Kinematic Modeling and Kinesiology Study of a Human Index Finger Based on a Tendon-Driven Articulated Manipulator With Disc-Cam Pulleys

A tendon-driven articulated manipulator with disc-cam pulleys is presented for the kinematic modeling and the motion analysis of a human index finger. Using the proposed model as a foundation, the driving forces of the tendons of human finger could be further evaluated and compared with the estimation from the EMG signals. The motivation of using such a tendon-driven articulated manipulator model to emulate the structure and functionality of a human finger is initiated by the similarities between these two systems, where the joint motions of the systems are both activated by the force transmission of tendons either by the base-driven actuators or the contraction of human muscles. However, the distinction between these two systems is that the extension/flexion motion of a human finger is coupled with the abduction/adduction motion due to the anatomical complexity of the expansion hood of a human finger, while the motion of a general articulated manipulator is not coupled. Moreover, since the shapes of the base and head of phalanges are irregular, the joints of a human finger cannot be simply treated as a perfect revolute joint. Hence, for the motion compatibility between the human finger and the articulated manipulator, the functionality of the expansion hood and the tendon system of a human index finger are identified and the joints are treated as revolute joints with non-circular pulleys. Based on the kinematic model and motion simulation of the finger-alike tendon-driven articulated manipulator is accomplished, and the prototyping model of the manipulator is constructed. Motion comparison between the models with the constant and non-constant moment arms is also implemented.