Projectile Sensor Fusion Layout for Spin Noise and Drift
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Solution Overview
Problem
Existing guidance systems for munitions face issues with high-frequency noise in accelerometers and drift in gyroscopes, which degrade accuracy during various flight maneuvers, particularly high spin rates and aggressive maneuvers.
Innovation Solution
A sensor farm comprising gyroscopes, accelerometers, and magnetometers with overlapping ranges and individual calibration, using sensor averaging and fusion techniques to combine data, mitigating noise and bias drift, and employing lead solder connections for shock resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If accelerometers are used to measure high spin rates, then angular velocity measurement capability is improved, but high-frequency noise increases
Solution Approach 1:
The patent combines multiple accelerometer types (analog and digital) with different measurement ranges and characteristics into a unified sensor farm. By merging sensors with complementary strengths, the system can select appropriate sensors based on flight conditions, using low-range sensors for low-speed phases and high-range sensors for high-speed phases, thereby reducing noise while maintaining measurement capability across the full speed range.
2Measurement precision
If gyroscopes are used to measure angular acceleration, then orientation measurement capability is improved, but bias drift increases
Solution Approach 1:
The patent introduces magnetometers as intermediary sensors to compensate for gyroscope drift. The magnetometer provides absolute orientation reference by measuring the Earth's magnetic field, serving as a mediator that corrects the accumulated errors in gyroscope measurements. This combination allows the system to maintain high orientation measurement precision while eliminating the bias drift problem through periodic recalibration using the magnetic field reference.
3Measurement precision
If multiple sensors with overlapping ranges are used, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent implements dynamic sensor selection and fusion where the system adaptively chooses which sensors to use based on real-time flight conditions. During low-speed phases, low-range sensors are activated; during high-speed phases, high-range sensors are activated. This dynamic approach allows the system to maintain high measurement accuracy across all flight regimes while managing complexity by not all sensors operating simultaneously at full capacity.
4Measurement precision
If sensors are positioned offset from center of spin, then centripetal spin measurement is improved, but susceptibility to shock increases
Solution Approach 1:
The patent segments the sensor farm into multiple groups positioned at different locations relative to the center of spin. Some sensors are placed offset to capture centripetal acceleration components, while others are positioned closer to the center to minimize shock exposure. This segmentation allows the system to obtain accurate centripetal spin measurements from offset sensors while using centrally-positioned sensors as backup during high-shock phases, thereby resolving the contradiction between measurement precision and shock susceptibility.
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 system provides a more accurate and reliable measurement of projectile position, velocity, and orientation by compensating for sensor weaknesses, enhancing precision and reliability under extreme conditions.
Implementation Method 1
high angular velocity measurements are improved by offsetting the plurality of accelerometers from a center of spin to obtain centripetal spin
Implementation Method 2
a second type being a gyroscope, the gyroscope providing angular acceleration data
Implementation Method 3
a third type being a magnetometer, the magnetometer providing position data relative to a fixed magnetic field
Implementation Method 4
the sensors are fixed to the circuit with lead solder with sufficient malleability to withstand a high shock environment
Data Source
AI summary
An apparatus that includes at least two types of sensors arranged on a projectile, each type of sensor including a plurality of sensors with overlapping ranges.