Adaptive sliding mode observer‐based synchronization for uncertain chaotic systems

This paper investigates the synchronization problem for a class of uncertain chaotic systems. Only partial information of the system states is known. An adaptive sliding mode observer‐based slave system is designed to synchronize a given chaotic master system with unknown parameters and external disturbances. Based on the Lyapunov stability theorem, the global synchronization between the master and slave systems is ensured. Furthermore, the structure of the slave system is simple and the proposed adaptive sliding mode observer‐based synchronization scheme can be implemented without requiring a priori knowledge of upper bounds on the norm of the uncertainties and external disturbances. Simulation results demonstrate the effectiveness and robustness of the proposed scheme. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

不确定Van der Pol混沌系统的模糊同步控制

本文研究了不确定Van der Pol混沌系统的同步问题,并进行了基于规则的模糊逻辑控制器(FLC)的控制。首先寻找主从Van der Pol混沌系统满足Lyapunov稳定性理论的条件,在此基础上建立模糊规则,设计模糊控制器,实现不确定混沌系统的同步。通过不确定VanderPol混沌系统的两组仿真结果,验证了模糊同步控制方法具有很好的鲁棒性。最后为了进一步验证该方法的有效性,本文在相同条件下,利用反馈控制的方法实现不确定主从VanderPol混沌系统的同步,然后再将此方法的仿真结果与本文的模糊同步控制方法的仿真结果在稳态误差及同步所需时间这两个方面进行对比分析。分析结果验证了本文同步方法的可行性及有效性。     

Synchronization of bilateral teleoperators with time delay

Bilateral teleoperators, designed within the passivity framework using concepts of scattering and two-port network theory, provide robust stability against constant delay in the network and velocity tracking, but cannot guarantee position tracking in general. In this paper we fundamentally extend the passivity-based architecture to guarantee state synchronization of master/slave robots in free motion independent of the constant delay and without using the scattering transformation. We propose a novel adaptive coordination architecture which uses state feedback to define a new passive output for the master and slave robots containing both position and velocity information. A passive coordination control is then developed which uses the new outputs to state synchronize the master and slave robots in free motion. The proposed algorithm also guarantees ultimate boundedness of the master/slave trajectories on contact with a passive environment. Experimental results are also presented to verify the efficacy of the proposed algorithms.     

Synchronization of two different chaotic systems using Legendre polynomials with applications in secure communications

In this study, a new controller for chaos synchronization is proposed. It consists of a state feedback controller and a robust control term using Legendre polynomials to compensate for uncertainties. The truncation error is also considered. Due to the orthogonal functions theorem, Legendre polynomials can approximate nonlinear functions with arbitrarily small approximation errors. As a result, they can replace fuzzy systems and neural networks to estimate and compensate for uncertainties in control systems. Legendre polynomials have fewer tuning parameters than fuzzy systems and neural networks. Thus, their tuning process is simpler. Similar to the parameters of fuzzy systems, Legendre coefficients are estimated online using the adaptation rule obtained from the stability analysis. It is assumed that the master and slave systems are the Lorenz and Chen chaotic systems, respectively. In secure communication systems, observer-based synchronization is required since only one state variable of the master system is sent through the channel. The use of observer-based synchronization to obtain other state variables is discussed. Simulation results reveal the effectiveness of the proposed approach. A comparison with a fuzzy sliding mode controller shows that the proposed controller provides a superior transient response. The problem of secure communications is explained and the controller performance in secure communications is examined.     

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.     

PTP网络非对称时延抖动修正算法设计与分析

为了改进PTPV2时间同步网络非对称时延抖动对主从时钟同步精度的影响,设计了传输报文的非对称时延抖动修正算法。基本思路是在主从时钟交换报文信息中,找出最佳报文用于从时钟的调整。采用两级过滤先进增强时间恢复算法,即使发生网络传输阻塞,也能筛选出未受阻塞的幸运报文用于时钟偏差估计。新算法能够很容易集成到PTPV2协议中,而不会影响基本的报文信息交换。实际测试结果表明,新设计的时间恢复算法,在普通交换机网络中,可有效抑制非对称时延抖动,主从时钟同步精度也可优于100ns。     

Integrated adaptive robust control for multilateral teleoperation systems under arbitrary time delays

With the increasing industrial requirements such as bigger size object, stable operation, and complex task, multilateral teleoperation systems extended from traditional bilateral teleoperation are widely developed. In this paper, the integrated control design is developed for multilateral teleoperation systems, where n master manipulators are operated by human to remotely control n slave manipulators cooperatively handling a target object. For the first time, the control objectives of multilateral teleoperation including stability, synchronization, transparency, and internal force distribution are clarified systematically. A novel communication architecture is proposed to cope with communication delays, where the estimated environmental parameters are transmitted from the slave side to the master, to replace the traditional environmental force measurement in the communication channel. A kind of nonlinear adaptive robust control technique is used to deal with nonlinearities, unknown parameters, and modeling uncertainties existing in the master, slave, and environmental dynamics, so that the excellent tracking performance is achieved in both master and slave sides. The coordinated motion/force control is designed in the slave side by the optimal internal force distribution among n slave manipulators, and the impedance control is designed in the master side to realize the target transparency behavior. In summary, the proposed control algorithm can achieve the guaranteed robust stability, the excellent synchronization and transparency performance, and the optimal internal force distribution simultaneously for multilateral teleoperation systems under arbitrary time delays and various modeling uncertainties. The simulation is carried out on a 2‐master/2‐slave teleoperation system, and the results show the effectiveness of the proposed control design. Copyright © 2015 John Wiley & Sons, Ltd.     

