有限时间收敛的Terminal滑模控制设计

讨论了一类SISO非线性系统的滑模变结构控制有限时间收敛问题,提出一种新的Terminal滑动模态及相应控制的设计方法,可用于带有外部扰动的二阶非线性系统。研究结果表明,系统状态在滑模面上能以较快的速度达到平衡点,在滑模面上到达平衡点的时间均是有限的,并且与普通的Terminal滑模相比,在滑模面上能以更短的时间到达平衡点。仿真结果表明了所提方法的有效性。     

偏置动量轮控卫星姿态控制

研究了轮控的三轴稳定的偏置动量卫星姿态控制问题。卫星的俯仰回路采用偏置动量轮，滚动／偏航轴上各安装一个反作用飞轮来完成姿态控制。小姿态角下俯仰回路可以单独设计，利用测量的俯仰角来实现其姿态控制；滚动／偏航回路利用滚动信息，采用基于偏航观测器的滑模控制器设计。磁力矩器提供的磁矩与地磁场作用产生的力矩实现了飞轮的动量卸载。对卫星姿态控制系统进行的仿真研究结果表明，所设计的控制方案在飞轮输出力矩工作范围内，可使卫星达到很高的姿态控制精度。     

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。     

时变终端滑模自适应有限时间控制算法

为实现非线性系统输出对期望轨迹的有限时间内精确跟踪,提出一种有限时间鲁棒控制算法。通过设计一种无到达过程的时变终端滑模面,在保证有限时间收敛的基础上,消除了传统滑模控制中固有的稳态误差,实现系统输出对期望轨迹的精确跟踪。设计了自适应更新律补偿由参数摄动导致的系统扰动,增强系统对内部未知参数摄动的鲁棒性。对比仿真结果表明:时变终端滑模控制比线性滑模控制的轨迹跟踪时间快41. 5%;线性滑模控制器下的轨迹跟踪稳态误差为0. 005,时变滑模控制器使轨迹跟踪的稳态误差降为0,实现精确跟踪。     

Robust Adaptive Fractional‐Order Terminal Sliding Mode Control for Lower‐Limb Exoskeleton

This paper introduces a robust adaptive fractional‐order non‐singular fast terminal sliding mode control (RFO‐TSM) for a lower‐limb exoskeleton system subject to unknown external disturbances and uncertainties. The referred RFO‐TSM is developed in consideration of the advantages of fractional‐order and non‐singular fast terminal sliding mode control (FONTSM): fractional‐order is used to obtain good tracking performance, while the non‐singular fast TSM is employed to achieve fast finite‐time convergence, non‐singularity and reducing chattering phenomenon in control input. In particular, an adaptive scheme is formulated with FONTSM to deal with uncertain dynamics of exoskeleton under unknown external disturbances, which makes the system robust. Moreover, an asymptotical stability analysis of the closed‐loop system is validated by Lyapunov proposition, which guarantees the sliding condition. Lastly, the efficacy of the proposed method is verified through numerical simulations in comparison with advanced and classical methods.     

具有强鲁棒性的滑模变结构控制

针对一类高阶不确定非线性系统,基于指数型快速终端滑模的良好特性,提出了一种新的滑模变结构控制．系统状态变量能以较快的收敛速度在有限时间内到达各级滑模面的邻域,并最终收敛到平衡点附近很小的区域．使用李亚普诺夫稳定性理论证明了系统的渐近稳定性,并推导出各级邻域和系统不确定环节的数学关系．Matlab仿真验证了系统的强鲁棒性．     

广义系统的终端滑模变结构控制

研究广义系统的终端滑模控制问题,通过线性奇异变换将广义系统化为受限等价形式,在此基础上给出相应的终端滑模超曲面和终端滑模控制律．研究结果表明,系统状态变量能以较快的收敛速度在有限时间内进入滑模超曲面并最终到达平衡点。     

Synchronization and Tracking of Multi‐Spacecraft Formation Attitude Control Using Adaptive Sliding Mode

This paper presents the finite‐time attitude synchronization and tracking control method of undirected multi‐spacecraft formation with external disturbances. First, a modified adaptive nonsingular fast terminal sliding mode surface (ANFTSMS) is designed by introducing a user‐defined function, both of which avoid the singularity problem and continuous sliding surface, and, therefore, can freely adjust relative weighting between angular velocity error and attitude error adaptively, such that the controller can provide sufficient maneuvers and precision. This provides designers with a new technique to adjust and improve formation control performance. Second, by applying the ANFTSMS associated with adaptation, two proposed decentralized ANFTSM‐controllers provide finite‐time convergence, robustness to disturbance, and chattering free for continuous design. Finally, simulation results validate the proposed algorithms.     

