Stride Vectoring for IMU Error Correction in Personal Navigation
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Solution Overview
Problem
Personal navigation systems face significant challenges in providing accurate location information in GPS-denied environments due to rapid error accumulation in inertial measurement units (IMUs), with heading errors contributing disproportionately to total position errors, and existing solutions like vision-based systems are computationally demanding or limited in accuracy.
Innovation Solution
The stride vector technique involves measuring position vectors between a pair of objects, such as boots or shoes integrated with a navigation system, to calculate distance, direction, and orientation, providing error corrections for IMUs and constraining both distance and heading error growth, using methods like trilateration or multilateration with ultrasonic signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If vision-based systems are used to compensate for heading error, then heading accuracy is improved, but computational demand increases significantly
Solution Approach 1:
The patent replaces vision-based computational systems with an acoustic field-based measurement system. Instead of using cameras and image processing to determine heading, the system uses ultrasonic transmitters and receivers to measure acoustic time-of-flight, providing heading information through direct acoustic measurement rather than complex visual computation.
Solution Approach 2:
The patent introduces acoustic signals as an intermediary medium between the navigation system and the environment. By using sound waves as the measurement carrier, the system achieves heading determination without requiring direct line-of-sight visual observations, thereby reducing computational complexity while maintaining measurement accuracy.
2Ease of operation
If IMU sensors are used to measure position changes, then navigation capability is provided, but error accumulation occurs rapidly
Solution Approach 1:
The patent implements a feedback mechanism where acoustic measurements of time-of-flight are continuously used to correct IMU-derived position estimates. The system compares acoustic measurements with IMU predictions and uses the discrepancies to calibrate and correct sensor drift, thereby maintaining position accuracy over extended periods.
Solution Approach 2:
The system performs preliminary calibration of IMU sensors using acoustic measurements during stationary phases. By establishing accurate baseline measurements when the device is at rest, the system prepares correction data that can be applied during motion phases to compensate for IMU errors before they accumulate significantly.
3Measurement precision
If additional sensors such as compass and pressure sensor are added to constrain error growth, then position accuracy is improved, but device complexity increases
Solution Approach 1:
The patent makes the acoustic measurement system serve multiple functions simultaneously. The same ultrasonic transmitters and receivers used for time-of-flight measurement also provide heading information, distance measurement, and calibration data. This multi-functionality reduces the need for separate dedicated sensors for each function.
Solution Approach 2:
The patent combines acoustic measurement capabilities with inertial sensing in an integrated navigation system. By merging the acoustic field-based measurement system with IMU sensors, the system achieves complementary information from different physical principles, improving overall accuracy without requiring entirely separate sensor systems.
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 significantly improves navigation accuracy by providing precise stride length measurements and position correction updates, reducing final position error and enabling accurate navigation in GPS-denied environments, while also allowing for self-calibration of IMUs during stationary phases.
Implementation Method 1
Typically, personal navigation systems use an inertial measurement unit (IMU), or some subset of inertial sensors, to measure changes in position and heading to track the movement of a person, ground vehicle, or air vehicle
Implementation Method 2
At least one position vector is measured between the first object and the second object when the first object is in motion and the second object is stationary
Data Source
AI summary
A method of error compensation for an inertial measurement unit is provided. The method comprises providing a first object including an inertial measurement unit, providing a second object proximal to the first object, and determining an initial position and orientation of the first object. A motion update is triggered for the inertial measurement unit when the second object is stationary with respect to a ground surface. At least one position vector is measured between the first object and the second object when the first object is in motion and the second object is stationary. A distance, direction, and orientation of the second object with respect to the first object are calculated using the at least one position vector. An error correction is then determined for the inertial measurement unit from the calculated distance, direction, and orientation of the second object with respect to the first object.