Dual-IMU Motion Separation for VR/AR Moving Reference Frames
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Solution Overview
Problem
Conventional virtual and augmented reality systems fail to separate user motion from vehicle motion, leading to nausea and erratic control due to oculovestibular mismatch and improper functioning of visual inertial odometry algorithms in moving reference frames.
Innovation Solution
A relative inertial measurement system using two inertial measurement devices, one coupled to the user and one to the vehicle, determines relative motion by subtracting vehicle motion from user motion, and a visual inertial odometry system adjusts motion information using camera data to correct for drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional VR/AR devices use a single IMU to determine user motion, then the device complexity is low, but the measurement precision of relative motion is poor because vehicle motion is incorrectly attributed to user motion
Solution Approach 1:
The system segments the motion measurement function by using two separate IMUs: one IMU attached to the user device measures combined user-vehicle motion, while another IMU attached to the vehicle measures only vehicle motion. This segmentation allows the system to isolate and subtract vehicle motion from the combined measurements, thereby accurately determining relative user motion within the vehicle reference frame.
Solution Approach 2:
The vehicle-mounted IMU acts as an intermediary that provides reference frame motion data. By introducing this intermediate measurement source, the system can compensate for vehicle acceleration and rotation effects, enabling accurate relative motion tracking despite the moving reference frame.
2Object-affected harmful factors
If conventional VR/AR devices attribute all IMU-measured motion to the user, then the system operation is simple, but harmful effects occur including user nausea due to oculovestibular mismatch
Solution Approach 1:
The system extracts vehicle motion components from the total motion measurements by using the vehicle-mounted IMU. By separating and removing the reference frame motion contribution, only the true relative user motion remains, preventing the oculovestibular mismatch that causes nausea while maintaining straightforward processing through direct subtraction of the extracted vehicle motion vectors.
Solution Approach 2:
The system implements feedback by continuously monitoring vehicle motion through the vehicle-mounted IMU and using this information to dynamically adjust and correct the user motion calculations. This closed-loop approach ensures that changes in vehicle acceleration and orientation are immediately compensated for, maintaining accurate relative motion tracking and preventing motion sickness.
3Reliability
If VIO algorithms use objects in the camera view as reference points, then the system can correct for drift, but reliability decreases when the vehicle is moving because some objects move with the reference frame while others do not
Solution Approach 1:
The system replaces the traditional VIO approach that relies on visual feature tracking with an inertial reference frame established by the vehicle-mounted IMU. This substitution provides a stable, non-visual reference frame that is independent of external objects, ensuring reliable drift correction whether the vehicle is stationary or moving, and eliminating the adaptability issues associated with selecting appropriate visual reference points.
Data Source
AI summary
Methods and systems for relative inertial measurement may include a user device comprising an inertial measurement device and/or a camera. A second inertial measurement device may be configured to move with a reference frame. One or more processors may receive inertial measurements from the first and second inertial measurement devices and determine movement of the user device relative to the reference frame by comparing the received inertial measurements. Additionally reference objects in a view of a camera may be used to calibrate the determined motion of the user device within the reference frame.