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In this work, the fabrication of Rochelle salt based piezoelectric structures is illustrated. Structures composed of paper and Rochelle salt are easily manufactured using simple processes. Both manufacturing and the material itself are environmental friendly. Additionally Rochelle salt is biocompatible. In the paradigm of a cleaner piezoelectric technology, the fabrication of active sensing or actuating devices is developed. Thus processing method, material and piezoelectric properties have been studied: (1) pure crystals are used as acoustic actuator, (2) properties of paper impregnated with Rochelle salt are detailed, (3) charge generation is demonstrated on the impregnated material. Actuating and sensing devices are reported in order to highlight the potential of this green piezoelectric material. [ABSTRACT FROM AUTHOR]

Abstract: Piezoelectricity is one major actuating mechanism of cellulose-based electro-active paper (EAPap). In order to increase the piezoelectricity of EAPap, wet drawing method with different stretching conditions was introduced in the fabrication process of cellulose film. Structural and mechanical characterizations of wet drawn and stretched cellulose film were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), high voltage electron microscope (HVEM) and mechanical pulling test setup. From the piezoelectric charge constant measurement, it was revealed that the performance of EAPap was sensitive to the drawing ratio of cellulose film and its material orientation. We found that optimized alignment direction along the cellulose fibers and drawing ratio during wet drawing process were very critical parameters to improve electro-mechanical properties of EAPap. Also we conclude that the simple wet drawing method is a very effective fabrication method to enhance the mechanical stiffness and the piezoelectricity of EAPap. [Copyright &y& Elsevier]

Abstract: Good cross-directional control of sheet variables in a paper machine depends on a number of factors. One such factor is the correct alignment of actuators with their corresponding responses. The alignment changes with time either locally or across the whole paper sheet due to a variety of reasons. In this paper, we provide an online mapping technique based on estimating the cross-correlation between actuator movement and the measurements. This procedure involves two steps–in the first step (called alignment monitoring) we determine if the current mapping is wrong at any CD position, and in the second step (called re-mapping), the alignment of actuators is corrected. The main advantage of this method is in its ability to re-align under closed loop conditions with minimal operational disruption. [Copyright &y& Elsevier]

The cross-directional model predictive control (CD-MPC) tuning problem is investigated for multiple-array paper-making process with parametric uncertainty. A systematic spatial tuning method is proposed to tune the penalty matrices such that the harmful high frequency elements in each actuator profile can be eliminated. A multivariable temporal filter is employed to adjust the output references, and a temporal tuning algorithm is developed for the filter parameters to achieve the pre-specified 2 σ performance indices. The computational time of the proposed methods is reduced via event-based sampling strategy. The effectiveness of the techniques is shown via a CD system from paper-making industry. [ABSTRACT FROM AUTHOR]

Paper-based analytical devices introduce an innovative platform technology for fluid handling and analysis, with wide range of applications, promoting low cost, ease of fabrication/operation and equipment independence. This review gives a general overview on the fabrication techniques reported to date, revealing and discussing their weak points as well as the newest approaches in order to overtake current mass production limitations and therefore commercialisation. Moreover, this review aims especially to highlight novel technologies appearing in literature for the effective handling and controlling of fluids. The lack of flow control is the main problem of paper-based analytical devices, which generates obstacles for marketing and slows down the transition of paper devices from the laboratory into the consumers' hands. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (rGO) papers prepared by simple self-assembly process were used as electrode material for the fabrication of bimorphic electrical actuators. Initially, the structural studies of the rGO paper confirmed the formation of graphitic structure. The ionic gel electrolyte was prepared separately and used to couple the two rGO paper electrodes. This forms the tri-layered structure as an actuator, the displacement was measured by varying the applied potential with respect to time. The actuation properties were extended for both photon as well as electronic conducting gel electrolyte. The experimental results suggest that the flexible rGO paper can be used for electronic actuators. [ABSTRACT FROM AUTHOR]

We report a novel biodegradable piezoelectric composite fabricated from paper and the piezoelectric salt, sodium potassium tartrate tetrahydrate (Rochelle salt, which we term PiezoSalt). The piezoelectric composite is non-toxic and is fabricated free of environmentally harmful solvents by impregnating PiezoSalt into a paper matrix through the crystallization of a concentrated PiezoSalt brine solution. The composite exhibits an effective piezoelectric constant between 3 and 25 pC N −1 , dielectric constant of 7, mass density of 625 kg m −3 , and a Young’s modulus between 7 and 8 GPa. When directly actuated, cm-scale cantilevers consisting of PiezoSalt paper produced clearly audible sound waves, illustrating one potential application. PiezoSalt paper composite provides a scalable, high throughput approach for biodegradable sensors and transducers with unsurpassed environmentally friendly processing. [ABSTRACT FROM AUTHOR]

• Graphene oxide/reduced graphene oxide paper was obtained by Ultraviolet laser. • The reduction degree of graphene oxide can be adjusted by changing the laser power. • The as-prepared papers exhibit anisotropically deformation triggered by ethanol vapor. This report aims to illustrate a highly effective method to obtain a kind of graphene oxide (GO)/reduced graphene oxide (RGO) paper by Ultraviolet (UV) laser direct writing method. Due to removing the oxygen-containing groups and introducing the layered micro-nano structures on one side of the GO film. The as-prepared GO/RGO papers exhibit anisotropically deformation triggered by ethanol vapor and could enable the potential applications for stimuli-response actuators. [ABSTRACT FROM AUTHOR]

Abstract: The construction of electromechanical actuator has been achieved by using the conducting polypyrrole films deposition onto a gold-coated cellophane paper. This is probably the first report of this type of paper actuator. The conducting polypyrrole was electro-generated using either galvanostatic or potentiostatic conditions at 0.5mA/cm2 current density or 0.7V applied potential, respectively. The two types of actuators were constructed, namely: (1) Ppy/cellophane bi-layer; (2) Ppy/cellophane paper/Ppy tri-layer. These actuators showed a reversible and reproducible displacement in acetonitrile solution containing LiClO4 (1M). The maximum displacement of 9.1mm was recorded for tri-layer device and 3.5mm for bi-layer device in 1M LiClO4 acetonitrile solutions. The results obtained in acetonitrile solution containing 1M LiClO4 shows that the actuator requires very low excitation voltage of 0.2MVm−1. The mechanism for this paper actuation phenomenon is addressed in this paper. [Copyright &y& Elsevier]

