Real-time Distance Query and Collision Avoidance for Point Clouds with Heavy-duty Redundant Manipulator

This paper presents a real-time method for generating joint trajectories for redundant manipulators with collision avoidance capability. The coordinated motion control system of the heavy-duty hydraulic manipulator resolves joint references so that a goal position can be reached in real-time without any collisions. The proposed method is able to detect and prevent different types of possible collisions, including self-collisions and collisions with obstacles. When the control system detects the risk of collision, the collision server searches the points where the collision is about to occur and calculates the shortest distance between the colliding objects. The collision server is used to retain static point clouds and to calculate the shortest distance between objects that are too close to each other. The point clouds on the server are kept up to date with the manipulators' joint sensors and laser scanner-based measurements. During coordinated motion control, the joint trajectories of the redundant manipulator are modified so that the collisions can be avoided, while at the same time, the trajectory of the end-effector maintains its initial trajectory if possible. Results are given for a 4-DOF redundant heavy-duty hydraulic manipulator to demonstrate the capability of this collision avoidance control system.