A finite-time approach to formation control of multiple mobile robots with terminal sliding mode

In this study, a new finite-time synchronised approach is developed for multiple mobile robots formation control based on terminal sliding mode control principle and system synchronisation theory. Associated stability analysis is presented to lay a foundation for analytical understanding in generic theoretical aspects and safe operation for real systems. An illustrative example of multiple mobile robots formation control is bench tested to validate the effectiveness of the proposed approach.     

基于预设性能的非仿射非线性系统自适应有限时间控制

针对一类具有死区的非仿射非线性系统,将预设性能控制与有限时间控制相结合,提出一种具有预设性能的自适应有限时间跟踪控制方法.基于Backstepping技术、模糊逻辑系统及有限时间Lyapunov稳定理论,给出使系统半全局实际有限时间稳定(semi-globally practically finite-time stable,SGPFS)的充分条件和设计步骤.该控制策略不仅使系统的输出误差在有限时间内收敛到一个预先设定区域,同时保证其收敛速度、最大超调量和稳态误差均满足预先设定的性能要求.最后通过仿真示例验证了所提出设计方法的有效性.     

Command filter-based finite-time adaptive tracking control for MIMO dynamic systems with external disturbances and prescribed performance constraints

This paper investigates command filter-based finite-time stability of multi-input multi-output (MIMO) dynamic systems with prescribed performance constraints and external disturbances. A novel finite-time differentiator is introduced into command filter-based control scheme, which improves transient performance of each subsystem. Meanwhile, disturbance observers are utilized to eliminate negative effects on control system caused by external disturbances. Furthermore, featured with a selected performance function, it can be guaranteed that tracking errors remain in prescribed performance region. Stability analysis of the proposed controller is presented by using a Lyapunov function including transformed filter errors, parameter errors of neural networks, and observed errors of lumped disturbances. Effectiveness of proposed control method is verified by a numerical example and a practical system of inverted pendulums, respectively.     

Adaptive non-singular fast terminal sliding mode based on prescribed performance for robot manipulators

A fast convergent non-singular terminal sliding mode adaptive control law based on prescribed performance is formulated to solve the uncertainties and external disturbances of robot manipulators. First, the tracking error of robot manipulators is transformed by using the prescribed performance function, which improves the transient behaviors and steady-state accuracy of robot manipulators. Then, a novel fast convergent non-singular terminal sliding mode surface is brought up according to the transformed error, and the control law is derived to meet the stability requirements of robot manipulators. In practice, the upper boundary of the lumped disturbances cannot be accurately obtained. Therefore, an adaptive prescribed performance control (PPC) controller to lumped disturbances is brought up to ensure the stability and finite-time convergence of robot manipulators. Finally, the system stability of robot manipulators is proved by the Lyapunov theorem. Simulation results and comparative analysis demonstrate the superiority and robustness of the raised strategy.     

Adaptive prescribed performance sliding mode control based on time-varying barrier function

In this paper, a nonoverestimated adaptive prescribed performance sliding mode control algorithm based on time-varying barrier function is proposed, for high-order integrator systems subject to bounded but unknown disturbances. The developed algorithm has some remarkable features. Firstly, it is able to ensure that the system states are confined in a performance function from the initial instant. Secondly, it is easy-implementable and some exponential stability and practical fixed-time stability algorithms can be easily obtained. Finally, with the system states to be known, the size of the performance function is independent of the upper bound of the external disturbance. To show the efficiency of the developed algorithm, some numerical simulations are provided.     

Model-free prescribed performance fast nonsingular terminal sliding mode control with practical finite-time stability of uncertain robot manipulators

This paper addresses the problem of robust and high precision trajectory tracking control of uncertain robot manipulators with prescribed performance. Time delay estimation (TDE) technique is employed to estimate system model, then a new self-adjusting strategy (SAS) is designed to adjust TDE gain online. Prescribed performance control (PPC) method is used to guarantee transient response speed and steady-state accuracy. Moreover, the transform function of PPC employed in this paper has unlimited domain, which greatly improves the robustness and stability of system. An improved fixed-time dynamical system is firstly deduced and analyzed, then a new fast nonsingular terminal sliding mode surface is designed to accelerate convergence rate of tracking errors. Finally, the whole system is strictly proven to be practical finite-time stable, which means that tracking errors can converge to a small neighborhood of zero within a uniformly bounded convergence time. Main advantages of the proposed approach include model-free, robust, singularity-free, faster transient response and higher steady-state tracking precision. Experimental results carried out on the Rethink Sawyer Robot also verified the effectiveness of the proposed scheme.     

