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In recent years, virtual coupling (VC) has been becoming a hot research topic in railways. The coordinative control for the virtually coupled train set (VCTS) is a critical technology for realising VC. In this paper, distributed adaptive coordinative control of the VCTS with considering parametric uncertainty and practical constraints is studied. To begin with, a third-order nonlinear VCTS train-following model is formulated by considering the uncertain resistance in the railway external environment and the actuator delay in the traction/braking system of unit trains. After that, a novel barrier functions-based third-order sliding mode control method is proposed to realise all states tracking control as well as to satisfy the state constraints (i.e. spacing and speed constraints). Adaptive control technology is used to alleviate the parametric uncertainty. Furthermore, by combining these techniques, a novel distributed adaptive coordinative control strategy is designed to not only guarantee the stable operation of the VCTS but also effectively handle parametric uncertainty and state constraints. Finally, the effectiveness of the proposed method is validated in simulation analysis. [ABSTRACT FROM AUTHOR]

In this paper, the mathematical model of the aviation pressure servo valve controlled actuator system(APSVCAS) considering nonlinearity is established based on a jet pipe pressure servo valve in this article. And the dynamic characteristics and stability boundary of APSVCAS are analyzed, which provides theoretical guidance for the actual composition and the determination of parameters. Firstly, a jet-tube two-stage pressure servo valve for aviation hydraulic system is designed, and an accurate model of APSVCAS is established considering multiple nonlinear factors. Meantime, the influence of 34 parameters on the dynamic characteristics of the system is analyzed by using the second-order sensitivity analysis method. And the key parameters that significantly affect the dynamic characteristics of the system are extracted. Based on this, the system stability discrimination method is proposed from the perspectives of frequency domain and time domain, and the stability boundary of key parameters is obtained. Finally, the theoretical analysis results are verified on the experimental platform of APSVCAS. The experimental results show that the mathematical model of APSVCAS considering nonlinearity has satisfactory accuracy. Concomitantly, it is verified that the parameters' stability boundary condition based on the sensitivity analysis method meet the stable output effect of the system under multiple working conditions. [ABSTRACT FROM AUTHOR]

Exosuits for the lower limb have developed rapidly as an affordable, light, and more cost-effective alternative to the bulkier, traditional exoskeletons. The synergy-based approach aims at further emphasizing such advantages, providing even lighter and cheaper solutions, thanks to its reduction in actuators and the subsequent simplification of the actuation unit. In this paper, a design approach based on dynamic synergies is proposed to reduce the number of required actuators, thus decreasing the price and weight of walking-assistance exosuits. Also, in this work, we propose a methodology to calculate motor torque output and cable forces during assisted gait. Mechanical designs for the actuation unit are proposed along with experimental and computer-based testing and simulation. Lastly, actuation units with one and two motors are studied and compared, regarding control, mechanical complexity, and metabolic cost reduction. The results show that dynamic synergies can indeed contribute to the design of these assistive devices, with its own set of advantages and disadvantages when compared to the previously proposed postural synergies: while the latter led to a higher cumulative variance of the first principal component and the transmission system is simpler, control may be more unpredictable and forces upon the system, harder to estimate. With dynamic synergies, more related to muscle synergies, metabolic benefit on users may be more significant. [ABSTRACT FROM AUTHOR]

Hydraulic motion platforms are widely utilized in various environments due to their capacity to bear heavy loads and provide long actuator strokes. The predominant control system employed for hydraulic motion platforms is the electro-hydraulic servo system (EHSS) due to its high accuracy and robustness. However, compared to other types of hydraulic valves, the electro-hydraulic servo valve (EHSV) is less durable. An alternative system to EHSS is the electro-hydraulic proportional system (EHPS), which employs an electro-hydraulic proportional valve (EHPV) instead of the EHSV. The EHPV resolves the durability issue at the expense of accuracy and system error. The optimization of durability and accuracy is the core of this study. The tracking behavior and response of both Three degrees of freedom (3 DOF) motion platforms using EHSS and EHPS are investigated across different frequency ranges. [ABSTRACT FROM AUTHOR]

The relevance of research aimed at developing diagnostic technologies for electromechanical actuators is due to the need to improve flight safety in conditions of increasing intensity of highly electrified aircraft and spacecraft operations. The paper discusses one of the promising approaches to electromechanical actuator health management, which involves the use of machine learning methods to synthesize health monitoring algorithms. Machine learning methods make it possible to build classification models based on empirical data, which are used to generate recommendations for making operational decisions. Empirical data, which is a source of valuable experience and the basis of a training sample necessary for formalizing patterns in classification models, can be formed as a result of life tests, mathematical modeling, and actuator operation. In order to improve the safety of space flights, the article focuses on the integration of electromechanical actuator mathematical model methods, optimal space filling, and machine learning. Optimal space filling methods are used to reduce the computational costs associated with representative training sampling. Examples of developing classification models are given to determine failures associated with changes in gear (backlash, Coulomb friction and viscous friction) which is the most critical actuator link. As a result of computational studies, the main advantages of the proposed approach to the synthesis of electromechanical actuator health assessment algorithms are shown. • Health monitoring algorithms of electromechanical actuators to improve space flight safety. • Integration of mathematical models for electromechanical actuators, optimal space filling, and machine learning. • Development and verification of classification models to determine failures associated with changes in backlash, Coulomb friction and viscous friction. [ABSTRACT FROM AUTHOR]

