Steering Torque Control Using Road Reaction Frequency Separation
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Solution Overview
Problem
Conventional steer-by-wire vehicle steering devices fail to accurately reflect road surface reaction forces to drivers, as they only detect absolute values exceeding a threshold, neglecting the characteristics of road surface forces, which can lead to inadequate steering reaction forces, especially on varying road surfaces.
Innovation Solution
A vehicle steering device with a control unit that separates road surface reaction forces into low-frequency and high-frequency components, applies level restrictions, and generates a torque signal to adjust the steering torque based on these components, ensuring appropriate steering reaction forces are provided according to road surface conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If road surface reaction force is detected and reflected in steering reaction force using a threshold value, then steering reaction force can be controlled for excessive road surface reaction force, but frequency components of road surface reaction force are not considered and steering reaction force cannot be appropriately adjusted for different road surface characteristics
Solution Approach 1:
The patent segments the road surface reaction force signal into multiple frequency components using frequency separation technology. This allows different frequency components to be processed independently with different gain values, enabling the system to adapt to different road surface characteristics (such as unpaved roads versus paved roads) while maintaining reliable steering reaction force control.
2Ease of operation
If steering reaction force is set to a constant value when road surface reaction force exceeds threshold, then wheel operation interference is reduced, but road surface situation information is lost and steering reaction force accuracy deteriorates
Solution Approach 1:
The patent changes the parameter of steering reaction force from a constant value to a variable value based on frequency components. By calculating different gain values for different frequency components and applying them selectively, the system maintains ease of wheel operation while improving steering reaction force accuracy to reflect actual road surface conditions.
3Device complexity
If only absolute value of road surface reaction force is detected, then control is simplified, but frequency component information is lost and road surface situation reflection is inadequate
Solution Approach 1:
The patent extracts frequency component information from the road surface reaction force signal using frequency separation. This extraction process separates the signal into different frequency bands, allowing the system to retain essential road surface information while maintaining relatively simple control structure through independent gain adjustment for each frequency component.
Data Source
AI summary
A vehicle steering device includes a target steering torque generation unit configured to generate target steering torque for a reaction force motor, and a torque correction value calculation unit configured to generate a torque signal Tref_p in accordance with road surface reaction force acting on a steering wheel of a vehicle. The torque correction value calculation unit generates the torque signal Tref_p by separating estimated road surface reaction force into a low-frequency component and a high-frequency component, providing level restriction on each of the low-frequency component and the high-frequency component, and adding torque values converted from the low-frequency component and the high-frequency component after the level restriction. The target steering torque generation unit generates the target steering torque by adding the torque signal Tref_p and a torque signal Tref_a generated based on a predetermined basic map in accordance with at least a vehicle speed and a steering angle of the vehicle.