An evolutionary planner for near time-optimal collision-free motion of multi-arm robotic manipulators

This paper presents an evolutionary technique for open-loop minimum time planning of time-histories of control torques for robotic manipulators subject to box constraints on the control torques. Planning is carried out in joint space of the manipulator and the path is represented as a string of via-points connected by cubic polynomial splines. Repeated path modification is done by using the evolutionary algorithm to search for a collision-free time-optimal path. The time taken to traverse over a particular path is calculated by reducing the dynamic equations of motion over that path in terms of a path parameter and then calculating the time optimal-control over that path. Fitness function of the evolutionary algorithm to guide the search towards a solution which would give a collision-free time-optimal trajectory. Simulation results for 2-DOF and 3-DOF dual-arm systems are presented.