Electric Vehicle Slip Rate Detection Using Motor Electrical Parameters
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Solution Overview
Problem
Existing slip rate calculation methods for electric vehicles are plagued by calculation delays, complexity, and poor real-time properties, particularly due to the need for sensors that affect accuracy and are limited to specific vehicle types.
Innovation Solution
A method that measures voltage, current, and rotational speed of the drive motor to calculate slip rate using motor and vehicle constants, eliminating the need for vehicle speed sensors and applicable to both two-wheel and four-wheel drive vehicles, with a simple and real-time detection system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If velocity sensors or acceleration sensors are mounted on driving wheels and driven wheels to detect slip rate, then the slip rate can be obtained by detecting wheel speeds, but the system performance is reduced, relay occurs, and accuracy is affected by encoder resolution
Solution Approach 1:
The patent extracts the slip rate detection function from the wheel speed sensors and vehicle speed sensors, and relocates it to the motor controller by utilizing existing motor detection data (current, voltage, rotational speed). This eliminates the need for additional velocity or acceleration sensors on the wheels, reducing device complexity while maintaining measurement accuracy.
Solution Approach 2:
The motor controller performs slip rate detection using its own existing detection capabilities (motor current, voltage, and rotational speed sensors), making the system self-sufficient without requiring external velocity or acceleration sensors. The motor controller serves dual purposes: motor control and slip rate detection.
2Measurement precision
If the Fourier transform is used to analyze system transfer characteristic from rotational speed to drive force, then the change of road surface condition can be analyzed, but the calculation is complex and consumes relatively long time, resulting in poor real-time property
Solution Approach 1:
The patent replaces the complex Fourier transform mathematical system with a simplified calculation method based on motor electrical characteristics. Instead of performing spectral analysis on rotational speed data, the system directly calculates slip rate using motor current, voltage, and rotational speed through algebraic equations, achieving both accuracy and real-time performance.
3Measurement precision
If torque sensor is mounted to measure external drive torque and wheel speed for slip rate calculation, then the slip rate can be obtained, but delay and accuracy problems result from the sensor
Solution Approach 1:
The patent extracts the torque measurement function from a separate torque sensor and relocates it to the motor controller by calculating torque from motor current and electrical characteristics. This eliminates the need for physical torque sensors and their associated delays, as electrical current data is already available in real-time within the motor control system.
4Measurement precision
If integration is used to calculate slip rate from differential equation, then the slip rate can be obtained, but the calculation method is complex and has poor real-time property
Solution Approach 1:
The patent replaces the complex integration-based differential equation method with a direct algebraic calculation approach. Instead of solving differential equations requiring integration over time intervals, the system calculates slip rate instantaneously using algebraic equations based on motor electrical parameters, significantly reducing computational complexity and improving real-time performance.
Data Source
AI summary
A slip rate detection method and a detection system for detecting the slip rate of an electric vehicle using the method. The slip rate of an electric vehicle is measured by measuring the motor voltage, motor current, and motor rotational speed of the drive motor. The detection system includes a motor rotational speed detection unit, a motor voltage detection unit, and a motor current detection unit, all connected to the drive motor. The motor rotational speed detection unit, the motor voltage detection unit, and the motor current detection unit are connected to a slip rate calculation unit by means of a motor rotational speed signal processing unit, a voltage signal processing unit, and a current signal processing unit, respectively. The slip rate calculation unit is configured with a slip rate calculation formula. The formula is determined according to the drive motor type.