Comparison of charge estimators for piezoelectric actuators

This article deals with charge estimators for piezoelectric actuators. Two most recent/effective types of these estimators employ either a sensing capacitor (type I in this paper) or a sensing resistor (type II); the latter (and the newer) one is widely called digital charge estimator. There are experimental results in the literature indicating that, with the same waste of voltage, significantly higher amount of charge can be estimated with a type II estimator compared to a type I one; thus, the superiority of type II estimators has been professed. In order to re-assess this conclusion, this paper even-handedly compares type I and II estimators through analytical modelling and experimentation. The results show that types II estimators only have an insubstantial advantage in estimating higher amount of charge, if both type I and II estimators are designed pertinently. On the other hand, the resistance of type II estimators needs to tuned to deal with different excitation frequencies. This research concludes that capacitor-based charge estimators of piezoelectric actuators, with proper design and implementation, can be still the right solution for many problems despite the claims in the literature in the last decade.