Transparency Of Teleoperation System Research Articles

Stability analysis of the linear discrete teleoperation systems with stochastic sampling and data dropout

This paper addresses the stability conditions of the sampled-data teleoperation systems consisting continuous-time master, slave, operator, and environment with discrete-time controllers over general communication networks. The output signals of the slave and master robots are quantized with stochastic sampling periods which are modeled as being from a finite set. By applying an input-delay method, the probabilistic sampling system is converted into a continuous-time system including stochastic parameters in the system matrices. The main contribution of this paper is the derivation of the less conservative stability conditions for linear discrete teleoperation systems taking into account the challenges such as the stochastic sampling rate, constant time delay and the possibility of data packet dropout. The numbers of dropouts are driven by a finite state Markov chain. First, the problem of finding a lower bound on the maximum sampling period that preserves the stability is formulated. This problem is constructed as a convex optimization program in terms of linear matrix inequalities (LMI). Next, Lyapunov–Krasovskii based approaches are applied to propose sufficient conditions for stochastic and exponential stability of closed-loop sampled-data bilateral teleoperation system. The proposed criterion notifies the effect of sampling time on the stability-transparency trade-off and imposes bounds on the sampling time, control gains and the damping of robots. Neglecting this study undermines both the stability and transparency of teleoperation systems. Numerical simulation results are used to verify the proposed stability criteria and illustrate the effectiveness of the sampling architecture.

An Improved Wave-Variable Based Four-Channel Control Design in Bilateral Teleoperation System for Time-Delay Compensation

Good transparency performance (including position tracking and force feedback) is a significant issue for teleoperation control design. The four-channel control approach, which is based on the impedance matching between the master and slave, is an effective method to achieve the perfect transparency performance of teleoperation system. However, the obvious drawback of this design is that the time delay existing in the communication channel is neglected and thus the stability of this design under time delay cannot be guaranteed. Some passivity based control approaches such as wave-variable are developed to handle the stability problem of teleoperation system under time delay, and have been tried to add into four-channel control design. Though the stability under time delay is achieved for this kind of design, the transparency performance may largely decrease since the traditional wave-variable may essentially suffer some performance limitations (e.g., wave reflection). Thus, simultaneously realizing the stability and good transparency performance for four channel teleoperation system is still a challenging issue. In this paper, an improved wave-variable based four-channel control design is developed for bilateral teleoperation system to guarantee stability and further improve transparency performance. Under four channel control architecture, the passivity based time-delay compensator by the modified wave transform and the local force feedback are provided to compensate the distortion by reducing wave reflection and further enhance the stability and transparency of teleoperation system. The experiment is carried out, and the results show the great improvement of the proposed method to achieve the good transparency performance compared to the previous four-channel control designs.

Design and Implementation of Robust-Fixed Structure Controller for Telerobotic Systems

The controller design for bilateral teleoperation systems involves a delicate trade-off between performance and stability. To achieve high performance, high order robust controllers may not be feasible for real-time implementation because of hardware and computational limitations. The main purpose of this paper is to achieve stability and transparency in the presence of time delay in communication channel as well as model uncertainty. To address these problems, a novel robust fixed-structure controller is proposed for uncertain bilateral teleoperation systems. Here, the traditional conventional Proportional-Integral-Derivative (PID) controller is employed to achieve the requirements. The simplicity and straightforward design are the significant advantageous of the proposed method. Robust stability analysis of the proposed technique is also provided. Results demonstrate that the structure is effective in providing stability and transparency in teleoperation systems.