Machines

17 pages, 6826 KiB

Open AccessEditor’s ChoiceArticle

Design, Modelling and Optimization of a High Power Density Axial Flux SRM with Reduced Torque Ripple for Electric Vehicles

by Akbar Mohammadi Ajamloo, Mohamed N. Ibrahim and Peter Sergeant

Machines 2023, 11(7), 759; https://doi.org/10.3390/machines11070759 - 20 Jul 2023

Cited by 8 | Viewed by 2245

Abstract

Switched reluctance machines (SRMs) are potential candidates for use in the propulsion systems of electric vehicles. However, they suffer from low power density and high torque ripple. In this paper, a segmented rotor double-sided axial flux SRM (DSAFSRM) is chosen for detailed analysis. [...] Read more.

Switched reluctance machines (SRMs) are potential candidates for use in the propulsion systems of electric vehicles. However, they suffer from low power density and high torque ripple. In this paper, a segmented rotor double-sided axial flux SRM (DSAFSRM) is chosen for detailed analysis. A hybrid design algorithm is proposed to take the effects of iron non-linearity into account. The proposed design procedure benefits from simplicity and high accuracy at the same time. A two-step optimization procedure is presented which minimizes the torque ripple of the DSAFSRM without jeopardizing its efficiency. The torque ripple is reduced from 120% to 35% after optimization. In the two-step optimization procedure, both geometrical and switching related parameters are investigated. Moreover, a double-sided radial flux SRM is designed and compared with the proposed DSAFSRM in terms of torque ripple, average torque, efficiency and power density. The results indicate superior performance of the optimized DSAFSRM, especially in terms of average torque, which is 26% higher than the torque produced by the double-sided radial flux SRM. Full article

(This article belongs to the Special Issue Future Trends in Advanced Design of Electrical Machines, Drives and Electric Vehicles Using Additive Manufacturing Approaches)

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18 pages, 7609 KiB

Open AccessEditor’s ChoiceArticle

A Novel Sleeve Design to Reduce the Eddy Current Loss of High-Speed Electrical Machines

by Seung-Heon Lee, Si-Woo Song, Min-Jae Jeong, Won-Ho Kim and Dong-Hoon Jung

Machines 2023, 11(7), 756; https://doi.org/10.3390/machines11070756 - 19 Jul 2023

Cited by 2 | Viewed by 1859

Abstract

Demand for high-speed motors is increasing. Surface-mounted permanent magnet synchronous motors (SPMSM) used in high-speed applications have magnets attached to the rotor, so there is a risk of damage and scattering due to centrifugal force as the speed increases. For this reason, applying [...] Read more.

Demand for high-speed motors is increasing. Surface-mounted permanent magnet synchronous motors (SPMSM) used in high-speed applications have magnets attached to the rotor, so there is a risk of damage and scattering due to centrifugal force as the speed increases. For this reason, applying the retaining sleeve to the rotor is essential. However, when using sleeves, there is a problem of reducing efficiency due to eddy current loss. In this paper, a study was conducted on a motor for a 100 kW building air conditioning system operating at a speed of 20,000 rpm. The purpose of the study is to reduce eddy current loss by optimizing the sleeve geometry. To this end, 3D finite element analysis (FEA) using JMAG 22.1 was conducted to analyze eddy current loss, the minimum safety factor was analyzed through mechanical stiffness analysis using ANSYS Workbench, and the validity of sleeve shape was proved through cause analysis. Through the research results, it is expected that the shape change of the sleeve will have the effect of reducing eddy current loss. Full article

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

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21 pages, 5877 KiB

Open AccessEditor’s ChoiceReview

Research Progress on the Dynamic Characteristics of Planetary Gear Transmission in a Non-Inertial System

by Bingwei Gao, Yongkang Wang and Guangbin Yu

Machines 2023, 11(7), 751; https://doi.org/10.3390/machines11070751 - 18 Jul 2023

Viewed by 2364

Abstract

Planetary gear systems have many advantages over other gear systems. Previous studies on its dynamic characteristics mostly used Earth as the reference system, which is inconsistent with the actual working conditions of many planetary gear systems, such as aircraft maneuvering, vehicle movement changes, [...] Read more.

Planetary gear systems have many advantages over other gear systems. Previous studies on its dynamic characteristics mostly used Earth as the reference system, which is inconsistent with the actual working conditions of many planetary gear systems, such as aircraft maneuvering, vehicle movement changes, etc. By analyzing representative research papers, this study summarizes the lumped-parameter, finite element, and rigid–flexible coupling models commonly used in studying the traditional dynamic characteristics. Then, the research status of gear–rotor and planetary gear systems in inertial and non-inertial systems is summarized. The research progress of load characteristics, vibration characteristics, and vibration control of the traditional planetary gear system is summarized. Finally, some suggestions for future development are put forward. There are a few studies on the non-inertial dynamics of planetary gear systems. The three analysis models have distinct characteristics and applications but can all be used in non-inertial systems. The dynamic analysis method of non-inertial rotor systems can be combined with the dynamic study of gear systems. It is of practical significance to study the non-inertial dynamic characteristics of planetary gear systems. Scholars can refer to the non-inertial dynamic research of the gear–rotor system, select the analysis model according to the needs, and continue to study the dynamic characteristics of the planetary gear system under the non-inertial system. Full article

(This article belongs to the Special Issue Research on Rotor Dynamics and Vibration Control)

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20 pages, 29747 KiB

Open AccessEditor’s ChoiceArticle

Experimental Study on Fatigue Damage of Drilling Tool Materials Based on Magnetic Memory Detection

by Yingming He, Qilong Xue, Weiguo Hai, Xuesong Xing, Xudong Wu and Xing Fu

Machines 2023, 11(7), 701; https://doi.org/10.3390/machines11070701 - 2 Jul 2023

Viewed by 1098

Abstract

In drilling engineering, the cost of drilling tool fracture is enormous, and studying the fatigue failure process of drilling tools has practical significance. This paper uses metal magnetic memory detection technology to design and conduct fatigue damage tests on typical drilling tool material [...] Read more.

In drilling engineering, the cost of drilling tool fracture is enormous, and studying the fatigue failure process of drilling tools has practical significance. This paper uses metal magnetic memory detection technology to design and conduct fatigue damage tests on typical drilling tool material 42CrMo specimens under tensile, torsional, compressive, tensile, compressive, and torsional dynamic loading conditions. By analyzing the changes in the tangential component H_p(x) and gradient value K of the magnetic memory signal under different load conditions with the number of loading times, the process of fatigue failure of the specimens and the trend of changes in the magnetic memory signal in local stress concentration areas are explored. The characteristic parameters of fatigue damage based on magnetic memory detection were extracted and the critical point at which fatigue damage leads to crack initiation was inferred. This confirms that metal magnetic memory testing technology is an effective means of analyzing the fatigue damage process of drilling tools and provides a certain reference for formulating judgment standards for drilling tool maintenance on site. Full article

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

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19 pages, 4845 KiB

Open AccessEditor’s ChoiceArticle

Dynamics-Based Thermal Analysis of High-Speed Angular Contact Ball Bearings with Under-Race Lubrication

by Jintao Lei, Bing Su, Shuailong Zhang, Haisheng Yang and Yongcun Cui

Machines 2023, 11(7), 691; https://doi.org/10.3390/machines11070691 - 1 Jul 2023

Cited by 6 | Viewed by 2536

Abstract

The paper mainly studied the temperature rise characteristics of under-race lubricated high-speed angular contact ball bearings under operational conditions from the perspective of dynamics. The steady-state calculation model of the bearing was established using a thermal network method in consideration of the influence [...] Read more.

The paper mainly studied the temperature rise characteristics of under-race lubricated high-speed angular contact ball bearings under operational conditions from the perspective of dynamics. The steady-state calculation model of the bearing was established using a thermal network method in consideration of the influence factor of friction power consumption in bearing components based on a dynamic model. Following this, the steady-state change characteristics of the bearing were obtained by solving a thermal balance equation. Through this process, the influence laws of bearing rotation speed, oil supply, and environmental temperature on the friction temperature rise of the bearing were analyzed. Finally, the finite element analysis software ANSYS was employed to provide comparative verification. The results showed that the bearing temperature nonlinearly increased with the increase in inner ring rotation speed, and when it approached a certain critical value, the outer ring temperature exceeded the inner ring temperature. It had an obvious effect on controlling the temperature rise of the bearing inner ring by way of increasing the quantity and reducing the temperature of the lubricating oil supply. Comparative verification showed that the speed–temperature variation tendency from the dynamics-based thermal analysis well agrees with that of the finite element analysis. Full article

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

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22 pages, 1243 KiB

Open AccessEditor’s ChoiceReview

A Review of Prognostic and Health Management (PHM) Methods and Limitations for Marine Diesel Engines: New Research Directions

by Hla Gharib and György Kovács

Machines 2023, 11(7), 695; https://doi.org/10.3390/machines11070695 - 1 Jul 2023

Cited by 11 | Viewed by 11655

Abstract

Prognostic and health management (PHM) methods focus on improving the performance and reliability of systems with a high degree of complexity and criticality. These systems include engines, turbines, and robotic systems. PHM methods involve managing technical processes, such as condition monitoring, fault diagnosis, [...] Read more.

Prognostic and health management (PHM) methods focus on improving the performance and reliability of systems with a high degree of complexity and criticality. These systems include engines, turbines, and robotic systems. PHM methods involve managing technical processes, such as condition monitoring, fault diagnosis, health prognosis, and maintenance decision-making. Various software and applications deal with the processes mentioned above independently. We can also observe different development levels, making connecting all of the machine’s technical processes in one health management system with the best possible output a challenging task. This study’s objective was to outline the scope of PHM methods in real-time conditions and propose new directions to develop a decision support tool for marine diesel engines. In this paper, we illustrate PHM processes and the state of the art in the marine industry for each technical process. Then, we review PHM methods and limitations for marine diesel engines. Finally, we analyze future research opportunities for the marine industry and their role in developing systems’ performance and reliability. The main added value of the research is that a research gap was found in this research field, which is that new advanced PHM methods have to be implemented for marine diesel engines. Our suggestions to improve marine diesel engines’ operation and maintenance include implementing advanced PHM methods and utilizing predictive analytics and machine learning. Full article

(This article belongs to the Special Issue Condition-Based Maintenance, Instrumentation and Data Analysis Methods Aiming Efficient Operation of Internal Combustion Engines)

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25 pages, 8330 KiB

Open AccessEditor’s ChoiceArticle

Research into Dynamic Error Optimization Method of Impeller Blade Machining Based on Digital–Twin Technology

by Rongyi Li, Shanchao Wang, Chao Wang, Shanshan Wang, Bo Zhou, Xianli Liu and Xudong Zhao

Machines 2023, 11(7), 697; https://doi.org/10.3390/machines11070697 - 1 Jul 2023

Cited by 3 | Viewed by 1488

Abstract

A TC4 impeller blade is a typical weak, rigid, thin–walled part. The contact area between a cutting tool and a workpiece has strong time–varying characteristics. This leads to a strong non–linear variation in cutting load. So, in this kind of part, the processing [...] Read more.

