Abstract: Inview of the fact that conventional rotary proportional solenoids are unable to work under high fluid pressure, a novel rotary proportional solenoid capable of withstanding high pressure is presented. The polarizing magnetomotive forces generated by the permanent magnets are superimposed on the control magnetomotive forces, which are provided by the excitation currents flowing in the coils, to make the solenoid produce output torques (angular displacements) proportional to the excitation currents. The static torque characteristics and the amplitude frequency response characteristics are analyzed based on magnetic circuit analyses, magnetic field simulations and experiments. The simulations and measured results agree well and show that the rotary proportional solenoid has advantages of compact structure, no zero dead-zone, large output torques (maximum output torques ±0.65 N•m) and fast response (bandwidth about 190 Hz). With positive magnetic stiffness, high level of linearity (non-linearity less than 3%) and hysteresis less than 4.5%, the solenoid is suitable for driving the rotary servo valve directly.

Key words: Bi-directional driving, Magnetic circuit, Magnetic stiffness, Rotary proportional solenoid, Withstanding high pressure