Actuators, Volume 11, Issue 12 (December 2022) – 42 articles

Increasing heat flux restricts the development of the miniaturization of electronic devices. There is an urgent need for a heat dissipation method that will efficiently cool the chip. This paper presents a novel liquid cooling device based on dual synthetic jets actuator (DSJA) technology. The characteristics of the temperature and velocity field of the device are numerically studied by a three-dimensional coupled heat transfer model. The entropy generation rate caused by heat transfer and fluid friction was studied to analyze the effective work loss and irreversibility of the heat transfer process. When the DSJA is turned on, the temperature of the heat source with a heat flux of 200 W/cm² is 73.07 ${}^{\circ }$C, and the maximum velocity is 24.32 m/s. Compared with the condition when the the DSJA is closed, the temperature decreases by 25.15 ${}^{\circ }$C, and the velocity increases by nearly 20 m/s. At this time, the total inlet flow is 1.26 L/min. The larger frictional entropy generation is mainly distributed near the inlet and outlet of the channel and the jet orifice. The higher the velocity is, the more obvious the frictional entropy generation is. Due to the large temperature gradient, there is a large thermal entropy generation rate at the fluid–solid interface. Full article

For an electro-hydrostatic actuator (EHA), the position, speed, and current cascade three-loop control architecture are dominant in existing active disturbance rejection control (ADRC). However, this architecture suffers from many problems, such as severe noise sensitivity of the extended state observer (ESO), excessive complexity of control structure, and too many tuned parameters, which makes the controller not easy to implement in practice. Aiming at the above drawbacks, a novel cascade double-loop ADRC strategy that is automatic current-constrained is proposed, which makes the whole ADRC architecture simplified to the position and the integrated speed–current double-loop architecture. Firstly, for the position control loop, the singular perturbation theory is used to reasonably reduce the order of the model for the position subsystem of EHA. A reduced order ADRC controller (ROADRC) is synthesized, which not only effectively reduces the noise sensitivity of ESO, but also circumvents use of the actuation acceleration information in the controller design process. Secondly, the integrated speed–current ADRC controller is designed by taking the speed and current subsystems of EHA into synthesis, which avoids the problem of excessive current loop bandwidth in conventional three-loop control architecture, and the number of tuned parameters is significantly reduced. Additionally, an uncomplicated and effective automatic current-constrained ADRC controller (CACADRC) is designed to solve the problem in the integrated speed–current ADRC that the current cannot be automatically constrained. Finally, by comparing the three-loop PI controller with the traditional three-loop ADRC, a detailed simulation analysis is carried out to verify the effectiveness and merits of the proposed controller. The simulation results show that the proposed controller not only inherits the advantages of high precision and strong disturbance rejection performance of the conventional ADRC, but can also efficiently decrease the noise sensitivity of ESO and effectively achieve the current-constrained control. Full article

Nanoparticles with small diameters and large surface areas have potential advantages and are actively utilized in various fields related to biomedical and catalytic applications. Multifunctional applications can be achieved by endowing nanoparticles with piezoelectric, quantum dot, magnetothermal, and piezoluminescent properties. In particular, multiferroic magnetoelectric nanoparticles (MENPs) can generate electricity by coupling piezoelectric and magnetostrictive properties when an external magnetic field, which is harmless to the human body, is applied. In this regard, magnetoelectricity (ME) induced by a magnetic field makes MENPs useful for various biomedical and electrocatalytic applications. The ME voltage coefficients, which express the efficiency of energy conversion from magnetic field to electricity, show differences depending on the setup for ME measurements of MENPs. Therefore, numerous attempts have been made to optimize the ME characterization method to reduce measurement errors resulting from charge leakages caused by the specimen preparation, as well as to investigate the ME effect of a single nanoparticle. Our review is focused on the structures, syntheses (hydrothermal and sol–gel methods), activation mechanism, and measurement of magnetoelectricity, as well as applications, of core–shell MENPs. Full article

