Steering Control Device Axial Force Allocation
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Solution Overview
Problem
The existing steering control devices for Steer By Wire systems face challenges in applying an appropriate steering reaction force, particularly when the accuracy of the control amount based on the steering angle degrades, leading to inappropriate steering reaction forces.
Innovation Solution
A steering control device that allocates feedforward and feedback axial forces at specific ratios based on the axial force difference, vehicle velocity, steering angle, and steering angular velocity to blend these forces appropriately, ensuring a more accurate application of the steering reaction force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reaction force motor is driven based on the control amount of the steering reaction force calculated from the steering angle and the control amount calculated by multiplying the electric current of the steering motor by a setting gain, then the steering reaction force reflects external forces on steered wheels, but the steering reaction force becomes inappropriate when the accuracy of the control amount based on steering angle degrades
Solution Approach 1:
The patent changes the parameters used for calculating steering reaction force from relying on steering angle to using steering wheel operating angular velocity and axial force. By detecting the operating angular velocity of the steering wheel and calculating axial force based on this velocity and detected axial force, the system maintains accurate steering reaction force control even when steering angle measurement accuracy degrades.
2Adaptability or versatility
If a fixed allocation ratio is used for blending feedforward and feedback axial forces, then the control system is simple, but the steering reaction force cannot be optimized for different driving conditions
Solution Approach 1:
The patent makes the allocation ratio dynamic by determining it based on the absolute value of the axial force difference between feedforward and feedback axial forces. When the axial force difference is large, a first allocation ratio is used; when the difference is small, a second allocation ratio is used. This dynamic adjustment allows the system to adapt to different driving conditions without requiring complex multi-parameter control logic.
Data Source
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AI summary
A control computing unit (11) blends a feedforward axial force (TFF) and a feedback axial force (TFB) at an allocation ratio (GF1, GF2, GF3, and GF4), based on an axial force difference, a lateral acceleration (Gy), a vehicle velocity (V), a steering angle (δ), and a steering angular velocity (dδ/dt) so as to set a final axial force. Then, the control computing unit (11) applies a steering reaction force based on the final axial force that has been set.