力觉临场感遥操作机器人系统的鲁棒控制

力觉临场感遥操作机器人系统的通信通道中存在通信时延,而且在机器人和环境建模中,系统参数存在不确定性,以致可能造成系统不稳定和操作性能降低.针对通信时延和系统不确定性,建立系统的状态方程,利用鲁棒控制理论,提出用力、位置和速度反馈的控制方法.分析与实验表明,用该方法设计的控制器能使系统鲁棒渐近稳定,而且能使系统完全透明.     

非线性网络控制系统的保性能控制

针对网络诱导时延小于一个采样周期的非线性网络控制系统,研究了系统的稳定性和保性能控制问题.对于T-S模糊模型描述的非线性被控对象,将时延的不确定性转化为系统参数的不确定性,从而将这一类非线性网络控制系统建模为具有参数不确定性的离散T-S模糊模型.基于建立的模型,提出了存在稳定保性能控制器的充分条件,并得出了相应的线性矩阵不等式(LMI)形式.最后通过对永磁同步电动机混沌系统进行控制和仿真研究,验证了所提出方法的有效性.     

多径路由网络化控制系统的路径调度与控制器协同设计北大核心CSCD

研究了带有多径通信路由的网络化控制系统的通信路径调度和控制器的协同设计问题.通过将不同通信路径切换及带来的时延变化建模为系统模态的切换,得到了所研究系统的切换系统模型.给出了使得闭环系统指数稳定的通信路径调度所需满足的条件,并提出了满足系统稳定和网络负载均衡的闭环通信路径调度方案和控制器设计方法.数值仿真算例验证了算法的优越性和有效性.     

多径路由网络化控制系统的路径调度与控制器协同设计

研究了带有多径通信路由的网络化控制系统的通信路径调度和控制器的协同设计问题.通过将不同通信路径切换及带来的时延变化建模为系统模态的切换,得到了所研究系统的切换系统模型.给出了使得闭环系统指数稳定的通信路径调度所需满足的条件,并提出了满足系统稳定和网络负载均衡的闭环通信路径调度方案和控制器设计方法.数值仿真算例验证了算法的优越性和有效性.     

具有状态时延和网络诱导时延的非线性网络系统的指数稳定控制

研究了一类具有状态时延和网络诱导时延的非线性不确定性网络系统的指数稳定控制问题。利用T-S模糊控制方法,建立了非线性网络系统模型。基于Lyapunov稳定性理论和线性矩阵不等式方法,得到系统指数稳定的充分条件。并在此基础上设计系统的状态反馈模糊控制器。最后仿真算例说明了该方法的有效性。     

时延混成系统的切换控制器合成

如何设计安全、可靠的信息物理融合系统是计算机科学和控制理论面临的一个重大挑战.时延现象在信息物理融合系统中普遍存在,时延对系统的稳定性、安全性和控制性能具有实质性影响.但是在已有时延系统验证和控制器合成的工作中往往忽略时延因素,这会导致在不考虑时延情况下能保证稳定和安全的系统在实际运行时因为时延原因而不再稳定和安全.因为时延使得系统的行为演化不仅与当前状态有关,还依赖于系统的历史状态,所以时延混成系统的验证和控制合成更加困难.本文研究信息物理融合系统在考虑时延情形下切换控制器合成问题,提出基于不变式生成技术的控制器合成方法.首先,利用谱分析和线性化技术将时延系统的微分不变式生成问题归结为有界时间的可达集计算问题;然后,提出基于抽象精化的算法计算时延系统有界时间可达集的上近似;最后,实现本文算法并使用实例验证该方法的有效性.     

基于均方指数稳定的随机时延网络系统的输出反馈控制

研究了随机时延网络系统的输出反馈控制问题.通过把网络诱导时延和数据丢包看做满足区间Bernoulli分布的等价时延,建立了随机时延网络系统模型.基于随机系统稳定性理论,以线性矩阵不等式形式给出了系统均方指数稳定条件和输出反馈控制器设计方法.仿真结果说明了该方法的有效性.     

