再入飞行器带有干扰观测器的有限时间控制

针对模型参数不确定及外界干扰影响下的再入飞行器的姿态控制问题,设计基于干扰观测器的有限时间控制策略.首先建立面向控制模型,并通过多时间尺度原理将面向控制模型分为内、外两环;其次,设计干扰观测器实时观测面向控制模型中的参数不确定及外界干扰,解决滑模控制因参数过大而导致的抖振问题,基于观测值,设计终端滑模控制器,在此基础上,基于Lyapunov理论对控制系统的稳定性进行分析;最后,基于六自由度再入模型,验证所设计的有限时间姿态控制策略的有效性.     

基于拟连续高阶滑模的高超声速飞行器再入姿态控制

考虑模型参数不确定和外界干扰对再入制导控制性能的影响,基于拟连续高阶滑模控制策略对高超声速飞行器的再入制导控制问题进行了研究.首先,给出再入制导指令的设计过程.其次,基于再入飞行特性对模型进行简化,获得面向控制的姿态模型,在此基础上,通过引入新的控制变量,设计解耦滑模面,实现姿态间的解耦.再次,为了削弱控制抖振,通过引入虚拟控制,对系统进行增广,基于齐次性理论设计拟连续三阶滑模再入姿态控制器,确保系统在有限时间实现对制导指令的稳定跟踪.最后,六自由度再入飞行器的制导控制一体化仿真结果表明,本研究给出的控制策略在不影响系统鲁棒性的同时,能够实现对标称轨迹和再入姿态的综合控制.     

基于Terminal 滑模的高超声速飞行器姿态控制

针对高超声速飞行器六自由度再入模型,考虑模型参数不确定和外界干扰对再入姿态控制的影响,基于Terminal滑模对再入过程中姿态角的跟踪控制问题进行研究.为了减少外界高频噪声对系统性能的影响,首先,利用多时间尺度技术将姿态模型划分为双环结构;然后,分别针对各环路设计Terminal滑模控制器,并通过Lyapunov理论和奇异摄动理论对系统的稳定性进行证明.仿真结果表明,对于六自由度再入模型,该控制方法能够很好地跟踪再入制导指令.     

基于干扰观测器的航天器非奇异终端二阶滑模控制

为了消除干扰力矩和结构不确定性对卫星姿态控制性能的影响,本文提出了一种基于新型干扰观测器的非奇异终端二阶滑模控制方法.首先,文章设计了一种基于跟踪微分器的干扰观测器,来对卫星系统中的不确定项进行估计,利用估计值进行补偿,并保证估计误差在有限时间内收敛.在此基础上,文章设计一个非奇异终端滑模面,当系统到达滑模面时,姿态误差可以在有限时间内收敛,并利用二阶滑模趋近律设计控制器,保证系统在有限时间到达滑模面.在干扰观测器误差未完全收敛时,滑模控制器可以对存在的扰动进一步抑制,实现姿态跟踪系统的有限时间稳定,并通过李雅普诺夫方法严格证明了其稳定性.最后,仿真结果表明,干扰估计值误差可以在有限时间内收敛,证明了该控制方法对存在的干扰是具有较好的鲁棒性.     

基于super-twisting算法的多航天器姿态有限时间分布式协同控制

针对受外界干扰和执行器故障影响的多航天器姿态协同控制问题,本文设计了一种基于干扰观测器的分布式协同supper-twisting滑模控制器.首先,将各航天器的外界干扰和执行器故障看作一个集总干扰,设计自适应滑模干扰观测器对其进行估计.其次,将supper-twisting算法和积分滑模面相结合,设计一种基于多航天器姿态一致性误差的分布式协同控制器,并由Lyapunov稳定性理论证明了所设计的多航天器姿态可以在有限时间内收敛到平衡点附近的邻域内.最后的仿真研究及比较结果表明,所设计的控制器可以加快系统的收敛速度,并提高系统的控制精度.     

四旋翼无人机抗干扰轨迹跟踪控制

针对四旋翼无人机轨迹跟踪过程中存在的参数不确定与外界干扰问题,设计一种双闭环自适应控制策略.为了降低控制器设计复杂度,根据四旋翼无人机系统的欠驱动特性将系统分成姿态内环和位置外环.在扰动观测器的基础上,利用积分型反步控制算法完成无人机位置信息在外界干扰下的稳定跟踪控制.在扰动观测器的基础上,利用自适应滑模控制算法完成无人机姿态信息在参数不确定和外界干扰作用下的稳定跟踪控制.与传统PID控制和滑模控制进行仿真对比,验证所提出控制策略的优越性.     

