Nonsingular terminal sliding mode based finite-time control for spacecraft attitude tracking

This paper studies finite-time attitude tracking control problem of a rigid spacecraft system with external disturbances and inertia uncertainties. Firstly, a new finite-time attitude tracking control law is designed using nonsingular terminal sliding mode concepts. In the absence and presence of external disturbances and inertia uncertainties, this controller can drive the attitude and angular velocity tracking errors to reach zero in finite time. Secondly, a finite-time disturbance observer is introduced to estimate the disturbance, and a composite controller is developed which consists of a feedback control based on nonsingular terminal sliding mode method and compensation term based on finite-time disturbance observer. Finite-time convergence of attitude tracking errors and the stability of the closed-loop system is ensured by the Lyapunov approach. Numerical simulations on attitude control of spacecraft are also given to demonstrate the performance of the proposed controllers.     

交会对接模拟系统姿态位置耦合有限时间控制

针对航天器交会对接模拟系统的姿态同步和位置跟踪控制问题,在存在外界扰动和系统不确定性的情况下,基于改进的快速非奇异终端滑模面和改进的自适应律,采用双闭环控制结构分别设计内环和外环有限时间姿态位置耦合控制器.所提出的自适应律不仅能有效地抑制扰动和不确定性且能保证控制器是连续的.李雅普诺夫理论推导和仿真结果表明,所提出的控制方法能保证系统内环和外环跟踪误差的有限时间稳定性和准确收敛性.     

航天器自适应快速非奇异终端滑模容错控制

针对存在外部干扰、转动惯量矩阵不确定以及执行器故障的航天器姿态跟踪控制问题,本文提出了基于自适应快速非奇异终端滑模的有限时间收敛故障容错控制方案.通过引入能够避免奇异点,且具有有限时间收敛特性的快速非奇异终端滑模面,设计了满足多约束条件有限时间收敛的姿态跟踪容错控制律,利用参数自适应方法使控制器不依赖转动惯量和外部干扰的上界信息.Lyapunov稳定性分析表明:在存在外部干扰、转动惯量矩阵不确定以及执行器故障等约束条件下,本文设计的控制律能够保证闭环系统的快速收敛性,而且对执行器故障具有良好的容错性能.数值仿真校验了该控制律在姿态跟踪控制中的优良性能.     

Terminal sliding mode fault-tolerant control for aviation redundant hydraulic actuation system based on robust fault reconstruction

This paper investigates the fault-tolerant control problem for a dual-redundant hydraulic actuation system on active/active (A/A) mode subject to servovalve leakage and disturbances. The change in system dynamics caused by servovalve leakage is modeled as an additive time-varying fault. Then, an enhanced iterative learning observer with improved robustness against abrupt unknown input is designed for fault reconstruction. In view of the high relative degree of the plant, an auxiliary variable is adopted to facilitate the controller design. Combined with the fault reconstruction results, an adaptive continuous nonsingular fast terminal sliding mode (NFTSM) fault-tolerant controller is developed, in which an NFTSM manifold is constructed based on the auxiliary variable to achieve fast convergence of trajectory tracking errors. An adaptive continuous reaching law with less chattering is designed to compensate for the influence of the lumped disturbance. Lyapunov stability analysis demonstrates that this method can ensure finite-time convergence of sliding variable and can guarantee the trajectory tracking errors converge to the neighborhood of the origin exponentially. Finally, the effectiveness of the proposed method is verified through a comparative simulation study.     

交会对接模拟系统姿态跟踪有限时间抗干扰控制

针对交会对接模拟系统的姿态同步问题,在存在扰动和系统不确定性的情况下,利用改进的快速非奇异终端滑模面和改进的自适应律设计两个有限时间抗干扰控制器.改进的自适应律保证了两个控制器的连续性和对干扰的鲁棒性,且第2个控制器能解决边界层理论存在的边界层内有限时间稳定性丢失的问题.李雅普诺夫理论推导和仿真结果表明,提出的两个控制器能保证系统的有限时间稳定性,系统能快速收敛到平衡点.     

