Electric Motor Pulse Frequency Control for Lower NVH
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Solution Overview
Problem
Existing electric motor systems face challenges in reducing Noise, Vibration, and Harshness (NVH) while maintaining high operating efficiency, particularly in applications like electric vehicles where excessive NVH is unacceptable.
Innovation Solution
The system adjusts the pulsing frequency of electric machines during pulsed operation to minimize NVH while ensuring high efficiency, using real-time feedback and tables that account for various vehicle conditions and configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the amplitude of the pulses is increased to improve motor efficiency, then operating efficiency is improved, but Noise, Vibration and Harshness (NVH) increases
Solution Approach 1:
The patent applies dynamics by making the pulse frequency adjustable rather than fixed. The controller dynamically selects from multiple frequency tables based on real-time operating conditions (torque demand, machine speed, NVH inputs) to optimize the balance between efficiency and NVH. This is evident in the controller's ability to switch between different frequency selection strategies depending on vehicle speed, torque requirements, and NVH thresholds.
Solution Approach 2:
The patent changes the parameter of pulse frequency across multiple discrete levels (e.g., 100 Hz, 200 Hz, 400 Hz, 800 Hz, 1600 Hz, 3200 Hz) to resolve the contradiction. By having multiple frequency tables with different frequency assignments for the same torque/speed conditions, the system can select frequencies that maintain efficiency while avoiding NVH-prone ranges. The amplitude is kept at or near peak efficiency while frequency varies to control NVH.
2Object-generated harmful factors
If the frequency of the pulses is decreased to reduce NVH, then NVH is reduced, but operating efficiency decreases
Solution Approach 1:
The system dynamically adjusts pulse frequency based on real-time NVH inputs and operating conditions rather than using a fixed low frequency. The controller monitors NVH levels and selectively decreases frequency only when NVH thresholds are exceeded, while maintaining higher frequencies when efficiency is prioritized. This dynamic adaptation allows the system to avoid the trade-off by being frequency-variable rather than frequency-fixed.
Solution Approach 2:
The patent uses periodic pulsed action with variable periods (frequencies) to maintain efficiency while managing NVH. Instead of continuous operation or fixed-period pulsing, the system employs periodic pulses with selectively varied frequencies that adapt to operating conditions. This allows the motor to operate at peak efficiency during each pulse while the variable period between pulses controls the overall NVH characteristics.
3Object-generated harmful factors
If multiple frequency tables are used to reduce NVH, then NVH control is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing multiple frequency tables in advance, each optimized for different operating scenarios. Rather than computing frequencies in real-time, the controller simply selects from pre-prepared tables based on current torque demand and machine speed. This eliminates complex real-time calculations while maintaining sophisticated NVH control, as the computationally intensive work was done beforehand during system setup.
Solution Approach 2:
The system uses feedback from NVH sensors and operating condition monitors to select the appropriate frequency table. The controller continuously monitors torque demand, machine speed, and NVH levels, then selects from multiple pre-programmed frequency tables based on this feedback. This feedback mechanism allows intelligent selection among multiple frequency options without requiring complex real-time computation, as the decision logic is based on straightforward threshold comparisons and lookup operations.
Data Source
AI summary
Pulsed control of electric motors, and more particularly, to selectively adjusting one or more of a pulsing frequency, an amplitude of the pulses and/or a duty cycle of the pulses for reducing Noise, Vibration and Harshness (NVH) while maintaining high levels of operating efficiency.