’s ChoiceArticle

A Refined Dynamic Model for the Planetary Gear Set Considering the Time-Varying Nonlinear Support Stiffness of Ball Bearing

by Xiaodong Yang, Chaodong Zhang, Wennian Yu, Wenbin Huang, Zhiliang Xu and Chunhui Nie

Machines 2023, 11(2), 206; https://doi.org/10.3390/machines11020206 - 1 Feb 2023

Cited by 3 | Viewed by 1908

Dynamics models of planetary gear sets (PGSs) are usually established to predict their dynamic behavior and load-sharing characteristics. The accurate modeling of bearing support stiffness is essential to study their dynamics. However, in most of the existing PGS dynamic models, the effect of [...] Read more.

Dynamics models of planetary gear sets (PGSs) are usually established to predict their dynamic behavior and load-sharing characteristics. The accurate modeling of bearing support stiffness is essential to study their dynamics. However, in most of the existing PGS dynamic models, the effect of characteristics coupling the rolling bearing time-varying nonlinear stiffness with the translational property of PGSs on the dynamic responses was completely neglected. To investigate this problem, a refined dynamic model for PGSs is proposed considering the coupled relationship between the radial translation of the rotating components and the time-varying nonlinear support stiffness of the ball bearing. The refined dynamic model simultaneously considers the coupled effect of the time-varying characteristic caused by the orbital motion of the rolling elements and the nonlinear characteristic caused by Hertzian contact between the rolling elements and raceways of the ball bearing. Comparisons between the simulations and experimental results are presented, which indicate that the PGS vibration spectrums yielded by the proposed time-varying nonlinear stiffness model are much closer to the actual scenarios than those of traditional models. The analysis results provide theoretical guidance for fault monitoring and diagnosis of the rolling bearings used in the PGS. Full article

(This article belongs to the Special Issue Safety of Machinery: Design, Monitoring, Manufacturing)

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22 pages, 5061 KiB

Open AccessEditor’s ChoiceArticle

Integrated Adhesion Coefficient Estimation of 3D Road Surfaces Based on Dimensionless Data-Driven Tire Model

by Zhiwei Xu, Yongjie Lu, Na Chen and Yinfeng Han

Machines 2023, 11(2), 189; https://doi.org/10.3390/machines11020189 - 31 Jan 2023

Cited by 4 | Viewed by 2087

The tire/road peak friction coefficient (TRPFC) is the core parameter of vehicle stability control, and its estimation accuracy significantly affects the control effect of active vehicle safety. To estimate the peak adhesion coefficient accurately, a new method for the comprehensive adhesion coefficient of [...] Read more.

The tire/road peak friction coefficient (TRPFC) is the core parameter of vehicle stability control, and its estimation accuracy significantly affects the control effect of active vehicle safety. To estimate the peak adhesion coefficient accurately, a new method for the comprehensive adhesion coefficient of three-dimensional pavement based on a dimensionless data-driven tire model is proposed. Firstly, in order to accurately describe the contact state between the three-dimensional road surface and the tire during driving, stress distribution and multi-point contact are introduced into the vertical dynamic model and a new tire model driven by dimensionless data is established based on the normalization method. Secondly, the real-time assessment of lateral and longitudinal adhesion coefficients of three-dimensional pavement is realized with the unscented Kalman filter (UKF). Finally, according to the coupling relationship between the longitudinal tire adhesion coefficient and the lateral tire adhesion coefficient, a fuzzy reasoning strategy of fusing the longitudinal tire adhesion coefficient and the lateral tire adhesion coefficient is designed. The results of vehicle tests prove that the method proposed in this paper can estimate the peak adhesion coefficient of pavement quickly and accurately. Full article

(This article belongs to the Special Issue Advanced Modeling, Analysis and Control for Electrified Vehicles)

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15 pages, 10318 KiB

Open AccessEditor’s ChoiceArticle

Rejection of Synchronous Vibrations of AMB System Using Nonlinear Adaptive Control Algorithm with a Novel Frequency Estimator

by Xiaoyu Bian, Zhengang Shi, Ni Mo, Lei Shi, Yangbo Zheng and Xingnan Liu

Machines 2023, 11(2), 188; https://doi.org/10.3390/machines11020188 - 31 Jan 2023

Cited by 3 | Viewed by 1409

This paper focuses on the synchronous vibration suppression of an active magnetic bearing (AMB) system without a rotating speed sensor. One of the most intractable problems with AMB systems is the synchronous vibration caused by the mass imbalance of the rotor. Moreover, practically [...] Read more.

