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Copyright of Przeglad Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper addresses the optimal control problem with sparse controls of a Timoshenko beam, its numerical approximation using the finite element method, and the numerical solution via nonsmooth methods. Incorporating sparsity‐promoting terms in the cost function is practically useful for beam vibration models and results in the localization of the control action that facilitates the placement of actuators or control devices. We consider two types of sparsity‐inducing penalizers: the L1$$ {L}^1 $$‐norm and the L0$$ {L}^0 $$‐penalizer, which measures function support. We analyze discretized problems utilizing linear finite elements with a locking‐free scheme to approximate the states and adjoint states. We confirm that this approximation has the looking‐free property required to achieve a linear convergence linear order of approximation for L1$$ {L}^1 $$ control case and depending on the set of switching points in the L0$$ {L}^0 $$ controls. This is similar to the purely L2$$ {L}^2 $$‐norm penalized optimal control, where the order of approximation is independent of the thickness of the beam. [ABSTRACT FROM AUTHOR]

Copyright of Automatisierungstechnik is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The finite time tracking control of n‐link robotic system is studied for model uncertainties and actuator saturation. Firstly, a smooth function and adaptive fuzzy neural network online learning algorithm are designed to address the actuator saturation and dynamic model uncertainties. Secondly, a new finite‐time command filtered technique is proposed to filter the virtual control signal. The improved error compensation signal can reduce the impact of filtering errors, and the tracking errors of system quickly converge to a smaller compact set within finite time. Finally, adaptive fuzzy neural network finite‐time command filtered control achieves finite‐time stability through Lyapunov stability criterion. Simulation results verify the effectiveness of the proposed control. [ABSTRACT FROM AUTHOR]

A new stick-slip type piezoelectric actuator based on asymmetric structure is proposed. The actuator uses a stator with the asymmetric diamond-shaped structure, and the structure size is determined by finite element simulation. First, the structure and working principle of the proposed actuator are introduced. The elongation deformation of the piezo stack is transferred to the driving tip by the used asymmetric diamond-shaped hinge. This produces a diagonal movement on the driving tip, with the lateral motion used for driving and the longitudinal motion used for pressing the slider, respectively. Then, the statics analysis of the proposed piezoelectric actuator is performed by finite element simulation. The simulated displacements of the driving tip under different structures are obtained, and then the structure size is determined. Finally, an experimental system is established to study the performance of the proposed piezoelectric actuator. The experimental results show that the maximum output velocity of the proposed actuator is 5.26 mm/s. The maximum output force is 1.9N when the locking force is 2N and the drive frequency is 660 Hz. [ABSTRACT FROM AUTHOR]

Actuator line modeling of wind turbines requires the definition of a free‐stream velocity in a computational mesh and a regularization kernel to project the computed body forces onto the domain. Both choices strongly influence the results. In this work, a novel velocity sampling method—the so‐called effective velocity model (EVM)—is implemented in the CFD software SOWFA, validated, and compared to pre‐existing approaches. Results show superior method robustness with respect to the regularization kernel width (ϵ) choice while preserving acceptable accuracy. In particular, the power predicted by the EVM is nearly independent of the ϵ value. [ABSTRACT FROM AUTHOR]

Copyright of International Journal of Engineering Transactions B: Applications is the property of International Journal of Engineering (IJE) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study utilizes the Takagi–Sugeno fuzzy model to represent a subset of nonlinear systems and presents an innovative adaptive approach for optimal dynamic terminal sliding mode control (TSMC). The systems under consideration encompass bounded uncertainties in parameters and actuators, as well as susceptibility to external disturbances. Performance evaluation entails the design of an adaptive terminal sliding surface through a two-step process. Initially, a state feedback gain and controller are developed using Linear Matrix Inequality (LMI) techniques, grounded on H 2 -performance and partial eigenstructure assignment. Dynamic sliding gain is subsequently attained via convex optimization, leveraging the derived state feedback gain and the designed terminal sliding mode (TSM) controller. This approach diverges from conventional methods by incorporating control effort and estimating actuator uncertainty bounds, while also addressing sliding surface and TSM controller design intricacies. The TSM controller is redefined into a strict feedback form, rendering it suitable for addressing output-tracking challenges in nonlinear systems. Comparative simulations validate the effectiveness of the proposed TSM controller, emphasizing its practical applicability. [ABSTRACT FROM AUTHOR]

Polymer-based actuators have gained extensive attention owing to their potential applications in aerospace, soft robotics, etc. However, poor mechanical properties, the inability of multi-stimuli response and programmable deformation, and the costly fabrication procedure have significantly hindered their practical application. Herein, these issues are overcome via a simple and scalable one-step molding method. The actuator is fabricated by hot-pressing commercial unidirectional carbon fiber/epoxy prepregs with a commodity PC membrane. Notable CTE differences between the CF and PC layers endow the bilayer actuator with fast and reliable actuation deformation. Benefiting from the high strength of CF, the actuator exhibits excellent mechanical performance. Moreover, the anisotropy of CF endows the actuator with design flexibility. Furthermore, the multifunction of CF makes the actuator capable of responding to thermal, optical, and electrical stimulation simultaneously. Based on the bilayer actuator, we successfully fabricated intelligent devices such as light-driven biomimetic flowers, intelligent grippers, and gesture-simulating apparatuses, which further validate the programmability and multi-stimuli response characteristics of this actuator. Strikingly, the prepared gripper possesses a grasping capacity approximately 31.2 times its own weight. It is thus believed that the concept presented paves the way for building next-generation robust robotics. [ABSTRACT FROM AUTHOR]

