A design of bilateral teleoperation systems using composite adaptive controller

This paper presents a synchronization scheme of bilateral teleoperation systems using composite adaptive controller. To design a controller for bilateral teleoperation systems, all the parameters of the master and the slave robots need to be known. However, there exist parameter uncertainties in the robot manipulators. A composite adaptive controller is designed for convergence of states and parameters of the master and the slave robots in the presence of parameter uncertainties. Consequently, position and force tracking problems in free and contact motion are solved in a synchronized manner. Through a number of simulations, the superiority of the proposed method over existing works is illustrated. Furthermore, for the validation of utility of the proposed method in an actual embedded system, the algorithms are implemented and tested in FPGA-based hardware controller.     

Neural network-based synchronization of uncertain chaotic systems with unknown states

In this paper, synchronization of chaotic systems with unknown parameters and unmeasured states is investigated. Two nonidentical chaotic systems in the framework of a master and a slave are considered for synchronization. It is assumed that both systems have uncertain dynamics, and states of the slave system are not measured. To tackle this challenging synchronization problem, a novel neural network-based adaptive observer and an adaptive controller have been designed. Moreover, a neural network is utilized to approximate the unknown dynamics of the slave system. The proposed method imposes neither restrictive assumption nor constraint on the dynamics of the systems. Furthermore, the stability of the entire closed-loop system in the presence of the observer dynamics has been established. Finally, effectiveness of the proposed scheme is demonstrated via computer simulation.     

Control and synchronization of chaotic systems using a novel indirect model reference fuzzy controller

This paper presents a robust indirect model reference fuzzy control scheme for control and synchronization of chaotic nonlinear systems subject to uncertainties and external disturbances. The chaotic system with disturbance is modeled as a Takagi–Sugeno fuzzy system. Using a Lyapunov function, stable adaptation laws for the estimation of the parameters of the Takagi–Sugeno fuzzy model are derived as well as what the control signal should be to compensate for the uncertainties. The synchronization of chaotic systems is also considered in the paper. It is shown that by the use of an appropriate reference signal, it is possible to make the reference model follow the master chaotic system. Then, using the proposed model reference fuzzy controller, it is possible to force the slave to act as the reference system. In this way, the chaotic master and the slave systems are synchronized. It is shown that not only can the initial values of the master and the slave be different, but also there can be parametric differences between them. The proposed control scheme is simulated on the control and the synchronization of Duffing oscillators and Genesio–Tesi systems.     

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.     

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.     

基于神经网络误差修正的混沌控制与同步

针对混沌系统非线性强、多变量耦合等特点,提出了一种基于神经网络误差修正的自适应多变量混沌系统的广义预测控制算法,用线性广义预测控制器控制混沌系统,用神经网络对模型预测误差进行修正。算法中辩识过程模型用递推最小二乘法(RLS)、神经网络权值用Davidon最小二乘法(DLS)训练。这种算法对被控混沌系统的先验知识要求较少,无需知道被控系统的精确模型,数值仿真显示可实现混沌系统的宽范围控制与同步。     

Stability guaranteed teleoperation: an adaptive motion/force control approach

An adaptive motion/force controller is developed for unilateral or bilateral teleoperation systems. The method can be applied in both position and rate control modes, with arbitrary motion or force scaling. No acceleration measurements are required. Nonlinear rigid-body dynamics of the master and the slave robots are considered. A model of the flexible or rigid environment is incorporated into the dynamics of the slave, while a model of the human operator is incorporated into the dynamics of the master. The master and the slave are subject to independent adaptive motion/force controllers that assume parameter uncertainty bounds. Each parameter is independently updated within its known lower and upper bounds. The states of the master (slave) are sent to the slave (master) as motion/force tracking commands instead of control actions (efforts and/or flows). Under the modeling assumptions for the human operator and the environment, the proposed teleoperation control scheme is L/sub 2/ and L/sub /spl infin// stable in both free motion and flexible or rigid contact motion and is robust against time delays. The controlled master-slave system behaves essentially as a linearly damped free-floating mass. If the parameter estimates converge, the environment impedance and the impedance transmitted to the master differ only by a control-parameter dependent mass/damper term. Asymptotic motion (velocity/position) tracking and force tracking with zero steady-state error are achieved. Experimental results are presented in support of the analysis.     

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     

Motion synchronization of dual-cylinder pneumatic servo systems with integration of adaptive robust control and cross-coupling approach

We investigate motion synchronization of dual-cylinder pneumatic servo systems and develop an adaptive robust synchronization controller. The proposed controller incorporates the cross-coupling technology into the integrated direct/indirect adaptive robust control （DIARC） architecture by feeding back the coupled position errors, which are formed by the trajectory tracking errors of two cylinders and the synchronization error between them. The controller employs an online recursive least squares estimation algorithm to obtain accurate estimates of model parameters for reducing the extent of parametric uncertainties, and uses a robust control law to attenuate the effects of parameter estimation errors, unmodeled dynamics, and disturbances. Therefore, asymptotic convergence to zero of both trajectory tracking and synchronization errors can be guaranteed. Experimental results verify the effectiveness of the proposed controller.     

