Hybrid Engine Stop Torque Control for Reverse Rotation Risk
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Solution Overview
Problem
Hybrid electric vehicles face challenges in efficiently managing engine stop processes due to reverse engine rotation, which can decrease battery charge and increase vibration, especially as motor torque increases and rotational speed decreases.
Innovation Solution
A method and system for controlling engine stop in hybrid electric vehicles that involves determining conditions for engine stop and rotational energy recovery, applying negative torque based on engine rotational speed, predicting reverse rotation, and applying feedback torque to maintain target behavior, thereby improving energy recovery and reducing vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If motor torque is increased to improve rotational energy recovery, then battery charge amount increases, but engine rotational speed decreases rapidly increasing reverse rotation risk
Solution Approach 1:
The control method applies preliminary countermeasures by predicting reverse rotation occurrence before it actually happens. The controller calculates predicted rotational speed and compares it with a predetermined threshold to anticipate reverse rotation risk, then adjusts motor torque in advance to prevent the harmful effect of reverse rotation while maintaining efficient energy recovery.
Solution Approach 2:
The control method implements feedback control by continuously monitoring actual engine rotational speed, comparing it with predicted rotational speed, and adjusting motor torque based on the deviation. When reverse rotation is detected or predicted, the controller provides feedback to reduce motor torque or apply positive torque, ensuring the engine maintains reliable operation without reverse rotation.
2Productivity
If motor torque is increased to maximize battery charging, then energy recovery efficiency improves, but engine control complexity increases
Solution Approach 1:
The control method performs preliminary calculations of predicted rotational speed using a predetermined model before actual engine stop occurs. By preparing the prediction in advance and comparing it with thresholds, the system simplifies the control logic during critical moments while maintaining high charging efficiency through pre-computed torque adjustments.
Solution Approach 2:
The control method manages complexity by changing control parameters dynamically - using predicted rotational speed as a key parameter to determine control strategy. The system switches between different control modes (normal energy recovery vs. reverse rotation prevention) based on parameter thresholds, simplifying decision-making while optimizing both charging efficiency and control reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances motor torque for rotational energy recovery, increases battery charge, improves fuel efficiency, and allows for quicker engine stop while mitigating reverse rotation, thus enhancing the overall efficiency of engine stop control.
Implementation Method 1
the motor may recover rotational energy maintained by the inertia of the engine after stopping fuel injection
Implementation Method 2
the engine can be stopped by outputting the torque, so-called the negative torque, which rotates in the opposite direction to the rotational direction of the engine through the motor
Implementation Method 3
the rotational speed of the engine determined by a detection result of at least one sensor
Data Source
AI summary
Disclosed is a hybrid electric vehicle and a method of controlling an engine stop for the vehicle. The method includes: determining whether a first condition and a second condition is satisfied; applying a negative torque to the motor when the first condition and the second condition are satisfied; predicting occurrence of reverse rotation of the engine; and applying a feedback torque for satisfying the target behavior of the engine to the motor when the occurrence of the reverse rotation is predicted.