Control of Active Microvibration Isolation Equipment by Consideration of the Air Pressure Characteristics in a Tube

Abstract

The range of applications using microvibration isolation equipment is being extended to devices for which the influence of vibration had not previously been considered. As a representative example, the application of active microvibration isolation equipment using an air spring actuator, suitable for MRI and NMR that operate in a strong magnetic field, is examined. In order to be used in a strong magnetic field, the active microvibration isolation equipment needs to have an actuator made from a nonmagnetic material. The servo valve that controls the air pressure in the actuator, however, must be installed away from the strong magnetic field since it cannot be fabricated from a nonmagnetic material. This necessitates the use of a long air supply tube to connect the servo valve to the actuator. Since this long tube affects the actuator characteristics, adequate vibration isolation performance cannot be attained with a controller designed using the conventional equipment model. In this study, a new equipment model is proposed by analyzing the characteristics of the active microvibration isolation equipment, and the control system is designed for the model using the model matching technique. The equipment model and control technique are validated by simulation and experiment.