Electric Motor Torque Control for Counter Electromotive Voltage
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Solution Overview
Problem
In electric vehicles with multiple motors driving the same shaft, the absence of a clutch between motor output shafts leads to counter electromotive voltage issues when one motor is non-functional, risking circuit component failure due to high-speed rotation.
Innovation Solution
Implementing control means that restrict torque to the operational motor based on counter electromotive voltage when a non-drive condition is detected, disconnecting power supply to the faulty motor and canceling torque restriction only when the vehicle is stationary, with staged cancellation of torque restriction values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the output shafts of the motors are engaged with the same drive shaft without interposition of a clutch, then the structure is simplified and cost is reduced, but counter electromotive voltage is generated in the non-drive motor due to rotation of the drive shaft, creating risk of circuit component failure
Solution Approach 1:
The control device changes the operational parameters of the drive motor by restricting its output torque based on the counter electromotive voltage generated in the non-drive motor. This parameter adjustment prevents the counter electromotive voltage from exceeding the withstand voltage of circuit components, thereby resolving the reliability issue while maintaining the simplified structural configuration
2Reliability
If torque restriction is executed to the drive motor based on counter electromotive voltage, then circuit components are protected from damage, but vehicle acceleration performance is reduced
Solution Approach 1:
The control device applies partial torque restriction to the drive motor, adjusting the torque output to be just sufficient to prevent counter electromotive voltage from exceeding circuit component withstand voltage. This partial action approach protects circuit components while minimizing the impact on vehicle acceleration performance
3Reliability
If the power supply path to the faulty motor is electrically disconnected, then the faulty motor is put in non-drive condition for safety, but the counter electromotive voltage issue arises from the coupled drive shaft rotation
Solution Approach 1:
The control device converts the harmful counter electromotive voltage generated in the non-drive motor into a controllable parameter by using it as the basis for torque restriction control. By monitoring and responding to this voltage, the system protects circuit components while maintaining operational flexibility
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
Prevents circuit component damage by managing counter electromotive voltage within safe limits and ensures safe vehicle operation by preventing sudden acceleration during torque restriction cancellation.
Implementation Method 1
a counter electromotive voltage is generated in the motor in the non-drive condition due to the rotation of the drive shaft
Data Source
AI summary
An electric vehicle comprises a drive shaft that outputs drive force and at least two electric motors that output power to this drive shaft, and further comprises control means that executes, when either of the electric motors is in non-drive condition, torque restriction of the electric motor in the drive condition based on the counter electromotive voltage of the electric motor in the non-drive condition. In an electric vehicle in which the same shaft is driven by two or more electric motors, circuit components such as inverters can be suitably protected even in the case where vehicle running is continued with one of the electric motors in non-drive condition.