This paper examines fault-tolerant quantized control for neural networks under persistent dwell-time switching, considering the presence of actuator faults and dynamic output quantization. The dynamic scaling factor (DSF) of the quantizer is designed as a piecewise function concerning the output to avoid the possibility of division by zero. To reduce conservatism, the controller is designed to combine the system model with a time scheduler constructed with a minimum time span. A sufficient condition for the asymptotic stability and L2-gain of the closed-loop system is derived using a piecewise Lyapunov functional and decoupling approach. When the condition is satisfied, the needed feedback gains and the parameter range associated with the DSF can be determined by exact mathematical expressions. For comparison, feedback gains that depend only on the system mode are also studied, and the corresponding design method is presented. The numerical simulation results demonstrate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Performance evaluation of avionics software in conjunction with flight hardware is a critical process carried out using a specialized Hardware-In-Loop Simulation (HILS) platform. This platform integrates essential flight subsystems, such as actuators and navigation systems, to validate their performance under real-time conditions. A unique facility, the Flight Motion Simulator (FMS), plays a vital role in testing the dynamic behavior of navigation systems. However, challenges arise due to the physical separation of critical equipment like the FMS and actuator setups from the main HILS Test-bed, necessitating their integration across large distances. To address this, a remote simulation Test-bed has been designed and developed utilising the emerging MIL-STD 1773 protocol with fiber optics-based communication. This approach ensures real-time data transfer with minimal latency, preserving the high-performance requirements of HILS. The Fiber Optics Data Acquisition System (FODAS) facilitates seamless integration of remote flight subsystems with the HILS Test-bed, eliminating delays associated with relocating equipment and re-establishing setups. Additionally, it enables the connection of flight subsystems directly from integration hangers, enhancing testing efficiency and flexibility. This research outlines the design and development methodology of the MIL-STD 1773-based FODAS system integrated with the HILS Test-bed. It further provides performance analysis, advantages, and practical results from its implementation, demonstrating the system's capability to overcome existing limitations while improving operational efficiency. [ABSTRACT FROM AUTHOR]

Sensor faults can contaminate system measurements such that reliable estimation cannot be achieved and further cause abnormalities in multiagent systems (MASs). Addressing this problem, this study develops an event-triggered fault-tolerant tracking control (FTTC) protocol. The descriptor approach is first used to construct extended states and eliminate sensor faults from the measurement equation. A sliding-mode observer is then tailored based on the transformed system to realize state estimation and fault diagnosis (FD) simultaneously. Subsequently, an event-triggered distributed estimator is developed to isolate the uncertainty's influence and reduce communication overhead while estimating the leader's state. By incorporating the estimator and observer outputs, an FTTC protocol is developed to ensure stability under actuator/sensor faults. Finally, the investigated FTTC method is validated with a numerical simulation of multiple quadrotors. • The descriptor approach is utilized to cope with the actuator/sensor faults. • A sliding mode-based observer is used to diagnose concurrent actuator/sensor faults. • An estimator isolates the impact of uncertainties to estimate the leader's state. • Distributed fault-tolerant tracking control is achieved. • An event-triggered technique is adopted to reduce communication overhead. [ABSTRACT FROM AUTHOR]

The steering system plays a critical role in the vehicle's handling and directly influences its lateral dynamics. Faults or abnormal behavior in this system can affect performance, cause vehicle instability, and even lead to accidents. Therefore, considering these potential events is essential for designing robust controllers for autonomous vehicles. For this reason, in this work, a fault-tolerant path-tracking Static Output-Feedback controller is designed to handle steering actuator faults in autonomous vehicle steering systems. The controller adopts a Linear Parameter Varying approach to effectively handle nonlinearities associated with varying vehicle speeds and tire behavior. Furthermore, it only uses information from sensors, avoiding estimation stages. This controller can operate in two modes: a no-fault mode where only the steering is controlled to follow the reference path and a fault mode where the controller manages both the steering and torque vectoring. In fault mode, torque vectoring compensates for faults in the steering actuator. The design of the controller is completed considering gain faults in the steering system. The simulation results show that the proposed controller successfully maintains vehicle stability and significantly reduces tracking errors during high-risk maneuvers, achieving reductions of up to 50.65% in lateral error and 47.26% in heading error under worst-case fault scenarios. [ABSTRACT FROM AUTHOR]

A global prescribed performance control method is proposed for a class of uncertain high-order odd-rational-power nonlinear systems (a chain of integrators whose power is the ratio of odd integers) with actuator faults, where the high-order odd-rational powers and the parameters of actuator faults are unknown. A new coordinate transformation on the state and tracking errors is introduced based on the tangent function and its inverse function, resulting in a global low-complexity prescribed performance controller. The proposed controller does not require any knowledge of system nonlinearities or powers, and it also does not require the time derivatives of virtual control signals without using any filters, which implies the controller is of low complexity. Finally, two simulation examples, including a practical high-maneuver flight control example, are given to demonstrate the effectiveness of our method. [ABSTRACT FROM AUTHOR]

The current shafting alignment process primarily relies on manual adjustments, resulting in low efficiency and limited precision. This study designs an automatic alignment system for multi-support shafting to improve alignment efficiency and accuracy, advancing the development of intelligent systems. The overall design of the automatic alignment system is proposed, including the establishment of shafting and actuator models. The alignment performance of two control strategies under different shafting deviations is validated through simulations. The results indicate that both the full-state feedback control strategy and the model predictive control strategy can regulate bearing load errors to within 1%. Compared to manual alignment, both strategies demonstrate significantly higher efficiency. The proposed automatic alignment system is feasible and lays a foundation for the development of high-precision shafting alignment systems. [ABSTRACT FROM AUTHOR]

In this paper, a two-DOF L-shaped yoke spherical actuator based on the principle of traditional voice coil actuators is developed. By utilizing the shape characteristics of the yoke and the magnetization direction of the magnet, the magnetic flux is concentrated and the magnet is shared, thereby improving the performance of the actuator. In the design process, SOLIDWORKS 2018 software is used for design modeling and assembly simulation, ANSYS Maxwell 2018 software is employed for magnetic circuit analysis and electromagnetic simulation, while MATLAB is utilized for analyzing the dynamic characteristics through a mathematical model. A prototype was also fabricated, and torque measurement experiments were conducted to verify the performance and feasibility of the proposed design. [ABSTRACT FROM AUTHOR]

To address the issues of limited adaptability and low spatial utilization in traditional rigid actuators, a biomimetic actuator with water-induced helical deformation functionality was designed. This actuator is capable of adaptive gripping and retrieval of objects in a narrow lumen. A numerical model was established to analyze its helical deformation mechanism, and the helical deformation characteristics of the actuator were calculated under different structural parameters. Based on four-dimensional (4D) printing technology, which integrates three-dimensional printed structures with responsive materials, experimental samples of biomimetic actuators were fabricated by combining thermoplastic polyurethane fiber scaffolds with water-absorbing polyurethane rubbers. By comparing the simulation results with the experimental data, the numerical model was corrected, providing theoretical guidance for the structural optimization design of the actuator. The experiment shows that the biomimetic actuator can act as a gripper to capture a small target in a lumen less than 5 mm in diameter. This research provides a theoretical and technical foundation for the development of specialized actuators aimed at narrow spaces. [ABSTRACT FROM AUTHOR]

