Electric Vehicle Drive Motor Speed Ripple Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electric vehicles experience drive motor speed ripple due to noise generated from the synchronization of excitation input signal peaks and inverter switching frequency, leading to noise vibration harshness, reduced gas mileage, and increased durability issues.
Innovation Solution
A system and method that synchronize the peaks of the excitation voltage signal with the dead time periods of the inverter switching, using a motor controller to adjust the PWM signal and excitation input signal frequency, preventing overlapping and minimizing noise generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the excitation input signal frequency is synchronized with the inverter switching frequency, then the resolver can accurately detect motor speed and position, but noise is generated at the peaks of the excitation signal causing speed ripple
Solution Approach 1:
The motor controller pre-adjusts the excitation input signal frequency to be desynchronized from the inverter switching frequency before noise generation occurs. This preliminary frequency adjustment ensures that peaks of the excitation signal do not coincide with inverter switching moments, preventing noise generation at critical measurement points while maintaining accurate resolver detection.
Solution Approach 2:
The system changes the frequency parameter of the excitation input signal dynamically. The motor controller adjusts the excitation frequency to values that are not integer multiples or harmonics of the inverter switching frequency, thereby avoiding peak overlap and noise generation while preserving the resolver's ability to accurately measure motor speed and position.
2Loss of energy
If the inverter switching frequency is increased to improve power conversion efficiency, then energy loss is reduced, but noise generation and speed ripple are exacerbated
Solution Approach 1:
The system independently optimizes two frequency parameters: the inverter switching frequency for energy efficiency and the excitation input signal frequency for noise reduction. The motor controller maintains high inverter switching frequency for efficient power conversion while simultaneously adjusting the excitation frequency to avoid harmonic overlap, thereby achieving both energy efficiency and noise reduction.
3Measurement precision
If the excitation voltage signal amplitude is increased to improve signal-to-noise ratio, then detection accuracy is improved, but noise at the peaks becomes more severe
Solution Approach 1:
The motor controller pre-adjusts the excitation signal frequency to avoid overlap with inverter switching frequency before the signal is applied to the resolver. This prevents the generation of high-amplitude noise at the signal peaks, allowing the system to maintain high excitation voltage amplitude for improved signal-to-noise ratio without suffering from peak noise contamination.
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
This approach reduces drive motor speed ripple, improves efficiency, decreases noise vibration harshness, and lowers after-sales-service costs by minimizing noise at the peaks of the output voltage signal, thereby enhancing the stability and durability of electric vehicle drive motors.
Implementation Method 1
The square wave signal is integrated by a circuit integrator and output as a sine wave and used as an excitation input signal
Implementation Method 2
an inverter that configured to convert DC power supplied from a battery to AC power and supplies the AC power to a drive motor by inverter switching
Implementation Method 3
The motor controller configured to control the PWM signal and the excitation input signal to be synchronized so that the peaks of the excitation voltage signal to be positioned in the dead time periods where no inverter switching occurs
Implementation Method 4
a resolver may be configured to detect a speed of the drive motor and a position of a rotor
Data Source
AI summary
A system and method for reducing drive motor speed ripple of an electric vehicle are provided. The system includes an inverter that converts DC power supplied from a battery to AC power and supplies the AC power to the drive motor by inverter switching. A resolver is configured to detect a speed of the drive motor and a position of a rotor, a signal generator includes a microcontroller that is configured to generate a square wave signal. An integrator is configured to convert the square wave to a sine wave, and apply a sine-wave excitation input signal to the resolver. Furthermore, a motor controller is configured to operate the inverter through a PWM signal, adjust the frequency of the excitation input signal to prevent the inverter switching frequency of the inverter and the peaks of an output voltage signal sampled for speed calculation from overlapping.