A high-end permanent magnet (PM) synchronous motor’s cogging torque is a significant performance measure (PMSM). During the running of the motor, excessive cogging torque will amplify noise and vibration. Therefore, the cogging torque must be taken into account while optimizing the design of motors with precise motion control. In this research, we proposed a local optimization-seeking approach (RSM+NSGA-II-LR) based on Response Surface Methodology (RSM) and Non-Dominated Sorting Genetic Algorithm-II (NSGA-II), which reduced the cogging torque of a permanent magnet synchronous motor (SPMSM). To reduce the complexity of optimization and increase its efficiency, the sensitivity analysis method was utilized to identify the structural parameters that had a significant impact on the torque performance. Second, RSM was utilized to fit the functional relationship between the structural parameters and each optimization objective, and NSGA-II was integrated to provide the Pareto solution for each optimization objective. The solution with a greater average torque than the initial motor and the lowest cogging torque was chosen, and a new finite element model (FEM) was created. On the basis of the sensitivity analysis, the structural factors that had the highest influence on the cogging torque were selected, and the RSM is utilized for local optimization to lower the cogging torque as much as feasible. The numerical results demonstrated that the optimization strategy presented in this study effectively reduced the cogging torque of the motor without diminishing the motor’s average torque or increasing its torque ripple. Full article

The selection of an appropriate method for modeling vehicle dynamics heavily depends on the application. Due to the absence of human intervention, the demand for an accurate and real-time model of vehicle dynamics for intelligent control increases for autonomous vehicles. This paper develops a multibody vehicle model for longitudinal-vertical dynamics applicable to advanced driver assistance (ADAS) applications. The dynamic properties of the chassis, suspension, and tires are considered and modeled, which results in accurate vehicle dynamics and states. Unlike the vehicle dynamics models built into commercial software packages, such as ADAMS and CarSim, the proposed nonlinear dynamics model poses the equations of motion using a subset of relative coordinates. Therefore, the real-time simulation is conducted to improve riding performance and transportation safety. First, a vehicle system is modeled using a semi-recursive multibody dynamics formulation, and the vehicle kinematics and dynamics are accurately calculated using the system tree-topology. Second, a fork-arm removal technique based on the rod-removal technique is proposed to reduce the number of bodies, relative coordinates, and equations constrained by loop-closure. This increase the computational efficiency even further. Third, the dynamic simulations of the vehicle are performed on bumpy and sloping roads. The accuracy and efficiency of the numerical results are compared to the reference data. The comparative results demonstrate that the proposed vehicle model is effective. This efficient model can be utilized for the intelligent control of vehicle ADAS applications, such as forward collision avoidance, adaptive cruise control, and platooning. Full article

In this article, an electromagnetic actuator is proposed to improve the driving performance of magnetic levitation transportation applied to ultra-clean manufacturing. The electromagnetic actuator mainly includes the stator with the Halbach array and the mover with a symmetrical structure. First, the actuator principle and structure are illustrated. Afterward, in order to select a suitable secondary structure and analyze the characteristics of the actuator, the electromagnetic characteristics of actuators with different secondary structures are analyzed by the finite element method (FEM). Analysis results show that the actuator adopting the secondary structure with a Halbach array will increase the electromagnetic force and working stability. The secondary with the three-section Halbach array is selected for the electromagnetic actuator. Then, the influence of secondary permanent magnet (PM) thickness on the electromagnetic force is analyzed by FEM. The results indicate that the increase in PM thickness will lead to increased electromagnetic force and decreased utilization ratio of PM. Finally, a prototype of an electromagnetic actuator is built, and experiments are implemented. The correctness of the theoretical analysis and the effectiveness of the electromagnetic actuator are verified by experimental results. Full article

In order to understand the impingement flow field and cooling characteristics of vectoring dual synthetic jets (DSJ), an experimental investigation was performed to analyze the parameter effects. With the variation of the slot location, the vectoring angle of DSJ can be adjusted from 34.5° toward the left to 29.5° toward the right. The vectoring function can greatly extend the length of impingement region. There are three local peaks both for the local cooling performance (Nu) and the whole cooling performance (Nu_avg). Although the peak Nu at a certain location of the slider is higher than that at the center, the corresponding Nu_avg is lower. As for different driving frequencies, the vectoring angle reaches its minimum of 9.7° at 350 Hz, but the Nu is obviously improved. There is one local peak of Nu_avg values at 350 Hz rather than three local peaks at 250 Hz and 450 Hz. The slot locations where the Nu_avg of 250 Hz and 450 Hz reach maximum are different. With the increase in driving voltage from ±100 V to ±200 V, the vectoring angle drops from 46.9° to 22.2°, but both Nu and Nu_avg are improved. The maximum Nu_avg of each driving voltage occurs at the center location of the slider. The choking effect and the cross flow have dominated the vectoring angle and the cooling performance of impingement DSJ. Vectoring DSJ will give impetus to the thermal management of large-area electric devices in spaced-constrained cooling and removing dynamic hotspots. Full article

