ISOLATION DESIGN FOR A FLEXIBLE SYSTEM

Abstract It has been commonly assumed that the corner or mount frequency in an isolator should be designed as low as possible. This is one result of using a single-degree-of-freedom (SDOF) system to model isolation systems. However, for systems that have flexible or non-rigid foundations, a design point for the mount frequency can occur between the modes of the base. By implementing this type of design, a strong interaction will exist between the modes. When isolator damping is included, whether done passively or actively, more then one mode can be attenuated by this new mount design. Therefore, the effects of the mount frequency on isolation designs are discussed as well as using both passive and active damping in the isolator. For active damping, three commonly used control methodologies are discussed: a proportional-plus-integral-plus-derivative (PID) controller, a linear quadratic Gaussian (LQG) regulator and a positive position feedback (PPF) controller.