This article investigates the robust cooperative fault-tolerant control problem of multi-agent systems subject to mismatched uncertainties and actuator faults. During the design process of the intermediate variable estimator, there is no need to satisfy fault estimation matching conditions, and this overcomes a crucial constraint of traditional observers and estimators. The feedback term of the designed estimator contains the centralized estimation errors and the distributed estimation errors of the agent, and this further improves the design freedom of the proposed estimator. A novel fault-tolerant control protocol is designed based on the fault estimation information. In this work, the bounds of the fault and its derivatives are unknown, and the considered method is applicable to both directed and undirected multi-agent systems. Furthermore, the parameters of the estimator are determined through the resolution of a linear matrix inequality (LMI), which is decoupled by employing coordinate transformation and Schur decomposition. Lastly, a numerical simulation result is used to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, we present the design of a fractional-order sliding mode observer (FO-SMO) for actuator fault estimation in a quadrotor unmanned aerial vehicle (QUAV) system. Actuator faults can significantly compromise the stability and performance of QUAV systems; therefore, early detection and compensation are crucial. Sliding mode observers (SMOs) have recently demonstrated their accuracy in estimating faults in QUAV systems under matched uncertainties. However, existing SMOs encounter difficulties associated with chattering and sensitivity to initial conditions and noise. These challenges significantly impact the precision of fault estimation and may even render fault estimation impossible depending on the magnitude of the fault. To address these challenges, we propose a new fractional-order SMO structure based on the Caputo derivative definition. To demonstrate the effectiveness of the proposed FO-SMO in overcoming the limitations associated with classical SMOs, we assess the robustness of the FO-SMO under three distinct scenarios. First, we examined its performance in estimating actuator faults under varying initial conditions. Second, we evaluated its ability to handle significant chattering phenomena during fault estimation. Finally, we analyzed its performance in fault estimation under noisy conditions. For comparison purposes, we assess the performance of both observers using the Normalized Root-Mean-Square Error (NRMSE) criterion. The results demonstrate that our approach enables more accurate actuator fault estimation, particularly in scenarios involving chattering phenomena and noise. In contrast, the performance of classical (non-fractional) SMO suffers significantly under these conditions. We concluded that our FO-SMO is more robust to initial conditions, chattering phenomena, and noise than the classical SMO. [ABSTRACT FROM AUTHOR]

Poly(ionic liquid) (PIL)‐based porous membranes are extensively investigated as soft polymer actuators. While PILs have shown significant advancements in membrane fabrication and stabilization of metal nanoparticles (MNPs), research on integrating MNPs into porous membranes to achieve actuation behavior under multiple stimuli is limited. Herein, this work presents a new paradigm for designing a porous PIL‐polyacrylic acid (PAA) membrane with a distinct MNP gradient via a top‐bottom diffusion approach involving a metal salt precursor solution and NaBH4 as a reducing agent. The strong binding sites provided by PILs, combined with the gradient distribution of ‐COO− groups across the membrane cross‐section, play a significant role in controlling the MNPs' gradient distribution. Interestingly, the MNPs within the membrane display excellent catalytic activity in exothermic reactions such as H2O2 decomposition, dissipating uneven heat that quickly permeates the membrane network. This induces asymmetrical swelling of polymer chains, resulting in rapid membrane bending. Furthermore, such MNP‐loaded membrane could serve as a portable test paper for visually monitoring H2O2. This advancement paves the way for the development of intricate smart actuation materials and expands their practical applications in various real‐life scenarios. [ABSTRACT FROM AUTHOR]

Smart hydrogels responsive to external stimuli are promising for various applications such as soft robotics and smart devices. High mechanical strength and fast response rate are particularly important for the construction of hydrogel actuators. Herein, tough hydrogels with rapid response rates are synthesized using vinyl‐functionalized poly(N‐isopropylacrylamide) (PNIPAM) microgels as macro‐crosslinkers and N‐isopropylacrylamide as monomers. The compression strength of the obtained PNIPAM hydrogels is up to 7.13 MPa. The response rate of the microgel‐crosslinked hydrogels is significantly enhanced compared with conventional chemically crosslinked PNIPAM hydrogels. The mechanical strength and response rate of hydrogels can be adjusted by varying the proportion of monomers and crosslinkers. The lower critical solution temperature (LCST) of the PNIPAM hydrogels could be tuned by copolymerizing with ionic monomer sodium methacrylate. Thermo‐responsive bilayer hydrogels are fabricated using PINPAM hydrogels with different LCSTs via a layer‐by‐layer method. The thermo‐responsive fast swelling and shrinking properties of the two layers endow the bilayer hydrogel with anisotropic structures and asymmetric response characteristics, allowing the hydrogel to respond rapidly. The bilayer hydrogels are fabricated into clamps to grab small objects and flowers that mimicked the closure of petals, and it shows great application prospects in the field of actuators. [ABSTRACT FROM AUTHOR]

The purpose of the Hydracer project is to discuss the system performance of the EHAs (Electro-Hydrostatic Actuators) when integrated into robotic systems. We have developed EHAs focusing on compactness, light-weight, force controllability, and back-drivability. The requirements such as compactness and light-weight lead us to the adoption of high-pressure, which unfortunately contradicts with the other requirements, namely, force controllability and back-drivability. The contradiction indicates the necessity of study to find the balanced specification between them, which was the question we raised when we started the development of Hydracer, a 6-DOF manipulator driven by EHAs. The system design started following the specifications of an industrial standard of small-size manipulators. In the previous paper, we reported on the design and evaluation of actuators, namely, the linear EHA modules for the first three joints from the base and the ceramic-reinforced vane motors for the last three. We could also discuss the preliminary results of force control of the last three (wrist) joints. In this paper, we report on the performance of force-controllability and backdrivability of the first three joints of the manipulator after integrating force controllers and gravity compensation. It provides useful information about the total performance of manipulators driven by EHAs. The RMSEs (root mean square errors) of torques of the first three joints under the gravity compensation were 0.53, 1,7, and 1.2 Nm respectively, while the manipulator could carry 10 kg payload at the horizontally stretched configuration for 5 s. [ABSTRACT FROM AUTHOR]

