Hybrid Engine Auto-Start Control in Reverse Gear
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Solution Overview
Problem
Current automotive systems with automatic stop-start technology are not compliant with Federal Motor Vehicle Safety Standards (FMVSS) regarding engine shutdown and restart in reverse gear, as they may cause sudden torque boosts or disturbances during reverse driving.
Innovation Solution
A control strategy implemented by a controller that shifts the transmission into reverse gear while the brake pedal is unapplied and applies the electronic parking brake after a predetermined time, inhibiting engine restart until the brake pedal is applied, ensuring compliance with FMVSS and preventing unwanted torque boosts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the engine automatically restarts when the transmission shifts into reverse gear, then the vehicle is ready to move immediately, but sudden torque boosts occur causing disturbances during reverse driving
Solution Approach 1:
The controller applies the electronic parking brake in advance before allowing engine restart in reverse gear. This preliminary action prevents the torque boost disturbance by ensuring the vehicle is securely held before engine power is reapplied, eliminating the harmful effect while maintaining readiness.
2Object-affected harmful factors
If the engine remains stopped while in reverse gear to prevent torque boosts, then disturbance is minimized, but the vehicle cannot respond quickly when needed
Solution Approach 1:
The controller applies the electronic parking brake before engine restart, preparing the system in advance so that when the engine restarts, the vehicle is already secured and ready to move without disturbance or delay.
Solution Approach 2:
The controller continuously monitors transmission gear position and brake pedal status, using this feedback to determine when to apply the parking brake and when to permit engine restart, ensuring optimal timing that balances disturbance prevention with response readiness.
3Loss of energy
If the engine automatically restarts upon selecting reverse gear without brake application, then fuel economy is improved through stop-start operation, but FMVSS compliance is violated
Solution Approach 1:
The controller monitors brake pedal status as feedback and uses this information to determine whether to permit engine restart in reverse gear. When the brake pedal is unapplied, the controller applies the electronic parking brake and inhibits restart, ensuring FMVSS compliance while maintaining stop-start fuel savings when appropriate.
Data Source
AI summary
A stop/start hybrid vehicle includes an engine configured for stopping and restarting during travel, a multiple-ratio transmission, a brake pedal, and an electronic parking brake. The transmission can be shifted into reverse gear either when the brake pedal is applied or unapplied. At least one controller is programmed to control the vehicle under these scenarios. If the engine is off and the brake pedal is applied when the transmission is shifted into reverse, the controller restarts the engine. If the engine is off and the brake pedal is unapplied when the transmission is shifted into reverse, the controller inhibits the engine from restarting until the brake pedal is applied. The controller can also be programmed to apply the electronic parking brake while the brake pedal remains unapplied after a predetermined time from the transmission being shifted into the reverse gear.