Robust synchronization of fractional-order unified chaotic systems via linear control

A new scheme for accomplishing synchronization between two fractional-order unified chaotic systems is proposed in this paper. The scheme does not require that the nonlinear dynamics of the synchronization error system must be eliminated. Moreover, the parameter of the systems does not have to be known. A controller is a linear feedback controller, which is simple in implementation. It is designed based on an LMI condition. The LMI condition guarantees that the synchronization between the slave system and the master system is achieved. Numerical simulations are performed to demonstrate the effectiveness of the proposed scheme.     

基于无偏LS-SVM的混沌系统的混合同步控制

为实现超混沌系统与混沌系统的混合同步控制,通过对主系统采样,获得训练样本数集,设计了从系统混合同步轨线的形式;采用无偏最小二乘支持向量机(LS-SVM)的方法,引入核函数,获得优化目标,根据优化目标,求出混合同步轨线,设计了控制器.以超混沌Lorenz-Stenflo系统为主系统,Chen混沌系统为从系统为例,基于Matlab进行数值仿真,验证了方法的有效性.     

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.     

Control and Synchronization Of A Class Of Uncertain Fractional Order Chaotic Systems Via Adaptive Backstepping Control

This paper presents the stabilization and synchronization problem of a class of fractional order chaotic systems with unknown parameters. A systematic step by step approach is explained to derive control results using an adaptive backstepping strategy. The analytically obtained control structure, derived by blending a systematic backstepping procedure with Mittag‐Leffler stability results, helps in obtaining the stability of a strict feedback‐like class of uncertain fractional order chaotic systems. The results are further extended to achieve synchronization of these systems in master–slave configuration. Thereafter, the methodology has been applied to two example systems, that is, chaotic Chua's circuit and Genesio‐Tesi system, which belong to addressed class, in order to show the application of results. Numerical simulation given at the end confirms the efficacy of the scheme presented here.     

基于PC和FPGA的运动控制系统

针对运动控制系统对高速度与高精度的要求,基于二次插补原理及最小偏差插补法,提出一种以PC机为主控制器、FPGA为从控制器的主从式运动控制系统的设计。主控制器的功能是对系统运行过程进行控制规划和粗插补;从控制器的功能是对加工进行精插补和执行速度控制。该系统在Matlab环境下进行了插补仿真,并在两轴数控雕刻床上进行了加工测试,验证了系统的可靠性与高精度。加工精度可达0.01 mm,为高精度、高速插补数控系统提供了有效的解决方案。     

一种鲁棒神经网络自适应控制策略及其应用

针对具有外部干扰等不确定因素的离散未知非线性受控对象,提出了一种鲁棒神经网络自适应控制策略.该策略运用自适应预测及带遗忘因子的递推最小二乘参数估计的思想,对神经网络的预报输出进行修正,利用鲁棒反馈控制器保证系统稳定性,并对控制信号的增量进行限幅以抑制突变大幅值干扰信号对系统的影响.将提出的控制方法应用于实验室级液面系统的仿真中,结果表明了该控制策略的有效性.     

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.      

Adaptive H_∞ Synchronization of Master-slave Systems with Mixed Time-varying Delays and Nonlinear Perturbations： An LMI Approach

This paper proposes an adaptive synchronization problem for the master and slave structure of linear systems with nonlinear perturbations and mixed time-varying delays comprising different discrete and distributed time delays. Using an appropriate Lyapunov-Krasovskii functional, some delay-dependent sufficient conditions and an adaptation law including the master-slave parameters are established for designing a delayed synchronization law in terms of linear matrix inequalities(LMIs). The time-varying controller guarantees the H _∞ synchronization of the two coupled master and slave systems regardless of their initial states. Particularly, it is shown that the synchronization speed can be controlled by adjusting the updated gain of the synchronization signal. Two numerical examples are given to demonstrate the effectiveness of the method.     

Near-minimum time control of flexible manipulators with a payload

In this paper near-minimum time controllers for coordinating flexible two-link robots carrying an object in a workspace are developed. Bang-bang control theory in conjunction with synchronization of execution time for each joint is used to derive the near-minimum lime controller. The near-minimum time control law is implemented for two distinct cases. One is for a single flexible robot grasping a payload white the other is for a master/slave configuration for the motion of two flexible robots and their load. Simulation results indicate the feasibility of the proposed schemes.     

遥操作旋转运动梁系统多目标优化控制研究

本文以旋转运动柔性梁为对象,采用基于胞映射的多目标优化方法进行遥操作系统双边控制研究.首先建立遥操作旋转运动柔性梁系统动力学方程,其次考虑信号传输时滞和系统主从端跟踪误差信号设计主端控制器和从端控制器,并利用Lyapunov稳定性理论获得保证闭环控制系统稳定的控制增益所需要满足的条件.由于满足稳定性条件并不意味着好的控制性能,最后利用基于胞映射的多目标优化方法进行优化控制设计,得到同时满足多个不同目标的控制增益的Pareto最优解集.仿真结果表明所获得的控制增益能够有效实现遥操作系统主从端的信号跟踪,并且操作者能够及时感受到从端环境的变化.     

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.