This paper focuses on the synchronous vibration suppression of an active magnetic bearing (AMB) system without a rotating speed sensor. One of the most intractable problems with AMB systems is the synchronous vibration caused by the mass imbalance of the rotor. Moreover, practically all existing unbalance control algorithms require the rotating speed sensor to determine rotation speed. However, in some unique applications, it is impossible to install and use the rotating speed sensor as intended. This study provided a nonlinear adaptive control (NAC) algorithm and a modified frequency estimator to address the above issues. The proposed approach can suppress current and displacement vibrations by regulating the control structure. The frequency estimator calculates the rotating speed based on the position of the rotor at different moments, which has a quick response time, high precision, and effective tracking. The NAC algorithm can achieve unbalanced control based on the period iteration strategy. Additionally, the Lyapunov method is used to demonstrate the stability of the NAC algorithm. Finally, the experimental and simulation results also confirm the effectiveness and reliability of the overall control scheme. The results from simulations and experiments indicate that the novel frequency estimator can track the speed accurately and that its error can be regulated to within

\pm

0.05 Hz. The overall control schema can reduce the displacement vibration’s amplitude by 72.2% and the current vibration’s amplitude by 65.6%. Full article

(This article belongs to the Special Issue Selected Papers from CITC2022)

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20 pages, 9995 KiB

Open AccessEditor’s ChoiceArticle

Sound-Based Intelligent Detection of FOD in the Final Assembly of Rocket Tanks

by Tantao Lin, Yongsheng Zhu, Zhijun Ren, Kai Huang, Xinzhuo Zhang, Ke Yan and Shunzhou Huang

Machines 2023, 11(2), 187; https://doi.org/10.3390/machines11020187 - 31 Jan 2023

Cited by 2 | Viewed by 1810

The traditional method of relying on human hearing to detect foreign object debris (FOD) events during rocket tank assembly processes has the limitation of strong reliance on humans and difficulty in establishing objective detection records. This can lead to undetected FOD entering the [...] Read more.

The traditional method of relying on human hearing to detect foreign object debris (FOD) events during rocket tank assembly processes has the limitation of strong reliance on humans and difficulty in establishing objective detection records. This can lead to undetected FOD entering the engine with the fuel and causing major launch accidents. In this study, we developed an automatic, intelligent FOD detection system for rocket tanks based on sound signals to overcome the drawbacks of manual detection, enabling us to take action to prevent accidents in advance. First, we used log-Mel transformation to reduce the high sampling rate of the sound signal. Furthermore, we proposed a multiscale convolution and temporal convolutional network (MS-CTCN) to overcome the challenges of multi-scale temporal feature extraction to detect suspicious FOD events. Finally, we used the proposed post-processing strategies of label smoothing and threshold discrimination to refine the results of FOD event detection and ultimately determine the presence of FOD. The proposed method was validated through FOD experiments. The results showed that the method had an accuracy rate of 99.16% in detecting FOD and had a better potential to prevent accidents compared to the baseline method. Full article

(This article belongs to the Special Issue Intelligent Maintenance and Health Management of Electromechanical Equipment)

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22 pages, 27826 KiB

Open AccessEditor’s ChoiceArticle

The Water-Powered Trip Hammer and Forge La Pianca as a Case Study of a Piedmont (Italy) Water Mill

by Walter Franco, Roberto Olivero, Gianpiero Cavallo and Davide Colletti

Machines 2023, 11(2), 180; https://doi.org/10.3390/machines11020180 - 28 Jan 2023

Cited by 1 | Viewed by 3310

For hundreds of years, water mills have supported the local economies of Piedmont by contributing to the production of flour, textile fibres, timber, and metal agricultural tools. Since the beginning of the last century, and in particular after the 1950s, many artefacts have [...] Read more.

For hundreds of years, water mills have supported the local economies of Piedmont by contributing to the production of flour, textile fibres, timber, and metal agricultural tools. Since the beginning of the last century, and in particular after the 1950s, many artefacts have been abandoned. Nonetheless, hundreds of mills are still present in southern Piedmont, both in the plains and in the mountains, sometimes in an excellent state of conservation. This work presents a hammer forge, the La Pianca mill in Busca, Cuneo, Italy, as a significant, detailed case study. The socio-economic context in which exists is analysed, its history is reconstructed, and the functioning of the machinery, including the water wheels, the motion transmission systems, and the various utilities consisting of tilt hammers, grinding wheels, and drills, is analysed in detail. Beyond the historical interest, concerning both the territory and the architecture, as well as the machines and mechanisms, this work aims to make a contribution to the prefiguration of effective scenarios for the reconversion of similar productive artefacts. Full article

(This article belongs to the Section Machine Design and Theory)

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30 pages, 3392 KiB

Open AccessEditor’s ChoiceArticle

Explainable Data-Driven Method Combined with Bayesian Filtering for Remaining Useful Lifetime Prediction of Aircraft Engines Using NASA CMAPSS Datasets

by Faisal Maulana, Andrew Starr and Agusmian Partogi Ompusunggu

Machines 2023, 11(2), 163; https://doi.org/10.3390/machines11020163 - 24 Jan 2023

Cited by 5 | Viewed by 3580

An aircraft engine is expected to have a high-reliability system as a safety-critical asset. A scheduled maintenance strategy based on statistical calculation has been employed as the current practice to achieve the reliability requirement. Any improvement to this maintenance interval is made after [...] Read more.

