Handheld Gyroscope and Compass Bias Calibration
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Solution Overview
Problem
Existing methods for calibrating gyroscopes and compasses in handheld devices are inefficient, requiring complex device movements and relying on reliable accelerometer and compass data, which can be unreliable in certain conditions, leading to continuous drift due to uncompensated bias errors.
Innovation Solution
A novel method that uses gyroscope data to determine compass bias with small device movements and stores quaternion-based angular velocity terms for estimating gyroscope bias, even when compass and accelerometer data are unreliable, allowing continuous bias estimation across varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional least squares method is used to calibrate compass, then compass bias can be determined, but user must move device through complex trajectory (figure eight) which increases operation complexity and time
Solution Approach 1:
The gyroscope serves as an intermediary tool to assist compass calibration. By using gyroscope data to determine device orientation and rotation, the system can calculate compass bias without requiring the user to perform complex figure-eight motions. The gyroscope mediates between the user's simple device movement and the compass calibration process, enabling accurate bias determination through mathematical relationships between gyroscope measurements and compass readings.
Solution Approach 2:
The system performs preliminary gyroscope calibration and stores calibration data before attempting compass calibration. By pre-calibrating the gyroscope and having it ready to provide orientation data, the system eliminates the need for complex user movements during compass calibration. The preliminary gyroscope calibration creates a foundation that simplifies the subsequent compass bias determination process.
2Reliability
If conventional method relies on accelerometer and compass data for gyro offset compensation, then gyro bias can be corrected, but system becomes unreliable when accelerometer or compass data is unavailable due to interference or high linear acceleration
Solution Approach 1:
The gyroscope performs self-calibration by using its own measurement data in combination with compass data to determine its own bias offset. The system integrates gyroscope angular velocity measurements with compass heading information to calculate and correct gyro bias continuously. This self-service capability allows the gyroscope to maintain accuracy without relying on accelerometer data, enabling operation in conditions with high linear acceleration where accelerometers become unreliable.
Solution Approach 2:
The system implements continuous feedback by constantly monitoring the relationship between gyroscope measurements and compass readings. By comparing the orientation changes measured by the gyroscope with the heading changes detected by the compass, the system generates feedback signals that are used to adjust and correct gyro bias in real-time. This feedback mechanism ensures reliable offset compensation across varying operational conditions.
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 and efficient calibration of gyroscopes and compasses with reduced movement requirements and continuous bias estimation, improving orientation accuracy and stability in handheld devices.
Implementation Method 1
a gyroscope is used for measuring or maintaining orientation based on the Coriolis Effect
Implementation Method 2
a compass is used for determining direction relative to the earth's magnetic pole
Data Source
AI summary
Techniques for estimating compass and gyroscope biases for handheld devices are disclosed. The compass bias can be determined by causing a small movement of the handheld device and comparing the data obtained from the compass with the data obtained from the gyroscope. The gyroscope bias can be determined by obtaining a quaternion based angular velocity term of the handheld device when the accelerometer and compass data are reliable, and then comparing the angular velocity term with the gyro data to estimate the gyro bias. When the compass and/or the accelerometer data are unreliable, a previously determined quaternion angular velocity term is used. The gyroscope bias can also be determined by measuring gyroscope biases at various temperatures in a non-factory setting, storing the data in a memory, and using the data to estimate gyro biases when the accelerometer and/or the compass data are unreliable.