Flexible-joint manipulators (FJMs) have been attracting much attention in recent decades. However, position control and vibration suppression of single-input (SI) multi-degrees-of-freedom (multi( $ {\geqslant }3 $ ⩾ 3)-DOF) FJM is still a high mountain to climb due to the characteristic that some states of such FJMs cannot be directly controlled by the SI. This paper aims to carry out this challenging research. We present a double-loop frame-based adaptive neural sliding-mode control method for an uncertain horizontal SI 3-DOF FJM, i.e. a two-link FJM with only one actuator at the first joint. Since only the actuator angle can be directly controlled, in the inner loop, we design a torque controller so that the actuator angle tracks a time-varying reference actuator angle, designed in real-time by the outer loop. In the outer loop, we consider the reference actuator angle as a virtual control signal and design it based on the dynamic coupling relationships, aiming to indirectly control the first link to its target position and suppress the vibration of both links. Furthermore, to enhance the transient system performance, we plan the input signal of the outer loop (i.e. the target angle) as a smooth reference-trajectory signal. The validity and superiority of this method are demonstrated in simulations. [ABSTRACT FROM AUTHOR]

To achieve predefined‐time trajectory tracking control of a flexible‐joint space robot(FJSR) with actuator constraints, a nonsingular predefined‐time dynamic surface control scheme is developed. The input saturation caused by actuator constraints is addressed via the designed predefined‐time anti‐saturation compensator. On this basis, two different control laws are designed for such high‐order nonlinear systems by utilizing the backstepping technique, and a novel nonlinear filter is constructed to filter the virtual control signals, thus avoiding the "differential expansion" phenomenon. Moreover, a singularity‐free auxiliary function is designed to solve the singularity issue generated by the derivative of fractional power terms in the predefined‐time control algorithm framework. The closed‐loop system is proven to be semi‐globally predefined‐timely uniformly ultimately bounded (SGPTUUB) via constructing the suitable Lyapunov function. The difference and effectiveness of the two designed control laws are illustrated by the conducted simulations. Both of them allow the FJSR system to track the desired trajectory in a reasonably predefined time. [ABSTRACT FROM AUTHOR]

This article addresses the event‐triggered adaptive consensus control of nonlinear multi‐agent systems with unknown control direction and actuator saturation. A new robust adaptive control algorithm based on an event‐triggered mechanism is designed. The smooth Lipschitz function approximates the saturated nonlinear function, while the Nussbaum function handles unknown control directions and residual terms. The event‐triggered mechanism is designed to determine the time of communication, significantly reducing the communication burden. An additional estimator is utilized to deal with unknown parameters involved in neighbor dynamics and prevent information exchange to consistency errors between connected subsystems. The results show that all the signals of the closed‐loop system are uniformly bounded, and the consensus tracking error converges to a bounded set. Meanwhile, Zeno's behavior is eliminated. Simulation results confirm the superiority of the proposed method. [ABSTRACT FROM AUTHOR]

An adaptive neural network fault‐tolerant control method is proposed for the non‐affine multi‐agent systems with actuator failure and input saturation. Through the transformation of the original multi‐agent systems, an equivalent model is proposed. Considering that the signal input of multi‐agent systems is limited, this article will solve the input saturation problem. But in a real system, the actuator would probably fail. Therefore, a fault tolerant control algorithm is proposed to solve the fault problem in the systems. In this article, an adaptive distributed controller is designed to eliminate the uncertainty of the systems. At the same time, the integral barrier Lyapunov function is selected to verify the stability. Finally, a simulation example is given to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents the results of a computer optimising a multibody system using Generative Design methods to select a lower-cost actuator that meets process requirements with its parameters. Optimisation was performed to reduce the mass of the motion apparatus components of the author's CPM device, used for the rehabilitation of patients after knee arthroscopy and total or partial knee replacement. An analysis of the kinematics and dynamics of the multibody mechanism, based on a virtual model, was carried out to identify the requirements for selecting an actuator. The main components of the motion apparatus mechanism were subjected to a series of numerical analyses using selected CAD/CAE tools, with the assumed criterion of varying material and component shapes to ensure that the required strength and accuracy of the mechanism links were maintained, assuming the same functionality. The results of the numerical analyses will be the basis for the selection of the optimum solution, for which a new, lower-cost actuator will be selected. [ABSTRACT FROM AUTHOR]

Dielectric elastomers (DEs) are actively being studied to develop soft transducers including DE actuators (DEAs). Poly(dimethylsiloxane) is a popular elastomer component and known for yielding a relatively low dielectric constant (ε′) for DEAs. Herein, a novel polysiloxane‐based DE, namely, DOWSIL ME 7540 Electroactive Elastomer is reported, offering ε′ = 5.2–5.5 over a broad frequency range that is nearly two times as high as that for commercially popular SYLGARD 184 Silicone Elastomer as a comparative DE. Weibull analysis is useful for statistically evaluating dielectric strength (DS). ME 7540 DE attains DS = 63.8 V μm−1, which is only 16% lower than DS = 75.7 V μm−1 obtained with 184 DE. The material parameters obtained by fitting uniaxial extension results with the Yeoh model are used to simulate an equibiaxial stress–stretch ratio (λib) curve, with i = 1 or 2, and the relationship between voltage and λ1b. Simulation and actuation experiments confirm that ME 7540 DE performs better than 184 DE over one million cycles. With these advantages, ME 7540 DE will help accelerate not only fundamental studies but also developments in real‐life applications in the DEA field. [ABSTRACT FROM AUTHOR]

