Displacement synchronous detection system and method for bearingless motor rotor angle

Abstract

The embodiment of the invention discloses a displacement synchronous detection system and method for the rotor angle of a bearingless motor, relates to the field of motor control and precision measurement, and designs a rotor position detection reference ring capable of reflecting the rotor angle and radial displacement information at the same time for the bearingless motor. The invention also provides a demodulation method for simultaneously detecting the rotor angle and radial displacement information. The reference ring is in the shape of a regular polygon, an oval and the like, and after the reference ring is installed in cooperation with the eddy current sensor, the rotor angle and the radial displacement can be modulated in displacement information detected by the eddy current sensor at the same time. When the motor runs, the rotor drives the reference ring to rotate synchronously, the eddy current sensor detects and outputs a distance voltage signal in real time, and the distance voltage signal is processed and analyzed by the DSP. According to the detection method provided by the invention, the rotation angle and radial displacement information of the rotor can be demodulated from the displacement information at the same time. The number of required sensors can be reduced, the system volume requirement is reduced, the system structure is simplified, and the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the fields of motor control and precision measurement, and in particular, to a displacement synchronous detection system and method for the rotor angle of a bearingless motor, mainly used for synchronous detection of the rotor angle and radial displacement of a bearingless motor. Background Art

[0002] As a new type of motor integrating rotation and suspension functions, the bearingless motor has broad application prospects in the fields of aerospace, high-speed machine tools, vacuum pumps, flywheel energy storage, etc. To achieve stable suspension and precise control of the bearingless motor, it is crucial to accurately detect the rotor angle and radial displacement. Traditional rotor position detection methods require corresponding sensors and detection systems to be configured separately for the rotor angle and radial displacement, which have the disadvantages of high system complexity, large occupied space, high manufacturing and usage costs, etc.

[0003] Currently, the main synchronous detection methods for the rotor angle and radial displacement include the state observer method, the intelligent detection method based on machine learning, or the high-frequency signal injection method, etc. During the low-speed operation or startup process of the motor, the signal-to-noise ratio of the rotor angle and radial displacement and the related current, voltage, or magnetic flux information is very low, and at this time, it is difficult for the state observer method and the intelligent detection method based on machine learning to accurately estimate the rotor angle and radial displacement. The high-frequency signal injection method utilizes the electromagnetic characteristics of the motor itself, with a simple principle and good robustness. However, this method requires the motor to have a certain degree of saliency, and continuous high-frequency excitation needs to be injected, which will interfere with the fundamental wave signal of the motor, etc., and also has relatively high requirements for hardware and signal processing technologies, resulting in a relatively large number of sensors required in practical applications, a more complex structure of the sensing system, and thus more space will be occupied, ultimately increasing the manufacturing cost of the motor. Summary of the Invention

[0004] Embodiments of the present invention provide a displacement synchronous detection system and method for the rotor angle of a bearingless motor, which can alleviate the problem of a relatively large number of sensors required in practical applications, a relatively complex structure of the sensing system, and thus more space occupied, so as to reduce the manufacturing cost of the motor.

[0005] To achieve the above object, the embodiments of the present invention adopt the following technical solutions:

[0006] In a first aspect, an embodiment of the present invention provides a displacement synchronous detection system for the rotor angle of a bearingless motor, including: a rotor position detection reference ring (1) fixed on the rotating shaft (7) of the bearingless motor; wherein, a protective bearing (10) is also sleeved on the bearingless motor, which plays a protective role when the suspension function of the bearingless motor fails, and the protective bearing (10) is also suspended during normal operation. A bracket (9) is fixed on the end cover (8) of the bearingless motor through double bolts (11), and an eddy current sensor (13) is also installed on the motor end cover (8); the eddy current sensor probe (2) of the eddy current sensor (13) is fixed on the bracket (9) and fixed through a fastening nut (12), and the eddy current sensor probe (2) faces the detection surface (6) of the rotor position detection reference ring (1). Among them, the eddy current sensor (13) integrates a probe, an extension cable, and a preamplifier, and can output a voltage signal linearly related to the gap between the probe and the detection surface. A DSP (Digital Signal Processor) (5) processes and analyzes the collected voltage signal to extract the rotational angle and radial displacement information of the rotor.

[0007] Optionally, the cross-sectional shape of the rotor position detection reference ring (1) is a regular polygon or an ellipse. The rotor position detection reference ring (1) can be designed in shapes such as a regular polygon or an ellipse. Such a design enables the reference ring to simultaneously reflect the rotational angle and radial displacement characteristics of the rotor.