A TC4 impeller blade is a typical weak, rigid, thin–walled part. The contact area between a cutting tool and a workpiece has strong time–varying characteristics. This leads to a strong non–linear variation in cutting load. So, in this kind of part, the processing error is difficult to control. To solve this problem, a method of processing error prediction and intelligent controlling which considers the effect of tool wear time variation is proposed by combining digital–twinning technology. Firstly, an iterative model for digital–twin process optimization is constructed. Secondly, an iterative prediction model of the machining position following the milling force and considering the effect of tool wear is proposed. Based on these models, the machining error of the TC4 impeller blade under dynamic load is predicted. Dynamic machining error prediction and intelligent control are realized by combining the digital–twin model and the multi–objective process algorithm. Finally, the machining error optimization effect of the proposed digital–twin model is verified via a comparison experiment of impeller blade milling. In terms of the precision of milling force mapping, the average error after optimization is less than 8%. The maximum error is no more than 14%. In terms of the optimization effect, the average error of the optimized workpiece contour is reduced by about 20%. The peak contour error is reduced by approximately 35%. Full article

(This article belongs to the Special Issue Recent Progress of Thin Wall Machining)

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16 pages, 4199 KiB

Open AccessEditor’s ChoiceArticle

Computational Fluid Dynamics Simulation and Optimization of Hydropneumatic Spring Damper Valves for Heavy Vehicle Applications

by Wei Nie, Hongwen He, Luming Sha, Chao Wang and Fu Du

Machines 2023, 11(7), 680; https://doi.org/10.3390/machines11070680 - 25 Jun 2023

Cited by 2 | Viewed by 1508

Abstract

To satisfy the design requirements for a hydropneumatic spring damper valve, the inlet–outlet pressure drop (ΔP) and the axial force on the spool (F_Z) of a valve were investigated using fluid–solid coupling simulations and multi-objective optimization, along with [...] Read more.

To satisfy the design requirements for a hydropneumatic spring damper valve, the inlet–outlet pressure drop (ΔP) and the axial force on the spool (F_Z) of a valve were investigated using fluid–solid coupling simulations and multi-objective optimization, along with the effects of the diameters of three internal holes (D_A, D_B, and D_C) in the valve on the ΔP and the F_Z. First, a meshed computational fluid dynamics model of a damper valve was established based on its geometric structure. Next, the effects of the flow rate (Q) and the diameter of the damping hole in the internal structure on the ΔP and the F_Z of the damper valve were investigated. The results showed that the ΔP and the F_Z varied nonlinearly with Q. For a given Q, the ΔP decreased as D_A, D_B, and D_C increased. For a given Q, the F_Z was not related to D_A and D_C, but it decreased as D_B increased. Finally, the structure of the damper valve was optimized by defining the ΔP and the F_Z as the response variables and D_A, D_B, and D_C as the explanatory variables. The results showed that the best configuration of the hole diameters was D_A = 8.8 mm, D_B = 5.55 mm, and D_C = 6 mm. In this configuration, ΔP = 0.704 MPa and F_Z = 110.005 N. The ΔP of the optimized valve was closer to the middle value of the target range than that of the initial valve design. The difference between the simulated and target values of the F_Z decreased from 0.28% to 0.0045%, satisfying application requirements. Full article

(This article belongs to the Section Industrial Systems)

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29 pages, 775 KiB

Open AccessEditor’s ChoiceReview

Autonomous Vehicle Decision-Making and Control in Complex and Unconventional Scenarios—A Review

by Faizan Sana, Nasser L. Azad and Kaamran Raahemifar

Machines 2023, 11(7), 676; https://doi.org/10.3390/machines11070676 - 23 Jun 2023

Cited by 8 | Viewed by 9606

Abstract

The development of autonomous vehicles (AVs) is becoming increasingly important as the need for reliable and safe transportation grows. However, in order to achieve level 5 autonomy, it is crucial that such AVs can navigate through complex and unconventional scenarios. It has been [...] Read more.

The development of autonomous vehicles (AVs) is becoming increasingly important as the need for reliable and safe transportation grows. However, in order to achieve level 5 autonomy, it is crucial that such AVs can navigate through complex and unconventional scenarios. It has been observed that currently deployed AVs, like human drivers, struggle the most in cases of adverse weather conditions, unsignalized intersections, crosswalks, roundabouts, and near-accident scenarios. This review paper provides a comprehensive overview of the various navigation methodologies used in handling these situations. The paper discusses both traditional planning methods such as graph-based approaches and emerging solutions including machine-learning based approaches and other advanced decision-making and control techniques. The benefits and drawbacks of previous studies in this area are discussed in detail and it is identified that the biggest shortcomings and challenges are benchmarking, ensuring interpretability, incorporating safety as well as road user interactions, and unrealistic simplifications such as the availability of accurate and perfect perception information. Some suggestions to tackle these challenges are also presented. Full article

(This article belongs to the Special Issue Artificial Intelligence for Automatic Control of Vehicles)

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16 pages, 1466 KiB

Open AccessEditor’s ChoiceArticle

Integration of sEMG-Based Learning and Adaptive Fuzzy Sliding Mode Control for an Exoskeleton Assist-as-Needed Support System

by Pablo Delgado, Nathan Gonzalez and Yimesker Yihun

Machines 2023, 11(7), 671; https://doi.org/10.3390/machines11070671 - 21 Jun 2023

Cited by 3 | Viewed by 1309

Abstract

This paper presents an adaptive Fuzzy Sliding Mode Control approach for an Assist-as-Needed (AAN) strategy to achieve effective human–exoskeleton synergy. The proposed strategy employs an adaptive instance-based learning algorithm to estimate muscle effort, based on surface Electromyography (sEMG) signals. To determine and control [...] Read more.

This paper presents an adaptive Fuzzy Sliding Mode Control approach for an Assist-as-Needed (AAN) strategy to achieve effective human–exoskeleton synergy. The proposed strategy employs an adaptive instance-based learning algorithm to estimate muscle effort, based on surface Electromyography (sEMG) signals. To determine and control the inverse dynamics of a highly nonlinear 4-degrees-of-freedom exoskeleton designed for upper-limb therapeutic exercises, a modified Recursive Newton-Euler Algorithm (RNEA) with Sliding Mode Control (SMC) was used. The exoskeleton position error and raw sEMG signal from the bicep’s brachii muscle were used as inputs for a fuzzy inference system to produce an output to adjust the sliding mode control law parameters. The proposed robust control law was simulated using MATLAB-Simulink, and the results showed that it could instantly adjust the necessary support, based on the combined motion of the human–exoskeleton system’s muscle engagement, while keeping the state trajectory errors and input torque bounded within

\pm 5 \times 10^{- 2}

rads and

\pm 5

N.m, respectively. Full article

(This article belongs to the Special Issue State-of-the-Art in Service and Rehabilitation Machines)

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18 pages, 5245 KiB

Open AccessEditor’s ChoiceArticle

Influence of Cutting Parameters and Tool Geometry on Topography of Hard Turned Surfaces

by Viktor Molnar

Machines 2023, 11(6), 665; https://doi.org/10.3390/machines11060665 - 20 Jun 2023

Cited by 2 | Viewed by 1038

Abstract

Three-dimensional topography measurement is a focus area of precision machining because it provides detailed information on the functional behavior of contacting surfaces. The purpose of this study is to analyze how the process parameters and the edge geometry of the cutting insert influence [...] Read more.

Three-dimensional topography measurement is a focus area of precision machining because it provides detailed information on the functional behavior of contacting surfaces. The purpose of this study is to analyze how the process parameters and the edge geometry of the cutting insert influence the topographical characteristics of hardened 16MnCr5 steel surfaces and to determine the favorable combinations of technology parameter values based on the analyzed topography parameters (Ssk, Sku, Sz, Sa, Sk, Spk, Svk). A research question is whether the analyzed parameters can be substituted by each other or not. A hard turning experiment was carried out based on a full factorial design of experiments, and the areas of the machined surfaces were scanned and analyzed by analysis of variance, regression analysis (response function), and correlation analysis. It was found that there are strong correlations between the topography parameters that allow the substitution of one with another; the main influencing cutting parameter is the feed rate for both insert types. The contributions of the study are the numerical information with regard to the correlations among the topography parameters, as well as the extent of the influence of cutting parameters. Full article

(This article belongs to the Section Advanced Manufacturing)

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18 pages, 18905 KiB

Open AccessEditor’s ChoiceArticle

Investigating the Stiffness Characteristics of a Tendon-Driven Continuum Manipulator Using Sensitivity Analysis: A Case Study in Transoral Laser Microsurgery

by Kapil Sawant, Antonios E. Gkikakis and Leonardo S. Mattos

Machines 2023, 11(6), 662; https://doi.org/10.3390/machines11060662 - 19 Jun 2023

Cited by 3 | Viewed by 1613

Abstract

Continuum manipulators, with their characteristics of flexibility and dexterity, have gained significant interest in various applications across industries such as inspection, manufacturing, space exploration, and medical surgery. However, because of their inherent compliance, handling payloads may prove challenging due to shape distortion and [...] Read more.

Continuum manipulators, with their characteristics of flexibility and dexterity, have gained significant interest in various applications across industries such as inspection, manufacturing, space exploration, and medical surgery. However, because of their inherent compliance, handling payloads may prove challenging due to shape distortion and deflection. This demonstrates the need to optimize the manipulator’s stiffness. The primary objective of this work was to show the merits of sensitivity analysis in the design of flexible surgical manipulators. Such analysis can guide important design decisions and enable the more efficient use of available resources, contributing to designing more effective prototypes. A new sensitivity analysis framework based on a multi-model and a multi-method approach was proposed to achieve this. This framework was then demonstrated by studying a tendon-driven rolling contact joint hyper-redundant manipulator for transoral laser microsurgery. In this analysis, the effects of independent design parameters on the stiffness of the manipulator were examined. Then, scaled-up 3D-printed prototypes were used to validate the accuracy of the stiffness model experimentally, which enabled us to assess the outcome of the sensitivity analysis framework. The results demonstrated that only two out of five design parameters for the considered manipulator significantly impacted the device’s performance. This information could enable the designer to efficiently allocate resources toward correctly setting these two most important parameters to achieve the desired system. Overall, the proposed analysis framework is a general tool that can be applied to any design architecture, helping to develop optimal manipulators for various applications. Full article

(This article belongs to the Special Issue Robots in Healthcare: Design, Control and Applications)

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24 pages, 4797 KiB

Open AccessEditor’s ChoiceArticle

Hardware-in-the-Loop Scheme of Linear Controllers Tuned through Genetic Algorithms for BLDC Motor Used in Electric Scooter under Variable Operation Conditions

by Leonardo Esteban Moreno-Suarez, Luis Morales-Velazquez, Arturo Yosimar Jaen-Cuellar and Roque Alfredo Osornio-Rios

Machines 2023, 11(6), 663; https://doi.org/10.3390/machines11060663 - 19 Jun 2023

Cited by 4 | Viewed by 2070

Abstract

Outrunner brushless DC motors (BLDC) are a type of permanent magnet synchronous motor (PMSM) widely used in electric micro-mobility vehicles, such as scooters, electric bicycles, wheelchairs, and segways, among others. Those vehicles have many operational constraints because they are driven directly by the [...] Read more.