As an efficient method to realize photoinduced shape memory, photothermal filler has the characteristics of economy and convenience. However, the aggregation of the photothermal filler in the matrix material will reduce the material's shape memory and mechanical properties. In this work, the photothermal filler of reduced graphene oxide (rGO)‐titanium dioxide (TiO2) was prepared by the solvothermal method and then introduced into the polycaprolactone (PCL) matrices to construct a photoresponsive actuator. Because of TiO2 is uniformly loaded on the rGO surface, rGO‐TiO2 disperses well in the composites. When the GO:TiO2 ratio of photothermal filler is 1:1, the mechanical properties of PCL‐GT‐3 are the best, and the tensile strength and elongation at break are 31.8 MPa and 239.5%, respectively, and the crosslinking material under near‐infrared light has a good photothermal effect. Due to the induced difference between the in‐plane stress of the surface and the volume layer, the shape transformation can be controlled by very low energy (808 nm, 700 mW near‐infrared laser). The scheme of controlling the properties of the photoinduced shape memory material by changing only the filler type is conducive to commercial application. [ABSTRACT FROM AUTHOR]

A new piezoelectric actuator with flexible mechanism using stick-slip principle based on the frog-leg inspiration is developed in this work. It utilizes bipedal design, and the slider can be driven by only one foot or two feet alternately, which depends on the exciting situation of the used two PZT stacks. The extension of the PZT stack can be transmitted into the vertical and horizontal deformations on two driving feet due to the frog-leg inspiration. They are used to press and actuate the slider. The configuration of this actuator is presented and its working principle is illustrated. Finite element simulation is carried out to investigate the statics performance. A prototype of the proposed actuator is fabricated and series of mechanical output characteristics are measured. The results demonstrated that the proposed actuator obtained the output velocity of 4.23 mm/s when the voltage and frequency were 100 V and 400 Hz. The maximum vertical loading capacity was 9 N under the voltage of 100 V. The corresponding results in this work validated the feasibility of the proposed bipedal piezoelectric actuator with flexible mechanism based on the frog-leg inspiration. [ABSTRACT FROM AUTHOR]

Structurally ordered soft materials that respond to complementary stimuli are susceptible to control over their spatial and temporal morphostructural configurations by intersectional or combined effects such as gating, feedback, shape‐memory, or programming. In the absence of general and robust design and prediction strategies for their mechanical properties, at present, combined chemical and crystal engineering approaches could provide useful guidelines to identify effectors that determine both the magnitude and time of their response. Here, we capitalize on the purported ability of soft intermolecular interactions to instigate mechanical compliance by using halogenation to elicit both mechanical and photochemical activity of organic crystals. Starting from (E)‐1,4‐diphenylbut‐2‐ene‐1,4‐dione, whose crystals are brittle and photoinert, we use double and quadruple halogenation to introduce halogen‐bonded planes that become interfaces for molecular gliding, rendering the material mechanically and photochemically plastic. Fluorination diversifies the mechanical effects further, and crystals of the tetrafluoro derivative are not only elastic but also motile, displaying the rare photosalient effect. [ABSTRACT FROM AUTHOR]

Soft actuators are gaining significant attention due to their ability to provide realistic tactile sensations in various applications. However, their soft nature makes them vulnerable to damage from external factors, limiting actuation stability and device lifespan. The susceptibility to damage becomes higher with these actuators often in direct contact with their surroundings to generate tactile feedback. Upon onset of damage, the stability or repeatability of the device will be undermined. Eventually, when complete failure occurs, these actuators are disposed of, accumulating waste and driving the consumption of natural resources. This emphasizes the need to enhance the durability of soft tactile actuators for continued operation. This review presents the principles of tactile feedback of actuators, followed by a discussion of the mechanisms, advancements, and challenges faced by soft tactile actuators to realize high actuation performance, categorized by their driving stimuli. Diverse approaches to achieve durability are evaluated, including self-healing, damage resistance, self-cleaning, and temperature stability for soft actuators. In these sections, current challenges and potential material designs are identified, paving the way for developing durable soft tactile actuators. [ABSTRACT FROM AUTHOR]

Vertical-axis wind turbines (VAWTs) are efficient tools for harvesting wind energy, especially in urban areas; however, aerodynamic losses owing to dynamic stall and negative torque reduce their efficiency. Therefore, it is necessary to use flow-control methods for VAWTs. In the present study, a two-dimensional VAWT is numerically modeled and simulated. Subsequently, a novel combined actuator is proposed to improve the performance of VAWT. This novel combined actuator included plasma actuators and deflector plate as active and passive actuators, respectively. First, 16 cases were examined to determine the optimal deflector angle and distance. In the best case, the deflector with an angle of 45° and a radius ratio of 3.3 increased the power coefficient by 13.37% compared to the open rotor. Then, the effect of the combined use of the deflector and plasma actuator was investigated. The results showed that the activation of the plasma actuator from an azimuth angle of 55° to 145° increased the power coefficient by 45.68% in comparison to the open rotor. Considering the energy consumed by actuators, the net energy produced by the VAWT per rotation cycle increased by 26.72% compared to the open rotor. [ABSTRACT FROM AUTHOR]

The load-adaptive behavior of the muscles in the human musculoskeletal system offers great potential for minimizing resource and energy requirements in many technical systems, especially in drive technology and robotics. However, the lack of knowledge about suitable technical linear actuators that can reproduce the load-adaptive behavior of biological muscles in technology is a major reason for the lack of successful implementation of this biological principle. In this paper, therefore, the different types of linear actuators are investigated. The focus is particularly on artificial muscles and rope pulls. The study is based on literature, on the one hand, and on two physical demonstrators in the form of articulated robots, on the other hand. The studies show that ropes are currently the best way to imitate the load-adaptive behavior of the biological model in technology. This is especially illustrated in the context of this paper by the discussion of different advantages and disadvantages of the technical linear actuators, where ropes, among other things, have a good mechanical and control behavior, which is very advantageous for use in an adaptive system. Finally, the next steps for future research are outlined to conclude how ropes can be used as linear actuators to transfer load-adaptive lightweight design into technical applications. [ABSTRACT FROM AUTHOR]

