Dynamic Engine Stop-Start Control for Vehicle Stability
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Solution Overview
Problem
Existing vehicle control systems with idling-stop functions face challenges in safely managing engine stop-and-restart operations, particularly on inclined road surfaces, which can lead to unexpected vehicle movements due to inadequate integration with cruise control and failure in sensing conditions.
Innovation Solution
A control unit that integrates an automatic engine stop-and-restart system with a following-cruise control unit, utilizing gradient sensors, vehicle speed sensors, and brake control units to modify stop and restart conditions based on road gradient, vehicle speed, and driver inputs, ensuring safe engine management during idling-stop and following-cruise operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the engine stop conditions include a relatively lenient gradient threshold to allow idling-stop on mild inclines, then fuel consumption is reduced, but vehicle stability deteriorates on steeper slopes
Solution Approach 1:
The gradient threshold for engine stop conditions is made dynamic rather than fixed. The control unit adjusts the threshold based on real-time detection of road gradient by the gradient sensor. When a steep incline is detected, the threshold is raised to prevent idling-stop, while on mild inclines the threshold remains low to allow fuel-saving stops. This dynamic adaptation resolves the contradiction between fuel efficiency and vehicle stability.
2Speed
If the engine restarts automatically based on vehicle speed exceeding a threshold, then the vehicle responds quickly to driver intent, but unexpected movement occurs on downhill slopes during following-cruise control
Solution Approach 1:
The control unit continuously monitors road gradient via the gradient sensor and uses this feedback to modulate the engine restart conditions. During following-cruise control on downhill slopes, the system detects the negative gradient and suppresses automatic restart even if vehicle speed exceeds the threshold, preventing unexpected movement. On level or uphill roads, the normal speed-based restart logic applies, maintaining quick response to driver intent.
3Reliability
If the gradient threshold for engine stop is kept high to prevent instability on slopes, then vehicle stability is maintained, but fuel consumption increases due to reduced idling-stop opportunities
Solution Approach 1:
The system dynamically adjusts the gradient threshold based on real-time road conditions detected by the gradient sensor. On mild inclines where stability is not compromised, the threshold is set low to permit idling-stop and reduce fuel consumption. On steeper slopes where stability could be affected, the threshold is raised to prevent idling-stop. This dynamic adjustment optimizes the trade-off between fuel efficiency and vehicle stability across varying operating conditions.
4Reliability
If the system modifies restart conditions to exclude speed threshold detection during following-cruise control, then unexpected movement on downhill is prevented, but normal restart response is delayed
Solution Approach 1:
The restart conditions are dynamically modified based on the operational state of the following-cruise control and detected road gradient. When following-cruise is active and a downhill gradient is detected, the speed-based restart condition is suppressed to prevent unexpected movement. However, when following-cruise is inactive or the gradient is not downhill, the normal speed-based restart logic remains active, ensuring quick restart response and minimizing time loss in normal operating conditions.
Data Source
AI summary
A control unit for a vehicle comprises an automatic engine stop-and-restart unit for stopping the engine responsive to predefined stop conditions and for restarting the engine responsive to predefined restart conditions, and a following-cruise control unit for controlling the vehicle to follow a vehicle ahead responsive to predefined following-cruise conditions. The automatic stop-and-restart unit for stopping and restarting the engine is configured to modify at least one of the stop conditions and the restart conditions during the following-cruise control.