Steering Control Device Axial Force Calculation
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Solution Overview
Problem
The complexity of setting axial forces in steering control devices for steer-by-wire systems, which are necessary to convey road surface information to drivers, leads to complications in determining the steering reaction force, as multiple axial forces need to be considered for different scenarios, such as obstacle contact and changes in steering angle ratio.
Innovation Solution
A steering control device that calculates a target reaction torque and difference axial force based on the difference between reference and converted angles, considering the steering angle ratio, and adjusts these forces using viscous and end axial components to accurately convey the vehicle's turning state to the driver, simplifying the setting of axial forces and reducing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple axial forces are considered to determine steering reaction force for different scenarios, then the accuracy of steering reaction force determination is improved, but the complexity of setting axial forces increases
Solution Approach 1:
The patent applies universality by creating a unified approach to handle multiple axial force scenarios. Instead of setting different axial forces for obstacle contact and steering angle ratio changes separately, the system uses a single conversion mechanism that transforms turning angle to steering angle based on the steering angle ratio, allowing one formula to handle multiple situations effectively
Solution Approach 2:
The patent utilizes parameter changes by introducing the steering angle ratio as a dynamic parameter that varies with driving conditions. By converting the turning angle to a steering angle equivalent using this ratio, the system adapts the axial force calculation to different scenarios (obstacle contact, steering limits) without requiring separate setting for each condition
2Reliability
If axial forces are set based on specific situations, then the accuracy of force feedback is improved, but the complexity of control logic increases
Solution Approach 1:
The patent implements feedback by continuously monitoring the steering angle ratio and using it to convert the turning angle to an equivalent steering angle. This feedback mechanism allows the system to automatically adjust the axial force calculation based on current driving conditions, maintaining accurate force feedback without requiring complex if-else control logic for different scenarios
Data Source
AI summary
A steering control device includes a control unit configured to control at least an operation of a steering-side motor. The control unit is configured to calculate a target reaction torque; calculate a difference axial force that is used to limit steering for turning the turning wheels in a predetermined direction, the difference axial force being reflected in the target reaction torque; and set a reference angle to one of a steering angle and a turning angle, set a converted angle to an angle obtained by converting another of the steering angle and the turning angle according to a steering angle ratio, and calculate the difference axial force based on a difference between the reference angle and the converted angle.