Models for piezoelectric sensor-actuator systems

The miniaturization trend in industry requires micro devices for handling and sensing in a micro environment. As the size of the handled objects decreases and their fragility increases, the demand for sensors with higher force sensitivity and resolution grows. Force measurement as a technical process is always the conversion of the quantity force into another measurable quantity. The most commonly used "transducing"-principle for force measurement is the conversion of force to elastic deformation i.e. mechanical strain. To yield a high sensitivity, the force has to induce a large strain, which makes the sensor very compliant. The biggest problem of the high compliance force sensors is that the concept works only for forces which are not position dependent (i.e. gravitational forces). To provide force measurement for highly position dependent forces, a system is needed that is very stiff but also very sensitive. The concept of choice is a force sensor system where the force induced deflection is actively compensated, e.g. by a piezo-electric actuator. This work describes the development of the analytical models for two kinds of piezo-electric sensors and actuators. In the first part, the direct-drive-actuators (e.g. stacked actuators) are discussed, and in the second part the models for beam shaped actuators are subject of investigation. The developed models represent a new modeling approach which is open to any geometrical variations and different boundary conditions. The suitability of the presented models for optimization is shown later in this work and a procedure for optimization is developed. In the last, part the function of the two considered systems is demonstrated experimentally. The concept of the direct-drive-system is demonstrated with a charge-sensing stacked actuator-sensor system. For the beam-shaped-actuator system, a 1-degree of freedom was set up. In these experiments strain gauges measured the force and the position.


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