Recently, the fourth industrial revolution has accelerated the application of multiple degrees-of-freedom (DOF) robot arms in various applications. However, it is difficult to utilize robot arms for precision motion control because of their low stiffness. External loads applied to robot arms induce deflections in the joints and links, which deteriorates the positioning accuracy. To solve this problem, control methods using a disturbance observer (DOB) with an external sensory system have been developed. However, external sensors are expensive and have low reliability because of noise and reliance on the surrounding environment. A disturbance-observer-based dual-position feedback (DOB-DPF) controller is proposed herein to improve the positioning accuracy by compensating for the deflections in real time using only an internal sensor. The DOB was designed to derive the unpredictable disturbance torque applied to each joint using the command voltage generated by the position controller. The angular deflection of each joint was calculated based on the disturbance torque and joint stiffness, which were identified experimentally. The DPF controller was designed to control the joint motor while simultaneously compensating for angular deflection. A five-DOF robot arm testbed with a position controller was constructed to verify the proposed controller. The contouring performance of the DOB-DPF controller was compared with that of a conventional position controller with an external load applied to the end effector. The increases in the root mean square values of the contour errors were 1.71 and 0.12 mm with a conventional position controller and the proposed DOB-DPF controller, respectively, after a 2.2 kg weight was applied to the end effector. The results show that the contour error caused by the external load is effectively compensated for by the DOB-DPF controller without an external sensor. Full article

Attitude control of a novel regional truss-braced wing (TBW) aircraft with low stability characteristics is addressed in this paper using Reinforcement Learning (RL). In recent years, RL has been increasingly employed in challenging applications, particularly, autonomous flight control. However, a significant predicament confronting discrete RL algorithms is the dimension limitation of the state-action table and difficulties in defining the elements of the RL environment. To address these issues, in this paper, a detailed mathematical model of the mentioned aircraft is first developed to shape an RL environment. Subsequently, Q-learning, the most prevalent discrete RL algorithm, will be implemented in both the Markov Decision Process (MDP) and Partially Observable Markov Decision Process (POMDP) frameworks to control the longitudinal mode of the proposed aircraft. In order to eliminate residual fluctuations that are a consequence of discrete action selection, and simultaneously track variable pitch angles, a Fuzzy Action Assignment (FAA) method is proposed to generate continuous control commands using the trained optimal Q-table. Accordingly, it will be proved that by defining a comprehensive reward function based on dynamic behavior considerations, along with observing all crucial states (equivalent to satisfying the Markov Property), the air vehicle would be capable of tracking the desired attitude in the presence of different uncertain dynamics including measurement noises, atmospheric disturbances, actuator faults, and model uncertainties where the performance of the introduced control system surpasses a well-tuned Proportional–Integral–Derivative (PID) controller. Full article

In this paper, an adaptive incremental neural network (INN) fixed-time tracking control scheme based on composite learning is investigated for robot systems under input saturation. Firstly, by integrating the composite learning method into the INN to cope with the inevitable dynamic uncertainty, a novel adaptive updating law of NN weights is designed, which does not need to satisfy the stringent persistent excitation (PE) conditions. In addition, for the saturated input, differing from adding the auxiliary system, this paper introduces a hyperbolic tangent function to deal with the saturation nonlinearity by converting the asymmetric input constraints into the symmetric ones. Moreover, the fixed-time control approach and Lyapunov theory are combined to ensure that all the signals of the robot closed-loop control systems converge to a small neighborhood of the origin in a fixed time. Finally, numerical simulation results verify the effectiveness of the fixed-time control and composite learning algorithm. Full article

In recent decades, the demand for rail transport has been growing steadily and faces a double problem. Not only must the transport capacity be increased, but also a more flexible service is needed to meet the real demand. Both objectives can be achieved through virtual coupling (VC), which is an evolution of the current moving block systems. Trains under VC can run much closer together, forming what is called a virtually coupled train set (VCTS). In this paper, we propose an approach in which virtual coupling is implemented via model predictive control (MPC). For this purpose, we define a robust controller that can predict, based on a dynamic model of the train, the state of the system at later moments of time and make the appropriate control decisions. A robust MPC (RMPC) is obtained by introducing two uncertain variables. The first uncertain variable is added to the acceleration equation of the dynamic model, while the second uncertain variable is used to define the uncertainty in the train positioning. To test the RMPC for virtual coupling, two simulation cases are performed for a metro line, analysing the influence of both the uncertainties. In all cases, the results obtained show a safer operation of the virtual coupling without significantly affecting the service. Full article

