Adaptive fuzzy fault-tolerant attitude control of spacecraft

This paper investigates the attitude control of spacecraft in the presence of unknown mass moment of inertia matrix, external disturbances, actuator failures, and control input constraints. A robust adaptive controller is proposed with the utilization of fuzzy logic and backstepping techniques. The unit quaternion is employed to describe the attitude of spacecraft for global representation without singularities. The system uncertainty is estimated by introducing a fuzzy logic system. The adaptive mechanism has only two parameters to be adapted on-line because the adaptive law of the proposed controller is derived from the norm of the weight matrix. The stability of the closed-loop system is guaranteed by Lyapunov direct approach. Results of numerical simulations state that the proposed controller is successful in achieving high attitude performance in the presence of parametric uncertainties, external disturbances, actuator failures, and control input constraints.     

考虑执行器动态和输入受限的近空间飞行器鲁棒可重构跟踪控制

针对多变量、不稳定的近空间飞行器姿态系统,在系统存在参数不确定和外部干扰的情况下,并考虑执行器动态和输入受限,提出一种鲁棒可重构跟踪控制策略.首先,利用二阶滑模干扰观测器分别重构姿态、角速率回路的复合干扰;其次,采用鲁棒二阶滑模积分滤波器的反推(backstepping)方法避免了控制器设计中微分项膨胀问题,利用鲁棒项抵消重构误差对系统的影响,以实现姿态控制器设计.然后,在考虑执行器动态、输入受限及舵面卡死故障下,给出一种线性矩阵不等式的在线优化舵面分配算法,以实现飞行器的姿态角渐近跟踪期望的制导指令.最后,仿真结果表明所提出的方法具有良好的跟踪控制性能.     

Adaptive backstepping‐based control design for uncertain nonlinear active suspension system with input delay

This paper addresses the control problem of adaptive backstepping control for a class of nonlinear active suspension systems considering the model uncertainties and actuator input delays and presents a novel adaptive backstepping‐based controller design method. Based on the established nonlinear active suspension model, a projector operator–based adaptive control law is first developed to estimate the uncertain sprung‐mass online, and then the desirable controller design and stability analysis are conducted by combining backstepping technique and Lyapunov stability theory, which can not only deal with the actuator input delay but also achieve better dynamics performances and safety constraints requirements of the closed‐loop control system. Furthermore, the relationship between the input delay and the state variables of this vehicle suspension system is derived to present a simple and effective method of calculating the critical input delay. Finally, a numerical simulation investigation is provided to illustrate the effectiveness of the proposed controller.     

执行机构部分失效的挠性航天器多界依赖容错控制

针对挠性航天器在轨运行时受到的外部干扰,输入时滞以及执行机构部分失效问题,本文提出了一种基于不确定参数的鲁棒H_∞容错控制方法.首先,将执行机构部分失效容错控制问题转化为不确定参数的鲁棒控制问题.然后,设计了一个新型的多界依赖状态反馈鲁棒H_∞控制算法.此算法不仅依赖时滞积分不等式分割参数和时滞界信息,还依赖部分失效因子.因此,本文设计的控制器能同时实现对输入时滞的敏感,对部分失效故障的容错及对外部干扰的抑制.最后,通过一系列的仿真验证本文方法的有效性.     

Reaction wheel fault‐tolerant finite‐time control for spacecraft attitude tracking without unwinding

This article proposes fault‐tolerant finite‐time attitude tracking control of a rigid spacecraft actuated by four reaction wheels without unwinding problem in the presence of external disturbances, uncertain inertia parameter, and actuator faults. First, a novel antiunwinding finite‐time attitude tracking control law is derived with a designed control signal which works within a known actuator‐magnitude constraint using a continuous nonsingular fast terminal sliding mode (NFTSM) concept. Second, a finite‐time disturbance observer (FTDO) is introduced to estimate a lumped disturbance due to external disturbances, uncertain inertia parameter, actuator faults, and input saturation. Third, a composite controller is developed which consists of a feedback control based on the continuous NFTSM method and compensation term based on the FTDO. The global finite‐time stability is proved using Lyapunov stability theory. Moreover, the singularity and unwinding phenomenon are avoided. Simulation results are conducted under actuator constraints in the presence of external disturbances, inertia uncertainty, and actuator faults and results are illustrated to show the effectiveness of the proposed method. In addition, to show the superiority of the proposed control method over the recently reported control methods, comparative analysis is also presented.     