An aircraft engine is expected to have a high-reliability system as a safety-critical asset. A scheduled maintenance strategy based on statistical calculation has been employed as the current practice to achieve the reliability requirement. Any improvement to this maintenance interval is made after significant reliability issues arise (such as flight delays and high component removals). Several publications and research studies have been conducted related to this issue, one of them involves performing simulations and providing aircraft operation datasets. The recently published NASA CMAPPS datasets have been utilised in this paper since they simulate flight data recording from various measurements. A prognostics model can be developed by analysing these datasets and predicting the engine’s reliability before failure. However, the state-of-the-art prognostics techniques published in the literature using these NASA CMAPPS datasets are mainly purely data-driven. These techniques mainly deal with a “black box” process which does not include uncertainty quantification (UQ). These two factors are barriers to prognostics applications, particularly in the aviation industry. To tackle these issues, this paper aims at developing explainable and transparent algorithms and a software tool to compute the engine health, estimate engine end of life (EoL), and eventually predict its remaining useful life (RUL). The proposed algorithms use hybrid metrics for feature selection, employ logistic regression for health index estimation, and unscented Kalman filter (UKF) to update the prognostics model for predicting the RUL in a recursive fashion. Among the available datasets, dataset 02 is chosen because it has been widely used and is an ideal candidate for result comparison and dataset 03 is employed as a new state-of-the-art. As a result, the proposed algorithms yield 34.5–55.6% better performance in terms of the root mean squared error (RMSE) compared with the previous work. More importantly, the proposed method is transparent and it quantifies the uncertainty during the prediction process. Full article

(This article belongs to the Special Issue Fault Detection, Diagnosis and Prognostics of Machines: Applications and Advances)

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18 pages, 7729 KiB

Open AccessEditor’s ChoiceArticle

Numerical and Experimental Investigations of Axial Flow Fan with Bionic Forked Trailing Edge

by Zhong Liang, Jun Wang, Wei Wang, Boyan Jiang, Yanyan Ding and Wanxiang Qin

Machines 2023, 11(2), 155; https://doi.org/10.3390/machines11020155 - 23 Jan 2023

Cited by 3 | Viewed by 3148

To improve the performance of the aerodynamic properties and reduce the aerodynamic noise of an axial flow fan in the outdoor unit of an air conditioner, this study proposed a bionic forked trailing-edge structure inspired by the forked fish caudal fin and implemented [...] Read more.

To improve the performance of the aerodynamic properties and reduce the aerodynamic noise of an axial flow fan in the outdoor unit of an air conditioner, this study proposed a bionic forked trailing-edge structure inspired by the forked fish caudal fin and implemented by modifying the trailing edge of the prototype fan. The effect of the bionic forked trailing edge on the aerodynamic and aeroacoustic performance was investigated experimentally, and detailed analyses of the blade load and internal vortex structures were performed based on large-eddy simulations (LES). It is shown that the bionic forked trailing edge could effectively adjust the blade load distribution, reduce the pressure difference between the pressure side and suction side near the trailing edge of the blade tip region, and weaken the intensity and influence range of the inlet vortex (IV) and the tip leakage vortex (TLV). The discrete noise caused by the vortices in the rotor tip area was also reduced, particularly at the blade passing frequency (BPF) and its harmonic frequency. The experimental results confirmed the existence of an optimal bionic forked trailing-edge structure, resulting in the maximum power-saving rate γ of 7.5% and the reduction of 0.3 ~ 0.8 dB of aerodynamic noise, with an included angle θ_t of 13.5°. The detailed analysis of the internal vortex structures provides a good reference for the efficiency improvement and noise reduction of axial flow fans. Full article

(This article belongs to the Special Issue Selected Papers from CITC2022)

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19 pages, 3675 KiB

Open AccessEditor’s ChoiceArticle

A Novel Method of Digital Twin-Based Manufacturing Process State Modeling and Incremental Anomaly Detection

by Qinglei Zhang, Zhen Liu, Jianguo Duan and Jiyun Qin

Machines 2023, 11(2), 151; https://doi.org/10.3390/machines11020151 - 22 Jan 2023

Cited by 5 | Viewed by 2245

In the manufacturing process, digital twin technology can provide real-time mapping, prediction, and optimization of the physical manufacturing process in the information world. In order to realize the complete expression and accurate identification of and changes in the real-time state of the manufacturing [...] Read more.

In the manufacturing process, digital twin technology can provide real-time mapping, prediction, and optimization of the physical manufacturing process in the information world. In order to realize the complete expression and accurate identification of and changes in the real-time state of the manufacturing process, a digital twin framework of incremental learning driven by stream data is proposed. Additionally, a novel method of stream data-driven equipment operation state modeling and incremental anomaly detection is proposed based on the digital twin. Firstly, a hierarchical finite state machine (HFSM) for the manufacturing process was proposed to completely express the manufacturing process state. Secondly, the incremental learning detection method driven by stream data was used to detect the anomaly of the job process data, so as to change the job status in real time. Furthermore, the F1 value and time consumption of the proposed algorithm were compared and analyzed using a general dataset. Finally, the method was applied to the practical case development of a welding manufacturer’s digital twin system. The flexibility of the proposed model is calculated by the quantitative method. The results show that the proposed state modeling and anomaly detection method can help the system realize job state mapping and state change quickly, effectively, and flexibly. Full article

(This article belongs to the Special Issue Digital Twin Applications in Smart Manufacturing)

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15 pages, 3331 KiB

Open AccessEditor’s ChoiceArticle

A Method of Improving the Length Measurement Accuracy of Metal Parts Using Polarization Vision

by Zhiying Tan, Yan Ji, Wenbo Fan, Weifeng Kong, Xu Tao, Xiaobin Xu and Minzhou Luo

Machines 2023, 11(2), 145; https://doi.org/10.3390/machines11020145 - 20 Jan 2023

Viewed by 1633

Measurement technology based on machine vision has been widely used in various industries. The development of vision measurement technology mainly depends on the process of photosensitive components and the algorithm of processing a target image. In the high-precision dimension measurement of machined metal [...] Read more.