Electrical discharge machining (EDM) is not limited to the strength and hardness of conductive materials, and is a non-contact special processing technology. In micro-EDM, there are problems such as untimely axial positioning, unstable inter-electrode machining voltage, and difficulty in discharging inter-electrode electric erosion products. This paper considers a magnetic actuator with fast response and high accuracy as the local actuator for a micro-EDM. By introducing a domain adjustment mechanism, a variable domain fuzzy PID controller was designed to control the inter-electrode voltage control system of the magnetic actuator for micro-EDM using an intelligent control strategy. During the micro-EDM machining process, the controlled magnetic actuator drives the tool electrode in the axial direction for rapid micro-positioning, thus maintaining effective inter-electrode machining voltage and achieving a high-speed and high precision EDM. Simulation and experimental results showed that compared with traditional micro-EDM, the machining efficiency of the variable domain fuzzy PID control magnetic actuator, and traditional micro-EDM cooperative control, was increased by 40%, the machining process was more stable, and the quality of the machined surface was better. Full article

The start-up process of a centrifugal pump as turbine (PAT) under gas–liquid two-phase conditions was simulated based on Fluent, and the evolution mechanism of the internal flow field and the variation law of force characteristics were studied in its start-up process under gas–liquid two-phase conditions. The results show that the area with high gas phase concentration corresponds to a strong vortex at the beginning of the start-up. The vortex intensity in the impeller gradually decreases with an increase in rotational speed. The gas volume fraction of the blade suction surface is more significant than that of the blade pressure surface. The higher the inlet gas volume fraction (IGVF) is, the more severely the blade load will fluctuate during the start-up process. As the rotational speed increases, the fluctuation of the blade load gradually weakens, and the maximum load is distributed near the inner edge of the blade after the rotational speed is stable. The periodic unbalanced radial force is produced in the start-up process. From the pure liquid conditions to the gas–liquid two-phase conditions with increasing IGVF, the dominant frequency amplitude of radial force shows a similar trend of decreasing first but then increasing. After the rotational speed tends to be stable, the dominant frequency of radial force is equal to the rotational frequency of the blade. With the increase in rotational speed, the dominant frequency amplitude of axial force decreases gradually. The higher the IGVF, the greater the dominant frequency amplitude of axial force at the same time. Full article

In lower-limb rehabilitation systems, exoskeleton robots are one of the most important components. These robots help patients to execute repetitive exercises under the guidance of physiotherapists. Recently, pneumatic artificial muscles (PAM), a kind of actuator that acts similarly to human muscles, have been chosen to power the exoskeleton robot for better human–machine interaction. In order to enhance the performance of a PAM-based exoskeleton robot, this article implements an active disturbance rejection control (ADRC) strategy with a nonlinear extended state observer (NLESO). Moreover, the stability of the closed-loop system is proved by Lyapunov’s theory. Finally, the experimental results show that with the proposed control strategy, the rehabilitation robot can effectively track the desired trajectories even when under external disturbance. Full article

This paper establishes a matrix displacement model and an improved dynamic model for the static and dynamic performances analysis for a kind of bridge-type displacement amplification mechanism with distributed-compliance, which has better performances than traditional lumped-compliance bridge-type mechanisms. In the matrix displacement model, the stiffness matrix for two rigid bodies connected by flexures is first obtained by regarding the displacements and the forces on two mass centers of the rigid bodies as the node displacements and node forces. By extending and superimposing each elemental stiffness matrix, the global stiffness matrix for the flexure mechanism can be obtained to calculate the displacement amplification ratio and input stiffness of the bridge-type mechanism. In the improved dynamic model, in order to establish the Lagrangian dynamic model more accurately, the deflectional, axial, and rotational velocities of any point on the beam flexure are calculated by solving the derivatives of the deformation curves of beam flexures versus time to obtain the expression of the kinetic energy in the vibrating beams. On this basis, the three-degree-of-freedom vibration differential equation for the bridge-type mechanism is established by using the Lagrange method, and the natural frequency in the working direction is obtained accurately. The presented models are compared with the finite element analysis, and experiments for two case studies of the bridge-type distributed-compliance mechanism are presented. The comparisons results demonstrate the high prediction accuracy of the improved dynamic model. Full article

