Vehicle Position Estimation Using Speed-Dependent Tire Radius Correction
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Solution Overview
Problem
Existing vehicle position estimation methods, such as those using the pulse distance factor calculated by GPS and wheel speed sensors, suffer from reduced accuracy due to changes in tire rolling radius with vehicle speed, leading to inaccuracies in traveled distance measurement and subsequent position estimation.
Innovation Solution
A position estimation device that acquires vehicle position, rotation parameters, and speed, calculates correction factors for tire rolling radius based on vehicle speed ranges, and corrects the reference tire rolling radius to improve distance calculation accuracy, incorporating wheel load, temperature, and air pressure for enhanced precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the traveled distance is measured by pulse distance factor multiplied by number of pulses counted by wheel speed sensor, then the position estimation can be performed, but the accuracy of vehicle position estimation is reduced due to tire rolling radius changes with vehicle speed
Solution Approach 1:
The patent applies dynamics by making the tire rolling radius adjustable according to vehicle speed. The ECU stores multiple tire rolling radius values corresponding to different vehicle speed ranges and selects the appropriate value dynamically. This resolves the contradiction by allowing the measurement system to adapt to changing conditions (vehicle speed), thereby maintaining measurement accuracy consistency across different operating conditions.
Solution Approach 2:
The patent changes the parameter of tire rolling radius based on vehicle speed. The ECU divides vehicle speed into multiple ranges and stores different tire rolling radius values for each range. When the vehicle speed changes, the system selects the corresponding tire rolling radius value, thus maintaining accurate traveled distance measurement despite variations in tire rolling radius with speed.
2Measurement precision
If GPS is used to acquire vehicle position, then position information can be obtained, but position information becomes unavailable in areas with weak GPS signals
Solution Approach 1:
The patent uses traveled distance calculation as an intermediary method to bridge the gap when GPS is unavailable. The system calculates traveled distance by integrating wheel speed sensor data with speed-adjusted tire rolling radius values, and uses this calculated distance combined with vehicle orientation to estimate position. This intermediary approach maintains position acquisition availability in areas with weak GPS signals while preserving reasonable accuracy.
3Device complexity
If a single reference tire rolling radius is used for all vehicle speeds, then the device complexity is reduced, but the accuracy of traveled distance measurement deteriorates
Solution Approach 1:
The patent implements dynamics by transitioning from a static single reference tire rolling radius to a dynamic multi-value system. The ECU stores multiple tire rolling radius values corresponding to different vehicle speed ranges and selectively applies the appropriate value based on current speed. This maintains manageable device complexity through software-based management while significantly improving traveled distance measurement accuracy across varying speeds.
Data Source
AI summary
A position estimation device includes an ECU. The ECU is configured to estimate the position of a vehicle using at least a traveled distance of the vehicle. The ECU calculates correction factors for a reference tire rolling radius and stores the correction factors in a storage device. Each of the correction factors is set for a corresponding one of a plurality of vehicle speed ranges. The ECU calculates the traveled distance of the vehicle based on a rotation parameter and the corrected reference tire rolling radius obtained by correcting the reference tire rolling radius using the correction factor.