Resistance Estimation in Solenoid Actuators by Considering Different Resistances in the PWM Paths

Abstract

The estimation of the resistance of solenoid actuators is important to reduce bias in model based control and estimation methods due to temperature changes. Under PWM operating conditions, the overall resistance the current encounters during the “on” and “off” periods of the PWM cycles can be different because of non idealities such as the resistance of wires, transistor’s junction etc. In this paper, methods are developed for estimating the resistance of solenoids that consider the difference between the resistances in the energizing paths. First, the steady-state PWM current waveform is considered. Then, methods are presented for the transient current waveforms. Thus, the resistance can be estimated in case of long transient periods due to changes in the control signal. Because solenoid actuators are usually implemented in embedded applications, the methods are optimized to meet the requirements of low complexity and computational load. Experimental results are also presented.