Cable-Driven Parallel Robots (CDPRs) are special manipulators where rigid links are replaced with cables. The use of cables offers several advantages over the conventional rigid manipulators, one of the most interesting being their ability to cover large workspaces since cables are easily winded. However, this workspace coverage has its limitations due to the maximum permissible cable tensions, i.e., tension limitations cause a decrease in the Wrench Feasible Workspace (WFW) of these robots. To solve this issue, a novel design based in the addition of passive carriages to the robot frame of three degrees-of-freedom (3DOF) fully-constrained CDPRs is used. The novelty of the design allows reducing the variation in the cable directions and forces increasing the robot WFW; nevertheless, it presents a low stiffness along the x direction. This paper presents the dynamic model of the novel proposal together with a new dynamic control technique, which rejects the vibrations caused by the stiffness loss while ensuring an accurate trajectory tracking. The simulation results show that the controlled system presents a larger WFW than the conventional scheme of the CDPR, maintaining a good performance in the trajectory tracking of the end-effector. The novel proposal presented here can be applied in multiple planar applications. Full article

This paper proposes a model-based systems engineering (MBSE) methodology to design a first-stage separation system for a launch vehicle. It focuses on the whole process of system modeling, such as modeling the requirements analysis, logical architecture design, physical architecture design, and system verification and validation. Finally, the component requirements are obtained as the baseline for the component design. Requirements analysis is carried out by identifying stakeholders with the cycle modeling for this system and the use of case modeling to ensure that the requirements are comprehensive and correct. Additionally, the standard system requirements are obtained and baselined. Based on system requirements, the trade-off analysis of hierarchical functional architecture and key indicators was mainly carried out to design the logical architecture. Once the logical architecture was decided, the logical architecture was allocated to the physical architecture to be implemented. Several physical architectures are analyzed hierarchically to seek the optimal architectures. Then, other CAE analysis tools were integrated to verify the physical architecture design. All these processes are modeled and integrated as the authority system model, which benefits the system engineer for managing the requirement changes easier and rapidly provides multi-views for different roles. Full article

With the development of engineering materials, as well as the growing requirements for weight reduction and the reduction of energy consumption by mechanical systems, attempts have been made to utilize composite materials in the design of hydraulic cylinders. In many cases, the reduction in the weight of the actuators may lead to a reduction in the values of bending moments acting on the booms of working machines, as well as leading to a reduction in the power demand in drive systems. The use of composite materials can also increase the reliability of cylinders in corrosive environments and places with strong electromagnetic fields. This paper presents the development of hydraulic actuators made of composite materials, presenting both the achievements of research centers and commercial companies. The main research and engineering problems are presented along with the methods of solving them resulting from the literature available. The directions for further research that should be undertaken in order to increase reliability, improve efficiency, and reduce weight are also outlined. Full article

The primary goal of this study is to create a magnetic levitation system for additive manufacturing (AM) applications. The emphasis of this research is placed on Laser Directed Energy Deposition via Powder Feeding (LDED-PF). The primary benefit of using a magnetic levitation system for AM applications is that the levitated geometry is expected to be a portion of the final part manufactured, thus eliminating the need for a substrate and reducing the post-processing operation requirement. Two novel levitation systems were designed, optimized, and manufactured. The design, optimization, and analysis were first conducted in the simulation environment using ANSYS Maxwell and then tested with experiments. The newly developed systems depicted a much-improved performance compared to the first prototype developed in a previous article written by the authors. The newly developed systems had an increase in levitation height, the surface area for powder deposition activities, the time available for AM operations, and the ability to support additional mass within the limits of allowable inputs. The compatibility of the levitation system with AM applications was also verified by testing the impact of powder deposition and the ability of the levitated disc to support added mass as a function of time with minimal loss in performance. This article also highlights the development of a novel feedback PID controller for the levitation system. To improve the overall performance of the controller, a feedforward controller was added in conjunction with the PID controller. Finally, the levitation system was shown to highlight control over levitation height and maintain constant levitation height with the addition of an added mass using the feedback controller. Full article