Dielectric elastomer actuators (DEAs) are difficult to apply to flexible grippers due to their small deformation range and low output force. Hence, a DEA with a large bending deformation range and output force was designed, and a corresponding flexible gripper was developed to realize the function of grasping objects of different shapes. The relationship between the pre-stretch ratio and DEA deformation degree was tested by experiments. Based on the performance test results of the dielectric elastomer (DE), the bending deformation process of DEAs with different shapes was simulated by Finite Element Method (FEM) simulation. DEAs with different shapes were prepared through laser cutting and the relationship between the voltage and the bending angle, and the output force of the DEAs was measured. The result shows that under uniaxial stretching, the deformation of the DEA in the stretching direction gradually increases and decreases in the unstretched direction with the increase in the pre-stretch ratio. Under biaxial stretching, DEA deformation increases with the increase in the pre-stretch ratio. The shape of the DEA has a certain influence on the bending deformation range under the same conditions, and the elliptical DEA has a larger bending deformation range and higher output force compared with the rectangular DEA and the trapezium DEA. The elliptical DEA can produce a bending deformation of 40° and an output force of 37.2 mN at a voltage of 24 kV. The three-finger flexible gripper composed of an elliptical DEA can realize the grasping of a paper cup. [ABSTRACT FROM AUTHOR]

To simplify the grasping mechanism of drones, this paper presents a dual-function landing gear with an actively closing mechanism, designed for coaxial drones. The proposed design integrates self-locking and clutch mechanisms, enabling the landing gear to be actuated by a single motor. This novel approach eliminates the need for additional actuators, optimizing the drone's takeoff, landing, and grasping capabilities while reducing energy consumption compared to traditional designs. Kinematic and static analyses, along with experimental evaluations, were conducted to assess the grasping performance of the mechanism. Experimental results demonstrate that the landing gear can close within 0.2 s and provide a grasping force exceeding 10 N. Compared to conventional designs, this solution offers a reliable and energy-efficient approach for dual-function drone operations. [ABSTRACT FROM AUTHOR]

Continuously rotating gimbals for scanning purposes are widely used in space applications. For high-precision gimbals, it is essential to lock the gimbal before launch and unlock it on orbit. This kind of gimbal puts forward the need for hold down release mechanisms that are able to clear the gap between the rotating and fixed parts at release. Existing technologies either lack the function of gap avoidance after separation or rely more or less on the elastic deformation of the structure or limited spring forces for unlocking, which are either unreliable or complicated. To address this problem, this paper presents the design of a novel non-pyrotechnic heavy-load hold down release mechanism (HDRM) based on shape memory alloy actuator. The proposed HDRM is shock-free and capable of clearing an axial gap of 8 mm for safe rotating at release. The structure and operational principle of the proposed design are straightforward. Detailed tests show the proposed HDRM may withstand a maximum external force of 50 KN with relatively high stiffness under 15 KN of preload, indicating a better performance than existing products. The HDRM demonstrates its promising usage as an alternative to traditional pyrotechnic and non-pyrotechnic HDRMs. [ABSTRACT FROM AUTHOR]

In this proposed work, two prototypes are implemented, one is for smart parking and the other is for monitoring the energy consumption of the same. With the implementation of IoT based Street Light System in the field, nearly 60-70 percent of electricity saving can be achieved as compared to conventional systems. Here, this system is not only controlling the switching of the street lights ON/OFF but these electricity consumption details can be monitored remotely through another developed prototype. It is demonstrated that for a single pole electricity consumption is nearly 1.2KW load per pole which results in power consumption of 14.4KWh from evening 6:00 PM to morning 6:00AM with conventional system. The implemented system is energy efficient in terms of energy saving which is nearly 9.6KWh can be achieved per day on each pole with same specifications. Moreover, real-time implementation of the proposed system is also demonstrated. IoT is a key technology in healthcare sector for managing, monitoring and controlling the medical devices, services and processes with the basic sensing and actuating components. [ABSTRACT FROM AUTHOR]

This study delves into an event-triggered hierarchical learning control framework for air-breathing hypersonic vehicles subject to practically constrained actuators. The hierarchical learning mechanism is adeptly integrated into both the control and allocation layers. In the control layer, an emotional deterministic learning control methodology is proposed with predefined-time disturbance observers and filters to attain predefined-time convergence of system tracking and learning, while compensating for lumped disturbances stemming from allocation errors and external disturbances. An intelligent triggered allocation approach is implemented in the allocation layer to distribute the desired control effect to the actuator with fast and low-complexity allocation considering practical actuator characteristics. The proposed control scheme ensures that all signals in the closed-loop system converge to a residual set in close proximity to the origin within a predefined time, whose time constant can be adjusted as desired by the designer. Furthermore, as the system is governed by the event-triggered mechanism, the communication burden can be considerably reduced. The effectiveness of the proposed controller is demonstrated through both theoretical proof and numerical simulations. [ABSTRACT FROM AUTHOR]

In many applications of cyber-physical systems, a sequence of tasks is necessary to perform a certain functionality. For example, from a sensor to an actuator, the first task reads the sensor value (cause), the second task processes the data, and the third task produces an output for the actuator (an effect is triggered). For such scenarios, the end-to-end timing properties (the so-called end-to-end latency) of the sequence of tasks (the so-called cause-effect chain) are of importance. This tutorial recaps different metrics for the end-to-end latency of cause-effect chains, and summarizes fundamental properties and existing analytical results in a systematic manner. To that end, this tutorial has a special focus on the reaction time (how fast can a reaction be in the worst case) and the data age (how old is the data source of an actuation in the worst case). The goal of this tutorial is to provide a systematic view of the fundamental end-to-end timing properties of cause-effect chains and offer an outlook of possible research directions in the near future. Furthermore, we extend the proof of one fundamental property in the literature to comply with the current state-of-the-art definition of end-to-end latencies. [ABSTRACT FROM AUTHOR]