Measurement technology based on machine vision has been widely used in various industries. The development of vision measurement technology mainly depends on the process of photosensitive components and the algorithm of processing a target image. In the high-precision dimension measurement of machined metal parts, the high-resolution imaging device usually exposes the cutting texture of the metal surface and affects the accuracy of measurement algorithm. At the same time, the edges of machined metal parts are often chamfered, which makes the edges of objects in the picture overexposed in the lighting measurement environment. These factors reduce the accuracy of dimensioning metal parts using visual measurements. The traditional vision measurement method based on color/gray image makes it difficult to analyze the physical quantities in the light field except for the light intensity, which limits the measurement accuracy. Polarization information can more carefully depict the edge contour edge information in the scene and increase the contrast between the foreground and the background. This paper presents a method to improve the measurement accuracy of machined metal parts by using polarization vision. The incident angle of the light source is optimized according to the complex refractive index of the metal material, and the degree of polarization image with enhanced edge contour features of the ROI (region of interest) is obtained. The high-precision measurement of cylindrical brass motor components is realized by using the method of reprojection transformation correction and maximum correlation template matching (NCC) for rough positioning, as well as the method of edge extraction and optimal fitting. The experimental results show that for copper parts with a tolerance range of

\pm 0.1

mm, the average measurement error and maximum measurement error are within

0.01

mm, which are higher than the existing color/gray image measurement methods. Full article

(This article belongs to the Section Machines Testing and Maintenance)

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16 pages, 6667 KiB

Open AccessEditor’s ChoiceArticle

Simulation and Field Studies on an Innovative Downhole Machine Designed for Ultrashort-Radius Horizontal Well Drilling Engineering

by Chenglong Li, Zongtao Chen, Zenglin Wang, Qizhong Tian, Rongdong Dai and Kun Wang

Machines 2023, 11(2), 139; https://doi.org/10.3390/machines11020139 - 19 Jan 2023

Viewed by 1650

Ultrashort-Radius Horizontal Well (URHW) drilling engineering plays an important role in increasing the recovery factor of old oilfields. By sidetracking old wellbores at a very high build-up rate, the URHW can effectively exploit the residual oil near old wellbores. Currently, the main problem [...] Read more.

Ultrashort-Radius Horizontal Well (URHW) drilling engineering plays an important role in increasing the recovery factor of old oilfields. By sidetracking old wellbores at a very high build-up rate, the URHW can effectively exploit the residual oil near old wellbores. Currently, the main problem faced in URHW drilling engineering is the reduced torque received by drill bits owing to the increased friction between the flexible drilling assembly and wellbore as the horizontal section extends, which greatly limits oil production from a single trip. To tackle this problem, we proposed an innovative machine design, a Dynamic Flexible Drill Rod (DFDR), to provide extra torque near the drill bit to extend the horizontal section of the URHW. The interior structure and working principle of the DFDR were illustrated. The mechanical properties of the DFDRs critical load-bearing part were examined via simulation. The torque and pressure loss characteristics were analyzed using computational fluid dynamics. Corresponding modifications were made to optimize the design, with model machines produced accordingly. Field trials were carried out based on old wellbores in Chunliang District, Shengli Oilfield. The DFDR-based technique extended the URHWs horizontal section in this area by 13.38% on average. Full article

(This article belongs to the Special Issue Machine Science and Research in Jiangsu University: Celebrating the 60th Anniversary of the Research Center of Fluid Machinery Engineering and Technology)

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16 pages, 2059 KiB

Open AccessEditor’s ChoiceArticle

Fixed-Time Sliding Mode-Based Active Disturbance Rejection Tracking Control Method for Robot Manipulators

by Anh Tuan Vo, Thanh Nguyen Truong, Quang Dan Le and Hee-Jun Kang

Machines 2023, 11(2), 140; https://doi.org/10.3390/machines11020140 - 19 Jan 2023

Cited by 5 | Viewed by 1859

This work investigates the issue of a hybrid trajectory tracking control algorithm (HTCA) for robot manipulators (RMs) with uncertain dynamics and the effect of external disturbances. Following are some proposals for achieving the control target. Firstly, to achieve the active disturbance rejection, we [...] Read more.