Outrunner brushless DC motors (BLDC) are a type of permanent magnet synchronous motor (PMSM) widely used in electric micro-mobility vehicles, such as scooters, electric bicycles, wheelchairs, and segways, among others. Those vehicles have many operational constraints because they are driven directly by the user with light protective wearing. Therefore, to improve control strategies to make the drive safer, it is essential to model the traction system over a wide range of operating conditions in a street environment. In this work, we developed an electro-mechanical model based on the Hardware-in-the-Loop (HIL) structure for a two-wheeler electric scooter, using the BLDC motor to explore its response and to test linear controllers for speed and torque management under variable operating conditions. The proposed model includes motor parameters, power electronics component characteristics, mechanical structure, and external operating conditions. Meanwhile the linear controllers will be adjusted or tuned though a heuristic approach based on Genetic Algorithms (GAs) to optimize the system’s response. The HIL scheme will be able to simulate a wide range of conditions such as user weight, slopes, wind speed changes, and combined conditions. The designed model can be used to improve the design of the controller and estimate mechanical and electrical loads. Finally, the results of the controller tests show how the proposed cascade scheme, tuned through the GA, improves the system behavior and reduces the mean square error with respect to a classical tuning approach between 20% and 60%. Full article

(This article belongs to the Special Issue Condition-Based Monitoring of Electrical Machines)

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19 pages, 5883 KiB

Open AccessEditor’s ChoiceArticle

Dynamic Modeling and Performance Evaluation of a 5-DOF Hybrid Robot for Composite Material Machining

by Xiaojian Wang, Jun Wu and Yulin Zhou

Machines 2023, 11(6), 652; https://doi.org/10.3390/machines11060652 - 16 Jun 2023

Cited by 2 | Viewed by 1270

Abstract

Dynamic performance is an important performance of robots used for machine processing. This paper studies the dynamic modeling and evaluation method of a 5-DOF (Degree of Freedom) hybrid robot used in aerospace composite material processing. With the consideration of the dynamics of the [...] Read more.

Dynamic performance is an important performance of robots used for machine processing. This paper studies the dynamic modeling and evaluation method of a 5-DOF (Degree of Freedom) hybrid robot used in aerospace composite material processing. With the consideration of the dynamics of the serial part, the complete dynamic model of the hybrid robot is established based on the virtual work principle. In addition to the widely considered acceleration term, a dynamic performance evaluation index that comprehensively considers the acceleration term, velocity term and gravity term in the dynamic model is proposed. Using the dynamic performance index, the effect of the placement direction of the robot and the arrangement of the double symmetric limbs on robot dynamics are investigated. The results indicate that the vertical placement is beneficial to the dynamics of the hybrid robot, and the arrangement of double symmetric limbs has different effects on different limbs. Full article

(This article belongs to the Special Issue Advances in Parallel Robots and Mechanisms)

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18 pages, 2955 KiB

Open AccessEditor’s ChoiceArticle

The Friction of Radially Loaded Hybrid Spindle Bearings under High Speeds

by Marcus Gärtner, Christian Brecher, Stephan Neus, Hans-Martin Eckel, Andreas Bartelt, Maik Hoppert and Mohammad Reza Ilkhani

Machines 2023, 11(6), 649; https://doi.org/10.3390/machines11060649 - 15 Jun 2023

Cited by 1 | Viewed by 1616

Abstract

Friction losses are an important parameter for evaluating the operational behaviour of high-speed rolling bearings. Specifically, in machine tool applications, the bearings are subjected to high radial loads and high speeds, which lead to increased forces in the rolling contact and, as a [...] Read more.

Friction losses are an important parameter for evaluating the operational behaviour of high-speed rolling bearings. Specifically, in machine tool applications, the bearings are subjected to high radial loads and high speeds, which lead to increased forces in the rolling contact and, as a result, increased bearing friction. In this high-speed application, hybrid spindle bearings, typically made of ceramic balls and steel raceways, show better frictional behaviour compared to full steel-made bearings. Therefore, precise knowledge of the friction characteristics of high-speed hybrid bearings can improve friction models and generalise them to spindle bearings with different types, geometries, and operating conditions. In this article, a new straightforward and cost-efficient method for measuring the frictional torque in spindle bearings is presented. A rigidly arranged 7008 hybrid spindle bearing pair was tested up to rotational speeds of 24,000 rpm and high radial loads of 3 kN. The effects of oil–air and grease lubrication are discussed in characteristic diagrams of the tested bearings. Then, based on the test results, a friction calculation model is presented and validated for the outer race control and minimised power dissipation regarding the influence of radial forces. Full article

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

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13 pages, 1282 KiB

Open AccessEditor’s ChoiceArticle

Fused Filament Fabrication and Injection Moulding of Plastic Packaging: An Environmental and Financial Comparative Assessment

by Cheryl Marie Bezzina and Paul Refalo

Machines 2023, 11(6), 634; https://doi.org/10.3390/machines11060634 - 7 Jun 2023

Cited by 2 | Viewed by 1532

Abstract

The drive towards smart and sustainable manufacturing is leading companies to opt for environmentally conscious technologies. This study assesses the environmental and financial feasibility of using additive manufacturing, in this case, fused filament fabrication (FFF), instead of injection moulding (IM) to mass-produce cosmetic [...] Read more.

The drive towards smart and sustainable manufacturing is leading companies to opt for environmentally conscious technologies. This study assesses the environmental and financial feasibility of using additive manufacturing, in this case, fused filament fabrication (FFF), instead of injection moulding (IM) to mass-produce cosmetic plastic packaging. Using a life cycle assessment (LCA), the environmental impacts of the raw material production and manufacturing processes were assessed for both technologies. The results showed that using FFF creates a five times greater environmental impact, with printing energy consumption generating 80% of the impact. Using costing models, the cost per product produced using IM and FFF was evaluated, and the models showed that the raw material costs comprise the highest share in both cases. A net present value (NPV) model over twelve years indicated that the FFF NPV was seventeen times higher than that of IM. When testing for quality, the packages produced using IM were superior overall. This study concludes that FFF is more expensive and environmentally impactful when compared to IM. Full article

(This article belongs to the Special Issue Assessing New Trends in Sustainable and Smart Manufacturing)

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23 pages, 980 KiB

Open AccessEditor’s ChoiceArticle

Decentralized Adaptive Quantized Dynamic Surface Control for a Class of Flexible Hypersonic Flight Vehicles with Input Quantization

by Wenyan Zhao, Zeyu Lu, Zijian Bi, Cheng Zhong, Dianxiong Tian, Yanhui Zhang, Xiuyu Zhang and Guoqiang Zhu

Machines 2023, 11(6), 630; https://doi.org/10.3390/machines11060630 - 6 Jun 2023

Cited by 1 | Viewed by 1082

Abstract

A control strategy for a certain class of hypersonic flight aircraft dynamic models with unknown parameters is proposed in this article. The strategy is adaptive dynamic surface input quantization control. To address the issues in conventional inversion control, a first-order low-pass filter and [...] Read more.

A control strategy for a certain class of hypersonic flight aircraft dynamic models with unknown parameters is proposed in this article. The strategy is adaptive dynamic surface input quantization control. To address the issues in conventional inversion control, a first-order low-pass filter and an adaptive parameter minimum learning law are introduced in the control system design process. This method has the following features: (1) it solves the problem of repeated differentiation of the virtual control law in the conventional back-stepping method, greatly simplifying the control law structure; (2) by using the norm of the neural network weight vector as the adaptive adjustment parameter instead of updating each element online, the number of adaptive adjustment parameters is significantly reduced, improving the execution efficiency of the controller; (3) the introduced hysteresis quantizer overcomes the disadvantage of the quantization accuracy deterioration when the input value is too low in the logarithm quantizer, improving the accuracy of the quantizer. Stability analysis has shown that all signals in the closed-loop system are semi-globally uniformly bounded, and simulation results have verified the effectiveness of the proposed adaptive quantized control scheme. Full article

(This article belongs to the Special Issue Advanced Methodology of Intelligent Control and Measurement)

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19 pages, 1269 KiB

Open AccessEditor’s ChoiceArticle

An Experimental Methodology for Introducing Educational Robotics and Storytelling in Therapeutical Activities for Children with Neurodevelopmental Disorders

by Elena Peribañez, Sofia Bayona, Jose San Martin, Ana Verde, Carlos Garre, Janika Leoste and Luis Pastor

Machines 2023, 11(6), 629; https://doi.org/10.3390/machines11060629 - 6 Jun 2023

Cited by 1 | Viewed by 1953

Abstract

Educational robotics is a valuable tool in education and therapy for children with neurodevelopmental disorders (NDD), especially when introduced in activities, combined with gamification and storytelling elements. However, the lack of familiarity of therapists with the technologies involved makes their widespread introduction difficult [...] Read more.

Educational robotics is a valuable tool in education and therapy for children with neurodevelopmental disorders (NDD), especially when introduced in activities, combined with gamification and storytelling elements. However, the lack of familiarity of therapists with the technologies involved makes their widespread introduction difficult and leads to case-specific rather than more generalizable methods. In this paper, we present an experimental methodology which provides a guide for the introduction of these elements in therapeutical activities with children with NDD. Providing a common framework reduces the gap between the different expertise of therapists, educators, and engineers. While establishing a common vocabulary and objectives, the methodology provides a guide for designing activities and evaluating their therapeutic effectiveness. We provide an example with a pilot study using a low-cost robot (Ozobot) in a therapeutic environment. Results regarding the children’s task involvement, level of attention, and use of social skills were positive. In addition, the attitude of some children changed throughout the sessions, improving frustration tolerance. The discussion of the pilot study provides clues for improving future implementations of the presented methodology, which serves as a framework for the design of future experiments that include therapeutic activities with educational robotics, gamification, and storytelling. Full article

(This article belongs to the Special Issue Robots in Healthcare: Design, Control and Applications)

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21 pages, 14316 KiB

Open AccessEditor’s ChoiceArticle

Research on Additive Technique Parameter Optimization for Robotic Gripper Construction

by Emilian Paduraru, Catalin-Gabriel Dumitras, Dragos-Florin Chitariu, Mihaita Horodinca and Florin Chifan

Machines 2023, 11(6), 621; https://doi.org/10.3390/machines11060621 - 4 Jun 2023

Cited by 1 | Viewed by 2971

Abstract

Designing an industrial robot gripper suitable for today’s industry is a challenging task due to the rapid evolution of products. Industrial robots are involved in machining, the transfer of parts, control and assembly, and the number of tasks performed by robots are increasing. [...] Read more.

