IMU Calibration via Vertical Acceleration for AR Headsets
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Solution Overview
Problem
Existing calibration methods for inertial measurement units (IMUs) in virtual and augmented reality applications face challenges in aligning reference systems accurately, especially when modules are worn on the user's body, as they lack a consistent 'left', 'right', 'up', or 'down' orientation, leading to inconsistent orientation measurements.
Innovation Solution
A calibration system that uses periodic measurements from IMUs attached to hands, arms, and the head to determine their orientation relative to a common user-defined reference system, utilizing vertical acceleration data to initiate calibration and store last orientations for efficient reactivation, allowing modules to be worn universally without inherent orientation designations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If IMUs are worn on user's body without inherent orientation designations, then versatility and ease of operation are improved, but measurement precision and reliability of orientation measurements deteriorate
Solution Approach 1:
The system performs preliminary calibration operations to establish a common reference system before normal operation. The computing device receives periodic acceleration measurements, determines sensor attachment status, and initiates calibration operations to align all IMU reference systems with a user-defined common reference system, storing last orientations for efficient reactivation.
Solution Approach 2:
The patent introduces a common reference system as an intermediary framework that mediates between multiple IMUs with different local reference systems. This common reference system acts as a mediator that translates and aligns measurements from various sensors (accelerometers, gyroscopes, magnetometers) across different modules to a unified coordinate system.
2Measurement precision
If calibration operations are performed continuously to maintain accuracy, then measurement precision is improved, but loss of time and productivity deteriorate
Solution Approach 1:
The computing device receives periodic acceleration measurements from sensor modules and performs calibration operations at appropriate intervals. The system determines when calibration is needed based on attachment status and operational context, rather than continuously, optimizing the balance between accuracy and time efficiency.
Solution Approach 2:
The system automatically determines whether sensor modules are attached to the user based on acceleration measurements and autonomously initiates calibration operations when needed. The computing device self-manages the calibration process without requiring explicit user intervention, reducing time loss while maintaining 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
Ensures accurate and consistent orientation measurements across various user configurations, enabling precise tracking of hand, arm, and head movements for enhanced virtual and augmented reality interactions by aligning IMU reference systems with the user's orientation, improving user experience and system reliability.
Implementation Method 1
Each IMU includes a tri-axial accelerometer, a tri-axial gyroscope, and a tri-axial magnetometer
Implementation Method 2
Each IMU includes a tri-axial accelerometer, a tri-axial gyroscope, and a tri-axial magnetometer
Implementation Method 3
Each IMU includes a tri-axial accelerometer, a tri-axial gyroscope, and a tri-axial magnetometer
Data Source
AI summary
A method including receiving, in a computing device, periodic measurements of accelerations from a plurality of sensor modules. The computing device determines whether each respective sensor module of the sensor modules is attached to a respective part of a user from the periodic measurements of accelerations from the plurality of sensor modules as received. In response to the determination that each respective sensor module of the sensor modules is attached to the respective part of the user, the method includes initiating, by the computing device, a calibration operation to calibrate orientation measurements of the sensor modules relative to a common reference system defined based on an orientation of the user.