Balancing planar linkage mechanisms

Abstract

This thesis concerns the synthesis of counterweights for balancing the forces, moments and driving torque generated by planar linkage mechanisms. Part I reports the development of theory and an associated procedure by which multi-link, multi-degree-of-freedom planar linkage mechanisms may be fully force-balanced without reference to the kinematic equations of motion. The procedure includes rules to determine whether a particular linkage may be fully force-balanced, and if so how many counterweights are needed, together with a means of selecting an appropriate counterweight set. Part II reports the development and use of a general computer-based approach to synthesizing counterweights by means of numerical minimization. The illustrative computer program described can be used to improve the unbalanced forces, moment and/or driving torque of two types of planar linkages, a four-bar linkage and a particular Watt's six-bar chain. Quantitative criteria for evaluating the improvements are considered in some detail. The worth of the two approaches is examined theoretically and experimentally in the case of a particular Watt's six-bar chain. Part III contains the overall discussions on and conclusions to the work of this thesis, along with suggestions for further work.