D-Axis Position Correction Using Speed-Dependent Calibration
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Solution Overview
Problem
Existing methods for determining the correction value for a control device of an electrical machine are inefficient, particularly in automotive applications where precise torque control is crucial, as they require multiple rotations of the rotor to achieve accurate d-axis positioning, which is time-consuming and labor-intensive.
Innovation Solution
A method that calculates the correction value using rotor position information, stator voltage components, magnetic flux, rotor speed, and a speed-dependent calibration value, allowing for precise determination with minimal effort by accounting for core losses and timing errors, enabling accurate d-axis positioning even with single-direction rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the rotor is rotated repeatedly in two different directions to determine the offset, then the accuracy of the determined d-axis is improved, but the complexity of the process increases and it becomes more time-consuming
Solution Approach 1:
Instead of rotating the rotor in both directions to compensate for iron losses and timing errors, the patent inverts the approach by using a pre-determined calibration value that accounts for these effects. The correction value is calculated using Equation 2 with the calibration value Δud(ωel) that was previously determined to compensate for iron losses, thereby achieving accurate d-axis positioning without requiring bidirectional rotation.
Solution Approach 2:
The patent applies preliminary action by pre-determining the calibration value Δud(ωel) that compensates for iron losses and timing errors before the actual correction value determination. This calibration value is stored and reused during operation, eliminating the need to perform time-consuming bidirectional rotations each time the correction value is needed.
2Measurement precision
If the rotor is rotated repeatedly in two different directions to determine the offset, then the accuracy of the determined d-axis is improved, but the time required for the process increases
Solution Approach 1:
The calibration value Δud(ωel) is determined in advance and stored, allowing the correction value to be quickly calculated during operation using Equation 2 without requiring time-consuming repeated rotations in both directions.
Solution Approach 2:
The patent changes the parameter from requiring dynamic bidirectional rotation to using a pre-stored calibration value that varies with electrical angular frequency ωel. This parameter change from mechanical operation to stored data lookup significantly reduces the time required for correction value determination.
3Ease of operation
If a simple correction method is used without accounting for iron losses and timing errors, then the process is simpler and faster, but the accuracy of the correction value deteriorates
Solution Approach 1:
The calibration value Δud(ωel) acts as an intermediary that compensates for iron losses and timing errors. By introducing this intermediate parameter that was pre-determined to account for these effects, the system achieves high accuracy while maintaining operational simplicity through the use of Equation 2.
Solution Approach 2:
The patent introduces the calibration value parameter Δud(ωel) that varies with electrical angular frequency to account for iron losses and timing errors. This parameter change transforms the correction calculation from a simple geometric relationship to a more accurate model that incorporates physical effects, thereby improving accuracy while maintaining computational efficiency.
Data Source
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AI summary
A method for determining a correction value for a control device (3) for an electrical machine (5), wherein the correction value describes an angular difference between a position of a d-axis of the electrical machine (5), which position is assumed in an initial configuration of the control device (3) on the basis of rotor position information (8) of a rotor position transmitter (7), and an actual position of the d-axis, wherein a zero current is impressed into stator windings of the electrical machine and the correction value, in a rotating state of a rotor of the electrical machine (5), is determined depending on - a d-voltage value which describes a d-component of a stator voltage which is prespecified by the control device (3) in the initial configuration, - a q-voltage value which describes a q-component of the stator voltage which is prespecified by the control device (3) in the initial configuration, - a flux value which describes a magnetic flux of the rotor, - a rotation speed value which describes the rotation speed of the rotor in the rotating state, and - a calibration value which describes a rotation-speed-dependent voltage error in the d-component of the stator voltage.