Kinematic design optimization of improved branched tendon mechanism using genetic algorithm

This paper presents the improved branched tendon mechanism by including additional design parameters to the original branched tendon design, and a kinematic design optimization technique for this mechanism using genetic algorithm. The significance of additional design parameters and the feature of improved branched tendon mechanism are also explained. Unlike traditional joint pulley-tendon mechanism that always has the same length of moment arm, the improved branched tendon mechanism uses special tendon which is divided into two just before it is attached to the remote link. By optimizing these divided two different lengthes of tendons and other design parameters, creating various moment arm on a single joint with respect to the flexion angle of joint and limiting maximum moment arm to ensure all the tendons to be inside of the finger's outer frame are possible at the same time. Total 12 variables, 4 given and 8 independent, are used to represent the mechanism mathematically and the objective function is defined to maximize the moment arm throughout the flexion of the joint while not exceeding joint radius. Optimizing the kinematic model of improved branched tendon mechanism with genetic algorithm, it is possible to minimize the loss of the moment arm to 311% throughout the flexion. Meanwhile, overall actuation mechanism becomes much simple than traditional joint pulley-tendon mechanism.