考虑输入饱和的近空间飞行器姿态容错控制

针对近空间飞行器姿态控制中出现的执行器故障,输入饱和与外部干扰等问题,设计了一种基于二阶滑模干扰观测器和辅助系统的鲁棒容错跟踪控制方法.首先,将系统不确定,外部扰动和执行器故障作为复合干扰,设计super-twisting二阶滑模干扰观测器对其进行估计.然后为解决输入饱和问题构造了辅助分析系统,并借助backstepping方法,设计姿态容错跟踪控制器.利用Lyapunov方法,严格证明了所有闭环系统信号的收敛性.最后将所设计的控制方法应用于近空间飞行器姿态控制中,仿真结果验证了该控制方法的有效性.     

Guidance Laws With Input Constraints and Actuator Failures

A novel three‐dimensional fault‐tolerant control guidance law is proposed for interception of maneuvering targets in the presence of external disturbances, actuator failures, and control input constraints. The input‐to‐state stability (ISS) method is introduced to design the fault‐tolerant control guidance law to guarantee robust tracking of a maneuvering target. Then, a saturated fault‐tolerant control guidance law is constructed using a modified saturation function to ensure the resulting control signal will never incur input constraints, and the convergence to a small neighborhood of origin is ensured in theory. Simulation results show that the presented approach is effective in achieving a successful interception against target maneuvers, external disturbances, actuator failures, and control input constraints.     

Robust‐decentralized tracking control for a class of uncertain MIMO nonlinear systems with time‐varying delays

A new control design method based on signal compensation is proposed for a class of uncertain multi‐input multi‐output (MIMO) nonlinear systems in block‐triangular form with nonlinear uncertainties, unknown virtual control coefficients, strongly coupled interconnections, time‐varying delays, and external disturbances. By this method, the controller design is performed in a backstepping manner. At each step of backstepping procedure, a nominal virtual controller is first designed to get desired output tracking for the nominal disturbance‐free subsystem, and then a robust virtual compensator is designed to restrain the effect of the uncertainties, delays involved in the subsystem, and the couplings among the subsystems. The designed controller is linear and time‐invariant, so the explosion of complexity in the control law is avoid. It is proved that robust stability and robust practical tracking property of the closed‐loop system can be ensured, and the tracking errors can be made as small as desired. Copyright © 2013 John Wiley & Sons, Ltd.     

Robust Tracking Control Of The Variable Stiffness Actuator Based On The Lever Mechanism

This paper is concerned with the design of a robust adaptive tracking control scheme for a class of variable stiffness actuators (VSAs) based on the lever mechanisms. For these VSAs based on the lever mechanisms, the AwAS‐II developed at Italian Institute of Technology (IIT) is chosen as the study object, and it is an enhanced version of the original realization AwAS (actuator with adjustable stiffness). Firstly, for the dynamic model of the AwAS‐II system in the presence of parametric uncertainties, unknown bounded friction torques, unknown bounded external disturbance and input saturation constraints, by using the coordinate transformations and the static state feedback linearization, the state space model of the AwAS‐II system with composite disturbances and input saturation constraints is transformed into an uncertain multiple‐input multiple‐output (MIMO) linear system with lumped disturbances and input saturation constraints. Subsequently, a combination of the feedback linearization, disturbance observer, sliding mode control and adaptive input saturation compensation law is adopted for the design of the robust tracking controller that simultaneously regulates the position and stiffness of the AwAS‐II system. Under the proposed controller, the semi‐global uniformly ultimately bounded stability of the closed‐loop system has been proved via Lyapunov stability analysis. Simulation results illustrate the effectiveness and the robustness of the proposed robust adaptive tracking control scheme.     

考虑测量不确定和输入饱和的充液航天器自适应鲁棒控制

本文研究了三轴稳定充液航天器控制系统中同时存在测量不确定,外部未知干扰,参数不确定和控制输入饱和的鲁棒自适应姿态机动控制问题.建模过程中,将晃动液体燃料等效为粘性球摆模型,采用动量矩守恒定律推导出充液航天器的耦合动力学方程.提出了一种将反步控制方法结合非线性干扰观测器和指令滤波器的鲁棒饱和输出反馈复合控制策略,该控制策略不仅能继承反步控制方法的优点,而且通过引入非线性干扰观测器实现对未知外部干扰,参数不确定以及测量不确定的补偿,还能利用指令滤波器处理控制力矩输入饱和的不利影响.基于Lyapunov稳定性分析方法证明了系统状态变量的渐进稳定性.仿真结果验证了提出控制方法的有效性和鲁棒性.