Kinematic & Dynamic Analysis of the Human Upper Limb Using the Theory of Screws

TL;DR

This paper applies screw theory to analyze the kinematics and dynamics of the human upper limb and its exoskeleton, providing insights for control and movement prediction.

Contribution

It introduces a screw theory-based method for kinematic and dynamic analysis of the upper limb and exoskeleton, enhancing understanding of joint mechanics and control strategies.

Findings

Screw theory effectively models joint axes and motions.

Dynamic equations enable accurate control of exoskeletons.

Analysis distinguishes between natural limb and exoskeleton dynamics.

Abstract

Screw theory provides geometrical insight into the mechanics of rigid bodies. Screw axis is defined as the line coinciding with the joint axis. Line transformations in the form of a screw operator are used to determine the joint axes of a seven degree of freedom manipulator, representing the human upper limb. Multiplication of a unit screw axis with the joint angular velocity provides the joint twist. Instantaneous motion of a joint is the summation of the twists of the preceding joints and the joint twist itself. Inverse kinematics, velocities and accelerations are calculated using the screw Jacobian for a non-redundant six degree of freedom manipulator. Netwon and Euler dynamic equations are then utilized to solve for the forward and inverse dynamic problems. Dynamics of the upper limb and the upper limb combined with an exoskeleton are only different due to the additional mass and inertia of the exoskeleton. Dynamic equations are crucial for controlling the exoskeleton in position and force.