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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]

• 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]

[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]

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 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]

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]

• 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]

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]

This paper investigates the attitude coordination control issue for spacecraft formation flying in the presence of actuator saturation and external disturbances with unknown boundaries. Firstly, a super-twisting integral terminal sliding mode surface is developed, which ensures that the sliding mode surface and its first-time derivative converge to zero in finite time. Then, based on the developed sliding mode surface and adaptive technique, a robust anti-saturation distributed attitude coordination controller that enables the attitude and angular velocity to precisely track the desired time-varying command in finite time is devised under the undirected communication topology. Finally, stability analysis and numerical simulations validate the effectiveness and feasibility of the devised control approach. [ABSTRACT FROM AUTHOR]

The electrohydrodynamic (EHD) actuator system, which produces thrust by ionizing a gas and accelerating it, is a novel propulsion system for near space vehicles. In this paper, an analytical model for EHD actuators, called EHD-AM, has been presented to estimate the thrust produced by the actuators in a wire-to-cylinder configuration. Experimental data from six previous studies have been used to validate the model and the mean absolute percentage error (MAPE) between each configuration and EHD-AM has been calculated under different environmental conditions. Based on the evaluations, the MAPE between EHD-AM and the experimental results for different pressures and wire-to-airfoil structures is 7.18% and 6.16%, respectively. The MAPE between EHD-AM and the experimental data measured by particle image velocimetry (PIV) method and with conventional experimental setups is 10.59% and 6.76%, respectively. Based on the EHD-AM, at a constant voltage, the relation between thrust and pressure has a local minimum and a local maximum point in the range of 0.05–1 atm. From 0.05 atm to 0.5 atm, as the pressure increases, the thrust decreases and then increases. As the pressure increases from 0.5 to 1 atm, the thrust decreases. In addition, a higher voltage can result in a higher pressure at which thrust is maximized. Furthermore, the generated thrust is monotonically increasing as the voltage amplitude increases. By implementation of EHD-AM thrust scale in a simple numerical model, the thrust generated by the actuator has been computed and simulated numerically. Initially, the numerical model was verified using experimental results from a previous study. The MAPE between the numerical model and the EHD-AM is 24.08%. Finally, when the interelectrode gap, the collector radius and the emitter radius are relatively large, the thrust of the actuator is predicted by EHD-AM and compared with the numerical results. EHD-AM can be used in the design and optimization of EHD actuators, and also for controller design and related analyses in a control system. • In EHD actuator, the relation between the thrust and the pressure is determined. • The relationship between corona current and voltage has been considered based on the space-charge-limited current relations. • In high and low mobility of ions, the thrust is obtained as a function of voltage. • Analytical model for corona discharge-based EHD plasma actuator is obtained by incorporating environmental conditions. [ABSTRACT FROM AUTHOR]

Spacecraft attitude control employs quaternion representation to avoid singularity issues and obtain global maneuver stability. However, it has redundancy associated, resulting in dual equilibrium points. The attitude control may confront the unwinding phenomenon due to the presence of the equilibria. In this paper, an anti-unwinding controller for spacecraft stabilization in the presence of external disturbances and inertial uncertainties, angular velocity limit, actuator saturation and faults is presented. Specifically, a modified extended state observer (ESO) is designed to obtain total disturbance estimates of the rigid-body spacecraft. Auxiliary parameters are added in the design to avoid initial high estimates in the proposed ESO design resulting in faster convergence. The proposed disturbance observer is to release the assumption that requires the estimated disturbance to be constant or varying at slow rates. Using the ESO estimates, a particular back-stepping-SMC (ESO-BTSMC) controller is devised to formulate anti-unwinding control law for spacecraft stabilization. Lyapunov stability theory is employed to prove closed-loop stability of system and estimation error convergence. Comparative simulations are performed to demonstrate the performance of the proposed control scheme. It is found that the proposed control scheme gives smooth and precise control performance along with faster transient response. Additionally, it also alleviates the chattering phenomenon. [ABSTRACT FROM AUTHOR]

This paper investigates the attitude fault-tolerant stabilization problem for a spacecraft subjected to its actuator effectiveness loss, inertia uncertainties and space disturbances. A novel Iterative Learning Sliding Mode Observer (ILSMO) is proposed to reconstruct the actuator effectiveness factors robustly and accurately by combining the P-type iterative learning algorithm with the sliding mode approach. Based on the reconstructed fault signals, an Iterative Learning Sliding Mode Controller (ILSMC) is designed to guarantee the closed-loop spacecraft attitude fault-tolerant stabilization by compensating for its lumped disturbance. The ILSMO and ILSMC stabilities are guaranteed using the Lyapunov direct approach, respectively. Finally, the numerical simulation results show that the proposed ILSMO-ILSMC-based spacecraft attitude fault-tolerant stabilization method is effective and superior. [ABSTRACT FROM AUTHOR]

This paper presents the design and development of a new granite hardware-in-the-loop air-bearing testbed that can emulate the relative dynamics of orbiting spacecraft. The air-bearing testbed's granite slab is supported via a fixed post and two mechanically adjustable screw actuators that allow the table's surface to change in orientation. The surface can actuate in two axes: pitch and roll. As the table tilts, the Earth's gravitational acceleration affects the acceleration experienced by a floating test vehicle operating on its surface without the need to activate the vehicle's on-board thrusters. Thus, the testbed emulates the relative orbital dynamics between two orbiting spacecraft, instead of the planar zero-g conditions provided by most granite table facilities. Proof-of-concept experimental results are presented. [ABSTRACT FROM AUTHOR]

