Set-Membership Filtering Approach to Dynamic Event-Triggered Fault Estimation for a Class of Nonlinear Time-Varying Complex Networks

The present study addresses the problem of fault estimation for a specific class of nonlinear time-varying complex networks,utilizing an unknown-input-observer approach within the framework of dynamic event-triggered mechanism(DETM).In order to optimize communication resource utilization,the DETM is employed to determine whether the current measurement data should be transmitted to the estimator or not.To guarantee a satisfactory estimation performance for the fault signal,an unknown-input-observer-based estimator is constructed to decouple the estimation error dynamics from the influence of fault signals.The aim of this paper is to find the suitable estimator parameters under the effects of DETM such that both the state estimates and fault estimates are confined within two sets of closed ellipsoid domains.The techniques of recursive matrix inequality are applied to derive sufficient conditions for the existence of the desired estimator,ensuring that the specified performance requirements are met under certain conditions.Then,the estimator gains are derived by minimizing the ellipsoid domain in the sense of trace and a recursive estimator parameter design algorithm is then provided.Finally,a numerical example is conducted to demonstrate the effectiveness of the designed estimator.

Precision motion control for electro-hydraulic axis systems under unknown time-variant parameters and disturbances

This article focuses on asymptotic precision motion control for electro-hydraulic axis systems under unknown time-variant parameters,mismatched and matched disturbances.Different from the traditional adaptive results that are applied to dispose of unknown constant parameters only,the unique feature is that an adaptive-gain nonlinear term is introduced into the control design to handle unknown time-variant parameters.Concurrently both mismatched and matched disturbances existing in electro-hydraulic axis systems can also be addressed in this way.With skillful integration of the backstepping technique and the adaptive control,a synthesized controller framework is successfully developed for electro-hydraulic axis systems,in which the coupled interaction between parameter estimation and disturbance estimation is avoided.Accordingly,this designed controller has the capacity of low-computation costs and simpler parameter tuning when compared to the other ones that integrate the adaptive control and observer/estimator-based technique to dividually handle parameter uncertainties and disturbances.Also,a nonlinear filter is designed to eliminate the“explosion of complexity”issue existing in the classical back-stepping technique.The stability analysis uncovers that all the closed-loop signals are bounded and the asymptotic tracking performance is also assured.Finally,contrastive experiment results validate the superiority of the developed method as well.

Fixed-Time Adaptive Time-Varying Matrix Projective Synchronization of Time-Delayed Chaotic Systems with Different Dimensions

This paper deals with the fixed-time adaptive time-varying matrix projective synchronization(ATVMPS)of different dimensional chaotic systems(DDCSs)with time delays and unknown parameters.Firstly,to estimate the unknown parameters,adaptive parameter updated laws are designed.Secondly,to realize the fixed-time ATVMPS of the time-delayed DDCSs,an adaptive delay-unrelated controller is designed,where time delays of chaotic systems are known or unknown.Thirdly,some simple fixed-time ATVMPS criteria are deduced,and the rigorous proof is provided by employing the inequality technique and Lyapunov theory.Furthermore,the settling time of fixed-time synchronization(Fix-TS)is obtained,which depends only on controller parameters and system parameters and is independent of the system’s initial states.Finally,simulation examples are presented to validate the theoretical analysis.

转动惯量未知的非合作目标角速度估计方法研究

针对转动惯量未知的非合作目标的姿态角速度估计问题,将解算得到的非合作目标的惯性姿态作为测量信息,估计姿态角速度和姿态动力学参数(即转动惯量比).首先,应用非线性控制系统的几何理论对待估计的状态扩展系统进行能观性分析.然后,利用UKF设计相应的滤波估计算法.仿真结果表明,本文所设计的方法能够精确估计出非合作目标的姿态角速度与转动惯量比.

未知时变惯量航天器自适应姿态跟踪容错控制

针对存在未知时变惯量不确定性、执行机构衰退故障和外部干扰力矩的非刚体航天器系统,研究了航天器自适应姿态跟踪容错控制问题,结合非线性鲁棒控制方法、自适应方法、容错控制理论和参数估计方法,提出了一种鲁棒自适应姿态跟踪容错控制器。所设计的控制器克服了执行器故障、惯量不确定性以及外界干扰对系统稳定性的影响,保证了航天器姿态及角速度能够跟踪上时变的期望状态,实现了跟踪误差系统最终一致有界稳定。最后通过数字仿真验证了所提方法的有效性,并且与已有方法进行了对比,说明了所提方法的优越性。

