Dynamic Heading Control via Sensor Fusion
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Solution Overview
Problem
Three-dimensional compass devices face inaccuracies due to lateral accelerations affecting accelerometers and drift issues with rate gyros, which corrupt tilt calculations and heading determinations in dynamic environments.
Innovation Solution
A method that combines average magnetic heading with compensated inertial heading, using low-pass filters to correct for artifacts, short-term dynamic accelerations, and long-term drift in both magnetic and inertial measurements, thereby adjusting filters based on long-term measurements to achieve accurate device heading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If accelerometers are used to determine device orientation, then tilt calculations can be performed, but lateral accelerations of translation corrupt the tilt calculations
Solution Approach 1:
The patent introduces a mediator approach by combining accelerometer and gyroscope data through a complementary filter. The gyroscope provides rotational information that is less susceptible to linear acceleration corruption, while the accelerometer provides tilt information. The filter mechanism reconciles these two data sources, using the gyroscope to correct accelerometer drift and the accelerometer to correct gyroscope bias, thereby achieving accurate orientation estimation despite the presence of lateral accelerations.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the weighting factors in the complementary filter based on detected motion conditions. When linear acceleration is detected, the system increases reliance on gyroscope data and decreases reliance on accelerometer data. The filter coefficients are modified in real-time based on the intensity and direction of detected accelerations, allowing the system to adapt to varying environmental conditions and maintain measurement precision.
2Measurement precision
If rate gyros are used to determine device orientation, then heading can be determined, but drift is induced by manufacturing properties and temperature changes
Solution Approach 1:
The patent implements feedback by continuously monitoring the discrepancy between heading values derived from the gyroscope and those from the magnetometer. When drift is detected in the gyroscope readings, the system uses the magnetometer's stable magnetic north reference to correct the gyroscope accumulation errors. This closed-loop feedback mechanism continuously compensates for drift induced by manufacturing variations and temperature changes, maintaining reliable heading determination over extended periods.
Solution Approach 2:
The patent substitutes the purely mechanical integration of gyroscope data with a hybrid approach that incorporates magnetic field measurements. Instead of relying solely on mechanical integration which accumulates drift errors, the system uses magnetic field sensing to provide an independent reference frame. This substitution of the error-prone mechanical integration process with magnetic field-based correction significantly reduces the impact of manufacturing properties and temperature variations on heading accuracy.
3Measurement precision
If magnetic heading is used to determine device orientation, then heading can be determined, but artifacts are introduced that corrupt the measurement
Solution Approach 1:
The patent introduces a mediator approach by using the gyroscope data as an intermediary to correct magnetic heading measurements. The gyroscope provides high-frequency rotational information that can compensate for artifacts in the magnetic heading data caused by metal interference, magnetic anomalies, or environmental disturbances. The complementary filter mechanism allows the system to switch between relying on magnetic heading and gyroscope-derived heading based on the quality and reliability of each measurement source at any given moment.
Solution Approach 2:
The patent applies dynamics by making the filter coefficients adaptive rather than fixed. The system dynamically adjusts the weighting between magnetic heading and gyroscope data based on real-time detection of measurement quality. When magnetic artifacts are detected, the system dynamically increases reliance on gyroscope data. The filter parameters are modified in response to detected conditions such as high linear acceleration or magnetic interference, allowing the system to adapt to varying environmental conditions and maintain measurement precision.
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 continuous and accurate device heading determination, minimizing user intervention and requiring only inexpensive sensors and a low-cost microprocessor, effectively addressing errors in both magnetic and inertial measurements.
Implementation Method 1
The system may apply at least one low-pass filter to the magnetic heading to remove the artifacts
Implementation Method 2
The system may apply at least one low-pass filter to the orientation measurements of the device frame of reference to remove the short term dynamic accelerations
Implementation Method 3
The system may compensate for the time delay of the inertial heading by filtering long term drift from measurements of the inertial heading
Data Source
AI summary
In one embodiment a method and corresponding apparatus are arranged to determine an accurate device heading by continuously combining an average magnetic heading with the compensated inertial heading. The example embodiment obtains the compensated inertial heading by compensating for a time delay of an inertial heading.