Pressure Sensor Cavity for Aircraft Shooter Localization
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Solution Overview
Problem
Aircraft, particularly helicopters, pose a challenging environment for detecting shock waves and muzzle blasts due to turbulent airflow and mechanical vibrations, which interfere with acoustic sensors used in shooter localization systems.
Innovation Solution
A pressure sensor assembly with a domed surface and a porous member is designed to attenuate turbulent airflow-induced pressure fluctuations, while a flexible support and high acoustic impedance housing isolate the sensor from mechanical vibrations, maintaining an adequate signal-to-noise ratio for accurate projectile trajectory calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acoustic sensors are mounted on aircraft to detect shock waves and muzzle blasts, then shooter localization capability is improved, but measurement precision deteriorates due to turbulent airflow and mechanical vibrations interfering with sensor readings
Solution Approach 1:
A rigid housing with acoustic isolation features serves as an intermediary between the sensor and the turbulent airflow environment. The housing includes a rigid support member with a cavity that isolates the sensor from direct exposure to turbulence and vibrations, while still allowing acoustic waves to reach the sensor element through controlled pathways.
Solution Approach 2:
The patent employs a flexible support member that can deform to accommodate turbulent airflow patterns while maintaining sensor isolation. This flexible element allows the housing to flex in response to airflow variations without transmitting those variations directly to the sensor, thereby maintaining measurement precision while preserving localization capability.
2Device complexity
If the sensor is closely coupled to the aircraft surface for compact design, then device complexity is reduced, but measurement precision worsens due to direct exposure to mechanical vibrations and turbulent airflow
Solution Approach 1:
The sensor assembly employs a nested structure where the sensor element is housed within a rigid housing that contains a flexible support member and acoustic isolation features. This nested arrangement allows the sensor to be compact while maintaining isolation from external disturbances, achieving both reduced complexity and high measurement precision.
Solution Approach 2:
The patent introduces a spatial dimension for acoustic isolation by creating a cavity within the rigid housing that separates the sensor element from the external environment. This dimensional approach allows the sensor to be physically positioned close to the aircraft surface while maintaining acoustic isolation through the cavity structure, thereby improving signal-to-noise ratio without significantly increasing overall device complexity.
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 effectively suppresses noise from turbulent airflow and mechanical vibrations, enabling accurate detection of shock waves and muzzle blasts, thereby improving the accuracy of shooter localization systems on aircraft.
Implementation Method 1
a pressure fluctuation with a frequency of approximately 1 KHz induced by turbulent airflow across the domed surface is attenuated by at least a factor of 7 as the pressure fluctuation propagates across the distance
Implementation Method 2
flexible support and high acoustic impedance housing isolate the sensor from mechanical vibrations
Implementation Method 3
a pressure fluctuation with a frequency of approximately 1 KHz induced by turbulent airflow across the domed surface is attenuated by at least a factor of 7 as the pressure fluctuation propagates across the distance
Data Source
AI summary
A sensor assembly suitable for use in an airborne shooter localization system. The sensor assembly has a pressure sensor subassembly with a pressure transducer positioned to detect pressure variations associated with a shock wave from a passing projectile or the muzzle blast following the shock wave. To substantially increase the signal to noise ratio for measurements of the shock wave, the pressure sensor subassembly attenuates pressure fluctuations triggered by turbulent airflow over the surface of the subassembly more than it attenuates the shock wave. This preferential attenuation is provided by separating the pressure transducer from the surface of the sensor assembly by a cavity large enough that the pressure fluctuations are substantially attenuated as they propagate across the cavity. Additionally, features of a housing that holds the pressure sensor subassembly facilitate use on an aircraft. Those features include flexibility that allows the sensor assembly to conform to curved surfaces, a skin that provides resistance to environmental conditions and allows the sensor assembly to be attached with an adhesive, and a body region that provides high vibrational impedance to prevent low frequency mechanical vibrations from being coupled to the pressure transducer.