基于未知动态观测器双惯量伺服系统低频主动谐振抑制

针对双惯量伺服系统存在的机械谐振,本文提出了一种基于扰动观测器的滑模主动低频谐振控制方法.利用可测量的电机端的位置信号,对其进行滤波操作得到位置的滤波变量,根据不变流形原理设计未知扰动观测器,实现对传递力矩的在线估计,并将估计值融入到控制器设计中对其进行补偿.为了消除传统滑模存在颤振现象,基于正切函数提出了一种新颖滑模面设计方法.在此基础上,设计了滑模控制器实现了对期望信号的准确跟踪,并利用李雅普诺夫稳定性理论证明了闭环系统稳定性.最后通过实验对比,验证了本文提出的控制策略有效性,此外该算法建构简单不需要计算电机加速度的信息,利于在实际中应用.

Adaptive Iterative Learning Control for Nonlinearly Parameterized Systems with Unknown Time-varying Delay and Unknown Control Direction

This paper proposes a new adaptive iterative learning control approach for a class of nonlinearly parameterized systems with unknown time-varying delay and unknown control direction.By employing the parameter separation technique and signal replacement mechanism,the approach can overcome unknown time-varying parameters and unknown time-varying delay of the nonlinear systems.By incorporating a Nussbaum-type function,the proposed approach can deal with the unknown control direction of the nonlinear systems.Based on a Lyapunov-Krasovskii-like composite energy function,the convergence of tracking error sequence is achieved in the iteration domain.Finally,two simulation examples are provided to illustrate the feasibility of the proposed control method.

Modeling and simulation of a time-varying inertia aircraft in aerial refueling

Studied in this paper is dynamic modeling and simulation application of the receiver aircraft with the time-varying mass and inertia property in an integrated simulation environment which includes two other significant factors, i.e., a hose-drogue assembly dynamic model with the variable-length property and the wind effect due to the tanker＇s trailing vortices. By extending equations of motion of a fixed weight aircraft derived by Lewis et al., a new set of equations of motion for a receiver in aerial refueling is derived. The equations include the time-varying mass and inertia property due to fuel transfer and the fuel consumption by engines, and the fuel tanks have a rectangle shape rather than a mass point. They are derived in terms of the translational and rotational position and velocity of the receiver with respect to an inertial reference frame. A linear quadratic regulator （LQR） controller is designed based on a group of linearized equations under the initial receiver mass condition. The equations of motion of the receiver with a LQR con- troller are implemented in the integrated simulation environment for autonomous approaching and station-keeping of the receiver in simulations.

Adaptive neural control of nonlinear periodic time-varying parameterized mixed-order multi-agent systems with unknown control coefficients

In this paper, we first consider the adaptive leader-following consensus problem for a class of nonlinear parameterized mixedorder multi-agent systems with unknown control coefficients and time-varying disturbance parameters of the same period. Neural networks and Fourier series expansions are used to describe the unknown nonlinear periodic time-varying parameterized function.A distributed control protocol is designed based on adaptive control, matrix theory, and Nussbaum function. The robustness of the distributed control protocol is analyzed by combining the stability analysis theory of closed-loop systems. On this basis, this paper discusses the case of time-varying disturbance parameters with non-identical periods, expanding the application scope of this control protocol. Finally, the effectiveness of the algorithm is verified by a simulation example.

Distributed Adaptive Synchronization of Complex Dynamical Network with Unknown Time-varying Weights

A new approach of adaptive distributed control is proposed for a class of networks with unknown time-varying coupling weights. The proposed approach ensures that the complex dynamical networks achieve asymptotical synchronization and all the closed-loop signals are bounded. Furthermore, the coupling matrix is not assumed to be symmetric or irreducible and asymptotical synchronization can be achieved even when the graph of network is not connected. Finally, a simulation example shows the feasibility and effectiveness of the approach.

Distributed Fault Detection for Consensus in Second-Order Discrete-Time Multiagent Systems with Adversary

This paper is concerned with distributed fault detection of second-order discrete-time multi-agent systems with adversary,where the adversary is regarded as a slowly time-varying signal.Firstly,a novel intrusion detection scheme based on the theory of unknown input observability( UIO) is proposed. By constructing a bank of UIO,the states of the malicious agents can be directly estimated. Secondly,the faulty-node-removal algorithm is provided.Simulations are also provided to demonstrate the effectiveness of the theoretical results.