Abstract: Electro-active papers (EAPap) made with cellulose have been known as a biomimetic actuator material according to their merits in terms of large bending deformation, low actuation voltage, ultra-lightweight, and biodegradability. This out-of-plane bending deformation is useful for achieving flapping wings, micro-insect robots, and smart wallpapers. On the other hand, in-plane strains, such as extension and contraction of EAPap materials are also promising for artificial muscle applications since the Young''s modulus of EAPap materials is large. This paper first reports the experimental investigation of the in-plane strain of EAPap materials in the presence of electric fields. The EAPap samples preparation and the in-plane strain measurement system are explained. The test results are shown in terms of electric field, frequency and the orientation of the samples. The power consumption and the strain energy of EAPap samples are discussed. Although there are still unknown facts in EAPap materials, this in-plane strain may be useful for artificial muscle applications. [Copyright &y& Elsevier]

Abstract: This paper investigates the performance of electro-active paper (EAPap) actuators with thickness variation. EAPap made with cellulose paper, is attractive for biomimetic actuators due to its characteristics in terms of lightweight, biodegradable, dry condition, large displacement output, low actuation voltage and low power consumption. EAPap actuators exhibit a bending deformation in the presence of electric field. However, the performance is sensitive to the thickness of the EAPap material because the thickness is associated with the bending stiffness that strongly affects the bending deformation and the force output of the actuator. Thus, the performance of EAPap actuators that have three different samples of 20, 30, and 40μm thicknesses is tested in terms of tip displacement, blocked force, electrical power consumption, and the efficiency. The sample preparation and the test methods are addressed. The resonance frequency and the bending stiffness are associated with the thickness of the EAPap actuator, and there is an optimum thickness for the best performance of the EAPap actuators. The mechanical output power and the efficiency at an optimal thickness are drastically improved comparing with the previous thickness case. [Copyright &y& Elsevier]

Abstract: Functionalized multi-walled carbon nanotubes (F-MWNTs) were blended with cellulose solution to fabricate F-MWNTs/cellulose electro-active paper (EAPap) actuators. Cellulose was dissolved in LiCl/N,N-dimethylacetamide (DMAc) solution by solvent exchange process and blended with F-MWNTs to make F-MWNTs/cellulose EAPap actuators. Their characteristics were investigated by taking X-ray diffractometer (XRD), SEM, Young''s modulus measurement and water retention measurement. Actuator performance of F-MWNT/cellulose EAPap was evaluated in terms of bending displacement, resonance frequency, output force and electrical power consumption. A large bending displacement of 4.5mm and improved output force of the actuator were obtained. The actuation principle of cellulose EAPap was more likely based on ion migration effect, especially in humid condition. More explanation about the characteristics, actuation principle and performance of actuator is introduced. [Copyright &y& Elsevier]

Abstract: The effect of heat treatment on the structure, piezoelectricity and actuation behavior of cellulose electroactive-paper actuators was studied by infrared spectroscopy, piezoelectricity measurement and the tip displacement test. After heat treatment at 60°C for 2h, the piezoelectric coefficient (d 31) was enhanced nearly 10-fold as compared to that of non-heat-treated films. However, when the treatment temperature was raised above 60°C the piezoelectric coefficients were higher than the non-treated film but lower than that of film treated at 60°C. Infrared and UV–visible spectroscopy suggested that there were changes in chemical structure at higher treatment temperatures. Furthermore, the tip displacement tests performed on the actuators also showed almost same trend as that of the piezoelectric constant. [Copyright &y& Elsevier]

Abstract: This paper presents a blocked force measurement of electro-active paper (EAPap) with a simple configuration and high accuracy. Blocked force is a force at the tip of a bending actuator when the tip is fixed. A micro-balance with a fixture is used to measure the blocked force of EAPap bending actuator. The measurement is conducted with dc electric fields. A theoretical blocked force is calculated by using the cantilever beam model, and the measured blocked force is compared with the calculated result. Comparing the measured blocked force with the calculated result shows a good agreement. This force measurement method is simple and accurate, and can be applied for measuring blocked forces of EAP actuators. [Copyright &y& Elsevier]

Abstract: Covalently bonded multi-walled carbon nanotubes (MWNTs) to cellulose were used to fabricate electro-active paper (EAPap) and its mechanical properties as well as actuator performance were investigated. A cellulose solution was prepared by dissolving cotton pulp in LiCl/N,N-dimethylacetamide (DMAc) solution. MWNTs were covalently bonded to cellulose by reacting MWNTs-imidazolides with cellulose solution. Using this, MWNTs/cellulose (M/C) EAPap was fabricated with different weight percents of MWNTs. This EAPap was analyzed by Fourier-transform IR, X-ray diffraction and X-ray photoelectron spectroscopy and their Young''s modulus was measured. The actuator performance of M/C EAPap was evaluated in terms of bending displacement, resonance frequency and electrical power consumption depending on the weight percent of MWNTs and humidity levels. Due to the presence of covalent bonds between MWNTs and cellulose, the Young''s modulus of M/C EAPap was remarkably enhanced more than the MWNTs blended EAPap. The enhanced Young''s modulus was strongly associated with the crystallinity change of cellulose. The actuator performance of M/C EAPap was improved also. More explanation about the characteristics, actuation principle and actuator performance of M/C EAPap actuator is addressed. [Copyright &y& Elsevier]

