Modal Analysis of Rigid Bodies Supported by Low Frequency Pneumatic Vibration Isolators

Classical techniques for determining accurate frequencies and modes of a rigid body supported by pneumatic vibration isolation mounts were deemed unsatisfactory. It was found that the isolator’s transfer functions were nonlinear and exhibited frequency dependent stiffness and damping characteristics. To overcome these shortcomings a computer model of the isolator’s frequency response was developed by curve fitting a Laplace polynomial to the experimentally derived transfer functions. By mathematically combining the isolator’s response characteristics with a variety of rigid bodies the total system’s performance under a number of laboratory configurations could be efficiently predicted.