Optimal Kinematic Design of the Link Lengths of a Hand Exoskeleton

Abstract This chapter presents the kinematic optimization of the link lengths of the second-generation robotic hand exoskeleton of the UCLA Bionics Lab to assist stroke victims in performing rehabilitation exercises during physical therapy. The device is based on a three-linkage base-to-distal topology for controlling the five human hand digits. Each of the robot linkages ends in a 3R planar serial mechanism to accommodate flexion/extension motions. The link lengths of each 3R mechanism determine the workspace, kinematic capabilities, and size of the device, and therefore must be selected carefully. The optimization method presented is based on the mechanism isotropy performance measure as well as the planar area occupied between the 3R mechanism and relevant digit. In addition, the optimization algorithm evaluates designs based on coverage of the in-plane workspace area and, optionally, the interference between the joints of the manipulator and the digit. The theoretical result is compared to a physically realized model of the manipulator.