This work investigates the issue of a hybrid trajectory tracking control algorithm (HTCA) for robot manipulators (RMs) with uncertain dynamics and the effect of external disturbances. Following are some proposals for achieving the control target. Firstly, to achieve the active disturbance rejection, we propose a uniform second-order sliding mode disturbance observer (USOSMDO) to obtain directly the lumped uncertainties without their prior upper-bound information. Secondly, a fixed-time singularity-free terminal sliding surface (FxSTSS) is proposed to obtain a fixed-time convergence of the tracking control error (TCE) without the singularity in the control input. Then, using information on the proposed USOSMDO, our HTCA is formed based on the FxSTSS and the fixed-time power rate reaching law (FxPRRL). The control proposal not only stabilizes with the global fixed-time convergence but also attains high tracking accuracy. In addition, the chattering problem also is handled almost completely. Finally, numerical simulations verify the effectiveness and advantages of applying the proposed HTCA to a FARA robot. Full article

(This article belongs to the Special Issue Motion Planning and Advanced Control for Robotics)

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18 pages, 7624 KiB

Open AccessEditor’s ChoiceArticle

Stator Faults Detection in Asymmetrical Six-Phase Induction Motor Drives with Single and Dual Isolated Neutral Point, Adopting a Model Predictive Controller

by Khaled Laadjal, João Serra and Antonio J. Marques Cardoso

Machines 2023, 11(2), 132; https://doi.org/10.3390/machines11020132 - 18 Jan 2023

Cited by 2 | Viewed by 2060

Multiphase drives have been presented as potential replacements for conventional three-phase machines, primarily because of their propensity to operate faultlessly. Due to the various stator phase arrangements, standard fault detection techniques are insufficiently applicable and cannot be used to diagnose faults in the [...] Read more.

Multiphase drives have been presented as potential replacements for conventional three-phase machines, primarily because of their propensity to operate faultlessly. Due to the various stator phase arrangements, standard fault detection techniques are insufficiently applicable and cannot be used to diagnose faults in the various configurations of multiphase machines in closed-loop applications. The current study proposes an effective online diagnostic technique based on the computing and tracking of a significant severity factor, which is defined as the ratio of the zero, negative, and positive voltage symmetrical components employing a short-time least-square Prony algorithm (STLSP). In this study, the asymmetrical six-phase induction motor (ASPIM) was controlled by a model predictive control (MPC) algorithm, an attractive control scheme for the regulation of multiphase electric drives, since it easily exploits their inherent advantages. This article addresses stator faults in ASPIMs. The effectiveness of the suggested strategy was confirmed experimentally for various operating conditions in both steady and transient states. Full article

(This article belongs to the Special Issue Condition Monitoring and Fault Diagnosis of Induction Motors)

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15 pages, 4327 KiB

Open AccessEditor’s ChoiceArticle

Unknown Slope-Oriented Research on Model Predictive Control for Quadruped Robot

by Zhitong Zhang, Honglei An, Xiaojian Wei and Hongxu Ma

Machines 2023, 11(2), 133; https://doi.org/10.3390/machines11020133 - 18 Jan 2023

Cited by 4 | Viewed by 1876

There are many undulating terrains in the wild environment. In order to realize the adaptive and stable walking of quadruped robots on unknown sloped terrain, a slope-adaptability model predictive control (SAMPC) algorithm is proposed in this work. In the absence of external vision [...] Read more.

There are many undulating terrains in the wild environment. In order to realize the adaptive and stable walking of quadruped robots on unknown sloped terrain, a slope-adaptability model predictive control (SAMPC) algorithm is proposed in this work. In the absence of external vision sensors, the orientation and inclination of the slope are estimated based on the joint position sensors and inertial measurement units (IMU). In an effort to increase the stability margin, the adaptive algorithm adjusts the attitude angle and the touch-down point of the swing leg. To reduce the slipping risk, a nonlinear control law is designed to determine the friction factor of the friction cone constraint from the inclination of the slope. We validate the effectiveness of the framework through a series of simulations. The automatic smooth transition from the flat to the unknown slope is achieved, and the robot is capable of walking in all directions on the slope. Notably, with reference to the climbing modal of blue sheep, the robot successfully climbed a 42.4° slope, proving the ultimate ability of the proposed framework. Full article

(This article belongs to the Special Issue Motion Planning and Advanced Control for Robotics)

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21 pages, 7027 KiB

Open AccessEditor’s ChoiceArticle

CNN Model with Multilayer ASPP and Two-Step Cross-Stage for Semantic Segmentation

by Min-Hong Park, Jae-Hoon Cho and Yong-Tae Kim

Machines 2023, 11(2), 126; https://doi.org/10.3390/machines11020126 - 17 Jan 2023

Cited by 5 | Viewed by 2213

Currently, interest in deep learning-based semantic segmentation is increasing in various fields such as the medical field, automatic operation, and object division. For example, UNet, a deep learning network with an encoder–decoder structure, is used for image segmentation in the biomedical area, and [...] Read more.