This article investigates the control problem of unmanned surface vessels with sensor measurement sensitivity under deception attacks, and proposes a novel self‐triggered adaptive neural control scheme under the backstepping design framework. To solve the control design problem of unknown time‐varying gains caused by deception attacks and measurement sensitivity in kinematic and kinetic channels, the parameter adaptive and neural network technology are involved. In addition, to decrease actuator wear caused by the high‐frequency wave and sensor measurement sensitivity and reduce the computational burden caused by continuous monitoring of the triggered condition, a self‐triggered mechanism is constructed in the controller–actuator channel. Finally, a self‐triggered adaptive neural control solution is proposed, which can guarantee that all signals in the whole closed‐loop system are bounded by theoretical analysis. The effectiveness and superiority are verified by numerical simulations. [ABSTRACT FROM AUTHOR]

This study explored the design, performance evaluation, and application of two types of in-plane motion actuators that were scalable to larger sizes—that is, the extension-type electrothermal actuator (ExACT) and retraction-type electrothermal actuator (ReACT). These actuators were based on the displacement amplification mechanism (DAM) principles and regularly arranged structures in mechanical metamaterials. A modular design approach allowed these actuators to be easily configured to the desired size and scaled to create large-scale in-plane motion actuators. Studies were conducted to assess the performance of the ExACT and ReACT, focusing on the actuator displacement and blocking force. The actuation displacements for the 3 × 1 ExACT and ReACT matrices were measured at 2.0 and 0.8 mm, respectively. Similarly, the blocking forces achieved by the actuator matrices were 2.24 and 3.78 N for the ExACT and ReACT, respectively. Subsequently, the ExACT and ReACT were applied to implement large deformable morphing wings, referred to as the ExMOW and ReMOW, respectively. These wings incorporated an additional thickness amplification mechanism resembling an elliptical bridge-type DAM. The wing thickness of the ExMOW increased by approximately one-third of its initial value, whereas that of the ReMOW decreased to approximately one-quarter of its original thickness. [ABSTRACT FROM AUTHOR]

This study introduces piezoelectric actuators for blade vibration control and aims to establish both experimental and numerical benchmarks for active vibration control with macro fiber composite (MFC) piezoelectric actuators on engine blades. It also involves optimizing the placement of MFC actuators. Experimental and numerical assessments were conducted on a 3D-printed fan model with integrated piezoelectric MFC actuators. The results confirm the effectiveness of the proposed approach, aided by a PID controller, in significantly reducing and damping blade vibrations. This comprehensive study offers a promising solution to enhance aviation engine performance and longevity. [ABSTRACT FROM AUTHOR]

Multistable composite laminates are ideal candidates for morphing applications due to their ability to switch between multiple stable states with proper actuation mechanisms. Surface-bonded macro fiber composite (MFC) actuators to trigger snap-through between one stable shape to another by applying external voltages have attracted considerable attention recently. In this work, dynamic snap-through of bistable unsymmetric cross-ply laminate using MFC actuators under oscillating impulse voltages has been investigated. Both unimorph and bimorph laminate-MFC configurations are considered for the analysis. The stable equilibrium configurations of the MFC-actuated bistable laminate, considering the effects of MFC bondage, are discussed using the proposed finite element (FE) framework. Under the action of oscillating impulse voltages, the single-well and cross-well oscillations of the active bistable plate are analyzed in detail through time responses and phase portraits. The FE results show the advantage of actuating MFC layers through the oscillating impulse voltages as it leads to a reduction in the maximum snap-through voltage requirements. [ABSTRACT FROM AUTHOR]

By focusing on vibrations, current wearable haptic devices underutilize the skin's perceptual capabilities. Devices that provide richer haptic stimuli, including contact feedback and/or variable pressure, are typically heavy and bulky due to the underlying actuator technology and the low sensitivity of hairy skin, which covers most of the body. This article presents a system architecture for compact wearable devices that deliver salient and pleasant broad‐bandwidth haptic cues: Cutaneous Electrohydraulic (CUTE) devices combine a custom materials design for soft haptic electrohydraulic actuators that feature high stroke, high force, and electrical safety with a comfortable mounting strategy that places the actuator in a non‐contact resting position. A prototypical wrist‐wearable CUTE device produces rich tactile sensations by making and breaking contact with the skin (2.44 mm actuation stroke), applying high controllable forces (exceeding 2.3 N), and delivering vibrations at a wide range of amplitudes and frequencies (0–200 Hz). A perceptual study with 14 participants achieves 97.9% recognition accuracy across six diverse cues and verifies their pleasant and expressive feel. This system architecture for wearable devices gives unprecedented control over the haptic cues delivered to the skin, providing an elegant and discreet way to activate the user's sense of touch. [ABSTRACT FROM AUTHOR]

ABSTRACT This study devotes itself to the issue of fault detection for a class of discrete‐time Lipschitz nonlinear systems by virtue of a set of restricted frequency‐domain specifications. First of all, unlike traditional Luenberger‐like observers, which only contain a unitary parameter matrix, a novel, more design–degree of freedom incorporated fault detection observer (FDO) under linear‐matrix‐inequality (LMI) conditions is innovatively constructed to access a more flexible practical adjustment range. And the evaluations of both fault sensitivity and disturbance robustness were quantified via finite‐frequency H_$$ {H}_{\_} $$ and L∞$$ {L}_{\infty } $$ indices, respectively. Besides, the actuator and sensor faults were concurrently addressed in a more wide circumstance, where the reformulated Lipschitz property is utilized to handle what the complex nonlinear term causes. Furthermore, a novel, less computational dynamic threshold based on the ellipsoidal set‐membership technique was creatively synthesized during timely fault detection so as to guarantee a smaller range of residual intervals. Finally, simulation examples were conducted to demonstrate the viability and validity of the proposed strategy. [ABSTRACT FROM AUTHOR]

