The Modeling and Experimental Verification of a Servo-Proportional Valve

The present work deals with a method for the modeling of a three-way servo-proportional valve actuated by a proportional solenoid. The model incorporates the primary nonlinear phenomenon exist in the solenoid, such as the hysteresis, nonlinear inductance and counter-electromotive force. Two ways are employed to simplify the model for the purpose of controller design. Firstly, the relations of current supply vs. flux linkage and flux linkage vs. electromagnetic force under different displacements of armature are captured by curve fitting and interpolation, with the advantage of keeping the nonlinear characteristics. Then the linearization method around the null-position of the spool is implemented, where the solenoid is modeled as a 1-order system, and the body of valve is treated as mass-spring 2-order system. Then the test-bed for the identification of main parameters and verification of the model is designed. The parameters are obtained from the experimental results where the armature and spool are locked at different positions. Finally, the model is verified as the dynamic responses of current supply and displacement of spool obtained from the simulation model agree well with the experimental results when the armature and spool are unlocked.