Chaos synchronization and duration time of a class of uncertain chaotic systems

This paper addresses the problem of chaos synchronization from a control theoretic point of view. The main idea is to construct an augmented dynamical system from the synchronization error system, which is itself uncertain. A new dynamic output feedback is applied to perform synchronization in spite of master/slave mismatches. In this way, the nonidentical chaotic synchronization can be attained. The advantage of this method over the existing results is that the feedback controller has a predictable synchronization delay. The synchronization time is explicitly computed. Computer simulations are provided to verify the operation of the designed synchronization algorithm.     

预估控制下的实时网络遥操作移动机器人

构建了能使操作者通过Internet远程实时控制的移动机器人系统．为了补偿网络时延和抵消其对遥操作系统的影响,基于我们以前提出的改进型Smith预估器原理,采用了预估控制策略．为了保证系统稳定性和透明性,基于主从端的传感器信息交换,设计了一个动态模型管理器,其中模型和力反馈误差调节通过模糊控制实现．除了力反馈外,为了增强遥操作的实时性,引入了预估的虚拟显示．为了精确地预测网络时延,提出了一个新颖的时钟同步算法．为了降低时延抖动,结合我们提出的两个算法,实现了数据缓冲策略．最后,通过长距离的网络遥操作实验验证了系统和控制策略的实用性和有效性．     

基于改进主从控制结构的海洋机器人零航速减摇鳍系统

利用零航速减摇鳍系统实现对海洋机器人在近水面低速航行时的横摇姿态控制. 基于零航速减摇鳍的非线 性动态特性和海洋机器人横摇解耦模型, 提出具有主从结构的横摇减摇控制规律. 设计具有积分滑模面的变结构控 制规律, 估算系统期望横摇扶正力矩, 并进一步结合非线性跟踪控制理论和反馈线性化方法, 建立减摇鳍子系统模 型, 设计从属控制规律驱动减摇鳍产生实际横摇稳定力矩. 仿真结果和理论分析表明, 所设计的控制规律是稳定且有 效的.

     

主-从自治海上航行器有限时间同步运动控制

研究主-从自治海上航行器有限时间同步运动问题, 提出一种可实现主-从自治海上航行器的位置、姿态、线速度、角速度、线加速度和角加速度等运动状态有限时间同步的连续状态反馈控制方法. 首先, 通过建立主、从自治海上航行器的动力学模型, 给出了主-从同步运动控制方案; 然后, 采用齐次系统有限时间稳定性理论, 为从自治海上航行器设计了一种连续状态反馈控制器, 以及在该控制器下实现主-从自治海上航行器有限时间同步运动的充分性判据, 并通过实例仿真进行了验证.     

仿真系统中的时钟同步算法

研究当前仿真系统中的时钟同步问题和网络时间协议（NTP）。在NTP的基础上通过引入“主从服务器”模式、客户端时间推进和事件注册机制,实现一种适用于分布式仿真系统的、具有较高精度的软件时钟同步算法,给出同步系统的设计和实验方案。根据对实验数据的分析,验证该算法是一种简单有效的高精度时钟同步算法。     

基于两步控制策略的混沌系统全局有限时间同步

本文研究了无刷直流电机(brushless direct current motor,BLDCM)混沌系统的全局有限时间同步问题.利用混沌吸引子的有界性,提出了两步控制策略.首先不施加控制,让主–从混沌系统各自的轨迹收敛到各自的吸引子中,并估计了吸引子的界和收敛时间;再对收敛到吸引子的从系统施加状态误差反馈控制,根据有限时间稳定性理论,得出该控制器在满足一定条件时,两个相同的混沌系统可以快速达到有限时间同步.这种方法在主从系统的初始值相差很大的情况下可以大大减少控制成本,并且可以并估计同步时间.文章最后用仿真结果验证了所得判据的可行性和有效性.     

