Rotor Radial Position Sensing With Segmented Conductive Targets
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Solution Overview
Problem
Existing sensor devices for contactless determination of a rotor's radial position in active magnetic bearings are prone to faults due to defects in the sensor target, leading to distorted measurements and incorrect position determination, especially at high speeds, which introduce dynamic excitations and negatively affect system control.
Innovation Solution
A sensor device with a target unit having multiple target elements separated by gaps, where the geometry of the coils and gaps is coordinated to minimize the temporal change of the projected coil portion onto the gaps during rotor rotation, ensuring minimal disturbance to the response signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a continuous target element is used to maximize the cylindrical target area, then the sensor head achieves high positional resolution and sensitivity, but defects in the target element cause falsified measured distances and incorrect position determination
Solution Approach 1:
The continuous target element is divided into multiple separate target elements (e.g., three target elements with gaps between them). This segmentation allows the sensor to tolerate defects in individual elements while maintaining measurement capability through the remaining elements, thus improving fault tolerance without significantly compromising positional resolution
Solution Approach 2:
Different regions of the target unit have different properties - the target elements are arranged with specific gaps between them. The gaps are positioned and dimensioned to minimize their impact on the sensor signal while the target elements provide the measurement function. This local differentiation allows the system to maintain high measurement precision in the regions with target elements while accepting the presence of gaps as a fault-tolerance feature
2Reliability
If target elements are separated by gaps to improve fault tolerance, then the sensor becomes more reliable, but the gaps cause temporal changes in the projected coil portion leading to signal disturbances
Solution Approach 1:
The gaps between target elements are positioned asymmetrically with respect to the coil winding pattern. Specifically, the gaps are located in regions where the coil has minimal sensitivity or where the projected coil area onto the gaps causes minimal temporal variation. This asymmetric arrangement reduces signal disturbances while maintaining the fault tolerance benefits of the segmented target structure
Solution Approach 2:
The problem of gap-induced signal disturbances is addressed by considering the three-dimensional arrangement of the coil and target elements. The coil is designed with specific radial and tangential dimensions, and the gaps are positioned at specific radial distances and angular positions. By optimizing the projection of the coil onto the target elements in multiple dimensions, the temporal variation of the projected coil area is minimized, reducing signal disturbances
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The sensor device enhances fault tolerance and improves the control of active magnetic bearings by preventing disturbances in the response signal, allowing for more precise and reliable position determination even at high speeds.
Implementation Method 1
a coil unit (4) having at least one coil (4a) and designed for electromagnetic interaction with the target material (3a to 3f) of the target unit (3)
Implementation Method 2
The coil unit (4) has at least one coil (4a) and is designed for electromagnetic interaction with the target material (3a to 3f) of the target unit (3)
Data Source
Figure 1~5b
Figure 6a~7b
AI summary
The disclosure relates to a sensor device (1) for non-contact determination of the radial position of a rotor (2), which is designed to rotate about a longitudinal axis (L), comprising a target unit (3) arranged on the rotor (2) and having an electrically conductive target material; a coil unit (4) comprising at least one coil (4a) and configured for electromagnetic interaction with the target material of the target unit (3); and a control unit (5) electrically coupled to the coil unit (4) and configured to excite the coil (4a) of the coil unit (4) with an excitation signal and to detect and evaluate a response signal from the coil unit (4) in order to determine the radial position of the rotor (2); wherein the target unit (3) has several target elements (3a-3f) with the target material arranged in the direction of rotation on the rotor (2), which are separated from each other by a respective gap (6a-6f);and the column (6a-6f) of the target unit (3) and the at least one coil (4a) of the coil unit (4) are geometrically matched such that the temporal change of the component (4a') of the coil (4a), which is projected in a radial projection onto the target unit (3) in a radial projection when the rotor (2) is rotating, is essentially zero, wherein the projected component (4a') of the coil (4a) is not spaced further than a predetermined maximum distance from the target elements (3a-3f) in order to realize a sensor device (1) with improved error tolerance.