Electric Power Steering Control for Smooth Torque Limiting
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Solution Overview
Problem
Existing driver assistance systems with electric power steering often fail to smoothly limit additional steering torque, leading to abrupt changes that can disturb drivers, especially when threshold limit values are suddenly reached, causing safety concerns and discomfort.
Innovation Solution
A method and device that calculate an intermediate correction driver support value, compare it to an assistance limit, and apply a limiting factor less than one to smoothly limit the correction driver support value, with the assistance limit and limiting factor adjusted based on vehicle speed, steering angle, and steering torque to adapt to different driving situations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed threshold limit value is used to limit additional steering torque, then the device complexity is reduced, but the driver comfort deteriorates due to sudden disturbances when the limit is reached
Solution Approach 1:
The patent applies dynamics by making the threshold limit value variable rather than fixed. The threshold is dynamically adjusted based on vehicle speed, with higher thresholds allowed at lower speeds where driver corrections are more common. This resolves the contradiction by maintaining simple control logic while improving driver comfort through adaptive threshold values that prevent sudden disturbances.
2Reliability
If the additional steering torque is abruptly limited at a fixed threshold, then the reliability of the assistance system is improved by preventing excessive torque, but the driver comfort deteriorates due to sudden changes in steering feel
Solution Approach 1:
The patent implements beforehand cushioning by preparing a buffer value that is stored and used to smoothly limit the additional steering torque when the threshold is reached. Instead of abruptly cutting off assistance, the buffer value provides a gradual transition, maintaining system reliability while preventing sudden changes in steering feel that would disturb the driver.
3Productivity
If the driver assistance device demand value is fully applied, then the productivity of steering correction is improved, but the driver control authority deteriorates as the driver cannot overturn system proposals
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the threshold limit value based on vehicle speed. At lower speeds where drivers frequently need to correct lane keep assistant deviations, higher threshold values are allowed, enabling full driver control authority. At higher speeds, lower thresholds maintain correction effectiveness while preventing excessive torque. This resolves the contradiction by adapting the assistance level to driving conditions.
Data Source
AI summary
An electric power steering system may be controlled by superimposing a driver demand and a driver assistance device demand value to calculate a driver requested support value, in which a virtual driver support value may be calculated based on driver demand and a correction driver support value may be calculated based on a driver assistance device demand value, and the driver requested support value may be calculated as a combination of the virtual correction driver support value and the virtual driver support value.