Electric Machine Torque Estimation Calibration Without Torque Sensors
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Solution Overview
Problem
Existing methods for estimating torque supplied by electrical machines, particularly in aircraft propulsion systems, suffer from inaccuracies due to uncertainties in current measurement and manufacturing tolerances, leading to potential flight safety issues and increased system weight or reduced performance.
Innovation Solution
A calibration method and device that adjusts a torque estimation model using electric current measurements, incorporating steps to measure and compare estimated torque with reference torque, and adjust the model to minimize differences, eliminating the need for a specific torque sensor and improving accuracy across various operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a torque sensor is used for direct measurement, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses an intermediary approach by introducing a calibration procedure that acts as a mediator between the simple current sensor and the torque estimation. The calibration process uses a torque sensor temporarily to establish a correction model, which then enables accurate torque estimation using only the current sensor during normal operation. This resolves the contradiction by eliminating the need for continuous torque sensor integration while maintaining measurement precision through the intermediary calibration model.
Solution Approach 2:
The patent creates a copy or model of the torque-sensor measurement capability through calibration data. Instead of physically integrating a torque sensor, the system creates a mathematical model (correction factors or lookup tables) that copies the torque measurement functionality. This model is derived from temporary torque sensor measurements and then used independently to estimate torque accurately without the physical sensor, thus resolving the device complexity issue while maintaining precision.
2Reliability
If torque sensor is integrated, then reliability is improved, but weight and cost increase
Solution Approach 1:
The patent extracts the essential function of torque measurement from the physical torque sensor and separates it into two components: a temporary calibration phase using the torque sensor, and a permanent operation phase using only the current sensor with calibration data. By taking out the torque sensor from the continuous operation requirement and using it only for initial calibration, the system maintains measurement reliability through the calibration model while eliminating the ongoing weight penalty of integrating a torque sensor in the aircraft propulsion system.
3Device complexity
If indirect torque measurement via current sensor is used, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent introduces feedback by using temporary torque sensor measurements during calibration to generate correction factors that are fed back into the torque estimation model. The calibration process creates a feedback loop where the torque sensor's accurate measurements inform and correct the current sensor-based estimation model. This feedback mechanism allows the simple current sensor system to achieve torque measurement precision comparable to direct torque sensing, resolving the precision deterioration issue while maintaining low device complexity.
Solution Approach 2:
The patent changes the parameters of the torque estimation model through calibration. By adjusting correction factors, scaling parameters, or lookup table values based on torque sensor measurements, the system transforms the raw current sensor data into accurate torque estimates. This parameter adjustment process compensates for the inherent imprecision of indirect measurement, resolving the contradiction by improving precision through parameter optimization while maintaining the simplicity of the current sensor-based approach.
Data Source
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Figure 2b~3
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AI summary
The present application relates to a method for calibrating a model for estimating a torque supplied by an electric machine (10), which comprises the following steps: (E1) measuring an electric current in the electric machine (10) for an operating point; (E2) estimating the torque supplied by the electric machine (10) for the operating point from the measured electric current and an estimation model which associates an output torque with an input electric current; (E3) measuring a reference torque provided by the electric machine (10) for the operating point; (E4) comparing the estimated torque with the reference torque; and (E5) adjusting the estimation model so as to reduce, or even cancel, a difference between the estimated torque and the reference torque.