具有时延和无时延加权多智能体系统一致性

针对存在全局可达节点有向加权图的静态网络,研究了在控制算法中引入不同权重的当前状态和时延状态时多智能体系统一致性问题.通过采用频域控制理论中广义Nyquist准则和Gerschgorin圆盘定理,证明了系统渐近稳定收敛到一致性的充分条件,提出一种改进系统实现一致性的最大时延上界方法;最后通过数值仿真验证了结论的正确性.     

自主仿生机器鱼水下电场通信的设计与实现

水下机器人由于工作环境的特殊性,导致其通信困难.文章首先设计一套水下电场通信系统,并且将此通信系统集成到仿生机器鱼上.值得注意的是,它解决了多个水下机器人在传统的的通信方式下不能正常通信的问题.其次,针对电流场的物理特性设计了一系列的实验来验证理论的可行性,引入误码率(BER)来评估通信系统的稳定性.最后,通过外部发射装置并应用水下电场通信系统来控制机器鱼的各种游动模态.该通信系统在水下机器人的近距离通信中有很好的应用前景.     

基于事件驱动的拉格朗日无源系统的输出同步控制

针对由多个拉格朗日无源系统构成的分布式网络系统,利用基于事件驱动的方法来解决系统的输出同步问题.在拓扑网络为强连通图的条件下,推导出无通信时延的拉格朗日无源系统网络输出同步的事件触发条件.进一步,利用网络设置框架,对于有通信时延的拉格朗日无源系统网络推导出输出同步的事件触发条件.文章将事件驱动控制方法应用到分布式无源网络系统的协同控制中,并将系统的拓扑网络由平衡图延伸到了更为一般的强连通图.     

Cucker–Smale flocking under rooted leadership and time-varying heterogeneous delays

In this paper, a Cucker–Smale model with time-varying heterogeneous delays in the communication process is investigated, where the delay on each communication link is time-varying and independent of other communication links. A general update rule based on the distance between agents is used to determine the edge weights of the communication network. The method of constructing augmented system is used so that the system stability is transformed into a product convergence problem of time-varying sub-stochastic matrices equivalently. By analyzing this convergence problem, a sufficient condition is established to achieve flocking, which relates to the initial states, the structure of communication network and the upper bound of time delays.     

Leaderless and leader-following consensus of multi-agent chaotic systems with unknown time delays and switching topologies

In this paper the distributed consensus problem for a class of multi-agent chaotic systems with unknown time delays under switching topologies and directed intermittent communications is investigated. Each agent is modeled as a general nonlinear system including many chaotic systems with or without time delays. Based on the Lyapunov stability theory and graph theory, some sufficient conditions guarantee the exponential convergence. A graph-dependent Lyapunov proof provides the definite relationship among the bound of unknown time delays, the admissible communication rate and each possible topology duration. Moreover, the relationship reveals that these parameters have impacts on both the convergence speed and control cost. The case with leader-following communication graph is also addressed. Finally, simulation results verify the effectiveness of the proposed method.     

Real-time distributed control: A fuzzy and model predictive control approach for a nonlinear problem

Nowadays the study of faults and their consequences has become an issue for highly safety critical computer network systems. How to bound the effects of a fault and how to tackle them in a dynamic system is still an open field. Here, an approach to studying this problem is presented as a hybrid strategy. The use of a multi-model technique from the point of view of real-time systems and intelligent control structure is described, in order to accomplish one challenge: to overcome the problem of the presence of local faults and the respective time delays within a real-time distributed system. This approach is pursued as a reconfigurable strategy according to communication time delays within a real-time distributed system. In fact, it is pursued as a reconfigurable strategy according to communication delays and local faults where the control strategy is modified from several perspectives.     

