Heading Reference System Soft Iron Disturbance Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic heading reference systems in vehicles, such as aircraft, face errors due to local soft iron disturbances, which existing solutions have not adequately addressed in a cost-effective manner.
Innovation Solution
The system employs sensor instruments like magnetometers and gyroscopes to detect soft iron disturbances by comparing changes in magnetometer and gyro readings against predetermined thresholds, using multiple heading reference systems to identify and correct erroneous measurements, and applying calibration algorithms to maintain accurate heading information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external magnetometers are located on aircraft wings away from electrical devices to avoid soft iron magnetic disturbances, then magnetic heading measurement accuracy is improved, but installation cost and system complexity increase significantly
Solution Approach 1:
The patent converts the harmful soft iron magnetic disturbances into useful calibration data. By deliberately exposing the magnetometer to known magnetic field conditions generated by onboard electrical devices, the system performs automated calibration to determine soft iron disturbance characteristics. These previously harmful disturbances become the basis for calculating correction factors that improve heading accuracy without requiring relocation of the magnetometer.
Solution Approach 2:
The system implements continuous feedback by periodically comparing magnetometer readings with expected magnetic field values and using this feedback to update calibration parameters. The automated calibration process uses real-time monitoring of magnetic field variations to dynamically adjust correction factors, maintaining accurate heading measurements despite the presence of soft iron disturbances from electrical devices.
2Reliability
If multiple heading reference systems are installed at different locations to provide redundancy and alleviate soft iron effects, then measurement reliability is improved, but installation and maintenance cost increase significantly
Solution Approach 1:
Instead of installing multiple physical heading reference systems, the patent creates a virtual copy through software-based calibration. The system generates corrected heading measurements by applying calibration-derived correction factors to the single magnetometer's raw readings. This software copying approach provides the reliability benefits of multiple systems without the associated hardware costs and complexity.
Solution Approach 2:
The calibration system serves multiple functions: it characterizes soft iron disturbances, generates correction factors, validates magnetometer performance, and provides continuous compensation. This multi-functional approach replaces the need for multiple dedicated heading reference systems, achieving reliability through a single versatile system rather than multiple specialized components.
3Device complexity
If traditional magnetometer calibration methods are used without accounting for soft iron effects, then system simplicity is maintained, but heading accuracy deteriorates due to magnetic disturbances from electrical devices
Solution Approach 1:
The system performs preliminary calibration actions by characterizing soft iron disturbance characteristics before normal operation begins. During initial calibration phases, the system deliberately exposes the magnetometer to known magnetic field conditions and stores the resulting correction factors for use during subsequent operations. This preliminary characterization enables accurate compensated measurements throughout the aircraft's operational life without adding complexity to normal operation.
Solution Approach 2:
The calibration process changes the magnetometer's operational parameters by applying correction factors to compensate for soft iron effects. The system modifies the raw magnetic field readings through mathematical transformations that account for the characterized disturbances, effectively changing the measurement parameters to eliminate accuracy deterioration while maintaining system simplicity.
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
This approach provides accurate and reliable heading information by compensating for soft iron effects, reducing errors and maintenance costs, and is applicable to various vehicles with magnetic heading indication systems.
Implementation Method 1
the heading gyro is periodically corrected by means of data from an external magnetometer that relies on the earth's magnetic field to provide a heading relative to magnetic north
Implementation Method 2
the heading gyro is periodically corrected
Data Source
AI summary
A method and system for compensating for soft iron magnetic disturbances in multiple heading reference systems, such as aircraft heading reference systems, integrated standby units; or vehicle inertial systems, detects and provides a heading correction signal to the error prone heading reference system when a detected difference in value between a gyro heading relative to magnetic north and a magnetometer reading during a defined measurement period exceeds a predetermined acceptable threshold value of change, such as one based on the expected gyro drift over that period. Upon receipt of the heading correction signal, the gyro heading is adjusted to maintain an accurate heading relative to true magnetic north. If this threshold value is not exceeded, then the magnetometer reading is used for the heading value. This method is periodically repeated in order to continually maintain an accurate heading and may be employed for each heading measurement axis.