A sensorless position estimator for a nonlinear solenoid actuator

The proportional solenoid is a variable reluctance actuator operating under trajectory or position control mode. Established sensorless position estimation methods for variable reluctance motors do not work on proportional solenoids due to its single phase structure, noncyclic electrical signals, unpredictable load variations and highly nonlinear model. In this paper, a novel method of estimating the position of a solenoid by indirect observation of incremental inductance in the excited coil is described. The method relies on accurate measurement of di/dt values. For this purpose, a novel hardware circuit which measures the di/dt values from PWM current waveform accurately and reliably is developed. The method is implemented on a DSP and the results are found to be satisfactory