This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination. IEEE TRANSACTIONS ON CYBERNETICS 1 Adaptive Neural Synchronization Control for Bilateral Teleoperation Systems With Time Delay and Backlash-Like Hysteresis Huanqing Wang, Peter Xiaoping Liu, Senior Member, IEEE, and Shichao Liu Abstract—This paper considers the master and slave synchronization control for bilateral teleoperation systems with time delay and backlash-like hysteresis. Based on radial basis functions neural networks’ approximation capabilities, two improved adaptive neural control approaches are developed. By Lyapunov stability analysis, the position and velocity tracking errors are guaranteed to converge to a small neighborhood of the origin. The contributions of this paper can be summarized as follows: 1) by using the matrix norm established using the weight vector of neural networks as the estimated parameters, two novel control schemes are developed and 2) the hysteresis inverse is not required in the proposed controllers. The simula- tions are performed, and the results show the effectiveness of the proposed method. Index Terms—Adaptive control, networked control system, nonlinear control, teleoperation, time-delay. I. I NTRODUCTION A TELEOPERATION system can extend the human-sensing and manipulative abilities to a remote environment and it generally contains five parts: human operator, two robotic manipulators including the master and the slave, communication channel, and the remote environment. In general, teleoperation falls into two main categories, i.e., unilateral and bilateral. The former one transmits only the master motion and/or force information to the slave site, and the later contains the motion and/or force information transmissions from the slave site to the master site. The bilateral teleoperation system has a wide range of applications in both traditional and potential areas such as operations in hazardous and less structured environments, space and undersea exploration, nuclear plants, drilling, etc. Because of its importance in both theory and application, Manuscript received August 11, 2016; revised November 19, 2016; accepted December 15, 2016. This work was supported in part by the National Natural Science Foundation of China under Grant 61304002 and Grant 61175072, and Grant 61403043. This paper was recommended by Associate Editor C. Hua. (Corresponding authors: Peter Xiaoping Liu; Huanqing Wang.) The authors are with the School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044, China, and also with the Department of Systems and Computer Engineering, Carleton University, Ottawa, ON K1S 5B6, Canada (e-mail: ndwhq@163.com; xpliu@sce.carleton.ca; lshchao@sce.carleton.ca). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TCYB.2016.2644656 the control design problem of bilateral teleoperation sys- tems has attracted tremendous attention in the past several decades and a variety of control approaches [1] have been developed for both theoretical interests and engineering applications. The control of bilateral teleoperation systems under the condition of time delays, for instance network-based teleoper- ation, is another challenging problem. The existence of time delay in the communication channel often degrades the sys- tem performance and even results in instability. Therefore, the effect of time-delay should be considered in the controller design of bilateral teleoperation systems, and there have been many interesting results obtained in [2]–[12] and the reference therein. The earlier results on stability of bilateral teleopera- tion systems with time delays are obtained via the passivity theory, for instance scattering transformation [2] and wave variables [3]. A new scattering approach is presented in [6] to improve the haptic feedback fidelity. In [10], a novel passive bilateral teleoperation control scheme applying a PD con- troller and a dissipative term is developed for teleoperators with time delays. Pan et al. [13] developed a new predic- tive approach for bilateral teleoperation with applications to drive-by-wire systems. In the above mentioned results, to achieve a satisfactory performance, the knowledge of dynamic models of teleoperation under consideration are assumed to be available precisely, which is not very realistic for many applications. It is well known that the uncertainties, with the forms of functional uncertainties, unmodeled dynamics and the distur- bances from the external environment, are inherent in the dynamical plants of master and slave robots. How to effec- tively deal with the complex uncertainties of bilateral teleop- erations is an active topic in the control field recently. Adaptive neural networks (or fuzzy) control approaches [14]–[37] have been proven to be useful tools for controlling highly non- linear, complex, and uncertain systems, and have also been extensively used in robotics control and applications [38]–[43]. In [41], an adaptive fuzzy synchronization control is pro- posed for the teleoperation system with stochastic time-delay. Yang et al. [42] presented a new finite-time fuzzy synchroniza- tion control method with the help of adaptive fuzzy approx- imation. More recently, the problem of neural network-based control is considered in [43] for networked trilateral teleopera- tion with geometrically unknown constraints. Nevertheless, the above intelligent control approaches require that the number 2168-2267 c  2017 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.