A 2-DOF joint with coupled variable output stiffness

This paper presents a 2-degree-of-freedom (DOF) joint with coupled variable output stiffness that makes use of three actuators, i.e., two for the 2-D joint motions and one for the joint stiffness adjustment. By base-mounting the actuators and the variable stiffness module that contains the passive elastic elements, the design is compact and has low actuated inertia. Since the joint has coupled variable stiffness characteristic in the 2-DOF motions, the number of required actuators is reduced. The 2-DOF variable stiffness joint has been realized and experimentally tested