基于扩张状态观测器的四旋翼无人机快速非奇异终端滑模轨迹跟踪控制

针对受多源干扰影响的四旋翼无人机系统的轨迹跟踪控制问题进行研究,充分考虑位置回路和姿态回路动态特性,提出一种全回路复合快速非奇异终端滑模轨迹跟踪控制方案.首先,通过变换将轨迹跟踪问题转化为位置回路和姿态回路的指令跟踪控制问题;然后,将各通道之间的耦合以及多源干扰影响视作集总干扰,并基于扩张状态观测器对其进行估计;接着,基于干扰估计信息和快速非奇异终端滑模控制算法,分别在位置回路和姿态回路构造复合快速非奇异终端滑模控制器;最后,基于位置回路和姿态回路虚拟控制量解得无人机真实控制量旋翼转速.仿真结果表明,所提出控制方案显著提升了四旋翼无人机轨迹跟踪的响应速度和抗干扰性能.     

Robust Finite-time Attitude Tracking Control of Rigid Spacecraft Under Actuator Saturation

This paper investigates the robust finite-time attitude tracking control problem for rigid spacecraft considering the modeling uncertainty, external disturbance and actuator saturation. An auxiliary system is proposed to directly compensate for the saturated control input. First, the basic controller is formulated based on the fast nonsingular terminal sliding mode surface (FNTSMS), the fast-TSM-type reaching law and the auxiliary system in the presence of upper bounded external disturbance. Then, when facing system uncertainty which consists of both modeling uncertainty and external disturbance and has upper bounded first derivative, the extended state observer (ESO) is associated with the first controller to improve the robustness of control system. Furthermore, to handle more general system uncertainty which is upper bounded by a polynomial function of the closed-loop system states, a continuous adaptive controller is designed to compensate for the total system uncertainty on line. The proposed controllers are able to deal with system uncertainty, input singularity and actuator saturation, while simultaneously providing fast finite-time convergence speed for the control system. And the problems of complex parameters selection process and repeated differentiations of nonlinear functions can be avoided. Rigorous stability analyses are given via the Lyapunov stability theory and digital simulations are conducted to illustrate the effectiveness of the proposed controllers.     

基于自组织小波小脑模型关节控制器的不确定非线性系统鲁棒自适应终端滑模控制

针对一类不确定非线性系统的跟踪控制问题,在考虑建模误差、参数不确定和外部干扰情况下,以良好的跟踪性能及强鲁棒性为目标,提出基于自组织小脑模型(self-organizing wavelet cerebellar model articulation controller,SOWCMAC)的鲁棒自适应积分末端(terminal)滑模控制策略.首先,将小脑模型、自组织神经网络和小波函数各自优势相结合,给出一种SOWCMAC,以保证干扰估计方法具有快速学习能力和更好的泛化能力.其次,设计两种改进的terminal滑模面构造方法,并分别给出各自的收敛时间.然后,基于SOWCMAC和改进的积分terminal滑模面,给出不确定非线性系统鲁棒自适应非奇异terminal控制器的设计过程,其中通过构造自适应鲁棒项抑制干扰估计误差对系统跟踪性能的影响,并利用Lyapunov理论证明闭环系统的稳定性.最后,将该方法应用于近空间飞行器姿态的控制仿真实验,结果表明所提出方法有效性.     

四旋翼无人机姿态系统复合连续快速非奇异终端滑模控制EI北大核心CSCD

本文针对受多源干扰影响的四旋翼无人机姿态系统,基于复合连续快速非奇异终端滑模算法,研究了姿态指令变化率未知情况下的连续有限时间姿态跟踪控制问题.首先,基于四旋翼无人机姿态回路动力学模型,通过引入虚拟控制量实现姿态跟踪误差动态的三通道解耦;其次,分别针对各通道跟踪误差动态设计高阶滑模观测器,实现跟踪误差变化率和集总干扰的有限时间估计;最后,结合姿态跟踪误差变化率的估计信息,构建动态快速非奇异终端滑模面,并在控制设计中用指数幂函数代替符号函数以保证控制量连续.并且基于Lyapunov分析方法给出了姿态跟踪误差有限时间收敛的严格证明,仿真结果验证了所提方法的有效性.     

Global finite-time attitude consensus tracking control for a group of rigid spacecraft

The problem of finite-time attitude consensus for multiple rigid spacecraft with a leader–follower architecture is investigated in this paper. To achieve the finite-time attitude consensus, at the first step, a distributed finite-time convergent observer is proposed for each follower to estimate the leader's attitude in a finite time. Then based on the terminal sliding mode control method, a new finite-time attitude tracking controller is designed such that the leader's attitude can be tracked in a finite time. Finally, a finite-time observer-based distributed control strategy is proposed. It is shown that the attitude consensus can be achieved in a finite time under the proposed controller. Simulation results are given to show the effectiveness of the proposed method.     

