This article (1) proposes the use of a varying sensing resistor for digital charge estimators of piezoelectric actuators, (2) shows the usefulness of this proposal and (3) derives formulae to estimate the proposed varying sensing resistor. Digital charge estimators are used for charge-based precise position control of piezoelectric actuators. In existing digital charge estimators, an uncalculated resistor is used for a wide range of operating areas. Improper choice of the sensing resistor causes excessive drop in accuracy of charge estimation and/or in the driver voltage across the actuator. These issues are shown to nearly vanish with the use of proposed varying resistors.

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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.

Background: Electrothermal microactuators are very promising for wide range of Microelectromechanical Systems (MEMS) applications due to the low voltage requirement and large force produced. Method: A new optimized V-beam electrothermal micro actuator was implemented in variable optical attenuator. In this work, Particle Swarm Optimization (PSO) technique is proposed to design the Vshaped beam. Result: The approach has successfully improved both angular displacement & output force of the microactuator. Entropy generation rate was used as optimization criteria.