Resonant Sensor Array for Airborne Hostile Fire Detection
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Solution Overview
Problem
Conventional systems for detecting small arms fire on airborne platforms like helicopters face challenges in accurately identifying the source of incoming projectiles due to high noise levels from the aircraft's operation, which saturates microphone arrays and makes it difficult to discern acoustic signals of interest.
Innovation Solution
A resonant sensor system comprising a piezo electric sensor attached to a plate designed to resonate with shockwaves from projectiles, generating electrical signals that are less affected by operational noise and wind noise, allowing for the detection and localization of small arms fire sources through a resonant sensor array providing 360-degree coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a microphone array is used to detect small arms fire, then acoustic signals can be captured, but the microphone array becomes saturated by high operational noise and wind noise from the helicopter
Solution Approach 1:
The patent changes the detection parameter from acoustic pressure (microphone) to mechanical vibration (piezoelectric sensor on resonant plate). This parameter transformation allows the system to detect shockwaves while being immune to acoustic noise saturation, as the piezoelectric sensor responds to mechanical deformation rather than acoustic pressure.
Solution Approach 2:
The patent replaces the acoustic detection system (microphone array) with a mechanical vibration detection system (piezoelectric sensor mounted on a resonant plate). This substitution enables direct mechanical coupling to the shockwave energy, bypassing the acoustic noise saturation problem that plagues microphone-based systems.
2Measurement precision
If omni-directional microphones are used to capture shockwaves and muzzle waves, then shooter location can be estimated, but the broadband nature makes the array susceptible to receiving all other sounds which distort the acoustic signals
Solution Approach 1:
The patent changes from broadband acoustic detection to narrowband mechanical vibration detection at a specific resonant frequency. The resonant plate is designed to vibrate at a particular frequency when struck by a shockwave, effectively filtering out other sounds and preventing signal distortion while maintaining shooter location estimation capability.
Solution Approach 2:
The patent employs mechanical vibration of a resonant plate at a specific natural frequency to detect shockwaves. When a projectile shockwave strikes the plate, it induces vibration at the plate's resonant frequency, which can be detected by the piezoelectric sensor. This resonant vibration approach selectively amplifies the shockwave signal while rejecting other acoustic disturbances.
3Measurement precision
If a network of sensors is used to detect shockwaves only, then shooter location certainty can be achieved, but maintaining the array in a fixed location with respect to the shooter is not feasible for a flying platform
Solution Approach 1:
The patent transitions from a static microphone array requiring fixed positioning to a dynamic resonant sensor system that maintains detection capability despite platform motion. The resonant plate's mechanical coupling and the piezoelectric sensor's response characteristics allow the system to accurately detect shockwaves and determine shooter location even when the helicopter is moving, eliminating the need for complex array positioning maintenance.
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 resonant sensor system effectively captures high-energy shockwaves while rejecting lower-energy operational and wind noise, enabling accurate determination of projectile trajectories and source locations, enhancing the pilot's ability to maneuver the helicopter out of harm's way and engage the enemy.
Implementation Method 1
A resonant sensor system comprising a piezo electric sensor attached to a plate designed to resonate with shockwaves from projectiles, generating electrical signals
Implementation Method 2
a plate designed to resonate with shockwaves from projectiles, generating electrical signals
Data Source
AI summary
Systems and methods are presented for detecting a direction of an incoming projectile and determining a source location of the projectile. One or more resonant sensors (comprising a plate, piezo electric sensor, etc.) can be arranged, where shockwaves from the projectile (e.g., shockwaves from a bullet travelling at supersonic speeds) are incident upon the plate and cause the plate to resonate. The resonance causes an electrical signal to be generated by the piezo electric sensor (e.g., a piezo electric film sensor), the greater the degree of resonance in the plate, the higher the magnitude of signal generated by the piezo electric sensor. By comparing the magnitude of the piezo electric signals across the array of resonant sensors it is possible to determine a trajectory of the projectile and hence a location of the source of the projectile. Acoustic waves can also be generated by muzzle waves.