In this paper, a finite-time active fault-tolerant control scheme is designed for a flexible spacecraft's attitude control experiencing inertial parametric variations, external disturbances, multiple actuator faults, and estimation errors while suppressing the flexible appendages' vibrations without using smart vibration suppression actuators. First, relative attitude dynamics of a flexible spacecraft with multiple actuator faults are outlined, and a sliding mode observer is designed to estimate flexible appendages-related vibrations. The proposed fault detection and identification (FDI) strategy can efficiently detect actuator faults, avoiding the false alarms caused by uncertainties and disturbances, and accurately estimate the cumulative fault effects on the spacecraft via Chebyshev neural network (CNN) based estimator. Based on a novel fast nonsingular terminal sliding mode surface, a finite-time, unwinding-free, and adaptive fault-tolerant attitude controller is designed to acclimatize the detected faults and uncertainties effectively, also heeding the errors in the estimation of flexible modes and faults. The spacecraft can carry out the coveted control objective in a definable time, and the stability of the proposed controller is corroborated via Lyapunov techniques. Finally, a comparative simulation analysis with the existing results elucidated the proposed scheme's efficacy. [ABSTRACT FROM AUTHOR]

This paper considers the data-driven fault isolation and estimation problem for linear time-invariant systems with unknown dynamic matrices and multiple actuator faults. In most of existing fault isolation methods, how to accurately identify the types of faults has not been solved well when the system matrices are unknown. To deal with this problem, a neural network-based fault isolation method is proposed by analyzing and extracting features of different fault models in terms of constructing sparse vectors and function libraries using the available input–output data. Then, a fault estimator is designed to estimate the fault signals within the data-driven framework, where its parameters are computed by the system's Markov parameters and the identified types of faults. Finally, two examples are used to verify the advantages and effectiveness of the proposed fault isolation and estimation approach. • A data-driven fault diagnosis approach is developed for unknown linear systems. • A neural network-based fault isolation method is used to isolate actuator faults. • The faults features of different fault models are analyzed and extracted. • A fault estimator is designed for both single and simultaneously occurring faults. • H 2 index is used to attenuate the effects of noises on fault estimation error. [ABSTRACT FROM AUTHOR]

This paper designs a fuzzy adaptive control approach for the Continuous Stirred Tank Reactors (CSTRs) with full state constraints and actuator faults. Using the backstepping design technique and Integral barrier Lyapunov function (IBLF), the full state constraints are handled in the design process of the adaptive controller. Besides, there exist unknown internal dynamics in the CSTRs system, which are identified by the fuzzy logic system. It is shown that the constraints are not overstepped and the CSTRs operate reliably is ensured, despite the presence of system nonlinearities, stuck faults and loss of control effectiveness. Based on the Lyapunov stability theory, the proposed approach can ensure that all the signals of the CSTRs system are globally bounded. Finally, the simulation results on CSTRs are showed to reveal the availability of the developed control scheme. [ABSTRACT FROM AUTHOR]

In this paper, a novel observer-based prescribed performance finite-time dynamic event-triggered consensus controller is investigated for multi-agent systems with external disturbances, actuator faults, model uncertainties, and limited communication. Different from existing dynamic event-triggered control schemes, here a dynamic event-triggered strategy that can be applied to multiple communication channels simultaneously is proposed, which further extends the advantages of event-triggered control. In this context, three issues are the main research directions of this paper. First, a controller that does not need to be constantly updated according to the real-time estimate of the disturbance is designed. Second, a controller that guarantees the tracking errors remain in a prescribed region without continuous updates is proposed. Third, a dynamic triggering condition that will not fail under the background of the actual engineering period sampling is proposed. Simulation results illustrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

This paper addresses the post-fault selection of an actuators configuration for flow-based networks with back-up components. The proposed reconfiguration methodology consists of an offline and an online phase. On the one hand, an offline analysis looks for the minimal configurations for which the economic cost of the (best) steady-state trajectory that can be achieved using a robust model predictive control (MPC) policy is admissible. On the other hand, at fault detection time, an online search for the best actuators configuration to cope with the transient induced by the fault is conducted in the superset of each minimal configuration calculated offline. With this strategy, the final new configuration is computed by sequentially solving a set of mixed-integer programs whose constraints are derived from single-layer robust MPC schemes coupled with local controllers designed for the a priori minimal configurations identified offline. A portion of a water transport network is used to show the performance the proposed solution. • Methodology for post-fault actuators configuration selection in flow-based networks. • Offline search for confs. with an economically admissible steady-state trajectory. • Online selection of the optimal configuration to deal with the fault-induced transient. • Simulation results show good performance in a large-scale water transport network. [ABSTRACT FROM AUTHOR]

The rapid evolution of in-orbit manufacturing will enable the fabrication of low-cost, large-scale space structures. In particular, the use of 3D printing technologies will remove traditional payload constraints associated with launch vehicles, due to fairing size and launch loads, thus allowing the construction of larger and lighter structures, such as orbiting solar reflectors. These structures will require efficient attitude control systems, able to provide the necessary torque for maneuvers and to counteract perturbations, such as gravity gradient and solar radiation pressure. In this paper, a top-level overview of actuator performances for orbiting solar reflectors is provided, and scaling laws associated with the required actuator mass and input power are developed. For each class of actuator, upper bounds on the maximum size of the structure which can be effectively controlled are presented. The results can also be extended to other classes of large planar Earth-pointing structures such as solar power satellites, solar sails, or large antennae. [ABSTRACT FROM AUTHOR]

• An ESO-based controller is proposed for the attitude control of spacecraft with unknown faults. • The event-triggered policy reduces the effects of constants on the final convergence regions. • The controller reduces the frequency of data transmission and actuators updates. An event-triggered control strategy based on extended state observer (ESO) is proposed for the attitude tracking problem of small plug-and-play spacecraft with uncertain inertia parameters, external disturbances, and actuator faults. A simplified controller is developed based on the angular velocity and the general disturbances estimated by the provided ESO using the information of the system inputs and the angular velocities. In the designed event-triggered sampling mechanism, a state-dependent event-triggered strategy determines the triggering instant of the controller to reduce the frequency of information transmission between the controller and the actuator. In comparison with the previous literature, this paper considers uncertain inertia parameters, external disturbances, and actuator faults as general disturbances estimated by ESO, especially for the actuator faults. The inputs of ESO are the error of the angular velocities, which can simplify the controller design. Moreover, the designed ESO can effectively attenuate the influence of measured noises generated by the gyroscopes. The proposed event-triggered policy balances the performance of event-triggering and the control stability performance, which reduces the final state convergence regions without increasing more triggering times compared to existing studies. Furthermore, the investigated policy achieves Zeno-free triggering. Numerical simulations verify theoretical results. [ABSTRACT FROM AUTHOR]

