Abstract
Piezo actuators have very desirable properties, such as a high stiffness and extreme position resolution, but suffer from electromechanical resonances that complicate their use in high-speed applications. These resonances can be minimized by using resistive or resistive-inductive damping.In this paper a comprehensive theory is presented which describes these piezo resonances, and the mechanism by which these resonances are minimized by adding electrical damping components. The theory is based on a purely electronic model, and uses an electrical-mechanical transformation to describe actual piezo displacements. Using this theory, an ‘optimal’ value of damping resistance is readily identified. This optimal resistance causes maximal damping of the primary resonance of the piezo. It is shown that damping with a combination of a resistor and an inductor can theoretically be even better.An optical displacement setup was developed, and frequency- and time-domain measurements were performed that validate the theory. The mechanical damping of the piezo actuator needs to be included in the theory to obtain a good fit with the electrical and mechanical behavior of an actual piezo actuator.
Highlights
Piezoelectric crystal actuators are used in many precision positioning applications
It is difficult to use piezos in high-speed applications, because they suffer from large electromechanical resonances [1]
In the current paper a compre hensive theory of electronic damping of piezo actuator resonances using R- and RL-(resistor-inductor) compensation is pre sented in purely electronic terms
Summary
Piezoelectric crystal actuators (piezos in short) are used in many precision positioning applications. Contrary to the ap proach followed in the current paper, they mathematically follow a mechanical resonance framework instead of the electronic descrip tion presented here Even though they do not consider piezos for actuation, only for passive damping, they obtain equations de scribing important features of piezo damping, such as peak shift, quality factor reduction, and the ‘saddle’ that is characteristic of resistor-inductor compensation. To use a piezo actuator with a mechanical resonance as low as possible, driving it with a voltage source including series resistance Ra close to the value required for maximum damping is highly desirable. Both acoustic and electronic damping can be combined to create a well-behaved system that can be further optimized by using control-based drive signals
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