RLV抗扰动非线性最优控制器设计

可重复使用运载器(RLV)再入面临严重的扰动影响,对此设计一种抗扰动非线性最优控制器(ADNOC)。首先,基于时标分离原理设计快、慢双回路控制结构;其次,将角速率动态变换处理成线性形式,通过依赖状态的黎卡提方程(SDRE)优化方法获得最优控制指令;然后,设计非线性扰动观测器用于估计外界干扰,并在非线性最优控制律中进行干扰补偿。仿真实验结果表明,所设计的控制器能良好地完成姿态跟踪控制,抑制扰动对姿态控制的影响,实现RLV的最优控制性能。     

输入饱和的充液航天器抗干扰有限时间滑模控制

研究三轴稳定充液航天器姿态控制过程中存在外部未知干扰、参数不确定和输入饱和的问题,提出一种抗干扰有限时间滑模控制的姿态机动控制方法.将部分充液贮箱内液体燃料晃动等效为球摆模型,采用动量矩守恒定律推导出充液航天器耦合动力学方程.首先,设计有限时间积分滑模干扰观测器,保证控制系统中集总干扰可以在有限时间内被估计;然后,基于所设计的干扰观测器,提出一种抗干扰有限时间快速终端滑模控制策略,并且证明在该控制律的作用下闭环系统的状态是有限时间稳定的,而且收敛到指定的快速终端滑模面上.此外,通过引入辅助变量补偿控制输入超调量,克服输入饱和的约束.仿真结果验证了该控制策略的有效性和鲁棒性.     

带状态观测器的船舶路径跟踪预测滑模控制

为解决具有速度不易测量、模型不确定与外界干扰的欠驱动船舶路径跟踪问题,提出一种结合线性扩张状态观测器(LESO)的滑模控制算法.首先对船舶路径进行预测,据此预测值和参考路径值计算路径未来误差,并基于Backstepping算法设计参考艏向角.其次,采用双曲正切函数设计滑模控制器,对艏向进行控制.引入LESO对外界干扰和不确定参数进行逼近,以提高控制器的鲁棒性.并利用非线性观测器和LESO对船舶纵向速度、横向速度以及转艏角速度进行估计,避免速度不易测量问题.最终的仿真结果验证了所设计控制器的有效性.     

基于非线性干扰观测器的高超声速飞行器滑模反演控制

针对高超声速飞行器非线性、强耦合和参数不确定弹性体模型,提出了一种基于非线性干扰观测器的滑模反演控制方法.将飞行器曲线拟合模型分解为速度子系统和高度相关子系统并表示为严格反馈形式,分别采用滑模和反演方法设计实际控制量与虚拟控制量.采用1阶低通滤波器获取虚拟控制量的导数,解决了传统反演控制方法"微分项膨胀"问题.基于改进滑模微分器设计了一种新型非线性干扰观测器,以此对模型不确定项进行估计和补偿.仿真结果表明,该控制器对模型不确定性和气动弹性影响具有鲁棒性,且实现了对速度和高度参考输入的稳定跟踪.     

Multivariable supertwisting fixed‐time approach for RLV re‐entry attitude control

The attitude control problem of reusable launch vehicles (RLVs) is investigated based on multivariable supertwisting fixed‐time comprehensive control strategy. A novel multivariable supertwisting fixed‐time approach, which can guarantee that the states converge to zero within a fixed time, is proposed. According to the multiple time scale principle, the RLV attitude control system is divided into attitude angle subsystem and attitude angle rate subsystem. Based on multivariable supertwisting fixed‐time approach, comprehensive design of fixed‐time disturbance observer and controller is proposed to ensure that the attitude angle tracking error converges to zero within a fixed time. The features of the proposed control scheme contain that the settling time is independent of initial conditions and it has the better property of chattering reduction. Finally, the efficiency of the proposed method is verified through numerical simulation.     

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.     

基于有限时间扰动观测器的四旋翼编队控制

针对复杂飞行环境下的多四旋翼飞行器系统,提出一种基于有限时间扩张状态观测器的主从编队控制策略(FTESO-LFFC).对于领航者子系统,提出一种积分滑模控制(ISM)策略,通过引入的积分项,消除了传统滑模控制中的趋近阶段,提高了系统的鲁棒性.对于跟随者子系统,提出一种非奇异终端滑模控制(N TS M)策略,该方法在解决...     