[Display omitted] • The method of pencil drawing is employed to fabricate the multi-responsive actuator. • The multi-responsive actuator can be driven by light or humidity. • The T- and strip-shaped actuators are designed by the surface patterning method. • The helix-shaped actuator created by the shaping method performs twisting motion. Over the past few years, researchers have focused on stimulus-responsive soft materials and their applications in the design of soft actuators. The key factor of the soft actuators to achieve various applications is the programmable and controllable shape deformations. Here, a versatile and simple surface patterning method consisted of pencil drawing and pasting polymer films is proposed to design the soft actuators with programmable deformations. Due to the thermal expansion effect and the hygroexpansion effect, the graphite paper/polymer actuator performs a bending motion with a curvature of 1.4 cm−1 under light irradiation and 1.2 cm−1 under high humidity. Owing to the convenience of the patterning method, different patterns on both two surfaces of the paper substrate are designed without effort. Thus, through tuning the grayscale of the graphite on one surface of the paper, three types of T-shaped actuators can be obtained with different deformations under light irradiation. In addition, by pencil drawing or hydrophobically modifying specific patterns on the two surfaces of the paper, three types of strip-shaped actuators are also proposed to demonstrate that different 3D shape deformations can be obtained under different stimuli. Finally, a helix-shaped actuator inspired by the natural plant tendrils is fabricated by the thermal-induced shaping method. The helix-shaped actuator performs twisting/untwisting motion under different stimuli and can be used as a grasping robot. These results demonstrate the diversified programmability of the graphite paper/polymer actuator. Hence, the simple and versatile programming methods of soft actuators have great potential to be used in the field of biomimetic applications, intelligent robotics, and lab-on-paper devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • The flytrap-inspired soft actuator realizes sense-drive-feedback integration. • Large deformation (1.2 cm−1) and low voltage consumption (4 V) are achieved. • Objects can be sensed by the device with high sensitivity (3.22 kPa−1). • The device can sense (both weight and volume), grasp, and move the objects. • The device enables intelligent human–machine interaction. In recent years, soft actuators have attracted much attention due to their potential application in soft robots, artificial muscles, and human–machine interaction interfaces. However, it is still challenging to achieve intelligent integration of sensing and driving functions. Herein, inspired by natural flytrap, a novel soft intelligent actuator is developed based on sense-drive-feedback integration in response to pressure stimuli. The actuator is fabricated using MXene/CNT paper to construct sensing and driving modules. In terms of actuation, the Joule heating effect and heterogeneous composites endow the device with large deformation under low-power consumption. As for sensing, highly conductive MXene/CNT paper contributes to superior sensitivity over a large linear range. Thereon, a portable soft tactile actuator is constructed to grasp and manipulate objects based on manual operation. Moreover, a soft petal actuator that mimics the feeding action of flytrap was prepared to actively sense and grasp external objects, where its weight and size can also be reflected in real time. Furthermore, integration of the actuators with human hands can enable its real-time control via bending the fingers. Therefore, this study provides a significant paradigm to construct intelligent soft tactile actuators towards various practical applications. [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanotube papers have many potential applications from actuators to electrodes. Cross-linked papers with embedded nanoparticles are now being investigated for use in these applications. Here we report on the development of piezoelectric multi-walled carbon nanotube paper. The piezoelectric effect of the paper was enhanced by four orders of magnitude by embedding zinc oxide nanoparticles into the carbon nanotube network, resulting in a simple method for producing flexible piezoelectric carbon nanotube paper. [Copyright &y& Elsevier]

• A novel fault-tolerant controller has been developed for the attitude control of rigid spacecraft based on Q-learning. • This controller obviates the necessity for actuator fault data or extensive fault knowledge. • The controller stability analysis and controller implementation are discussed. This paper presents a novel active fault-tolerant control (FTC) scheme based on reinforcement learning (RL) for rigid spacecraft operating in challenging conditions with simultaneous actuator faults and external disturbances. Initially, the paper outlines the dynamics of a rigid spacecraft afflicted by actuator faults and subject to external disturbances. Subsequently, an observer is designed to swiftly detect actuator faults, ensuring a timely response to fault occurrences. An indirect fault estimator is then employed to estimate the total faults affecting the system. Based on the estimated total faults, the proposed decision mechanism switches the controller from the nominal to the fault-tolerant controller. The proposed fault-tolerant controller is model-free and utilizes the Q-learning algorithm. This Q-learning-based fault-tolerant controller can be implemented online without relying on explicit system models or actuator fault details. Notably, this innovative controller operates independently from fault detection and identification (FDI), utilizing data extracted from system trajectories. The stability of the fault-tolerant controller is established using Lyapunov techniques, providing rigorous validation of its effectiveness in maintaining system stability and achieving satisfactory performance. The performance and adaptability of the proposed approach are assessed through comprehensive simulation studies, emphasizing its capacity to enhance spacecraft fault tolerance in demanding operational scenarios. [ABSTRACT FROM AUTHOR]

This paper studies the leader–follower consensus problem for nonlinear multi-agent systems with actuator saturation by adaptive event-triggered scheme. This adaptive mechanism allows parameters in triggered mechanism to change automatically compared to fixed ones in traditional strategies. The paper introduces two distinct approaches to address the issue of saturation. The first approach is sector bounded condition, while the second relies on convex hull representation. Compared with the former one, the latter one can reduce the conservatism of controller design effectively. Furthermore, it is assumed that the nonlinear function adheres to incremental quadratic limitations, thereby offering a more comprehensive depiction of its nonlinear properties. Finally, the validity of the proposed approaches is demonstrated by one numerical example in the background of mechanical systems. • The leader–follower consensus problem for nonlinear multi-agent systems with actuator saturation is studied. • Adaptive event-triggered mechanism for multi-agent systems is considered. • Two methods for dealing with saturation are proposed, one is sector bounded condition and another is convex hull representation. • The nonlinear function is supposed to satisfy incremental quadratic constraints. [ABSTRACT FROM AUTHOR]

Semiconductor photolithography equipment requires an actuation system that can satisfy high acceleration and precision demands on the nanoscale in order to operate with high throughput and efficiency. Reluctance actuators, which offer greater acceleration and force output than conventional Lorentz actuators, are one option. The photolithography technique uses a floating stage with air bearings to reduce friction; nonetheless, vibration transfer is not completely prevented, potentially causing misalignment and asymmetries between the actuator components. The output force can be significantly impacted by unequal offsets between the mover and stator. In the paper that follows, a technique for calculating the force of various asymmetrical instances for the C-core reluctance actuator is demonstrated. This paper looks into the effect of rotational offsets in all rotational degrees of freedom occurring simultaneously. Previously, only each degree of freedom was analyzed. Analytical models are developed and compared to Comsol Multiphysics (COMSOL) simulations, and experimental findings show accuracy to be within almost 10% for the ranges examined. The findings presented can allow for future control systems to be designed to counteract multi-axial asymmetric issues. • Derived an analytical equation of the output force under multi-axial angular offsets. • Implemented a FEM setup to further tune the analytical output force equation. • Tested experimentally on multi-axial offset cases to verify the analytical model. [ABSTRACT FROM AUTHOR]

This paper investigates the fault-tolerant attitude control problem for a spacecraft with actuator faults using an event-triggered-based concurrent-learning control (CLC) approach. A concurrent-learning controller, updating itself through previous control signal values to generate the current control signal, is studied in this paper. The concurrent-learning controller is designed under an event-triggered policy to compensate for the actuator's data transmission constraints caused by bandwidth limit. In addition, a robust fault observer is designed to facilitate the concurrent-learning controller in compensating for the actuator faults. The key feature of the given approach is in the simplicity of control structure to stabilize spacecraft attitude considering actuator faults, model uncertainty, actuators' dynamics effect, and data transmission; simulation results show the proposed approach's efficiency. [ABSTRACT FROM AUTHOR]