[0008] The rotor position detection reference ring (1) is fixed on the motor rotating shaft (7) in an interference fit manner to synchronously rotate with the rotating shaft (7) of the bearingless motor, that is, to rotate synchronously with the motor rotor; the material of the rotor position detection reference ring (1) is stainless steel. Among them, in a preferred solution, the rotor position detection reference ring (1) is made of stainless steel material. The reference ring needs to be precision machined, and the detection surface (6) is precisely machined to ensure the accuracy of geometric dimensions. At the same time, the roughness of the detection surface (6) should be strictly controlled to meet the requirements of high-precision measurement.

[0009] Furthermore, two eddy current sensors (13) are installed in the x-axis direction and the y-axis direction of the motor end cover (8) respectively, so as to form four-direction eddy current sensor probes (2) which are Y1, Y2, X1, and X2 respectively; Y1, Y2, X1, and X2 are evenly distributed along the circumferential direction of the motor, and the angle between each probe and the adjacent probe is 90°, and the installation direction of the probes all points to the rotor center axis. The components of the eddy current sensor (13) also include a preamplifier (4), the preamplifier (4) is connected to the eddy current sensor probe (2) through an extension cable (3), and the preamplifier (4) is also connected to the DSP (5); the preamplifier (4) includes: an oscillator, a detection circuit, an amplifier, and a linear correction circuit.

[0010] The preamplifier (4) is used as an electronic signal processor. On the one hand, it provides high-frequency alternating current for the probe coil (15) of the eddy current sensor probe (2), and records the changes in probe parameters caused by the detection surface (6) (as a metal conductor) approaching the eddy current sensor probe (2). The probe parameters include: an output voltage signal that is linearly related to the gap between the detection surface (6) and the end face of the eddy current sensor probe (2). After the voltage signal is transmitted to the DSP (5), the DSP (5) obtains the rotor motion parameters, including the rotation angle and radial displacement of the rotor. After being processed by the preamplifier (4), an output voltage signal that is linearly related to the gap between the measured surface and the probe end face is generated, and this signal reflects the rotation angle and radial displacement information of the rotor. The voltage signal output by the eddy current sensor (13) is transmitted to the DSP (5) through a conditioning circuit, and the rotation angle and radial displacement of the rotor are obtained through demodulation analysis in the DSP (5).

[0011] On the second hand, the displacement synchronization detection method for the rotor angle of the bearingless motor provided by the embodiment of the present invention includes:

[0012] S1. After the bearingless motor starts, as the gap between the eddy current sensor probe (2) and the detection surface (6) changes, the eddy current sensor (13) continuously collects an output voltage signal that is linearly related to the gap between the detection surface (6) and the end face of the eddy current sensor probe (2). Among them, as the rotor of the bearingless motor rotates, the rotation angle and radial displacement of the rotor change, causing the gap between the eddy current sensor probe (2) and the detection surface (6) to change, thereby causing a change in the output voltage of the eddy current sensor (13). The DSP (5) processes the collected voltage signal to obtain the distance information between the eddy current sensor probe (2) and the detection surface (6).

[0013] S2. Divide the voltage signal collected by the eddy current sensor (13) according to intervals, and establish the corresponding relationships within different intervals. The corresponding relationships include: the corresponding relationship between the distance information between the eddy current sensor probe (2) and the detection surface (6) and the rotor motion parameters; the rotor motion parameters include: the rotor angle and radial displacement. Determine the corresponding relationship between the mechanical rotation period of the bearingless motor rotor and the period of the voltage signal of the eddy current sensor (13) according to the specific shape of the rotor position detection reference ring (1), and divide a period of the voltage signal of the eddy current sensor (13) into multiple intervals. Within different intervals, the corresponding relationships between the detected distance information and the rotor angle and radial displacement are different.

[0014] S3. Identify the rotation angle range of the rotor and determine the rotation angle of the bearingless motor rotor. Specifically, map the rotation angle range based on the variation law of the distance information between the four eddy current sensor probes (2) and the detection surface (6) measured, and judge the rotation angle range of the rotor. Then, comprehensively process the distance information measured by the four sensors to cancel out the overall offset error caused by the radial displacement of the rotor, thereby obtaining the rotor angle-related quantity. According to the corresponding mathematical model within this angle range, the rotation angle of the rotor can be obtained through processing and analysis.