Currently, interest in deep learning-based semantic segmentation is increasing in various fields such as the medical field, automatic operation, and object division. For example, UNet, a deep learning network with an encoder–decoder structure, is used for image segmentation in the biomedical area, and an attempt to segment various objects is made using ASPP such as Deeplab. A recent study improves the accuracy of object segmentation through structures that extend in various receptive fields. Semantic segmentation has evolved to divide objects of various sizes more accurately and in detail, and various methods have been presented for this. In this paper, we propose a model structure that reduces the overall parameters of the deep learning model in this development and improves accuracy. The proposed model is an encoder–decoder structure, and an encoder half scale provides a feature map with few encoder parameters. A decoder integrates feature maps of various scales with high area details and forward features of low areas. An integrated feature map learns a feature map of each encoder hierarchy over an area of previous data in the form of a continuous coupling structure. To verify the performance of the model, we learned and compared the KITTI-360 dataset with the Cityscapes dataset, and experimentally confirmed that the proposed method was superior to the existing model. Full article

(This article belongs to the Section Robotics, Mechatronics and Intelligent Machines)

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21 pages, 4474 KiB

Open AccessEditor’s ChoiceArticle

Numerical Investigation on the Combustion and Emission Characteristics of Diesel Engine with Flexible Fuel Injection

by Qihao Mei, Intarat Naruemon, Long Liu, Yue Wu and Xiuzhen Ma

Machines 2023, 11(1), 120; https://doi.org/10.3390/machines11010120 - 16 Jan 2023

Cited by 3 | Viewed by 2168

As the main engineering power plant, diesel engines are irreplaceable in the future. However, the stringent emission regulations impose many tough requirements to their developments. Recently, flexible fuel injection strategy has been recognized as an effective technology in creating an advanced spray and [...] Read more.

As the main engineering power plant, diesel engines are irreplaceable in the future. However, the stringent emission regulations impose many tough requirements to their developments. Recently, flexible fuel injection strategy has been recognized as an effective technology in creating an advanced spray and mixture formation and improving combustion efficiency indirectly. However, the detailed combustion and emission behaviors under flexible fuel injection are still unknown. Therefore, this paper aims to investigate the combustion and emission characteristics under flexible fuel injection and explore an optimal injection strategy for high-efficiency combustion. A numerical simulation method is conducted by coupling the large-eddy simulation (LES) model and the SAGE combustion model. Then, the spray mixing, combustion flame propagation and emissions formation under various multiple-injection strategies are investigated. Results reveal that initial an ultrahigh injection pressure has a significant influence on the spray’s axial penetration while dwell time mainly affects the spray’s radial expansion. Under an initial ultrahigh injection pressure, the turbulence kinetic energy (TKE) becomes larger, and the vortex motions are stronger, contributing to a better spray turbulent mixing. Meanwhile, a snatchier flame structure with a favorable level of equivalence ratio and a homogeneous temperature distribution is obtained. In this way, the peak heat release rate (HRR) could increase by 46.7% with a 16.7% reduction in soot formation and a 31.4% reduction in NO_x formation. Full article

(This article belongs to the Special Issue Advances in Combustion Science for Future IC Engines)

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22 pages, 6534 KiB

Open AccessEditor’s ChoiceArticle

Modification and Validation of 1D Loss Models for the Off-Design Performance Prediction of Centrifugal Compressors with Splitter Blades

by Xiuxin Yang, Yan Liu and Guang Zhao

Machines 2023, 11(1), 118; https://doi.org/10.3390/machines11010118 - 15 Jan 2023

Cited by 2 | Viewed by 2014

One-dimensional (1D) aerodynamic performance predictions are very often conducted by researchers and designers during the preliminary design of centrifugal compressors. This paper focuses on a 1D prediction method for centrifugal compressors with splitter blades, which is rarely seen in the open literature. One-dimensional [...] Read more.

One-dimensional (1D) aerodynamic performance predictions are very often conducted by researchers and designers during the preliminary design of centrifugal compressors. This paper focuses on a 1D prediction method for centrifugal compressors with splitter blades, which is rarely seen in the open literature. One-dimensional prediction of aerodynamic overall performance is made for centrifugal compressors with different technical design specifications. However, the aerodynamic overall prediction accuracy relies on the accuracy of the 1D-loss-models used. Therefore, an optimum combination of loss models is proposed by summarizing a variety of loss models presented in the public literature. In addition, an optimization method is utilized to optimize some coefficients involved in loss models in order to improve the generality of the combined model. The modified models obtained in this study are proved to have good predictive accuracy. Full article

(This article belongs to the Section Turbomachinery)

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18 pages, 4867 KiB

Open AccessEditor’s ChoiceArticle

The Graph Neural Network Detector Based on Neighbor Feature Alignment Mechanism in LIDAR Point Clouds

by Xinyi Liu, Baofeng Zhang and Na Liu

Machines 2023, 11(1), 116; https://doi.org/10.3390/machines11010116 - 14 Jan 2023

Cited by 2 | Viewed by 2155

Three-dimensional (3D) object detection has a vital effect on the environmental awareness task of autonomous driving scenarios. At present, the accuracy of 3D object detection has significant improvement potential. In addition, a 3D point cloud is not uniformly distributed on a regular grid [...] Read more.

