Modelling of a linear proportional electromagnetic actuator and possibilities of sensorless plunger position estimation

In flow control and in hydraulic systems used in automotive industry, e.g. brakes or automatic transmission units, one of the basic controlling problems is the precise adjustment of oil (fluid) pressure. As an electromechanical actuator, switching and linear variable solenoids are widely used in such applications. In this paper, a magnetic valve is analyzed in details. The main features of the system are highlighted and a proper solenoid model is intended to be established as well. Reliability and cost-efficiency are key requirements for actuators in the field of automotive engineering. For this purpose, sensorless position estimation for linear translational valve actuators is also proposed in this paper. According to this principle, the plunger position could be predicted from the magnetic valve's electrical impedance by using its transducer characteristics during excitation. As a great advantage, an external position or pressure transducer becomes unnecessary thus saving additional costs and further improving system robustness. This paper also presents and studies two different methods for sensorless position prediction which can be implemented under pulse width modulated drive conditions.