EV Motor Slip Detection Using Periodic Torque Fluctuation
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Solution Overview
Problem
Existing systems struggle to accurately and efficiently determine whether a vehicle is slipping, particularly in electric vehicles, as they may require time to detect variations in resonant frequencies.
Innovation Solution
A slip determination apparatus that includes electric motor control circuitry to generate a fluctuating torque command value at a predetermined frequency and determination circuitry to detect fluctuations in the motor's revolutions, allowing for rapid and precise slip detection by comparing fluctuation components against a threshold value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resonant frequency detection is used to determine vehicle slip, then measurement precision is improved, but response time increases and productivity decreases
Solution Approach 1:
The system applies periodic torque fluctuations at a predetermined frequency to the electric motor. By periodically varying the torque command value, the system creates regular oscillations in motor revolutions that can be easily detected and analyzed, enabling rapid slip determination without waiting for natural resonant frequency development
Solution Approach 2:
The control circuit pre-establishes a predetermined frequency for torque fluctuations before slip detection is needed. This preliminary setup of the detection frequency allows the system to immediately begin slip detection operations without requiring time to identify or tune to the resonant frequency, thus reducing response time while maintaining detection accuracy
2Measurement precision
If complex resonant frequency analysis is performed, then measurement precision improves, but device complexity increases
Solution Approach 1:
The system changes the detection approach by using a predetermined frequency parameter instead of analyzing variable resonant frequencies. The control circuit sets a fixed frequency for torque fluctuations, and the determination circuit only needs to detect fluctuations at this known frequency, dramatically simplifying the detection algorithm and reducing computational complexity while maintaining accurate slip detection
Solution Approach 2:
The predetermined frequency acts as an intermediary that simplifies the detection process. Instead of directly analyzing complex resonant frequency variations, the system uses the predetermined frequency as a reference marker, making it easier to detect slip conditions through simpler comparison operations between expected and actual motor behavior at this intermediate frequency reference point
Data Source
AI summary
A slip determination apparatus to be applied to a vehicle includes electric motor control circuitry and determination circuitry. The electric motor control circuitry is configured to generate a first torque command value that fluctuates at a predetermined frequency, and determine torque of an electric motor, based on the first torque command value and a second torque command value that depends on a driving operation performed by a driver who drives the vehicle. The determination circuitry is configured to detect a fluctuation component at the predetermined frequency in a number of revolutions of the electric motor, and determine whether the vehicle is slipping, based on the fluctuation component.