Ring APA actuator. The ring actuator is constituted by a metallic ring and 2 piezoelectric stacks. A potential is applied to the 2 piezoelectric stacks through the piece of metal at the centre. Due to the potential, the 2 piezoelectric stacks are contracted and induce a transversal displacement at the top of the actuator. The main goal of this type of actuator is the high precision positioning. In this section, the static mechanical response of an actuator is presented. It is made of a metallic external ring, a metallic central part and two piezoelectric stacks. A voltage is applied between the ring and the central part and it induces a contraction in piezoelectric stacks. A vertical movement can then be observed on the upper face of the actuator. The generated electrical potential in the actuator (left) and the resulting displacement field (right) Go back to applications list Capacitors in MEMS. Micromachined variable capacitors are used in RFMEMS, monolithic VCO's, accelerometers, gyroscopes and varactors. Critical to the succes of coupled analysis of structural - thermal - fluidic – electric-optic fields inside semiconductor components, is the integration inside widely used EDA designflows such CADENCE virtuoso, Tanner EDA, and EEsof ADS. Since it allows for co-simulation of the component inside the electrical circuit. Typical set up for a parallel plate capacitor. A sensing capacitor plate is suspended in parallel with a referenec plate. The sensing plate is able to move relative to the reference plate. Oofelie has a complete flow that enables to translate the ECAD layout in full 3D structures and to output to circuit simulation tools. To re-integrate the 3D electro-mechanic model into the circuit desing, we use the “Super Element modelling” capabilities in Oofelie. Reduced order modelling will reduce the complex 3D electro-mechanic model that includes interconnects, via’s and semiconductor layers to a verilogA or vhdl Super Element model to be included in the electric simulations. Go back to applications list Piezoresistive Pressure Sensor. Piezoresistive Semiconductor material can be printed on a flexible membrane structure. The stretching of this structure translates itself in a change in resistivity of the material. Measurement circuits can be co-simulated with in-build electronic components.

In a simple example we have simulated a piezoresitive film on a deforming beam. The results map the change in resitivity that can be observed at the area of highest deformation.

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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.

For more information consult The Onera Webpage (In French)

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.

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