Design of the Planar Compliant Five-bar Mechanism for Self-aligning Knee Exoskeleton

Most of the previous designs of wearable robot for lower extremities did not take into account the misalignment between the instantaneous center of rotation (ICR) of human knee joint with that of the exoskeleton, and misalignment will cause uncontrollable force on the attachment point, make malaise and affect the rotation of the human joint. Based on the five-bar mechanism, this study brings up a novel design of knee exoskeleton to alleviate even eliminate the misalignment. The mechanism introduces compliant joints between bars which provide adjustable stiffness and selective passive flexibility for exoskeletons with respect to the posture of human knee joint. Kinematic movement is presented, and according to which the stiffness matrix is exploited and validated to conform to the mechanism characteristics we anticipated.