Linear Estimator for Aircraft Heading Without Magnetometer
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Solution Overview
Problem
Current aircraft piloting systems face challenges in accurately estimating ground speed and heading independently of magnetic measurements, particularly in environments with magnetic disturbances, and require expensive inertial units with lengthy alignment times.
Innovation Solution
A hybrid system combining a GNSS receiver and an AHRS device, utilizing a linear estimator to correct unbounded heading errors and provide accurate ground speed and heading estimates without magnetic measurements, by integrating GNSS speed measurements with AHRS acceleration and attitude data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic measurements are used to estimate heading, then heading accuracy is improved, but the system becomes sensitive to magnetic disturbances
Solution Approach 1:
The patent extracts and removes the magnetometer from the heading estimation system, relying solely on gyroscopic measurements from the AHRS device. This eliminates magnetic disturbance sensitivity while maintaining heading accuracy through continuous gyro integration and linear estimator correction.
Solution Approach 2:
The patent replaces expensive inertial units with a combination of standard AHRS device and GNSS receiver. The system uses readily available, cost-effective components that provide sufficient performance for the application.
2Reliability
If expensive inertial units are used to provide heading independent of magnetic measurements, then reliability is improved, but device cost and complexity increase
Solution Approach 1:
The patent merges the AHRS device and GNSS receiver into a hybrid system where the linear estimator combines data from both sources. This integration achieves reliable heading estimation independent of magnetic measurements using standard, cost-effective components rather than expensive inertial units.
Solution Approach 2:
The linear estimator acts as an intermediary that processes and combines data from the GNSS receiver and AHRS device. It corrects unbounded heading errors by integrating acceleration measurements and comparing with GNSS-derived position changes, providing reliable heading without requiring expensive inertial measurement units.
3Measurement precision
If inertial units with alignment procedures are used, then measurement precision is improved, but initialization time increases
Solution Approach 1:
The system performs preliminary alignment actions during aircraft taxiing and takeoff phases. The linear estimator continuously processes data from both GNSS and AHRS devices during these phases, preparing accurate heading estimates before precision navigation phases begin, thereby reducing initialization time.
4Device complexity
If GNSS receiver is used to measure ground speed, then device cost and size are reduced, but the system cannot provide heading independent of magnetic measurements
Solution Approach 1:
The patent merges GNSS receiver data with AHRS device measurements through a linear estimator. The GNSS provides ground speed and position information while the AHRS provides attitude and acceleration data. The linear estimator fuses these inputs to produce reliable heading estimates that are independent of magnetic measurements, achieving both system simplicity and magnetic independence.
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 robust and reliable estimates of ground speed and heading, insensitive to magnetic disturbances, without the need for expensive inertial units and with reduced initialization time, ensuring accurate piloting even in disturbed environments.
Implementation Method 1
a satellite navigation receiver that is more accurate, and above all less bulky and less expensive. This on-board receiver receives signals from a plurality of satellites belonging to one or more constellations of satellites
Implementation Method 2
The AHRS device makes use firstly of measurements from gyros and accelerometers for estimating the attitudes of the aircraft
Implementation Method 3
The AHRS device makes use firstly of measurements from gyros and accelerometers for estimating the attitudes of the aircraft
Implementation Method 4
utilizing a linear estimator to correct unbounded heading errors and provide accurate ground speed and heading estimates without magnetic measurements
Data Source
AI summary
A device for estimating an aircraft's speed relative to the ground and heading, while making no use of the rotation of the Earth or of the Earth's magnetic field. The device comprises in particular a first linear estimator that hybridizes a measurement of the speed of the aircraft relative to the ground as provided by a global navigation satellite system (GNSS) receiver with measurements of the acceleration and the attitudes of the aircraft coming from an attitude and heading reference system (AHRS) device without a gyrocompass and without a magnetometer. The first estimator is made linear by replacing the single “heading error estimate Δψ” state of prior art embodiments with two states, namely estimates of the sine and of the cosine of the heading error.