Pulsed Electric Machine Control Using Lookup Tables
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Solution Overview
Problem
Electric machines, such as motors and generators, often operate at suboptimal efficiency levels due to varying torque and speed requirements, leading to reduced energy conversion efficiency, especially in applications like electric vehicles where they need to operate over a wide range of conditions.
Innovation Solution
Implementing pulse control methods that determine whether to operate in continuous or pulsed mode, with defined pulse frequency and duty cycle, using tables indexed by vehicle speed and torque requests to optimize energy efficiency while minimizing Noise, Vibration, and Harshness (NVH).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the electric machine operates continuously at optimal efficiency points, then energy conversion efficiency is maximized, but the machine cannot adapt to wide variations in torque and speed requirements
Solution Approach 1:
The patent applies periodic pulsed operation instead of continuous operation. The electric machine is pulsed on and off according to a duty cycle, allowing it to operate at optimal efficiency points during active periods while meeting varying torque and speed demands through periodic activation. This resolves the contradiction by enabling the machine to maintain high efficiency while adapting to different operating conditions through time-based modulation rather than continuous adjustment.
2Loss of energy
If the electric machine operates in pulsed mode to improve efficiency, then energy conversion efficiency increases, but Noise, Vibration and Harshness (NVH) levels increase
Solution Approach 1:
The patent changes the frequency parameter of pulsed operation to resolve the NVH issue. By selecting pulse frequencies above the human hearing threshold (>20 Hz), the system maintains the efficiency benefits of pulsed operation while eliminating audible noise and reducing perceptible vibration. This parameter adjustment allows the system to achieve high efficiency without generating unacceptable NVH levels.
Solution Approach 2:
The system dynamically adjusts the duty cycle and frequency of pulsed operation based on operating conditions. By modulating these parameters in real-time, the system can optimize efficiency while keeping NVH levels acceptable across different torque and speed requirements, rather than using fixed pulsed parameters.
3Adaptability or versatility
If the electric machine operates outside optimal load regions to meet varying drive cycle requirements, then adaptability to driving conditions improves, but energy conversion efficiency decreases
Solution Approach 1:
The patent uses periodic pulsed operation to allow the machine to operate at or near optimal efficiency points during active periods, rather than continuously operating at suboptimal loads. By pulsing the machine on and off, the system can meet varying torque demands while maintaining high efficiency during active operation, thus resolving the contradiction between adaptability and efficiency.
Data Source
AI summary
A variety of methods, controllers and electric machine systems are described for pulse control of electric machines (e.g., electric motors and generators). To improve the energy conversion efficiency of the machine, pulse control involves determining if the machine should operate in a continuous mode or pulse mode, and if the latter, defining a magnitude, duty cycle, and frequency for the pulses. One or more tables, indexing by a wide range of speeds and torque requests, is/are used to define the pulsing frequency or a pulsing frequency pattern.