不确定性多变量系统的变结构最终滑动模态控制方案

为了改善多变量变结构控制系统的瞬态性能，本文提出了一个变结构最终滑动模态控制方案。文中方案克服了由于多变量变结构控制中存在多个滑动模态，而带一的因采递阶控制方案导致控制结构复杂程序增加的缺点，有效地改善了系统进入最终滑动的动态品质，并对于参数摄动具有较强的鲁棒性。     

Attitude stabilization of rigid spacecraft with finite‐time convergence

The problem of attitude control for a spacecraft model which is nonlinear in dynamics with inertia uncertainty and external disturbance is investigated in this paper. Two sliding mode controllers are proposed to force the state variables of the closed‐loop system to converge to the origin in finite time. Specially, the second control design consists of the estimation of the uncertainty and disturbance by adaptive method and thus it achieves the decrease of undesired chattering effectively. Also, simulation results are presented to illustrate the effectiveness of the control strategies. Copyright © 2010 John Wiley & Sons, Ltd.     

防空导弹姿态控制系统终态滑模变结构设计

针对防空导弹垂直发射姿态调转时的快速性要求,研究了快速姿态调转的控制问题.首先基于一类多输入多输出高阶非线性系统的Teminal(终态)滑模变结构控制方法,对垂直发射防空导弹的滚动和俯仰、偏航通道所呈现的非线性、强耦合性进行了分析,并设计了一种新型滑模控制器.控制器设计方案消除了滑模控制的到达阶段,系统的初始状态始终保持在滑模面上,确保了系统的全局鲁棒性和稳定性,且能在有限且可控时间内使跟踪误差趋近于零.最后通过数字仿真验证了系统在不确定因素情况下具有强鲁棒性和适应性,可用于防空导弹短时间姿态调转控制.     

不确定非线性系统的自适应最终滑模控制──Backstepping方法(英)

对具有参数不确定与未知非线性的一类非线性系统，本文通过引入快慢两种切换线给出了一种自适应有限时间滑模控制机制．Backstepping方法被应用到设计中．此种控制机制保证了闭环系统的稳定性并使状态在有限时间内收敛到原点．仿真结果表明该控制机制的有效性．     

快速非奇异终端滑模在混沌系统中的应用

为解决传统线性滑模控制中的速度较慢和终端滑模的奇异性问题,提出一种快速非奇异终端滑模的控制策略,并将其应用于Lorenz混沌系统中。控制策略为当系统状态离平衡点较远时采用线性滑模,使其快速地到达滑模面;而一旦滑模到达所设计的滑模面时控制策略变为非奇异终端滑模,使其快速地收敛于平衡点。此策略将线性滑模和终端滑模的优点相结合,从而使整个系统的状态在全程都具有较快的收敛速度,此方法改善了传统的线性滑模只能渐近地趋近于平衡点的动态缺点;同时也改善了单独采用终端滑模时,离平衡点较远的状态到达时间较长的缺点;且有效地避免了奇异现象的发生。最后通过M atlab仿真,对Lorenz混沌系统进行仿真,验证了该方法的有效性。     

4‐Channel Sliding Mode Control of Teleoperation Systems with Disturbances

Sliding mode control can effectively account for the disturbances of a system. Among the different teleoperation architectures, 4‐channel architecture is the most successful for fulfilling transparency. In this paper, two sliding mode controllers are designed for nonlinear master and slave with external disturbances and are incorporated into a 4‐channel structure to achieve transparency. To this end, each of the controllers consists of a sliding mode position feedback law, a force feedback law, and two supplementary terms regarding gravity and contact force compensation. Stability and transparency of the overall system is studied via a Lyapunov function analysis. Simulations compared with the conventional adaptive control on teleoperation systems demonstrate the effectiveness of the proposed scheme.     