[0015] S4. Utilize the rotation angle of the bearingless motor rotor to obtain the radial displacements of the rotor in the x-axis and y-axis directions. The obtained radial displacements are fed back to the control system of the bearingless motor for closed-loop control. Specifically, the eddy current sensor integrates a probe, an extension cable, and a preamplifier. The circuit in the preamplifier generates a high-frequency current signal and sends it to the probe of the sensor. When the probe approaches the measured metal, high-frequency eddy current signals will be induced inside the metal. Due to the skin effect of high-frequency signals in conductors, the induced eddy current signals mainly exist on the metal surface and are transmitted to the probe. Due to Lenz's law, the feedback signal is opposite to the signal inside the probe, and the superposition of the two causes the impedance of the probe coil to change. The cable then transmits this signal back to the preamplifier. After being processed by the preamplifier, an output voltage signal linearly related to the gap between the measured surface and the end face of the probe is generated. Changes in the rotation angle and radial displacement of the rotor will both cause changes in the distance between the eddy current sensor probe and the detection surface, thereby causing changes in the output voltage of the eddy current sensor. This voltage signal reflects the rotation angle and radial displacement information of the rotor. The voltage signal output by the eddy current sensor is transmitted to the DSP through a conditioning circuit. After being processed and analyzed by the DSP, the rotation angle and radial displacement of the rotor are obtained. Taking the square rotor position detection reference ring as an example for analysis, the cross-sectional outer contour of this reference ring is square, and there are a total of four detection surfaces. For the square reference ring, every 90° of rotor rotation angle is a cycle of the sensor voltage signal. Divide a cycle of the sensor voltage signal into two 45° intervals. In different intervals, the corresponding relationships between the rotor angle, radial displacement, and distance information are different. Map the angle range according to the variation law of the distance information between the four sensor probes and the detection surface, thereby judging the range of the rotor rotation angle.

[0016] Specifically, in S2, the voltage signals collected by the eddy current sensor (13) are divided according to the intervals of the rotor rotation angle, and the corresponding relationships in different intervals are established, including: when the rotor rotation angle is 0°, the normal directions of the four detection surfaces of the rotor position detection reference ring (1) respectively correspond to the four basic directions of the xy coordinate system, and the rotor rotates counterclockwise; among them, in the angle interval of 0° to 45°, the distance between the eddy current sensor probe (2) and the detection surface (6) shows a decreasing trend, and the distance between the eddy current sensor probe (2) and the detection surface (6) is the smallest at 45°; in the angle interval of 45° to 90°, the change trend of the distance between the eddy current sensor probe (2) and the detection surface (6) is opposite to that in the angle interval of 0° to 45°.

[0017] For example: at time t, the judgment method for the interval of the rotor rotation angle is as follows:

[0018]

[0019] where Δt represents a detection period, and ΣL t represents the sum of the distances detected by the four eddy current sensors (13) at time t.

[0020] In the angle interval of 0° to 45°, the distances between the four eddy current sensor probes (2) of Y1, Y2, X1, and X2 and the detection surface (6) detected are:

[0021]

[0022] where Δt represents a detection period, and ΣL t represents the sum of the distances detected by the four eddy current sensors (13) at time t, L1, L2, L3, and L4 respectively represent the distances between the four eddy current sensor probes (2) of Y1, Y2, X1, and X2 and the detection surface (6) detected during the rotor rotation; d represents the initial distance between the four eddy current sensor probes (2) of Y1, Y2, X1, and X2 and the detection surface (6) when the rotor rotation angle is 0°; Δr θ represents the change amount of the distance between the probe and the detection surface due to the change of the rotation angle during the rotor rotation; Δx -x represents the distance change measured in the x direction caused by the displacement in the x direction. When the rotor moves in the positive direction of the x axis, Δx -x is positive; Δx -y represents the distance change measured in the x direction caused by the displacement in the y direction. When the rotor moves in the negative direction of the y axis, Δx -y is positive; Δy -y represents the distance change measured in the y direction caused by the displacement in the y direction. When the rotor moves in the negative direction of the y axis, Δy-y is positive; Δy -x represents the distance change measured in the y - direction caused by the displacement in the x - direction. When the rotor moves in the positive x - axis direction, Δy -x is positive.

