Experiments of a variable stiffness robot using shape memory gel

This paper proposes a variable stiffness robot using a shape memory gel (SMG). Variable stiffness robots are useful to handle uneven objects in uneven environments such as home and office. Variable stiffness of rigid-link robots can be realized using motor control. Most of these robots require expensive force sensors. Flexible mechanical parts enable robots to realize low stiffness at the end-effectors without force sensors. However, high stiffness is hard to be realized by the robots with flexible mechanical parts. We propose another method to realize the variable stiffness of the robot without force sensors. We use a cold SMG for a rigid link and a hot SMG for a flexible link. A temperature control system of the SMG is developed, and any SMG link can be used as both a rigid link and a flexible link. Experiments of the application using the system are performed to illustrate the validity of our proposed method.