Modeling and sensorless control of an electromagnetic valve actuator

This paper presents the modeling and control of an electromagnetic valve actuator. The model is nonlinear and takes into account secondary nonlinearities like hysteresis, saturation, bounce and mutual inductance. Experimental methods for identifying parameters of the model are presented. Sliding mode control is utilized to reduce the seating velocity of the plunger as it strikes the core housing. This reduces actuator noise due to the high impact velocity of the plunger. In order to eliminate the need for position and velocity sensors, a nonlinear observer is developed that only employs coil current measurement. The position estimate is used as feedback to track a desired trajectory. The control objective is to minimize energy consumption and to reduce the seating velocity, which should improve actuator fatigue life and reduce impact noise. Simulation and experimental results are presented for an actuator designed and built in our laboratory. The experimental results show very good agreement with the analytical model.