In this work, a problem is formulated and a mathematical model for numerical calculation of the effective piezoelectro-elastic characteristics of macro fiber composite (MFC) structures is developed. At the macrolevel, constitutive relations are obtained for composite under longitudinal and transverse piezoelectric loading taking into account the conductivity of phases. The electromagnetic coupling coefficients of the MFC actuator have been determined depending on the volume fraction of the piezoelectric phase in the form of PZT4 fibers and epoxy matrix. The influence of the design piezo actuator parameters on the MFC piezo actuator efficiency is shown. [ABSTRACT FROM AUTHOR]

Flexible intelligent actuators with the characteristics of flexibility, safety and scalability, are highly promising in industrial production, biomedical fields, environmental monitoring, and soft robots. Nanocomposite hydrogels are attractive candidates for soft actuators due to their high pliability, intelligent responsiveness, and capability to execute large‐scale rapid reversible deformations under external stimuli. Here, the recent advances of nanocomposite hydrogels as soft actuators are reviewed and focus is on the construction of elaborate and programmable structures by the assembly of nano‐objects in the hydrogel matrix. With the help of inducing the gradient or oriented distributions of the nanounits during the gelation process by the external forces or molecular interactions, nanocomposite hydrogels with ordered structures are achieved, which can perform bending, spiraling, patterned deformations, and biomimetic complex shape changes. Given great advantages of these intricate yet programmable shape‐morphing, nanocomposite hydrogel actuators have presented high potentials in the fields of moving robots, energy collectors, and biomedicines. In the end, the challenges and future perspectives of this emerging field of nanocomposite hydrogel actuators are proposed. [ABSTRACT FROM AUTHOR]

The nonlinearity between input current and output displacement in giant magnetostrictive actuator (GMA) systems seriously destabilizes the system, and the inaccuracy of existing integer-order differential modeling makes it difficult to predict and control the output of the system. Therefore, the study of more accurate GMA nonlinear dynamical behavior is of theoretical guidance for system scheme design. Firstly, based on the working principle of GMA and Caputo's fractional-order differential theory, a GMA fractional nonlinear dynamics model is developed; secondly, the amplitude–frequency response equations and stability conditions at the main resonance of the system are solved by applying the averaging method; finally, the effects of fractional order and damping coefficients on the nonlinear dynamics behavior of the system are investigated by means of the power series method. The conclusions of the study serve for the scheme design of the system as well as the stability analysis of the system. [ABSTRACT FROM AUTHOR]

This paper focuses on soft actuators that utilize fluid power to drive soft robots and describes their features and applications. First, it discusses how soft actuators function as elemental technology in robots. This is followed by an introduction to the driving principle and features of fluid-driven soft actuators. It also classifies these soft actuators based on the fluid power source and the active mode of operation. Furthermore, an overview is provided on the materials employed in soft actuators and the control and evaluation methods for them. Finally, currently reported applications of these soft actuators, such as wearable devices, grippers, and bio-inspired robots, are presented. [ABSTRACT FROM AUTHOR]

Soft robots require soft actuators for mobility and functionality. To integrate multiple functions in a limited space, researchers are developing multifunctional soft actuators with several functions integrated in one device. This study successfully demonstrates an electroluminescent (EL) soft actuator, a single device with both light‐emitting and actuating capabilities, using liquid dielectric and uniformly dispersed EL phosphor particles. EL phosphor particles are copper‐doped zinc sulfide (ZnS) particles doped with copper. The work is able to disperse the ZnS particles uniformly in the oil by coating the ZnS particles with silica, ensuring consistent luminescence across the device's active area. The performance of the soft actuator is notable, with a strain of 25% and a maximum EL intensity of 23 cd m−2 for a single actuator. When stacking multiple actuators, the intensity exceeds 29 cd m−2. The findings suggest that EL actuator devices will be valuable smart components for soft robots and interactive sensors. They can effectively represent external stimuli through color signals, expanding the capabilities of these systems. [ABSTRACT FROM AUTHOR]

In this study, the photothermal performance of lignin-based nanospheres was investigated. Subsequently, a photothermal actuator was prepared using lignin-based carbon nanospheres (LCNSs). The results demonstrated that LCNSs exhibited an impressive photothermal conversion efficiency of up to 83.8%. This extreme efficiency significantly surpasses that of lignin nanospheres (LNSs) and covalently stabilized LNSs (HT-LNSs). As a structural material, a hydrophobic coating was effectively engineered by LCNSs on the filter paper, achieving a water contact angle of 151.9° ± 4.6°, while maintaining excellent photothermal effects (with a temperature increment from room temperature to 138 °C in 2 s). When employing hydrophobic filter paper as the substrate for the photothermaldriven actuator, under the influence of a 1.0 W/cm2 power–density NIR laser, the material exhibited outstanding photothermal actuation, achieving speeds up to 16.4 mm/s. In addition, the direction of motion of the actuator can be adjusted in accordance with the location of the NIR light irradiation. This study offers valuable perspectives on the application of LNSs for highvalue applications and the development of innovative photothermal-driven actuators. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO2) stands out for its versatility in numerous applications, thanks to its unique reversible insulator-to-metal phase transition. This transition can be initiated by various stimuli, leading to significant alterations in the material's characteristics, including its resistivity and optical properties. As the interest in the material is growing year by year, the purpose of this review is to explore the trends and current state of progress on some of the applications proposed for VO2 in the field of sensors and actuators using literature review methods. Some key applications identified are resistive sensors such as strain, temperature, light, gas concentration, and thermal fluid flow sensors for microfluidics and mechanical microactuators. Several critical challenges have been recognized in the field, including the expanded investigation of VO2-based applications across multiple domains, exploring various methods to enhance device performance such as modifying the phase transition temperature, advancing the fabrication techniques for VO2 structures, and developing innovative modelling approaches. Current research in the field shows a variety of different sensors, actuators, and material combinations, leading to different sensor and actuator performance input ranges and output sensitivities. [ABSTRACT FROM AUTHOR]

