Design of a unidirectional joint with adjustable stiffness for energy efficient hopping leg

In this paper we introduced a unidirectional joint with adjustable stiffness (UJAS) for legged robot applications. It allowed the robotic leg to change dynamic property by tuning joint parameters. The joint was designed to provide large compliant motion range and sufficient energy storage capacity for passive gaits. In order to avoid undesired leg vibration during flying phase we brought about the unidirectional design with mechanical stops. Rotational stiffness output and the neutral position could be controlled independently allowing different leg configurations and dynamic features. The joint design was based on lever mechanism with torsion springs providing necessary compliant. It is experimentally tested that the joint design could provide different stiffness output characters and it has the potential to be used in legged robotic systems.