Composite Nonlinear Bilateral Control for Teleoperation Systems With External Disturbances

This paper presents a new composite nonlinear bilateral control method based on the nonlinear disturbance observer (NDOB) for teleoperation systems with external disturbances. By introducing the estimations of NDOB and systems' nominal nonlinear dynamics into controller design, a NDOB based composite nonlinear bilateral controller is constructed to attenuate the influence of disturbance and uncertain nonlinearities. As compared with the existing bilateral control methods which usually achieve force haptic (i.e., contact force tracking) through a passive way, the newly proposed method has two major merits: 1) asymptotical convergence of both position and force tracking errors is guaranteed; 2) disturbance influence on force tracking error dynamics is rejected through the direct feedforward compensation of disturbance estimation. Simulations on a nonlinear teleoperation system are carried out and the results validate the effectiveness of the proposed controller.      

LESO-based Position Synchronization Control for Networked Multi-Axis Servo Systems With Time-Varying Delay

The position synchronization control (PSC) problem is studied for networked multi-axis servo systems (NMASSs) with time-varying delay that is smaller than one sampling period. To improve the control performance of the system, time-varying delays, modeling uncertainties, and external disturbances are first modeled as a lumped disturbance. Then, a linear extended state observer (LESO) is devised to estimate the system state and the lumped disturbance, and a linear feedback controller with disturbance compensation is designed to perform individual-axis tracking control. After that, a cross-coupled control approach is used to further improve synchronization performance. The bounded-input-bounded-output (BIBO) stability of the closed-loop control system is analyzed. Finally, both simulation and experiment are carried out to demonstrate the effectiveness of the proposed method.      

不确定时变时滞系统稳定性的Riccati方程法

讨论了不确定时变时滞系统的基于观测器后次稳定性问题,有两类不确定性被讨论,利用Ｌｙａｐｕｎｏｖ稳定性定理及范数不等式,我们证明了几个关于二次稳定性的定理,通过求解Ｒｉｃｃａｔｉ方程可以获得系统可二次稳定的状态反馈控制器,最后,通过实例验证了上述结果。     

无源散射变换的双边移动机器人网络遥操作

网络遥操作系统的随机时延给控制器设计带来巨大挑战,严重时破坏系统的稳定性。首先对遥操作无源理论及其波变量控制方法做了简单综述,然后提出直接无源散射变换方法,它将无源双边控制方法推广到具有随机时延的网络遥操作系统中去,保证网络遥操作系统在任何不对称随机网络时延情况下稳定。最后基于此变换方法设计了一个虚拟主从手双边移动机器人网络遥操作方案,并进行了仿真验证,结果表明结出的设计方法能满足系统性能要求。     

多自由度遥操作系统控制的波变量法

为了将波变量方法用于多自由度遥操作系统,提出了一种更具一般性的多自由度遥操作系统的波变换公式,并扩展了公式参数的选择原则.首先分析了波变量法的原理,并用波变换矩阵替换波阻抗常数b得到多自由度系统的波变换公式.然后从能量的角度分析了波阻抗矩阵的选择原则,根据此选择原则扩展了波阻抗矩阵的选择方法和矩阵之间的约束关系.接着基于耗散理论,分析了扩展的波阻抗矩阵的无源性.最后以3自由度主从遥操作系统为例,分别进行了仿真实验和机器人遥操作实验,实验结果表明所提出的波变换公式能够保证多自由度遥操作系统在时延条件下的稳定性.     

Secure Consensus Control for Multi-Agent Systems With Attacks and Communication Delays

This paper addresses the consensus problem for nonlinear multi-agent systems suffering from attacks and communication delays. The network studied in this paper consists of two types of agents, namely, loyal agents and attack agents. The loyal agents update their states based on delayed state information exchanged with their neighbors. Meanwhile, the attack agents can strategically send messages with wrong values, or collude with other attack agents to disrupt the correct operation of the system. We design a novel delay robust secure consensus (DRSC) algorithm according to the neighboring nodes' delayed information. Convergence analysis of the system under the protocol designed is provided by using Lyapunov-Krasovskii stability theory and Barbalat-like argument approach. Finally, an example and simulation results are presented to demonstrate the effectiveness of the algorithm.      