Electrically driven soft pumps act as ideal "hearts" for flexible fluidic systems in soft robots and wearable devices. Dielectric elastomers (DEs) are promising for soft pump fabrication owing to their features of fast response, large strain, high energy density, and low power consumption. However, conventional dielectric elastomer actuators (DEAs) using single DE material usually exhibit poor pumping performance due to electromechanical instability or insulating problems. Herein, a multilayer structured heterogeneous dielectric elastomer actuator (H‐DEA) is fabricated based on thin films of processable, high‐performance dielectric elastomer (PHDE) and silicones, and is integrated onto silicone pump body to build a fully soft pump. The pump achieves a flow rate of 3.25 mL min−1 and a blocked pressure of 2.75 kPa with a mass of less than 1 g and a power consumption of 0.21 W. It maintains pumping functions when being bent or stretched and after twisted. It works for viscous liquids and is demonstrated to drive a soft robotic fluidic circuit. [ABSTRACT FROM AUTHOR]

Over the years, researchers have investigated active metamaterials because of controllability of their geometry and mechanical properties. However, despite the undeniable appeal and significance of this direction of studies from the perspective of many industries, researchers have struggled to systematically design such structures in an easily reproducible and scalable manner. Herein, it is shown that this can be achieved by harnessing the potential of foldable magnetomechanical metamaterials controlled via the external magnetic field. To this aim, two different configurations of the system with one of them being constrained so that it acts similarly to a linear actuator while the other one allows to fully control its expandability and mechanical properties in all directions are presented. Finally, the possibility of stacking the considered structures to create large systems that may exhibit auxetic properties in multiple planes will be discussed. The magnetomechanical metamaterials discussed are very interesting as they offer multidirectional and finely controlled movement which could be untethered. This is particularly promising for use in actuators, vibration dampers as well as scaffolds in deployable structures and impact resistive materials as the mechanical properties can be fine‐tuned by simply adjusting the external magnetic field and reconfiguring the structure. [ABSTRACT FROM AUTHOR]

Failures are inevitable part of any manufacturing system. If not handled properly, they will lead to machine breakdown and line stoppage. One of the causes of failures is unattended faults. Faults are any unwanted deviations that can occur in any component of the system, mechanical parts, software, sensors, actuators, etc. Another concept that helps manufacturers to continue manufacturing efficiently at a reasonable cost and production time is resilience, which is a system's capability to withstand and accommodate disruptions and recover back to an acceptable state as soon as possible. This research will focus on linking the concept of fault detection and diagnosis with fault recovery and resilience of manufacturing systems. To obtain the results, different types of faults are developed in a manufacturing system, and the time taken to handle (detect, diagnose, and recover) each fault is presumed (empirical research findings from literature and case studies were utilized along with conjectural data). Next, with the help of simulation software, the manufacturing system is modeled, and the impact of each type of fault on the system and its resiliency is studied. Finally, with quantitative measures, the system's resilience is calculated. [ABSTRACT FROM AUTHOR]

A design concept for porous hydrogel actuators is demonstrated, combining lower critical solution temperature (LCST)-type phase separation with crystallinity formation. In contrast to the existing methods of producing porous hydrogels, our concept could not only generate fast actuation speed, but also greatly enhance the hydrogel tensile strength and toughness. [ABSTRACT FROM AUTHOR]

Soft actuators are critical for enabling soft robots, medical devices, and haptic systems. Many soft actuators, however, require power to hold a configuration and rely on hard circuitry for control, limiting their potential applications. In this work, the first soft electromagnetic system is demonstrated for externally‐controlled bistable actuation or self‐regulated astable oscillation. This novel bellows‐shaped actuator uses liquid metal encased in silicone as a compliant conductor that is capable of force generation, integrated sensing, and self‐reconnecting. In the bistable configuration, the actuator can hold positions with no power. By utilizing a unique soft kinking mechanism, the actuator can generate feedback for self‐regulated oscillation. The construction, sensing, and feedback mechanisms for this actuator are first discussed. Then, the force output, thermal performance, and dynamics are characterized. The bistable version has a stroke of 6 mm and can compress/expand with only 15 W of power for 30 ms. The astable version has a stroke of 3 mm and can oscillate at 27 Hz with 18 W of power. Several applications are demonstrated including bistable crawling, hopping, pulsing, and swimming. By adding a 20 V battery, self‐regulated astable vibrational locomotion is also demonstrated. Overall, this work shows how these actuators and oscillators can bridge the gap between conventional and soft robots. [ABSTRACT FROM AUTHOR]

Shape adjustment of large planar phased array antennas is significant because the shape distortion of phased arrays can greatly reduce the antenna's gain in the observing direction. This study selects the inherent diagonal cables driven by motors as actuators, initially used to improve the stiffness of the antenna structure. The shape adjustment can be implemented by changing the length of the diagonal cables, so that there is no need to design additional control devices, which can significantly reduce the mass and improve the reliability of the antenna system. For shape adjustment, the cable tensions are chosen as the control inputs in general, but for structures with finite deformations, the cable tensions may be strongly coupled and therefore can no longer be used as the control inputs. We examine all the sources of the elongation of the cable actuator and group them into three categories: pre‐elongation, passive elongation, and feedback elongation. Since the feedback elongations of different cables are driven independently by the motors and do not change with the structural deformation, they can be used as the control inputs. Giving a detailed theoretical derivation, this paper demonstrates the necessity of considering nonlinearity of the cable actuator and proposes a nonlinear model of the active cable element. Further, an optimization model is established for shape adjustment, and the genetic algorithm is used to solve this problem. The effectiveness of the proposed nonlinear active cable element and the shape adjustment method is validated by simulations. Results show that the shape adjustment can be successfully achieved by the nonlinear cable actuators proposed in this paper. Moreover, the effect of pre‐elongation on the stiffness of the antenna structure can be well reflected by the nonlinear cable actuators, and the relationship between the shape adjustment and the number of actuators is also investigated. [ABSTRACT FROM AUTHOR]

Pump-controlled actuators, or more generically, hydrostatic actuators, have the significant advantage of not relying on valves to control the cylinders. This results in much better energy usage compared to traditional valve-controlled systems. However, it is possible to further increase energy efficiency by storing load energy in motoring quadrants and subsequently releasing the stored energy back into the circuit or making it available for other applications. Much work is needed to practically study energy storage in hydrostatic actuators. In this note, we review the two basic ways hydraulic energy can be saved in circuits using accumulators, emphasizing their advantages and drawbacks. The review is followed by a brief description of the current research being carried out at the University of Manitoba in Canada. We aim to show that research in this field is promising and demonstrates that hydraulic power transmission can not only be made efficient but also be used to regenerate load energy that would otherwise go to waste. [ABSTRACT FROM AUTHOR]

