Motor Torque Estimation Weighting Across Low and High Speeds
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Solution Overview
Problem
Existing motor torque estimation methods, such as the cross product and energy methods, have limitations in accurately estimating torque, especially due to assumptions of linear current and magnetic flux relationships and failure to utilize the features of both methods effectively, leading to inaccuracies and instability, particularly at low and high motor speeds.
Innovation Solution
A motor control device that combines first and second torque estimation values based on coil interlinkage flux and motor input power, respectively, with a weighting adjuster to dynamically adjust the weightings applied to these values using a weighting coefficient, allowing for accurate torque estimation across various motor speed regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the cross product method is used to estimate motor torque, then the estimation can be performed based on magnetic flux and current, but the assumption of linear relationship between current and magnetic flux reduces estimation accuracy
Solution Approach 1:
The patent combines the cross product method and energy method into a unified torque estimation system. The cross product estimator calculates torque based on magnetic flux and current, while the energy estimator calculates torque based on motor input power and rotational speed. Both estimation results are merged through a weighting mechanism that dynamically adjusts their contributions based on motor speed, thereby improving overall estimation accuracy while avoiding the limitations of using either method alone.
2Measurement precision
If the energy method is used to estimate motor torque, then the estimation can be performed by dividing motor output by motor rotational speed, but the method fails to accurately estimate torque at low speeds due to division by small numbers
Solution Approach 1:
The patent implements a dynamic weighting mechanism that adjusts the contribution of each estimation method based on motor speed. At low speeds, the weighting coefficient favors the cross product method to avoid division by small numbers. At high speeds, the weighting coefficient transitions to favor the energy method. This dynamic adjustment ensures reliable and accurate torque estimation across the entire speed range, resolving the instability issue at low speeds while maintaining the advantages of the energy method at high speeds.
3Ease of manufacture
If a simple arithmetic mean of torque estimation values from both methods is taken, then the calculation is simple, but the features of each method are not effectively utilized and estimation accuracy is compromised
Solution Approach 1:
The patent introduces a speed-dependent weighting coefficient that dynamically changes the parameters of the torque estimation calculation. Instead of using a fixed arithmetic mean, the system calculates a weighting coefficient based on motor speed, which determines the proportion of each estimation method's contribution. This parameter change enables the system to effectively utilize the strengths of each method across different operating conditions while maintaining computational efficiency through a straightforward weighting formula.
4Measurement precision
If the cross product method is used, then instantaneous torque ripple can be estimated, but the linear relationship assumption limits the effectiveness of this capability
Solution Approach 1:
The patent merges the cross product method's capability to estimate instantaneous torque ripple with the energy method's robustness. The cross product estimator provides detailed instantaneous torque information including ripple, while the energy estimator provides reliable overall torque estimation. The dynamic weighting system combines these complementary capabilities, allowing the system to effectively estimate instantaneous torque ripple when operating conditions favor the cross product method while maintaining overall estimation reliability across all operating conditions.
Data Source
AI summary
A first torque estimator determines a first torque estimation value according to a cross product method, and a second torque estimator determines a second torque estimation value according to an energy method. A torque weight adjuster adjusts, using a weighting coefficient calculated in accordance with a predetermined condition, weightings respectively applied to these two types of torque estimation values, and outputs a torque estimation value.