Designing an industrial robot gripper suitable for today’s industry is a challenging task due to the rapid evolution of products. Industrial robots are involved in machining, the transfer of parts, control and assembly, and the number of tasks performed by robots are increasing. Robots need to have the capability to adapt to new jobs consisting of new parts and new trajectories, and in most cases the preferred end effectors are grippers. In turn, grippers need to be flexible enough in order to cope with these changes. For this research, the authors propose a new gripper design which is capable of handling a large variety of parts with different sizes and shapes. In this research, an electrically actuated four-jaw gripper, with the capability of parallel movement of its jaws, is presented that also has the capability to fold the clamping jaws two by two and become a two-jaw gripper. Since the design is most suitable for additive manufacturing techniques, different additive techniques are analyzed for the manufacturing of the gripper. In the second part of the paper, different setups of the 3D printers are considered, such as infill percentage, raster angle and layer height. The main material on focus is a PET with grinded carbon-fiber reinforcement, but different materials are used for a better comparison of the rigidity of the system. This comparison is also presented in this article. The analysis of the material and 3D printing parameters are tested with Standard D638-14 probes used in a traction testing machine. After performing the traction test, the results are compared with FEA analysis. An optimal solution based on the experimental tests is proposed for the manufacture of the proposed gripper design. Full article

(This article belongs to the Section Industrial Systems)

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23 pages, 5713 KiB

Open AccessEditor’s ChoiceArticle

A New Cable-Driven Model for Under-Actuated Force–Torque Sensitive Mechanisms

by Giovanni Gerardo Muscolo and Paolo Fiorini

Machines 2023, 11(6), 617; https://doi.org/10.3390/machines11060617 - 3 Jun 2023

Cited by 3 | Viewed by 2227

Abstract

Force–torque sensors are used in many and different domains (i.e., space, medicine, biology, etc.). Design solutions of force–torque sensors can be conceived by using many types of connections or components; however, there are only a few sensors designed using cable-driven systems. This could [...] Read more.

Force–torque sensors are used in many and different domains (i.e., space, medicine, biology, etc.). Design solutions of force–torque sensors can be conceived by using many types of connections or components; however, there are only a few sensors designed using cable-driven systems. This could be related to many reasons, one of which being that cables are able only to pull and not push. In this paper, a new cable-driven model for under-actuated force–torque sensing mechanisms is proposed, simulated, and tested, underlining the novelty of using cables for force–torque sensing. Analytical formulations, simulations, and physical implementations are presented in this paper. Results confirm that the new proposed model can be used for force–torque sensing mechanisms in micro- and macro- applications where under-actuation is a fundamental requirement, as in robotic surgery. The proposed model and mechanism can be used in the design of sensors and actuators. The innovative model is validated with two different test benches, opening new challenges in the design and development of under-actuated force–torque transducers. Full article

(This article belongs to the Special Issue Variable Stiffness Physical Interaction in Robotic Devices and Machines)

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30 pages, 26046 KiB

Open AccessEditor’s ChoiceArticle

Neuro-Cognitive Locomotion with Dynamic Attention on Topological Structure

by Azhar Aulia Saputra, János Botzheim and Naoyuki Kubota

Machines 2023, 11(6), 619; https://doi.org/10.3390/machines11060619 - 3 Jun 2023

Cited by 1 | Viewed by 1308

Abstract

This paper discusses a mechanism for integrating locomotion with cognition in robots. We demonstrate an attentional ability model that can dynamically change the focus of its perceptual area by integrating attention and perception to generate behavior. The proposed model considers both internal sensory [...] Read more.

This paper discusses a mechanism for integrating locomotion with cognition in robots. We demonstrate an attentional ability model that can dynamically change the focus of its perceptual area by integrating attention and perception to generate behavior. The proposed model considers both internal sensory information and also external sensory information. We also propose affordance detection that identifies different actions depending on the robot’s immediate possibilities. Attention is represented in a topological structure generated by a growing neural gas that uses 3D point-cloud data. When the robot faces an obstacle, the topological map density increases in the suspected obstacle area. From here, affordance information is processed directly into the behavior pattern generator, which comprises interconnections between motor and internal sensory neurons. The attention model increases the density associated with the suspected obstacle to produce a detailed representation of the obstacle. Then, the robot processes the cognitive information to enact a short-term adaptation to its locomotion by changing its swing pattern or movement plan. To test the effectiveness of the proposed model, it is implemented in a computer simulation and also in a medium-sized, four-legged robot. The experiments validate the advantages in three categories: (1) Development of attention model using topological structure, (2) Integration between attention and affordance in moving behavior, (3) Integration of exteroceptive sensory information to lower-level control of locomotion generator. Full article

(This article belongs to the Special Issue Biorobotic Locomotion and Cybernetic Control)

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23 pages, 13488 KiB

Open AccessEditor’s ChoiceArticle

Lifetime Extension Method for Three-Phase Voltage Source Converters Using Discontinuous PWM Scheme with Hybrid Offset Voltage

by Jaechang Kim, Minh-Hoang Nguyen, Sangshin Kwak and Seungdeog Choi

Machines 2023, 11(6), 612; https://doi.org/10.3390/machines11060612 - 2 Jun 2023

Cited by 6 | Viewed by 2089

Abstract

This paper proposes a lifespan extension technique for three-phase voltage inverters using hybrid offset voltage. The proposed method lengthens the inverter lifetime by independently adjusting the switching frequency of the three phases in accordance with the aging degree. To reduce the switching operation [...] Read more.

This paper proposes a lifespan extension technique for three-phase voltage inverters using hybrid offset voltage. The proposed method lengthens the inverter lifetime by independently adjusting the switching frequency of the three phases in accordance with the aging degree. To reduce the switching operation of the phase with the shortest lifetime, the proposed technique injects the offset voltage for generalized discontinuous pulse-width modulation PWM (GDPWM) into the reference voltage in the region where the switching operation of the shortest lifespan phase can be stopped. When the switching operation does not need to be stopped, the offset voltage for space vector PWM (SVPWM) is injected into the reference voltage for high inverter load current quality. An offset voltage that varies according to the need to stop the switching operation is the proposed hybrid offset voltage. Using the proposed hybrid offset voltage, the switching frequencies of the three phases are independently controllable. In addition, since only the switching operation of the phase having the shortest lifespan is reduced, the load current quality in accordance with the switching operation reduction is good compared to the conventional method to simultaneously diminish all phase switching frequencies. The proposed method significantly increases the reliability of the three-phase voltage inverter, where the thermal stress of the phase having the shortest lifespan is decreased up to 55%, whereas the inverter lifetime can be increased by 10 times. The proposed technique was verified by simulations and experiments. Full article

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

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26 pages, 2973 KiB

Open AccessEditor’s ChoiceArticle

Optimization of Airplane Landing in Crosswind Conditions for Minimum Tire Wear

by Stefano Cacciola, Carlo E. D. Riboldi and Edoardo Generali

Machines 2023, 11(6), 599; https://doi.org/10.3390/machines11060599 - 1 Jun 2023

Viewed by 2088

Abstract

Being one of the most critical phases of a flight, landing deserves specific attention, especially when the aircraft is subject to external disturbances such as wind. A notable concern associated with touchdown events, especially when crosswind is present, is tire wear. This work [...] Read more.

Being one of the most critical phases of a flight, landing deserves specific attention, especially when the aircraft is subject to external disturbances such as wind. A notable concern associated with touchdown events, especially when crosswind is present, is tire wear. This work is aimed first at developing a nonlinear flight simulator able to handle the entire landing maneuver in non-null wind conditions, considering the airborne phase, the ground run, and the transition between them. Then, the simulator is included in an optimal process to define the landing technique associated with the minimum tire wear. The methodology is tested in a simulation environment with a realistic model of a reference aircraft, showing that a significant reduction in tire wear can be obtained by optimizing the sideslip angle at touchdown and the lateral–directional controls after the airplane touches the runway with both legs of the main landing gear. The amount of the reduction is highly variable and depends on the landing conditions, e.g., the velocity and glide path angle. It may range from some percentage points up to 45%. Full article

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

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17 pages, 5975 KiB

Open AccessEditor’s ChoiceArticle

Study on Cage Wear of Railway Traction Motor Bearings Based on Analysis of Rolling Element Motion

by Daisuke Suzuki, Ken Takahashi, Fumihiro Itoigawa and Satoru Maegawa

Machines 2023, 11(6), 594; https://doi.org/10.3390/machines11060594 - 30 May 2023

Cited by 2 | Viewed by 1703

Abstract

Cylindrical roller bearings used in traction motors for railway vehicles are used at high rotational speeds and under light loads. Under these operating conditions, the life due to cage wear is much shorter than the life due to raceway fatigue. Therefore, bearing life [...] Read more.

Cylindrical roller bearings used in traction motors for railway vehicles are used at high rotational speeds and under light loads. Under these operating conditions, the life due to cage wear is much shorter than the life due to raceway fatigue. Therefore, bearing life can be extended by reducing cage wear. The authors thought that to reduce cage wear, it is necessary to establish a dynamic analysis method for the contact between the roller and the cage, and to identify the wear mode of the cage. If cage wear follows Archard’s equation, then cage wear is proportional to the impulse caused by the contact between the rollers and the cage. Therefore, in this paper, a simple model consisting only of a roller and a cage was constructed, and the impulse was obtained via dynamic analysis. The impulses calculated by the dynamic analysis were in good agreement with those measured. In addition, the experiments showed that cage wear is proportional to the impulse and revealed the wear mode of the cage. These allow the method proposed in this paper to be used to predict cage wear and to determine bearing specifications to reduce cage wear. Full article

(This article belongs to the Section Friction and Tribology)

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17 pages, 9826 KiB

Open AccessEditor’s ChoiceArticle

A Study on the Improvement of Power Density of Axial Flux Motors for Collaborative Robot Joints through Same-Direction Skew

by Min-Ki Hong, Hyun-Jo Pyo, Si-Woo Song, Dong-Hoon Jung and Won-Ho Kim

Machines 2023, 11(6), 591; https://doi.org/10.3390/machines11060591 - 26 May 2023

Cited by 3 | Viewed by 3372

Abstract

Axial flux motors have a large output density with a large outer diameter of the motor and a short axial length. Since it is advantageous in short axial length, the axial thickness of motor components becomes a very important parameter when designing axial [...] Read more.