In this paper, two event-triggered algorithms are investigated to reduce the consumption and occupation of system resources for attitude tracking control of spacecraft system under external disturbances, model uncertainties, actuator failures, and limited communication. The first robust controller is designed with the triggering condition based on a time-based exponential function that has a dynamically decreasing trigger threshold. To improve the first controller, the second controller with the adaptive triggering condition based on a time-based exponential function is established to facilitate the realization of a comprehensive combination of feedback compensation mechanism and event-triggered control theory. It follows from the theoretical analysis that asymptotic convergence and Zeno-free are achieved under the proposed controller. Simulation results are provided to verify the effectiveness of the developed adaptive event-triggered fault-tolerant control laws. [ABSTRACT FROM AUTHOR]

In this paper, the hypersonic shock-shock interaction control using plasma actuator array is experimentally studied to explore a new surface thermal protection method of hypersonic aircraft. The typical flow structure is produced by a double-wedge model abstracting from the rudder component, and the high schlieren imaging, as well as pressure-sensitive paint/temperature-sensitive paint measurement system, are adopted for flow diagnostics with and without actuation. The results shows that the shock-shock interaction system can be controlled by the plasma actuator array in Ma = 6.0 and Ma = 8.0, and the latter case has a better control outcome where the complicated shock-shock interaction system can be modified to one single oblique wave structure. It indicates that the heat flow amplification effect induced by shock-shock interaction can be alleviated. Also, the increase in energy deposition is proved to have a positive impact on the control outcome, namely the higher energy deposition brings in a better control effect. At last, a preliminary conceptual model is established to reveal the probable thermal protection mechanism. The virtual curved compression surface produced by the high-energy plasma actuator array plays an important role in achieving shock-shock interaction control. • A hypersonic surface thermal protection method via shock-shock interaction control using plasma actuator array is proposed. • The complicated shock-shock interaction system can be modified to one single oblique wave structure. • A conceptual model is established to reveal the mechanism of shock-shock interaction control. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrowetting-on-dielectric (EWOD) phenomenon is widely employed for liquid actuation at the micro scale. Due to its simple structure, low cost, low power consumption and fast response speed, diverse applications are developed and commercialized based on EWOD, such as digital microfluidics, tunable lenses, electronic displays, small-scale propellers etc. However, the liquid actuation with EWOD requires a high-voltage but low-current power source. The accessory equipment (e.g., waveform generator and amplifier) not only attenuates the benefits originated from microscale liquid actuation, but also limits its portability, wearability, and environmental friendliness of the EWOD inspired applications. Triboelectric nanogenerator (TENG) is a promising technology to convert arbitrary mechanical energy to electricity based on triboelectrification and electrostatic induction. The output electric signal shows a high-voltage but low-current property which well matches the demands in EWOD devices. This paper reviews the technical advances in the TENG powered EWOD devices developed in recent years. The mechanisms, structures, and performance of each application are reviewed. The challenges and future perspectives are put forward. The review and discussion in this study open up opportunities for the development of TENG and EWOD based self-powered liquid actuators. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new form of TiO 2 NWs@PDA@nrGO hybrid filler was synthesized using three substances: TiO2 NWs, PDA, and nanosized rGO. • The addition of TiO 2 NWs@PDA@nrGO greatly improved the dielectric constant and actuated strain of silicone rubber. • A new type of cone-type actuator was created through TiO 2 NWs@PDA@nrGO/PDMS composite. Dielectric elastomer actuators (DEAs) have versatile applications in soft robotics, medical devices, and environmental monitoring, making them a highly anticipated area for future applications. On the other hand, developing DEAs exhibiting high strain at low voltages remains challenging. This paper reports a strategy for enhancing the actuating performance of polydimethylsiloxane (PDMS) at low voltages by preparing a hybrid filler comprised of TiO 2 nanowires (TiO 2 NWs), polydopamine (PDA), and nano-sized reduced graphene oxide (nrGO). This hybrid filler, merging the virtues of these three materials, was added at 15 parts per hundred of rubber (phr), resulting in a 2.3-fold increase in the dielectric permittivity of PDMS while mitigating the increase in loss tangent and enhancing efficiency. Actuators fabricated using this composite exhibited the highest deformation at 10 phr, reaching approximately 27.31 % (at 28 V/µm), representing a remarkable 15.2-fold improvement compared to pure PDMS. Moreover, even at a low voltage of 1.6 V/µm, they displayed a substantial actuated strain of 2 %. This novel strategy for manufacturing hybrid fillers is a promising example of enhancing the performance of DEAs, offering innovative solutions for future technological advancements. [ABSTRACT FROM AUTHOR]

This paper proposes a set of digitalisation indicators focused on measuring the different digital capabilities and infrastructure of electricity distribution systems, as opposed to previous indicators which have mainly focused on performance and quality of service aspects. The indicators are classified according to the pillars of digitalisation: sensor and actuator, connectivity, data processing, and digital culture. They are use-case-agnostic and do not require a huge amount of information. In addition to this, three possible new applications of these indicators for distribution system operators and regulatory authorities are identified and discussed. The extensive use of these indicators in Europe could allow the development of fruitful collaborations between distribution system operators, allow the identification of cause–effect relations between grid performance and digital infrastructure, and improve the replicability of innovative smart grid solutions. However, this will only be possible if regulators promote the adoption of the proposed indicators and the dissemination of their results. • Smart grid indicators are required by European Directive 2019/944. • Indicators on sensors/actuators, connectivity, data processing, and digital culture. • Indicators to provide an overview of the distribution grid. • Indicators to study relation between performance and digital infrastructure. • Indicators to generate information for the replicability of solutions. [ABSTRACT FROM AUTHOR]