This paper proposes a new adaptive super-twisting global integral terminal sliding mode control algorithm for the trajectory tracking of autonomous robotic manipulators with uncertain parameters, unknown disturbances, and actuator faults. Firstly, a novel global integral terminal sliding mode surface is designed to ensure that the tracking errors of autonomous robotic manipulators converge to zero in finite time and the global robustness of the system is also enhanced. Then a new adaptive method is devised to deal with the adverse effect of nonlinear uncertainty. To suppress the chattering phenomenon, the adaptive super-twisting algorithm is used in this paper, which can ensure that the control torque is a continuous input signal. Based on the adaptive mechanism, the adaptive super-twisting global integral terminal sliding mode controller is developed to provide superior control performance. The stability analysis of the system is demonstrated by using the Lyapunov method. Ultimately, the effectiveness of the control scheme is confirmed by a simulation study. • A novel adaptive finite-time global integral terminal sliding mode control scheme is designed. • A novel global integral terminal sliding mode surface is proposed to ensure faster convergence and better global robustness. • A novel adaptive law is designed to adjust the estimation parameters according to the change of system state to avoid overestimation. • The actuator fault is considered to make the proposed control logic more suitable for practical applications. [ABSTRACT FROM AUTHOR]

This paper investigates the attack estimation and state reconstruction problem for linear cyber–physical systems with state delay and simultaneous sensor and actuator attacks. Reduced-order observer is designed for the augmented system to simultaneously estimate the actuator attack, sensor attack and the state of system. By adopting the double integral term into the Lyapunov–Krasovskii functional and decomposing the cross term, the delay-dependent results are obtained. The method proposed in this paper can accurately estimate the state, actuator and sensor attacks simultaneously without additional design. Compared with the previous method, the time delay information is fully utilized and the conservation is greatly reduced. Finally, the correctness of the results is verified by simulation. • Delay-dependent conditions are obtained for cyber–physical systems with state delay. • Both attack estimation and state reconstruction are considered. • Actuator attacks, sensor attacks and system state are estimated simultaneously. [ABSTRACT FROM AUTHOR]

This paper develops a new approach for the design of polynomial-based reference and feedforward control trajectories for the high precision control of flexible servo actuators. First, a robust frequency-domain controller is designed for reference tracking and disturbance rejection. This controller is designed to achieve a desirable loop shape with reasonable bandwidth and stability margins. Then, the polynomial trajectories are derived based on a simplified rigid body representation of the system. To avoid the excitation of the system's resonant modes, this paper proposes the design and implementation of a set of feedforward notch filters. We further investigate the main cause of tracking error resulted from the rigid body approximation, and propose an alternative model for the derivation of the polynomial input trajectories. This model accounts for the cumulative DC gain of the resonant modes ignored in the rigid body approximation. A method for deriving the new polynomial trajectories with the appropriate initial and final time conditions is developed and evaluated for a representative flexible servo system model. Simulation results indicate that the proposed scheme provides significant improvement in the performance of system compared to the conventional methods. • Polynomial feedforward inputs improve settling response of flexible servo systems. • Feedforward notch filters can mitigate high-frequency vibrations during settling. • Accounting for actuator flexibility in the feedforward model reduces settling time. [ABSTRACT FROM AUTHOR]

This paper proposed a prediction algorithm for the degraded actuator taking into account the impact of estimation error of hidden index in the closed-loop system. To this end, a unified prediction framework is established to evaluate the hidden degradation information and recursively update the degradation model parameters simultaneously. The advantage is that the prediction framework can comprehensively compensate the estimation error of hidden degradation index caused by system uncertainty. To jointly estimate the degradation information in avoidance of the impact of system uncertainty, a modified adaptive Kalman filter is designed, and the proof of stability is provided. With the priori estimate from the filter, the degradation model parameters are updated by the inverse filtering probability based on Bayes' theorem. It is followed by the computation of the remaining useful life (RUL) prediction utilizing aforementioned hidden degradation information and the latest degradation model. The effectiveness of the proposed RUL prediction algorithm is demonstrated by the degraded actuator in the continuous casting process. • A novel prediction framework is designed for degraded actuator in closed-loop system. • Adaptive degradation model is established by modified adaptive Kalman filter. • The estimation error of hidden degradation index is integrated. • The stability of optimized adaptive Kalman filter is proven. • Recursive prediction algorithm is performed without full life data. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive review of the diverse approaches employed to study dynamic responses of gossamer membrane structures for space applications. The primary aim of the current review article is to explore the proposals/attempts made in the literature to understand the vibration, wrinkling, and shape control phenomena of these structures using analytical, experimental, and numerical approaches. This review delves into understanding the impact of various parameters/factors such as membrane thickness, aspect ratio, geometric and material properties, aspect ratio, types of load, load ratio, boundary conditions, air added mass, inflation pressure, type of actuators, and their placements etc. on the behavior of membrane structures. [ABSTRACT FROM AUTHOR]

This paper proposes a novel sliding mode control (SMC) algorithm for direct yaw moment control of four-wheel independent drive electric vehicles (FWID-EVs). The algorithm integrates adaptive law theory, fractional-order theory, and nonsingular terminal sliding mode reaching law theory to reduce chattering, handle uncertainty, and avoid singularities in the SMC system. A sequential quadratic programming (SQP) method is also proposed to optimize the yaw moment distribution under actuator constraints. The performance of the proposed algorithm is evaluated by a hardware-in-the-loop test with two driving maneuvers and compared with two existing SMC-based schemes together with the cases with the change of vehicle parameters and disturbances. The results demonstrate that the proposed algorithm can eliminate chattering and achieve the best lateral stability as compared with the existing schemes. [Display omitted] • A novel AFONT-SMC is proposed to achieve fast global convergence and precise tracking. • An adaptive law is proposed to avoid singularity and strengthen the system robustness. • A new boundary of full vehicle is studied to ensure the controllability of FWID-EVs. • Two new actuator constraints are studied to improve torque distribution in FWID-EVs. [ABSTRACT FROM AUTHOR]

With the increased motion requirements of precision drive devices, multi-degree-of-freedom piezoelectric actuators have become key technologies for realizing multi-axis motion control. To expand upon the three-degree-of-freedom piezoelectric stick-slip driving method, a sandwich-type three-degree-of-freedom rotating inertial stick-slip piezoelectric actuator is proposed in this paper. Firstly, the structure and control strategy of the actuator were introduced. Statics analysis of the core component of the piezoelectric vibrator was carried out, and the relationship between the structural parameters and the deformation of the driving foot was obtained. Then the free and forced vibrations of the piezoelectric vibrator are analyzed to determine the dynamic response of the driving foot in the time domain. Finally, a prototype was fabricated and an experimental system was built to test its output characteristics. The test results show that when the driving voltage was 150 V and the frequency was 320 Hz, the proposed actuator achieves maximum speeds and load torques around the x- axis and y- axis of 306 mrad/s and 2 mN m, respectively. When the driving voltage was 150 V and the frequency was 450 Hz, the proposed actuator achieves a maximum speed and load torque around the z-axis of 140 mrad/s and 1.55 mN m, respectively. [Display omitted] • A piezoelectric actuator with three-degree-of-freedom motion is proposed. • The problem of structural redundancy caused by increasing the preload is solved. • The vibrator's dynamics model is established, solved, and analyzed. • Load capacity and speed are superior to the same type of actuator. [ABSTRACT FROM AUTHOR]

