Energy-saving control of an unstable valve with a MR brake

In fluid power systems, excessive heat often causes solenoid failure. Heat, as well as useful power of a solenoid, is associated with the current. In this paper, we attempt to alleviate the requirement for the solenoid power, thus reducing the heat generation accordingly. The method we utilize to change the solenoid power requirement is based on unstable valves, which take advantage of fluid induced forces to achieve open loop instability. Previous studies have shown that for unstable valves, the electromagnetic actuator needs to absorb the power generated by the flow forces. Using the dual-solenoid actuator alone as a brake does not imply heat reduction. In this paper, we propose a new type of actuator in which a dual-solenoid actuator is mounted in series with a magneto-rheological (MR) brake. A nonlinear sliding mode optimal controller is then developed to achieve position tracking and energy-saving. Simulation verities that using the proposed actuator and control law, heat generated in the unstable valves can be reduced significantly.