The role of joint stiffness enhancing collision reaction performance of collaborative robot manipulators

For robots working in human environment, human safety is one of the most serious and important aspects to be considered. Appropriate intrinsic and / or functional safety design must be employed for collaborative robots in order to reduce the human injury risks through physical human-robot interaction. Above all the situations that such interactions are possible to occur, it is reported that clamping humans with robot and its environment is of great danger in a sense of human injury risks. We have conducted experiments and simulations that mimic clamping-human accident in some different situations varying robot's inertia, velocity, thickness of robot's soft cover and joint stiffness. Furthermore, some collision detection and reaction measures are implemented on the experimental system and their contributions to human safety were evaluated. From the results of these experiments and simulations, the joint stiffness was found to play an important role on human safety considerably affecting the performance of collision reaction.