Electric Power Steering Mode Switching Correction
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Solution Overview
Problem
Conventional electric power steering systems cause uncomfortable feelings for drivers when switching from automatic to manual steering control due to inverse motor current outputs, leading to a catching feeling and restricted steering freedom, especially when the steering torque is below the threshold.
Innovation Solution
An electric power steering apparatus with a target steering angle correcting section that calculates a correction value based on steering torque and vehicle speed, using phase compensation and dead band gain to adjust the target steering angle, ensuring the actual steering angle aligns with the corrected target, thereby reducing mode-switching interference and enhancing steering feel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the system switches from automatic to manual steering control mode, then the driver can take manual control, but the driver experiences uncomfortable feelings and catching feeling due to inverse motor current outputs
Solution Approach 1:
The control device calculates a corrected target steering angle by adding a correction amount to the target steering angle before mode switching occurs. This preliminary correction ensures that when the system transitions from automatic to manual control mode, the motor current output is already adjusted to match the driver's steering torque direction, eliminating the uncomfortable catching feeling and ensuring smooth transition.
2Stability of the object's composition
If the system maintains automatic steering control when steering torque is below threshold, then steering stability is maintained, but the driver loses steering freedom and feels restricted
Solution Approach 1:
The control device dynamically adjusts the correction amount based on the steering torque magnitude. When steering torque exceeds the threshold, the correction amount increases to enable smoother manual control transition. When steering torque remains below the threshold, the system maintains automatic control with appropriate correction, allowing the driver to feel steering freedom without compromising stability.
3Ease of operation
If the correction amount is increased to improve steering feel at low torque, then steering freedom is enhanced, but the system becomes more complex
Solution Approach 1:
The control device varies the correction amount as a parameter based on steering torque magnitude and vehicle speed. By using parameter changes rather than complex structural modifications, the system achieves improved steering feel at low torque conditions while maintaining relatively simple control logic. The correction amount is calculated using formulas that adjust based on torque thresholds and speed conditions.
Data Source
AI summary
[Problem] An object of the present invention is to provide a high-performance electric power steering apparatus that can smoothly switch a steering control mode with a simple structure and does not make a driver uncomfortable when the driver steers a handle in an automatic steering control.[Means for Solving the Problem] The present invention is the electric power steering apparatus that has a function, which switches between a manual steering control which drives a motor by the first motor current command value calculated based on at least a steering torque and an automatic steering control which drives the motor by the second motor current command value calculated at a steering angle control section so that an actual steering angle follows-up a target steering angle, comprising: a target steering angle correcting section that performs a calculation process for the steering torque depending on a steering state and vehicle speed and outputs a target steering angle correction value, and a correction outputting section that corrects the target steering angle by using the target steering angle correction value and inputs a corrected correction target steering angle into the steering angle control section.