Abstract
In pneumatic position and force control systems, nozzle-flapper type servo valves are usually used for the pressure control. This paper proposes a linear model for a 4-port nozzle-flapper type pneumatic servo valve, which also includes the influence of the flow force, by deriving it from a full nonlinear model. The proposed linear model had a better agreement with experimental dynamics response than the former one which neglects the flow force. Furthermore, the proposed model was applied to achieve the differential pressure control between two symmetrical control chambers. A two degree-of-freedom (TDF) controller was designed based on the proposed model. The experiment results showed that differential pressure controllability could be improved for the reference input tracking and disturbance restraining by using the proposed model.