ABSTRACT This article investigates the issue of finite‐time tracking control for uncertain robotic manipulator systems with unknown actuator faults and shifting loads based upon a fuzzy sliding mode control strategy. A novel fuzzy adaptive sliding mode fault‐tolerant control law is synthesized, where a fuzzy approximation algorithm is utilized to fit the unknown plant parameters, potential disturbances, and relational actuator faults, and the corresponding adaptive robust term is designed to estimate the unidentified boundary of the estimated errors, and the boundedness of all the relevant design parameters of the manipulator systems is ensured combining with the average dwell time mechanism of switched system control theory. Furthermore, the reachability of the pre‐devised sliding surface and the finite‐time convergence of tracking error are achieved under the presented controller design. Ultimately, simulation results exhibit the feasibility and superiority of the proposed algorithm. [ABSTRACT FROM AUTHOR]

In this paper, a novel miniature piezoelectric actuator was proposed with a compact ring structure and four driving teeth. The prominent feature was that the ring-shaped piezoelectric actuator could not only drive multiple types of movers, but also achieve multi-DOF motions by using the hybrid and traveling vibration modes. On the one hand, the four teeth were driven by only one ring-shaped piezoelectric actuator instead of four actuators separately, and were arranged circumferentially capable of supporting and driving both flat and spherical movers. On the other hand, the 4th-order radial and axial vibration modes were degenerated to achieve linear motions in the ox and oy directions; while two 3rd-order axial vibration modes were hybrid to realize the rotary motion around oz direction. FEM (finite element method) was employed to determine parameters and verify the working principles. Then, a prototype with a size of about Φ60 × 13 mm3 and a weight of 40 g was fabricated, and the characteristics were tested. Experimental results showed that the maximum speed, resolution and load realized in the linear motions were 23.3 mm/s, 0.7 μm, and 200 g, respectively; while that in the rotary motions were 0.8 rad/s, 11.5 μrad, and 200 g, respectively. The multi-DOF motions were successfully achieved by degenerating different vibration modes of the same ring structure. [ABSTRACT FROM AUTHOR]

Planar piezoelectric actuators, which can achieve high-precision motions over a wide range, have been widely applied in high-end equipment fields. However, the existing planar piezoelectric actuators can no longer meet the high actuation characteristics required for the rapidly development of these fields, which include large travel, high resolution, fast speed, planar three degrees of freedom (3-DOF) and a compact structure. A planar piezoelectric actuator with resonant actuation is proposed and tested in this work. The actuator consists of four symmetrically configured uniform bending-bending hybrid piezoelectric units, which coordinate to achieve large travel and planar 3-DOF characteristics. A vibration isolation mechanism adopting thin beam structure with low stiffness in coupling directions is designed to achieve vibration isolation among the units. The actuator can operate in high frequency resonance mode and low frequency stepping mode, allowing for the achievement of high-speed and high-resolution characteristics. A prototype is fabricated and tested. A compact structure measuring 53 mm × 53 mm × 13 mm and weighing only 30.2 g has been achieved. The maximum linear and rotary speeds have been tested to be over 400 mm/s and 13 rad/s, respectively. The linear and rotary resolutions are 0.42 μm and 12.9 μrad, respectively. The proposed actuator achieves characteristics of large travel, high resolution, fast speed, 3-DOF and a compact structure. [ABSTRACT FROM AUTHOR]

Reconfigurable structures can perform multiple functions and are useful in confined environments with complicated access. To extend the complexity of configurations achievable with reconfigurable mechanisms, remotely reconfigurable mechanisms are explored. Magnetically responsive phase change materials are selected for actuation, and origami backbones as the structure. Modulating the mechanism's coupling and constraints, multiple configurations are achieved. Three functional aspects of in situ reconfiguration are demonstrated. First, selective attachment and actuation enable remote mechanisms to deploy and actuate. Second, reconfiguration that modifies the constraints allows for new kinematics even in confined environments. Third, the actuator can construct and change the configuration of an origami structure, allowing subsequent functions to emerge. Tetherless interface reconfiguration is demonstrated with an in situ needle puncture and escape room puzzle, which can benefit existing robotic applications in confined spaces. [ABSTRACT FROM AUTHOR]

The flexible electronics market is rapidly growing, driven by demand in the healthcare, automotive, and consumer industries. While these technologies enhance the daily lives, the electronic waste (e‐waste) generated in tandem poses significant environmental challenges. Covalent adaptable networks (CANs) are crosslinked polymers bearing dynamic covalent bonds (DCBs). These exchangeable bonds endow CANs not only with the high mechanical and chemical stability of thermosets but also with the stimuli‐activated reprocessability of thermoplastics. CAN‐derived electronics offer a solution to alleviate e‐waste generation since the DCBs allow for the self‐healing and recycling of these devices. Additionally, the ability of CANs to respond to stimuli is highly desirable for smart materials, especially flexible electronics. In this review, how CANs play the role of conformable substrates and dielectrics, and also as flexible electronic connectors, sensors, and actuators is comprehensively cataloged. Furthermore, the advantages gained by utilizing CANs in electronic sensors and actuators is highlighted, as well as provide the insights into design strategies to address the challenges of creating high‐performance sustainable soft electronics. [ABSTRACT FROM AUTHOR]

