Analytical modeling of anthropomorphic hand using simmechanics

Abstract

Anthropomorphic hands are currently generating significant amount of interest for their variety of use, such as bionic hands in active prostheses applications, robotic grippers for remote applications as well as assisting tremor free surgical operations. Modeling of a human hand is an intricate process due to complex shapes of fingers and phalanges flexibility of the muscles. Movement coordination of the finger imposes a control paradigm structure with the central nervous system. This study presents a model of hand with four fingers and thumb connected with palm for gripping action through control scheme. The model describes through the torque applied at the proximal-inter-phalange (PIP) which closes to the palm. This provides the rotation of a complete finger assembly and output are taken from the position of the tip of distal inter-phalange (DIP). An anthropomorphic hand which is made up of using micro-servo motors and gear assemblies, a feedback path from the DIP may not be able to provide a feasible solution. However, a rotation and angular velocity feedback from PIP will be useful as an encoder from motor as sensory measurements. This model has open loop model from input torques as well as feedback of rotation and angular velocities from PIP as well as performance objectives from DIP position. A simple simulation of PID control validates the controller design scheme in MATLAB / Simulink environment with SimMechanics for achieving 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> order model for each finger independently. The simulation results demonstrate well the applications of tools for analytical development of biologically inspired anthropomorphic hands.