Quasistatic displacement self-sensing method for cantilevered piezoelectric actuators

Abstract

Piezoelectric meso- and microactuator systems required for manipulation or assembly of microscale objects demand reliable force and/or displacement information. Available sensors are prone to dimension restrictions or precision limitation. Self-sensing method, based on the electric charge measurement, may represent a solution in terms of cost-effectiveness and integration, the actuator performing simultaneously as its own sensor. This paper presents a self-sensing method dedicated to free uni- and bimorph piezocantilevers but can also be adapted to other piezoactuator types. The integrated electric current, used to convert the charge, can be compensated against piezoelectric material nonlinearities to provide accurate displacement information. The advantages relative to existing self-sensing methods consist in the ability to keep this displacement information for long-term periods (more than a thousand seconds) and in the reduction in signal noise. After introductive issues related to the method the base principle allowing the estimation of tip displacement is presented. Then, the identification procedure of the estimator parameters is depicted and representative experimental results are shown. Finally, a series of aspects related to electronic circuits are discussed, useful for successful system implementation.

Sensorless Position Control For Piezoelectric Actuators Using A Hybrid Position Observer

“…However, in practice, this approach poses a number of challenges. The main problem is associated with the bridge balancing since it employs a similar capacitor as the piezoelectric capacitance where the accurate measurement of the piezoelectric capacitance is difficult [32], [33]. Also, the nonlinear capacitance behavior is hard to achieve with linear capacitors, which may cause errors in sensing signals.…”

“…However, this also faces a challenge with charge drift due to offset currents. Ivan et al presented a simplified current integrator circuit (modified charge amplifier) to eliminate the charge drift for quasi-static applications [33]. However, this requires additional circuitry.…”

“…The major contribution in this research is a hybrid position observer (HPO) that combines two separate sensorless position measurements into a single high quality position estimate. The first position measurement uses the well documented linear relationship between charge and position [12], [21], [26], [33], and [36] which provides a highly dynamic position signal which unfortunately suffers from drift due to charge leakage. The second position estimate is obtained from a recently published relationship between effective actuator capacitance and position [35], [37].…”

Piezoelectric self-sensing technique for tweezer style end-effector

“…[7] but the method relies on charge amps to sense induced charge and is therefore poorly suited to static [9] measurements. The method proposed in [8] uses a modified charge amp as a current integrator and is capable of taking static measurements. However, the method in [8] is reliant on high quality components and is sensitive to changes in ambient temperature.…”

“…The method proposed in [8] uses a modified charge amp as a current integrator and is capable of taking static measurements. However, the method in [8] is reliant on high quality components and is sensitive to changes in ambient temperature. The method proposed in this paper utilizes a new set of equations reliant only on induced current and applied voltage to the piezoelectric element, reducing the components required for the self-sensing circuit to a single resistor.…”