Simultaneous Control of Speed and Thrust of Hydraulic Actuator with Magnetorheological Fluids Valve Using Rectangular Pulse Wave Control

Magnetorheological fluids (MR Fluids) are suspensions which consist of soft magnetic particles and base liquid. By applying magnetic field, the particles make chain-like structure and rheological properties of the MR fluids show remarkable change. This characteristic is suitable for constructing control devises. In those devices, a MR fluids valve is one of promising devises. Because, the MR fluids valve can be controlled without mechanical mechanism, so the MR fluids valve has excellent reliability. In case of applying the MR fluids valve to controlling a hydraulic actuator, pressure (thrust) control is easy, but speed control is difficult. Because, the MR fluids have Bingham plastic characteristics, so pressure drop due to flow velocity is small compared to that due to yield shear stress. So, a rectangular pulse wave control based on pulse width modulation (PWM) control method taking account of yield shear stress of MR fluids and time constant of MR fluids valve is proposed and simultaneous control of speed and thrust of the hydraulic actuator with MR fluids valve is performed.