Power-Based Safety Constraint for Redundant Robotic Manipulators

Abstract

A robot making or losing contact with its environment will experience a sudden change in its dynamics. This may cause instability, possibly causing the robot to harm itself and its environment. To prevent this while not placing overly restrictive constraints on the energy generated by the controller, we place a time-varying constraint on the system's power. The power limit varies with a heuristic measure of a desired task trajectory's stability, which is based on the largest Lyapunov exponent. When the trajectory is deemed unstable, the controller is forced to dissipate energy, while it is allowed to generate energy when the trajectory is stable. The constraint is included in a strict task-priority framework, allowing a redundant robotic platform to perform several tasks simultaneously while ensuring that the performance of the higher-priority tasks is not affected by the lower-priority tasks. The presented method is validated by simulation of an articulated intervention autonomous underwater vehicle (AIAUV).