Steer-By-Wire Feedback Actuator Calibration for End Stop Shift
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Solution Overview
Problem
Existing steer-by-wire steering systems face challenges in accurately calibrating the absolute position of feedback actuators due to potential shifts in mechanical end stops during the lifetime of the system, affecting steering feel and reliability.
Innovation Solution
A method for calibrating feedback actuator positions involves moving the actuator to defined end stops, determining a new center position, and updating stored positions based on detected mechanical end stop changes, using motor torque and position data to adjust steering wheel angle limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the feedback actuator position is calibrated at production or replacement, then the initial steering feel is correct, but the calibration becomes inaccurate when end stops shift during system lifetime
Solution Approach 1:
The system performs preliminary calibration actions by moving the feedback actuator to defined end stops and recording positions before normal operation. This preliminary positioning establishes the center position and steering wheel angle limits that will be used during subsequent operation, ensuring accurate initial calibration.
Solution Approach 2:
The system continuously monitors the feedback actuator position and compares it against stored end stop positions. When deviations are detected indicating end stop shifts, the system provides feedback to update the stored positions and recalibrate the center position, maintaining accuracy over the system lifetime.
2Ease of operation
If mechanical end stops are used to define maximum steering angle, then physical limits are enforced, but the end stop positions shift during system lifetime affecting steering wheel angle accuracy
Solution Approach 1:
The system replaces purely mechanical end stop positioning with an electro-mechanical calibration system. The feedback actuator's position is calibrated using defined end stops and stored in memory, allowing the system to compensate for mechanical shifts through electronic adjustment of the center position and steering wheel angle limits.
Solution Approach 2:
The system changes the reference parameters for steering wheel angle by updating the stored end stop positions and recalculating the center position when shifts are detected. This parameter adjustment compensates for mechanical end stop shifts and maintains accurate steering angle limits despite physical wear or movement.
3Ease of operation
If the feedback actuator position is fixed after initial calibration, then the system is simple to operate, but it cannot adapt to end stop shifts that occur during system lifetime
Solution Approach 1:
The system transitions from a static calibration approach to a dynamic one by continuously monitoring feedback actuator position against stored end stop positions. When deviations indicate end stop shifts, the system dynamically updates the stored positions and recalibrates the center position, adapting to changes while maintaining simple operation through automated processes.
Data Source
AI summary
A method for calibrating a position of a feedback actuator of a steer-by-wire steering system of a road vehicle includes moving the feedback actuator to a first end stop of the feedback actuator and from there moving the feedback actuator to a second end stop, recording a position of the two end stops and based thereon determining a newly defined center position, moving the feedback actuator to the newly defined center position, and storing the newly defined center position in a memory as an offset value of an absolute steering wheel angle.