MEMS Accelerometer Proof-Mass Locking for Bunker Void Detection
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Solution Overview
Problem
Current MEMS accelerometers face challenges in accurately detecting and differentiating voids and hardened barriers within dense structural layers due to noisy signals from rapid projectile encounters, requiring sophisticated and costly computational hardware, and are prone to damage from high-G shock loading, limiting their precision and reliability in military applications.
Innovation Solution
A novel MEMS accelerometer design with a proof-mass locking mechanism that allows for high sensitivity and minimal settling time, combined with a piezoelectric sensor for reliable multiple-impact event detection, enabling accurate void counting and thickness measurement without complex computational hardware, and capable of withstanding high-G shock loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size of the moving proof-mass is reduced to withstand high-G shock loading, then the device can survive impact with hardened barriers, but the sensitivity and measurement precision are reduced
Solution Approach 1:
The device segments the sensing function into two independent sensors: a piezoelectric sensor for detecting high-G shock events (survivability) and a MEMS accelerometer for precise acceleration measurement (precision). This segmentation allows each sensor to be optimized for its specific function without compromise
Solution Approach 2:
The piezoelectric sensor acts as an intermediary that detects the shock event and triggers the locking mechanism, which then protects the MEMS accelerometer. The piezoelectric sensor mediates between the harsh external environment and the sensitive measurement device
2Measurement precision
If conventional accelerometers are used to detect voids between dense structural layers, then void detection is possible, but the settling time is too long to accurately measure the brief impact duration
Solution Approach 1:
The locking mechanism is pre-positioned and ready to engage immediately upon detecting a shock event. By preparing the protection mechanism in advance, the system can instantly protect the MEMS accelerometer during high-G impacts, enabling accurate measurement of brief void transit times without settling time delays
Solution Approach 2:
The system dynamically switches between two operational states: normal measurement mode with full MEMS accelerometer sensitivity, and protected mode during high-G shock events. This dynamic adaptation allows the system to maintain measurement capability across vastly different acceleration conditions
3Measurement precision
If sophisticated computational hardware and software are used to extract information from noisy accelerometer signals, then void and barrier information can be extracted, but the device size, power consumption, and cost increase
Solution Approach 1:
The solution extracts and removes the noisy high-G shock events from the signal processing chain by using a dedicated piezoelectric sensor for this function. This allows the MEMS accelerometer to focus only on measuring the quieter void transit phases, eliminating the need for complex signal processing algorithms to separate void signals from shock noise
Solution Approach 2:
The piezoelectric sensor performs preliminary detection of shock events and triggers the locking mechanism before the MEMS accelerometer is exposed to damaging G-forces. This preliminary action protects the primary sensor and simplifies subsequent signal processing
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 provides highly sensitive and reliable void sensing and counting capabilities with negligible settling time, enabling precise measurement of void lengths and hardened bunker layer thickness, and differentiates between voids and barriers with improved robustness and reduced costs.
Implementation Method 1
a piezoelectric sensor for reliable multiple-impact event detection
Implementation Method 2
Acceleration event detection and differential sensory devices and methods... MEMS accelerometers with their relatively long settling time produce very noisy signals
Data Source
AI summary
A method for detecting hardened bunkers within a target, the method including: producing a first output from a sensor fired to travel through the hardened bunkers, the first output being different from a second output when the sensor travels in a void between the hardened bunkers or encounters other objects outside of the hardened bunkers; and determining one or more of the number of hardened bunkers, a thickness of the hardened bunkers and a strength of the hardened bunkers based on the first and second outputs of the sensor over time. The sensor can include one of a piezoelectric generator for producing a voltage output and a circuit input by the voltage output or an accelerometer having a locking member for locking a proof mass during periods of impact with the one or more hardened bunkers.