A vision based online motion planning of robot manipulators

This article presents a vision based online system for the robust trajectory planning of robot manipulators. It uses a 3D vision system to determine the relative position of the objects to be engaged and the obstacle to avoid, and a novel obstacle avoidance procedure for manipulator motion planning. From intensity images acquired by a CCD camera mounted on the robot arm, the salient features are first accurately and robustly detected and then grouped. Through the correspondences between the feature groupings and the model features, the 3D poses of the objects and the obstacles are determined and confirmed by back-projection. Once these poses are determined, an online procedure, based on redundancy resolution, is used to achieve obstacle avoidance. The approach utilizes a null space vector to set properly the robot configuration, and a potential field method to guide the end-effector. By pseudoinverse perturbation it also prevents singular configurations and local minima. The feasibility and effectiveness of the system is demonstrated by an experiment with online engagement and transportation of objects posed inside an aluminium frame.