The paper discusses the dissipative control problem of nonlinear singularly perturbed systems (SPSs) with dynamic quantization and actuator failure. The nonlinear singularly perturbed plant is described by Takagi–Sugeno (T–S) fuzzy model. The dynamic quantizer is considered to realize the effective utilization of the limited network channel bandwidth resources, and the possible transmission failure between the controller and the actuator is also considered. Based on linear matrix inequalities, sufficient design conditions for the ϵ -independent state feedback controller are given such that the constructed quantized closed-loop system is asymptotically stable and satisfies a predefined dissipative performance. Furthermore, a short search algorithm is given to search the maximum stability bound ϵ ̄. Finally, two examples are provided in order to prove the feasibility and effectiveness of the proposed method. • A state feedback control scheme is proposed for fuzzy singularly perturbed systems. • The dissipative performance of fuzzy singularly perturbed systems is analyzed. • Sufficient conditions are given to design the controller and the quantizer. [ABSTRACT FROM AUTHOR]

This paper studies the control problem for a continuous-time networked system with non-linearity in the state equation as well as in the input, as saturation. The system is considered under denial-of-service (DoS), attacks which cause the blockage of input and/or output components in the overall closed-loop model. An event-triggering scheme that is resilient in nature, along with an observer-based control, has been considered under DoS attacks. The resultant scheme ensures efficient network resources and excludes Zeno behavior naturally due to the presence of a minimum positive interevent delay. Then, an event-based switched non-linear model is presented to address both the event-triggering scheme and the presence of DoS blocking attacks. A piece-wise Lyapunov–Krasovskii functional method on the described non-linear model, resulting in the switched system, is considered for achieving an exponentially stable response by driving the required feasibility conditions. In the presence of a non-linear system with saturation in the actuator, the presented design establishes quantitative relationships among the exponential decay rate, active/sleeping intervals of attacks, parameters of the event-triggering condition, and sampling period of the system. After that, linear matrix inequalities are presented for designing an event-triggered controller with an observer, while the design also includes the region of convergence for dealing with the input non-linearity. Finally, comparative results for an offshore structure model with non-linearity in states as well as in actuator, are demonstrated to verify the results of the control scheme that is developed. It has been verified that our design is less conservative than the previous designs, and can handle the non-linearities in the dynamics of plant and actuator saturation more efficiently, while DoS attacks are also present. By applying our proposed method, the overshoot and undershoot are less than ±2.5 percent, while system states converge to the origin within 55 s. • An ϵ T-Lipschitz condition is used with a scaling factor ϵ and a variable matrix T • Non-linear control designed for system with input saturation and state non-linearity • Stability of the system is ensured in presence of DoS attacks with event triggering • Output feedback is utilized with switching non-linear observer having multiple gains • The joint design of all the required matrices using LK functions is utilized [ABSTRACT FROM AUTHOR]

Smart hydrogel actuators which respond to external stimuli have attracted great attention and shown good application prospects in many fields as their simplicity and reliability, while the challenges remain in terms of the relatively low driving force, responsive velocity and deformation amplitude considering the structure-dependent actuation behavior. Here, we propose a thermosensitive hydrogel-based actuator with bioinspired bilayer structure by applying a textured airlaid paper to induce the formation of heterogeneous construction. This nature-inspired design benefits the hydrogel-based actuator rapidly bidirectional actuation, realizing excellent bending velocity (140.6° s−1 within first 5 s) and bending amplitude (850.0° within 30 s) in hot water, powerful recovery in cool water and remarkable reproducibility upon external environmental stimulus by optimizing the texture orientation and mechanical property of airlaid paper. The excellent bonding between airlaid paper and hydrogel also endows the actuator satisfactory stability for circularly operation under water environment for weeks. The programmable deformation and devisable functionality are further realized by propagable and elaborate design for architecture and component of responsive hydrogel, favoring the hydrogel-based actuator alterable ethanol-sensitive ability, photothermal drivability and regenerability. This bilayer hydrogel-based actuator provides promising potentials for the applications in soft robots, smart actuators, artificial muscles, and intelligent human-machine technologies. [Display omitted] Inspired by the fast underwater motion of snap-traps of the Aldrovanda vesiculosa, we have reported a bilayer hydrogel-based actuator consisting of hydrogel layer and airlaid paper layer. This nature-inspired design benefits the bilayer hydrogel-based actuator rapidly bidirectional actuation, meanwhile the programmable deformation and devisable functionality are further realized by optimizing the structure-related parameters. • A thermosensitive hydrogel/airlaid paper actuator with bioinspired structure is proposed. • The airlaid paper can be treated by different solutions to changes its mechanical property and actuating performance. • Programmable deformation and devisable functionality are realized by architecture and component design of hydrogel. • This actuator has application potentials in soft robot, smart actuator, and intelligent human-machine technologies. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is an insulator and should be converted to reduced graphene oxide (rGO) paper structure by reduction to provide electrochemical activity. This work maintains an essential route to fabricate rGO paper. Hence, the first aim of this study is to produce rGO paper by one-step electrochemical reduction of GO paper by the optimization of quality parameters. Humidity actuators produce mechanical feedback if the moisture is exposed to their surface. To provide this kind of response, Janus materials are good nominated due to their asymmetric surface character in terms of hydrophilicity. GO paper can be performed for this application by converting one side to rGO layers. By this approach, hydrophobic rGO and hydrophilic GO sheets of the Janus system are generated, in which moisture flow swells the GO side and causes bending motion of the material through the rGO layer. In this work, Janus GO/rGO paper has been prepared by one-step electrochemical reduction of one side of the GO paper. Characterization of the samples has been carried out using numerous techniques. Humidity actuator experiments have indicated that Janus GO/rGO paper is acting circularly and there is an exponential relationship between relative humidity and circularly-oriented bending angle of the actuator. [Display omitted] • Preparation of rGO paper by one-step electrochemical reduction route. • Fabrication of Janus GO/rGO paper by electrochemical reduction of one side of GO paper. • Circular actuation of GO/rGO paper proportional to moisture content. • High stability and reproducibility of Janus GO/rGO paper as a humidity actuator. [ABSTRACT FROM AUTHOR]

