IMU Calibration Using Optical Marks and Pose Rotation
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Solution Overview
Problem
Existing computer input devices for virtual reality and augmented/mixed reality applications face challenges in accurately calibrating inertial measurement units attached to users' arms to align with a common reference coordinate system, leading to deviations in measurement spaces and affecting the precision of gesture recognition and control.
Innovation Solution
A system that uses specific user poses to calibrate inertial measurement units (IMUs) attached to arms, head, and hands by computing relative orientation changes between reference poses, allowing the computing device to align sensor device measurements with a common reference coordinate system, and includes methods for recalibrating after initial calibration to account for device movement and slippage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If inertial measurement units are attached to arms and head for gesture recognition, then gesture control capability is enabled, but measurement precision deteriorates due to device movement and slippage
Solution Approach 1:
The system performs preliminary calibration by capturing images of calibration patterns at specific poses (neutral pose, left pose, right pose) before actual gesture recognition begins. This preliminary action establishes reference orientation data that compensates for subsequent device movement and slippage during operation.
Solution Approach 2:
The system continuously compares current sensor readings against the calibrated reference data from the captured poses. When deviations are detected due to device movement or slippage, the system uses the orientation differences to correct subsequent measurements, providing continuous feedback that maintains measurement precision.
2Measurement precision
If calibration is performed to align sensor measurements with reference coordinate system, then measurement precision is improved, but time consumption increases due to multiple pose requirements
Solution Approach 1:
The system performs calibration with three specific poses (neutral, left, right) which is more than a single pose but less than complete multi-axis calibration. This partial action approach provides sufficient precision for gesture recognition applications while minimizing calibration time compared to exhaustive calibration methods.
Solution Approach 2:
The system changes the orientation parameter of the device through predefined poses during calibration. By capturing calibration data at specific, discrete orientations rather than continuous movement, the system efficiently establishes reference points that enable accurate coordinate system alignment without requiring extensive calibration time.
3Measurement precision
If multiple sensor devices are used on arms and head, then gesture recognition accuracy is improved, but device complexity increases
Solution Approach 1:
The system combines data from multiple sensor devices (head-mounted device and arm-mounted devices) into a unified coordinate system through calibration. By merging the sensor inputs and processing them together using the calibrated orientation relationships, the system achieves improved gesture recognition accuracy while managing complexity through integrated processing.
Data Source
AI summary
A system including: a sensor module having an inertial measurement unit and attached to the head of a user. The sensor module is initially calibrated to measure its orientation relative a reference pose. To recalibrate the sensor module according to a calibration pose, a camera of the sensor module is used to capture an image of at least one optical mark (e.g., configured on devices held in hands in the calibration pose in front of the user). A direction identified from the image is rotated according to the rotational transformation between the reference pose and the calibration pose measured by the sensor module and then projected on to a horizontal plane relative to the reference pose. The angle in the horizontal plane between the projected direction and the front facing direction is used for the calibration of the subsequent orientation measurements of the sensor module.