Hybrid Vehicle Engine Speed Control for Autonomous Stop Comfort
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Solution Overview
Problem
In hybrid vehicles, when slowing down and stopping in autonomous driving mode, frequent changes in engine rotation speed can cause discomfort for the driver due to varying lower limit rotation speeds, leading to potential rattle noise and muffled sound issues.
Innovation Solution
The hybrid vehicle incorporates a controller that sets the engine's lower limit rotation speed to a maximum value when operating under load in autonomous driving mode, ensuring stable operation within a higher range to minimize speed changes and reduce uncomfortable feelings, while also considering rattle noise conditions in normal driving mode by adjusting the rotation speed between two candidate speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the controlling lower limit rotation speed is changed multiple times to reduce rattle noise and muffled sound, then noise reduction is improved, but the engine rotation speed changes frequently causing driver discomfort
Solution Approach 1:
The system dynamically adjusts the controlling lower limit rotation speed based on driving mode. In autonomous driving mode, it maintains a fixed maximum value to ensure comfort, while in normal driving mode, it can switch between multiple values to reduce noise, making the control strategy adaptive to different operational contexts
Solution Approach 2:
Different control strategies are applied to different driving modes. The system treats autonomous driving mode and normal driving mode differently, applying a comfort-oriented fixed rotation speed in autonomous mode and a noise-oriented variable rotation speed in normal mode, optimizing performance for each specific context
2Ease of operation
If the engine rotation speed is stabilized to reduce driver discomfort, then driver comfort is improved, but the ability to reduce rattle noise and muffled sound deteriorates
Solution Approach 1:
The control strategy is made dynamic by detecting the driving mode and adjusting the rotation speed control accordingly. The system switches between comfort-priority and noise-priority modes, allowing it to stabilize rotation speed when needed while maintaining the ability to adjust for noise reduction when appropriate
Solution Approach 2:
The system changes the controlling lower limit rotation speed parameter based on driving mode detection. By modifying this key parameter, the system achieves different control outcomes: fixed maximum value for comfort in autonomous mode, and variable values for noise reduction in normal mode
Data Source
AI summary
A hybrid vehicle includes an engine, a motor, and a controller. The controller is configured to control the engine and the motor. The controller is configured to, when the engine is operated under load at the time when the vehicle slows down and stops in an autonomous driving mode in which the vehicle runs without driver's operation, set a controlling lower limit rotation speed of the engine to a maximum rotation speed out of a plurality of candidate rotation speeds and control the engine such that the engine is operated under load within a range higher than or equal to the controlling lower limit rotation speed.