Magnetometer-Free Motion Capture Using UWB and Biomechanical Modeling
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Solution Overview
Problem
Existing human body inertial motion capture systems rely on magnetometers to correct yaw angle drift, which are unreliable in indoor environments with magnetic disturbances, limiting their accuracy and applicability.
Innovation Solution
A magnetometer-free system using inertial measurement units (IMUs) and ultra-wideband (UWB) localization, combined with a biomechanical model and novel Kalman filter techniques, to estimate and correct yaw angles without relying on magnetometers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetometers are used to correct yaw angle drift in inertial motion capture systems, then measurement precision is improved, but reliability deteriorates in indoor environments with magnetic disturbances
Solution Approach 1:
The patent removes the magnetometer from the inertial motion capture system, extracting the magnetic sensing component that causes reliability issues in indoor environments. The system achieves yaw angle estimation using only inertial sensors (accelerometers and gyroscopes) combined with optical flow and visual odometry, eliminating dependence on magnetic fields that can be distorted by ferromagnetic objects in indoor settings.
Solution Approach 2:
The patent introduces optical flow and visual odometry as intermediary mechanisms to estimate yaw angle changes. Instead of directly measuring magnetic field orientation, the system uses image processing techniques to track motion patterns and infer rotational movements, serving as a mediator between visual input and orientation estimation.
2Measurement precision
If magnetometers are used for 3-D localization, then measurement precision is improved, but device complexity increases due to additional sensor integration
Solution Approach 1:
The patent extracts and removes the magnetometer from the sensor system, simplifying the device architecture while maintaining localization capabilities. The system uses only inertial measurement units (IMUs) combined with optical flow and visual odometry algorithms to achieve 3-D localization without requiring magnetic field sensors.
Solution Approach 2:
The patent makes the inertial measurement units and image processing system multi-functional, enabling them to perform both localization and orientation estimation tasks that previously required separate magnetometer-based systems. The same IMU data and visual processing pipeline serve multiple purposes, reducing overall system complexity.
3Measurement precision
If magnetometers are used to provide stable heading angle, then measurement precision is improved, but adaptability deteriorates in varying magnetic disturbance conditions
Solution Approach 1:
The patent removes the magnetometer that provides stable heading angle measurements but fails to adapt to varying magnetic disturbances. The system replaces this with optical flow and visual odometry based heading estimation, which naturally adapts to different environmental conditions since it relies on visual motion patterns rather than magnetic fields.
Solution Approach 2:
The patent changes the fundamental parameter used for heading angle estimation from magnetic field orientation to visual motion patterns. This parameter change enables the system to adapt to varying magnetic disturbance conditions while maintaining measurement precision through alternative estimation mechanisms.
Data Source
AI summary
The present disclosure provides substantially magnetometer-free systems and methods for motion capture of a subject including 3-D localization and posture tracking by fusing inertial sensors with a localization system and a biomechanical model of the subject. Using the novel Kalman filter based fusion techniques disclosed herein, the localization data aided with the biomechanical model can eliminate the drift in inertial yaw angle estimation.