The problem of retargeting rigid body attitude with attitude constraints has been extensively investigated, whereas the challenge persists in maneuvering rigid-body attitude with multiple concurrent attitude constraints and finite sequential actuator faults. Finite sequential actuator faults, which can reduce controllability or destabilize the system, necessitate the implementation of fault-tolerant control strategies. Therefore, this paper aims to address the issue of redirecting spacecraft attitude subject to multiple attitude constraints and finite sequential actuator faults comprehensively. Firstly, we represent spacecraft attitude using unit quaternions and employ an artificial potential function to effectively handle multi-attitude constraints. The negative gradient direction guides the rigid-body spacecraft towards seamless convergence with the desired attitude. Our proposed unwinding strategy effectively avoids unwinding phenomena during large-angle spacecraft reorientation as well. Additionally, we design an adaptive compensation strategy for finite sequential actuator faults that enables real-time calculation of the fault compensation matrix under such actuator faults. Importantly, we propose an improved adaptive fault-tolerant back-stepping controller integrated with a potential function that effectively addresses both attitude constraints and finite sequential actuator faults simultaneously. Subsequently, stability analysis is conducted on the proposed controller to ensure its stability in practical applications rigorously. Finally, numerical simulations are performed meticulously to demonstrate the effectiveness and robustness of our proposed controller. [ABSTRACT FROM AUTHOR]

Precision micro-manipulation tasks demand high-speed motion but low driving frequency for stick-slip actuators to achieve efficient operation and reduce friction wear. This paper presents a novel parasitic-type linear stick-slip actuator with macro fiber composites (MFCs). Unlike conventional piezoelectric actuators, the proposed stick-slip actuator has large single-step displacements and high motion consistency. It can realize high-speed motion under low driving frequency due to the superior properties of MFCs and the dual-drive method with a single driving foot. The actuator is devised based on a multi-beam-compliant driving mechanism, a pair of MFCs, and a slider. Also, an electromechanical dynamic model is proposed. A switching control strategy guarantees high positioning accuracy under large strokes. Finally, an experimental system is built. The single-step displacement can reach 367.7 μm with the dual-drive method. The actuator still has an effective stepping displacement of 63.4 μm even with a load of 2.1 kg. The maximal speed is 131.80 mm/s at a working frequency of 450 Hz. Thus, the actuator can realize mm/s motion with several Hertz driving voltages. Moreover, the maximum forward-reverse deviation only accounts for 1.31 % for a 2504 μm motion range, and the closed-loop motion resolution is 1.970 nm. Experiments verify the effectiveness and performance of the designed MFC stick-slip actuator. [Display omitted] • Macro-fiber-composite stick-slip actuator with large single-step displacements. • High forward-reverse motion consistency. • Electromechanical dynamic model for the MFC stick-slip actuator. • Nanoscale motion resolution using feedback control. [ABSTRACT FROM AUTHOR]

In this paper, a distributed bearing-based formation control scheme with finite-time convergency is proposed for multiple underactuated surface vessels (USVs). By virtue of the guide point-based model transformation method, the dimension of underactuated tracking error dynamics can be reduced from three to two. This allows us to convert the actuator model to a fully form that matches dimension-reduced tracking error dynamics. Further, to reduce the computation complexity, a finite-time recruited filter is designed according to first-order Levant differentiator. At meanwhile, auxiliary error compensation signals are introduced to address unknowns stemming from filter process and system dynamics. Since merely relative-distances and inner bearings are utilized in the proposed bearing-based formation approaches, the proposed control scheme provides a feasible solution to achieve formation control under body-fixed frame. Finally, theoretical analysis and numerical simulations are presented to demonstrate the efficacy. • Bearing-based finite-time formation control. • Underactuated surface vessels. • Levant differentiator. • Command filtered backstepping with error compensation signals and compensated errors. [ABSTRACT FROM AUTHOR]

Variable stiffness actuators (VSAs) are essential for ensuring safe human–robot interactions in robotic applications. This paper proposes a novel rotary VSA using an antagonistic Hoberman linkage mechanism (AHLM), which offers a large stiffness range and a compact structure. The VSA-AHLM consists of two sets of antagonistic-type quadratic springs based on spiral cams connected to the Hoberman linkage mechanism (HLM) through four cables. By simultaneously adjusting both the radius of the HLM and the spring preload, the stiffness of the VSA-AHLM can be varied within a large range. Furthermore, the position and stiffness of the VSA-AHLM can be controlled independently by two rotary motors. The geometric parameters of the spiral cam are determined to achieve the desired linear stiffness–elongation behavior of a quadratic spring, and detailed models of the actuator's stiffness, elastic energy, and torque are established. An actuator prototype is fabricated to demonstrate the proposed variable stiffness approach. Experiments show that the developed actuator can achieve significant stiffness changes and exhibits excellent positioning and trajectory tracking performance. • A novel variable stiffness actuator is proposed for robotic applications. • An approximate quadratic spring is designed based on a variable radius pulley. • The performance of the variable stiffness actuator is investigated experimentally. • The position and stiffness are independently controlled by a proportion-derivative and feedforward controller. [ABSTRACT FROM AUTHOR]

• A fixed-time disturbance observer is proposed under the event-triggered technique to provide an attenuation effect on multi-source disturbances such as exogenous disturbances, system uncertainties, actuator faults, periodic vibrations and uncertain modeled disturbance of actuator, and input saturation. • Propose a fault-tolerant fixed-time controller to track the attitude of spacecraft under multi-source disturbances and limited communication framework. The proposed controller overcomes the unwinding phenomenon, and results show that attitude attitude-tracking path described by quaternion is the shortest maneuvering path. • Stability analysis of a closed-loop system ensures that both disturbance estimation error and the attitude tracking error of the system converge to a final boundary within a fixed time. Moreover, Zeno-free behavior is always guaranteed. This paper studies the attitude tracking problem for rigid spacecraft under restricted communication resources. This work proposes a novel composite control scheme for spacecraft subjected to system uncertainty, exogenous disturbance, periodic vibrations and uncertain modeled disturbance of actuator, actuator faults, and input saturation, which consists of a fixed-time controller (FiTC) based on an integral non-singular fast terminal sliding mode technique and a fixed-time disturbance observer (FiTDO). The FiTDO estimates the total disturbance (combination of the abovementioned effects) within a fixed time. Further, it improves the attenuation disturbance property of the composite controller by feedforward compensation. The proposed controller relaxes the prior upper-bound knowledge of the total disturbance and has anti-unwinding characteristics. Moreover, the designed event-triggered mechanism reduces control workload reduction and guarantees the Zeno-free behavior in the proposed composite scheme. The stability analysis of the closed-loop system under the proposed scheme using Lyapunov theory ensures the system states converge to a small invariant set within a fixed time. Simulation analysis and comparative studies demonstrate that the proposed scheme is effective in terms of convergence time, steady-state performance, and anti-interference ability, rate of controller update. [ABSTRACT FROM AUTHOR]