Axial flux motors have a large output density with a large outer diameter of the motor and a short axial length. Since it is advantageous in short axial length, the axial thickness of motor components becomes a very important parameter when designing axial flux motors. Among the components, the back yoke exists to serve as a path for magnetic flux and must have a certain thickness to prevent magnetic saturation. However, as the thickness of the back yoke increases within the axial size limit of the motor, the output of the motor may decrease. In this paper, same-direction skew that increases the cross-sectional area of the magnetic flux path without increasing the thickness of the back yoke is presented. Same-direction skew is a way to increase the cross-sectional area of the back yoke by skewing the rotor and stator in the same direction. The back yoke thickness that can be reduced by same-direction skew was calculated. Performance with same-direction skew designed using the equations was analyzed and compared, and the effectiveness of each type of rotor was verified. The validity of the proposed model was examined using the finite element analysis method. Full article

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

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40 pages, 2691 KiB

Open AccessEditor’s ChoiceReview

Engineering Applications of Artificial Intelligence in Mechanical Design and Optimization

by Jozef Jenis, Jozef Ondriga, Slavomir Hrcek, Frantisek Brumercik, Matus Cuchor and Erik Sadovsky

Machines 2023, 11(6), 577; https://doi.org/10.3390/machines11060577 - 23 May 2023

Cited by 13 | Viewed by 21127

Abstract

This study offers a complete analysis of the use of deep learning or machine learning, as well as precise recommendations on how these methods could be used in the creation of machine components and nodes. The examples in this thesis are intended to [...] Read more.

This study offers a complete analysis of the use of deep learning or machine learning, as well as precise recommendations on how these methods could be used in the creation of machine components and nodes. The examples in this thesis are intended to identify areas in mechanical design and optimization where this technique could be widely applied in the future, benefiting society and advancing the current state of modern mechanical engineering. The review begins with a discussion on the workings of artificial intelligence, machine learning, and deep learning. Different techniques, classifications, and even comparisons of each method are described in detail. The most common programming languages, frameworks, and software used in mechanical engineering for this problem are gradually introduced. Input data formats and the most common datasets that are suitable for the field of machine learning in mechanical design and optimization are also discussed. The second half of the review describes the current use of machine learning in several areas of mechanical design and optimization, using specific examples that have been investigated by researchers from around the world. Further research directions on the use of machine learning and neural networks in the fields of mechanical design and optimization are discussed. Full article

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

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29 pages, 8584 KiB

Open AccessEditor’s ChoiceArticle

Compound Uncertainty Quantification and Aggregation for Reliability Assessment in Industrial Maintenance

by Alex Grenyer, John Ahmet Erkoyuncu, Sri Addepalli and Yifan Zhao

Machines 2023, 11(5), 560; https://doi.org/10.3390/machines11050560 - 16 May 2023

Viewed by 1624

Abstract

The mounting increase in the technological complexity of modern engineering systems requires compound uncertainty quantification, from a quantitative and qualitative perspective. This paper presents a Compound Uncertainty Quantification and Aggregation (CUQA) framework to determine compound outputs along with a determination of the greatest [...] Read more.

The mounting increase in the technological complexity of modern engineering systems requires compound uncertainty quantification, from a quantitative and qualitative perspective. This paper presents a Compound Uncertainty Quantification and Aggregation (CUQA) framework to determine compound outputs along with a determination of the greatest uncertainty contribution via global sensitivity analysis. This was validated in two case studies: a bespoke heat exchanger test rig and a simulated turbofan engine. The results demonstrated the effective measurement of compound uncertainty and the individual impact on system reliability. Further work will derive methods to predict uncertainty in-service and the incorporation of the framework with more complex case studies. Full article

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

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28 pages, 3520 KiB

Open AccessEditor’s ChoiceReview

Bearing Current and Shaft Voltage in Electrical Machines: A Comprehensive Research Review

by Kotb B. Tawfiq, Mehmet Güleç and Peter Sergeant

Machines 2023, 11(5), 550; https://doi.org/10.3390/machines11050550 - 12 May 2023

Cited by 11 | Viewed by 9496

Abstract

The reliability assessment of electric machines plays a very critical role in today’s engineering world. The reliability assessment requires a good understanding of electric motors and their root causes. Electric machines mostly fail due to mechanical problems and bearing damage is the main [...] Read more.

The reliability assessment of electric machines plays a very critical role in today’s engineering world. The reliability assessment requires a good understanding of electric motors and their root causes. Electric machines mostly fail due to mechanical problems and bearing damage is the main source of this. The bearings can be damaged by mechanical, electrical, and thermal stresses. Among all stresses, the researcher should give special attention to the electrical one, which is bearing current and shaft voltage. This review paper introduces a comprehensive study of bearing current and shaft voltage for inverter-fed electric machines. This study aims to discuss several motor failure processes, as well as the sources and definitions of bearing current and shaft voltage. The different kinds of bearing currents are addressed and the parasitic capacitances, which are the key component to describe bearing current, are determined. Several measurement approaches of bearing current will be discussed. Furthermore, modeling of bearing current will be covered together with the machine’s parasitic capacitances. Moreover, the different bearing current mitigation techniques, as described in many papers, will be thoroughly addressed. The use of rewound multiphase machines for mitigation of bearing current will be proposed and compared to a three-phase machine. Finally, various pulse width modulation techniques of multiphase systems that reduce bearing current and shaft voltage will be investigated, and the findings described in the literature will be summarized for all techniques. Full article

(This article belongs to the Special Issue Advanced Power Electronic Technologies in Electric Drive Systems)

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13 pages, 7243 KiB

Open AccessEditor’s ChoiceArticle

Simulative and Experimental Investigation of the Ring Creeping Damage Mechanism Considering the Training Effect in Large-Sized Bearings

by Daniel Billenstein, Martin Neidnicht, Daniel Becker, Christian Liewen, Jörg Rollmann and Bernd Lüneburg

Machines 2023, 11(5), 543; https://doi.org/10.3390/machines11050543 - 11 May 2023

Cited by 1 | Viewed by 2049

Abstract

In this work, an advanced, numerical simulation method based on finite element analyses was developed in order to simultaneously take into account both roller- and structural-induced ring creeping phenomena. Ring creeping in general refers to a failure mode caused by a (non-bolted) bearing [...] Read more.

In this work, an advanced, numerical simulation method based on finite element analyses was developed in order to simultaneously take into account both roller- and structural-induced ring creeping phenomena. Ring creeping in general refers to a failure mode caused by a (non-bolted) bearing ring rotating relatively to its adjacent component such as, e.g., shaft or housing during operation. In particular, the coefficient of friction at the contact interface between bearing ring and adjacent component has a crucial influence. In order to consider this effect, a bearing ring creeping test rig based on component-like specimen was developed. Experimental results with respect to (i) measured creeping parameters such as creeping distance and (ii) the coefficient of friction due to run-in effects were described. Finally, experimental and numerical results were compared qualitatively to approve the reasonableness of the simulation model. The developed simulation approach enables the consideration of the entire drive train system within the micro-scale creeping evaluation procedure and therefore supports both drive train and bearing design-specific optimization measures in order to increase the reliability and robustness of a main bearing arrangement. Full article

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

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17 pages, 408 KiB

Open AccessEditor’s ChoiceReview

Survey on Physiological Computing in Human–Robot Collaboration

by Celal Savur and Ferat Sahin

Machines 2023, 11(5), 536; https://doi.org/10.3390/machines11050536 - 9 May 2023

Cited by 1 | Viewed by 2616

Abstract

Human–robot collaboration has emerged as a prominent research topic in recent years. To enhance collaboration and ensure safety between humans and robots, researchers employ a variety of methods. One such method is physiological computing, which aims to estimate a human’s psycho-physiological state by [...] Read more.

Human–robot collaboration has emerged as a prominent research topic in recent years. To enhance collaboration and ensure safety between humans and robots, researchers employ a variety of methods. One such method is physiological computing, which aims to estimate a human’s psycho-physiological state by measuring various physiological signals such as galvanic skin response (GSR), electrocardiograph (ECG), heart rate variability (HRV), and electroencephalogram (EEG). This information is then used to provide feedback to the robot. In this paper, we present the latest state-of-the-art methods in physiological computing for human–robot collaboration. Our goal is to provide a comprehensive guide for new researchers to understand the commonly used physiological signals, data collection methods, and data labeling techniques. Additionally, we have categorized and tabulated relevant research to further aid in understanding this area of study. Full article

(This article belongs to the Special Issue Control and Mechanical System Engineering)

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18 pages, 3026 KiB

Open AccessEditor’s ChoiceArticle

A 3D Reduced Common Mode Voltage PWM Algorithm for a Five-Phase Six-Leg Inverter

by Markel Fernandez, Endika Robles, Iker Aretxabaleta, Iñigo Kortabarria, Jon Andreu and José Luis Martín

Machines 2023, 11(5), 532; https://doi.org/10.3390/machines11050532 - 6 May 2023

Cited by 3 | Viewed by 1692

Abstract

Neutral point voltage control converters (NPVCC) are being considered for AC drive applications, where their additional degree of freedom can be used for different purposes, such as fault tolerance or common mode voltage (CMV) reduction. For every PWM-driven converter, the CMV is an [...] Read more.

Neutral point voltage control converters (NPVCC) are being considered for AC drive applications, where their additional degree of freedom can be used for different purposes, such as fault tolerance or common mode voltage (CMV) reduction. For every PWM-driven converter, the CMV is an issue that must be considered since it can lead to shaft voltages between rotor and stator windings, generating bearing currents that accelerate bearing degradation, and can also produce a high level of electromagnetic interference (EMI). In light of these considerations, in this paper a three-dimensional reduced common mode voltage PWM (3D RCMV-PWM) technique is proposed which effectively reduces CMV in five-phase six-leg NPVCCs. The mathematical description of both the converter and the modulation technique, in space-vector and carrier-based approaches, is included. Furthermore, the simulation and experimental analysis validate the CMV reduction capability in addition to the good behaviour in terms of the efficiency and harmonic distortion of the proposed RCMV-PWM algorithm. Full article

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

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16 pages, 2211 KiB

Open AccessEditor’s ChoiceArticle

Reconfiguration Analysis and Characteristics of a Novel 8-Link Variable-DOF Planar Mechanism with Five Motion Modes

by Xianwen Kong and Jieyu Wang

Machines 2023, 11(5), 529; https://doi.org/10.3390/machines11050529 - 4 May 2023

Viewed by 1707

Abstract

Variable-DOF (or kinematotropic) mechanisms are a class of reconfigurable mechanisms that have varying degrees of freedom (DOF) in different motion modes and can be reconfigured without disassembly. However, the number of proposed variable-DOF multi-loop planar mechanisms is currently limited. This paper introduces a [...] Read more.

