In this paper, a novel approach for the application of dynamic safety zones based on the requirements of safety standards for collaborative robotics is presented. The aim of the proposed method is to verify the possibility of collision between robot and operator, by performing online intersection tests between bounding volumes surrounding the robot and those surrounding the human. This approach allows us to tackle the limitations that impair the contribution of the robot to the collaborative task due to the enforcement of excessively conservative safety constraints. Furthermore, stopping trajectories for the manipulator are computed online and implemented when a potential collision is detected. These trajectories are optimized to minimize the stopping time by considering the robot dynamics and the maximum torque bounds at the joints. The proposed approach is of simple implementation and requires low computational effort, allowing an online evaluation of the protective separation distance required by the technical specification. Experimental results on a collaborative sorting task show the feasibility of the proposed approach and a significant statistical reduction of the completion time with respect to the approach based on static safety zones.