The hydraulic actuator system (HAS) for wet clutches in heavy-duty vehicle transmissions is required to have a fast response and high precision in the pressure regulation procedure. Conventional pressure control valves for HAS are almost slide spool structures, which perform a large flow force at a high flow rate. An open-center spool structure is designed and developed in this paper, which is a combination of a traditional slide spool and a valve sleeve. It has an orifice-groove combination throttling orifice, which can take into account the large through-flow capacity and small flow force. Firstly, to deeply understand the mechanism of pressure variation in the clutch chamber, a high-fidelity dynamic characteristic mathematical model of HAS considering the oil temperature is proposed. Secondly, the functional relationship between the oil temperature on the medium physical property parameters and the orifice thermal flow parameters in the model is deduced in detail. An experimental bench to measure the pressure valve dynamic performance and actuator pressure regulation characteristics in a wide temperature domain is then designed and implemented to validate the accuracy of the simulation model. Finally, the mechanisms of oil temperature and system pressure on pressure impact and pressure response are quantitatively analyzed in association with a supervised learning algorithm. The feasible domains of the two adjustable variables are also explored. This study provides a new perspective on dynamic control and energy saving of HAS pressure valves and a new method for the prediction of HAS performance under complicated operating conditions. • The orifice migration and straightening effect of OPRV under thermal flow conditions are investigated. • A maximum HAS pressure error of 0.8 bar between simulation and experiment is obtained. • A prediction surrogate model for actuator performance is proposed by utilizing RBF. • The feasible domain of oil temperature and system pressure is proposed for the shift impact. [ABSTRACT FROM AUTHOR]

One possible approach for saving structural mass and related emissions is to design adaptive load-bearing structures, i.e. actively reducing deformations under changing loads through actuation. This paper describes the application of a methodology based on influence matrices to identify a feasible actuator size for actuator placement in reinforced concrete slabs under multiple load cases. The design is implemented in a physical prototype comprising a concrete slab with a clear span of 2 m x 2 m, being equipped with fluidic actuators that are controlled via a cascade controller. Experimental tests show that the displacement response of the adaptive slab under twice the design load can be kept equal to that of the passive slab under the design load. Thus, proof of concept is provided that considerable material savings can be achieved by employing integrated fluidic actuators in two-way slabs. • The first physical implementation of an actuation concept for two-way concrete slabs in an experimental test setup. • The computation of design spaces for an actuator placement for multiple load cases based on influence matrices. • Experimental verification of a controlled displacement compensation under multiple load cases. • Proof of performance increase by employing fluidic actuators in two-way slabs regarding displacement response by 100%. • Proof of concept for considerable material savings by employing integrated fluidic actuators in two-way slabs. [ABSTRACT FROM AUTHOR]

• A temperature-dependent self-sensing actuation strategy is proposed based on a self-sensing magnetostrictive actuator. • The influence of temperature on self-sensing is investigated by a theoretical model that considers temperature-dependent hysteresis. • A self-sensing based control method with rate-dependent hysteresis compensation is developed by combining adaptive feedforward with PID feedback. • A temperature-controlled experimental platform is fabricated to verify self-sensing precision positioning at different temperatures. The self-sensing actuator that integrates both actuation and sensing functions is an effective way to simplify the structure of electromechanical systems. This paper proposes a temperature-dependent self-sensing actuation strategy based on a self-sensing giant magnetostrictive actuator (SSGMA) by sensing online stiffness. Utilizing the developed model considering temperature-dependent hysteresis nonlinearity, the self-sensing output characteristics of SSGMA are first evaluated. The self-sensing based control system is then designed in detail. The relationship between the self-sensing signal and the output displacement of SSGMA at different temperatures is constructed by General Regression Neural Network (GRNN) model for fast recognition by the controller. On this basis, a composite control scheme that takes into account rate-dependent asymmetric hysteresis nonlinearities and combines an adaptive feedforward controller with PID feedback controller is proposed for precision actuation of SSGMA. Finally, a temperature-controlled experimental platform is assembled for verification. Experimental results demonstrate that, based on the developed model, the SSGMA is capable of accurate self-sensing output at temperatures of 22 °C, 40 °C, and 70 °C, respectively. The SSGMA with the proposed control method enables the synchronous and precise self-sensing positioning of step and multiple-frequency sinusoidal expectations at different temperatures. [Display omitted] [ABSTRACT FROM AUTHOR]

• Deeply analyzed the primary factors affecting the performance of dielectric elastomer actuators. • Systematically reviewed the different performance enhancement strategies for dielectric elastomer actuators. • Comprehensively summarized the various bio-inspired applications of dielectric elastomer actuators. • Challenges and future research directions in the development of dielectric elastomer actuators are discussed. • This work lays the foundation for the development and flexible application of novel dielectric elastomer actuators. Compared to traditional robots, soft robots have more intriguing performance. Dielectric elastomer actuators (DEAs) are the key components of soft robots. Analyzing various aspects of dielectric elastomer materials and their effects on the electro-mechanical performance of DEA is crucial for enhancing their overall performance. This paper presents a meticulous review of electro-responsive DEAs, with a particular emphasis on analyzing the influence of optimization strategies on the performance of DEAs: filler reinforcement, chemical modification, physical blending, structural design, and other reinforcement techniques. It comprehensively analyzes the application of bio-inspired DEA-based soft robots and provides an outlook on the potential future development directions of DEAs. Through the development of novel dielectric elastomer materials, research on structural optimization methods, establishment of reinforcement mechanisms, and the design of the next generation of soft robots, it is anticipated that DEAs will achieve heightened energy density, augmented electro-responsive deformation, and improved stability in the field of intelligent robotics. This work contributes constructive insights for the construction and widespread applications of DEAs in the future, and is significant for the enhancement of the performance of novel elastomeric materials. [ABSTRACT FROM AUTHOR]

A novel fault diagnosis procedure is proposed in this paper to estimate faults using a linear parameter varying (LPV) model whose scheduling parameters depend on the fault. A wrong determination of the operating conditions could lead the system to an undesired performance or even to an unstable situation, when classical fault diagnosis approaches are applied. This paper addresses this issue by formulating fault diagnosis as a dynamic optimization problem, solved by using a novel hybrid technique that combines a Luenberger-based observer with artificial intelligent (AI) optimization-based algorithms. The observer supervises the health of the system, while AI-based algorithms are able to reconstruct the faulty signal in real-time when the observer determines that the system is under a fault. The efficiency of the proposed fault diagnosis scheme, the three AI-based algorithms based on artificial bee colony and particle swarm optimization, and the gradient-based algorithm developed in this paper, are assessed using a numerical example. [ABSTRACT FROM AUTHOR]

