Distributed Event‐Triggered Adaptive Control for Consensus of Actuator Fault Multiagent Systems With Parameter Uncertainty and External Disturbances

Learning‐based robust control methodologies under information constraints

Semi-global output consensus of discrete-time multi-agent systems with input saturation and external disturbances

Position tracking control of electro-hydraulic single-rod actuator based on an extended disturbance observer

A nonlinear controller based on an extended second-order disturbance observer is presented to track desired position for an electro-hydraulic single-rod actuator in the presence of both external disturbances and parameter uncertainties. The proposed extended second-order disturbance observer deals with not only the external perturbations, but also parameter uncertainties which are commonly regarded as lumped disturbances in previous researches. Besides, the outer position tracking loop is designed with cylinder load pressure as output; and the inner pressure control loop provides the hydraulic actuator the characteristic of a force generator. The stability of the closed-loop system is provided based on Lyapunov theory. The performance of the controller is verified through simulations and experiments. The results demonstrate that the proposed nonlinear position tracking controller, together with the extended second-order disturbance observer, gives an excellent tracking performance in the presence of parameter uncertainties and external disturbance.

In this paper, the leader-follower consensus problem of linear multi-agent systems with unknown dynamics and external disturbances is studied by using the two-player zero-sum game and adaptive dynamic programming. First, we establish the global error dynamic system of the multi-agent system and decouple the global error dynamic system for each agent. Second, we use the two-player zero-sum game theory to deal with external disturbances, and get the generalized algebraic Riccati equation for each agent. Third, based on adaptive dynamic programming, we propose a new algorithm for solving the leader-follower consensus problem for multi-agent systems with unknown dynamics. At last, Simulation results are further presented to show the effectiveness of the proposed algorithm.

Direct adaptive robust tracking control for 6 DOF industrial robot with enhanced accuracy

In this article, the issue of fault-tolerant leader-following consensus under a distributed dynamic event-triggered mechanism is addressed for linear multiagent systems (MASs) in the presence of unknown parameter uncertainties, external disturbances, and actuator faults, including loss of effectiveness and bias, in which the mechanism is with quantized state measurements. Due to the fact that information is transmitted via a bandwidth-limited communication network, a quantized control scheme with a uniform quantizer is introduced for leader-following consensus. In order to decrease the communication load and save the limited communication network resources, a distributed event-triggered mechanism is studied for leader-following consensus problem of linear MASs with quantized state measurements. In the presence of actuator faults, external disturbances, and unknown parameter uncertainties, an adaptive coupling gain for the controller is presented. Based on the Lyapunov function approach, the stability of the closed-loop system and the convergence of consensus errors are proved. Furthermore, the Zeno behavior is excluded for the triggering time sequences. Finally, simulation studies are given to verify the effectiveness of the proposed event-triggered fault-tolerant control scheme.

Adaptive Robust Control of a Class of Multivariable Nonlinear Systems

In this study, the synchronization problem of the faulty chaotic gyrostat master–slave systems using a wavelet-based robust adaptive T-S fuzzy control is investigated. This control system is comprised of a wavelet T-S fuzzy network (TSFN) controller, a feedback controller and a robust controller. Within this scheme, the wavelet TSFN is used in two separate approaches. At the first approach, it is utilized to approximate the nonlinear functions of the gyrostat systems, and at the second approach, it is used to approximate the lumped fault function of the control system. The feedback controller is developed to initially control the underlying system, and a robust controller is an adaptive controller which is used to dispel the effects of the approximation errors on the tracking performance. The parameters of wavelet TSFN and the bound parameter of the robust controller are tuned on-line by the derived adaptive laws based on Lyapunov stability analysis. The wavelet block acts as a feature extractor, reduces the number of fuzzy rules and also acts as a normalization block. The Lyapunov stability of the closed-loop system, robustness against the parameters uncertainties, the external disturbances and the approximation errors, as well as the convergence of the tracking errors and boundedness of all signals in the closed-loop system, are guaranteed. Finally, the synchronization problem of the unknown chaotic gyrostat systems in the presence of parameter uncertainties, external disturbances and actuator faults is simulated to illustrate the effectiveness of the proposed control scheme.

This paper consider the distributed fault-tolerant tracking control problem for linear multi-agent systems with unmatched parameter uncertainties, external disturbances and actuator faults. The considered time-varying actuator fault includes loss of effectiveness, outage and stuck. For the case where the communication graph is undirected and connected, a new distributed fault-tolerant control scheme is proposed. Based on the local state information of neighboring agents, the controller gains are adjusted online according to a designed adaptive mechanism to compensate the effects of actuator faults, external disturbances and mismatched parameter uncertainties on systems. Moreover, on the basis of Lyapunov stability theory, it is proved that all the signals of the closed-loop are bounded and all follower nodes asymptotically tracking to the leader. Finally, an example is included to show the effectiveness of the obtained theoretical results.

<div class="section abstract"><div class="htmlview paragraph">BBW (Brake-by-wire) can increase the vehicle safety performance due to high control accuracy and fast response speed. As one solution of BBW, the novel Integrated-electro-hydraulic brake system (I-EHB) is proposed, which consists of electro-hydraulic booster and hydraulic pressure control unit. The electro-hydraulic booster is activated by an electric motor that driving linear motion mechanism to directly produce the master cylinder pressure. With electro-hydraulic booster as an actuator, the hydraulic pressure control problem is a key issue. Most literatures deal with the pressure control issue based on the feedback pressure signal measured by pressure sensor. As far as the authors are aware, none of the proposed techniques takes into account the pressure sensor unequipped BBW. In this paper, there is no pressure feedback signal, but there is only position feedback signal measured by position sensor for control law design. This paper presents a cascade controller based on a nonlinear observer to track desired master cylinder pressure for a pressure sensor unequipped electro-hydraulic booster in the presence of both external disturbances and parameter uncertainties. The outer pressure tracking loop employs feedforward control law to increase the response speed with desired position of master cylinder piston rod as control output; the inner position control loop is designed using the sliding mode control algorithm. The stability of the overall closed-loop control system is proved on the basis upon Lyapunov theory and then the constraint zone of control parameter is calculated. Finally, the controller performance is verified through bench test. The results show that the proposed nonlinear cascade controller, together with the nonlinear observer, provides good tracking performance in the presence of parameter uncertainties and external disturbances.</div></div>

Anti-saturation adaptive finite-time neural network based fault-tolerant tracking control for a quadrotor UAV with external disturbances

Distributed control gains design for consensus in multi-agent systems with second-order nonlinear dynamics

This paper deals with adaptive robust control of a class of multi-input multi-output (MIMO) nonlinear systems, with parametric uncertainties, unknown nonlinear functions, modelling error and external disturbances. The idea of adaptive robust control Lyapunov functions (ARCLF) is introduced to formulate a general framework of the adaptive robust control. Specific ARCLFs are sought out for different applications, including MIMO nonlinear systems with arbitrary known relative degrees transformable to a semi-strict feedback form, in which unknown parameters are also allowed to enter control channels. The method bridges the gap between adaptive control and deterministic robust control by preserving their advantages, i.e. the asymptotic stability of adaptive control in the presence of parametric uncertainties and guaranteed transient performance with prescribed precision of deterministic robust control in the presence of both parametric uncertainties and unknown nonlinear functions and, at the same time, eliminating drawbacks of each. Simulation results verify the effectiveness of the suggested method.

Guaranteed-performance consensus control for multi-agent systems with external disturbances via event-triggered strategy