Piezoelectric Sensor Damping for Hard-Target Impact Discrimination
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Solution Overview
Problem
Piezoelectric sensors in detonating projectiles are overly sensitive, leading to potential unintentional detonation due to high voltage peaks from soft objects like brushwood, which can be misinterpreted as impacts on hard targets, especially at small angles, causing safety concerns.
Innovation Solution
A piezoelectric sensor arrangement with a damping layer that attenuates frequencies above a predetermined cutoff frequency, allowing integration of voltage signals over time to differentiate between low-energy soft object impacts and high-energy hard target impacts, setting a threshold for safe detonation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoelectric sensor sensitivity is increased to detect hard targets, then detection capability is improved, but false detection from soft objects increases
Solution Approach 1:
The patent segments the detection process by using multiple piezoelectric sensors positioned at different locations and orientations within the projectile. Each sensor detects different aspects of the impact, and the combined signal analysis enables discrimination between soft and hard targets, resolving the contradiction between sensitivity and false detection.
Solution Approach 2:
The patent changes the evaluation parameters from simple voltage threshold detection to analyzing multiple signal characteristics including voltage magnitude, rise time, pulse width, and temporal patterns. This multi-parameter approach allows the system to maintain high sensitivity while discriminating against false detections from soft objects based on their distinct signal signatures.
2Measurement precision
If voltage threshold is lowered to detect all impacts, then detection sensitivity is improved, but unintentional detonation from soft objects increases
Solution Approach 1:
The patent implements dynamic threshold adjustment based on the analyzed signal characteristics. Instead of using a fixed voltage threshold, the system adapts the detonation decision criteria based on the temporal evolution and pattern recognition of the detected signals, allowing low thresholds for sensitivity while preventing false triggers from soft objects through dynamic evaluation.
Solution Approach 2:
The system incorporates feedback mechanisms where the output from multiple sensors is continuously analyzed and fed back into the decision logic. The fuze evaluates the combined signals in real-time, adjusting the detonation decision based on the cumulative evidence from all sensors, which prevents unintentional detonation while maintaining high detection sensitivity.
3Device complexity
If conventional signal processing is used, then system complexity is minimized, but discrimination between soft and hard targets is insufficient
Solution Approach 1:
The patent applies preliminary signal conditioning and filtering stages before the main discrimination logic. The raw signals from piezoelectric sensors undergo preprocessing including amplification, filtering, and initial feature extraction, which prepares the data for more sophisticated discrimination algorithms while managing system complexity through staged 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
Effectively discriminates between desired hard targets and undesired soft objects, reducing the risk of unintentional detonation by filtering out high-frequency signals from soft objects while maintaining sufficient signal precision for hard target detection.
Implementation Method 1
an electrical output signal is generated in a piezoelectric crystal integrated in a fuze in a detonating device, such as a shell, upon impact on a target. The electrical signal generated by the piezoelectric crystal is related to a shockwave generated in the shell and the deceleration which occurs on impact of the projectile on the target.
Implementation Method 2
a damping layer adapted to attenuate signals of frequencies above a predetermined cutoff frequency
Data Source
AI summary
A piezoelectric sensor arrangement for use in a projectile comprises a piezoelectric sensor enveloped by a damping layer adapted to attenuate signals of frequencies above a predetermined cutoff frequency whereby the voltage output signal of the piezoelectric sensor upon impact on a desired hard target can be discriminated from voltage output signals originating from impact on undesired soft objects. A method of discriminating voltage outlet signals by means of the piezoelectric sensor arrangement and the use of a piezoelectric sensor arrangement in a projectile to safeguard unintentional detonation does not occur is described herein.