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Sensor-actuator integration and self-sensing techniques for space constrained piezoelectric driven micro-positioners

University of British Columbia

Piezoelectric actuators are commonly used in micro-positioning applications. However, they exhibit an inherent nonlinear relationship between their driving voltage and displacement, which is called hysteresis. To compensate for hysteresis, conventional control approaches use dedicated sensors that are often bulky and expensive. The main objective of this thesis is developing techniques to minimize the need for direct use of external sensors in micro-positioning work spaces. These techniques are categorized into two groups: 1- integrating actuators with dedicated sensors employed outside the actuators' work-space and 2- self-sensing, which is using an actuator simultaneously as a sensor. The first group consists of two techniques. The first technique moves the sensors from within a micro-positioning work-space to a location outside the work-space. The technique is experimentally validated, where about 1% average absolute errors are measured for both displacement and force. The second technique constructs strain gauges from top and bottom electrodes of a piezoelectric bender and uses them to measure the bender's tip displacement. The validation experiments show about 1% measurement error. The second group consists of three techniques. The first technique uses voltage and charge measurements of a piezoelectric actuator to estimate its displacement and force. The validation experiments show about 4% average absolute errors measured for both displacement and forces. The second technique refines the first technique by using a nonlinear capacitance and a novel exponential hysteresis operator. The experimental validations show about 2% and 3% average absolute errors for displacement and force respectively. The third technique is based on impedance measurement of a piezoelectric actuator. The presented technique measures the impedance at a mechanical resonance frequency and maps it to the displacement and force of the actuator. The experimental validation show about 3.7% and 2.4% average absolute errors for displacement force respectively. The presented techniques in this study will help future researchers design simple and economic micro-positioners with sensor-free work-spaces. The first group of the presented techniques is useful, when the design goal is to make compact micro-positioners with optimized work-spaces. The second group is useful, when dedicated sensors are unavailable due to work-space or financial restrictions.

Text

2019-10-09

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/71878

Mechanical Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/