[0023] In the range of 45° to 90°, the distances between the four eddy - current sensor probes Y1, Y2, X1, X2 and the detection surface are:

[0024]

[0025] Adding the distances between the four probes Y1, Y2, X1, X2 and the detection surface can cancel out the overall offset error caused by the radial displacement of the rotor. From the analysis of Equation (2) and Equation (3), we can get:

[0026] L1 + L2 + L3 + L4 = 4d - 4Δr θ (5)

[0027] Let the perpendicular distance from the geometric center of the square to any one of its sides be a. It is easy to obtain that in the range of 0° to 45°, Δr θ The expression of

[0028]

[0029] In the range of 45° to 90°, Δr θ The expression of

[0030]

[0031] By combining Equation (4) and Equation (5), in the range of 0° to 45°, the relationship between the rotation angle of the rotor and the measured distance is:

[0032]

[0033] By combining Equation (4) and Equation (6), in the range of 45° to 90°, the relationship between the rotation angle of the rotor and the measured distance is:

[0034]

[0035] After obtaining the rotation angle θ of the rotor, combined with the distance information of the four sensors, according to the corresponding mathematical model in this angle range, calculate the radial displacements of the rotor in the x - axis and y - axis directions.

[0036] In the range of 0° to 45°, Δy -x The relationship between Δy and Δx, and -y the relationship between Δx and Δy is

[0037]

[0038] In the range of 45° to 90°, Δy -x and Δx, Δx -y The relationship with Δy is

[0039]

[0040] After obtaining θ, by combining equations (2), (5), and (9), it can be obtained that in the range of 0° to 45°, Δx and Δy are respectively

[0041]

[0042] By combining equations (3), (6), and (10), it can be obtained that in the range of 45° to 90°, Δx and Δy are respectively

[0043]

[0044] At 45°, Δx and Δy are respectively

[0045]

[0046] For the elliptical reference ring, it is set that the 180° rotor rotation angle is a complete cycle of the eddy current sensor voltage signal, and a cycle of the eddy current sensor voltage signal is divided into two 90° intervals. In different intervals, the corresponding relationship between the detected distance information and the rotor angle and radial displacement is different.

[0047] According to the variation law of the distance information between the four sensor probes and the detection surface measured, perform angle interval mapping to judge the interval of the rotor rotation angle.

[0048] If the rotor rotation angle is 0°, its major axis coincides with the x-axis, the minor axis coincides with the y-axis, and the rotor rotates counterclockwise. Then in the range of 0° to 90°, the distances between the Y1 and Y2 sensor probes and the detection surface show a decreasing trend, and the distances between the X1 and X2 sensor probes and the detection surface show an increasing trend. The variation trend in the range of 90° to 180° is opposite to this. This variation trend is an important basis for judging the rotor angle interval. Let Δt be a detection cycle, and ΣL Yt 、ΣL Xt are respectively the total distances detected by the eddy current sensors in the y-axis and x-axis directions at time t. Then the judgment formula for the rotor rotation angle interval at time t is

[0049]

[0050] In the range of 0° to 90°, the distances between the four eddy current sensor probes Y1, Y2, X1, and X2 and the detection surface detected are

[0051]

[0052] L1, L2, L3, and L4 represent the distances between the four eddy current sensor probes Y1, Y2, X1, and X2 and the detection surface detected during the rotation of the rotor; d1 and d2 represent the distances from the two pairs of eddy current sensor probes Y1, Y2 and X1, X2 to the center of the ellipse; r θ , r θ ’ represent the distances from the center of the ellipse to the detection surfaces in the y-axis and x-axis directions respectively during the rotation of the rotor; Δx -x represents the distance change measured in the x-direction caused by the displacement in the x-direction. When the rotor moves in the positive x-axis direction, Δx -x is positive; Δx -y , Δx -y ’ represent the distance changes measured in the negative x-direction and positive x-direction caused by the displacement in the y-direction. When the rotor moves in the negative y-axis direction, Δx -y and Δx -y ’ are positive; Δy -y represents the distance change measured in the y-direction caused by the displacement in the y-direction. When the rotor moves in the negative y-axis direction, Δy -y is positive; Δy -x , Δy -x ’ represent the distance changes measured in the positive y-direction and negative y-direction caused by the displacement in the x-direction. When the rotor moves in the positive x-axis direction, Δy -x and Δy -x ’ are positive. In the range of 90° to 180°, the distances between the four eddy current sensor probes Y1, Y2, X1, and X2 and the detection surface detected are:

[0053]

[0054] For the elliptical rotor position detection reference ring, within a corresponding interval of one period, after measuring the distance information, the rotation angle and radial displacement information of the rotor can be obtained according to the look-up table method. According to the characteristics and design requirements of the motor, the theoretical distances of the four eddy current sensor probes relative to the detection surface are pre-calculated and sampled under different combinations of rotation angles and radial displacements. These theoretical distances are stored in a table in a certain order and format to form a look-up table. To further improve the accuracy of the look-up table, interpolation processing can be performed on the data between the sampling points, such as linear interpolation or quadratic interpolation. During the detection process, when the sensor measures the distance information of the four probes, the corresponding rotor rotation angle and radial displacement can be quickly obtained by looking up the pre-compiled table. When using the look-up table method, data structures or algorithms such as hash tables and binary searches can be used to improve the look-up efficiency. Considering factors such as sensor measurement errors and motor nonlinearity, algorithms such as Kalman filtering can be used for dynamic error correction. The detection results are real-time fed back to the control system of the bearingless motor to form a closed-loop control loop. The controller dynamically adjusts the suspension current, etc., according to the error between the actual value and the reference value of the rotor position, ensuring that the motor maintains a stable operating state during high-speed rotation and improving the overall performance and reliability of the system.