One of the effective methods of non-destructive testing of structures is active vibration diagnostics. This approach consists of the local dynamic impact of the actuator on the structure and the registration of the vibration response. Testing of massive reinforced concrete structures is carried out with the use of actuators, which are able to create sufficiently high-impact loads. The actuators, which are based on piezoelectric elements, cannot provide a sufficient level of force and the areas where it is possible to register the vibrations excited by such actuators are quite small. In this paper, we propose a variant of a piezoactuator with attached mass, which ensures an increase in the level of dynamic impact on the structure. The effectiveness of this version is verified by numerical modeling of the dynamic interaction of the actuator with a concrete slab. The simulation was carried out within the framework of the theory of elasticity and coupled electroelasticity. An algorithm for selecting the value of the attached mass is described. It is shown that when vibrations are excited in a massive concrete slab, an actuator with an attached mass of 1.3 kg provides a 10,000-fold increase in the force compared to an actuator without attached mass. In the pulse mode, a 100-fold increase in force is achieved. [ABSTRACT FROM AUTHOR]

Component failures can lead to performance degradation or even failure in multi-agent systems, thus necessitating the development of fault diagnosis methods. Addressing the distributed fault diagnosis problem in a class of partial differential multi-agent systems with actuators, a fault estimator is designed under the introduction of virtual faults to the agents. A P-type iterative learning control protocol is formulated based on the residual signals, aiming to adjust the introduced virtual faults. Through rigorous mathematical analysis utilizing contraction mapping and the Bellman–Gronwall lemma, sufficient conditions for the convergence of this protocol are derived. The results indicate that the learning protocol ensures the tracking of virtual faults to actual faults, thereby facilitating fault diagnosis for the systems. Finally, the effectiveness of the learning protocol is validated through numerical simulation. [ABSTRACT FROM AUTHOR]

Organohydrogels composed of immiscible hydrophilic and hydrophobic components have outstanding advantages in environmental adaptability, thus exhibiting potential applications in the fields of soft actuators, artificial sensors, energy storage devices, and so on. This paper provides a comprehensive overview of the latest developments in organohydrogels, from construction to performance and application. After a brief introduction, typical cases of organohydrogels and their construction methods are analyzed and summarized, including organohydrogels with heterogeneous networks, organohydrogels with binary solvent, emulsion‐based organohydrogels, and macroscopic hybrid gels. Then, their promising applications of soft actuators, flexible electronics, and anti‐counterfeiting platforms are outlined. Finally, the current challenges and future prospects of this emerging area are discussed. This review can be a significant reference for the development of environmentally adaptable materials and the expansion of new applications. [ABSTRACT FROM AUTHOR]

Inorganic nanoparticles have been widely used as fillers to modify dielectric elastomers to simultaneously improve mechanical and dielectric performances. Elegant interface design is crucial for achieving synergy between fillers and elastomers. Herein, we show that diborate ester polymers can both improve the interfacial compatibility between inorganic nanoparticles and elastomers and enhance the dielectric performances. The diborate ester polymers are derived from the condensation reaction between tetrakis(dimethylamino)diborane (or tetrahydroxydiborane) and a three‐armed catechol monomer. Choosing TiO2 nanoparticles as the inner core, a series of TiO2@diborate ester polymer core‐shell nanoparticles are synthesized. Density functional theory (DFT) calculations indicate that the diborate ester polymer shell tightly bonds to the surface of TiO2 through two dissociative bidentate bridging modes of the catechol monomer (absorption energy: −11.049 eV). These core‐shell nanoparticles can soften and tough polydimethylsiloxane (PDMS) and show enhanced interfacial binding affinity to PDMS than naked TiO2 nanoparticles. The fabricated composites have high dielectric constants (up to 6.8) and low dielectric losses (<0.03). The actuated strain and puncture voltage of the composites reach 25.9% and 80 V μm−1, respectively, which are much higher than those of PDMS and TiO2/PDMS. This work provides a promising route to fabricate core‐shell nanoparticles for high‐performance dielectric elastomers. [ABSTRACT FROM AUTHOR]

Sensors and actuators frequently encounter unexpected deviations from their optimal operating conditions, making their reliability an essential topic in many electric motor drives. In this paper, a comparison of structured residual synthesis methods for actuator and sensor additive fault detection and isolation (FDI) in a permanent magnet (PM) DC motor, applying two different approaches to the design of primary residuals, is presented. The first method involves a standard approach and is based on system transfer matrix synthesis. The second, more convenient approach involves the synthesis of primary residuals based on the analysis of subsystems that describe the observed system. Both methods are applicable for linear and time-invariant (LTI) systems but were successfully applied to a laboratory system that shows nonlinear behavior, time-variant properties, and is affected by a constant disturbance, thanks to the proposed technique of residual translation with the previous design of internal residuals. With the proposed method, all important performance characteristics of the residual generators such as fault sensitivity, reaction speed, and robustness are achieved. The technique can be applied to all mechatronic systems in general, whose behavior can be with satisfactory accuracy described by an LTI model. Given the transfer functions and state-space model of the system in the presence of faults in the Z domain with reduced order, presented technique is computationally efficient for embedded systems. Also, in addition to fault detection and isolation, the system can identify faults by analyzing fault sensitivities, nominal faults, and stationary residual values, making it superior for most FDI applications. A real-time experiment performed on a laboratory setup, which consists of a DC motor, an amplifier designed in the form of a linear electronic circuit, and a Compact RIO 9075 real-time processor is used to develop the FDI system, to generate residuals and confirm advantages of the proposed FDI technique. [ABSTRACT FROM AUTHOR]

