Development of a Charge Estimator for Piezoelectric Actuators: A Radial Basis Function Approach

Development of a Charge Estimator for Piezoelectric Actuators: A Radial Basis Function Approach

Morteza Mohammadzaheri (Sultan Qaboos University, Muscat, Oman), Mohammadreza Emadi (Sultan Qaboos University, Muscat, Oman), Mojtaba Ghodsi (Portsmouth University, Portsmouth, UK), Issam M. Bahadur (Sultan Qaboos University, Muscat, Oman), Musaab Zarog (Sultan Qaboos University, Muscat, Oman) and Ashraf Saleem (Sultan Qaboos University, Muscat, Oman)
DOI: 10.4018/IJAIML.2020010103
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Abstract

Charge of a piezoelectric actuator is proportional to its displacement for a wide area of operating. Hence, a charge estimator can estimate displacement for such actuators. However, existing charge estimators take a sizable portion of the excitation voltage, i.e. voltage drop. Digital charge estimators have presented the smallest voltage drop. This article first investigates digital charge estimators and suggests a design guideline to (i) maximise accuracy and (ii) minimise the voltage drop. Digital charge estimators have a sensing resistor; an estimator with a constant resistance is shown to violate the design guideline; while, all existing digital charge estimators use one or a few intuitively chosen resistors. That is, existing estimators witness unnecessarily large inaccuracy and/or voltage drop. This research develops charge estimators with varying resistors, fulfilling the design guideline. Several methods are tested to estimates the sensing resistance based on operating conditions, and radial basis function networks models excel in terms of accuracy.
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Digital Charge Estimators

Figure 1 is a schematic of a digital charge estimator, used in this research. The estimator comprises of (i) a digital part, within the computer, (ii) an I/O card including analogue to digital (A/D) and digital to analogue (A/D) units, and (iii) analogue parts including the actuator, a voltage amplifier and a sensing resistor.

Figure 1.

A schematic of the experimental setup used in this research

IJAIML.2020010103.f01

VS, the voltage across the sensing resistor, is called the ‘sensing voltage’. VS is almost proportional to the current passing the actuator, iP, and most of iP passes through the grounded sensing resistor, RS:

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