Vibrating Intertial Accelerometer.
Onera constructed a monolythic quartz sensor, Sensitive to orthogonal acceleration. This concept efficiently decouples the vibrating beam from the outside case through a decoupling framework. It permits to maximize the vibration quality factor of the beam, needed for frequency stability.
The whole device - including the sensor's package is simulated using Oofelie becasue of the need of strongly coupled Piezo-thermo-elastic modeling.
The resonating beam is activated through piezoelectrcity while thermo-elastic damping is critical for space (zero-gravity) and vacuum applications. At the same time thermal stresses influencing the frequency behavior need to be minimized.
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The device functionality is based on the piezoelectric actuation of a beam (see red arrow) and the consequent measurement of the frequency shift due to axial stresses exercised on this beam.
The importance of a high Quality factor for the device sentitivity. The Oofelie strongly couple piezo-thermo-elastic simulations give an excellent fit with the measurements.
We simulate the sensor's behavior within a To8 package, which enables us to
- Study the enegergy losses through the mounting parts
- Optimize the resonance quality
- Minimize the effectof thermal stresses on the resonance frequency.
Finally we optimze the accelerator's response together with it's measurement circuit. The measurement circuit is designed to lock into the transducers eigen-frequency for optimizal performance, however the transducer's original response (top left) does not enable this because the electric capacitance intoduced by the structure intoduces an unwanted phase-shift. By adding an electric compensation circuit and optimizing the electric parameters of this circuit, we are able to improve the total system performance (bottom right), cancelling the phase shift, while maintaining the quality factor.