具有多时变时滞的单一和复合线性系统的时滞无关稳定性判据

针对单一和复合多时变时滞系统分别建立了稳定性的充分条件,结果的推导采用了拉什密辛（Ｒａｚｕ－ｍｉｋｈｉｎ）定理结合代数不等式的方法,同时,本文提出了一些优化稳定性判据中参数的方法,所建判据既不依赖于时滞的大小也不依赖时滞的导数,故既适用于时变时滞系统也适用于常时滞系统或无无时滞系统,最后,给出了一些例子所提方法的应用,并比较文献中存在的结果。     

Guaranteed Cost Consensus for High-dimensional Multi-agent Systems With Time-varying Delays

Guaranteed cost consensus analysis and design problems for high-dimensional multi-agent systems with timevarying delays are investigated. The idea of guaranteed cost control is introduced into consensus problems for high-dimensional multi-agent systems with time-varying delays, where a cost function is defined based on state errors among neighboring agents and control inputs of all the agents. By the state space decomposition approach and the linear matrix inequality (LMI), sufficient conditions for guaranteed cost consensus and consensualization are given. Moreover, a guaranteed cost upper bound of the cost function is determined. It should be mentioned that these LMI criteria are dependent on the change rate of time delays and the maximum time delay, the guaranteed cost upper bound is only dependent on the maximum time delay but independent of the Laplacian matrix. Finally, numerical simulations are given to demonstrate theoretical results.      

一类线性时变系统的输出反馈控制

基于线性时不变系统能控能观标准型变换及非线性系统高增益观测器方法,本文研究了一类线性时变系统 的输出反馈控制问题. 通过引入时变的状态变量坐标变换,分别设计了线性时变系统的状态反馈控制器、状态观测器以及基于 状态观测器的输出反馈控制器. 进一步地,本文分别证明了观测器动态误差是渐近收敛于零的,而状态反馈控制器以及输出反馈控制器可以 保证闭环系统的渐近稳定性.     

Finite-time Prescribed Performance Time-Varying Formation Control for Second-Order Multi-Agent Systems With Non-Strict Feedback Based on a Neural Network Observer

This paper studies the problem of time-varying formation control with finite-time prescribed performance for nonstrict feedback second-order multi-agent systems with unmeasured states and unknown nonlinearities. To eliminate nonlinearities, neural networks are applied to approximate the inherent dynamics of the system. In addition, due to the limitations of the actual working conditions, each follower agent can only obtain the locally measurable partial state information of the leader agent.To a...     

Novel Stability Criteria for Linear Time-Delay Systems Using Lyapunov-Krasovskii Functionals With A Cubic Polynomial on Time-Varying Delay

One of challenging issues on stability analysis of time-delay systems is how to obtain a stability criterion from a matrix-valued polynomial on a time-varying delay.The first contribution of this paper is to establish a necessary and sufficient condition on a matrix-valued polynomial inequality over a certain closed interval.The degree of such a matrix-valued polynomial can be an arbitrary finite positive integer.The second contribution of this paper is to introduce a novel LyapunovKrasovskii functional,which includes a cubic polynomial on a time-varying delay,in stability analysis of time-delay systems.Based on the novel Lyapunov-Krasovskii functional and the necessary and sufficient condition on matrix-valued polynomial inequalities,two stability criteria are derived for two cases of the time-varying delay.A well-studied numerical example is given to show that the proposed stability criteria are of less conservativeness than some existing ones.     

Teleoperation in the presence of varying time delays and sandwich linearity in actuators

In this paper, a novel control scheme is proposed to guarantee global asymptotic stability of bilateral teleoperation systems that are subjected to time-varying time delays in their communication channel and sandwich linearity in their actuators. This extends prior art concerning control of nonlinear bilateral teleoperation systems under time-varying time delays to the case where the local and the remote robots’ control signals pass through saturation or similar nonlinearities that belong to a class of systems we name sandwich linear systems. Our proposed controller is similar to the proportional plus damping (P+D) controller with the difference that it takes into account the actuator saturation at the outset of control design and alters the proportional term by passing it through a nonlinear function; thus, we call the proposed method as nonlinear proportional plus damping (nP+D). The asymptotic stability of the closed-loop system is established using a Lyapunov–Krasovskii functional under conditions on the controller parameters, the actuator saturation characteristics, and the maximum values of the time-varying time delays. To show the effectiveness of the proposed method, it is simulated on a variable-delay teleoperation system comprising a pair of planar 2-DOF robots subjected to actuator saturation. Furthermore, the controller is experimentally validated on a pair of 3-DOF PHANToM Premium 1.5A robots, which have limited actuation capacity, that form a teleoperation system with a varying-delay communication channel.     

基于观测器的不确定动态时滞系统鲁棒镇定的Riccati方程方法

本文给出了一类不确定动态时滞系统基于观测器的鲁棒镇定方法，该类系统的状态、输人和输出矩阵均含有不确定性，且不确定性需满足给定的匹配条件，系统不仅有状态时滞，还有控制时滞，该方法通过求解两个代数Riccati方程实现，本文比较全面地解决了满足匹配条件的不确定动态时滞系统的鲁棒镇定问题．     

带时变时延的网络化控制系统控制器设计方法

为带时变时延的网络化控制系统提出了一种新的状态反馈控制器的设计方法.根据控制系统的时滞相关稳定性条件来设计确保网络化控制系统稳定性的控制器,并以线性矩阵不等式的形式描述.该方法可进一步扩展到解决鲁棒控制问题.最后的仿真实例表明了该方法的有效性.     