The advantages of the proposed dual-mode magnetic suspension are it having a high level of safety and a compact structure compared with the previous studies. However, the structure parameters can affect the energy harvesting of the suspension system. Therefore, this paper aims to analyze the energy-harvesting characteristics of the proposed dual-mode magnetic suspension. Firstly, the structure and working principle of the proposed suspension are introduced. Then, the influences of the various parameters for the actuator on the energy regeneration characteristics are analyzed by the finite element method, such as the magnetic ring, the fixed plug thickness, the heat dissipation, and the air gap, and the actuator parameters are defined by the orthogonal analysis method. Furthermore, the numerical results of the energy harvesting are calculated. Finally, the vibration experimental setup is manufactured, and the simulation analysis is verified by the experiment. The results demonstrate that the excitation amplitude is 3.1 mm, the frequency is 18 Hz, and the maximum induced EMF is 8.8 V. Additionally, compared with passive suspension, the energy harvesting of the proposed suspension has been verified in the laboratory, which lays the foundation for the design and analysis of the dual-mode magnetic suspension in a real vehicle. Full article

To analyze the multidimensional elastic–plastic response of the frame structure with magnetorheological (MR) dampers under strong seismic excitations, the test of the MRD was performed, the location matrix of the MRD in the frame structure was derived, and the multidimensional elastic–plastic calculation models of the frame structure with and without an MRD were established based on the three-segment variable stiffness beam. Taking a five-story reinforced concrete (RC) frame structure as an example, the multidimensional elastic–plastic calculation models were developed by MATLAB software and the dynamic time history analyses were performed under strong seismic excitations. The results show that under the seismic wave, after the MRD is installed in the structure, the maximum horizontal displacements of the top-story node of the structure in X and Y directions is reduced by 51.87% and 39.59%, respectively, and the maximum horizontal accelerations are reduced by 36.67% and 47.86%. The maximum displacements and the story drift ratios of each story of the structure are significantly reduced, and the reduction in the maximum accelerations of each story is small relatively. In the frame structure without an MRD, plastic hinges appear at the ends of most columns, and the structure is characterized by a column hinge yield mechanism. The maximum residual displacement angles of the column end in X and Y directions which reach 1.628 × 10⁻³ rad and 2.101 × 10⁻³ rad, respectively. After setting the MRD, the number of plastic hinges in X and Y directions at the column end are both reduced by 37.5%, and the residual displacement angle at some column ends are reduced to 0. The results show that the complied calculation model programs of the frame structure can effectively simulate the multi-dimensional seismic response of the structure with and without MRD. Full article

Aiming at the efficiency and precision in micro electrical discharge machining (micro-EDM) is affected because the interpole voltage is unstable in conventional micro-EDM. This paper describes a five-degrees-of-freedom (5-DOF) controlled, wide-bandwidth, and high-precision magnetic levitation actuator. The conventional micro-EDM can install the actuator to maintain a stable interpole voltage between the electrode and workpiece to realize the high-speed micro-EDM. In this paper, the structure of the magnetic levitation actuator is designed, and the magnetic field characteristics are analyzed. On this basis, an integrator and regulator are used along with a controller with local current feedback to eliminate steady-state errors, stabilize the control system, and improve the bandwidth and positioning accuracy of the magnetic levitation actuator, and the dynamic performance of the actuator is evaluated. The experimental results show that the developed actuator has excellent positioning performance with micron-level positioning accuracy to meet the demand for the real-time, rapid, and accurate adjustment of the interpole gap during micro-EDM. Full article

This paper presents the design and implementation of a flexible manipulator formed of connected continuum kinematic modules (CKMs) to ease the fabrication of a continuum robot with multiple degrees of freedom. The CKM consists of five sequentially arranged circular plates, four universal joints intermediately connecting five circular plates, three individual actuated tension cables, and compression springs surrounding the tension cables. The base and movable circular plates are used to connect the robot platform or the neighboring CKM. All tension cables are controlled via linear actuators at a distal site. To demonstrate the function and feasibility of the proposed CKM, the kinematics of the continuum manipulator were verified through a kinematic simulation at different end velocities. The correctness of the manipulator posture was confirmed through the kinematic simulation. Then, a continuum robot formed with three CKMs is fabricated to perform Jacobian-based image servo tracking tasks. For the eye-to-hand (ETH) experiment, a heart shape trajectory was tracked to verify the precision of the kinematics, which achieved an endpoint error of 4.03 in Root Mean Square Error (RMSE). For the eye-in-hand (EIH) plugging-in/unplugging experiment, the accuracy of the image servo tracking system was demonstrated in extensive tolerance conditions, with processing times as low as $58\pm 2.12$ s and $83\pm 6.87$ s at the 90% confidence level in unplugging and plugging-in tasks, respectively. Finally, quantitative tracking error analyses are provided to evaluate the overall performance. Full article