Metasurface with programmable configurations has attracted tremendous attention due to their exotic abilities to manipulate electromagnetic waves. Herein, an electrically reconfigurable metasurface for frequency selective transmission is developed based on ionic polymer–metal composite (IPMC) kirigami. First, low‐voltage driven IPMC actuators with stable actuation performance are realized, and then a thermomechanical equivalent model and a numerical electromagnetic analysis model are proposed for evaluating the deformation of the IPMC actuators and predicting the electromagnetic tunable properties of the IPMC kirigami metasurfaces, respectively. Subsequently, large‐area IPMC kirigami metasurfaces are proposed and produced by using programmable nanosecond laser micro‐processing technique that endows the uniformity of the kirigami units. Finally, the electromagnetic functionalities of these IPMC kirigami metasurfaces are researched and validated by experiments and numerical simulations. Both theoretical and experimental results demonstrate that the electromagnetic transmission frequency of the fabricated IPMC kirigami metasurface with 10 × 10 units can be tuned from 19.3 to 20.8 GHz by the application of a low voltage of 3 V. Compared with the existing reconfigurable metasurfaces, the proposed IPMC kirigami metasurface demonstrates clear advantages in its compact structure, lower driving‐voltage, low‐acoustic noise, and wide working frequency range. [ABSTRACT FROM AUTHOR]

A porous actuator is prepared using a liquid crystal elastomer (LCE) loaded with metal‐organic framework (MOF) nanoparticles (MIL‐88A). While the swellable MOF additive endows the LCE actuator with nanoscale pores, after its removal by chemical etching, macroporous LCE actuator is obtained. This LCE‐MOF actuator displays several interesting features. 1) Selective etching allows the actuator in water to curl in one direction and then reverse the curling direction owing to differential water absorption of the nano‐ and macroporous layers. 2) The stretching‐induced alignment of mesogens in the actuator is little affected by the presence of MOF and substantially retained after water uptake, so that an actuation deformation can be generated either by water absorption or thermally induced order‐disorder phase transition. 3) Assisted by the UV irradiation used for polymer cross‐linking, magnetic iron oxide FeO appears to be formed after chemical etching, which allows the actuator to gain the ability to move on water surface guided by a magnet. 4) The in situ formation of magnetic iron oxide in the macroporous actuator also provides an enhanced photothermal effect, making light‐driven locomotion of the actuator more effective. The use of active porogen like MOF opens a new way to explore porous LCE actuators. [ABSTRACT FROM AUTHOR]

Summary: To realize a high‐accuracy tracking control of an electromechanical actuator in which only position signal is available, a new robust adaptive output feedback control strategy based on dual CMAC neural networks is proposed in this article. A high‐gain observer and a neural network are combined to estimate the unmeasured system states, in which a neural network is designed to estimate and compensate the system parameter estimation error and other uncertain nonlinearity to improve the performance of the traditional observer. A robust adaptive controller and another neural network are combined to decrease the impact of parameter perturbation and external disturbance and strengthen the system robustness. Lyapunov theorem is used to derive an on‐line weight adaption law for the two neural networks and an on‐line parameter adaptation law for the uncertain parameters to stabilize the system. Thus the parameter uncertainty and disturbance can be compensated with feedforward compensation technique. A nonlinear robust feedback term is designed to suppress the model compensation deviation. Considering the stronger approximation ability of CMAC basis function against RBF basis function, an improved CMAC neural network is introduced in the proposed controller. A large number of simulations and experiments show that the proposed controller has better tracking performance than many main‐stream output feedback controllers in present. [ABSTRACT FROM AUTHOR]

The recent development in smart material-based actuators are composite structures of thin film integrated SMA/PI bimorph in the view of actuator cum sensing in electromechanical systems for medical, robotics, and aerospace application. The purpose of the present work on integrated SMA/PI bimorph is to reveal their ability to perform as actuators and sensors and study on control characteristics for soft robotic, positioning, and valve applications. Vide this research paper, the SMA bimorph actuator [thin film SMA (CuAlNi)/polyimide (Kapton) bimorph] is used as actuator cum sensor for position control. Proposed a Proportional Derivative combined Variable Structure Controller (PD-VSC) to control the displacement by Joule heating actuation in two ways, which are sensor-based control and self-sensing control. From the control characteristics in from of tracking and disturbance rejection, it is concluded that the integrated CuAlNi/Kapton bimorph can be successfully implemented for soft robotic, positioning, and valve applications. [ABSTRACT FROM AUTHOR]

The attitude tracking control problem of flexible spacecraft subjected to parameter uncertainties, time-dependent external disturbances, actuator input nonlinearity, and input actuator misalignment is investigated in this paper. Explicitly, the proposed strategy addresses the input actuator misalignment and dead-zone issues that increase the controller design difficulties. Initially, a new second-order sliding mode observer (SoSMO) using an extended state approach is developed by adding a correction function to improve observer performance to estimate unwanted system perturbations. Then, a distinct SoSMO-based integral-type sliding mode control (ISMC) structure is designed in a unified manner to guarantee the asymptotic stability of the closed-loop system. Comparative numerical simulations under input actuator misalignment, the dead-zone nonlinearity, external disturbance, and inertia uncertainty are performed to illustrate the effectiveness of the proposed controller. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate the development of a fast-response soft composite actuator fabricated by mechanical mixing of silicone elastomer (matrix) and ethanol (as phase-change fluid). Joule heating generated by electrical actuation causes a liquid-vapor transition of ethanol embedded in silicone microcapsules; provides the required pressure for mimicking the natural movements. We discuss the critical design variables to improve the temperature response, chemical composition, mechanical properties, force generated, and microstructure of soft actuator. Our soft actuator produces a high load-to-weight ratio (1000 times greater than its own) using a low-voltage source (˂20V). The stability of the soft actuator under multiple working cycles would bring the application to different robotic areas. The actuator using the mechanism presented here is easy to manufacture, automate, and recyclable. It can be used in a range of robotic applications. [ABSTRACT FROM AUTHOR]

