Report Number: CS-TR-94-1530
Institution: Stanford University, Department of Computer Science
Title: On Computing Multi-Arm Manipulation Trajectories
Author: Koga, Yoshihito
Date: October 1994
Abstract: This dissertation considers the manipulation task planning problem of automatically generating the trajectories for several cooperating robot arms to manipulate a movable object to a goal location among obstacles. The planner must reason that the robots may need to change their grasp of the object to complete the task, for example, by passing it from one arm to another. Furthermore, the computed velocities and accelerations of the arms must satisfy the limits of the actuators. Past work strongly suggests that solving this problem in a rigorous fashion is intractable. We address this problem in a practical two-phase approach. In step one, using a heuristic we compute a collision-free path for the robots and the movable object. For the case of multiple robot arms with many degrees of freedom, this step may fail to find the desired path even though it exists. Despite this limitation, experimental results of the implemented planner (for solving step one) show that it is efficient and reliable; for example, the planner is able to find complex manipulation motions for a system with seventy eight degrees of freedom. In step two, we then find the time-parameterization of the path such that the dynamic constraints on the robot are satisfied. In fact, we find the time-optimal solution for the given path. We show simulation results for various complex examples.