EV Motor Torque Control Under Battery Current Limits
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Solution Overview
Problem
Existing electric vehicles face challenges in freely selecting and mounting various batteries and battery control circuits due to the need for current limiting functions to protect battery-related components, limiting flexibility and options.
Innovation Solution
A control method for electric vehicles that sets a current-related upper limit value based on the vehicle state and calculates a torque upper limit value for the motor to ensure the current flowing through the battery remains within this limit, allowing for the use of batteries with small allowable currents or those without current limiting functions, thereby protecting battery-related components and expanding mounting options.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current limiting function is incorporated into the battery or battery control circuit to protect battery-related components, then the reliability of battery protection is improved, but the adaptability of battery selection is worsened
Solution Approach 1:
The motor control device acts as an intermediary between the battery and the motor system. It receives current-related upper limit values from the battery control circuit and calculates torque upper limit values to control motor output, thereby protecting battery-related components without requiring the battery itself to have current limiting functionality. This mediator approach enables the use of various battery types with different control circuit capabilities.
2Reliability
If the discharge power of the battery is reduced to protect battery-related components, then the reliability of battery protection is improved, but the power output capability is worsened
Solution Approach 1:
The system dynamically adjusts the torque upper limit value based on the current-related upper limit value and accelerator operation amount. The motor control device calculates the torque upper limit value in real-time to maintain current-related values within acceptable ranges while maximizing power output capability. This dynamic adjustment allows the system to protect battery components without unnecessarily limiting power output when conditions permit.
Data Source
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AI summary
There are provided a control method and a control device for a motor of an electric vehicle. The control method includes: setting a current-related upper limit value of a current-related value related to a current flowing through a battery of the electric vehicle in accordance with a vehicle state when the electric vehicle is driven by the motor; and calculating a torque upper limit value of a command torque for commanding the motor to maintain a state where the current-related value is equal to or less than the current-related upper limit value, based on an accelerator operation amount input to the electric vehicle and the current-related upper limit value.