Freewheel Control for Fuel Savings on Steep Downhills
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Solution Overview
Problem
Current vehicle systems with freewheel functionality do not adequately minimize fuel consumption when transitioning from moderate to steep downhill slopes, as they fail to optimize freewheel inactivation timing based on road topography and vehicle conditions.
Innovation Solution
A method that predicts the vehicle will encounter a steeper downhill slope and simulates fuel consumption with the freewheel function active or inactive, inactivating it before entering the steeper slope if simulation shows reduced fuel use, and adjusts engine connection and gear selection for optimal braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the freewheel function is activated during moderate downhill to save fuel, then fuel consumption decreases, but the vehicle cannot handle steep downhill slopes effectively
Solution Approach 1:
The system predicts upcoming steep downhill slopes using navigation data and road gradient information before the vehicle actually encounters them. This preliminary detection allows the control unit to deactivate the freewheel function in advance, ensuring the engine is ready to provide braking force when needed, thus preventing loss of vehicle control while still allowing freewheel operation during safe moderate downhill sections
Solution Approach 2:
The control unit continuously monitors vehicle speed, engine load, and predicted road gradient to dynamically adjust freewheel status. When vehicle speed exceeds safe limits or the predicted gradient indicates an upcoming steep section, the system provides feedback to deactivate freewheel operation, creating a closed-loop control system that balances fuel savings with vehicle safety
2Reliability
If the freewheel function is deactivated before entering steep downhill to ensure safety, then vehicle control capability is maintained, but fuel consumption increases
Solution Approach 1:
By using navigation system data and stored road gradient information, the system performs preliminary assessment of upcoming terrain before the vehicle reaches critical sections. This allows optimal timing of freewheel deactivation - early enough to ensure safety but late enough to maximize fuel-saving opportunities during moderate downhill segments
Solution Approach 2:
The system changes the operational parameter of the freewheel function based on predicted road gradient and vehicle conditions. Instead of a fixed on/off state, the freewheel function dynamically adjusts its status based on real-time parameters including predicted gradient, current speed, and engine capabilities, optimizing the balance between fuel efficiency and safety
3Speed
If the vehicle brakes to reduce speed before entering steep downhill, then vehicle speed is controlled, but fuel consumption increases and braking distance is extended
Solution Approach 1:
The system prepares the engine for upcoming braking needs by deactivating freewheel operation in advance of steep downhill sections. This preliminary engine engagement allows smoother speed control and reduces the need for aggressive braking, as the engine is already positioned to provide gradual braking force rather than requiring sudden mechanical intervention
Data Source
Figure 1~2
Figure 3
AI summary
A method and device for controlling an automatic freewheeling function in a vehicle where a freewheeling function is active due to a prevailing freewheeling condition and where a control unit is programmed to: -predict that said vehicle soon will travel in a steep downhill slope (that is below of position B in figure 2) that is steeper compared to a prevailing downhill slope; -simulate if less fuel will be consumed if said freewheeling function is inactivated in a position D (which is positioned above of said position B) before said vehicle enters said steeper downhill slope, compared to if said vehicle enters said steeper downhill slope with said freewheeling function active; -inactivate said freewheeling function in said position D, that is, before said vehicle enters said steeper downhill slope if said simulation shows that less fuel will be consumed.