Time-delayed Teleoperation Systems Research Articles

Intention-reflected predictive display for operability improvement of time-delayed teleoperation system

Robotic teleoperation is highly valued for its ability to remotely execute tasks that demand sophisticated human decision-making or that are intended to be carried out by human operators from a distance. However, when using the internet as a communication framework for teleoperation, high latency, and fluctuations make accurate positioning and time-dependent tasks difficult. To mitigate the negative effects of time delay, this paper proposes a teleoperation system that uses cross reality (XR) as a predictive display of the outcome of operators’ intended actions and develops a time-delay aware shared control to fulfill the intention. The system targets a liquid pouring task, wherein a white ring that indicates the intended height of the liquid surface is overlayed onto the beaker in a delayed camera image to close the visual feedback loop on the leader side. Simultaneously, the shared control automatically completes the pouring action to track the intended liquid height. The performance of the proposed system is validated based on liquid pouring experiments performed by human subjects. When compared with direct control, the absolute error rate decreased significantly for a constant round-trip time delay of 0.8 s and 1.2 s, similarly for a time-varying delay of 0.4 s and 0.8 s. Moreover, when the time-varying delay was 0.8 s, operators achieved significantly higher accuracy while maintaining comparable operation time. These results indicate that our proposed system improves operability even in the presence of time-varying delays in communication networks.

Adaptive control of time delay teleoperation system with uncertain dynamics.

A bilateral adaptive control method based on PEB control structure is designed for a class of time-delay force feedback teleoperation system without external interference and internal friction to study the uncertainty of dynamic parameters and time delay. The stability and tracking performances of the closed-loop constant time delay teleoperation system are analyzed by Lyapunov stability theory. Finally, the controller designed in this paper is successfully applied to the teleoperation system composed of a two-degree of freedom rotating manipulator as the master robot and the slave robot. The simulation is carried out in no operator and environment force or with operator and environment force. The adaptive bilateral control method's control performance is compared with that of the traditional time-delay teleoperation system. Finally, it is verified that the method has good control performance.

Control of Time Delay Force Feedback Teleoperation System With Finite Time Convergence.

In order to make the teleoperation system more practical, it is necessary to effectively control the tracking error convergence time of the teleoperation system. By combining the terminal sliding mode control method with the neural network adaptive control method, a bilateral continuous finite time adaptive terminal sliding mode control method is designed for the combined teleoperation system. The Lyapunov theory is used to analyze the stability of the closed-loop system, and the position tracking error is able to effectively converge in time. Finally, the effectiveness of the proposed control scheme is verified by MATLAB Simulink numerical simulation, and the numerical analysis of the results shows that the method has better system performance. Compared with the traditional two-sided control method (TPDC) of PD time-delay teleoperation system, the control method in this paper has good performance, improves stability, and makes steady-state errors smaller and better tracking.

Environment Recognition Based Shared Control for Operability Improvement of Time-Delayed Teleoperation System

Environment Recognition Based Shared Control for Operability Improvement of Time-Delayed Teleoperation System

Adaptive Neural Network Control of Time Delay Teleoperation System Based on Model Approximation.

A bilateral neural network adaptive controller is designed for a class of teleoperation systems with constant time delay, external disturbance and internal friction. The stability of the teleoperation force feedback system with constant communication channel delay and nonlinear, complex, and uncertain constant time delay is guaranteed, and its tracking performance is improved. In the controller design process, the neural network method is used to approximate the system model, and the unknown internal friction and external disturbance of the system are estimated by the adaptive method, so as to avoid the influence of nonlinear uncertainties on the system.

Adaptive-observer-based robust control for a time-delayed teleoperation system with scaled four-channel architecture

AbstractThis article presents an innovative adaptive-observer-based scaled four-channel (4-CH) control approach applying damping injection for nonlinear teleoperation systems, which unify the study of robotic dynamic uncertainties, operator/environment force acquirements and asymmetric time-varying delays in the same framework. First, a scaled 4-CH scheme with damping injection is developed to handle time-varying delay while guaranteeing the passivity of communication channels. Then, the improved extended active observer (IEAOB) is deployed to derive the operator/environment force while addressing the issues of measurement noise and model uncertainties. Furthermore, the system stability is analyzed by choosing Lyapunov functional. Finally, the proposed method is validated through simulation.

Energy-Optimized Consensus Formation Control for the Time-Delayed Bilateral Teleoperation System of UAVs

This paper proposes an energy-optimized consensus formation scheme for the time-delayed bilateral teleoperation system of multiple unmanned aerial vehicles (UAVs) in the obstructed environment. To deal with the asymmetric time-varying delays in aerial teleoperation, the local damping is independently distributed on both sides to enforce consensus formation and force tracking of the master haptic device and the slave UAVs. The stability of the time-delayed aerial teleoperation system is analyzed by the Lyapunov function. In addition, a flux-conserved force field is incorporated into the aerial teleoperation system to guarantee a collision-free consensus formation in the obstructed environment. Moreover, to reduce the communication complexity and energy dissipation of the formation, a top-down strategy of 3D optimal persistent graph is first proposed to optimize the formation topology. Under the optimized topology with environmental constraints, communication complexity and energy dissipation can be minimized while the rigid formation can be maintained and transformed persistently in the obstructed environment. Finally, the human-in-the-loop simulations are performed to validate the effectiveness of the proposed scheme.

