MEMS Piezoelectric Resonant Accelerometer for Low-Cost, Wireless Detection

Abstract

Researchers at the University of Central Florida have designed a wireless sensor that can accurately detect and transmit an object's acceleration or vibration without using on-board (wired) power sources or batteries with little to no maintenance required. Most commercial sensors need batteries to operate which, in turn, limits their life spans. In contrast, the UCF device operates by using energy that it receives wirelessly, so it requires no regular maintenance and can operate at ultra-low power.

Smaller, lighter and cheaper to build than other wireless accelerometers, the UCF sensor can be placed on moving parts inside an engine, in rotating objects such as tires, and in other hard-to-reach places that require regular maintenance. The design also enables operation at most frequencies, based on the application. Additionally, the design enables manufacturers to assemble several separate sensors with multiple frequencies and independent measurements onto one substrate. In one example use, the device could enable hospitals or parents to monitor newborns who are at risk for sudden infant death syndrome (SIDS).

Technical Details

The UCF invention consists of a microelectromechanical system (MEMS) piezoelectric-based resonator coupled with a mechanically-variable capacitor that is directly connected to a dipole antenna or an oscillator circuit. The sensor receives energy from a nearby transceiver, and the reflected signal contains the resonance frequency of the resonator, which is a function of the acceleration of the sensor. When mounted on a moving object, the sensor detects and translates movements/accelerations into movements of a lumped mass that forms the moving electrode of the variable capacitor and results in a change of capacitance/impedance. The transceiver wirelessly monitors the shift of frequency, extracting acceleration/displacement.

The system achieves wireless sensing by transmitting a sinusoidal interrogation signal from the transceiver to the sensor and receiving/analyzing the reflected signal. Using the interrogation signal, the sensor antenna energizes the sensor, which can then operate without needing an external power source. When the frequency of the interrogation signal equals the resonance frequency of the MEMS resonator, maximum energy transfer occurs. Once the interrogation signal is turned off, the resonator operates at its natural resonance frequency, allowing it to transmit a decaying sinusoidal signal to the receiver antenna. When the antenna receives the signal, the system extracts the resonance frequency of the resonator using Fast Fourier Transform (FFT) analysis. The system then adjusts the frequency of the interrogation signal for the next reading accordingly, to energize the sensor efficiently.

Partnering Opportunity

The research team is looking for partners to develop the technology further for commercialization.

Benefit

Market Application