The folding wing deployment mechanisms of aircraft are constrained by weight and space limitations, necessitating fewer actuators, multiple outputs, compact designs, and high efficiency. However, existing folding wing mechanisms often overlook the impact of performance in configuration design. Additionally, they struggle to achieve the synchronous unfolding of multiple wings using a single drive. This paper presents a design methodology for multi-wing deployment mechanisms based on configuration topology and multiple performance indicators. Specifically, seventeen configurations of multi-wing deployment mechanisms are developed based on functional requirements, along with expression methods for performance indicators, including compactness, mechanism stiffness, dynamic sensitivity, motion transmission, and joint transmission efficiency. The optimal configuration for the multi-wing deployment mechanism is identified utilizing the fuzzy comprehensive evaluation. Moreover, the transmission efficiency of multiple configurations is calculated across different scale parameters. Simulation analyses and prototype experiments are conducted to validate the design. The results indicate that the transmission efficiency of the optimized configuration consistently exceeds that of the other configurations. Maximum efficiencies surpass those of the other configurations by 2.4% and 5.7%. Importantly, this study introduces a quantitative expression method for multiple performance indicators at the configuration design stage. This approach enables the integration of various performance metrics with configuration designs. Overall, this research provides a novel approach for the innovative design of multi-wing deployment mechanisms in aircraft. Additionally, considering performance in the selection of mechanism configurations during engineering design offers valuable insights and potential applications. [ABSTRACT FROM AUTHOR]

3D/4D printing technologies are currently among the fastest growing cutting-edge fabrication technologies. The scale of their applications is vast and applicable to nearly all industries. Three-dimensional printing technologies are particularly popular in robotics and especially in advanced design innovative solutions for areas such as manufacturing, space technology, and medicine. The development of robotics, and, in particular, of the precision of manufactured components, such as actuators, pneumatic muscles, power transmission units, etc., means that new prototypes are still being made, and the use of 3D printers reduces the production time severalfold, allowing for the completion of necessary simulations and tests. In addition, the use of 3D printers allows for the production of thin-walled and cellular structures, which is a great advantage compared to conventional fabrication technologies. In the range of 3D printers available on the market, only a few selected technologies allow for actual use in the construction of advanced robot elements (muscles, vibration dampers, etc.). In an era of rapid growth in the precision of available 3D printers and modern materials, 3D printing may soon become a major tool in robotics. This article presents an overview of 3D printing technologies and materials in terms of their application in robotics and provides examples of the use of 3D and 4D printing in prototyping and fabricating robotic elements with particular emphasis on the current state of the art. The study considered the possibilities of using 3D/4D printing in robotics with the use of polymeric materials. Three-dimensional and 4D printing technologies can have a major impact on achieving sustainable development goals by providing appropriate strategies to minimise health risks and promote environmentally friendly production processes. The review of the literature and the research work currently being carried out in this area is very promising and it seems that 3D/4D printing in robotics is widely used and is still developing, which allows us to conclude that in the near future the number of research works in this field will increase rapidly. [ABSTRACT FROM AUTHOR]

Despite recent significant breakthroughs in novel mechanochromic luminescent (ML) materials, developing a high‐sensitivity ML material is still challengeable. Herein, a "friction‐induced crystallization" strategy is proposed to realize highly sensitive transformations of luminescent signal, through an integration of polymeric chains and an aggregation‐sensitive luminescent core, which act as mechanical sensors and fluochromic actuators, respectively. The coupling of these two components enables the material to crystallize in response to shear friction, thereby exhibiting blue‐shift fluorescence due to a more restricted relaxation pathway. This study underscores a high‐sensitivity ML material based on the precise regulation of molecular‐scale motions, and also expands the scope and potential of ML materials toward user‐friendly, interactive wearable devices. [ABSTRACT FROM AUTHOR]

An event‐based supervisory control scheme, in the Ramdage–Wonham framework, will be proposed for the cyber‐physical Waterway Lock system, known as Lock III, in Tilburg, the Netherlands. The proposed control scheme imposes desired behavior, by appropriately disabling controllable events, so as to avoid activation of actuator commands that may lead to undesired and potentially hazardous operating states. The discrete event model of the total Waterway Lock system, comprising 54 actuator and sensor automata, will be presented in analytic 6‐tuple forms of its subsystems. The system's desired behavior, which is expressed using six rules, will be formulated as 84 regular and prefix closed languages that will be realized as appropriate supervisor automata. All supervisors are developed by a general two‐state supervisor form, which facilitates their implementation. A distributed control architecture will be proposed, which organizes all supervisors in distinct groups, each of which controls one and only one distinct command event. The complexity of the proposed control scheme will be computed to be equal to (168,324,564), being reasonable, as compared to the large number of subsystems and the restrictive design requirements. The physical realizability of the 84 supervisors, with respect to the 54 subsystems of the waterway lock system, will be proved analytically. Also, it will be proved analytically that the proposed supervisor architecture guarantees the nonblocking property of the controlled automaton, including all subsystems. The establishment of these analytic proofs supports the extendibility of the results to other applications. To demonstrate the resulting large‐scale controlled automaton's good performance, its marked behavior and simulation results will be presented. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper addresses a switched sampled‐data control design for stabilization of the N‐dimensional (N‐D) semilinear heat equation with a mobile actuator. It is supposed that discrete‐time averaged measurements are available. The system is known to be stabilizable by the static output‐feedback employing several distributed in space actuators and sensors, but is not stabilizable by only one of the actuator‐sensor pairs. Does there exist a switching stabilizing static output‐feedback such that at all times, only one actuator‐sensor pair is active? In our recent paper we gave a positive answer and found the appropriate switching sampled‐data time‐triggered control law for the one‐dimensional (1‐D) case. In this paper, to enlarge the time between switching (which means to reduce the frequency of actuator moving to the active domain), we present an event‐triggered control for stabilization by switching. Moreover, we extend the results for stabilization by switching to the N‐D case. Numerical examples show that the switching‐based event‐triggered controller essentially decreases the frequency of the actuator moving compared to the time‐triggered controller, reducing operating costs. [ABSTRACT FROM AUTHOR]