Spacecraft Anti‐Unwinding Attitude Control Using Second‐Order Sliding Mode

This paper presents an anti‐unwinding control method for the attitude stabilization of a rigid spacecraft. Quaternion has double stable equilibrium and this may cause unwinding problems in spacecraft attitude control if both the equilibria are not considered in control design. Here, the initial condition of scalar quaternion is included in sliding surface and an anti‐unwinding control method is formulated in second‐order sliding mode. The presented second‐order sliding mode controller can alleviate chattering and ensure a smooth control for actuator. Further, to eliminate the need of advance information about bounds of uncertainty and external disturbance, adaptive laws are applied to estimate the controller gains. The closed‐loop stability is proved using the Lyapunov stability theory. In conclusion, a simulation is conducted in the presence of inertia uncertainty and external disturbances and it is found that the presented control method is efficient to negate the effect of inertia uncertainty and external disturbances, alleviate chattering, eliminate unwinding, and ensure high accuracy and steady state precision.     

Adaptive Nonsingular Terminal Sliding Mode Control Design for Near Space Hypersonic Vehicles

This paper presents an adaptive nonsingular terminal sliding mode approach for the attitude control of near space hypersonic vehicles (NSHV) in the presence of parameter uncertainties and external disturbances. Firstly, a novel nonsingular terminal sliding surface is developed and its finitetime convergence is analyzed. Then, an adaptive nonsingular terminal sliding mode control law is proposed, which is chattering free. In the proposed approach, all parameter uncertainties and external disturbances are lumped into one term, which is estimated by an adaptive uncertainty estimation for eliminating the boundary requirement needed in the conventional control design. Subsequently, stability of the closed-loop system is proven based on Lyapunov theory. Finally, the proposed approach is applied to the attitude control design for NSHV. Simulation results show that the proposed approach attains a satisfactory performance in the presence of parameter uncertainties and external disturbances.      

航天器姿态跟踪系统的自适应滑模控制

针对存在不确定惯量矩阵和外干扰的刚体航天器姿态跟踪系统,提出了一种自适应滑模控制方法。首先建立了姿态跟踪误差动力学方程,并对刚体航天器跟踪误差动力学定义了滑模,设计了自适应滑模控制律,该控制律的优点在于可以估计系统不确定块,消除了传统滑模控制中对不确定界的要求。Lyapunov分析表明了提出的自适应滑模控制器确保闭环系统取得渐近稳定性。仿真结果验证了提出的控制策略的有效性。     

基于新型动态积分滑模的运载火箭姿态控制

运载火箭在飞行过程中面临着参数变化范围大、外界干扰复杂的飞行环境,传统的控制方法已经很难满足姿态控制系统的要求.本文将传统的动态滑模和积分滑模综合起来,尝试一种新型的动态积分滑模控制策略律.仿真结果表明,在存在系统参数摄动和外部干扰的情况下,该法很好的消除了抖振,取得较理想的控制效果.     

Characteristic Model-based Discrete-time Sliding Mode Control for Spacecraft with Variable Tilt of Flexible Structures

In this paper, the finite-time attitude tracking control problem for the spacecrafts with variable tilt of flexible appendages in the conditions of exogenous disturbances and inertia uncertainties is addressed. First the characteristic modeling method is applied to the problem of the spacecraft modeling. Second, a novel adaptive sliding mode surface is designed based on the characteristic model. Furthermore, a discrete-time sliding mode control (DTSMC) law, which makes the tracking error converge into a predefined bound in finite time, is proposed by employing the parameters of characteristic model associated with the sliding mode surface to provide better performances, robustness, faster response, and higher control precision. The designed DTSMC includes the adaptive control architecture and is chattering-free. Finally, digital simulations of a sun synchronous orbit satellite (SSOS) are presented to illustrate effectiveness of the control strategies as well as to verify the practical feasibility of the rapid maneuver mission.      

Output Feedback Terminal Sliding Mode Control for a Class of Second Order Nonlinear Systems

In this study, a novel output feedback terminal sliding mode control (TSMC) approach is proposed for a class of second order nonlinear systems in light of the equivalent output injection sliding mode observer (SMO) method and TSMC principle. The SMO method is applied to reconstruct full states in finite time and the non‐singular TSMC algorithm is designed to stabilize system states to equilibrium points in finite time. The corresponding stability analysis is presented. An indispensable illustrative example is bench tested to validate the effectiveness of the proposed approach.