Electric Vehicle Voltage Control via Output Shaft Torque
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Solution Overview
Problem
Existing electric vehicle motor drive control systems face deterioration in driveability due to rapid changes in the operating point of the electric motor, especially when a transmission is involved, as they struggle to follow rapid changes in rotational speed and torque, leading to temporary torque insufficiency and reduced efficiency.
Innovation Solution
An electric vehicle system that includes a transmission, a converter to regulate voltage, and an electronic control unit that determines the target voltage based on the torque and rotational speed of the output shaft, stabilizing the voltage and ensuring efficient operation by considering both torque and rotational speed states, and adjusting weights based on running load to balance driveability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the target value of the inverter input voltage is determined based on the operating point of the electric motor, then the motor can be efficiently driven, but the inverter input voltage cannot follow rapid changes in the operating point due to transmission shifting
Solution Approach 1:
The control system determines the target inverter input voltage based on the output shaft operating point (torque and rotational speed) before the motor operating point changes rapidly during transmission shifting. This preliminary action allows the voltage to be pre-adjusted according to the transmission ratio and anticipated motor requirements, enabling the voltage to follow rapid changes without waiting for the motor operating point to change first.
Solution Approach 2:
The output shaft operating point (torque and rotational speed) serves as an intermediary parameter that bridges the transmission shifting information and the inverter input voltage control. By using this intermediary, the system can infer motor requirements through the transmission ratio without directly responding to rapid motor operating point changes, thus stabilizing voltage control while maintaining efficiency.
2Adaptability or versatility
If the target voltage is rapidly adjusted to follow motor operating point changes, then the voltage can match motor requirements, but the voltage becomes unstable during transmission shifting
Solution Approach 1:
The system calculates the target voltage in advance based on the output shaft operating point before transmission shifting occurs. This preliminary calculation allows the voltage to be smoothly transitioned to new values without rapid fluctuations, maintaining stability while still adapting to changing motor requirements through the transmission ratio relationship.
Solution Approach 2:
The output shaft operating point acts as a stabilizing intermediary that filters out rapid motor operating point changes during transmission shifting. By controlling voltage based on this more stable parameter, the system achieves both adaptability to motor needs and stability during shifting operations.
3Stability of the object's composition
If the inverter input voltage does not follow rapid changes in motor operating point, then voltage stability is maintained, but the motor cannot produce desired torque temporarily
Solution Approach 1:
The control system proactively adjusts the inverter input voltage based on the output shaft operating point before the motor experiences torque deficiency. This preliminary voltage adjustment ensures that the motor receives appropriate voltage levels in advance, preventing torque output deficiencies while maintaining overall voltage stability during transmission shifting.
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 configuration effectively curbs driveability deterioration and reduces efficiency losses by stabilizing the target voltage, ensuring the electric motor can maintain desired torque and efficiently operate across varying load conditions.
Implementation Method 1
The converter is configured to regulate a voltage supplied to the drive unit
Data Source
AI summary
An electric vehicle includes an electric motor, a transmission, a drive unit, a converter, and an electronic control unit. The transmission is provided in a power transmission path between a rotary shaft of the electric motor and drive wheels of the electric vehicle. The drive unit is configured to drive the electric motor. The converter is configured to regulate a voltage supplied to the drive unit. The electronic control unit is configured to control the converter, and determine the voltage regulated by the converter, based on a first quantity of state associated with torque of an output shaft of the transmission, and a second quantity of state associated with a rotational speed of the output shaft.