In 2017, Technische Universität Berlin (TU Berlin) has launched the first space-rated fluid-dynamic actuator (FDA) on the TechnoSat mission. This type of actuator is unique with respect to its dynamic properties, as it offers a very high torque but limited angular momentum storage capabilities in comparison to reaction wheels (RWs). In combination with the tetrahedron RW assembly featured on the spacecraft, a unique combination of attitude control actuators has been formed. The spacecraft axis parallel to the FDA is over-actuated, featuring control actuators of contrasting nature which offers novel options in terms of spacecraft operations. However, with the camera axis on TechnoSat being aligned parallel to the actuator's axis of rotation, there is limited operational use to this setup. In July 2019, TU Berlin launched Berlin Experimental and Educational Satellite 9 (BEESAT-9) – the first CubeSat featuring a set of three orthogonal RWs and a single picosatellite fluid-dynamic actuator (pFDA) for attitude control. The camera axis of BEESAT-9 is perpendicular to the actuator axis, and therefore allows the demonstration of the proposed novel modes of operation. Among the proposed modes is an artificial increase of the swath and the acquisition of stereo images of multiple, successive targets on the ground. Crucial to these operation scenarios is the control allocation between the RW assembly and the single pFDA. This paper first introduces the spacecraft and describes the proposed novel modes of operation that are enabled by the actuator combination realized on BEESAT-9, followed by a review of the state of the art of control allocation for over-actuated spacecraft. The main part of the paper comprises a description of the implementation of the dynamics models of the attitude control actuators and spacecraft, followed by a description of the implemented high-level control laws and control allocation methods. Finally, simulation results for the artificial swath increase and the single spacecraft stereo imaging mode are appended and discussed. • Picosatellite fluid-dynamic actuators enable novel modes of satellite operation. • Control allocation enables combination of novel actuator and reaction wheels. • First CubeSat with fluid-dynamic actuator and reaction wheels launched in 2019. • Attitude maneuvers in the orbit plane enable stereo imaging from single spacecraft. • Attitude maneuvers out off the orbit plane enable artificial swath increase. [ABSTRACT FROM AUTHOR]

As a major obstacle to high performance milling, chatter will inevitably decrease tool life, material removal efficiency and workpiece surface quality. Active control based on actuators for chatter suppression has been developed for a long time. However, in traditional active control, the feedback signals are usually time domain vibration signals, which will mitigate both chatter frequencies and normal frequencies, including rotation frequency and its frequency multiplications. In fact, rotation frequency and its frequency multiplications belong to normal cutting phenomenon, which don't need to be suppressed. Therefore, in traditional control strategies, more energy is wasted due to normal frequencies, which cannot obtain the optimal performance and causes the saturation effect of actuators. In order to solve this problem, this paper realized milling chatter suppression based on the adaptive vibration reshaping, which can precisely modify and control the milling vibration frequencies in frequency domain. Hence, the required control forces provided by actuators will decrease a lot, which can optimize the actuator performance and alleviate the saturation effect. Simulation results show that the adaptive vibration reshaping can suppress chatter frequencies effectively without changing rotation frequency and its frequency multiplications, which satisfies the initial control requirement for optimization of actuator performance. Besides, the convergence analysis, the noise resistance performance analysis, the control delay analysis and the chatter frequencies identification errors analysis are also presented for better facilitation to milling chatter suppression. Finally, contrastive milling tests are implemented on a three-axis milling machine. Experimental results show the designed control algorithm can decrease chatter frequencies, while having a little influence on normal frequencies. [ABSTRACT FROM AUTHOR]

This paper investigates a nonlinear output feedback fault-tolerant control method for the hypersonic flight vehicles with non-affine actuator faults. Compared to the existing investigations, with little aerodynamic knowledge, the proposed controller tackles three practical issues simultaneously, including the inaccurate onboard measurements of the flow angles, unknown non-affine actuator faults and actuator saturation. Drawing support from the differentiator technique, an estimation method for the unmeasured flight path angle is devised, and then an available transformed error variable is defined to construct control laws. Tracking differentiators are introduced to establish uncertainty observers for estimating the unknown model functions including the influences caused by the non-affine actuator faults, and tackle the "explosion of terms" inherent in backstepping. Besides, to improve the controller's performance when the actuator saturation happens, a novel anti-windup strategy is developed to settle the problem that many existing anti-windup strategies are not workable if the non-affine actuator faults happen. Finally, comparative simulation results are provided to demonstrate the effectiveness and superiority of the proposed method. • Three usual practical issues existing in HFV control are tackled simultaneously. • Superior result can be obtained even if the actuator faults and saturation happen. • A novel anti-windup strategy is devised considering actuator faults. • The proposed method is established with almost no aerodynamic knowledge. [ABSTRACT FROM AUTHOR]

This paper proposes a fault-tolerant nonsingular fixed-time control scheme based on neural networks (NNs) for spacecraft maneuver mission subject to actuator faults, unknown external disturbance and parametric uncertainty. The pose dynamic model of the rigid spacecraft is derived with unknown external disturbance and parametric uncertainty. A novel adaptive neural control law is proposed to estimate and compensate for the lumped system faults or uncertainties. Based on the adaptive neural control law, a nonsingular fixed-time terminal sliding-mode (NFTSM) controller is developed to ensure the fixed-time stability of the closed-loop system via the Lyapunov analysis. The singularity in the controller design can be directly avoided with no prior knowledge of lumped disturbance' upper bound. The controller can speed up the convergence rate with improved control accuracy. Moreover, the settling time for the system states is independent of the initial conditions. Finally, comparative simulations are carried out to prove that the proposed control scheme has strong robustness and fault tolerance. [ABSTRACT FROM AUTHOR]