This paper is focused on asymptotic tracking control of electro-hydraulic actuator (EHA) systems subject to matched and mismatched time-varying disturbances. To counteract the matched disturbance, a novel extended state observer (ESO) is proposed to achieve asymptotic convergence of the estimation error, by incorporating the strictly positive real (SPR) Lyapunov design method and a Nussbaum function. To further suppress the mismatched disturbance, an adaptive robust integral of the sign of the error (RISE) controller is formulated in the backstepping framework based on the proposed ESO. Asymptotic tracking performance is theoretically achieved via closed-loop system stability analysis. The efficacy of the proposed control scheme is verified through comparative experiments executed on an EHA test rig. In this study, a priori bounds of the disturbances and their higher-order derivatives are no longer needed, and only one auxiliary error signal is introduced. This approach loosens the restrictions on the disturbances and reduces the design conservativeness, thus making it promising in practice. [ABSTRACT FROM AUTHOR]

A comprehensive RFD-FTC-DCA system is proposed for the hypersonic vehicle with saturation constraints to resist the control surface damage, actuator faults, disturbances and parameter perturbation. Firstly, the hypersonic vehicle fault model is established. Secondly, the robust fault detection (RFD) observer is designed to detect the control surface damage and actuator faults accurately under the influences of disturbances and parameter perturbation. Thirdly, the fault-tolerant control (FTC) law is designed to resist the control surface damage, actuator faults, disturbances and parameter perturbation simultaneously. Finally, a dynamic control allocation (DCA) algorithm is designed to reallocate the FTC law and limit the deflection angle and velocity within saturation constraint. The comparison simulation results are presented to demonstrate that the RFD observer can detect the faults accurately and reduce false alarm rates effectively, the FTC law can resist the control surface damage, actuator faults, disturbances and parameter perturbation simultaneously, and the tracing errors of attack angle, side-slip angle and roll angle are only $ \pm 0.7^\circ $ ± 0.7 ∘ , $ \pm 0.2^\circ $ ± 0.2 ∘ and $ \pm 1.5^\circ $ ± 1.5 ∘ , respectively, and the DCA algorithm can reallocate the FTC law and limit the deflection angle and velocity within saturation values. [ABSTRACT FROM AUTHOR]

This paper introduces an innovative adaptive nonsingular Second-Order Terminal Sliding Mode (SOTSM) control strategy specifically designed to stabilise disturbed nonlinear Cyber-Physical Systems (CPSs) within a finite timeframe. Unlike the conventional methods, our approach incorporates a novel nonlinear sliding surface that eliminates the need for a reaching step, significantly enhancing the system's robustness. Novel real-time adaptive control laws are developed to cope with external perturbations, time-varying delays, and cyber-attack on actuators without requiring the identification of their upper bounds. The proposed method ensures robust performance for time-varying delayed and disturbed nonlinear CPSs, even in the face of strong cyber-attacks targeting the actuators. Moreover, the proposed method has distinct advantages: it delivers rapid response times, enhanced flexibility, exceptional accuracy, smooth and robust control devoid of transient fluctuations or chattering, and ensures finite-time convergence. Simulation results comprehensively demonstrate the superior efficiency and success of our proposed technique compared to traditional methods such as integral Sliding Mode Control (SMC) and State-Feedback Control (SFC) schemes. [ABSTRACT FROM AUTHOR]

Adaptive high-rise buildings can achieve significantly reduced resource consumption by incorporating actuators, sensor systems, and a control unit into the structure to compensate for the reduced stiffness. A vital step toward the wide real-world viability of this concept is ensuring the long-term operational reliability of adaptive buildings even in case of components malfunctioning. This article presents a comprehensive mechanical model of a large-scale adaptive high-rise structure incorporating various sensor systems as well as different actuation principles. As a basis for the simulative validation under critical load scenarios, a detailed model for wind disturbances is derived, accounting for time-variant velocity and direction. A parity space-based fault diagnosis scheme is employed for the reliable diagnosis of faulty sensors and actuators. Based upon the fault diagnosis, a reconfiguration strategy for estimation and control in adaptive structures is proposed. Assembling these components yields a fault-tolerant control loop that automatically adapts to the emergence of faults in sensors and actuators. In exemplary simulation scenarios, the proposed approach is demonstrated to be effective, largely mitigating the faults' impact and recovering the nominal performance. [ABSTRACT FROM AUTHOR]

This paper illustrates an experimental activity for the closed-loop position control of an actuator made using shape memory alloy (SMA) wire. A solution with the self-sensing effect was implemented to miniaturize the systems, i.e., without external sensors. A proportional control algorithm was initially used, demonstrating the idea's feasibility; the wire can behave simultaneously as an actuator and sensor. An experimental investigation was subsequently conducted for the optimization of the developed actuator. As for the material, a Flexinol wire, Ni-Ti alloy, with a diameter of 0.150 mm and a length of 200 mm, was used. Preliminarily, characterization of the SMA wire at constant and variable loads was carried out; the characteristics detected were elongation vs. electric current and elongation vs. electrical resistance. The control system is PC based with a data acquisition card (DAQ). A drive board was designed and built to read the wire's electrical resistance and power it by pulse width modulation (PWM). A notable result is that the actuator works with good precision and in dynamic conditions, even when it is called to support a load up to 65% different from that for which the electrical resistance–length correlation has previously been experimentally obtained, on which the control is based. This opens up the possibility of using the actuator in a counteracting configuration with a spring, which makes hardware implementation and control management simple. [ABSTRACT FROM AUTHOR]