The increase in emissions associated with aviation requires deeper research into novel sensing and flow-control strategies to obtain improved aerodynamic performances. In this context, data-driven methods are suitable for exploring new approaches to control the flow and develop more efficient strategies. Deep artificial neural networks (ANNs) used together with reinforcement learning, i.e., deep reinforcement learning (DRL), are receiving more attention due to their capabilities of controlling complex problems in multiple areas. In particular, these techniques have been recently used to solve problems related to flow control. In this work, an ANN trained through a DRL agent, coupled with the numerical solver Alya, is used to perform active flow control. The Tensorforce library was used to apply DRL to the simulated flow. Two-dimensional simulations of the flow around a cylinder were conducted and an active control based on two jets located on the walls of the cylinder was considered. By gathering information from the flow surrounding the cylinder, the ANN agent is able to learn through proximal policy optimization (PPO) effective control strategies for the jets, leading to a significant drag reduction. Furthermore, the agent needs to account for the coupled effects of the friction- and pressure-drag components, as well as the interaction between the two boundary layers on both sides of the cylinder and the wake. In the present work, a Reynolds number range beyond those previously considered was studied and compared with results obtained using classical flow-control methods. Significantly different forms of nature in the control strategies were identified by the DRL as the Reynolds number $Re$ increased. On the one hand, for $Re\le 1000$, the classical control strategy based on an opposition control relative to the wake oscillation was obtained. On the other hand, for $Re=2000$, the new strategy consisted of energization of the boundary layers and the separation area, which modulated the flow separation and reduced the drag in a fashion similar to that of the drag crisis, through a high-frequency actuation. A cross-application of agents was performed for a flow at $Re=2000$, obtaining similar results in terms of the drag reduction with the agents trained at $Re=1000$ and 2000. The fact that two different strategies yielded the same performance made us question whether this Reynolds number regime ($Re=2000$) belongs to a transition towards a nature-different flow, which would only admits a high-frequency actuation strategy to obtain the drag reduction. At the same time, this finding allows for the application of ANNs trained at lower Reynolds numbers, but are comparable in nature, saving computational resources. Full article

The agricultural sector is constantly evolving. The rise in the world’s population generates an increasingly growing demand for food, resulting in the need for the agroindustry to meet this demand. Tractors are the vehicles that have made a real difference in agriculture’s development throughout history, lowering costs in soil tillage and facilitating activities and operations for workers. This study aims to successfully design and build an autonomous, electric agricultural tractor that can autonomously perform recurring tasks in open-field and greenhouse applications. This project is fully part of the new industrial and agronomic revolution, known as Factory 4.0 and Agriculture 4.0. The predetermined functional requirements for the vehicle are its lightweight, accessible price, the easy availability of its spare parts, and its simple, ordinary maintenance. In this first study, the preliminary phases of sizing and conceptual design of the rover are reported before subsequently proceeding to the dynamical analysis. To optimize the design of the various versions of the automated vehicle, it is decided that a standard chassis would be built based on a robot operating inside a greenhouse on soft and flat terrains. The SimScape multi-body environment is used to model the kinematics of the non-back-drivable screw jack mechanism for the hitch-lifting arms. The control unit for the force exerted is designed and analyzed by means of an inverse dynamics simulation to evaluate the force and electric power consumed by the actuators. The results obtained from the analysis are essential for the final design of the autonomous electric tractor. Full article