The design of smart structures is challenging because of the integrated electromechanical modelling and optimization of actuators, sensors and load-bearing structures. To simplify the design process, it is common to decouple some of the components and physics and develop each part separately, which could lead to suboptimal systems. To improve the overall design of active structures, we propose an integrated and fully coupled design methodology for a certain class of smart structures. Specifically, this paper presents a numerical framework for the simultaneous application of density-based topology optimization of multi-material conductive compliant mechanisms and a composite multi-layered geometry-projection method for the optimization of the size, position and orientation of embedded piezoelectric stack actuators. Their electromechanical properties are represented in a continuum-based setting by an orientation- and geometry-dependent equivalent material model and their activation depends on the distribution of conductive material in the structure. Furthermore, a novel constraint on the polarization of the actuators is proposed to avoid unwanted designs that could cause their mechanical degradation. A set of numerical examples is analysed and discussed. The proposed framework exhibits promising results, with significant improvements in comparison to a benchmark problem. • Strongly-coupled multi-material smart structure design. • Embedded piezoelectric stack actuator (PSA) model, with length-dependent properties. • Composite multi-layered geometry projection-based modelling of the PSAs. • Geometry with flat ends described by a rectangular signed-distance function. • Introduction of a novel piezoelectric actuator polarization constraint. [ABSTRACT FROM AUTHOR]

In future tokamak devices, the control system will have to handle several control goals simultaneously with a limited number of actuators in long and high performance discharges. One of the critical roles of the future control systems will be the management of actuators, which would assign the most convenient available actuators primarily to the control goals of the highest importance at the time. Such a system would consist of a discharge program defining the experiment, a discharge supervisor making automatic high level decisions in real time and a component handling the actuators at a lower level: The virtual actuator, which is a software object responsible for distributing the controller commands to a set of selected actuators. This paper describes the implementation of a virtual actuator for all 8 gyrotrons of ASDEX-Upgrade. We also describe the intended use of the virtual actuator for three experiments: β control using ECRH, a disruption avoidance strategy, and electron temperature profile control. The paper also gives an overview of future actuator management developments at ASDEX-Upgrade: extension to all heating sources, inclusion of mirrors for ECRH, and intelligent real time distribution of the actuators between the control goals. [ABSTRACT FROM AUTHOR]

In recent decades, shake table real-time hybrid simulation (RTHS) has emerged as a promising seismic testing approach for complex engineering structures. However, the current shake table RTHS systems with actuators typically install the dynamic actuators on a reaction wall outside the table, which introduce interaction issues between the dynamic actuators and the shake table. This study proposes a potential improvement by developing a shake table RTHS platform with onboard actuators. The platform incorporates a 6 m × 9 m large-scale shake table where the physical substructure, two dynamic actuators, and the reaction frame are all positioned. To validate the effectiveness of the developed platform, a two-story steel frame is tested by both full structure shake table test and substructure shake table RTHS. In the shake table RTHS, the lower part of the frame serves as the physical substructure and is simultaneously loaded by the shake table and dynamic actuators, while the upper part is numerically analyzed in OpenSees, using OpenFresco and Simulink as intermediate softwares. The test results demonstrate that the developed shake table RTHS platform provides reasonable predictions to the structural seismic responses. In addition, time delay is optimized using both inner and outer loop compensators, highlighting the effectiveness of inverse compensation and adaptive time series (ATS) compensation schemes. This paper successfully develops a shake table RTHS platform using a large shake table with onboard dynamic actuators, providing a valuable seismic testing platform for RTHS of large-scale complex engineering structures. • Developed an advanced RTHS platform using a large shake table with onboard actuators. • Validated the shake table RTHS platform through full structure and substructure tests on a two-story steel frame model. • Optimized inner-loop controller parameters to reduce the system time delays for enhanced performance. • Employed outer-loop compensators (inverse and ATS) to further mitigate the system time delay. [ABSTRACT FROM AUTHOR]

This paper investigates fault-tolerant learning control for air-breathing hypersonic vehicles (AHVs) subject to parametric uncertainties, external disturbances, and actuator faults. By treating the flexible dynamics as equivalent disturbance, the AHV model can be decomposed into velocity subsystem and altitude subsystem. An intelligent fault diagnosis approach is deployed to estimate the actuator fault information for each subsystem sequentially. Furthermore, combined with a fixed-time neural disturbance observer, composite learning control is deployed to construct control commands using the historical stack to improve the learning accuracy, while compensating for lumped disturbances, including fault diagnosis errors and external disturbances. The designed controller addresses the fault-tolerant tracking problem by combining offline and online learning strategies, which is a significant advantage over other existing AHV controllers. Simulation results validate the effectiveness of the fault-tolerant learning control. • Fault-tolerant learning control is proposed for hypersonic vehicles. • Actuator-fault problem is intelligently accommodated. • Parametric uncertainties and disturbances are neuro-adaptively handled. [ABSTRACT FROM AUTHOR]

• Provides guidance for the available configuration of the spring roll actuators. • Clarifies the conditions for the actuator electromechanical failure. • Develops the system damping as a function of the frequency by experiment. • Exploits the kinematic equations to characterize the motion of a crawling robot. Dielectric elastomer actuators (DEAs) have received widespread attention in human-robot interaction and biomedical engineering due to their merits of large deformation, fast response, and excellent biocompatibility. The cylindrical DEA is one of the preferred structures, combining flexibility and compactness. However, the inherent non-linear behavior between the voltage and the actuator makes predicting the output performance during the design process difficult and encumbers its application, especially for multiple degrees of freedom. Herein, a dielectric elastomer spring-roll bending actuator capable of multimodal spatial locomotion using three pairs of electrodes is proposed in this paper. The electromechanical coupling behavior of the actuator under unidirectional bending deformation is described by analyzing the stress process between the spring and the film. The system's damping and excitation frequency relationship is obtained via a semi-analytical method. The experimental results validate the actuator design and show good consistency with the theoretical model. A prototype soft robot capable of running and turning is successfully demonstrated. The actuator also achieves various spatial trajectory paths via the cooperation between electrodes. Thus, the proposed scheme and modeling shed new light on the design and control of dielectric elastomers for multimodal deformation. [Display omitted] [ABSTRACT FROM AUTHOR]