基于主动滑模控制的一类不确定混沌系统的同步

讨论了一类不确定混沌系统的同步问题。基于主动控制思想,提出了一种新的主动滑模控制策略,使得从任意初始条件出发的不确定混沌系统在有限时间内趋近滑模面;通过一种新颖的虚拟反馈控制,得到了设计鲁棒滑模面的一个充分条件,较好地实现了响应系统与驱动系统的完全同步,确保了不确定混沌系统同步的鲁棒稳定性。该控制器适用于一般的混沌系统。以Lü混沌系统为例进行了仿真验证,仿真结果表明,该控制方法可以实现较快的混沌同步,且同步的鲁棒稳定性良好。     

Reliable synchronization of nonlinear chaotic systems

This article addresses the reliable synchronization problem for a general class of chaotic systems. By combining the Lyapunov stability theory with the linear matrix inequality (LMI) optimization technique, a reliable feedback controller is established to guarantee synchronization between the master and slave chaotic systems even though some control component (actuator) failures occur. Finally, an illustrative example is provided to demonstrate the effectiveness of the results developed in this paper.     

A generalized function projective synchronization scheme for uncertain chaotic systems subject to input nonlinearities

In this paper, a modified generalized function projective synchronization scheme for a class of master–slave chaotic systems subject to dynamic disturbances and input nonlinearities (dead-zone and sector nonlinearities) is investigated. This synchronization system can be seen as a generalization of many existing projective synchronization schemes (namely the function projective synchronization, the modified projective synchronization and so on), in the sense that the master system has a scaling function matrix and the slave system has a scaling factor matrix. To practically achieve this generalized function synchronization, an adaptive fuzzy variable-structure control system is designed. The fuzzy systems are used to appropriately approximate the uncertain nonlinear functions. A Lyapunov approach is employed to prove the boundedness of all signals of the closed-loop control system as well as the exponential convergence of the synchronization errors to an adjustable region. Simulations results are presented to illustrate the effectiveness of the proposed generalized function PS scheme.     

基于输出反馈滑模控制的分数阶超混沌系统同步

以具有更大秘钥空间的分数阶超混沌系统为驱动系统和响应系统,利用具有实际应用意义的输出反馈滑模控制实现两个系统的同步.通过对同步误差系统方程进行结构分解,在辅助系统的基础上设计具有输出反馈特性的滑模控制律.在分数阶系统稳定性理论基础上利用MATLAB YALMIP工具箱对滑模参数进行整定,并利用分数阶Lyapunov稳定性定理证明了滑模控制律和自适应滑模控制律的稳定性.最后,数值仿真表明了本文方法的有效性和可行性.     

调整一类部分线性混沌系统输出的实用方案

利用部分线性混沌系统耦合后内在的投影同步性质对耦合响应系统的状态输出进行反馈控制，得到与驱动系统相位一致(或反相)，振幅成比例的混沌输出信号。该方案所需控制代价较小，为设计任意功率输出的混沌信号源提供了理论依据，在利用混沌电路系统进行保密通信方面有着极大的应用前景；仿真实例进一步表明了控制方案的有效性。     

A haptic interface for computer-integrated endoscopic surgery and training

Haptic feedback has the potential to provide superior performance in computer-integrated surgery and training. This paper discusses the design of a user interface that is capable of providing force feedback in all the degrees of freedom (DOFs) available during endoscopic surgery. Using the Jacobian matrix of the haptic interface and its singular values, methods are proposed for analysis and optimization of the interface performance with regard to the accuracy of force feedback, the range of applicable forces, and the accuracy of control. The haptic user interface is used with a sensorized slave robot to form a master–slave test-bed for studying haptic interaction in a minimally invasive environment. Using the master–slave test-bed, teleoperation experiments involving a single degree of freedom surgical task (palpation) are conducted. Different bilateral control methods are compared based on the transparency of the master–slave system in terms of transmitting the critical task-related information to the user in the context of soft-tissue surgical applications.     

A new multi-stable fractional-order four-dimensional system with self-excited and hidden chaotic attractors: Dynamic analysis and adaptive synchronization using a novel fuzzy adaptive sliding mode control method

Four-dimensional chaotic systems are a very interesting topic for researchers, given their special features. This paper presents a novel fractional-order four-dimensional chaotic system with self-excited and hidden attractors, which includes only one constant term. The proposed system presents the phenomenon of multi-stability, which means that two or more different dynamics are generated from different initial conditions. It is one of few published works in the last five years belonging to the aforementioned category. Using Lyapunov exponents, the chaotic behavior of the dynamical system is characterized, and the sensitivity of the system to initial conditions is determined. Also, systematic studies of the hidden chaotic behavior in the proposed system are performed using phase portraits and bifurcation transition diagrams. Moreover, a design technique of a new fuzzy adaptive sliding mode control (FASMC) for synchronization of the fractional-order systems has been offered. This control technique combines an adaptive regulation scheme and a fuzzy logic controller with conventional sliding mode control for the synchronization of fractional-order systems. Applying Lyapunov stability theorem, the proposed control technique ensures that the master and slave chaotic systems are synchronized in the presence of dynamic uncertainties and external disturbances. The proposed control technique not only provides high performance in the presence of the dynamic uncertainties and external disturbances, but also avoids the phenomenon of chattering. Simulation results have been presented to illustrate the effectiveness of the presented control scheme.