Compliant Robotic Structures

Abstract

Elephant trunks are versatile and strong. Their mechanical design may therefore be used as a source of ideas for the design of versatile, strong robotic manipulators. In this paper a mathematical model of an elephant trunk lifting a weight is developed based on assumptions parallel to those used in the analysis of prestressed, linear, composite beams. Data on overall trunk geometry obtained during weight-lifting and data for the trunk muscle distribution at a cross section are used to calculate an apparent tangent modulus for the trunk tissue. During a change in trunk curvature for which the uniform component of longitudinal prestrain remains a constant 30 percent, a typical value for the apparent modulus is of the order of 10 6 N/m 2 . This study represents an initial step toward more refined analyses that rationally relate the loading, the overall trunk geometry and the muscle structure while satisfying equilibrium conditions. '.F, " A.q* " " v - '9 --4 -a -I I,g or 67 I* .,..