随机激励下板球系统建模与有限时间全状态预设性能跟踪控制

研究板球系统受到随机激励时的数学建模与轨迹跟踪控制问题.首次建立了板球系统的随机数学模型,并结合backstepping方法、有限时间预设性能函数、全状态约束及新的预设性能推导方法设计了具有未知输入饱和的随机板球系统实际有限时间全状态预设性能跟踪控制器,实现了随机激励下板球系统的有限时间预设性能轨迹跟踪控制.所设计的控制器保证了系统跟踪误差能够被预先给定的有限时间性能函数约束,并且能在任意给定的停息时间内收敛到预先给定的邻域内.最后通过仿真实验验证了所设计控制器具有更好的控制效果.     

永磁同步电机有限时间预设性能控制

为实现扰动作用下对永磁同步电机角位置伺服系统的高瞬态和稳态跟踪性能控制,本文提出一种具有预设性能约束的有限时间控制方法.首先,设计扰动观测器实现对负载力矩扰动的估计与补偿.其次,引入有限时间预设性能函数以保证角跟踪误差的动态性能,并通过可逆变换将受不等式约束的角位置跟踪误差转换为等效的无约束误差形式.然后,将有限时间指...     

基于龙伯格观测器的感应电机预设性能位置跟踪优化控制EI北大核心CSCD

考虑暂稳态约束、控制参数优化及参数摄动和负载扰动等对感应电机位置跟踪控制性能的影响,本文提出了一种基于龙伯格观测器的预设性能优化控制方法.首先,针对电机转子磁链在实际中不可测的问题,采用龙伯格观测器对其进行了快速准确的估计.其次,基于反步法完成感应电机位置预设性能控制器的设计,基于变增益指数趋近律完成感应电机磁链滑模控制器的设计,通过构造干扰观测器对电机系统中由参数摄动和负载扰动引起的不确定项进行观测,实现了对系统给定值准确的跟踪控制.再次,将遗传算法(GA)与改进的粒子群优化(IPSO)算法相结合,对所设计的控制器参数进行优化整定,进一步提高了系统的收敛速度和稳态精度.基于李雅普诺夫稳定性理论分析表:所设计的控制器能够保证位置跟踪误差一直处于预设边界内,且整个闭环系统是全局一致有界稳定的.最后,通过仿真和模拟实验对比分析验证了本文所提方法的有效性及在实际电机系统中应用的可行性.     

多智能体系统的有限时间包含控制研究

在固定有向拓扑结构下,研究了具有多个静态或动态领导者的多智能体有限时间包含控制问题;假设领导者之间不存在信息的交互,提出基于快速终端滑模的控制算法,该算法驱使跟随者的运动轨迹在有限时间收敛到由领导者组成的凸包中;进一步,考虑实际应用中跟随者状态不能在线获得的情况,提出基于有限时间观测器的包含控制协议;利用图论和Lyapunov有限时间稳定性理论,给出了有限时间包含控制的充分条件;最后通过仿真示例,验证了算法的有效性.     

小型四旋翼无人机建模与有限时间控制

本文首先介绍了一种小型四旋翼无人机的设计过程,从机架设计、动力匹配、机载控制器、传感器、无线通信等多个方面进行了较为详尽的阐述.采用牛顿―欧拉法对四旋翼无人机进行动力学分析,完成了六自由度数学模型的推导.进一步对系统的模型参数进行了测量和计算,并给出了结果.在此基础上,为了满足无人机快速跟踪性能的要求,本文基于快速终端滑模的思想,进行了闭环控制器的设计,并给出了基于Lyapunov函数的稳定性证明.控制器采用分环控制的结构形式,内环为姿态控制,外环为位置控制.最后结合设计的四旋翼无人机,给出的仿真结果验证了控制算法的有效性.     

Distributed prescribed performance control for consensus output tracking of nonlinear semi-strict feedback systems using finite-time disturbance observers

The distributed consensus output tracking 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 systems are under a directed communication graph, where the leader node is the root. The controller is designed in a backstepping manner, and the dynamic surface technique is adopted to avoid direct differentiation. At each step of virtual controller design, a prescribed performance controller is constructed to achieve prescribed transient performance so that the system states remain in the feasible domain. Then each virtual controller is enhanced by a finite-time disturbance observer which estimates the disturbance term in a finite-time. The properties of the control system are analysed theoretically. It is clarified that the prescribed performance control technique ensures that the system signals stay in the feasible domain, whereas sufficiently small ultimate control errors can be achieved by the finite-time disturbance observers. Finally, the performance of the proposed methods is confirmed by numerical studies.     

Finite time time-varying formation tracking for second-order multiagent systems with prescribed transient performance

This paper studies the finite time output formation tracking for a class of second-order multiagent systems subject to prescribed transient performance. The considered leader–follower time-varying formation tracking is realized under a directed communication topology. First, a performance function is introduced into a time-varying barrier Lyapunov function (TV-BLF) for the purpose of shaping the transient behavior. Then, based on the TV-BLF and adding a power integrator technology, a distributed formation control law is constructed such that all followers can form a predefined formation pattern while tracking the leader in finite time with satisfied transient performance. Moreover, a robust term is designed in the proposed controller to improve the disturbance rejection capability of the formation system. Finally, a simulation example is carried out to verify the effectiveness and superiority of the presented formation control protocol.     

