Nonlinear bilateral control of teleoperators with transmission time-delays

In bilateral teleoperation systems (bilateral teleoperators), the local and remote robot ma- nipulators are connected with a communication channel that often involves long distances or imposes limited data transfer between the local and the remote site. Such situations can result in substantial delays between the time a command is introduced by the operator and the time the command is executed by the remote robot. This time-delay affects the overall stability of the system. Scattering-based schemes have provided a suitable solution for the instability effects caused by time-delays, and since its presentation, have dominated the field of teleoperators control. The dissertation's endeavors can be viewed as a twofold: 1) Provide a first insight to the unification of the stability analysis for teleoperators with time- delays, 2) Prove that simple Proportional (P) and Proportional-Derivative (PD) controllers can sta- bilize a nonlinear bilateral teleoperator regardless constant and variable time-delays, and without scattering. First, a general Lyapunov function candidate is proposed that can be slightly modi?ed for dif- ferent control schemes, ranging from constant to variable time-delays, with or without scattering transformation and with or without position tracking. Then, the dissertation provides suf?cient conditions for the stability of nonlinear teleopera- tors. It is proved that P, PD and Scattering-based controllers do stabilize the teleoperator under constant and variable time-delays, and moreover, position tracking is also achieved, issues that have been thought to be compromising objectives. The dissertation outlines the conditions under which velocities and position error of the nonlinear teleoperator are bounded and, using Liapunov-Krasovskii i and Liapunov-Razumikhin functionals together with Barbalat's Lemma, it is also proved that velocities and position error converge to zero if the human operator does not move the local manipulator and the remote manipulator does not interact with the environment. Simulations and experiments validate the control schemes in this dissertation. Some of the experiments have been performed using the Internet as communication channel between Urbana-Champaign, USA and Barcelona, Spain.