Real-time collision avoidance for position-controlled manipulators

A new approach to real-time collision avoidance for position-controlled conventional 6-DOF and dexterous 7-DOF arms is developed, and supportive experimental results are presented. The collision avoidance problem is formulated and solved as a position-based force control problem. Virtual forces representing the intrusion of the arm into the obstacle safety zone are computed in real time using a spring-damper model. These forces are then nullified by employing an outer force control loop which perturbs the Cartesian commands for the arm position control system. The approach is implemented and tested on a 7-DOF RRC arm and a set of experiments are conducted in the laboratory. These experiments demonstrate perturbations of the end-effector position and orientation, as well as the arm posture, in order to avoid impending collisions. The proposed approach is simple, computationally fast, requires minimal modification to the arm control system, and applies to whole-arm collision avoidance for 7-DOF arms.