Active Steering Return Control via Dynamic Rack Force Adaptation
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Solution Overview
Problem
Modern steering systems struggle to implement an active return that adapts to the current driving situation, particularly in cornering or transition areas where returning the steering wheel to the center position can destabilize the vehicle.
Innovation Solution
The method determines the target steering wheel angular velocity based on the current rack force, which is influenced by lateral forces, allowing the target angle to be set to a stabilizing, lateral force-free position, and corrects for road bumps to prevent unwanted movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the steering wheel is returned to the center position using a fixed target angle, then the active return function is simple to implement, but the vehicle stability is compromised in cornering or transition areas
Solution Approach 1:
The patent implements dynamic adaptation by making the target steering angle variable based on rack force measurements. Instead of a fixed center position, the target angle dynamically adjusts according to the current driving situation, allowing the system to adapt to cornering and transition areas while maintaining implementation feasibility through a straightforward control loop.
Solution Approach 2:
The system employs feedback control by continuously measuring the rack force and using this information to adjust the target steering angle. The control unit monitors the actual steering wheel angular velocity, compares it with the target value, and generates appropriate steering torque to achieve the desired return behavior adapted to current conditions.
2Measurement precision
If the target steering wheel angular velocity is determined as a function of steering wheel angle, then the control implementation is straightforward, but the target angle does not correspond to the stabilizing angle in transition areas
Solution Approach 1:
The patent uses rack force as an intermediary parameter that indirectly provides information about the stabilizing steering angle. Instead of directly measuring or calculating the complex vehicle dynamics parameters, the system measures rack force which naturally reflects the current driving situation and lateral forces, making the determination of accurate target angles more feasible.
Solution Approach 2:
The system replaces direct mechanical angle sensing with a force-based measurement approach. By measuring rack force and using it to determine the target steering angle, the system substitutes a simpler force measurement for more complex angle determination methods, improving accuracy while managing measurement difficulty.
3Reliability
If road bumps are not corrected for, then the active return response is fast and direct, but unwanted steering wheel movements and driver irritation occur
Solution Approach 1:
The system performs preliminary correction of rack force measurements to account for road bumps before using these values to determine the target steering angle. By pre-compensating for disturbance forces in the rack force measurement, the system prevents unwanted steering wheel movements and driver irritation while maintaining reliable and responsive active return behavior.
Data Source
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AI summary
The method involves comparing a reference-steering angle speed with an initial-steering angle speed. Resetting moment is determined in dependent on the result of comparison of angle speeds. An actual gear rod force is determined in dependent on steering moment acting in a steering system (1), and the reference-steering angle speed is determined in dependent on the actual gear rod force. Unevenness of a road surface that influences the actual gear rod force is unconsidered, during the determination of the reference-steering angle speed. Independent claims are also included for the following: (1) a control device for controlling and/or regulating a steering device in a vehicle (2) a computer program, which is executable on the control device for controlling and/or regulating the steering device.