Three-dimensional (3D) object detection has a vital effect on the environmental awareness task of autonomous driving scenarios. At present, the accuracy of 3D object detection has significant improvement potential. In addition, a 3D point cloud is not uniformly distributed on a regular grid because of its disorder, dispersion, and sparseness. The strategy of the convolution neural networks (CNNs) for 3D point cloud feature extraction has the limitations of potential information loss and empty operation. Therefore, we propose a graph neural network (GNN) detector based on neighbor feature alignment mechanism for 3D object detection in LiDAR point clouds. This method exploits the structural information of graphs, and it aggregates the neighbor and edge features to update the state of vertices during the iteration process. This method enables the reduction of the offset error of the vertices, and ensures the invariance of the point cloud in the spatial domain. For experiments performed on the KITTI public benchmark, the results demonstrate that the proposed method achieves competitive experimental results. Full article

(This article belongs to the Special Issue Autonomous Driving: Advancements in Cognitive Perception Systems for Increased Level Autonomy)

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29 pages, 11741 KiB

Open AccessEditor’s ChoiceArticle

Fault Location in Distribution Network by Solving the Optimization Problem Based on Power System Status Estimation Using the PMU

by Masoud Dashtdar, Arif Hussain, Hassan Z. Al Garni, Abdullahi Abubakar Mas’ud, Waseem Haider, Kareem M. AboRas and Hossam Kotb

Machines 2023, 11(1), 109; https://doi.org/10.3390/machines11010109 - 13 Jan 2023

Cited by 18 | Viewed by 4699

Fault location is one of the main challenges in the distribution network due to its expanse and complexity. Today, with the advent of phasor measurement units (PMU), various techniques for fault location using these devices have been proposed. In this research, distribution network [...] Read more.

Fault location is one of the main challenges in the distribution network due to its expanse and complexity. Today, with the advent of phasor measurement units (PMU), various techniques for fault location using these devices have been proposed. In this research, distribution network fault location is defined as an optimization problem, and the network fault location is determined by solving it. This is done by combining PMU data before and after the fault with the power system status estimation (PSSE) problem. Two new objective functions are designed to identify the faulty section and fault location based on calculating the voltage difference between the two ends of the grid lines. In the proposed algorithm, the purpose of combining the PMU in the PSSE problem is to estimate the voltage and current quantities at the branch point and the total network nodes after the fault occurs. Branch point quantities are calculated using the PMU and the governing equations of the π line model for each network section, and the faulty section is identified based on a comparison of the resulting values. The advantages of the proposed algorithm include simplicity, step-by-step implementation, efficiency in conditions of different branch specifications, application for various types of faults including short-circuit and series, and its optimal accuracy compared to other methods. Finally, the proposed algorithm has been implemented on the IEEE 123-node distribution feeder and its performance has been evaluated for changes in various factors including fault resistance, type of fault, angle of occurrence of a fault, uncertainty in loading states, and PMU measurement error. The results show the appropriate accuracy of the proposed algorithm showing that it was able to determine the location of the fault with a maximum error of 1.21% at a maximum time of 23.87 s. Full article

(This article belongs to the Section Electromechanical Energy Conversion Systems)

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16 pages, 1331 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Reaching-Law-Based Discrete-Time Terminal Sliding Mode Current Control of a Six-Phase Induction Motor

by Yassine Kali, Jorge Rodas, Jesus Doval-Gandoy, Magno Ayala and Osvaldo Gonzalez

Machines 2023, 11(1), 107; https://doi.org/10.3390/machines11010107 - 13 Jan 2023

Cited by 7 | Viewed by 4156

This paper develops an inner stator current controller based on an enhanced reaching-law-based discrete-time terminal sliding mode. The problem of tracking stator currents with high accuracy while ensuring the robustness of a six-phase induction motor in the presence of uncertain electrical parameters and [...] Read more.

This paper develops an inner stator current controller based on an enhanced reaching-law-based discrete-time terminal sliding mode. The problem of tracking stator currents with high accuracy while ensuring the robustness of a six-phase induction motor in the presence of uncertain electrical parameters and unmeasurable states is tackled. The unknown dynamics are approximated by using a time delay estimation method. Then, an enhanced power-reaching law is used to make each stage of the convergence faster. A stability analysis and the system controller’s finite-time convergence are demonstrated in detail. Practical work was conducted on an asymmetrical six-phase induction machine to illustrate the developed discrete approach’s robustness and effectiveness. Full article

(This article belongs to the Special Issue Innovative Applications of Multiphase Machines)

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18 pages, 4130 KiB

Open AccessEditor’s ChoiceArticle

Path Planning of Unmanned Aerial Vehicle in Complex Environments Based on State-Detection Twin Delayed Deep Deterministic Policy Gradient

by Danyang Zhang, Zhaolong Xuan, Yang Zhang, Jiangyi Yao, Xi Li and Xiongwei Li

Machines 2023, 11(1), 108; https://doi.org/10.3390/machines11010108 - 13 Jan 2023

Cited by 7 | Viewed by 2628

This paper investigates the path planning problem of an unmanned aerial vehicle (UAV) for completing a raid mission through ultra-low altitude flight in complex environments. The UAV needs to avoid radar detection areas, low-altitude static obstacles, and low-altitude dynamic obstacles during the flight [...] Read more.

