Hybrid Vehicle Driving Device Engine Speed Control
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Solution Overview
Problem
During batteryless travel control in hybrid vehicles, when the engine rotation speed exceeds the target speed, the engine rotation speed drops sharply due to feedback control and power balance control, leading to a breakdown in power balance.
Innovation Solution
A driving device with a controller that restricts the requested driving force when the engine rotation speed is higher than the target speed, using a planetary gear mechanism to connect the engine and electric machines, and switching control modes of the electric machines between pulse width modulation and rectangular wave control to maintain engine rotation speed, thereby preventing a drop in engine rotation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If engine feedback control and power balance control are executed simultaneously during batteryless travel control, then the engine rotation speed is regulated to target speed and power generation matches power consumption, but the engine rotation speed drops sharply when it exceeds target speed
Solution Approach 1:
The control strategy dynamically adjusts the target rotation speed based on the current engine rotation speed. When the engine rotation speed exceeds the target speed by a predetermined threshold, the target rotation speed is increased to match the current speed, preventing sharp drops. This dynamic adjustment resolves the contradiction by making the control system adaptive to real-time conditions.
Solution Approach 2:
The system continuously monitors the engine rotation speed and compares it with the target rotation speed. When the difference exceeds a threshold, the feedback mechanism triggers an adjustment of the target speed. This feedback loop ensures that the engine rotation speed is regulated smoothly without sharp drops while maintaining power balance.
2Reliability
If the first rotating electric machine generates power to balance power consumption during batteryless travel control, then power balance is maintained, but the engine rotation speed decreases due to the power generation torque
Solution Approach 1:
The target rotation speed is dynamically adjusted based on the operating conditions and the power balance requirements. When power generation by the first rotating electric machine would cause excessive engine rotation speed decrease, the target speed is raised to compensate, maintaining both power balance and adequate engine speed.
Solution Approach 2:
The system changes the parameter of target rotation speed based on the current operational state. By adjusting this parameter in response to power balance requirements and engine speed conditions, the system resolves the contradiction between maintaining power balance and preventing excessive engine speed decrease.
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
The solution effectively suppresses the drop in engine rotation speed and maintains power balance by restricting the requested driving force and adjusting control modes, preventing a breakdown in power balance during batteryless travel control.
Implementation Method 1
a planetary gear mechanism having a rotating element connected to the engine, a rotating element connected to the first rotating electric machine, and a rotating element connected to the second rotating electric machine, the planetary gear mechanism mechanically connecting the engine, the first rotating electric machine and the second rotating electric machine
Implementation Method 2
a first rotating electric machine; a second rotating electric machine connected to a driving wheel
Implementation Method 3
switching control modes of the electric machines between pulse width modulation and rectangular wave control to maintain engine rotation speed
Data Source
AI summary
A vehicle includes an engine, a first MG (motor generator), a second MG, a planetary gear mechanism provided among the engine, the first MG and the second MG, a battery, and an ECU. The ECU executes batteryless travel control when the battery is abnormal. The batteryless travel control includes engine F/B control for controlling a rotation speed of the engine to become a target rotation speed, and power balance control for controlling a requested driving force to be output and allowing a power generated by the first MG to become equal to a power discharged by the second MG. When the rotation speed of the engine is higher than a threshold speed higher by a prescribed value than the target rotation speed while the batteryless travel control is in execution, the ECU decreases the requested driving force.