Finite‐time geometric control for underactuated aerial manipulators with unknown disturbances

In this article, the finite‐time geometric control for underactuated aerial manipulators is investigated. The dynamics of the aerial manipulator with unknown disturbances is analyzed first. The dynamics of the system is decomposed into the locked subsystem and shape subsystem. The finite‐time controller for the aerial manipulator is then designed based on the analyzed dynamics. In the controller, the attitude tracking error of the aircraft base is expressed from the rotation matrix, which makes the controller continuous and almost globally stable on SO(3). A continuous adaptive term is added in the controller to compensate for the unknown disturbances. Finite‐time filters are designed to ensure the smoothness of the commands on each loop. The convergence of the entire controlled system is strictly proved using Lyapunov theory and the definition of finite‐time stability. The results show that the tracking error and the disturbance bound estimation error of the entire system are finite‐time bounded near origin. Finally, comparative simulation results are presented to show the performance of the proposed controller.     

Adaptive finite‐time stabilization of nonlinearly parameterized systems subject to mismatching disturbances

This paper gives a first try to the finite‐time control for nonlinear systems with unknown parametric uncertainty and external disturbances. The serious uncertainties generated by unknown parameters are compensated by skillfully using an adaptive control technique. Exact knowledge of the upper bounds of the disturbances is removed by employing a disturbance observer–based control method. Then, based on the disturbance observer–based control, backstepping technique, finite‐time adaptive control, and Lyapunov stability theory, a composite adaptive state‐feedback controller is strictly designed and analyzed, which guarantees the closed‐loop system to be practically finite‐time stable. Finally, both the practical and numerical examples are presented and compared to demonstrate the effectiveness of the proposed scheme.     

具有时变扰动的四旋翼无人机有限时间预定性能控制

针对外界扰动、模型不确定性以及输出误差约束情况下的四旋翼无人机轨迹跟踪问题,提出有限时间预定性能控制策略.首先,将无人机动力学模型解耦为姿态子系统和位置子系统;其次,引入误差转换函数和性能约束函数,通过合理设计快速终端滑模面,实现转换误差有限时间收敛,从而实现原系统输出误差约束控制;进一步,通过稳定性分析可以得出所设计的控制器能够保证系统有限时间稳定,并且具有良好的暂稳态性能;最后,通过实例仿真验证所设计方法的有效性。     

基于学习观测器的航天器指定时间跟踪控制

针对一类含有外部扰动和执行器故障的刚体航天器姿态控制系统,提出一种基于自适应学习观测器的指定时间容错控制器的设计方案.首先,系统性地给出一种改进型自适应学习观测器设计方案,基于自适应学习观测器框架,设计航天器姿态系统的学习观测器实现对系统的综合扰动值估计;然后,利用综合扰动的估计信息和滑模控制理论设计指定时间容错跟踪控制器,使得系统的姿态角能够在指定时间跟踪指令信号,系统的收敛时间可通过容错控制器的参数预先设置,且与系统的初始状态值无关;接着,基于Lyapunov稳定性理论验证含有故障的姿态控制系统能够在指定时间内稳定;最后,通过数值仿真,与已有的观测器和有限时间控制方案进行对比,表明所提出方案的有效性和可行性.     

Robust control of nonlinear semi‐strict feedback systems using finite‐time disturbance observers

The output tracking controller design problem is dealt with for a class of nonlinear semi‐strict feedback systems in the presence of mismatched nonlinear uncertainties, external disturbances, and uncertain nonlinear virtual control coefficients of the subsystems. The controller is designed in a backstepping manner, and to avoid the shortcoming of ‘explosion of terms’, the dynamic surface control technique that employs a group of first‐order low‐pass filters is adopted. At each step of the virtual controller design, a robust feedback controller employing some effective nonlinear damping terms is designed to guarantee input‐to‐state practical stable property of the corresponding subsystem, so that the system states remain in the feasible domain. The virtual controller is enhanced by a finite‐time disturbance observer that estimates the disturbance term in a finite‐time. The properties of the composite control system are analyzed theoretically. Furthermore, by exploiting the cascaded structure of the control system, a simplified robust controller is proposed where only the first subsystem employs a disturbance observer. The performance of the proposed methods is confirmed by numerical examples. Copyright © 2017 John Wiley & Sons, Ltd.