Steering Control Device Partial Release Control
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Solution Overview
Problem
The existing electric power steering systems (EPS) face a challenge in maintaining small-turn performance due to end contact relaxation control, which limits the rack shaft movement to a virtual end position closer to the neutral steering position, resulting in a larger minimum turning radius and potential deterioration in vehicle handling.
Innovation Solution
A steering control device that includes an absolute steering angle detecting unit and a current command value calculating unit, which performs partial release control to decrease the correction value of the current command value when the vehicle is turning, allowing the turning shaft to move to the actual end position and preventing sudden changes in the current command value, thereby improving steering feeling and reducing the risk of a catching feeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If end contact relaxation control is performed to relax the impact of end contact, then the impact of end contact is reduced, but the rack shaft movement is limited to a virtual end position closer to the neutral steering position, resulting in a larger minimum turning radius and deterioration in small-turn performance
Solution Approach 1:
The patent applies dynamics by making the end contact relaxation control adaptive rather than static. The control adjusts the correction value of the current command value based on real-time detection of turning intentions through steering torque and steering angle changes. When turning is detected, the system dynamically reduces the correction value to allow the rack shaft to reach the actual end position, thereby maintaining small-turn performance while still providing end contact relaxation during normal steering operations.
Solution Approach 2:
The patent changes the parameter of the current command value correction dynamically. Instead of applying a fixed correction value, the system adjusts the correction value based on driving conditions. When turning is detected through monitoring steering torque and steering angle changes, the correction value is reduced, allowing the rack shaft to move to the actual end position and maintain proper turning performance.
2Object-affected harmful factors
If end contact relaxation control is performed to limit rack shaft movement to a virtual end position, then end contact impact is relaxed, but the steering angle is reduced, resulting in a larger minimum turning radius
Solution Approach 1:
The system dynamically adjusts the virtual end position based on detected turning intentions. When turning is detected through steering torque and steering angle changes, the control allows the rack shaft to reach the actual end position rather than being limited to the virtual end position, thereby reducing the minimum turning radius while maintaining end contact relaxation during normal steering.
Solution Approach 2:
The patent changes the parameter of the virtual end position dynamically. The control value for limiting rack shaft movement is adjusted based on driving conditions. When turning is detected, the system modifies the end position limitation parameter to allow full travel to the actual end position, thereby reducing the minimum turning radius while maintaining end contact relaxation during normal operations.
3Ease of operation
If partial release control is performed to decrease the correction value of current command value, then the rack shaft can move to the actual end position, but sudden changes in current command value may cause catching feeling
Solution Approach 1:
The patent applies dynamics by making the partial release control adaptive. The system dynamically adjusts the correction value based on real-time detection of turning intentions through steering torque and steering angle changes. When turning is detected, the control selectively reduces the correction value to allow the rack shaft to reach the actual end position, thereby improving small-turn performance while preventing sudden changes that would cause catching feeling through smooth, condition-based adjustments.
Data Source
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AI summary
A steering control device (1) includes: an absolute steering angle detecting unit (53) configured to detect an absolute steering angle; and a current command value calculating unit (51) configured to calculate a current command value corresponding to a target value of the motor torque output from the motor (21). The current command value calculating unit (51) is configured to perform partial release control for decreasing a correction value of the current command value due to execution of the end contact relaxation control when a vehicle is tried to be turned at the time of execution of the end contact relaxation control. The current command value calculating unit (51) is configured to stop the partial release control when the current command value which is calculated at the time of execution of the partial release control is a value which is not affected by decreasing the correction value based on execution of the partial release control.