Steering Wheel Angle Calibration Using Stationary Object Sensing
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Solution Overview
Problem
Autonomous and semi-autonomous vehicles face challenges in maintaining a straight path due to factors like friction, tire pressure, and road slope, causing deviations from planned routes without real-time calibration of steering angles.
Innovation Solution
A vehicle computer system determines distances and angles relative to stationary objects using sensor data to calibrate the center steering wheel angle, adjusting it to maintain or update the steering based on predicted and measured distances to ensure alignment with the planned path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the vehicle operates autonomously without real-time steering calibration, then the operating simplicity is improved, but the path accuracy deteriorates due to friction, tire pressure variations, and road slope causing steering deviations
Solution Approach 1:
The system performs preliminary steering calibration by detecting a stationary object, measuring initial distance d1, determining best fit line parameters (slope m1, intercept c1), and calculating expected distance d2 at a second location before autonomous operation begins. This pre-calibration establishes baseline steering accuracy without requiring continuous manual adjustment during operation.
Solution Approach 2:
The system implements feedback by measuring the actual distance d2 to the stationary object at the second location, comparing it with the expected distance calculated from the best fit line, and determining whether the center steering wheel angle calibration is accurate based on the discrepancy between measured and expected values. This feedback loop enables automatic calibration adjustment.
2Measurement precision
If the system performs real-time steering calibration using sensor data and distance measurements, then the path accuracy is improved, but the computational complexity and processing time increase
Solution Approach 1:
The system performs preliminary calculations of the best fit line parameters (slope m1 and intercept c1) using sensor data from the first location before needing to make calibration decisions. This pre-processing reduces the computational burden during real-time operation by having reference values ready for comparison.
Solution Approach 2:
The system uses the vehicle's existing sensor infrastructure (distance sensors, steering angle sensors) to perform self-calibration without requiring external calibration equipment or complex additional hardware. The stationary object serves as a natural reference point, eliminating the need for specialized calibration tools.
3Measurement precision
If the vehicle moves to a second location for calibration verification, then the calibration accuracy is improved, but the time required for calibration increases due to additional movement and measurement steps
Solution Approach 1:
The system determines the second location and expected distance d2 in advance using the best fit line calculation before actual movement occurs. This allows the vehicle to move directly to the calibration verification point without unnecessary intermediate steps, minimizing calibration time while ensuring accuracy.
Solution Approach 2:
The stationary object serves as an intermediary reference point that enables calibration verification without requiring complex target systems or multiple measurement points. By using a single stationary object and calculating expected distances based on geometry, the system simplifies the calibration process while maintaining accuracy.
Data Source
AI summary
A first distance d1 between a vehicle at a first location and an object is determined. A best fit line representing the object is determined from a plurality of sensor data. A distance Δd to move to a second location is specified. A predicted second distance dp between the vehicle at the second location and the object is determined based on the first distance d1, the distance Δd, and the best fit line. The vehicle is operated from the first location to the second location based on a center steering wheel angle. A measured second distance d2 between the vehicle at the second location and object is determined. Then the center steering wheel angle is one of (a) maintained based on the predicted second distance dp matching the measured second distance d2, or (b) updated based on the predicted second distance dp being different than the measured second distance d2.