[0055] The displacement synchronous detection system and method for the rotor angle of a bearingless motor provided by the embodiments of the present invention design a rotor position detection reference ring for the bearingless motor that can simultaneously reflect the rotor angle and radial displacement information, and propose a demodulation method for simultaneously detecting the rotor angle and radial displacement information. The shape of the proposed reference ring is a regular polygon, an ellipse, etc. After installing the proposed reference ring in cooperation with the eddy current sensor, the rotor angle and radial displacement can be modulated into the displacement information detected by the eddy current sensor at the same time. When the motor runs, the rotor drives the reference ring to rotate synchronously, and the eddy current sensor detects and outputs the distance voltage signal in real time, which is processed and analyzed by a digital signal processor (DSP). According to the proposed detection method, the rotor rotation angle and radial displacement information can be simultaneously demodulated from the displacement information. Through the above method, the present invention can reduce the number of required sensors, reduce the system volume requirement, simplify the system structure, and reduce the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0057] Figure 1 It is a schematic diagram of the device provided by the embodiments of the present invention.

[0058] Figure 2 Schematic diagram of the initial position of the square rotor position detection reference ring provided by the embodiment of the present invention in the coordinate system and the distribution of eddy current sensors.

[0059] Figure 3 Schematic diagram of the structure and working principle of the eddy current sensor provided by the embodiment of the present invention.

[0060] Figure 4 Schematic diagram of the output voltage varying with the rotor angle when the square rotor position detection reference ring provided by the embodiment of the present invention has no radial displacement.

[0061] Figure 5 Displacement characteristic curve of the eddy current sensor provided by the embodiment of the present invention.

[0062] Figure 6 Schematic diagram of the initial position of the elliptical rotor position detection reference ring provided by the embodiment of the present invention in the coordinate system and the distribution of eddy current sensors.

[0063] Figure 7 Schematic diagram of the output voltage varying with the rotor angle when the elliptical rotor position detection reference ring provided by the embodiment of the present invention has no radial displacement.

[0064] The reference numerals in the drawings respectively represent: rotor position detection reference ring (1); eddy current sensor probe (2); extension cable (3); preamplifier (4); DSP (5); detection surface (6); rotating shaft (7); end cover (8); bracket (9); protective bearing (10); double bolt (11); fastening nut (12); eddy current sensor (13); measured metal (14); probe coil (15); eddy current (16); alternating magnetic field (17). Detailed implementation manners

[0065] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention will be described in detail hereinafter. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary only for explaining the present invention and should not be construed as limiting the present invention. Those skilled in the art of the present technology can understand that unless specifically stated, the singular forms "a", "an", "the" and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the specification of the present invention means the presence of the described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their groups. It should be understood that when we say that an element is "connected" or "coupled" to another element, it can be directly connected or coupled to other elements, or there may also be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or coupling. The phrase "and / or" used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art of the present technology can understand that unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those of ordinary skill in the art to which the present invention belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless defined as here.

[0066] Embodiment 1:

[0067] This embodiment provides a method for synchronously detecting the rotor angle and radial displacement of a 12 / 8-pole bearingless electro-excited doubly salient motor, including a square rotor position detection reference ring 1, an eddy current sensor probe 2, an extension cable 3, a preamplifier 4, and a DSP 5. The preamplifier 4 can output a voltage signal linearly related to the gap between the probe 2 and the detection surface 6, and the DSP 5 processes and analyzes the collected signal to extract the rotational angle and radial displacement information of the rotor.

[0068] As Figure 1 shown, the rotor position detection reference ring 1 is fixed to the end of the motor shaft 7 in an interference fit manner and rotates synchronously with the motor rotor. A protective bearing 10 is installed at the floating end of the shaft 7 to support the shaft 7 when the motor is not floating. A certain gap is left between the protective bearing 10 and the shaft 7, and this gap is smaller than the air gap length between the stator and the rotor, which can prevent the rotor from rubbing against the stator when rotating.