智能车辆队列横纵向有限时间滑模控制

针对智能车辆队列横纵向控制及误差快速收敛问题,本文提出一种分布式横纵向有限时间滑模控制策略.首先,考虑跟踪误差的连锁反应及横纵向耦合效应,利用投影变换建立车辆队列横纵向误差模型,提出一种车辆队列横纵向控制框架.而后,针对误差快速收敛问题,设计非奇异积分终端滑模面(NITSM)与自适应幂次积分趋近律(APIRL),通过构造Lyapunov函数分析系统的有限时间稳定性与队列稳定性.最后,基于Trucksim/Simulink联合仿真以及实车实验进一步验证了本文方法的有效性.结果表明,本文所提方法能保证队列稳定性,并实现误差快速收敛,规避跟踪误差的连锁反应及车辆横向运动对纵向车间距误差的影响.     

基于扰动观测器补偿的机械臂非奇异快速终端滑模控制

针对机械臂系统在实际应用中存在的建模误差及未知扰动问题, 设计了一种基于扰动观测器的改进型非 奇异快速终端滑模控制策略. 通过扰动观测器准确估计系统存在的总扰动, 并设计恰当的非线性增益函数使扰动观 测误差指数收敛, 实现了对控制器的前馈补偿. 考虑到终端滑模存在的奇异性问题, 结合扰动观测器设计了非奇异 快速终端滑模控制器, 在保证跟踪误差有限时间收敛的同时抑制了滑模控制固有的抖振现象. 同时在控制器设计过 程中, 用fal函数代替sig函数有利于削弱滑模控制抖振, 提高系统稳定性及跟踪精度. 最后, 利用MATLAB软件进行 实验仿真, 验证了所设计控制器的有效性.     

Barrier function based finite-time tracking control for a class of uncertain nonlinear systems with input saturation

In this article, a novel robust finite-time tracking control scheme is proposed for a class of uncertain nonlinear systems subject to the model uncertainty, external disturbance, and input saturation. A barrier function based disturbance observer (BFDO) with finite-time convergence performance is developed to estimate the non-smooth nonlinear compound disturbance, which includes the uncertainty, disturbance of system and input saturation. In addition, an adaptive continuous nonsingular terminal sliding mode controller, based on the barrier function and the estimate of the BFDO is developed. The Lyapunov stability and finite-time convergence of the proposed control scheme are proved. The effectiveness and performance advantage of the proposed control scheme is demonstrated by numerical simulations and comparison with existing works.     

Adaptive attitude tracking control for rigid spacecraft with finite-time convergence

In this paper, the finite-time attitude tracking control problem for rigid spacecraft with external disturbances and inertia uncertainties is addressed. First, a novel fast nonsingular terminal sliding mode surface (FNTSMS) without any constraint is designed, which not only avoids the singularity problem, but also contains the advantages of the nonsingular terminal sliding mode (NTSM) and the conventional sliding-mode together. Second, the proposed FNTSM control laws (FNTSMCLs) by employing FNTSMS associated with adaptation provide finite-time convergence, robustness, faster, higher control precision. The proposed FNTSMCLs in light of novel adaptive control architecture are continuous. Thus, they are chattering-free. Finally, simulation results are presented to illustrate effectiveness of the control strategies. In addition, digital simulations of satellite Hubble Space Telescope (HST) are presented to verify the practical feasibility of the reorientation/ slew maneuvers mission.     

Robust adaptive fixed‐time tracking control of 6‐DOF spacecraft fly‐around mission for noncooperative target

The fixed‐time relative position tracking and attitude synchronization control problem of a spacecraft fly‐around mission for a noncooperative target in the presence of parameter uncertainties and external disturbances is investigated. Firstly, a novel and coupled relative position and attitude motion model for a noncooperative fly‐around mission is established. Subsequently, a novel nonsingular fast terminal sliding mode (NFTSM) surface is developed, and the explicit estimation of the convergence time independent of initial states is provided. Fair and systematic comparisons among several typical terminal sliding modes show that the designed NFTSM has faster convergence performance than the fast terminal sliding mode. Then, a robust integrated adaptive fixed‐time NFTSM control law with no precise knowledge of the mass and inertia matrix and disturbances by combining the nonsingular terminal sliding mode technique with an adaptive methodology is proposed, which can eliminate the chattering phenomenon and guarantee that the relative position and attitude tracking errors can converge into the small regions containing the origin in fixed time. Finally, numerical simulations are performed to demonstrate the effectiveness of the proposed control schemes.     

