Sensors And Actuators
Why Today’s Sensors and Actuators need Strongly Coupled Multiphysics Design.
VIA - Vibrating Inertial Accelerometer: Based on piezo-electricdetection of a Vibrating beam. - Courtesy ONERA.
Today’s sensors and actuators often involve multiple physical phenomena such as Capacitive –Electrostatics, Piezoresistivity, Piezoelectrity, Accoustics, Thermics, Peltier effects and ElectroMagnetics.
As components are increasingly scaled down (nanotechnology, MEMS), specific microscopicphysical phenomena assume greater importance (Electrostatic effects, Peltier). Furthermore the time constants of these physical phenomena have similar orders of magnitude (electrical, mechanicaland thermal effects). Classical design techniques performing sequentially coupled simulations of the different physical phenomena will yield poor accuracy. Not so with OOFELIE::Multiphysics, which can solve more than 4 of such phenomena in a single, strongly coupled simulation setup for optimal accuracy and convergence.
Piezo-resistive pressure sensor (top left), MEMS based gyrometer (top right),
APA piezoelectric based actuator (bottom left), MEMS based flow sensor (bottom right)
In the case of actuators, the analysis focuses mainly on the mechanical response due to an electrical loading and in the case of sensors, on the inverse phenomenon. The harmonic response of accelerometers and gyrometers enters in this class of problems.
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.
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 softMEMS 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.
Piezoresistive Pressure Sensor.
Piezoresistive Semiconductor material 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 build-in electronic components.
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)