Vehicle Speed Control Using Gravity Braking on Slopes
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Solution Overview
Problem
Existing methods for regulating vehicle speed using engine-off technology are limited in applicability and do not effectively reduce fuel consumption across various driving conditions.
Innovation Solution
A method that determines necessary conditions such as speed and slope thresholds to trigger engine-off driving, using gravity to brake the vehicle on ascending slopes, and switches to hydraulic braking when exiting the slope, ensuring the engine-off period is not too short to optimize fuel savings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is cut off downhill to regulate speed, then fuel consumption is reduced, but the method can only be used in very specific cases
Solution Approach 1:
The patent extends the engine-off method from only downhill use to also include ascending slopes. The control system evaluates multiple conditions (slope gradient, vehicle speed, acceleration requests) to determine when engine-off can be applied, making the fuel-saving technique applicable to a broader range of driving scenarios including both downhill and uphill conditions.
Solution Approach 2:
The patent introduces multiple parameter thresholds (slope threshold between 2.5%-3.5%, speed threshold between 15-25 km/h, derivative threshold between 1.5-2.5%/s) to dynamically control engine-off duration. By adjusting these parameters based on road gradient and vehicle state, the system optimizes fuel savings while maintaining adaptability to different slope conditions.
2Use of energy by moving object
If the engine is run off for a short time, then fuel is saved, but the fuel saving effectiveness is reduced
Solution Approach 1:
The control system performs preliminary evaluation of road gradient, vehicle speed, and acceleration requests before triggering engine-off. It predicts whether the slope is sufficient to maintain vehicle speed without engine power, and only initiates engine-off when conditions are favorable, ensuring the maneuver will be effective before committing to it.
Solution Approach 2:
The system continuously monitors vehicle speed, slope gradient, and driver acceleration requests during engine-off operation. If the vehicle speed drops below the setpoint or the driver requests acceleration, the system immediately restarts the engine. This feedback mechanism ensures engine-off duration is optimized for fuel savings while maintaining acceptable performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for efficient speed regulation and significant fuel savings by using gravity for braking on slopes and transitioning to hydraulic braking when necessary, reducing wear on brake pads and minimizing short engine-off periods.
Implementation Method 1
Such a method makes it possible to regulate the speed by running the engine off when climbing in order to use gravity to brake the vehicle
Data Source
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AI summary
This method for regulating the speed of a vehicle around a setpoint speed, comprises determining (E01, E02, E03) a set of necessary conditions and triggering (E04) of a step of driving with the engine switched off depending on the set of necessary conditions. The set of necessary conditions comprises the engagement of the vehicle on an uphill slope at a current speed higher than the setpoint speed.