Steering Column Jerk Reduction During Engine Restart
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Solution Overview
Problem
The existing automatic stop/start systems in motor vehicles with electric or electrohydraulic steering assistance cause discomfort due to jolts in the steering column during engine restarts, as the steering assistance is affected by voltage drops during automatic engine restarts, particularly at steering wheel positions close to stops, leading to hardening and jerking sensations.
Innovation Solution
A method to manage steering assistance by maintaining a level below the saturation value during automatic engine stop phases, which is determined iteratively based on vehicle parameters, steering wheel angle, and temperature, ensuring continuity of assistance during restarts and minimizing voltage drop effects, thereby reducing jolts and maintaining driver comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If steering assistance is maintained at nominal level during automatic engine stop phase, then driver comfort is improved, but voltage drop during restart causes steering column hardening and jerking
Solution Approach 1:
The control unit determines a saturation value for steering assistance before the automatic engine restart occurs, based on predicted voltage drop. By preemptively reducing the steering assistance level to this saturation value during the stop phase, the system prepares for the upcoming voltage drop, ensuring that steering assistance remains stable and comfortable during restart without causing hardening or jerking sensations.
2Reliability
If steering assistance is reduced during automatic stop phase, then steering column hardening and jerking are reduced, but driver comfort deteriorates
Solution Approach 1:
The control unit dynamically adjusts the steering assistance parameter by determining a saturation value that is lower than the nominal assistance value but optimized to maintain driver comfort. This saturation value is calculated based on vehicle parameters, steering wheel angle, and temperature, creating an optimal balance between preventing voltage drop effects and maintaining ease of operation during the automatic stop phase.
3Device complexity
If constant gain coefficient is applied to reduce steering assistance, then implementation is simplified, but optimal reduction cannot be achieved for varying steering conditions
Solution Approach 1:
Instead of using a constant gain coefficient, the control unit dynamically determines a saturation value for steering assistance that adapts to varying steering conditions. The saturation value is calculated based on real-time parameters including steering wheel angle, vehicle speed, and temperature, allowing the system to optimize steering assistance reduction for each specific operating condition rather than applying a fixed reduction strategy.
4Reliability
If steering assistance is reduced below saturation value, then voltage drop effects are minimized, but steering support becomes insufficient at critical moments
Solution Approach 1:
The control unit precisely determines the saturation value as an optimal threshold that prevents excessive reduction of steering assistance. By calculating this saturation value based on vehicle parameters and operating conditions, the system ensures that steering assistance is reduced enough to minimize voltage drop effects during restart, but not so much that steering support becomes insufficient. The saturation value acts as a lower bound that maintains adequate steering support force.
Data Source
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AI summary
The invention relates to a method for controlling power steering in a motor vehicle equipped with an internal combustion engine (13), comprising: an automatic engine stop/start system; and an electric or electro-hydraulic power steering system (12), characterised in that, during an automatic engine stop phase of an automatic stop/start sequence, the method permits a power steering level below a saturation value (A) that is lower than a nominal power steering value, said level being adapted to be maintained during the automatic engine start phase.