Analysis and modeling of a proportional directional valve with nonlinear solenoid

To explain the influence of the nonlinear characteristic of a proportional directional valve with double solenoids, a dynamic model with a nonlinear performance in current-force-displacement of double solenoids proportional valve is presented. Despite the analyzing of nonlinear characteristic of the solenoids, the valve spool modeling, the orifice area and the dynamic model of the valve are also presented. The simulation model is set in MATLAB and a test rig is built for the dynamic performance test. At last, the comparison in sine wave and dynamic response of the simulation and the experiments are made. A big distortion occurs near zero spool position because the nonlinear characteristic is mainly manifested when the solenoid current is small. And it is mainly induced by the nonlinear characteristic of the solenoids and the direction switch motion of spool. The output in simulation is almost coincided with that of experimental result. That means the proposed modeling method of solenoids and valve is valid and effective. Some advanced control theories and methods can be applied simultaneously.