Development of an anthropomorphic robot finger : mechanical and kinematic aspects

Abstract

In this work, we report on the mechanical design and development, the kinematic analysis, and the simulation of a new dexterous robot finger. The robot finger design is based on that of the human counterpart in size, mechanical structure, and range of motion, and exhibits four distinct joint motions (one abduction/adduction or yaw motion, and three flexion/extension or pitch motions), as does the human finger. Three miniature DC motors with built-in encoders drive the yaw motion of the finger and the two innermost pitch joints. The finger therefore has three independent degrees of freedom. The outermost pitch joint of the finger is mechanically coupled to the middle joint, and the design allows for the variation of the ratio of angular speed between the two coupled joint motions. The motors are installed on the finger itself and on the adjoining section of palm, and the required torques at the joints are obtained through speed reduction transmission systems. An analytical study of the finger, including forward and inverse kinematics and differential kinematics analyses, static force analysis, and computation of joint velocity profiles for straight-line motion of the fingertip, has been carried out. The results of these analyses have been used to develop the control program for the finger, as well as a versatile simulation tool that can be used to optimise future designs of the finger. The simulation program has been validated by comparison to the results of tests carried out on the prototype finger. The ultimate aim of the work is to produce a dexterous robot hand to be used in a flexible manufacturing environment in industry or as a prosthetic device.