| Parallel platform mechanisms with 6 degrees-of-freedom (DOF) are ideal candidates for precision positioning applications. Compared to serial kinematic mechanisms, their 6 kinematic chains give them greater load carrying capacity, higher stiffness, the ability to remain stable in the unpowered configuration, and redundancy in motion. Many of the precision positioning applications are located in environments where certain degrees of disturbances exist. These disturbances in the form of vibrations degrade the performance of the sensitive instruments needed for precision positioning. Therefore, it is important to create a vibration-free environment to enable precision positioning. From a design perspective, it would 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.;Within this work, a model of a 6 DOF vibration isolation system with semi-active control, using magnetorheological (MR) technology, is investigated. While passive vibration control and active vibration control have been extensively used in parallel platforms, a 6 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 6 DOF parallel platform model is created. Each leg of the platform is modeled as a 2 DOF system with an MR damper for adjustable damping in parallel with a stiffness element and 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 6 DOF vibration isolation applications when they are incorporated into parallel platform mechanisms. |
