Brake Effort Thresholds for Stop/Start Engine Control
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Solution Overview
Problem
Existing engine shutdown and restart systems in micro-hybrid vehicles face challenges in accurately determining when to shut down and restart the engine, leading to unintended shutdowns and restarts, which affects fuel economy and vehicle launch performance.
Innovation Solution
A vehicle system that uses a controller to shut down the engine based on brake effort exceeding a threshold and restarts it when the brake effort decreases below a specific threshold, both determined by estimated vehicle mass and road gradient, thereby anticipating vehicle hold and launch requests based on brake apply and release conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the engine is shutdown when wheel speed is zero and brake pedal is depressed, then fuel economy is improved, but unintended engine shutdowns occur affecting vehicle launch performance
Solution Approach 1:
The system performs preliminary detection of brake apply conditions before initiating engine shutdown. By monitoring brake pressure, wheel speed, and other parameters in advance, the system determines whether the vehicle is truly stationary and ready for shutdown, preventing unintended shutdowns that would compromise launch performance
Solution Approach 2:
The system continuously monitors multiple parameters including brake pressure, wheel speed, and vehicle motion to provide feedback on actual vehicle state. This feedback mechanism allows the system to distinguish between genuine stop conditions and transient states, ensuring engine shutdown only occurs when appropriate while maintaining reliable vehicle launch capability
2Speed
If the engine is restarted in anticipation of vehicle launch, then vehicle launch performance is improved, but unintended engine restarts occur reducing fuel economy
Solution Approach 1:
The system performs preliminary detection of brake release conditions before initiating engine restart. By monitoring brake pressure reduction, accelerator pedal position, and other parameters in advance, the system determines whether vehicle launch is truly anticipated, preventing unintended restarts that would reduce fuel economy
Solution Approach 2:
The system dynamically adjusts restart timing based on real-time evaluation of multiple changing parameters including brake pressure trajectory, accelerator pedal position, and vehicle motion state. This dynamic approach allows the system to optimize restart timing for each specific driving situation, improving launch performance when needed while avoiding unnecessary restarts that waste fuel
3Measurement precision
If multiple conditions are evaluated for engine shutdown and restart, then accuracy is improved avoiding unintended shutdowns and restarts, but system complexity increases
Solution Approach 1:
The system segments the control logic into distinct modules: brake apply condition evaluation, brake release condition evaluation, engine shutdown control, and engine restart control. Each module handles specific detection tasks independently, improving measurement precision through specialized processing while managing system complexity through modular architecture
Solution Approach 2:
The controller integrates multiple detection functions into a single multi-functional unit that evaluates brake pressure, wheel speed, vehicle motion, and other parameters simultaneously. This universal controller handles both shutdown and restart decisions using the same sensor inputs, improving detection accuracy through comprehensive monitoring while reducing overall system complexity by consolidating control functions
Data Source
AI summary
A vehicle is provided with an engine that is configured for automatic shutdown and restart. The vehicle is also provided with a controller that is configured to shutdown the engine in response to brake effort exceeding a first threshold and to restart the engine in response to brake effort decreasing below a second threshold. The first threshold and the second threshold are based on an estimated vehicle mass and a road gradient.