Multi-axis Semi-active Vibration Control using Magnetorheological Technology

Parallel platform mechanisms with six degrees-of-freedom (DOF) are ideal candidates for precision positioning applications. Many of the precision positioning applications are located in environments where multi degrees of vibrations exist. From a design perspective, it will be logical to have a parallel platform mechanism, which is inherently an ideal mechanism for precise positioning, to provide vibration isolation at the same time. While passive vibration control and active vibration control have been extensively used in parallel platforms, a six DOF parallel platform which uses semi-active vibration control has not received as much attention. 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 a six DOF parallel platform model is created. Each leg of the platform is modeled as a two DOF system with a coil-over magnetorheological (MR) damper for adjustable damping in series with an actuator used for positioning. The vibration isolation performance of the parallel platform mechanism and its positioning capability are quantified through simulations. Simulation results show that MR dampers are effective in six DOF vibration isolation applications when they are incorporated into parallel platform mechanisms.