This paper mainly addresses the practical consensus problem of nonlinear multi-agent systems modeled by reaction–diffusion equations subject to the bounded external disturbances. Different from the existing consensus control methods associated with spatiotemporal dynamics, the proposed H ∞ Neumann boundary controller based on distributed measurement data can guarantee the optimal disturbance attenuation performance under the actuator saturation. Initially, a consensus spatiotemporal error model is constructed by introducing the Kronecker product and equivalent directed graph. Subsequently, a linear matrix inequalities (LMIs)-based sufficient condition is derived by combining the improved Lyapunov-based approach and H ∞ norm. Then, an optimization problem is proposed by applying invariant set, such that the consensus errors can converge to a minimized bounded region in the presence of actuator saturation. Finally, comparison simulations on the synchronization of FitzHugh–Nagumo (FHN) model are given to demonstrate the effectiveness of proposed methodology. • This paper addresses the problem of practical consensus with spatiotemporal dynamics. • The multi-agent system is modeled by a nonlinear reaction–diffusion equation. • An H ∞ boundary consensus control is proposed to suppress the external disturbances. • The controller needs a fewer actuators than ones distributed inner spatial domain. • The controller gives a tradeoff between optimal performances and actuator saturation. [ABSTRACT FROM AUTHOR]

Carbon nanotubes are unique nanostructures with interesting properties that suit them to a range of diverse applications including nanoscale electronics, use in composites, as gas storage media and scanning probe tips. An exciting property of carbon nanotubes is their ability to efficiently convert electrical energy into mechanical energy (actuation). Nanotube actuation is caused by the geometrical expansion of the carbon–carbon covalent bond caused by charge transfer into the nanotube [Abstract American Chemical Society 22 (1999); Abstract American Chemical Society 20 (2000)]. This ability to actuate, in addition to their high strength (∼1 TPa), makes macro-scale sheets of nanotubes termed `bucky paper'', ideal for artificial muscles [Science 284 (1999) 1340]. Carbon nanotube actuators based on bucky paper have been shown to generate an order of magnitude higher stresses than those observed for natural muscle. These promising results suggest that carbon nanotube actuators based on a single (or a few hundred) nanotubes will also lead to enhanced applications on the micro- or nano-scale in the biomedical or electronic fields. This paper provides an overview of carbon nanotube actuators, their exceptional properties, current research ideas and possibilities for future applications. [Copyright &y& Elsevier]

Oxygen stoichiometry (OS) and stack temperature (ST) significantly affect the output performance and durability of proton exchange membrane fuel cells. This paper investigates the prescribed performance tracking control strategy of OS and ST under external disturbances, modeling errors, actuators faults and limited communication resources. The total disturbances are compensated by a variable-bandwidth extended state observer to simplify the control design and enhance the system robustness. To tolerate excessive disturbances and relax the strict requirement on the initial conditions, a new event-triggered adaptive sliding mode controller that integrates modified dynamic performance constraints and nonsingular error transformation is developed to ensure the user-designed transient and steady-state performance constraints, while saving the communication costs and avoiding the chattering and jump in control signals. The numerical validation results under combined working scenarios indicate that the proposed controller always ensures the preset error constraints and possesses superior performance in tracking the optimal OS value 2 and the optimal ST value 353.15K than other three representative controllers, with the integral absolute errors of 0.732 for OS tracking and 12.94 for ST tracking; besides, it achieves satisfactory robustness to uncertain model parameters and relatively large initial tracking errors. [Display omitted] • A robust event-triggered prescribed performance controller for PEM fuel cell systems. • Oxygen stoichiometry (OS) and stack temperature (ST) are simultaneously controlled. • Integral absolute errors when tracking OS and ST are 0.732 and 12.94 respectively. • A better compromise between control performance and communication cost. • The chattering and jump phenomena in control signals are suppressed. [ABSTRACT FROM AUTHOR]

It is the first report about fault-tolerant-based prescribed performance control of switched nonlinear systems under multiple faults. The concerned faults include not only external faults but also actuator faults. In the process of backstepping control design, prescribed performance control is fully considered, and the combination of unknown nonlinear functions is estimated by multi-dimensional Taylor network. Finally, the developed adaptive fault-tolerant control strategy guarantees the boundedness of all controlled signals while prescribed tracking performance is satisfied. In an effort to further manifest the validity of the fault-tolerant controller, a numerical simulation and a practical simulation are introduced. • This paper is dedicated to balancing prescribed tracking performance and multiple faults. • It is the first time that actuator fault, external fault are discussed in the complicated switching framework. • The adaptive fault-tolerant MTN-based controller is developed to cope with performance constraints. [ABSTRACT FROM AUTHOR]

To achieve a wide operating velocity range, stepping without backward motion, and high positioning resolution, a walking-type piezoelectric actuator with compliant mechanisms is developed. There are few academic research reports on this type of actuator, and this paper clarifies the features and advantages of this actuator. A systematic modeling and experimental evaluation of the proposed actuator are carried out. First, the configuration of the proposed actuator and the working principle of the alternating elliptical movements of the two driving feet are described. Then, dynamic models are built to simulate the output characteristics of the proposed actuator with in-phase and opposite-phase drive, which provide guidance for the design and optimization of walking-type actuators. An actuator prototype is fabricated and experimentally evaluated. The experimental results indicate that, under the opposite-phase drive, the proposed actuator can operate at a driving frequency of 1–15000 Hz. At a frequency of 14000 Hz, a maximum velocity of 24.6 mm/s is achieved at a voltage of 36 V pp , and the dead zone of the actuator is 0–6 V pp. A step displacement of 2.25 μm without backward motion is accomplished at a voltage of 72 V pp and a frequency of 1 Hz. Furthermore, the positioning resolution in the forward and reverse directions are 144 and 152 nm, respectively. The repeatability of the actuator is ±25 to ±50 nm for strokes of 325–725 nm, respectively. Therefore, compared to two driving feet being driven in phase, driving them in opposite phase as if they were walking has been confirmed to increase thrust, shorten the rise time, reduce the dead zone of driving voltage, eliminate backward motion, and provide high repeatability. • A piezoelectric actuator with triangular compliant mechanisms is first developed. • Dynamic models in the x - and y -directions are established for performance evaluation. • The actuator achieves a wide operating velocity range, no backward motion, and high-precision positioning. [ABSTRACT FROM AUTHOR]

This paper presents a novel control strategy to minimize residual vibrations and overshoot using inertial dampers in repetitive tasks. In this work, vibration data collected during repeating task is utilized to generate a fully pre-scheduled feedforward compensation signal that assists the inertial damper's original feedback controller to further enhance its vibration mitigation capability. Optimal feedforward signal is determined iteratively over successive operations considering the actuator stroke and force limits. Numerical and experimental results validate the approach demonstrating significant (up to 87%) reduction in peak vibration while using equal or less actuator force as compared to the conventional control. [ABSTRACT FROM AUTHOR]

