Active vs. Passive Vibration Isolation

Posted On: Monday, January 13, 2020

Active vs. Passive vibration isolation system performance

Active vs. passive vibration isolation, understanding the difference is critical to mitigating the impacts of vibration on equipment performance.  Passive isolation systems use the natural properties of a spring and a dampener to reduce vibration.  Active vibration isolation systems use a control system with integrated sensors and actuators, improving low-frequency performance.

Engineers use vibration isolation systems for many different applications in electron microscopy and semiconductor/display manufacturing.  Passive vibration isolation systems are widespread and have a diverse range of applications.  Passive isolation systems can be simple, such as the rubber feet underneath a vibrating pump, or be more complicated such as the shocks and struts on a car. Active vibration isolation systems, however, are intricate systems with highly specialized applications. Understanding the differences both in the implementation and performance of these two systems is critical to making sound decisions regarding your capital equipment.

Passive Vibraiton Isolation System Schematic

Passive Vibration Isolation Systems

A passive vibration isolation system consists of three components: an isolated mass (payload), a spring (K), and a damper (C), and they work as a harmonic oscillator. The payload and spring stiffness define the natural frequency of the isolation system. While the spring (isolator) reduces floor vibrations from being transmitted to the isolated payload, the damper eliminates the oscillation amplified within the isolation system.  Often, passive vibration isolation systems employ a pneumatic spring due to its low resonant frequency characteristics.  In many applications, pneumatic systems provide outstanding vibration isolation and damping.

Passive isolation systems are relatively inexpensive and are excellent at mitigating high-frequency vibration. However, their natural resonance is problematic in some applications where low-frequency vibration is problematic.  Besides the low-frequency resonance, passive vibration isolation systems have a longer settling time and are difficult to control.

Active Vibration Isolation Platform Schematic

 

Active Vibration Isolation Systems

Active vibration isolation systems consist of feedback and feed-forward control systems with integrated sensors and actuators. These systems isolate the most sensitive equipment from the extremely low-frequency vibration that passive isolation systems amplify at resonant frequencies. The sensors detect incoming vibration in all six degrees of freedom, and a digital controller processes the measured vibration data into digital signals. The controller then sends the signals to the actuators that cancel the vibrations by generating an equal and opposite force. High-resolution electron microscopes and precision manufacturing tools require active vibration isolation systems when low-frequency vibration is problematic.

 

Active vs. Passive Vibration Isolation

To learn more about the difference between active vs. passive vibration isolation systems, or to learn how VEC can help you mitigate vibration in your facility, contact us today!

vibration reduction for sensitive instruments