MEMS Piezoelectric Accelerometer Built-in Self-Test
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Solution Overview
Problem
Piezoelectric accelerometers lack a built-in self-test capability, making it difficult to verify their functionality, especially in critical applications like aerospace, where mechanical deformation and signal relations can change over time and temperature, requiring a method to detect these changes effectively.
Innovation Solution
An accelerometer design incorporating two MEMS piezoelectric transducers, one for actuation and one for sensing, mechanically coupled to a substrate with a proofmass, allowing for built-in self-testing by generating and comparing electrical signals to determine the device's operational status, using low voltage actuation and sensing mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If bulk-mode piezoelectric accelerometers are used, then mechanical deformation sensing is achieved, but large actuation voltage is required to cause measurable deformations
Solution Approach 1:
The patent replaces bulk-mode piezoelectric transducers with MEMS piezoelectric transducers, substituting a mechanical system with a micro-scale system that operates at lower voltages. The MEMS transducers use piezoelectric material deposited on a diaphragm structure, enabling measurable deformations with modest actuation voltages while maintaining sensing capability through the same piezoelectric effect.
Solution Approach 2:
The patent changes the scale parameter from bulk-mode to micro-scale, and modifies the structural configuration from solid piezoelectric elements to thin-film deposited on diaphragms. This parameter change enables the system to achieve measurable deformations at lower voltages by utilizing the high surface-area-to-volume ratio and flexible support structure of MEMS devices.
2Reliability
If piezoelectric transducers are used without self-test capability, then device simplicity is maintained, but reliability cannot be verified in critical applications
Solution Approach 1:
The patent implements multi-functionality by enabling the piezoelectric transducer to serve both as an actuator (when voltage is applied to cause deformation) and as a sensor (when deformation generates voltage). This dual functionality allows the same device structure to perform both operation and self-testing, reducing overall system complexity while enabling reliability verification.
Solution Approach 2:
The patent enables self-service by allowing the accelerometer to test itself through its own piezoelectric elements. The device applies test voltages to its own transducers, measures the resulting deformations, and verifies its operational status without requiring external test equipment, thereby maintaining simplicity while achieving reliability verification.
3Temperature
If mechanical deformation relations change over time and temperature, then environmental adaptability is required, but measurement accuracy deteriorates
Solution Approach 1:
The patent implements feedback by continuously monitoring the electrical signals generated by the piezoelectric transducers during self-testing and comparing them against reference values. This feedback mechanism allows the system to detect drifts in mechanical deformation relations caused by temperature or aging, and can trigger calibration or compensation procedures to maintain measurement accuracy.
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
Enables reliable self-testing of piezoelectric accelerometers, ensuring their functionality before use, particularly in aerospace applications, by using MEMS piezoelectric transducers to induce and measure mechanical deformations, thus verifying the device's performance across varying conditions.
Implementation Method 1
a first MEMS piezoelectric transducer configured to induce a mechanical deformation of the elastically deformable coupling member in response to an electrical excitation signal received by the first MEMS piezoelectric transducer
Implementation Method 2
a second MEMS piezoelectric transducer electrically isolated from but mechanically coupled to the first piezoelectric transducer via the elastically deformable coupling member. The second MEMS piezoelectric transducer is configured to generate an electrical response signal in response to mechanical deformation of the elastically deformable coupling member
Implementation Method 3
an elastically deformable coupling member
Data Source
Figure 1A~1B
Figure 1C
Figure 2
AI summary
Apparatus and associated methods relate to an accelerometer (10, 40, 70) having first and second piezoelectric transducers (28a, 28b, 30a, 30b) that are electrically isolated but mechanically coupled one to another via a coupling member (14a, 14b, 44). The first piezoelectric transducer (28a, 28b) is configured to induce a mechanical deformation of the coupling member in response to an electrical excitation signal received by the first piezoelectric transducer. The second piezoelectric transducer (30a, 30b) is configured to generate an electrical response signal in response to mechanical deformation of the coupling member. The accelerometer has a self-test module (104) configured to generate the electrical excitation signal and to receive the electrical response signal. The self-test module (104) is further configured to generate a sensor test result based upon a comparison between the received electrical response signal and a reference signal. The self-test module (104) may advantageously detect changes in an excitation/response relation due to time and/or environmental conditions, for example.