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.
Session Description: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 a 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 countermasses 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?
- Static balance
- The basic balancer
- The Anglepoise lamp; transformation rules
- Constant force mechanisms
- Adapting to varying payloads
- Static balance of compliant mechanisms
- Future directions
- 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
“The inventor of LEGO should have received the Nobel Peace Prize” – G. de Jong (father of Jan de Jong). How stuff moves fascinated Jan as a kid and it still does. In his current role as assistant professor, he translates design principles for precision mechanisms to other fields, such as medical devices and agro-food robotics. He received a master’s degree in biomedical engineering and a professional doctorate in engineering (PDEng) on the design of medical robot to apply transcranial magnetic stimulation during treadmill walking. Later he obtained his doctorate in the field of precision engineering on the dynamic balance of spatially moving robotic manipulators. His research interests include the kinematics and dynamics of (parallel) mechanisms, grippers, flexure mechanisms, screw theory. He is married, has two children. He practices a range of dynamic sports such as squash, ATB and futsal and still plays with LEGO.