Orientation Determination Amid Electromagnetic Interference
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Solution Overview
Problem
Consumer electronic devices with magnetic and inertial sensors face challenges in determining orientation due to electromagnetic interference, which can render magnetometer data inaccurate, especially in devices like digital still cameras with internal motors generating interference.
Innovation Solution
The system uses data from gyroscopes and accelerometers to generate an estimate of orientation change, activating the gyroscope before interference occurs to provide accurate magnetometer orientation calculations, and employs a processor to blend gyroscope-stabilized values with magnetometer data to compensate for interference, thereby maintaining orientation determination without continuous gyroscope operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetometer data is used to determine orientation, then compass orientation information can be obtained, but electromagnetic interference from internal motors renders the magnetometer data inaccurate
Solution Approach 1:
The patent introduces gyroscope data as an intermediary element to mediate between the corrupted magnetometer readings and the orientation calculation. When electromagnetic interference is detected, the system uses gyroscope measurements of angular velocity integrated over time to estimate orientation changes, bypassing the unreliable magnetometer data during interference periods
Solution Approach 2:
The system performs preliminary calibration and characterization of the device's electromagnetic interference patterns before actual orientation measurement. By pre-identifying when and how interference occurs (e.g., during motor operation), the system can proactively switch to alternative sensing strategies before corrupted data is generated
2Measurement precision
If gyroscope is activated continuously to compensate for interference, then accurate orientation data can be maintained, but power consumption increases
Solution Approach 1:
Instead of continuous operation, the gyroscope is activated periodically and selectively based on detected interference conditions. The system monitors for signs of electromagnetic interference and only activates the gyroscope when needed, using periodic calibration updates during non-interference periods to maintain accuracy while minimizing power consumption
Solution Approach 2:
The system dynamically adjusts gyroscope operation based on real-time conditions. The gyroscope activation state transitions between active and standby modes depending on interference detection, and the integration time constant is dynamically adjusted to balance between responsiveness to orientation changes and filtering of noise, optimizing power consumption while maintaining accuracy
3Measurement precision
If magnetometer and accelerometer data are blended, then orientation can be determined, but electromagnetic interference still corrupts the magnetometer component
Solution Approach 1:
The patent applies local quality by treating different sensor data sources differently based on local conditions. When electromagnetic interference is present, the magnetometer data is locally discounted or weighted to zero in the fusion algorithm, while accelerometer and gyroscope data are weighted higher. This localized adjustment of data quality weights allows the system to maintain reliable orientation determination by adapting the contribution of each sensor to the current operational context
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 ensures accurate orientation data in the presence of electromagnetic interference, conserving power by activating the gyroscope only when needed and maintaining reliable orientation calculations for applications like digital cameras, even when magnetometer data is unreliable.
Implementation Method 1
data generated by one or more gyroscopes in the device, in conjunction with data generated by one or more accelerometers, can be used to generate an estimate of the change of orientation of the device
Implementation Method 2
accelerometers to measure device acceleration or gravity
Implementation Method 3
magnetometers to measure magnetic field
Data Source
AI summary
A mechanism is provided to determine orientation of a device that includes sources of electromagnetic interference. Data generated by one or more gyroscopes in the device, in conjunction with data generated by one or more accelerometers, can be used to generate an estimate of the change of orientation of the device from the time of a last accurate magnetometer reading. In one embodiment, in order to conserve system power, the gyroscope is kept powered down or in a stand-by state until receiving a control signal to power up. The control signal is provided in advance of the source of electromagnetic interference being powered up, thereby providing an accurate starting point from which magnetometer orientation estimates may be calculated during such interference.