A new magneto-rheological fluid actuator with application to active motion control

A novel magneto-rheological fluid based actuator (MR actuator in short) is proposed for the micro level motion control application. The proposed MR actuator is working based on the principle of magnetic extension and contraction by the MR fluid sandwiched structure between the two electrode type coils. The key enabling concept in this work is to precisely control the biasing current of electrode-coil for achieving the desired displacement of the proposed actuator. The direction and amount of current input to the top and bottom electrode-coils decides the characteristics like contraction, extension and the force generated by the actuator, respectively. In order to undertake a proof-of-concept of the proposed actuator, a simple proportional-integral (PI) controller is designed and implemented in real time for the MR actuating system to control the desired displacement. The process parameters of the MR actuating system are obtained by applying a step input to the electrode- coils, and the PI controller are designed using internal model control (IMC) tuning rule. The experimental realization of the micro-level motion control is easily performed using the MR actuator. It is demonstrated from displacement tracking results that the proposed MR actuating system has a distinctive control characteristic in an active mode. Therefore, this salient control characteristic leads to wide and various applications, especially in micro electro mechanical systems (MEMS) devices fabrication.