Electric Machine Angle Error Estimation via Flux Injection
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Solution Overview
Problem
Existing electric drive systems in vehicles face inefficiencies due to inaccuracies in determining the angle between the rotor flux reference position and the rotor sensor zero angle reference position, which can lead to incorrect torque delivery and vehicle speed control, especially in designs with relocated motor stators or memory errors.
Innovation Solution
A method is developed to estimate the angle error by injecting a time-varying flux voltage signal into the electric machine controller, allowing for accurate determination of the angle between the rotor flux reference position and the rotor sensor zero angle reference position without requiring a torque sensor or vehicle operation, using a space vector pulse width modulation drive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the angle between rotor flux reference position and rotor sensor zero angle reference position is determined using conventional methods, then the system structure remains simple, but the angle determination accuracy deteriorates leading to incorrect torque delivery
Solution Approach 1:
The system uses the electric machine's own operational signals (phase currents and voltages) to determine the angle error, eliminating the need for external sensors or complex calibration equipment. The machine essentially measures itself during normal operation, improving angle accuracy without adding external measurement devices.
Solution Approach 2:
The patent replaces physical mechanical alignment methods or additional mechanical sensors with an electrical signal processing approach. By using electrical measurements and mathematical transformations (Park transform, inverse Park transform), the system determines angle error electronically rather than through mechanical means.
2Measurement precision
If a torque sensor is used to accurately determine the angle, then the angle measurement precision improves, but the device complexity and cost increase
Solution Approach 1:
The system eliminates the need for external torque sensors by using the electric machine's own phase currents and voltages as measurement inputs. The angle error is calculated from these existing operational signals through signal processing and mathematical transformations, making the system self-measuring.
Solution Approach 2:
The patent introduces mathematical transformations (Park transform, inverse Park transform) and signal processing algorithms as intermediaries to convert readily available electrical measurements into accurate angle information, replacing the need for direct mechanical torque sensing.
3Productivity
If the angle error is not accurately determined, then the system operation remains simple, but the torque delivery accuracy and vehicle efficiency deteriorate
Solution Approach 1:
The system continuously calculates angle error during operation and uses this feedback to correct the rotor flux reference position. This closed-loop approach ensures accurate torque delivery and maintains vehicle efficiency without requiring complex manual calibration procedures.
Solution Approach 2:
The angle error calculation and correction are performed automatically during normal vehicle operation without requiring separate calibration steps or user intervention. The system proactively determines and compensates for angle errors as they occur, maintaining optimal efficiency.
Data Source
AI summary
Systems and methods for operating an electric drive system for an electric or hybrid vehicle is described. In one example, an angle error between an electric machine rotor reference position and an electric machine position sensor reference position is estimated when high voltage is present and when zero torque is commanded of the electric machine.