[0069] As Figure 2As shown in the figure, two eddy current sensor probes 2 are installed in each direction of the x-axis and y-axis of the motor end cover 8, fixed by the bracket 9 and the fastening nut 12, and then the bracket 9 is fixed with double bolts 11 to prevent the bracket 9 from rotating. Y1, Y2, X1, and X2 respectively represent the eddy current sensor probes 2 in four directions. The four eddy current sensor probes 2 are evenly distributed along the circumferential direction of the motor, and the angle between each probe and the adjacent probe is 90°. The installation direction of the probes all points to the center axis of the rotor.

[0070] The rotor position detection reference ring 1 can simultaneously reflect the rotor angle and radial displacement characteristics, and its design forms include regular polygons, ellipses, etc. The reference ring 1 is made of stainless steel and needs to be precisely processed to ensure its geometric dimensions are accurate. In addition, the surface roughness of the corresponding detection surface 6 on the reference ring 1 should be strictly controlled between 0.4 μm and 0.8 μm to meet the requirements of high-precision detection.

[0071] As Figure 3 shown in the figure, the eddy current sensor 13 integrates the probe 2, the extension cable 3, and the preamplifier 4. The circuit in its preamplifier 4 generates a high-frequency current signal and sends it to the probe 2 of the sensor, generating an alternating magnetic field around the head. When the probe 2 approaches the measured metal 14, a high-frequency eddy current signal will be induced inside the measured metal 14. Due to the skin effect of high-frequency signals in conductors, the induced eddy current 16 mainly exists on the metal surface, generating an alternating magnetic field opposite to the direction of the original magnetic field. After the two are superimposed, a new magnetic field 17 is formed, causing the impedance of the probe coil 15 to change. The extension cable 3 then transmits this signal back to the preamplifier 4. After being processed by the preamplifier 4, an output voltage signal linearly related to the gap between the measured surface 6 and the probe 2 is generated.

[0072] As the rotor rotates, the rotation angle and radial displacement of the rotor change, causing the distance between the eddy current sensor probe 2 and the detection surface 6 to change, and further causing the output voltage of the eddy current sensor 13 to change. This voltage signal reflects the rotation angle and radial displacement information of the rotor.

[0073] When the rotor rotation angle is 0°, the normal directions of the four detection surfaces 6 of the reference ring 1 respectively correspond to the four basic directions of the xy coordinate system, and the rotor rotates counterclockwise. Then the law of the output voltage changing with the rotor angle is as Figure 4 shown in the figure. In the angle range of 0° to 45°, the output voltage gradually decreases as the rotor angle increases, and it is the opposite in the angle range of 45° to 90°.

[0074] As Figure 5 shown in the figure, the voltage output by the eddy current sensor 13 is linearly related to the gap between the measured surface 6 and the probe 2. When the rotor has a radial displacement, the gap distance changes, resulting in a change in the output voltage of the eddy current sensor 13.

[0075] The voltage signal output by the eddy current sensor 13 is transmitted to the DSP through the conditioning circuit, and the rotation angle and radial displacement of the rotor are obtained through DSP processing and analysis.

[0076] Set the 90° rotor rotation angle as a complete cycle of the voltage signal of the eddy current sensor 13. Divide a cycle of the voltage signal of the eddy current sensor 13 into two 45° intervals. In different intervals, the corresponding relationships between the detected distance information and the rotor angle and radial displacement are different.

[0077] Let L1, L2, L3, and L4 be the distances between the four eddy current sensor probes 2 of Y1, Y2, X1, and X2 and the detection surface 6 detected during the rotation of the rotor; d is the initial distance between the four eddy current sensor probes 2 of Y1, Y2, X1, and X2 and the detection surface 6 when the rotor rotation angle is 0°, and the value of d is 3.36 mm; a is the perpendicular distance from the geometric center of the square to any one of its sides, and the value of a is 7.5 mm; Δt is a detection cycle; ΣL t is the sum of the distances detected by the four eddy current sensors at time t. If the distances between the four eddy current sensor probes 2 of Y1, Y2, X1, and X2 and the detection surface 6 detected at time t are 2.214 mm, 2.186 mm, 2.314 mm, and 2.085 mm respectively, and ΣL t >ΣL t-Δt .

[0078] The judgment formula for the rotor rotation angle interval is

[0079]

[0080] It can be seen from formula (17) that the rotor rotation angle at time t is in the interval of 45° to 90°.

[0081] In the interval of 45° to 90°, the relationship between the rotor rotation angle and the measured distance is

[0082]

[0083] Substitute the data into formula (18) to get θ = 60°.

