Unbalance can be quite unpleasant. In this tutorial, we treat two related but distinct forms of balancing mechanisms and machines: static balance and dynamic balance. Both design principles aim to improve the mechanism’s performance by load cancelling; either cancel the static loads on the mechanism, or cancel the dynamic loads induced by the mechanism.
A statically balanced mechanism can move freely without apparent influence of gravity. This results in lamps, hospital equipment and bridges that seem to float and move with zero effort. In these statically balanced mechanisms, cleverly designed springs or counterweights counteract the pull of gravity (and other loads) and keep the mechanism upright. This principle is used in precision engineering to, for example reduce the required motor power and associated heat production, or to reduce the apparent stiffness of a mechanism and tune its natural frequency.
A dynamically balanced mechanism, on the other hand, is free of shaking moments and shaking forces, potentially leading to a vibration-free motion. The motion of the masses in a ‘normal’ mechanism induce counteractive forces and moments on the support frame, leading to vibrations and noise. These vibrations of the base reduce the accuracy at the end-effector and disrupt sensors and equipment in the vicinity. By a specific choice of the counter masses and kinematics, a mechatronic system may be designed in such a way that dynamic forces and moments cancel, leading to a reactionless, vibration-free system.
This tutorial treats the fundamentals, applications and state-of-the-art of these two balancing principles. By showing examples, it aims to provide an overview on static and dynamic balance. What are the pro’s and con’s? When to use and when not to use?
Topics: 1. Static balance - The basic balancer - The Anglepoise lamp; transformation rules - Constant force mechanisms - Adapting to varying payloads - Static balance of compliant mechanisms - Future directions
2. Dynamic balance - Difference between static and dynamic balance - Force balance vs moment balance - Balancing machines (axle, wheel and engines) - Balancing multi-DOF mechanisms - Balancing and flexibility; does dynamic balance goes off-balance? - Future directions
13 Oct 2020
35th Annual Meeting of the American Society for Precision Engineering, ASPE 2020