Autonomous Steering Angle Bias Correction Using Sensor Feedback
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Solution Overview
Problem
Autonomous vehicles face challenges in accurately determining and correcting steering wheel bias, which affects the precision of steering angle control, especially when the steering angle sensor reads non-zero values at the zero position.
Innovation Solution
A method is implemented to determine the steering wheel angle bias by subtracting the measured steer angle from the steer command, using inputs from sensors like yaw rate and image sensors, and continuously updating this bias every 10 milliseconds, with filtering to improve accuracy. This bias is then used to correct the steering angle, ensuring precise control of the electronic power steering system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a steering angle sensor is used to measure steering wheel position, then steering angle control can be implemented, but the sensor introduces bias that degrades measurement precision
Solution Approach 1:
The patent introduces an intermediary calculation process that uses multiple sensor inputs (steering angle sensor, yaw rate sensor, image sensor) to compute the actual steering angle, rather than relying directly on the biased steering angle sensor reading. This intermediary computation acts as a mediator to eliminate the sensor bias while preserving the steering control functionality.
Solution Approach 2:
The system implements feedback by continuously comparing the commanded steering angle with the actual steering angle derived from multiple sensors, and using this comparison to correct for bias. The bias correction is updated continuously based on the difference between expected and actual steering states, allowing the system to adapt and maintain precision despite sensor inaccuracies.
2Measurement precision
If steering wheel bias is corrected continuously, then measurement precision improves, but computational complexity and processing time increase
Solution Approach 1:
The bias correction system is segmented into distinct functional components: a bias determination module that calculates bias from sensor inputs, a bias storage module that retains the calculated bias, and a correction module that applies the bias correction to steering angle measurements. This segmentation allows each component to perform its specific function efficiently, reducing overall computational complexity.
Solution Approach 2:
The system performs preliminary action by pre-calculating and storing the steering wheel bias in advance, before it is needed for correction. The bias is determined once based on sensor inputs and then reused for multiple steering angle corrections, avoiding repeated complex calculations and reducing real-time processing requirements.
3Measurement precision
If multiple sensors are used to determine steering angle, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent applies multi-functionality by using the same set of sensors (steering angle sensor, yaw rate sensor, image sensor) for multiple purposes: determining steering angle, calculating vehicle orientation, and computing bias correction. This universal use of sensors reduces the need for additional dedicated sensors, thereby limiting the increase in device complexity while maintaining high measurement precision.
Data Source
AI summary
A method for controlling an autonomous vehicle includes: determining whether an autonomous control mode of the autonomous vehicle is active; determining a steering wheel angle bias in response to determining that the autonomous control mode of the autonomous vehicle is active; and controlling, via a steering controller of the autonomous vehicle, an electronic power steering system of the autonomous vehicle using the steering wheel angle bias.