Purpose: Investigating the nonlinear dynamic response of giant magnetostrictive actuator (GMA) is a valuable subject in the field of precision engineering. In order to effectively control the nonlinear dynamic response of a single-degree-of-freedom GMA, a fractional-order time-lag feedback controller is designed. Methods: We model the nonlinear dynamics of the controlled GMA through the geometric nonlinearity imposed by the disc-spring mechanism and introduce the dimensionless for simplification. The flexible order adjustment capability of the Riemann–Liouville fractional-order derivatives is adopted to more accurately simulate the memory effects and nonlocal properties of the system. It effectively compensates its nonlinear dynamic behavior to optimize the system design and control. By using the averaging method, the amplitude–frequency response equations of the primary resonance in the system containing a fractional-order time-lag feedback control strategy are solved and the stability conditions are obtained. Results: Through detailed parametric studies, the effects of key structural parameters within the uncontrolled GMA and the adjustment of the parameters under fractional-order time-lag feedback control on the primary resonance response characteristics are researched. Moreover, the time-lag feedback gain and fractional-order are adjusted to effectively guide the system into the desired chaos, or to get the system out of the chaotic state and back to a stable periodic behavior. Conclusions: The research results show that the unstable region of the primary resonance curve can be significantly reduced or eliminated by choosing suitable adjustment parameters, so as to better realize accurate and reliable motion control. [ABSTRACT FROM AUTHOR]

Stroke patients can benefit significantly from active recovery during the critical "golden period" following a cerebrovascular event. While healthcare professionals provide support, selfdirected training is also crucial for rehabilitation. This paper presents the structural design of bidirectional soft pneumatic actuators, the fabrication process, and the implementation of a soft rehabilitation wearable glove. Finite Element Analysis (FEA) simulations and experiments were performed to evaluate the mechanical behaviour and performance of the glove, specifically with respect to bending angle and force outputs during pressurization. The glove operation was controlled via a Peripheral Interface Controller (PIC) microcontroller-based hardware system. The actuators between each finger provided extension and contraction motions, enhancing the effectiveness of rehabilitation. Experimental evaluations focused on rehabilitation training at a clinic center with real patients. The results from the experiments indicate that the developed device has the potential to significantly improve hand mobility and increase the range of training. [ABSTRACT FROM AUTHOR]

A new motion control system for a hydraulic rotary actuator was designed in this work. The hydraulic fluid that goes to the actuator was used in a variable displacement pump to control the actuator movement. A mathematical model was conducted and the stability and performance of the open loop system were studied. Routh-Hurwitz stability criterion was implemented to assess the system stability which showed that the system is stable as long as realistic parameters are chosen for the design. Since the open loop system showed poor performance, PID and H-infinity controllers were considered to improve the system overall performance. Multiplicative uncertainty was considered in the H-infinity design process to ensure that the system responds well when uncertainties in the system parameters exist within a specified range. The leakage and friction coefficients are the parameters that were considered uncertain due to their expected change with time. The uncertainty was considered in the viscous friction and the leakage coefficients within a range of ±3%. The results showed that the open system has about 20% percent overshoot, 10% steady state error for a unit step input signal and a poor disturbance rejection. The system with both H-infinity and PID controller has no steady state error and a low settling time which is about 7 time constants (6.3 ms). The H-infinity controller provides the least percent overshoot in response to the unit step input signal, 4% compared to 10% for the PID controller. In addition, the H-infinity controller provides faster response and better disturbance rejection characteristics. Finally, only the H-infinity controller meets the robustness requirements. [ABSTRACT FROM AUTHOR]

In this paper, fault-tolerant control (FTC) of a four-motor servo system in the presence of an actuator partial loss of effectiveness (PLOE) is studied. First, a current observer is designed to observe the effectiveness factor and current of each motor to determine the motor's working status. Second, to reduce the computational burden in the process of backstepping design, the command filter is used for handling the computational complexity. In the design process, the speed synchronisation and torque balance signals are designed to ensure that each motor can still maintain high synchronisation performance after the fault occurs. Finally, the effectiveness of the proposed FTC method is proved and verified through simulations, and the system can accurately track the desired angular position on the premise of ensuring synchronisation performance even in the presence of the fault. [ABSTRACT FROM AUTHOR]

This paper is dedicated to the problem of actuator fault estimation and fault-tolerant control for general linear leader–follower multi-agent systems subject to external disturbance and communication delay. First, the intermediate variable observer is constructed to estimate faults using relative information with symmetric time delays. A contradiction between the convergence speed of estimation error and the time-delay margin is revealed, where quick convergence implies small time-delay margin. As such, the augmented system observer is employed to improve the convergence speed. In the next, integrated scheme is adopted to handle the bi-directional interaction between fault estimation and fault-tolerant control arising from external disturbance and time-varying faults. In addition, we also consider the asymmetric delay case with only transmission delay. The delay-independent stability condition is derived with the use of augmented system observer by virtue of Lyapunov–Krasovskii function and H ∞ robust theories. Finally, the simulation results are presented to verify the effectiveness of proposed method. [ABSTRACT FROM AUTHOR]

Electro‐mechanical actuators with redundancy design use a cross‐coupling control strategy to enhance the coordinated control capability of the aviation motors. Due to its linear control characteristic, traditional cross‐coupling control reveals moderate dynamic response performance and synchronisation control accuracy. To further reduce the susceptibility to load torque and parameter perturbations in the application of a dual permanent magnet synchronous motor system, this paper proposes a non‐linear active disturbance rejection control (ADRC)‐based synchronisation control strategy. Considering the low gain problem of traditional ADRC when the speed tracking error is large, a non‐linear ADRC speed controller with an efal function is designed. Meanwhile, a Levant differentiator is proposed to improve the speed tracking performance during dynamic processes. Moreover, a non‐linear synchronous controller with current constraints is applied to the cross‐coupling control to enhance the synchronisation convergence performance of the dual‐PMSM system. Finally, simulation and experimental results demonstrate the effectiveness of the proposed non‐linear ADRC speed synchronisation control. [ABSTRACT FROM AUTHOR]

The complexity of real‐world systems poses challenges to model‐based control, sparking significant interest in model‐free control methods. By depending exclusively on the system's input–output data, the proposed method eliminates the need to construct intricate internal system models. The implementation is straightforward, can satisfy bounded control inputs, and allows for arbitrary adjustment of the actuator's execution frequency. The proposed method establishes an iterative mechanism under the constraint of bounded control inputs. It guarantees the algorithm's convergence by ensuring the continuous narrowing of the control interval. Furthermore, the update conditions within the iterative strategy can adapt to extremely low and continuously adjusting actuator execution frequencies. The bounded stability of the control method is proven using the continuity definition of functions. Its effectiveness and feasibility are validated through simulation and experimental verification. [ABSTRACT FROM AUTHOR]