Within this work a model of a 6 DOF (degree-of-freedom) vibration isolation system with semi-active control, using magnetorheological (MR) technology, is investigated. Parallel platform mechanisms are ideal candidates for 6 DOF positioning and vibration isolation. While active and passive vibration control have been extensively used in parallel platforms, a 6 DOF parallel platform which utilizes semi-active vibration control has not received as much attention. The advantages of semi-active control include reduced cost by using a simpler actuator intended for only positioning, reduced power requirements, and improved stability. Within this work, the legs of a parallel platform model are investigated by implementing a two DOF Simulink model. Each leg of the platform is modeled as a two DOF system with a magnetorheological (MR) damper for adjustable damping.
A new way to perform vibration control on a single-degree-of-freedom system using a piezoelectric friction damper is developed. The damper consists of an actuator, which is based on a piezoelectric stack with a mechanical amplifying mechanism that provides symmetric forces within the isolator. The advantages of such an actuator are its high bandwidth, actuating response and its ability to operate in vacuum environments such as in space. The damper is constrained to move using an air bearing that produces a virtually ideal single-degree-of-freedom spring-mass system. Within this work, the actuating ability of the friction-based actuator is characterized. The relationship between the force generated by the actuator and the applied voltage was found to be linear. The maximum force generated by the friction damper in this study is 85 N for the specific friction pads used.