时延遥操作系统的能量观测与控制研究进展

能量观测与控制方法基于无源理论,在有源网络端口观测力和速度(位置)信号,分析并动态补偿能量以保持网络稳定,无需控制对象模型信息和通信传输时延估计。综述了时延遥操作系统的一端口和二端口网络能量观测与控制方案的研究进展,讨论了存在的主要问题,并指出进一步研究的方向为定量分析操作性能、改进控制器工作条件、克服传感器影响和安全操作等。     

Robust Output Feedback Control for Fractional Order Nonlinear Systems with Time-varying Delays

Robust controller design problem is investigated for a class of fractional order nonlinear systems with time varying delays. Firstly, a reduced-order observer is designed. Then, an output feedback controller is designed. Both the designed observer and controller are independent of time delays. By choosing appropriate Lyapunov functions, we prove the designed controller can render the fractional order system asymptotically stable. A simulation example is given to verify the effectiveness of the proposed approach.      

基于时变输出约束的机器人遥操作有限时间控制方法

受操作时间窗口和工作空间的限制,空间遥操作任务需要在有限时间内完成,同时确保末端执行器满足物理约束。此外,时延和外部扰动使不确定遥操作系统的稳定性和控制性能受到严重影响。为此,本文提出了一种基于时变输出约束的机器人遥操作有限时间控制方法。首先,利用积分障碍李雅普诺夫函数处理操作空间的时变约束问题,实用有限时间李雅普诺夫稳定定理保证了系统的快速稳定性。然后,利用神经网络估计环境力以及消解模型不确定性带来的影响,利用鲁棒项补偿神经网络的估计偏差和消解未知外部扰动的影响。最后,在Matlab/Simulink环境下同其他算法进行仿真对比,并在地面实验平台上验证了该算法,理论仿真和实验结果表明该方法进一步提高了误差收敛速率和收敛精度,且系统的输出不会超出预先设定的时变边界。     

A Composite State Convergence Scheme for Bilateral Teleoperation Systems

State convergence is a novel control algorithm for bilateral teleoperation of robotic systems. First, it models the teleoperation system on state space and considers all the possible interactions between the master and slave systems. Second, it presents an elegant design procedure which requires a set of equations to be solved in order to compute the control gains of the bilateral loop. These design conditions are obtained by turning the master-slave error into an autonomous system and imposing the desired dynamic behavior of the teleoperation system. Resultantly, the convergence of master and slave states is achieved in a well-defined manner. The present study aims at achieving a similar convergence behavior offered by state convergence controller while reducing the number of variables sent across the communication channel. The proposal suggests transmitting composite master and slave variables instead of full master and slave states while keeping the operator’s force channel intact. We show that, with these composite and force variables; it is indeed possible to achieve the convergence of states in a desired way by strictly following the method of state convergence. The proposal leads to a reduced complexity state convergence algorithm which is termed as composite state convergence controller. In order to validate the proposed scheme in the absence and presence of communication time delays, MATLAB simulations and semi-real time experiments are performed on a single degree-of-freedom teleoperation system.      

空间遥操作机器人主从双边自适应内模控制

天地大时延严重破坏具有力反馈的空间遥操作机器人系统的稳定性和透明性;针对天地大时延和未知的从手操作环境,基于内模控制和自适应控制思想设计一种自适应内模控制器;推导从手环境参数辨识模型,基于带遗忘因子的递推最小二乘滤波辨识环境模型,并利用辨识信息构建自适应内模控制器;基于单参数SNPIDC算法分别设计主手和从手自适应控制器;大量的仿真结果证明,在设计的主从双边自适应内模控制器作用下,空间遥操作机器人系统稳定性好,对未知环境适应能力强,系统透明性好,阻抗匹配程度高,且操作人员临场感强。     

Robust Output Feedback Stabilization for Uncertain Discrete-Time Fuzzy Markovian Jump Systems With Time-Varying Delays

This paper provides a delay-dependent approach to the design of fuzzy dynamic output feedback controllers for uncertain discrete-time fuzzy Markovian jump systems with interval time-varying delays. First, by a fuzzy-basis-dependent and mode-dependent Lyapunov functional, a stochastic stability condition is derived by using the Finsler's lemma. Second, in terms of linear matrix inequalities (LMIs), a delay-dependent sufficient condition is presented, under which there exists a fuzzy output feedback controller such that the resulting closed-loop system is robustly stochastically stable. A desired controller can be constructed when these LMIs are feasible. Finally, the effectiveness of the proposed design method is demonstrated by a simulation example.