Remote Control of Periodic Robot Motion

Abstract

Remote control of robots often leads to the presence of time delay in the information transmission of the signals in the control loop. Analytical methods are available for the calculation of the maximum critical time delays and control gains when stationary end positions of robots, or constant contact forces between actuators and environment are still stable. When the desired trajectory is periodic, or the desired contact force varies periodically, the non-linearities of the robotic structure take an important role even in the local stability behavior about the desired motion. The non-linear characteristics and the periodic path together lead to parametric excitation, i.e., the stiffness, damping and gain parameters may vary periodically in time. The stability behavior of these systems become intricate in the presence of great time delays. Stability charts are constructed which explain the stability properties of remote periodic force control.