Adaptive Terminal Sliding Mode Control for Motion Tracking of a Micropositioning System

This paper presents the design of a novel adaptive terminal sliding mode controller (ATSMC) and its application to motion tracking control of a piezoelectric‐driven micropositioning system. A nonsingular terminal sliding surface is used to achieve fast and finite‐time convergence for the trajectory tracking, and also to avoid the singularity phenomenon in traditional terminal sliding mode design. An adaptive gain law is developed to update the gain of the proposed controller and to provide stable and chattering‐free control action. The stability of the control system has been demonstrated in the sense of Lyapunov. The ATSMC scheme is established based on the output feedback only, which does not require a state observer and facilitates an easy implementation. The proposed controller is implemented on a field‐programmable gate array (FPGA) platform. Comparison study with three conventional controllers has been conducted. Experimental results show the feasibility and effectiveness of the proposed control strategy.     

基于快速终端滑模面的两旋翼飞行器有限时间姿态控制

针对带有模型不确定和外部干扰的两旋翼飞行器,提出一种基于快速终端滑模面的有限时间自适应姿态控制方法,保证两旋翼飞行器对期望姿态角度的有限时间跟踪。构造快速终端滑模面,并设计分段连续函数避免滑模变量求导产生的奇异值问题。在此基础上,设计有限时间姿态控制器,并设计系统不确定上界的自适应更新律,抵消模型不确定性和外部干扰的影响。经李雅普诺夫方法证明滑模变量、姿态角误差、角速度误差等闭环信号最终一致有界,且有限时间收敛至平衡点邻域,收敛时间与系统状态变量初始值有关。最后,采用了矩形波和 曲线作为设定信号,设计相应的跟踪实验,并在两旋翼飞行器平台上验证所提控制方法的有效性,且分析双曲正切函数对系统控制输入影响,经实验测试其可减少系统颤振现象。     

A new finite-time cooperative control algorithm for uncertain multi-agent systems

In this paper, the problem of fixed-time consensus tracking control is investigated for multi-agent networks with input uncertain dynamics under the undirected graph. First, a nonsingular terminal sliding mode manifold is proposed, with which the convergence time is globally bounded irrelevant to initial states. Then, with the aid of the observer method and sliding mode technique, the distributed nonsingular controller is designed for the underlying system to ensure that the consensus tracking errors go into sliding mode manifold and converge to origin within a desired time. Finally, examples are presented to verify the validity of the new control strategy.     

四旋翼无人机安全轨迹跟踪控制

针对存在安全约束的四旋翼无人机,为了保证其能够快速稳定地跟踪给定轨迹,本文提出了一种基于双闭环思想及控制障碍函数求解二次规划问题的控制器设计框架.首先,考虑到无人机的模型不确定性及外界干扰问题,基于快速非奇异终端滑模面设计了双闭环标称控制器,能够实现有限时间快速收敛.进一步地,为了解决无人机遇到的状态、距离约束等安全控制问题,利用控制障碍函数,将带有约束的控制器设计问题转化成二次规划的求解问题.最后,对提出的控制策略进行了仿真,验证了控制器的快速性和鲁棒性,并实现了给定轨迹的安全跟踪.     

飞翼无人机复合连续非奇异终端滑模姿态跟踪容错控制

本文针对受多源干扰和舵面故障影响的飞翼无人机系统姿态跟踪控制问题进行研究, 提出了一种基于高阶滑模观测器的复合连续非奇异终端滑模主动抗干扰容错控制算法, 在实现姿态跟踪误差有限时间收敛的同时, 保证了控制量的连续. 并且针对控制力矩的具体实现问题, 结合飞翼无人机气动舵面冗余特性, 给出了基于加权伪逆算法的舵面分配方案, 该方案在满足舵面约束的情况下, 保证了舵面偏转角度的最优. 仿真结果表明, 所提控制方案显著提升了飞翼无人机姿态跟踪精度和跟踪误差的收敛速度, 并且保证了所有舵面满足偏角约束.