[0084] After obtaining the rotation angle of the rotor, combined with the distance information between the four sensor probes 2 and the detection surface 6, according to the corresponding mathematical model in this angle interval, the radial displacements of the rotor in the x-axis and y-axis directions can be calculated.

[0085] In the interval of 45° to 90°, Δx and Δy are respectively

[0086]

[0087] Substituting the data into formula (19), we can get Δx = 0.08 mm and Δy = 0.06 mm.

[0088] For a 12 / 8-pole bearingless electro-magnetic excited doubly salient motor, one electrical cycle corresponds to a 45° rotor rotation. In the range of 0° to 45°, the corresponding relationship between the rotor electrical angle and the detection result is

[0089] θ e = 8·θ (21)

[0090] In the range of 45° to 90°, the corresponding relationship between the rotor electrical angle and the detection result is

[0091] θ e = (θ - 45°)·8 (22)

[0092] At time t, the rotor electrical angle is 120°, the positive displacement of the x-axis is 0.08 mm, and the negative displacement of the y-axis is 0.06 mm.

[0093] The detection result will be fed back to the control system of the bearingless motor in real time to form a closed-loop control loop. The controller dynamically adjusts the suspension current, etc. according to the error between the actual value and the reference value of the rotor position to ensure that the motor maintains a stable operating state during high-speed rotation and improves the overall performance and reliability of the system.

[0094] Embodiment 2:

[0095] A method for synchronously detecting the rotor angle and radial displacement of a bearingless motor. The detection device is as shown in Embodiment 1, except that the rotor position detection reference ring 1 is designed as an ellipse, as Figure 6 shown.

[0096] Set the 180° rotor rotation angle as a complete eddy current sensor voltage signal period. Divide an eddy current sensor voltage signal period into two 90° intervals. In different intervals, the corresponding relationship between the detected distance information and the rotor angle and radial displacement is different.

[0097] When the reference ring 1 is an ellipse, if the rotor rotation angle is 0°, its major axis coincides with the x-axis, the minor axis coincides with the y-axis, and the rotor rotates counterclockwise. Then as Figure 7 shown, in the range of 0° to 90°, the distances between the Y1 and Y2 sensor probes and the detection surface show a decreasing trend, and the output voltage of the corresponding eddy current sensor 13 decreases. The distances between the X1 and X2 sensor probes and the detection surface show an increasing trend, and the output voltage of the corresponding eddy current sensor 13 increases. The change trend in the range of 90° to 180° is opposite to this. This change trend is used as an important basis for judging the rotor angle interval.

[0098] Let Δt be a detection period, ΣLYt 、 ΣL Xt are the total distances detected by the eddy current sensors 13 in the y-axis and x-axis directions at time t, respectively. Then, the judgment formula for the rotor rotation angle interval at time t is

[0099]

[0100] Assume that the major axis a of the ellipse is 1.35 cm, the minor axis b is 1.25 cm. When the rotor rotation angle is 0°, the initial distance between the eddy current sensor in the x-axis direction and the detection surface is 0.25 mm, and the initial distance between the eddy current sensor in the y-axis direction and the detection surface is 1.25 mm.

[0101] If the distances between the four eddy current sensor probes 2 of Y1, Y2, X1, and X2 detected at time t and the detection surface 6 are 1.139 mm, 0.900 mm, 0.650 mm, and 0.391 mm respectively, and ΣL Yt < ΣL Y(t-Δt) , ΣL Xt > ΣL X(t-Δt) . It can be seen from formula (22) that the rotor rotation angle at time t is within the range of 0° to 90°.

[0102] For the elliptical rotor position detection reference ring 1, within the corresponding interval of one cycle, after obtaining the distance information, the rotor rotation angle and radial displacement information can be obtained according to the look-up table method. By looking up the table, it can be known that the rotor rotation angle is 30°, Δx = 0.12 mm, and Δy = 0.11 mm. That is, at time t, the rotor rotation angle is 30°, the positive displacement in the x-axis direction is 0.12 mm, and the negative displacement in the y-axis direction is 0.11 mm.

[0103] When using the look-up table method, data structures or algorithms such as hash tables and binary searches can be used to improve the search efficiency. Considering factors such as sensor measurement errors and motor nonlinearities, algorithms such as Kalman filtering can be used for dynamic error correction. The detection results will be real-time fed back to the control system of the bearingless motor to form a closed-loop control loop. The controller dynamically adjusts the suspension current, etc. according to the error between the actual value and the reference value of the rotor position to ensure that the motor maintains a stable operating state during high-speed rotation and improve the overall performance and reliability of the system.

