Piezoelectric Angular Rate Sensor with Perturbation Masses
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Solution Overview
Problem
Existing angular rate sensors face challenges in achieving high sensitivity and compactness due to limitations in piezoelectric material properties and structural design, leading to issues with external shock, vibrations, and reduced sensitivity in detecting Coriolis forces.
Innovation Solution
An angular rate sensor is developed using a semiconductor substrate with a piezoelectric film, featuring metallic dots as perturbation masses and a configuration that suppresses electric polarization in the z-direction, allowing for higher sensitivity and miniaturization through the use of electrodes and reflectors to generate and detect elastic acoustic waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single crystalline piezoelectric element is used to detect Coriolis force, then the sensor can provide angular rate information, but the sensor size cannot be sufficiently reduced and sensitivity is limited by material properties
Solution Approach 1:
The patent replaces the conventional single crystalline piezoelectric element with a thin film piezoelectric layer formed on a semiconductor substrate. This substitution enables the use of standard semiconductor fabrication techniques (sputtering, CVD, MOCVD) to create the piezoelectric structure, significantly reducing sensor size while maintaining detection capability through controlled film thickness and composition
Solution Approach 2:
The patent changes the physical parameters of the piezoelectric material by using thin film deposition techniques to create layers with controlled thickness (typically micrometers or less) and specific composition ratios. This allows optimization of both sensitivity (through appropriate thickness and piezoelectric coefficient) and miniaturization (through reduced overall dimension) simultaneously
2Volume of moving object
If the piezoelectric substrate is made compact, then the sensor size is reduced, but sensitivity to external shock and vibrations increases
Solution Approach 1:
The patent segments the piezoelectric structure into a thin film layer deposited on a separate semiconductor substrate. This segmentation allows the substrate to provide mechanical support and shock resistance while the thin film layer maintains the piezoelectric sensing function, effectively decoupling size reduction from increased vulnerability to external disturbances
Solution Approach 2:
The patent creates a composite structure combining a semiconductor substrate with a thin film piezoelectric layer. This composite material approach leverages the mechanical strength and shock resistance of the semiconductor substrate while maintaining the piezoelectric properties of the thin film, achieving both miniaturization and improved robustness against external shock and vibrations
3Measurement precision
If electric polarization in the z-direction is not suppressed, then the piezoelectric film can generate voltage in response to Coriolis force, but sensitivity is reduced due to polarization interference
Solution Approach 1:
The patent applies preliminary anti-action by configuring electrodes and applying voltages to pre-compensate for and suppress electric polarization in the z-direction before Coriolis force detection. This preliminary counteraction prevents polarization interference from degrading the sensitivity of Coriolis force measurement, ensuring accurate angular rate detection
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables high sensitivity and compactness, allowing for precise detection of angular rates while reducing the size of the sensor, making it suitable for integration with external driving circuits and production using very-large-scale integrated circuits (VLSI) technology.
Implementation Method 1
converting the Coriolis force into a voltage due to a piezoelectric effect
Implementation Method 2
a driving IDT for causing an elastic acoustic wave in the piezoelectric film in an response to externally applied driving voltage
Implementation Method 3
detecting IDTs for detecting a second standing wave generated by a Coriolis force acting on the metallic dots which vibrate
Data Source
AI summary
An angular rate sensor comprises a piezoelectric film having a first and a second surfaces forming an x-y plane and utilizes a perturbation mass coherently vibrating elastic acoustic waves on which a Coriolis force acts when the angular rate sensor undergoes a rotary motion about an x-direction. A first elastic acoustic wave is excited in the piezoelectric film by a driving transducer and a second elastic acoustic wave generated by the Coriolis force proportional to an angular rate of the rotary motion of the angular rate sensor itself is detected by the detecting transducer. The angular rate sensor further comprises at least a first electrode disposed on the first surface of the piezoelectric film for discharging a surface charge caused due to piezoelectric effect at the lower surface of the film in which the first elastic acoustic wave is excited.