08-11-2016, 03:05 PM
1466946121-ModelingandCharacterizationofTunablePiezoelectricActuator.pdf (Size: 510.18 KB / Downloads: 12)
Abstract— The hub of this paper to study the effect resonance frequency of piezoelectric MEMS. The modeling and
characterization of piezoelectric resonator using COMSOL Multiphysics. An investigative relation was developed based
on the shift in resonance frequency caused by the addition of a different material on the PZT. The theoretical analysis is
done with a user-friendly SPICE Circuit Editor interface constructed for easy introduction of design dimensions , material
parameter values and force signal stimuli. A piezoelectic device can actutate a cantniliver beam simply by applying an AC
voltage over the device.The cantilever beam itself has resonant modes that causes peaks in vibrations when the frequency
of applied voltage passes the resonance frequency of each mode .If another piezoelectric device is attached to the
cantilever, it is possible to tune the resonance by connecting that device to a passive external circuit.In this model,
different materials are used for designing o tunable actuator. We have observed the graph between displacement and
frequency of various materials. And the best material found from analysis is Lead Zirconate Titanate. This model
investigates how the external circuit influence the resonance peaks of cantilever beam and also improve the quality.
INTRODUCTION
MEMS is Micro-Electro-Mechanical System Technology is a capable technology for low-loss, high linearity
applications[1]-[4]. Piezoelectrically transduced micro resonator have become attractive research topic in ultra-mass
detector, bio-sensor, RF filter and high freq micro oscillator. Compared with elctrostatically actuated and sensed
capacitive silicon micro resonator, piezoelectrically transduced microresonator exhibits better power handling capacity
than capacitive type since low driving-voltage of several hundreds of millivolts is enough for resonator actuation ,which
facilitates the integration of microresonators with CMOS signal processing circuits. The main advantage of MEMS
resonator lies in possible integration onto silicon based IC platforms.
High-mode vibration can improve mass detect sensitivity of a resonant cantilever under atmospheric pressure by
suppressing the air damping effect [5].High mode vibration can be successfully achieved by the proposed structure, and
greater Q-factor can be obtained as expected for the pursuit of better mass detection sensitivity. However, the measured
Q-factors are still lower than the theoretical calculations. High mode vibration results in large vibration amplitude at the
position where cantilever and actuator connects. It leads to large vibration amplitude in PZT actuator, which in turn
induces additional energy dissipation as analyzed in reference[6]. Besides, large vibration amplitude at the actuation hinge
also trends to decrease Qsup, because energy may dissipate easily through substrate.
Quality Factor (Q) is one of the most important characteristics of MEMS resonators, especially if they are used to build sensors based
on frequency monitoring. The corresponding frequency resolution, and thus the system's sensitivity, is then indeed directly linked to
Q. The higher the value of Q, the higher the micro-system's performance. These MEMS resonators are indeed found in many
applications were a high sensitivity is needed: inertial sensors, mass sensors. To get high Q-values, these micro-systems generally rely
on the use of vacuum packaging, air damping being an important limitation to the quality factor [13].
Another possibility to get high Q-values could be to externally increase the quality factor. An interesting technique to artificially
improve the quality factor is called parametric amplification and consists in modulating the structure's stiffness at a harmonic
frequency of the device's resonant frequency. This modulation results in an increase of the oscillation amplitude at the device's
resonant frequency and thus an increase of Q.
II. THEORITICAL CONSIDERATION
The actuator consists of a thin bar of silicon with an active piezoelectric device below the bar, and a second passive
piezoelectric device on top as shown in Figure1. These devices are located at one end of the actuator. The piezoelectric
material is lead zirconate titanate (PZT), and each of the devices has two electrical connections to an external circuit,
realized with the Floating potential boundary condition of the Piezo Plane Strain application mode.
MODLING OF PIEZOELECTRIC ACTUATOR
Because the fundamental resonance mode is the mode of deformation with maximum displacement and the relevant mode
shapes were modeled. The results related to the various displacement with various piezoelectric material even the material
of cantilever beam is fixed, which is single crystal Silicon as shown below. Thus the deformation show by displacement
by varying the frequency
CONCLUSION
Here we concluded that all the material i.e. Quartz, Zinc Oxide, Aluminum Nitride, Lead Zirconate Titanate (PZT-5A), shows
various changes in displacement when frequency changes respectively. Quartz is not used due to its low piezoelectric cofficient, but it
is nevertheless an intresting material of its high Q factor. But the tunnig with external circuit is possible in the lead Zirconate Titanate
by varying the inductance and also frequency will shifted towards the lower side. In order to get desired frequency range, by changing
the parameter value in the solver parameter. The analysis is done by using a high end software COMSOL Multiphysics. One important
parameter is to able to predict the Q factor of the structure and have accurate design guidelines to minimize the energy losses.