Integrated interceptor guidance and control with prescribed performance

Robustness and transient performance are the key performance indexes of the integrated interceptor guidance and control. However, these two performances have not yet been guaranteed comprehensively before. In this paper, a robust integrated interceptor guidance and autopilot controller is presented with prescribed steady state and transient performances of interception. On the basis of the dynamic surface control technique, the robustness of the proposed controller is improved by signal compensation. By utilizing the prescribed performance control theory, the transformed system of original integrated guidance and control model is stabilized to guarantee the prescribed performance of interception. It is proven that the stability of the transformed system is obtained by the loose selection of controller parameters, and therefore, the system robustness has been improved. Simulation results are included to verify the effectiveness of the proposed approach. Copyright © 2014 John Wiley & Sons, Ltd.     

基于积分滑模的航天器有限时间姿态容错控制

针对存在执行机构故障和外部干扰的刚体航天器姿态稳定系统,本文提出了基于积分滑模的容错控制策略,实现了姿态有限时间稳定.首先,利用齐次系统相关理论,设计了一类饱和有界的基础控制律,保证了不存在执行机构故障和干扰情况下的姿态有限时间稳定.在此基础上,利用积分滑模和自适应技术设计了一种有限时间姿态鲁棒容错控制方案,对执行机构故障和干扰进行有效的补偿;该方案能够快速地实现姿态高精度稳定,并抑制系统抖振现象.最后,将本文提出的姿态容错控制方案进行数值仿真与对比,验证了方案的有效性与优越性.     

基于预设性能的船舶直流微电网终端滑模反推控制

为了解决船舶直流微网中负载突变带来的直流母线电压波动问题,本文首先在微网中引入混合储能系统并构建船舶直流微网的数学模型,接着采用一阶低通滤波的策略分配差额功率,最后设计了一种基于预设性能的终端滑模反推控制策略.在控制器中引入预设性能函数,使直流母线的跟踪误差按照预设的曲线进行快速收敛,定义跟踪误差的终端滑模面并利用反推...     

Reduced-order observer-based output feedback control of nonlinear time-delay systems with prescribed performance

This paper studies the problem of output feedback control for a class of nonlinear time-delay systems with prescribed performance. The system is in the form of triangular structure with unmodelled dynamics. First, we introduce a reduced-order observer to provide the estimate of the unmeasured states. Then, by setting a new condition with the performance function, we design the state transformation with prescribed performance control. By employing backstepping method, we construct the output feedback controller. It is proved that the resulting closed-loop system is asymptotically stable and both transient and steady-state performance of the output are preserved with the changing supply function idea. Finally, a simulation example is conducted to show the effectiveness of the main results.     

Decentralised finite-time attitude synchronisation and tracking control for rigid spacecraft

The problem of finite-time attitude synchronisation and tracking for a group of rigid spacecraft nonlinear dynamics is investigated in this paper. First of all, in the presence of environmental disturbance, a novel decentralised control law is proposed to ensure that the spacecraft attitude error dynamics can converge to the sliding surface in finite time; then the final practical finite-time stability of the attitude error dynamics can be guaranteed in small regions. Furthermore, a modified finite-time control law is proposed to address the control chattering. The control law can guarantee a group of spacecraft to attain desired time-varying attitude and angular velocity while maintaining attitude synchronisation with other spacecraft in the formation. Simulation examples are provided to illustrate the feasibility of the control algorithm presented in this paper.     

Adaptive prescribed performance control for switched nonlinear systems with input saturation

In this paper, an adaptive prescribed performance output-feedback control scheme is proposed for a class of switched nonlinear systems with input saturation. The MT-filters are employed to estimate the unmeasured states and the unknown functions are approximated by the radial basis function neural networks in controller design procedure. It is proved that all the signals in the closed-loop system are semi-globally uniformly ultimately bounded and the tracking error satisfies the prescribed performance. Finally, simulation results are given to illustrate the effectiveness of the proposed approach.     

控制方向未知的高次不确定非线性系统低复杂度预定性能控制

本文研究了控制方向未知的高次不确定非线性系统预定性能控制问题.基于有理分式函数类型的误差转换,通过设计具有切换形式的控制器,提出了一种低复杂度的控制方法,并利用Lyapunov理论和反证法证明了闭环系统稳定性.与现有其他方法相比,该方法具有适用范围广、跟踪精度高、容错能力强、控制器简单等优点.仿真结果验证了本文结论.