A redundant rehabilitation robot with a variable stiffness mechanism

This paper presents a variable stiffness mechanism suitable for use in robotic rehabilitation. By inherently varying both the magnitude and direction of loading in the mechanism using a single input, a large variation in effective stiffness is achieved. Design and analysis of the variable stiffness mechanism are presented, along with an example illustrating performance capabilities. The paper goes on to present a serial robot for upper limb rehabilitation whose noteworthy characteristics are a degree of redundancy and variable stiffness in its four active degrees of freedom. These traits make the robot suitable for various rehabilitation tasks. The kinematic solution is derived, and simulations of two characteristic movements demonstrate how the variable stiffness and redundancy contribute to task performance.