Non-fragile robust H_(∞)control of nonlinear networked control systems with time-varying delay and unknown actuator failures

Purpose-This paper is concerned with non-fragile robust H_(∞)control problems for nonlinear networked control systems(NCSs)with time-varying delay and unknown actuator failures.The paper aims to discuss these issues.Design/methodology/approach-The system parameters are allowed to have time-varying uncertainties and the actuator faults are unknown but whose upper and lower bounds are known.By using some lemmas,uncertainties can be replaces with the known values.By taking the exogenous disturbance and network transmission delay into consideration,a delay nonlinear system model is constructed.Findings-Based on Lyapunov stability theory,linear matrix inequalities(LMIs)and free weighting matrix methods,the sufficient conditions for the existence of the non-fragile robust H_(∞)controller gain are derived and which can obtained by solving the LMIs.Finally,a numerical example is provided to illustrate the effectiveness of the proposed methods.Originality/value-The introduced approach is interesting for NCSs with time-varying delay and unknown actuator failures.

航天器姿态机动优化容错控制

针对存在未知时变惯量不确定性、外部干扰力矩和执行机构衰退故障的非刚体航天器系统,研究了非刚体航天器自适应优化容错控制问题。首先,为了根据误差变量优化控制增益,设计一种动态增益调整函数实时优化控制增益;然后,基于非线性鲁棒控制方法、动态增益函数调整方法、自适应方法、容错控制理论与参数估计方法,提出一种新颖的自适应优化姿态跟踪容错控制器。所设计的控制器克服了执行器故障、惯量不确定性以及外界干扰的影响,保证航天器姿态及角速度能够跟踪时变的参考轨迹,实现跟踪误差系统最终一致有界稳定;最后,数字仿真结果验证了所提出方法的有效性,而且与已有控制方法相比,该方法具有更高的控制精度和稳定性。

Anti-saturation fault-tolerant adaptive torsional vibration control with fixed-time prescribed performance for rolling mill main drive system

An anti-saturation fault-tolerant adaptive torsional vibration control method with fixed-time prescribed performance for the rolling mill main drive system(RMMDS)was investigated,which is affected by control input saturation,actuator faults,sensor measurement errors,and parameter perturbations.First,we gave a continuously differentiable saturation function to approximate the control input saturation characteristic of the RMMDS,translating the saturation characteristic into the matched uncertainty and unknown time-varying gain in the system.Then,an RMMDS mathematical model with unmatched uncertainty and unknown time-varying gain was developed,taking into account the presence of control input saturation,actuator faults,sensor measurement errors,and parameter perturbations.Based on the established mathematical model,an error transformation model of the roll speed tracking was constructed by the equivalent error transformation method.According to the error transformation model,a barrier Lyapunov function and a novel adaptive controller were studied to ensure that the roll speed tracking error always evolves inside a fixed-time asymmetric constraint.Finally,numerical simulations were performed in Matlab/Simulink to verify the effectiveness and superiority of the proposed control method in suppressing the RMMDS torsional vibration.

Time-varying linear control for tiltrotor aircraft

Tiltrotor aircraft have three flight modes： helicopter mode, airplane mode, and transition mode. A tiltrotor has characteristics of highly nonlinear, time-varying flight dynamics and inertial/-control couplings in its transition mode. It can transit from the helicopter mode to the airplane mode by tilting its nacelles, and an effective controller is crucial to accomplish tilting transition missions. Longitudinal dynamic characteristics of the tiltrotor are described by a nonlinear Lagrangeform model, which takes into account inertial/control couplings and aerodynamic interferences.Reference commands for airspeed velocity and attitude in the transition mode are calculated dynamically by visiting a command library which is founded in advance by analyzing the flight envelope of the tiltrotor. A Time-Varying Linear（TVL） model is obtained using a Taylorexpansion based online linearization technique from the nonlinear model. Subsequently, based on an optimal control concept, an online optimization based control method with input constraints considered is proposed. To validate the proposed control method, three typical tilting transition missions are simulated using the nonlinear model of XV-15 tiltrotor aircraft. Simulation results show that the controller can be used to control the tiltrotor throughout its operating envelop which includes a transition flight, and can also deal with vertical gust disturbances.

Convergence of time-varying net works and its applications

In this study,we present the convergence of time-varying net works.Then,we apply the convergence property to cooperative control of nonlinear multiagent systems(MASs)with unknown control directions(UCDs),and illustrate a new kind of Nussbaum-type function based control algorithms.It is proven that if the time-varying net works are cut-balance,the convergence of nonlinear MASs with nonidentical UCDs is achieved using the presented algorithms.A critical feature of this application is that the designed algorithms can deal with nonidentical UCDs by employing conventional Nussbaum-type functions.Finally,one simulation example is given to illustrate the effectiveness of the presented algorithms.