Techniques to synthesize Inherently Force Balanced Mechanisms

Abstract

In mechanisms and machines, elements' motions can generate reaction forces and moments on the base of the mechanism, which are called shaking forces and shaking moments. These induce vibrations of the base, which create noise, wear and fatigue problems and reduce the accuracy of the systems. Dynamic balancing is a solution to eliminate these reaction forces and moments by generally introducing additional counterweights and counter-rotating elements. Mechanisms having zero shaking forces and moments are called, respectively, force balanced and moment balanced. Dynamically balanced mechanisms are both force and moment balanced. Since the introduction of additional elements increases the total mass and inertia of the mechanisms, the method of inherent dynamic balancing aims at designing dynamically balanced mechanisms which do not include additional elements. By considering dynamic balance as a design principle, all the links contribute to both the motion and the balance of the mechanisms. These are called inherently dynamically balanced mechanisms and can be synthesized from inherently force balanced linkage architectures, which are based on principal vectors. However, the design of these architectures consists in parallelogram linkages which can potentially compromise the force balance when their links become collinear. In addition, links can overlap and represent a potential limitation in real applications. This thesis presents techniques which modify the linkage architectures and can prevent the potential issues related to their original design. The number of degrees of freedom can be reduced and specific motions can be created by constraining links’ rotations and translations. Moreover, parallelograms’ sizes can be modified and links can be replaced by machine elements like sliders, gears, belt and chain drives. It will be shown how force balance is maintained after having modified the linkage architectures.