Adaptive cooperative control of networked uncalibrated robotic systems with time‐varying communicating delays

This paper investigates the trajectory tracking control of the networked multimanipulator with the existence of time‐varying delays and uncertainties in both kinematics and dynamics. To address time‐varying delays in the communication links, a novel control scheme is established by the design of delay–rate‐dependent networking mutual coupling strengths. Besides, to handle the kinematic and dynamic uncertainties, an adaptive controller is designed. The proposed control scheme guarantees that the networked robotic system can track a commonly desired trajectory cooperatively with the strongly connected communication graph, uncertainties, and time‐varying communicating delays. A Lyapunov–Krasovskii functional is employed to rigorously prove the asymptotic convergence of both tracking errors and synchronization errors. The simulation results are provided to verify the effectiveness of the control method proposed by this paper.     

基于冗余任务的轮式机器人巡检方法

针对配电室电力设备智能化巡检工作中,存在巡检方式单一等问题,基于轮式巡检机器人结构及系统、路径优化和通信等关键技术,研究了一种基于冗余任务的轮式机器人巡检方法.针对目前配电室巡检环境和轮式巡检机器人结构及系统特性,建立配电室巡检过程模型.分析顺序巡检方法的速度、位姿和节点关系,建立机器人巡检过程的路程-时间模型和奖惩模型,根据能耗约束得到目标函数.最后,通过设计方法实验流程图,依次分析顺序巡检、任务巡检和冗余任务巡检的效益值.实验结果表明,冗余任务巡检方式在保证单位时间和单位行程能耗比率不变的前提下,降低了控制系统能耗,有效提高了人机交互的巡检效益,且更好地兼容远程监测人员经验与机器人巡检优势,为智能化巡检技术的研究和推广提供了思路和方法.     

Optimal Control via Asynchronous Communication Channels

The paper is directed toward the development of a new chapter of control theory that deals with networked systems in which control and communication issues are combined together and in which the delays and limitations of the communication channels between sensors, actuators, and controllers are taken into account. We consider a situation where a single decision maker receives the sensor data and at the same time controls many linear discrete-time partially-observed subsystems perturbed by white noises via randomly delayed communication channels with finite capacities. Neither these delays nor their statistics are known in advance, but each message transmitted is equipped with a time stamp indicating the beginning time of the transfer. Under certain assumptions, a finite-horizon linear-quadratic optimal control problem is solved.     

The sensitivity of optimal states to time delay

In the design and computation of optimal controls for systems that evolve in time, usually the effect of delay is ignored. However in the implementation of the computed optimal controls in the control systems often delays occur, for example through transmission via digital communication channels. The question to be addressed is whether such small delays can have large effects on a system that is steered by an optimal control. We show that for a system that is governed by the wave equation with L²-norm minimal exact Dirichlet boundary control, for arbitrarily small time-delays there are initial states such that the terminal energy is almost twice as big as the initial energy. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effects of time delays on bifurcation and chaos in a non-autonomous system with multiple time delays

Time delays are often sources of complex behavior in dynamic systems. Yet its complexity needs to be further explored, particularly when multiple time delays are present. As a purpose to gain insight into such complexity under multiple time delays, we investigate the mechanism for the action of multiple time delays on a particular non-autonomous system in this paper. The original mathematical model under consideration is a Duffing oscillator with harmonic excitation. A delayed system is obtained by adding delayed feedbacks to the original system. Two time delays are involved in such system, one of which in the displacement feedback and the other in the velocity feedback. The time delays are taken as adjustable parameters to study their effects on the dynamics of the system. Firstly, the stability of the trivial equilibrium of the linearized system is discussed and the condition under which the equilibrium loses its stability is obtained. This leads to a critical stability boundary where Hopf bifurcation or double Hopf bifurcation may occur. Then, the chaotic behavior of such system is investigated in detail. Particular emphasis is laid on the effect of delay difference between two time delays on the chaotic properties. A Melnikov’s analysis is employed to obtain the necessary condition for onset of chaos resulting from homoclinic bifurcation. And numerical analyses via the bifurcation diagram and the top Lyapunov exponent are carried out to show the actual time delay effect. Both the results obtained by the two analyses show that the delay difference between two time delays plays a very important role in inducing or suppressing chaos, so that it can be taken as a simple but efficient “switch” to control the motion of a system: either from order to chaos or from chaos to order.