Vibration Suppression: Active and Passive Systems

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Machines are expected to vibrate as little as possible to avoid component fatigue/failure and in some cases, reduce user comfort level, for example, violent vibration of an automobile can lead to mechanical failure and driver discomfort. There are ways to avoid violent vibration such as running the machine away from critical speeds and suppressing vibration using active system or passive system. The latter can be implemented during design stage. Vibration problems are often found late in the process after a product is designed, prototyped, and tested, thus design changes are often needed.

Active vibration suppression systems are electronically controlled systems, which rely on a feedback circuit, consist of vibration measuring sensors such as accelerometers, a controller, and external power source. This allows high degree of vibration suppression to be achieved. An example of active vibration system is electronically controlled suspensions of cars. The system is able to adjust the stiffness and damping of the car according to road condition.

Passive vibration suppression systems are essentially systems which have a spring and damper. It does not require external power source or sensors to detect vibration. Dampers can be in form of viscoelastic materials such as rubber to dissipate kinetic energy. Passive systems are cheaper than active systems.

Machines have to have an acceptable vibration level during operation. Vibration level of machines, how much vibration a given machine can withstand, is addressed by the International Organization of Standard (ISO) as well as some national standard agencies. I will talk about acceptable vibration levels in general in the next article. 

Perpetual Industries’ Patented XYO Mechanical Balancer is able to reduce or eliminate vibration at the source by compensating for unbalance in the system. It is a passive system that does not require electronics.