This paper investigates the path planning problem of an unmanned aerial vehicle (UAV) for completing a raid mission through ultra-low altitude flight in complex environments. The UAV needs to avoid radar detection areas, low-altitude static obstacles, and low-altitude dynamic obstacles during the flight process. Due to the uncertainty of low-altitude dynamic obstacle movement, this can slow down the convergence of existing algorithm models and also reduce the mission success rate of UAVs. In order to solve this problem, this paper designs a state detection method to encode the environmental state of the UAV’s direction of travel and compress the environmental state space. In considering the continuity of the state space and action space, the SD-TD3 algorithm is proposed in combination with the double-delayed deep deterministic policy gradient algorithm (TD3), which can accelerate the training convergence speed and improve the obstacle avoidance capability of the algorithm model. Further, to address the sparse reward problem of traditional reinforcement learning, a heuristic dynamic reward function is designed to give real-time rewards and guide the UAV to complete the task. The simulation results show that the training results of the SD-TD3 algorithm converge faster than the TD3 algorithm, and the actual results of the converged model are better. Full article

(This article belongs to the Topic Design, Simulation and New Applications of Unmanned Aerial Vehicles)

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15 pages, 15285 KiB

Open AccessEditor’s ChoiceArticle

4D Printing of Hydrogels Controlled by Hinge Structure and Spatially Gradient Swelling for Soft Robots

by Masanari Kameoka, Yosuke Watanabe, MD Nahin Islam Shiblee, Masaru Kawakami, Jun Ogawa, Ajit Khosla, Hidemitsu Furukawa, Shengyang Zhang, Shinichi Hirai and Zhongkui Wang

Machines 2023, 11(1), 103; https://doi.org/10.3390/machines11010103 - 12 Jan 2023

Cited by 8 | Viewed by 2847

In 4D printing, structures with gradients in physical properties are 3D printed in order to dramatically increase deformation. For example, printing bilayer structures with passive and active layers has been proposed, however, these methods have the disadvantages that the material of each layer [...] Read more.

In 4D printing, structures with gradients in physical properties are 3D printed in order to dramatically increase deformation. For example, printing bilayer structures with passive and active layers has been proposed, however, these methods have the disadvantages that the material of each layer is mixed, and the modeling process is complicated. Herein, we present a method of creating gradient gels with different degrees of polymerization on the UV-exposed side and the other side using a single material by simply increasing the amount of initiator. This gel is the first example in which the differential swelling ratio between two sides causes the gradient to curl inward toward the UV-exposed side. The mechanical properties (swelling ratio and Young’s modulus) were measured at different material concentrations and structures, and the effects of each on deformation were analyzed and simulated. The results show that adding an initiator concentration of 0.2 (mol/L) or more causes deformation, that increasing the crosslinker concentration by a factor of three or more increases deformation, and that adding a hinge structure limits the gradient gel to deformation up to 90°. Thus, it was found that the maximum deformation can be predicted to some extent by simulation. In the future, we will be able to create complex structures while utilizing simulation. Full article

(This article belongs to the Special Issue Advance in Additive Manufacturing)

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18 pages, 5911 KiB

Open AccessEditor’s ChoiceArticle

Tribodynamic Modelling of High-Speed Rolling Element Bearings in Flexible Multi-Body Environments

by Harry Questa, Mahdi Mohammadpour, Stephanos Theodossiades, Colin P. Garner, Stephen R. Bewsher and Günter Offner

Machines 2023, 11(1), 93; https://doi.org/10.3390/machines11010093 - 11 Jan 2023

Cited by 1 | Viewed by 1982

This study presents a new flexible dynamic model for drive systems comprising lubricated bearings operating under conditions representative of electrified vehicle powertrains. The multi-physics approach importantly accounts for the tribological phenomena at the roller–race conjunction and models their effect on shaft-bearing system dynamics. [...] Read more.

This study presents a new flexible dynamic model for drive systems comprising lubricated bearings operating under conditions representative of electrified vehicle powertrains. The multi-physics approach importantly accounts for the tribological phenomena at the roller–race conjunction and models their effect on shaft-bearing system dynamics. This is achieved by embedding a non-linear lubricated bearing model within a flexible system level model; this is something which has not, to the authors’ knowledge, been reported on hitherto. The elastohydrodynamic (EHL) film is shown to increase contact deflection, leading to increased contact forces and total bearing stiffness as rotational speeds increase. Results show that for a 68 Nm hub motor operating up to 21,000 rpm, the input bearing EHL film reaches a thickness of 4.15

μ

m. The lubricant entrainment increases the roller–race contact deflection, causing the contact stiffness to increase non-linearly with speed. The contribution of the lubricant film leads to a 16.6% greater bearing stiffness at 21,000 rpm when compared to conventional dry-bearing modelling methods used in current multi-body dynamic software. This new methodology leads to more accurate dynamic response of high-speed systems necessary for the next generation of electrified vehicles. Full article

(This article belongs to the Special Issue Friction and Lubrication of Rolling Element Bearings)

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