Variable-DOF (or kinematotropic) mechanisms are a class of reconfigurable mechanisms that have varying degrees of freedom (DOF) in different motion modes and can be reconfigured without disassembly. However, the number of proposed variable-DOF multi-loop planar mechanisms is currently limited. This paper introduces a new 8-link variable-DOF planar mechanism that has five motion modes. Firstly, the 8-link variable-DOF planar mechanism is described. Then, reconfiguration analysis of the mechanism is performed using a hybrid approach that combines elimination and computer algebraic geometry methods. The analysis reveals that the 8-link mechanism has one 2-DOF motion mode and four 1-DOF motion modes. It can switch among three motion modes at four transition configurations and between two motion modes at the remaining four transition configurations. The paper also highlights the geometric characteristics of the mechanism in different motion modes. In contrast to variable-DOF planar mechanisms presented in the literature, the proposed 8-link mechanism has two inactive joints in one of its 1-DOF motion modes. Moreover, both closed-loop 4R kinematic sub-chains of the mechanism must appear as either a pair of parallelograms or a pair of anti-parallelograms in the same motion mode. As a by-product of this research, a method for factoring trigonometric functions in two angles is also proposed. Full article

(This article belongs to the Collection Machines, Mechanisms and Robots: Theory and Applications)

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22 pages, 45826 KiB

Open AccessEditor’s ChoiceArticle

Design and Microscale Fabrication of Negative Poisson’s Ratio Lattice Structure Based on Multi-Scale Topology Optimization

by Ran An, Xueyuan Ge and Miaohui Wang

Machines 2023, 11(5), 519; https://doi.org/10.3390/machines11050519 - 1 May 2023

Cited by 3 | Viewed by 2099

Abstract

The current design of negative Poisson’s ratio lattice structures is mainly forward-looking and predominantly dependent on several known deformation patterns. To automate the generation of structures with programmable Poisson’s ratio, the study utilized the energy homogenization method and the Solid Isotropic Material with [...] Read more.

The current design of negative Poisson’s ratio lattice structures is mainly forward-looking and predominantly dependent on several known deformation patterns. To automate the generation of structures with programmable Poisson’s ratio, the study utilized the energy homogenization method and the Solid Isotropic Material with Penalization (SIMP) method to establish an optimization model for negative Poisson’s ratio. By proposing a relaxed objective function and eliminating damping in the Optimality Criteria (OC) method, the study achieves the automatic evolution of negative Poisson’s ratio programmable lattice unit cells, with the lowest Poisson’s ratio achieving −0.5367, and an equivalent elastic matrix is derived. The iterative process’s efficiency is comparable to that of commercial software, with a maximum iteration time of 300 s, enabling the prompt identification of fundamental configurations. To validate the method’s effectiveness, finite element analysis was performed on four tubular structures, revealing evident tension–compression deformation patterns. Moreover, the microscale selective laser melting was used to successfully prepare multiple sets of tubular samples made from 316L stainless steel, each with a height of 5 mm. Quasi-static compression experiments showed negative Poisson’s ratio effects and buckling forms that align with finite element analysis results, providing valuable insights for industry applications. Full article

(This article belongs to the Section Material Processing Technology)

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21 pages, 6492 KiB

Open AccessEditor’s ChoiceArticle

Drivetrain Response Prediction Using AI-Based Surrogate and Multibody Dynamics Model

by Josef Koutsoupakis and Dimitrios Giagopoulos

Machines 2023, 11(5), 514; https://doi.org/10.3390/machines11050514 - 28 Apr 2023

Cited by 2 | Viewed by 1849

Abstract

Numerical models, such as multibody dynamics ones, are broadly used in various engineering applications, either as an integral part of the preliminary design of a product or simply to analyze its behavior. Aiming to increase the accuracy and potential of these models, complex [...] Read more.

Numerical models, such as multibody dynamics ones, are broadly used in various engineering applications, either as an integral part of the preliminary design of a product or simply to analyze its behavior. Aiming to increase the accuracy and potential of these models, complex mechanisms are constantly being added to existing methods of simulation, leading to powerful modelling frameworks that are able to simulate most mechanical systems. This increase in accuracy and flexibility, however, comes at a great computational cost. To mitigate the issue of high computation times, surrogates, such as reduced order models, have traditionally been used as cheaper alternatives, allowing for much faster simulations at the cost of introducing some error to the overall process. More recently, advancements in Artificial Intelligence have also allowed for the introduction of Artificial Intelligence-based models in the field of surrogates. While still undergoing development, these Artificial Intelligence based methodologies seem to be a potentially good alternative to the high-fidelity/burden models. To this end, an Artificial Intelligence-based surrogate comprised of Artificial Neural Networks as a means of predicting the response of dynamic mechanical systems is presented in this work, with application to a non-linear experimental gear drivetrain. The model utilizes Recurrent Neural Networks to accurately capture the system’s response and is shown to yield accurate results, especially in the feature space. This methodology can provide an alternative to the traditional model surrogates and find application in multiple fields such as system optimization or data mining. Full article

(This article belongs to the Special Issue Vibration and Acoustic Analysis of Components and Machines)

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26 pages, 3060 KiB

Open AccessEditor’s ChoiceArticle

Active Fault Diagnosis and Control of a Morphing Multirotor Subject to a Stuck Arm

by Alessandro Baldini, Riccardo Felicetti, Alessandro Freddi and Andrea Monteriù

Machines 2023, 11(5), 511; https://doi.org/10.3390/machines11050511 - 25 Apr 2023

Cited by 1 | Viewed by 1278

Abstract

In this paper, we propose a fault tolerant control law for a morphing quadrotor, where the considered morphing ability is that of extendable/telescopic arms. This quite recent class of systems is able to provide a good trade-off between payload capabilities, maneuverability, and space [...] Read more.

In this paper, we propose a fault tolerant control law for a morphing quadrotor, where the considered morphing ability is that of extendable/telescopic arms. This quite recent class of systems is able to provide a good trade-off between payload capabilities, maneuverability, and space occupancy. However, such degrees of freedom require dedicated servomotors, which in turn implies more possible faults. Thus, the problem of diagnosis for the telescopic servo motors subject to a stuck fault is considered. System symmetries are exploited and used in a residual generator design, which triggers an active fault isolation/identification phase. External disturbances are also taken into account and estimated through a nonlinear disturbance observer. A classical double-loop controller closes the loop, providing an overall control system structure that follows the disturbance observer-based control paradigm. The control scheme is validated through realistic numerical simulations, and the closed-loop performances are analyzed. Full article

(This article belongs to the Special Issue Current and Future Trends in Control and Automation- Selected Papers from the 30th Mediterranean Conference on Control and Automation (MED ’22))

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26 pages, 7342 KiB

Open AccessEditor’s ChoiceArticle

Autonomous Installation of Electrical Spacers on Power Lines Using Magnetic Localization and Special End Effector

by Filip Zorić, Stjepan Flegarić, Goran Vasiljević, Stjepan Bogdan and Zdenko Kovačić

Machines 2023, 11(5), 510; https://doi.org/10.3390/machines11050510 - 24 Apr 2023

Viewed by 3448

Abstract

The combined effects of environmental factors such as high winds and melting ice can cause transmission line conductors to vibrate at high amplitudes, resulting in damaged pole structures, cracked insulating strands, and short circuits. The manual installation of electrical spacers between the two [...] Read more.

The combined effects of environmental factors such as high winds and melting ice can cause transmission line conductors to vibrate at high amplitudes, resulting in damaged pole structures, cracked insulating strands, and short circuits. The manual installation of electrical spacers between the two power line conductors is currently the only way to prevent this, but due to the high-voltage environment, this operation is extremely dangerous for a human worker. As a solution to automate this operation, the autonomous installation of electrical spacers using a robotic manipulator is proposed. For this purpose, a design of a special end effector for the robotic installation of electrical spacers is proposed. The end effector prototype was produced and tested under laboratory conditions and then used for the autonomous installation of spacers on power lines. Its localization with respect to the power lines is based on measurements of the magnetic field generated by the alternating currents flowing through the power lines. To verify the feasibility of the proposed solution under laboratory conditions, the proposed end effector equipped with magnetometers was developed and mounted on a 6-axis Schunk LWA 4p robotic arm. The implemented autonomous installation sequence was successfully verified using a robot and a laboratory mock-up of power lines. Full article

(This article belongs to the Special Issue New Trends in Robotics and Mechatronics Engineering)

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22 pages, 1614 KiB

Open AccessEditor’s ChoiceArticle

Simple Internal Model-Based Robust Control Design for a Non-Minimum Phase Unmanned Aerial Vehicle

by Argyrios Zolotas

Machines 2023, 11(4), 498; https://doi.org/10.3390/machines11040498 - 21 Apr 2023

Cited by 1 | Viewed by 2157

Abstract

Robust control has been successful in enabling flight stability and performance for UAVs. This paper presents a simple explainable robust control design for UAV platforms with non-minimum phase (NMP) zero characteristics in their model. The paper contributes to economic (simple) robust control design [...] Read more.

Robust control has been successful in enabling flight stability and performance for UAVs. This paper presents a simple explainable robust control design for UAV platforms with non-minimum phase (NMP) zero characteristics in their model. The paper contributes to economic (simple) robust control design by addressing the NMP model’s characteristics via Internal Model Control (IMC) and its impact on the UAV pitch response performance. The proposed design is compared with a Parallel Feedback Control Design (PFCD) scheme for the same vehicle platform, for fair comparison. Simulation results illustrate the achievement of the proposed control designs for the UAV platform; only the pitch control is addressed. A by-product of this work is the interpretation of different ways of manipulating the non-minimum phase plant model, so-called ‘modelling for control’, to enable the simple controller design. The work in this paper underpins the simplicity and robustness of the IMC technique for the NMP UAV platform, which further supports the explainability of the control structure relative to performance. Full article

(This article belongs to the Special Issue Dynamics and Control of UAVs)

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16 pages, 9958 KiB

Open AccessEditor’s ChoiceArticle

Deep Learning to Directly Predict Compensation Values of Thermally Induced Volumetric Errors

by Huy Vu Ngoc, J. R. R. Mayer and Elie Bitar-Nehme

Machines 2023, 11(4), 496; https://doi.org/10.3390/machines11040496 - 20 Apr 2023

Cited by 2 | Viewed by 2575

Abstract

The activities of the rotary axes of a five-axis machine tool generate heat causing temperature changes within the machine that contribute to tool center point (TCP) deviations. Real time prediction of these thermally induced volumetric errors (TVEs) at different positions within the workspace [...] Read more.

The activities of the rotary axes of a five-axis machine tool generate heat causing temperature changes within the machine that contribute to tool center point (TCP) deviations. Real time prediction of these thermally induced volumetric errors (TVEs) at different positions within the workspace may be used for their compensation. A Stacked Long Short Term Memories (SLSTMs) model is proposed to find the relationship between the TVEs for different axis command positions and power consumptions of the rotary axes, machine’s linear and rotary axis positions. In addition, a Stacked Gated Recurrent Units (SGRUs) model is also used to predict some cases, which are the best and the worst predictions of SLSTMs to know the abilities of their predictions. Training data come from a long motion activity experiment lasting 132 h (528 measuring cycles). Adaptive moment with decoupled weight decay (AdamW) optimizer is used to strengthen the models and increase the quality of prediction. Multistep ahead prediction in the testing phase is applied to seven positions not used for training in the long activity sequence and 31 positions in a different short activity sequence of the rotary axes lasting a total of 40 h (160 cycles) to test the ability of the trained model. The testing phase with SLSTMs yields fittings between the predicted values and measured data (without using the measured values as targets) from 69.2% to 98.8%. SGRUs show performance similar to SLSTMs with no clear winner. Full article

(This article belongs to the Section Advanced Manufacturing)

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16 pages, 5291 KiB

Open AccessEditor’s ChoiceArticle

Design and Simulation Analysis of Docking Interface of Linked In-Orbit Replacement Module

by Zhuangwei Niu, Jie Zhang, Ning Kong, Jie Ren, Yuan Zhuang, Bo Wang and Runqi Han

Machines 2023, 11(4), 491; https://doi.org/10.3390/machines11040491 - 19 Apr 2023

Cited by 1 | Viewed by 1316

Abstract

On-orbit service for spacecraft relies heavily on on-orbit docking with the orbital replacement unit docking interface. Foreign research on the docking interface of the orbit replaceable unit has been in-depth, while the domestic work is still limited. Currently, most design on the docking [...] Read more.

