Coasting Control System Using Virtual Engine RPM for Downshifting
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Solution Overview
Problem
During Neutral Coasting Control (NCC) and Start Stop Coasting (SSC), drivers face challenges in downshifting appropriately, leading to engine stop, engine malfunction, and poor reacceleration performance due to unstable engine RPM when the clutch is engaged, as they lack intuitive guidance on suitable gear changes based on vehicle speed.
Innovation Solution
A coasting driving control method and system that determines a virtual engine RPM or virtual gear ratio using engine RPM, vehicle speed, and gear stage information to provide downshifting instructions, allowing for appropriate gear changes by outputting signals to the driver, either visually or audibly, to prevent engine issues and ensure smooth reacceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the clutch is moved to a neutral position for coasting control, then fuel efficiency is improved by maximizing coasting distance, but the driver cannot intuitively determine appropriate downshifting timing leading to engine stop or malfunction
Solution Approach 1:
The system calculates virtual engine RPM based on vehicle speed, gear stage, and engine characteristics, then provides feedback to the driver through the cluster display when virtual RPM approaches idle RPM. This feedback mechanism guides the driver on when to downshift, preventing engine stop while maintaining coasting efficiency.
Solution Approach 2:
The patent introduces an intermediary calculation system that computes virtual engine RPM as a mediator between the neutral clutch position and the driver's downshifting decision. This virtual RPM value represents the estimated engine state during coasting, enabling the driver to make informed gear changes without directly sensing engine behavior.
2Device complexity
If the driver manually downshifts during coasting based on intuition, then the system remains simple, but engine RPM becomes unstable causing engine malfunction and poor reacceleration performance
Solution Approach 1:
The system performs self-service by automatically calculating virtual engine RPM and generating downshifting guidance signals without requiring additional complex hardware. The controller utilizes existing vehicle parameters (speed, gear stage) and pre-stored engine characteristics to provide reliability-enhancing guidance, maintaining simplicity while improving engine operation stability.
3Reliability
If virtual engine RPM calculation is implemented to guide downshifting, then engine operation reliability is improved, but calculation complexity and processing requirements increase
Solution Approach 1:
The system applies preliminary action by pre-storing engine characteristics data (displacement, compression ratio, intake manifold volume) before coasting occurs. During coasting, the controller directly utilizes these pre-stored parameters in the virtual RPM calculation formula, avoiding complex real-time measurements and reducing processing complexity while maintaining calculation accuracy for reliable engine operation.
Data Source
AI summary
A coasting driving control method and system for a vehicle may determine virtual engine RPM for a current driving state using engine RPM, vehicle speed, and gear stage information by a controller when coasting is started with the clutch in the neutral position and outputs a downshifting instruction signal for a gear stage by the controller when the virtual engine RPM is less than a coasting engine RPM which is greater than an idling RPM by a predetermined value.