Steering Control Device Dynamic Return Torque
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Solution Overview
Problem
Related-art steering control devices fail to appropriately adjust target return speed or return torque based on the vehicle's turning state when the driver releases or turns back the steering wheel, leading to discomfort and inefficient steering wheel return.
Innovation Solution
A steering control device with an actuator, vehicle turning state detection, steering-holding determination, storage, and assist torque calculation sections, which calculates and applies steering assist torque based on the absolute value of the steering-holding determination state amount to adjust assist torque dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the target return speed is set to be larger as the steering angle becomes larger, then the steering wheel can return to the neutral position more quickly at large steering angles, but the road surface reaction torque and return torque act together causing the actual steering speed to be abruptly increased
Solution Approach 1:
The patent applies dynamics by making the target return speed variable rather than fixed. The control unit dynamically adjusts the target return speed based on the current steering angle, using a lookup table that maps steering angle values to corresponding target return speeds. This allows the system to adapt the return speed to the current steering state, achieving fast return at large angles while preventing abrupt increases through controlled variable adjustment.
Solution Approach 2:
The patent changes the parameter of target return speed based on the steering angle. By using a lookup table to determine target return speeds corresponding to different steering angle ranges, the system adjusts this key parameter dynamically. This parameter change enables the steering wheel to return at appropriate speeds for different steering conditions, resolving the contradiction between fast return and smooth control.
2Force
If the target return speed is set to 0 at small steering angles, then the steering assist torque is reduced, but the steering wheel may not return to the neutral position because the road surface reaction torque is insufficient
Solution Approach 1:
The patent changes the target return speed parameter based on steering angle to resolve this contradiction. At small steering angles, the system sets an appropriate non-zero target return speed that matches the limited road surface reaction torque capability. This parameter adjustment ensures the steering wheel can reliably return to the neutral position while the steering assist torque remains appropriately controlled, preventing excessive force application.
Solution Approach 2:
The system uses feedback from the steering angle sensor to determine the current steering angle and subsequently select the appropriate target return speed from the lookup table. This feedback mechanism ensures that the target return speed is always appropriate for the current steering state, guaranteeing reliable return to neutral position while maintaining appropriate torque levels.
3Speed
If the steering assist torque is increased to improve steering wheel return characteristics, then the steering wheel returns faster, but the driver may have a feel of discomfort due to abrupt torque changes
Solution Approach 1:
The patent applies dynamics by making the steering assist torque variable rather than constant. The control unit dynamically adjusts the steering assist torque based on the current steering angle and the corresponding target return speed from the lookup table. This dynamic adjustment allows the system to provide appropriate torque for fast return while avoiding abrupt changes that would cause driver discomfort, as the torque evolves smoothly with the steering state.
Solution Approach 2:
The system changes the steering assist torque parameter based on the steering angle and target return speed. By using the lookup table to determine appropriate torque levels for different steering angles, the system adjusts this parameter smoothly rather than abruptly. This parameter change strategy achieves fast steering wheel return while maintaining driver comfort through controlled, progressive torque application.
Data Source
AI summary
Provided is a steering control device, including: an actuator for applying a steering assist torque to a steering system of a vehicle; a vehicle turning state detection section for detecting a state amount representing a turning state of the vehicle; a steering-holding determination section for determining a steering-holding state of the steering system; a storing section for storing, when the steering-holding determination section determines that the steering system is in the steering-holding state, the state amount detected by the vehicle turning state detection section as a steering-holding determination state amount; a steering assist torque calculation section for calculating the steering assist torque based on an absolute value of the steering-holding determination state amount; and an actuator control section for controlling the actuator based on the calculated steering assist torque.