A Study of Calculation Method for Finger Joint Angular Displacement Based on the Finger Inverse Kinematics

A simple method for measuring and calculating the finger joint angular displacement was proposed to serve as the basis for designing dexterous hand and rehabilitation robot hand. The direct kinematics model and the inverse kinematics equation of the finger were established at the beginning of this paper. Then, the trajectory of the fingertip, from which the coordinates of the fingertip were extracted by using AutoCAD, was captured by camera. Finally, the trajectory coordinates of the fingertip were substituted into the inverse kinematics equations to solve the angular displacements of the proximal interphalangeal (PIP), distal interphalangeal (DIP) and metacarpophalangeal (MCP) joints. The calculating precision testing of the finger joint angular displacement needs to substitute the angular displacements calculated before into the direct kinematics equations of the finger to calculate the trajectory of the fingertip. Then, the average Euclidean distance between the calculated trajectory and the real trajectory was computed to test the calculating precision of the finger joint angular displacement. The average Euclidean distance of each fingers is less than 0.05mm, which proves the high calculating precision of the finger joint angular displacement and the efficiency of the method presented in this paper.