In the process industry, the actuator has complex operating processes. Its steady working conditions are easy to change. Moreover, it is in a dynamic process for long periods of time. These phenomena reduce the accuracy and timeliness of many condition monitoring (CM) methods. In this paper, a fault detection mechanism considering the complex operating processes of the actuator is proposed. One of its main feature is that it can detect faults under steady state regardless of variable load changes. The other is that it has ability to detect faults during dynamic processes refusing the interference of nonlinearity and dynamic characteristics. Firstly, an actuator data model library based on historical data is established offline. Secondly, in the online situation, after the R indicator divides the testing data into steady state or dynamic, it is input into the model library to obtain a standard training set. Finally, the steady-state/dynamic fault detection module will determine whether a fault has occurred based on the testing data and the training set. Moreover, open-loop experiments based on the DAMADICS (Development and Application of Methods for Actuator Diagnosis in Industrial Control Systems) platform and closed-loop experiments based on the water tank system are designed. These experiments show that, compared with other methods, the proposed fault detection framework has better monitoring performance during complex operating processes of actuators. • A novel actuator fault detection method is proposed. • It can deal with various complex operating processes containing steady and dynamic state. • It contains two novel extended non-negative matrix factorization algorithms. • The presented mechanism is verified by simulations and experiments. [ABSTRACT FROM AUTHOR]

The present paper deals with the control problem of vertical takeoff vertical landing (VTVL) reusable launch vehicle (RLV) under actuator faults and multi-type attitude constraints (unilateral constraints, symmetric/asymmetric bilateral constraints, or without constraints). A semi-globally smooth control system is proposed based on a novel barrier function (BF) to realize the finite-time convergence of attitude tracking errors into a small neighborhood of the origin. Moreover, the attitude constraints unviolated under multiple disturbances are guaranteed. To further enhance the disturbance rejection ability, a BF-based adaptive disturbance observer (DO) is derived and incorporated into the control system, which is responsible for reconstructing the disturbance in finite time. The proposed control systems are characterized by the following four points. One is to ensure the finite-time convergence of attitude tracking errors and guarantee the non-violation of constraints without requiring any prior information regarding the Lipschitz constant and upper bound of the disturbance. The second is to provide a unified instrument for control problems with the aforementioned multi-type state constraints. The third is the smoothness property contributing to the chattering-free convergence of attitude tracking errors. The high performance and robustness concerning non-Lipschitz disturbance (such as the sudden actuator faults) are the fourth. Ultimately, the effectiveness of the proposed control systems was demonstrated by the numerical simulation results. • Barrier function-based semi-globally smooth controller for finite-time convergence. • Barrier function-based adaptive observer for finite-time disturbance reconstruction. • Unification for bilateral/unilateral constraints or without constraints. • No need of information of the upper bound and Lipschitz constant of the disturbance. • Fast re-estimation and re-stabilization after the sudden actuator faults. [ABSTRACT FROM AUTHOR]

The virtual control strategy for mechanical systems has been recently proposed (Gnucci and Marino, 2021) in the context of under-actuated mechanical systems. Such a strategy views and represents an under-actuated mechanical system as a fully actuated system with virtually added inputs and outputs having to satisfy, through a suitable choice of the virtual output reference signals, the virtual input zero-equality constraint: the related adaptive tracking control problem is then solved through standard design techniques. This paper exhibits a twofold aim. The first one is: to enlarge the concept of zero-input constraint and thus naturally adapt the virtual control approach to the case in which an actuator fault can occur. The second aim is: to show how the application and transposition of such an adaptation to two well-known classes of nonlinear systems (special systems in multi-variable tracking form with two inputs and outputs under actuator faults; one-relative-degree, single-input, single-output systems in output feedback form under input saturation) not only own strong connections with the conditioning technique, originally conceived in the context of anti-windup problems under input constraints, but they also gain original results. [ABSTRACT FROM AUTHOR]

This paper proposes a novel impact welding method named water-augmented vaporizing foil actuator welding, in which liquid water is introduced to alter the foil's vaporization process, thus altering the induced driving pressure and the final welding performance. A series of comparative experiments were performed to confirm the effectiveness of the process and to understand the underlying mechanism. The proposed process decreased the lower-bound required discharge energy by 58–69%, increased the peel strength by 30–60%, and significantly reduced the variability in the critical standoff distance at the lower bound of the weld window. In addition, the proposed process resolved the robustness issue by producing a much more regular and repeatable shape of the weld area compared to conventional VFAW. Furthermore, three potential mechanisms have been proposed to explain the process improvement: the added water 1) increased the electrical energy deposition, 2) introduced additional energy from the aluminum-water chemical reaction, and 3) provided a more efficient force-transfer medium. In summary, this paper introduces a novel impact welding method with much improved process capability and robustness compared to conventional vaporizing foil actuator welding. In addition, due to its simplicity, this method may be easily extended for other forms of impulse metalworking, which may stimulate a wide interest for the community of high velocity metalworking. [ABSTRACT FROM AUTHOR]

Considerable attention has been paid to the exploration of moon, especially the construction of lunar habitat. However, few studies are found working on the construction equipment being suitable for trans planetary transportation, assembly, and working in lunar environment. This paper proposed a novel cable-driven printer used to build lunar architecture. The pose measurement and control strategy of the printing system is proposed. To study the reconfiguration characteristic of the cable-driven printer, several trees with arbitrary locations were selected as the rack to reconstruct the system outdoors. The key factors such as the sensitivity of pose deviation to system parameters affecting the reconstruction performance is discussed. The forming space of the cable-driven printer is analyzed theoretically and the forming ability of the system is verified experimentally. It is found that the cable-driven printer has the advantages of simple structure, small weight, large forming space and good reconfiguration characteristic, which shows the great potential of the proposed cable-driven printer in the construction of lunar architecture. • We present a novel cable-driven printer for lunar architecture. • The printer can be easily reconstructed on randomly selected lunar terrain. • The printer has a large ratio of forming space to mass. • We proposed the measurement and control strategy of the printer. • The printer has a flexible printing posture thanks to a 6-DOF actuator. [ABSTRACT FROM AUTHOR]