This paper investigates the fault-tolerant prescribed performance control problem for a class of multiple-input single-output unknown nonlinear systems subject to process faults and actuator failures. In contrast to the related works, we consider a general class of nonlinear systems with both multiplicative nonlinearities and additive nonlinearities corrupted by the process faults; only the boundedness of the process faults and the continuity of the nonlinear functions are required, without the explicit or fixed structures of the fault functions. To conquer this problem, a less-demanding and low-complexity fault-tolerant prescribed performance control approach is proposed. The controller is independent of the specific information of faults or the system model and does not invoke fault diagnosis or neural/fuzzy approximation to acquire such knowledge. It achieves the reference tracking with the predefined rate and accuracy. A comparative simulation on a single-link robot is conducted to illustrate the effectiveness and superiority of the proposed approach. • Both process faults and actuator failures are considered. • The virtual control coefficients are time-varying nonlinear functions. • We consider a general class of systems with multiplicative and additive nonlinearities. • Both multiplicative and additive nonlinearities are impacted by process faults. • The reference tracking with predefined rate and accuracy is achieved. [ABSTRACT FROM AUTHOR]

The stability and drivability of distributed drive electric vehicles over split-friction regions and with actuator faults are studied in this paper by using control allocation. Under the integrated control architecture of high-, medium-, and low-level controllers, a slip-ratio-based synchronization approach is presented to redistribute the driving force for all the driving wheels. The synchronization of slip ratios on wheels is accomplished by autonomously regulating the distribution parameters in the design of a low-level controller. Therefore, the driving force and moment can be adjusted from the design of the regulator on distribution parameters so that the stability and driving performance are ensured when electric vehicles drive over split-friction regions. Subsequently, the concept of distribution parameters is extended to handle actuator faults in electric vehicles by regulating the driving force via the adjustment of distribution parameters. The proportional fault, additive fault, and motor saturation are considered in this paper by compensating for the loss of driving force from the force allocation approach. Numerical examples using CarSim with MATLAB/Simulink and human/hardware-in-the-loop validations are illustrated to demonstrate the efficacy and performance of the proposed control schemes. • A slip-ratio-based force allocation control is presented for DDEVs over split-friction regions. • Auto-regulation of distribution parameters ensures stability of DDEVs with actuation faults. • Integrated controller with force allocation and fault-tolerant control are validated using HIL. [ABSTRACT FROM AUTHOR]

The design of robust state- and output-feedback control for uncertain discrete-time systems with physical magnitude and rate constraints on their actuator dynamics was addressed. Unlike the traditional methods such as anti-windup (AW) methods, nested ellipsoids, model predictive controllers (MPCs) and integral quadratic constraints(IQCs) formulated by sector bounded inequalities, this paper uses a transformation of the system dynamics to a form which considers control signal and its rate as controlled outputs and using discrete-time ℓ ∞ induced (peak-to-peak) norm from disturbance inputs to these outputs. To cope with the magnitude and rate bound non-linearities together, the induced ℓ ∞ norm from disturbance input to the outputs involving control signal and its rate is utilised. On the other hand, discrete-time(DT) induced ℓ 2 norm from disturbance input to the main controlled output is used to mitigate the effects of disturbances. We can tackle this ambitious non-linear control problem in the domain of linear convex multi-objective optimal control problem, which can be solved by effective semi-definite optimisation methods by using the proposed transformation and handling the control constraints in terms of worst case peak-to-peak gain of the system. Extended Linear Matrix Inequalities (LMIs) and full block S-procedure based design conditions developed over Linear Fractional Representation(LFR) framework allow the user to obtain robust state- and output-feedback control solutions with reduced conservatism. For the first time, this paper introduces an extended LMI based robust output-feedback control design for magnitude and rate bounded (MRB) systems, using full block S-procedure. We demonstrate the performance of the proposed controller through several simulations over benchmark examples covering systems having multi-variable structures and uncertainties. Our study also involves comparison results with a recently introduced technique based on multi-stage AW technique. The simulation results show that the proposed method of this paper is much effective and less conservative compared to the recent AW method provided in the literature. • A robust dynamic-output feedback controller is provided for systems with constraints. • Multi-objective topology is used with acceleration form representation of the process. • To deal with uncertainties, full block S-procedure is adapted to the design. • The method provides an alternative to recently developed anti windup techniques. [ABSTRACT FROM AUTHOR]

This manuscript discusses the positional systems used in intelligent robots. One of the characteristic problems that arise in such systems is associated with friction, including sticking during the process. Friction greatly affects the positioning accuracy of the actuators of controlled robots, especially if a pneumatic actuator is used as a motor. The work is devoted to the study and solution of this problem. Since it is impossible to completely eliminate the effect of friction, ways to minimize this effect are being investigated using a targeted choice of system parameters. For this purpose, the method of multicriteria optimization of a detailed mathematical model is applied on the example of a pneumatic positional system, as the most sensitive to friction. The paper considers the first stage of optimization associated with visualization and preliminary analysis of the process in order to prepare it for performing a system procedure. The dynamics equations of an intelligent positional system are written out, both in full-size and dimensionless one. The most convenient mathematical model of friction is presented terms of its use in the process of optimizing the entire control system. A procedure for visualizing the optimization process in the form of a graphical interface has been developed. The first stage of the intelligent drive system optimization procedure has been carried out. The paper presents at which parameters of the control system the "stick-slip" effect has less influence on the positioning process. [ABSTRACT FROM AUTHOR]

This paper proposes a novel fixed-time output feedback trajectory tracking control method suitable for autonomous surface vehicles (ASVs). Firstly, various complex uncertainty terms, such as unknown external disturbances, unmodeled errors, and actuator faults are considered in this paper. And these terms are uniformly converted into the total uncertainty terms through model transformation for convenience. Then, a fixed-time extended state observer (FTESO) with the newly expanded state is designed to observe and estimate the total uncertainty terms. Next, the saturation dynamic filter (SDF) is adopted to address the input saturation, and the saturation factors of SDF are incorporated into the trajectory error calculation to reduce the torque mutation caused by an excessive error in the control input. Finally, a fixed-time control law is proposed by taking into account the ASV system error and FTESO estimation state. Simulation experiments show that this method has excellent control performance, and this conclusion is validated through stability proof and case comparison. • A FTESO is designed to estimate the unknown states of ASVs. • A SDF is employed to address input saturation. • A novel FTOFC method is proposed for the stable and efficient operation of ASVs. [ABSTRACT FROM AUTHOR]