Spinning Projectile Roll Estimation Under Magnetic Distortion
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Solution Overview
Problem
Accurate roll angle estimation in spinning projectiles is hindered by distortions in magnetic sensor data due to self-magnetic fields, sensor offsets, and induced magnetic fields, which affect the precision of steering commands.
Innovation Solution
A system and method that corrects magnetic sensor data by estimating and removing distortions such as permanent magnetic fields, induced magnetic fields, and sensor offsets, using known geomagnetic field vectors and angular velocity data to determine the roll angle and roll rate of the projectile, allowing for precise steering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic sensor data is used to estimate roll angle, then steering commands can be generated, but distortion from self-magnetic fields reduces measurement precision
Solution Approach 1:
The patent converts the harmful self-magnetic field distortion into a measurable quantity by using magnetic sensors to detect both the geomagnetic field and the projectile's self-magnetic field. By characterizing the distortion pattern during calibration and compensating for it during flight, the system transforms the harmful magnetic interference into useful information for improving roll angle estimation accuracy.
2Measurement precision
If multiple distortion sources are corrected, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent merges multiple correction functions into a unified calibration and compensation process. During calibration, sensor offsets, permanent magnetic field distortions, and induced magnetic field coefficients are all estimated simultaneously through a series of maneuvers. During flight, these pre-calculated correction parameters are applied together to compensate for all distortion sources, reducing the operational complexity despite the multiple correction targets.
3Measurement precision
If magnetic sensors are used in spinning projectiles, then roll angle can be estimated, but sensor offsets and induced magnetic fields cause errors
Solution Approach 1:
The patent performs preliminary calibration actions during controlled maneuvers (level flight, banked turns, inverted flight) to characterize and store correction parameters before actual flight operations. Sensor offsets, permanent magnetic field vectors, and induced magnetic field coefficients are all determined in advance through these calibration maneuvers, allowing the system to compensate for these harmful effects during normal flight without real-time 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
Enables accurate roll angle and roll rate estimation, ensuring that steering commands are applied in the proper direction, thereby improving the trajectory control of spinning projectiles.
Implementation Method 1
estimating, with the at least magnetic sensor, a magnetic data output associated with a local magnetic field relative to the spinning projectile
Implementation Method 2
the first source of distortion is a permanent magnetic field of the spinning projectile
Implementation Method 3
magnetic fields produced by eddy currents on the spinning shell body
Implementation Method 4
estimating, with at least one angular rate sensor, a roll rate of the spinning projectile
Data Source
AI summary
A system and method for state estimation in spinning projectiles is provided. The state estimation is based, at least in part, on magnetic sensor data, angular velocity data, and correction terms applied to the magnetic sensor data and the angular velocity data. The system and method for state estimation in spinning projectiles estimates roll angles and roll rates of the spinning projectiles. The roll angle and roll rate estimates allow steering commands to be applied to steer the spinning projectiles in the proper direction.