Abstract
In this paper, we proposed a stiffness changeable joint mechanism with a fail-safe function. The mechanism can change its stiffness to three states, elastic-solid-elastic, according to the safety and task situation. Each stiffness state can be switched by positioning a stiffness changing part moved by a rotary slider that is automatically return to its original state. The prototype of the joint mechanism was manufactured and its stiffness changeable function was confirmed. In addition, its impact force reduction function was confirmed through impact experiments.
