Variable stiffness mechanism for human-friendly robots

We have developed a variable stiffness mechanism (VSM) for human-friendly robots to simultaneously meet safety and performance needs. The VSM has high stiffness in normal operation mode and has low stiffness in collision mode when the load applied to the joint exceeds a critical load, specified by the physical constraints of the joint structure and an actively controlled electro magnet. We have verified the safety of the VSM by simulations and experiments using the head injury criteria index.