Implementing a Vision-Based Collision Avoidance Algorithm on a UR3 Robot

Collaborative robotics implies the possibility for robots and humans to cooperate to perform a common task. A fundamental element to make collaboration possible is to ensure the safety of the human operators. In this paper a collision avoidance algorithm designed for a robotic redundant task is presented. This algorithm permits the robot to avoid collisions with obstacles (e.g. human operators) and in the same time to achieve the planned task when possible. The algorithm was tested with a UR3 robot of Universal Robots company, considering only tool centre point (TCP) position in order to obtain kinematic redundancy. The robot is controlled by an external PC that communicates with the controller of the robot via Ethernet network. The communication and control algorithms are written in the Matlab environment. The PC-UR communication functions permit to send joint velocities commands from the PC to the controller of the robot and feedback data from the UR to the PC. Control functions estimate the distances between an obstacle (whose position was acquired by a system of motion capture) and the robot and calculate the needed joints velocities to avoid any collision. The functions developed in Matlab will be explained in detail. Results of the experimental tests conducted to verify the effectiveness of the collision avoidance system are reported.