Ultrasonic Tracking for VR Controllers Using Time-of-Flight
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Solution Overview
Problem
Current systems for tracking controllers in virtual reality, augmented reality, and telesurgery systems face challenges in providing accurate and granular motion information due to the limitations of inertial measurement units (IMUs), which accumulate errors and fail to meet the required precision.
Innovation Solution
The system combines ultrasonic time-of-flight and time-difference-of-arrival measurements with inertial measurements, using a base station and tracked objects equipped with ultrasonic transducers to estimate relative location and orientation, and employs radio-synchronization for accurate tracking and synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inertial measurement units (IMUs) are used for tracking controllers, then the system can provide motion information, but accumulated error occurs and measurement precision deteriorates
Solution Approach 1:
The patent introduces ultrasonic transducers as an intermediary measurement system to provide absolute position references that correct the accumulated errors in IMU-based relative motion tracking. The ultrasonic time-of-flight measurements serve as a mediator between the IMU and the final tracked position, resetting error accumulation periodically.
Solution Approach 2:
The patent merges IMU-based inertial tracking with ultrasonic time-of-flight measurement systems into a hybrid tracking architecture. The IMU provides high-frequency relative motion data while ultrasonic transducers provide absolute position corrections, combining the advantages of both systems to achieve both high update rates and long-term accuracy.
2Measurement precision
If ultrasonic transducers are added to the system, then measurement precision improves, but device complexity increases
Solution Approach 1:
The base station performs multiple functions: it generates ultrasonic tracking signals, receives ultrasonic responses from transducers, processes time-of-flight measurements, and synchronizes the entire tracking system via radio communications. This multi-functionality reduces the need for separate dedicated components for each function.
Solution Approach 2:
Radio-frequency synchronization signals act as an intermediary mechanism to coordinate the timing between the base station and tracked objects without requiring direct physical connection or complex wiring. The radio synchronization mediates the timing relationship, simplifying the overall system architecture.
3Measurement precision
If multiple ultrasonic pulses are transmitted in series, then measurement precision improves through time-difference-of-arrival, but time delays between pulses may cause interference
Solution Approach 1:
The system transmits ultrasonic pulses in periodic sequences with carefully calculated time intervals. Each pulse is separated by a time delay that allows the previous pulse to be fully received and processed before the next pulse is transmitted, creating a periodic measurement cycle that avoids interference while maintaining continuous tracking.
Solution Approach 2:
The system pre-calculates and applies time delays between pulse transmissions based on expected target distances and ultrasonic propagation speeds. This preliminary timing adjustment ensures that pulses are transmitted at optimal intervals to maximize measurement accuracy while preventing temporal overlap and interference between successive pulses.
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 enhances the accuracy and precision of controller tracking by reducing errors and providing high update rates for orientation estimates, enabling effective interaction in VR, AR, and telesurgery environments.
Implementation Method 1
each comprising three ultrasonic transducers, each configured to transmit and receive ultrasonic pulses
Implementation Method 2
information corresponding to the ultrasonic pulses (e.g., time-difference-of-arrival, time-of-flight, or the like)
Implementation Method 3
employs radio-synchronization for accurate tracking and synchronization
Data Source
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AI summary
A tracking method is disclosed. The method may include displaying visual content on a screen. A base station may be stationary with respect to the screen while the visual content is being displayed. In contrast, one or more objects may move with respect to the screen while the visual content is being displayed. The one or more objects may be tracked so that the movement thereof may be used to alter the visual content. Such tracking may involve the base station and the one or more objects sending and/or receiving one or more ultrasonic pulses. Time-difference-of-arrival and/or time-of-flight of the one or more ultrasonic pulses may then be used to estimate a relative location and/or a relative orientation of the one or more objects with respect to the base station in three dimensional space.