Adaptive control for time-delay teleoperation systems with uncertain dynamics

In most teleoperation systems, the dynamics are uncertain and the communications exhibit time delays. In order to confront these problems, this paper reports a position error-based bilateral adaptive controller, in which the unknown operator dynamical parameters and environmental dynamical parameters are included in the unknown vector of the system to be evaluated, adaptive estimate laws are compensated by estimate errors and dissipation by time delays are compensated. By using Lyapunov-Krasovskii stability theorem, it is proved that both position errors and velocities of the teleoperation system asymptotically convergent to zero. Simulations are performed to compare the performance of the proposed controller with the traditional adaptive controller and to demonstrate the efficiency of the developed teleoperation control system.

Design of a New Impedance Controller for a Time Delay Teleoperation System

Bilateral teleoperation systems connected to computer networks such as the internet have to deal with varying time delays depending on several factors such as congestion, bandwidth, or distance. Such systems can easily become unstable due to irregular or varying time delays. A passivity concept has been used as the framework to solve the stability problem in bilateral control of teleoperation systems and we demonstrate in this paper how to recover both passivity and tracking performance using a novel control architecture that incorporates time varying gains into the transmission path, feedforward, and feedback position control. Simulation results for a single-degree of freedom master/ slave system are presented which demonstrates the performance of the resulting control architecture.

Key Technologies of Telepresence in Time-Delayed Teleoperation System: Review and Analysis

This paper reviews some key technologies and progress in the field of telepresence of teleoperation, meaning human sense and control of remote telerobot. Telepresence is the symbol of teleoperation, phenomenon of which enables the human to feel present at a remote location however a time-delay exits always in the teleoperation system. There are three means to conquer the effect: bilateral control method, virtual model based control and virtual reality technology. By optimizing control strategy user will get a perfect force or visual telepresence. Finally, opinions are given as to the further development of the field.

Stable and Transparent Time-Delayed Teleoperation by Direct Acceleration Waves

For time-delayed bilateral teleoperation systems, this paper presents a novel structure to considerably improve performance in terms of transparency and perception bandwidth, which are extremely low for passive systems, as well as force-position and velocity tracking on which delay control systems suffer both necessity for provision of identical initial conditions and drift problem. Performance improvement is carried out in three steps. The first step is the utilization of a four-channel wave-transmission structure that provides direct force and velocity feedbacks to each robot by asymmetric damping. Since the common dimension of wave variables is acceleration, the second step is the conversion of wave data into acceleration terms and the employment of acceleration control. The third step is the scaling of both the force- and position-based acceleration dimensions. Perception-bandwidth-limiting filters are used neither in wave space nor in control space. We showed the validity by experiments and superiority to previous systems by various comparative analyses.

Model-based Decentralized Control of Time-delay Teleoperation Systems

Recently, within a centralized control framework, the authors proposed a time-delay reduction method to achieve improved transparency in time-delay teleoperation. In this paper, a decentralized version of the controller is introduced that can further enhance the teleoperation transparency and robust stability by allowing the use of local delay-free measurements in local master/slave controllers. State/observation transformations are proposed that produce delay-free dynamics/measurements from the perspective of the local controllers at the master and slave stations. It is shown that the use of local suboptimal linear quadratic Gaussian master and slave controllers results in a delayed state perturbation term in the closed-loop dynamics. The stability of the system is then analyzed using a delay-dependent frequency sweeping test. The controllers employ a simple switching logic to handle large variations in the environment dynamics from free motion to rigid contact. The performance and robustness of the new decentralized controller are compared with those of the centralized controller using numerical analysis. Experimental results demonstrate the effectiveness of the proposed approach.

Analysis of absolute stability for time-delay teleoperation systems

In this paper, a new bilateral control algorithm based on absolute stability theory is put forward, which aims at the time-delay teleoperation system with force feedback from the slave directly. In the new control algorithm, the delay-dependent stability, instead of delay-independent stability, is taken as the aim of control design. It improves the transparency of the system at the price of unnecessary stability. With this algorithm, the time-delay teleoperation systems have good transparency and stability. A simulation system is established to verify the effect of this algorithm.

ROBUST BILATERAL TELEOPERATION CONTROL UNDER UNKNOWN CONSTANT TIME DELAY WITHOUT VELOCITY MEASUREMENTS

New technological advancements in the communication channel of time delay teleoperation systems have attracted lot of attention, which have produced recently new control schemes, under a variety of conditions, including unknown (either constant or time varying) time delay or parametric uncertainty. However, those require full access to the state of the master and slave robot. In this paper, a model free, exact differentiator, is used to estimate the full state under parametric uncertainty together with a chattering free, second order sliding mode controller to guarantee robust impedance tracking under constant, but unknown, time delay. Experimental results, that validate the predicted behavior, are presented and discussed.