Vehicle Speed Estimation Using GPS Scale-Factor Correction
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Solution Overview
Problem
Existing vehicle speed estimation methods fail to accurately correct errors in vehicle speed, leading to low accuracy in estimated speed due to variations in tire radius and acceleration, especially at different vehicle speeds.
Innovation Solution
A vehicle speed estimation device that calculates a scale factor based on the ratio and relationship between wheel speed and GPS-derived speed, using acceleration data to correct errors, and integrates acceleration to estimate actual vehicle speed, with optional segmentation of speed ranges and consideration of acceleration thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If vehicle speed is calculated based on wheel speed sensor, then speed can be obtained from direct sensor measurement, but measurement precision deteriorates due to tire radius variations and acceleration errors
Solution Approach 1:
The patent introduces GPS-derived speed as an intermediary reference to correct wheel speed sensor measurements. The system calculates speed using both wheel speed sensor data and GPS data, then uses the GPS-based speed (which is less affected by tire radius variations) to correct and refine the wheel speed sensor readings, thereby improving overall measurement precision.
Solution Approach 2:
The system implements feedback by continuously comparing wheel speed sensor measurements with GPS-derived speed and using the difference to correct future wheel speed readings. This closed-loop approach allows the system to compensate for sensor errors in real-time, improving measurement accuracy over time.
2Measurement precision
If scale factor is estimated based on ratio of GPS speed to wheel speed, then speed estimation accuracy improves, but device complexity increases due to additional calculation requirements
Solution Approach 1:
The patent changes the parameter used for speed estimation from raw wheel speed to a corrected speed that incorporates a scale factor. The scale factor is derived from the ratio of GPS speed to wheel speed and is used to adjust future wheel speed measurements. This parameter transformation simplifies the overall calculation by pre-compensating for systematic errors.
3Measurement precision
If acceleration data is integrated to correct speed errors, then speed estimation accuracy improves across varying acceleration conditions, but calculation complexity increases
Solution Approach 1:
The system performs preliminary action by pre-calculating and storing acceleration data from the acceleration sensor, then using this pre-acquired data to correct speed estimation errors. The acceleration data is integrated in advance to create correction values that are applied to future speed measurements, reducing the computational burden during real-time operation.
Data Source
AI summary
A vehicle speed estimation device is configured to calculate a first vehicle speed of a vehicle based on a wheel speed sensor, calculate a second vehicle speed of the vehicle based on a signal from a positioning satellite, estimate a scale factor corresponding to the first vehicle speed, based on a ratio of the second vehicle speed to the first vehicle speed and a relationship with the first vehicle speed, and estimate an actual vehicle speed of the vehicle by multiplying the first vehicle speed by the scale factor.