Electric Power Steering Torque Limiting via Variable Factor
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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 limits are suddenly reached, causing safety concerns and discomfort.
Innovation Solution
A method that calculates an intermediate correction driver support value and applies a limiting factor, which is determined by vehicle speed, steering angle, and steering torque, to smoothly limit the additional steering torque, ensuring the driver maintains control and minimizing disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed threshold limit is applied to limit the additional steering torque, then the driver assistance is controlled, but sudden disturbances occur when the limit is reached
Solution Approach 1:
The patent applies dynamics by making the limiting factor variable rather than fixed. The limiting factor changes continuously based on driving conditions (vehicle speed, steering angle, steering torque), transforming the static threshold limit into a dynamic adaptive limit that smoothly adjusts to prevent abrupt disturbances while maintaining control reliability
Solution Approach 2:
The patent changes parameters by introducing a variable limiting factor that depends on multiple driving parameters (vehicle speed, steering angle, steering torque). This parameter change approach allows the system to adapt the assistance limit continuously, avoiding sudden threshold crossings that cause driver disturbance while maintaining reliable control
2Reliability
If the additional steering torque is limited abruptly to ensure driver control, then safety is improved, but driving comfort deteriorates
Solution Approach 1:
The patent uses dynamics to create a smooth transition in torque limiting. By making the limiting factor variable and continuously adjustable based on driving conditions, the system maintains driver control authority while avoiding abrupt torque changes that would reduce driving comfort
Solution Approach 2:
The patent applies beforehand cushioning by preparing a variable limiting factor that anticipates driving conditions. The system pre-adapts the assistance limit based on current driving parameters, cushioning against potential abrupt changes before they occur, thereby maintaining both driver control and comfort
Data Source
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AI summary
A method of operating an electric power steering system, applicable for superimposing a driver demand (12) and a driver assistance device demand value (16) to calculating a driver requested support value (13), wherein a virtual driver support value (23) is calculating on basis of the driver demand (12) and a correction driver support value (26) is calculating on basis of a driver assistance device demand value (16) and the driver requested support value (13) is calculating as combination of the virtual correction driver support value (26) and the virtual driver support value (23), characterized in that, that the correction driver support value (26) is calculating by following steps: ° calculating an intermediate correction driver support value (25) on basis of the driver assistance device demand value (16); ° comparing the absolute value of the intermediate correction driver support value (25) with a assistance limit (TROmax); ° if the absolute value of the intermediate correction driver support value (25) exceeds the assistance limit (TROmax) than multiplying the intermediate correction driver support value (25) with a limiting factor (k) to get the correction driver support value (26), wherein the limiting factor (k) has a value, which is less than one and higher or equal than zero, ° if the absolute value of the intermediate correction driver support value (25) is less than the assistance limit (TROmax) than set the correction driver support value (26) as to the intermediate correction driver support value (25).