Reserve Piezoelectric Accelerometer for High-G Isolation and Low-G Precision
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Solution Overview
Problem
Existing accelerometers, particularly those using piezoelectric materials, struggle to simultaneously withstand high setback accelerations and accurately measure low accelerations required for munitions and other systems, lacking precision and durability in both high-G and low-G environments.
Innovation Solution
Design of 'reserve' linear and rotary accelerometers that isolate the proof-mass from the transducer during high-G events, engaging only when the acceleration level is within a prescribed range for precise measurement, using mechanisms like high-G support members and preloaded springs to ensure accurate low-G measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If compression type piezoelectric accelerometers are designed to measure low acceleration levels with high precision, then measurement precision is improved, but the device cannot withstand very high setback acceleration levels
Solution Approach 1:
The accelerometer is divided into two functional segments: a high-G accelerometer that withstands setback accelerations and a low-G accelerometer that provides precise measurement. These segments operate independently, with the high-G segment protecting the sensitive low-G segment during high acceleration events.
Solution Approach 2:
A mechanical coupling mechanism acts as an intermediary between the high-G and low-G accelerometers. This coupling transmits acceleration information from the high-G accelerometer to the low-G accelerometer only when appropriate, protecting the sensitive low-G sensor from damaging high acceleration forces while enabling it to measure low acceleration levels with high precision.
2Strength
If shear type piezoelectric accelerometers are designed to withstand high setback accelerations, then durability is improved, but measurement precision for low acceleration levels deteriorates
Solution Approach 1:
The system uses two separate accelerometer types segmented by function: a shear type piezoelectric accelerometer for high-G durability and a precision accelerometer for low-G measurement. Each type is optimized for its specific operational range without compromise.
Solution Approach 2:
The high-G and low-G accelerometers are combined into a single integrated system with a mechanical coupling mechanism. This merging allows the system to benefit from both the durability of the shear type accelerometer and the precision of the low-G accelerometer simultaneously.
3Measurement precision
If bending type piezoelectric elements are used to increase sensitivity, then sensitivity is improved, but the device becomes sensitive to temperature transients
Solution Approach 1:
The temperature sensitivity problem is extracted and isolated to the high-G accelerometer segment, which is designed to withstand such environmental variations. The low-G accelerometer segment, which requires temperature stability for precision measurement, is protected from temperature transients through the mechanical coupling design.
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 reserve accelerometers can withstand initial high-G accelerations without activation, ensuring high precision in measuring low-G accelerations with minimal cross-sensitivity to rotational accelerations, thus enhancing navigation and guidance systems in munitions and UAVs.
Implementation Method 1
seismic mass(es) and piezoelectric element(s) are arranged such that when the accelerometer is subjected to acceleration, the resulting inertial forces introduce strain in the piezoelectric element(s), which in turn produce electrical outputs by virtue of the piezoelectric effect
Implementation Method 2
the inertial force acting on the piezoelectric element generates electrical charges on the piezoelectric element and the charges are substantially proportional to the applied acceleration
Data Source
AI summary
An accelerometer including: a housing; a proof mass; a piezoelectric material; a support member for holding the proof mass a predetermined distance from the piezoelectric material, the proof mass being rotatably disposed relative to the housing and having a center of gravity offset from an axis of rotation of the support member; a first biasing material for biasing the proof mass towards the piezoelectric material and against the support member; and a second biasing material for biasing the proof mass at the predetermined distance from the piezoelectric material. When a level of acceleration of the proof mass is less than or equal to an acceleration level that is to be measured, the second biasing material is configured to force the support member to rotate to disengage the proof-mass and the first biasing material to move the proof-mass to contact the piezoelectric material.