Dual-Mode EV Motor Control for High-Speed Output and Low Vibration
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Solution Overview
Problem
Conventional electric vehicle motors face limitations in generating a wide range of output due to reduced torque at high speeds and difficulty in adapting to driver preferences, as they either operate synchronously using permanent magnets or asynchronously, with asynchronous operation only up to synchronous speed, leading to inadequate output and discomfort from torque pulsation.
Innovation Solution
A vehicle drive system that switches between synchronous and asynchronous operation modes based on required output, using a motor with a cylindrical stator and rotor, and a control section to manage the mode switch, and cancels torque pulsation by superimposing an antiphase current in the asynchronous mode to reduce vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a PM motor is used to achieve maximum torque in low-speed range, then torque output is improved, but output is reduced in high-speed range due to large back electromotive force
Solution Approach 1:
The motor dynamically switches between synchronous operation mode (using permanent magnet magnetic force) for low-speed high torque requirements and asynchronous operation mode (using induced current in secondary conductors) for high-speed operation, allowing the system to adapt its characteristics to different operating conditions and eliminate the high-speed output limitation
Solution Approach 2:
The motor is designed with dual functionality by incorporating both permanent magnets and secondary conductors, enabling it to operate in both synchronous and asynchronous modes. This multi-functionality allows the motor to overcome the traditional limitation of PM motors and provide adequate output across a wide speed range
2Power
If asynchronous operation is used to eliminate back electromotive force effect, then high-speed output is improved, but torque pulsation occurs due to permanent magnet magnetic force
Solution Approach 1:
The control section utilizes the permanent magnet magnetic force that causes torque pulsation by superimposing an antiphase current to generate counteracting torque, converting the harmful torque pulsation into a beneficial cancellation effect that reduces vibration while maintaining high-speed output capability
Solution Approach 2:
The control section proactively applies an antiphase current that generates torque in opposite phase to the torque pulsation before it manifests as harmful vibration, preventing the adverse effect from impacting the vehicle cabin and driver comfort
3Device complexity
If synchronous operation is presupposed with cage-shaped rotor, then motor structure is simplified, but wide range of required output cannot be generated according to driver preference
Solution Approach 1:
The motor incorporates both permanent magnets and secondary conductors in the rotor, enabling it to function in both synchronous and asynchronous modes. This dual-function design provides adaptability to generate a wide range of required output according to driver preferences while maintaining a relatively simple cage-shaped rotor structure
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
Enables a wide range of output according to driver preference by mode switching and minimizes unpleasant vibration through antiphase current compensation, enhancing the motor's adaptability and comfort.
Implementation Method 1
a synchronous operation mode in which the rotor is rotated by using a magnetic force of the permanent magnet
Implementation Method 2
an asynchronous operation mode in which the rotor is rotated by using an induced current generated in the secondary conductor
Data Source
AI summary
The vehicle drive system includes a motor that has a stator and a rotor provided in the stator and that drives a drive wheel of a vehicle by rotation of the rotor. The rotor has: plural secondary conductors that are aligned in a circumferential direction in a radially outer portion; and plural permanent magnets that are aligned in the circumferential direction in a portion on a radially inner side of these plural secondary conductors. An ECU and a motor ECU capable of switching a drive mode of the motor between a synchronous operation mode and an asynchronous operation mode are further provided. Based on required output for the motor, the ECU and the motor ECU are configured to switch the drive mode of the motor from the synchronous operation mode to the asynchronous operation mode.