On-orbit service for spacecraft relies heavily on on-orbit docking with the orbital replacement unit docking interface. Foreign research on the docking interface of the orbit replaceable unit has been in-depth, while the domestic work is still limited. Currently, most design on the docking interface relies on the axial feed of the manipulator, which may result in insufficient docking interface mating force under specific conditions. In view of the above problems, it requires a linear plug-in locking interface for the docking of the orbital replaceable unit, and the design scheme of the tapered rod guide and linkage locking parts needs to be determined. Optimization of the linkage locking mechanism is completed by a finite element simulation. The effect of clearance of the taper rod, effective locking points and friction coefficient have been analyzed by means of dynamics modelling during the docking and locking processes. The research also verified the design rationality for the orbital replaceable unit linkage. A processing path and verification for the prototype have been made as well. This work introduces the idea of self-plugging during the orbital docking process. It lays a foundation for the prototype development and control strategy of the orbital replaceable unit. Full article

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

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28 pages, 12098 KiB

Open AccessEditor’s ChoiceArticle

Methodology for Tool Wear Detection in CNC Machines Based on Fusion Flux Current of Motor and Image Workpieces

by Geovanni Díaz-Saldaña, Roque Alfredo Osornio-Ríos, Israel Zamudio-Ramírez, Irving Armando Cruz-Albarrán, Miguel Trejo-Hernández and Jose Alfonso Antonino-Daviu

Machines 2023, 11(4), 480; https://doi.org/10.3390/machines11040480 - 14 Apr 2023

Cited by 2 | Viewed by 2404

Abstract

In the manufacturing industry, computer numerical control (CNC) machine tools are of great importance since the processes in which they are used allow the creation of elements used in multiple sectors. Likewise, the condition of the cutting tools used is paramount due to [...] Read more.

In the manufacturing industry, computer numerical control (CNC) machine tools are of great importance since the processes in which they are used allow the creation of elements used in multiple sectors. Likewise, the condition of the cutting tools used is paramount due to the effect they have on the process and the quality of the supplies produced. For decades, methodologies have been developed that employ various signals and sensors for wear detection, prediction and monitoring; however, this field is constantly evolving, with new technologies and methods that have allowed the development of non-invasive, efficient and robust systems. This paper proposes the use of magnetic stray flux and motor current signals from a CNC lathe and the analysis of images of machined parts for wear detection using online and offline information under the variation in cutting speed and tool feed rate. The information obtained is processed through statistical and non-statistical indicators and dimensionally reduced by linear discriminant analysis (LDA) and a feed-forward neural network (FFNN) for wear classification. The results obtained show a good performance in wear detection using the individual signals, achieving efficiencies of 77.5%, 73% and 89.78% for the analysis of images, current and stray flux signals, respectively, under the variation in cutting speed, and 76.34%, 73% and 63.12% for the analysis of images, current and stray flux signals, respectively, under the variation of feed rate. Significant improvements were observed when the signals are fused, increasing the efficiency up to 95% for the cutting speed variations and 82.84% for the feed rate variations, achieving a system that allows detecting the wear present in the tools according to the needs of the process (online/offline) under different machining parameters. Full article

(This article belongs to the Section Advanced Manufacturing)

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21 pages, 2495 KiB

Open AccessEditor’s ChoiceArticle

Deep PCA-Based Incipient Fault Diagnosis and Diagnosability Analysis of High-Speed Railway Traction System via FNR Enhancement

by Yunkai Wu, Xiangqian Liu and Yang Zhou

Machines 2023, 11(4), 475; https://doi.org/10.3390/machines11040475 - 13 Apr 2023

Cited by 14 | Viewed by 2225

Abstract

In recent years, the data-driven based FDD (Fault Detection and Diagnosis) of high-speed train electric traction systems has made rapid progress, as the safe operation of traction system is closely related to the reliability and stability of high-speed trains. The internal complexity and [...] Read more.

In recent years, the data-driven based FDD (Fault Detection and Diagnosis) of high-speed train electric traction systems has made rapid progress, as the safe operation of traction system is closely related to the reliability and stability of high-speed trains. The internal complexity and external complexity of the environment mean that fault diagnosis of high-speed train traction system faces great challenges. In this paper, a wavelet transform-based FNR (Fault to Noise Ratio) enhancement is realised to highlight incipient fault information and a Deep PCA (Principal Component Analysis)-based diagnosability analysis framework is proposed. First, a scheme for FNR enhancement-based fault data preprocessing with selection of the intelligent decomposition levels and optimal noise threshold is proposed. Second, fault information enhancement technology based on continuous wavelet transform is proposed from the perspective of energy. Further, a Deep-PCA based incipient fault detectability and isolatability analysis are provided via geometric descriptions. Finally, experiments on the TDCS-FIB (Traction Drive Control System–Fault Injection Benchmark) platform fully demonstrate the effectiveness of the method proposed in this paper. Full article

(This article belongs to the Special Issue Advanced Data Analytics in Intelligent Industry: Theory and Practice)

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30 pages, 2725 KiB

Open AccessEditor’s ChoiceReview

Railways Passengers Comfort Evaluation through Motion Parameters: A Systematic Review

by Patricia Silva, Diogo Ribeiro, Joaquim Mendes, Eurico Augusto Rodrigues Seabra and Octavian Postolache

Machines 2023, 11(4), 465; https://doi.org/10.3390/machines11040465 - 8 Apr 2023

Cited by 2 | Viewed by 2175

Abstract

Railways are one of the most widely used mass transportation systems. Its superior transportation capacity, low environmental impact, high safety, and comfort have been leading to a continuous increase in passengers. To keep this trend going, it is crucial to improve the railways’ [...] Read more.

Railways are one of the most widely used mass transportation systems. Its superior transportation capacity, low environmental impact, high safety, and comfort have been leading to a continuous increase in passengers. To keep this trend going, it is crucial to improve the railways’ attractiveness and comfort levels. A rail journey’s comfort performance is rather complex, involving the analysis of multiple factors. Those raised by the vehicle motion and seat performance are the focus of vehicle designers’ concerns. Therefore, only a combination of static and dynamic comfort methodologies can accurately characterize passengers’ comfort. This work aimed to perform a systematic review concerning the comfort evaluation of train passengers. The bibliographic search yielded 62 studies on static and dynamic comfort evaluation methods. Results show a lack of experiments conducted on real rail environments, leading to weak conclusions regarding the real in-service conditions that train users face. Moreover, an investigation gap concerning the simultaneous application of both static and dynamic methodologies was observed. Therefore, more investigations are needed to evaluate and increase passengers’ comfort and promote rail usage as a daily transportation system. Full article

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19 pages, 7409 KiB

Open AccessEditor’s ChoiceArticle

Field Evaluation of Piezoelectric Energy Harvesters on Bridge Structure

by Lukai Guo, Hao Wang, John Braley and Giri Venkiteela

Machines 2023, 11(4), 462; https://doi.org/10.3390/machines11040462 - 7 Apr 2023

Cited by 3 | Viewed by 1908

Abstract

This study aims to develop and evaluate vibration-based piezoelectric energy harvesters for generating power from a bridge structure. New designs of multiple-degree-of-freedom (DOF) cantilevers were proposed and evaluated in a laboratory and on a full-scale bridge. It was found that all cantilever designs [...] Read more.

This study aims to develop and evaluate vibration-based piezoelectric energy harvesters for generating power from a bridge structure. New designs of multiple-degree-of-freedom (DOF) cantilevers were proposed and evaluated in a laboratory and on a full-scale bridge. It was found that all cantilever designs showed potential of generating 35 V voltage outputs under a simple sinusoidal vibration scenario in the laboratory. Field testing results showed that the match between the vibration frequencies of bridge structure and the resonant frequencies of cantilevers significantly affected the voltage output from the piezoelectric energy harvester under moving tire loads. Through adding more DOF on the same cantilever, the voltage attenuation from peaks generated by the cantilever turned to be less significant after each load passing, leading to greater energy outputs in some cases. With adjusting the mass combination in the 3-DOF cantilever design, the voltage output and energy production reached 11.1 V and 58.2 μJ under one single loading pulse, respectively, which was higher than 9.2 V and 14.9 μJ obtained from the best scenario of 1-DOF cantilevers. The study findings indicate the potential of developing multi-band piezoelectric energy harvesters for harvesting energy from bridge vibrations. Full article

(This article belongs to the Special Issue Applications of Piezoelectric Devices and Materials)

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30 pages, 6546 KiB

Open AccessEditor’s ChoiceReview

State of the Art in Wearable Wrist Exoskeletons Part I: Background Needs and Design Requirements

by Roberto Francesco Pitzalis, Daegeun Park, Darwin G. Caldwell, Giovanni Berselli and Jesús Ortiz

Machines 2023, 11(4), 458; https://doi.org/10.3390/machines11040458 - 4 Apr 2023

Cited by 4 | Viewed by 3931

Abstract

Despite an increase in the use of exoskeletons, particularly for medical and occupational applications, few studies have focused on the wrist, even though it is the fourth most common site of musculoskeletal pain in the upper limb. The first part of this paper [...] Read more.

Despite an increase in the use of exoskeletons, particularly for medical and occupational applications, few studies have focused on the wrist, even though it is the fourth most common site of musculoskeletal pain in the upper limb. The first part of this paper will present the key challenges to be addressed to implement wrist exoskeletons as wearable devices for novel rehabilitation practices and tools in the occupational/industrial sector. Since the wrist is one of the most complex joints in the body, an understanding of the bio-mechanics and musculo-skeletal disorders of the wrist is essential to extracting design requirements. Depending on the application, each wrist exoskeleton has certain specific design requirements. These requirements have been categorized into six sections: purpose, kinematics, dynamics, rigidity, ergonomics, and safety. These form the driving factors behind the choice of a design depending on the objectives. Different design architectures are explored, forming the basis for the various technical challenges that relate to: actuation type, power source, power transmission, sensing, and control architecture. This paper summarizes, in a systematic approach, all the current technologies adopted, analyzes their benefits and limitations, and finally proposes future perspectives. Full article

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

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17 pages, 8821 KiB

Open AccessEditor’s ChoiceArticle

Robust Control for the Hybrid Energy System of an Electric Loader

by Yuchuan Ma, Qiao Wang, Min Ye and Gaoqi Lian

Machines 2023, 11(4), 454; https://doi.org/10.3390/machines11040454 - 4 Apr 2023

Cited by 3 | Viewed by 1573

Abstract

With the wide application of electric vehicles and the development of battery technology, pure electric construction machinery (PECM) has received more and more attention due to its high efficiency and no pollution. The working conditions of construction machinery are complex and accompanied by [...] Read more.

