An Energy Approach to the Design of Single Degree of Freedom Gravity Balancers With Compliant Joints

Abstract

A gravity balancer is a mechanism that compensates the weight of a mass over a range of motion. When no friction is present, this gives an energy efficient mechanism and little effort is required to move an object. Conventional mechanisms have drawbacks due to the use of conventional rigid joints. Compliant joints do not have these disadvantages, can be made from fewer parts and can increase performance compared to rigid body joints. The goal of this paper is to develop a new method for the design of single degree of freedom gravity balancers where all the rigid joints are replaced with compliant joints. The method is based on connecting rigid links with compliant joints. With a constant potential energy as objective, the method allows new gravity balancers to be designed. The second goal is to construct a demonstrator as proof of principle. It can be concluded that for the first time a gravity balancers has been constructed where all the rigid joints are replaced with compliant joints. The gravity balancer had a peak moment reduction of 93%. The presented method is extensible and allows others to understand and to further develop gravity balancers with compliant joints for other applications.

Linkage Design for Gravity Balancing by Means of Non-zero Length Springs

“…This requires the use of special springs called "zero free length springs" [2]. The use of conventional linear springs leads to application of auxiliary mechanical systems, such as cable and pulley arrangements [3][4][5], linkages [6][7][8][9][10][11][12], cam mechanisms [7,13] or gear trains [14,15].…”