Time Delay and Uncertainty Compensation in Bilateral Telerobotic Systems

Abstract

This chapter presents the state-of-art of the bilateral teleoperation field. It starts with a discusion of the early class of techniques, which are based on passivity and scattering theory. The main issue in bilateral telerobotic systems is the communication delay between the operator and the remote site (environment), which (if not treated) can lead the system to instability. The chapter continues by presenting the evolution of modern control techniques for stabilization and compensation of the time delay consequences. These techniques include predictive control, adaptive control, sliding-mode robust control, neural learning control, fuzzy control, and neurofuzzy control. Four case studies are reviewed that show what kind of results can be obtained.

Review of Control Methods for Upper Limb Telerehabilitation With Robotic Exoskeletons

“…First, there are system uncertainties [123] such as modeling uncertainties. There are also input uncertainties [80] such as unknown external disturbances and improperly measured, modeled [97], or time-varying human arm parameters. Accurate velocity and acceleration value estimates or measurements are required for many control methodswhich can be challenging to obtain due to noise in the signal.…”

“…Besides issues due to the communication medium, such as internet latency, other challenges for bilateral control systems are modeling complexities and modeling uncertainties [72], parameter variations [79], and uncertain disturbances such as friction or payload variations [80]. Furthermore, safety and reliability are of paramount concern in telerobotics with human operators in the loop, and even more so when dealing with humans on the slave side as well.…”

“…For example, in telesurgery, the slave robots are performing a task inside the human's body while in telerehabilitationwhen using exoskeletonsthe robotic device encapsulates part of the human body. There are many surveys and reviews covering teleoperation in the literature [64], [72]- [73], [80]- [83] and the following section summarizes succinctly the most commonly used control methods for telerobotic systems with more than one degree of freedom (n-DOF systems, n > 1).…”

Mobile Robots at Work

“…Web robots, that is, robots taking their inputs and sending their outputs using as infrastructure the World Wide Web, are used for teleoperation, education, and entertainment purposes [26,27]. These systems can be remotely controlled via the Internet from any site having a typical web browser that incorporates the human operator control interface [25].…”