This study designs and implements a wheeled bipedal robot (WBR) that combines the mobility of wheeled robots and the dexterity of legged robots. The designed WBR has extra knee joints to maintain body balance when encountering uneven terrain. Because of the robot’s highly nonlinear, dynamic, unstable, and under-actuated nature, an intelligent motion and balance controller (IMBC) based on a fuzzy logic approach is proposed to maintain the balance of the WBR while it is standing and moving on the ground. It should be emphasized that the proposed IMBC system does not require prior knowledge of system dynamics and the controller parameters are tuned using the qualitative aspects of human knowledge. Furthermore, a 32-bit microcontroller that has memory, programmable I/O peripherals, and a processor core is used to implement the IMBC method. Finally, moving and rotating, height-changing, posture-keeping, and “one leg on slope” movement scenarios are tested to demonstrate the feasibility of the proposed IMBC system. The experimental results show that, by using the proposed IMBC system, the WBR can not only balance and move well both on flat ground and in complex terrain but also extend each leg independently to maintain body balance. Full article

This paper presents two nonlinear model predictive control (MPC) methods for the integrated propulsion and cabin-cooling management of electric vehicles. An air-conditioning (AC) model, which has previously been validated on a real system, is used to accomplish system-level optimization. To investigate the optimal solution for the integrated optimal control problem (OCP), we first build an MPC, referred to as a joint MPC, in which the goal is to minimize battery energy consumption while maintaining cabin-cooling comfort. Second, we divide the integrated OCP into two small-scale problems and devise a co-optimization MPC (co-MPC), where speed planning on hilly roads and cabin-cooling management with propulsion power information are addressed successively. Our proposed MPC methods are then validated through two case studies. The results show that both the joint MPC and co-MPC can produce significant energy benefits while maintaining driving and thermal comfort. Compared to regular constant-speed cruise control that is equipped with a proportion integral (PI)-based AC controller, the benefits to the battery energy earned by the joint MPC and co-MPC range from 2.09% to 2.72%. Furthermore, compared with the joint MPC, the co-MPC method can achieve comparable performance in energy consumption and temperature regulation but with reduced computation time. Full article

This paper investigates secure control of Networked Inverted Pendulum Visual Servo Systems (NIPVSSs) based on Active Disturbance Rejection Control (ADRC). Firstly, considering the network- and image-induced delays in conjuction with computational errors caused by image processing and image attacks, the model of NIPVSSs is established. Secondly, the limitations of the traditional Single-Input-Single-Output (SISO) ADRC used in NIPVSSs with disturbance are revealed. The limitations are that the ESO used in the traditional SISO ADRC brings large steady-state error, and the NLSEF used in the traditional SISO ADRC can achieve stable control of pendulum angle, but cannot achieve stable control of cart position. Thirdly, a new Single-Input-Multi-Output (SIMO) ADRC method is proposed for NIPVSSs with disturbance. In the new SIMO ADRC method, the new ESO is designed by introducing additional first and second derivatives of error to reduce the steady-state error. In addition, the new NLSEF is developed by taking both the calculated cart position and pendulum angle as inputs to achieve dual stable control of pendulum angle and cart position. Finally, combined with the designed ADRC parameter-tuning strategy, the results from simulation and real-world experiments confirm the effectiveness and feasibility of the proposed method. Full article

The car suspension setting is always a trade-off between comfort and handling. The semi-active damper system seems to be an option for reducing the compromise between the two demands. This paper deals with the effect of the magnetorheological damper setting on a car’s suspension performance, especially tire grip, which was directly measured. A unique test rig was developed, and an experimental trolley with a fast magnetorheological damper (response time of 3 µs) was used in the paper. The damper was controlled by a modified Groundhook algorithm. Compared with the passive regime, the experiments showed a 30% improvement when using the Groundhook algorithm and when the damper was adequately set. The experiments proved the trends that were set by simulations. Full article

This paper presents a fault tolerant scheme employing adaptive non-singular fixed-time terminal sliding mode control (AFxNTSM) for the application of robotic manipulators under uncertainties, external disturbances, and actuator faults. To begin, non-singular fixed-time terminal sliding mode control (FxNTSM) is put forth. This control method uses non-singular terminal sliding mode control to quickly reach fixed-time convergence, accomplish satisfactory performance in tracking, and produce non-singular and non-chatter control inputs. Then, without knowing the upper bounds beforehand, AFxNTSM is used as a reliable fault tolerant control (FTC) to estimate actuator faults and unknown dynamics. The fixed-time stability of the closed-loop system is established by the theory of Lyapunov analysis. The computer simulation results of the position tracking, control inputs, and adaptive parameters are presented to verify and illustrate the performance of the proposed strategy. Full article