GNSS Wheel Radius Calibration for Speedometer Accuracy
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Solution Overview
Problem
Modern vehicle speed measurement systems, relying on indirect sensor measurements and GNSS technology, face accuracy issues due to manufacturing variations, temperature effects, and limited satellite coverage, leading to errors in speed and distance calculations, which are critical for applications like rental vehicle billing and autonomous driving safety.
Innovation Solution
Combining speed sensor data with inertial sensor and GNSS information, a processor adjusts the wheel radius correction factor when a statistically significant difference is detected between the two measurements, ensuring accuracy within 1% error by aligning the speed measurements from different sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GNSS satellite technology is used to determine vehicle speed, then location and speed information can be obtained, but the system becomes less effective in areas with tall buildings or impeded views of the sky
Solution Approach 1:
The patent combines GNSS speed measurements with inertial sensor measurements and wheel speed sensor measurements into a unified speed determination system. The processor integrates data from multiple sources (GNSS receiver, inertial sensors, wheel speed sensors) to calculate vehicle speed, ensuring continuous reliable operation even when GNSS signals are blocked by tall buildings or other obstructions.
2Ease of operation
If indirect sensor measurements are used to determine vehicle speed, then speed information can be obtained, but the accuracy is limited to within a few percent of actual speed
Solution Approach 1:
The system continuously compares speed measurements from different sources (wheel speed sensors, inertial sensors, GNSS) and uses statistical analysis to detect significant discrepancies. When differences exceed predetermined thresholds, the system adjusts the wheel radius correction factor to compensate for measurement errors, thereby improving overall speed accuracy while maintaining ease of operation.
3Measurement precision
If wheel radius correction is applied to improve speed accuracy, then measurement precision improves, but the system complexity increases due to additional calibration requirements
Solution Approach 1:
The system performs automatic wheel radius calibration by comparing speed measurements from inertial sensors and GNSS with wheel speed sensor measurements. The processor automatically detects statistically significant differences and adjusts the wheel radius correction factor without requiring manual calibration procedures, thereby improving speed accuracy while minimizing the increase in system complexity.
Data Source
AI summary
Method and apparatus are disclosed for GNSS statistical speed calibration An example vehicle includes a wheel, a speed sensor for determining a first vehicle speed, an inertial sensor, and a processor. The processor may be configured for determining a second vehicle speed based on information from the inertial sensor and information from a satellite based system, determining that a difference between the first and second vehicle speeds is statistically significant, and responsively adjusting a value of the radius of the wheel.