With the wide application of electric vehicles and the development of battery technology, pure electric construction machinery (PECM) has received more and more attention due to its high efficiency and no pollution. The working conditions of construction machinery are complex and accompanied by periodical working conditions and heavy load. For electric construction machinery, a heavy load represents an energy supply with a large current. To adapt to the working conditions of PECM, this paper proposes a robust controller to regulate the current of the hybrid energy system (HES) which include the battery and supercapacitor. The V-type operating conditions of a 5-ton pure electric loader are the research focus to analyze the working principles of the HES. The topology and energy flow patterns of the HES are proposed and analyzed. The model of the battery, supercapacitor, and DC/DC converter are depicted, and the robust control method is designed. An electric loader experiment platform is created to verify the effectiveness of the robust control method. Compared with the proportional integral control effect, the experiment results show that the proposed control method had good control performance and could better regulate the current. It can be used as a reference value for other dual energy source PECM. Full article

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

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19 pages, 2897 KiB

Open AccessEditor’s ChoiceArticle

Cloud-Empowered Data-Centric Paradigm for Smart Manufacturing

by Sourabh Dani, Akhlaqur Rahman, Jiong Jin and Ambarish Kulkarni

Machines 2023, 11(4), 451; https://doi.org/10.3390/machines11040451 - 3 Apr 2023

Cited by 4 | Viewed by 1748

Abstract

In the manufacturing industry, there are claims about a novel system or paradigm to overcome current data interpretation challenges. Anecdotally, these studies have not been completely practical in real-world applications (e.g., data analytics). This article focuses on smart manufacturing (SM), proposed to address [...] Read more.

In the manufacturing industry, there are claims about a novel system or paradigm to overcome current data interpretation challenges. Anecdotally, these studies have not been completely practical in real-world applications (e.g., data analytics). This article focuses on smart manufacturing (SM), proposed to address the inconsistencies within manufacturing that are often caused by reasons such as: (i) data realization using a general algorithm, (ii) no accurate methods to overcome the actual inconsistencies using anomaly detection modules, or (iii) real-time availability of insights of the data to change or adapt to the new challenges. A real-world case study on mattress protector manufacturing is used to prove the methods of data mining with the deployment of the isolation forest (IF)-based machine learning (ML) algorithm on a cloud scenario to address the inconsistencies stated above. The novel outcome of these studies was establishing efficient methods to enable efficient data analysis. Full article

(This article belongs to the Special Issue Industry 5.0 and Digital Practices in Multidisciplinary Applications)

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36 pages, 10046 KiB

Open AccessEditor’s ChoiceReview

A Review on the Design and Application of Compliant Mechanism-Based Fast-Tool Servos for Ultraprecision Machining

by Vinodth Paniselvam, Nicholas Yew Jin Tan and Senthil Kumar Anantharajan

Machines 2023, 11(4), 450; https://doi.org/10.3390/machines11040450 - 3 Apr 2023

Cited by 4 | Viewed by 3380

Abstract

The compliant mechanism (CM)-based fast-tool servo (FTS) is used in ultraprecision machining contexts to produce high value products for technically advanced applications. Far too often, the FTS’ machined products are expected to be geometrically complex with minimal form tolerance and surface roughness. Since [...] Read more.

The compliant mechanism (CM)-based fast-tool servo (FTS) is used in ultraprecision machining contexts to produce high value products for technically advanced applications. Far too often, the FTS’ machined products are expected to be geometrically complex with minimal form tolerance and surface roughness. Since the FTS’ enclosing CM is responsible for guiding the cutting motion, its design is of utmost importance in determining the quality of the machined product. The objective of this paper is therefore to review specifically the design and structural related aspects of CM-based FTS that affects its ultraprecision machining performance. After a brief introduction, the fundamentals for designing ultraprecision capable CMs such as flexure hinge modelling, actuator selection and isolation and CM designing are comprehensively explained. In the subsequent section, the various configurations of CM-based FTSs that exist so far and their functionalities are listed. The critical factors which impact the CM-based FTS’ ultraprecision machining performance are identified and mitigating measures are provided wherever possible. Before concluding, the research questions that should be investigated for raising the state of the art of CM-based FTSs are presented as food for thought. With this review article, not only can practitioners have a clearer picture of how better to design their CMs for their FTSs, but they can also improve upon existing FTS designs from leading researchers so that products of higher quality than before can be made for the future. Full article

(This article belongs to the Section Advanced Manufacturing)

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20 pages, 6492 KiB

Open AccessEditor’s ChoiceArticle

Development of Pneumatic Force-Controlled Actuator for Automatic Robot Polishing Complex Curved Plexiglass Parts

by Xinyu Zhang and Yuwen Sun

Machines 2023, 11(4), 446; https://doi.org/10.3390/machines11040446 - 1 Apr 2023

Cited by 3 | Viewed by 2692

Abstract

Due to the temperature-sensitive characteristic of plexiglass materials, it is necessary to maintain a constant small contact force to avoid surface burn damage when polishing complex curved plexiglass parts. To handle the issue, in this paper a pneumatic force-controlled actuator was developed to [...] Read more.

Due to the temperature-sensitive characteristic of plexiglass materials, it is necessary to maintain a constant small contact force to avoid surface burn damage when polishing complex curved plexiglass parts. To handle the issue, in this paper a pneumatic force-controlled actuator was developed to keep the normal contact force between the polishing tool and the workpiece constant during the robotic polishing process. The force-controlled actuator is configured with a double-acting cylinder as the driving element, and two electrical proportional valves are used to control the output force by adjusting the pressure difference between the two air chambers of the cylinder. In this case, a small contact force can be exactly achieved, and the cylinder can always work within the optimal pressure range. In order to judge the stability of the system and reduce the commissioning time of the force-controlled actuator, a mathematical model of the force-controlled actuator is established. Meanwhile, for eliminating the influence of the gravity of the polishing tool on the contact force control, a gravity compensation algorithm is also given according to the roll-pitch-yaw (RPY) angle calculation method. Since there are some nonlinear factors in the operation of the force-controlled actuator, a fuzzy proportion-integral-derivative (PID) control strategy is adopted without steady-state errors. Finally, the polishing experiment of a complex curved plexiglass part was carried out by using the robot automatic polishing system. The experimental results show that the contact force control effect of the force-controlled actuator meets the processing requirements, and the curved plexiglass part has good surface quality and optical performance after polishing. Full article

(This article belongs to the Special Issue Recent Progress of Thin Wall Machining)

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20 pages, 4120 KiB

Open AccessEditor’s ChoiceArticle

An Indirect Procedure for Real-Time Monitoring the Neutral Conductor Deterioration in Three-Phase Distribution Networks

by Vicente León-Martínez, Joaquín Montañana-Romeu, Elisa Peñalvo-López, Amparo León-Vinet and Jorge Cano-Martínez

Machines 2023, 11(4), 444; https://doi.org/10.3390/machines11040444 - 1 Apr 2023

Viewed by 1304

Abstract

An indirect procedure for real-time monitoring the neutral conductor condition in three-phase distribution networks, based on watching over the growth of a novel parameter (∆τ), has been described in this paper. The parameter ∆τ has been defined as the relationship [...] Read more.

An indirect procedure for real-time monitoring the neutral conductor condition in three-phase distribution networks, based on watching over the growth of a novel parameter (∆τ), has been described in this paper. The parameter ∆τ has been defined as the relationship between the neutral-displacement power and Buchholz’s apparent power measured at the fundamental frequency in the loads of the distribution networks for any condition of the neutral conductor and in its nominal conditions. The effectiveness of this procedure has been compared with other traditional indirect procedures, such as the surveillance of the RMS values of the line-to-neutral load voltages or their zero-sequence component. The practical application on a real distribution network reveals that the growth of the parameter ∆τ in the early stages of the breaking process of the neutral conductor follows a straight line whose equation is known for each length and section of that conductor, regardless of the loads and the voltage regulation of the transformer of the distribution network. This characteristic of the ∆τ parameter shows that the proposed procedure is suitable for monitoring neutral conductor deterioration and can be used for preventive maintenance of distribution networks. Full article

(This article belongs to the Special Issue Application of Deep Learning in Fault Diagnosis)

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21 pages, 10018 KiB

Open AccessEditor’s ChoiceArticle

Development and Testing of a Self-Propelled Machine for Combined Potato Harvesting and Residual Plastic Film Retrieval

by Yuanjin Ju, Wei Sun, Zhiwei Zhao, Hucun Wang, Xiaolong Liu, Hua Zhang, Hui Li and Petru Aurelian Simionescu

Machines 2023, 11(4), 432; https://doi.org/10.3390/machines11040432 - 28 Mar 2023

Cited by 6 | Viewed by 2715

Abstract

A self-propelled machine for combined potato harvesting and residual plastic film retrieval is presented in this paper. The machine was designed collaboratively and built at the College of Mechano-Electronic Engineering of Gansu Agricultural University. It is intended for slow slope and horizontal terraces [...] Read more.

A self-propelled machine for combined potato harvesting and residual plastic film retrieval is presented in this paper. The machine was designed collaboratively and built at the College of Mechano-Electronic Engineering of Gansu Agricultural University. It is intended for slow slope and horizontal terraces in hilly and mountainous areas of Northwest China, where regular-size harvesters cannot operate. The machine can realize the combined operations of potato digging, potato separation from soil and plastic film, potato collection and bagging, and residual plastic film retrieval. Through engineering analyses, the main systems of the machine were calculated, and their operating parameters were estimated. These include the digging and lifting device, the potato–plastic-film separation device, and the residual plastic film retrieval device. Field tests were performed at a 0.5 m/s driving speed of the machine, while the linear speed of the lifting chain of the digging and lifting device was 1.5 m/s, the tilting angle of the conveying chain of the potato and plastic film separation device was 50°, its linear speed was 0.6 m/s, and the linear speed of the lifting screen of the circulating lifting device was 0.7 m/s. With these settings, the average productivity of the machine was 0.12 ha/h. The loss rate, damage rate, and potato bruising rate were 1.8%, 1.4%, and 2.8%, respectively; the potato impurity rate was 3.6%; and the residual plastic film retrieval rate was 83%—all above industry standards. This research provides a solution to the problem of mechanized potato harvesting and plastic mulch retrieval on small, slopped plots of land in Northwest China and in other parts of the world where similar conditions exist. Full article

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

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