• Generation of traveling waves in one-dimensional beams by piezoelectric actuation. • The design variables are two sets of electrodes including the polarization direction. • The deflection of the beam is computed by modal decomposition. • An interpolation scheme for the selection of the set of electrodes is proposed. In this paper a milli-sized traveling wave actuator is designed by optimizing the polarization direction. Two different sets of electrodes are needed to generate the traveling wave. The topology optimization method is used to get the optimal sets of electrodes that minimize the difference between a pure traveling wave and the deflection generated. Classical issues in topology optimization problem such as mesh-dependence or intermediate densities are overcome by using filtering and projection techniques. Examples with different boundary conditions are presented in order to validate the model. [ABSTRACT FROM AUTHOR]

Based on the delta operator approach, a new method of actuator fault estimation for a two-stage chemical reactor system is presented with time-delay and outside disturbances. Firstly, a nonlinear delta operator mathematical model is established to describe the two-stage chemical reactor systems by using the mechanism analysis method. In order to estimate the actuator fault, the proportional–integral observer (PIO) is employed as the state estimator. Meanwhile, a novel delta operator-based actuator fault estimation algorithm is proposed. Then, by means of the Lyapunov–Krasovskii functional technique, sufficient conditions are derived to guarantee that the error system is asymptotically stable with a predefined H ∞ performance index. Next, the desired PIO can be designed. Finally, simulation results are given to illustrate the effectiveness of the proposed methods. • A novel proportional and integral fault estimation algorithm is firstly proposed. • This method connects continuous-time systems and discrete-time systems. • A practical simulation example is given to verify the method. • The system model in this paper is more universal and practical. [ABSTRACT FROM AUTHOR]

In this paper, adaptive control schemes are proposed for the trajectory tracking control of a free-flying space manipulator with guaranteed prescribed performance in the presence of parametric uncertainties, external disturbances, and actuator saturation. Both full-state feedback control and output feedback control are considered. First, a model-based controller is designed by using the barrier Lyapunov function (BLF) to prevent the position tracking errors from exceeding the prescribed performance bounds. Then, a full-state feedback controller is designed by using the radial basis function neural network (RBFNN) to compensate for the lumped uncertainties. Finally, an output feedback controller is designed by using a high-gain observer to estimate the velocity of the space manipulator. Rigorous theoretical analysis for the semi-global uniform ultimate boundedness of the whole closed-loop system is provided. The proposed output feedback controller can guarantee the position and velocity tracking errors converge to the small neighborhoods about zero, while ensuring the position tracking errors within the prescribed performance bounds even without using velocity measurements. To the best of the authors' knowledge, there are really limited existing controllers can achieve such excellent control performance in the same conditions. Numerical simulations demonstrate the effectiveness and strong robustness of the proposed control schemes. • The trajectory tracking control of a free-flying space manipulator is investigated. • Both full-state and output feedback control is considered. • The prescribed performance is guaranteed by using the barrier Lyapunov function. • The semi-global uniform ultimate boundedness of the whole closed-loop system is proved. [ABSTRACT FROM AUTHOR]

The detection and identification for aircraft icing and actuator/sensor fault has been a lasting topic in flight safety researches. The current algorithms are usually tailored for some specific cases (faults/icing locations, magnitude, etc.). Although the performance of the algorithm in the designated cases may be good, the transferring of it to other different cases is usually heavy as parameters tuning or even algorithm redesigning may be required. In this paper, the author advocates exploring a comprehensive scheme that balance both good performance and wide transferability for different cases. Referring to the current advances in other research communities, we follow the state-of-art Deep Learning (DL) and transfer learning (TL) concepts. A scheme for the icing/actuator fault detection using the DL technique is firstly constructed. The TL is then adopted to transfer this scheme to other different tasks, e.g. fault/icing identification, sensor fault detection. Test results show that the TL-enhanced DL scheme exhibits not only good performance for the designated detection task, but also reflects flexible transferability at low tuning efforts. Via this paper the author advocates furtherly exploring the potentials of the novel DL and TL technique as to advancing the researches/techniques in the flight dynamics and control realm. [ABSTRACT FROM AUTHOR]

Highlights • In contrast with the existing linear large-scale systems literature, a novel cyclic-small-gain condition is introduced to solve the mismatched interconnections of each subsystem. • A novel time-invariant controller is developed to solve the model reference adaptive fault-tolerant problem. • Different from the traditional method to estimate the weight vector on fuzzy logic systems, only the norm of the weight vector is estimated in this paper. Abstract This paper considers the decentralized fault-tolerant model reference adaptive control (MRAC) problem for a class of nonlinear large-scale systems with matched unknown nonlinearity and uncertain time delay interconnections and mismatched interconnections. A novel cyclic-small-gain condition is achieved to show the boundedness of tracking errors. Furthermore, by introducing adaptive mechanisms, a new decentralized fault-tolerant controller is developed. In addition, it is shown that the matched unknown nonlinear functions and the matched uncertain time delay functions can be compensated by the developed controller. Compared with existing large-scale systems results, the proposed method is effective to solve the fault-tolerant MRAC problem for large-scale systems with time-varying delays and mismatched interconnections. Finally, the validity is shown by applying the proposed method to a chemical reactor system with two subsystems. [ABSTRACT FROM AUTHOR]

Zusammenfassung: This paper describes an integrated methodology for finding and assessing architectures of electromechanical actuators with special attention to safety and reliability. The methodology was developed and applied in the framework of the research project DRESS, which aimed to develop and test a highly reliable electromechanical nose gear steering system for a single aisle commercial aircraft. The present paper introduces the integrated methodology proposed for a more systematic design for safety and reliability. Emphasis is placed on the method for finding the most promising candidate architectures that are compliant with the project requirements in general and the safety and reliability requirements in particular. The results obtained by applying the methodology to the DRESS project are presented and discussed. [ABSTRACT FROM AUTHOR]