Dynamic Speed Threshold for Automatic Engine Stop
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Solution Overview
Problem
Existing automatic engine stop systems, such as 'Sailing', face challenges in maintaining drivability and handling when engine shutdown occurs at high vehicle speeds during real driving conditions, as they do not adequately account for dynamic parameters like steering, road grade, and safety system activations.
Innovation Solution
A method for controlling automatic engine stop in automotive systems that calculates a dynamic speed threshold based on multiple driving parameters, including steering wheel angle, steering wheel rate, wheel speed difference, antilock braking system status, electronic stability control status, and road grade, allowing engine shutdown at non-zero speeds while ensuring safety and drivability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is shut off at high vehicle speed to reduce fuel consumption, then fuel economy is improved, but drivability and handling deteriorate
Solution Approach 1:
The patent applies dynamics by making the speed threshold dynamic rather than fixed. The threshold adapts in real-time based on steering wheel angle, steering wheel angle rate, wheel speed difference, and safety system status. This allows the system to enable engine shut-off at high speeds during straight driving while preventing shut-off during steering or unstable conditions, thus improving fuel economy without compromising drivability.
Solution Approach 2:
The patent changes the parameter of speed threshold from a static value to a dynamic value that varies with driving conditions. By monitoring parameters like steering wheel angle and wheel speed difference, the system adjusts the threshold to allow engine shut-off only when conditions are appropriate, resolving the contradiction between fuel savings and drivability.
2Use of energy by moving object
If the engine is shut off at high vehicle speed to reduce fuel consumption, then fuel economy is improved, but vehicle stability and safety deteriorate
Solution Approach 1:
The patent uses feedback by continuously monitoring steering wheel angle, steering wheel angle rate, wheel speed difference, and safety system status. This feedback mechanism allows the system to detect when the vehicle is in an unstable condition (e.g., steering, ABS activation, ESC activation) and adjust the speed threshold accordingly, preventing engine shut-off during critical moments and thus maintaining vehicle stability and safety.
Solution Approach 2:
The dynamic speed threshold adapts to real-time vehicle conditions, enabling the system to permit engine shut-off during stable straight driving while prohibiting it during unstable conditions such as steering or safety system activation, thereby resolving the contradiction between fuel economy and vehicle stability.
3Device complexity
If a fixed speed threshold is used for engine shut-off to simplify control, then device complexity is reduced, but adaptability to different driving conditions deteriorates
Solution Approach 1:
The patent implements a dynamic speed threshold that automatically adapts to different driving conditions based on monitored parameters. This dynamic approach significantly improves adaptability compared to a fixed threshold, while the added complexity is limited to the monitoring and calculation logic, which is manageable within modern automotive control systems.
Solution Approach 2:
The patent changes the speed threshold parameter from fixed to dynamic, allowing it to vary with driving conditions. This improvement in adaptability is achieved by monitoring parameters such as steering wheel angle and wheel speed difference, and adjusting the threshold accordingly, resolving the contradiction between control complexity and adaptability.
Data Source
AI summary
The present disclosure provides a method of controlling an automatic engine stop of an automotive system, during a coasting phase. A dynamic speed threshold is calculated as a minimum value of a plurality of dynamic speed values. Each dynamic speed value is calculated as a function of an automotive system parameter such as a steering wheel angle, a steering wheel angle rate, a wheel speed difference, an antilock braking system status, or an electronic stability control status (p5) and/or a road condition such as road grade. The automatic engine stop is enabled when a vehicle speed is lower than the dynamic speed threshold.