[0104] The main advantages of this embodiment are as follows: 1. By utilizing the characteristics that the position detection reference ring of a regular polygon or elliptical rotor has both rotor angle and radial displacement characteristics, the types and quantities of required sensors are reduced, saving motor space and lowering system complexity and cost. 2. It can reflect the specific rotation angle of the rotor rather than a rough angle range, improving the accuracy of rotor angle detection. At the same time, it can also measure the radial displacement of the rotor, being applicable to application scenarios that require both precise control of the rotor angle and real-time monitoring of the radial displacement. 3. The calculation method of this solution is relatively simple and has low requirements for signal processing technology, thus enabling a relatively fast detection speed. This is crucial for high-speed motor systems because the rapidly rotating rotor needs to quickly and accurately obtain its position and displacement information to ensure system stability and reliability. 4. The design of the rotor position detection reference ring has a high degree of flexibility and can be adjusted according to the structure and type of the motor. This means that this invention can be applied to various types and structures of bearingless motors, and this wide applicability makes this invention have potential application value in multiple fields such as industrial automation, robotics, aerospace, and medical devices.

[0105] Generally speaking, this solution adopts a non-contact measurement form and has advantages such as strong anti-interference ability, stable and reliable long-term operation, high sensitivity, high resolution, and strong environmental adaptability. The proposed method for synchronous detection of rotor angle and radial displacement of a bearingless motor is applicable to various high-performance bearingless motor systems such as bearingless electro-magnetic double salient motors, bearingless switched reluctance motors, bearingless permanent magnet synchronous motors, and bearingless flux-switching motors. In addition, this detection method realizes the synchronous detection of the rotor angle and radial displacement of a bearingless motor, reduces the number of required sensors, can simplify the system structure, save occupied space, and reduce manufacturing costs.

[0106] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the device embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and for the relevant parts, reference can be made to the partial description of the method embodiments. As described above, the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A displacement synchronous detection system for the rotor angle of a bearingless motor, characterized in that The rotor position detection reference ring (1) is fixed on the rotating shaft (7) of the bearingless motor; The bracket (9) is fixed on the end cover (8) of the bearingless motor by double bolts (11), and an eddy current sensor (13) is also installed on the motor end cover (8); The eddy current sensor probe (2) of the eddy current sensor (13) is fixed on the bracket (9) and fixed by a fastening nut (12), and the eddy current sensor probe (2) faces the detection surface (6) of the rotor position detection reference ring (1).

2. The system according to claim 1, characterized in that, The cross-sectional shape of the rotor position detection reference ring (1) is a regular polygon or an ellipse.

3. The system according to claim 2, wherein The rotor position detection reference ring (1) is fixed on the motor rotating shaft (7) in an interference fit manner to synchronously rotate with the rotating shaft (7) of the bearingless motor; The material for making the rotor position detection reference ring (1) is stainless steel.

4. The system according to claim 3, wherein Two eddy current sensors (13) are installed in the x-axis direction and the y-axis direction of the motor end cover (8), and the four eddy current sensor probes (2) are Y1, Y2, X1, and X2 respectively; Y1, Y2, X1, and X2 are evenly distributed along the circumferential direction of the motor, and the angle between each probe and the adjacent probe is 90°, and the installation direction of the probes all points to the center axis of the rotor.

5. The system according to claim 4, wherein The components of the eddy current sensor (13) also include a preamplifier (4), the preamplifier (4) is connected to the eddy current sensor probe (2) through an extension cable (3), and the preamplifier (4) is also connected to the DSP (5); The preamplifier (4) includes: an oscillator, a detection circuit, an amplifier, and a linear correction circuit.

6. The system according to claim 5, characterized in that, The preamplifier (4) is used to provide a high-frequency alternating current for the probe coil (15) of the eddy current sensor probe (2), and record the change of the probe parameters caused by the approach of the detection surface (6) as a metal conductor to the eddy current sensor probe (2); The probe parameters include: an output voltage signal linearly related to the gap between the detection surface (6) and the end face of the eddy current sensor probe (2); after the voltage signal is transmitted to the DSP (5), the DSP (5) obtains the rotor motion parameters, including the rotation angle and radial displacement of the rotor.

7. A displacement synchronization detection method for the rotor angle of a bearingless motor, characterized in that, Including: S1. After the bearingless motor starts, as the gap between the eddy current sensor probe (2) and the detection surface (6) changes, the eddy current sensor (13) collects the corresponding output voltage signal in real time, and this signal is linearly related to the gap between the detection surface (6) and the end face of the eddy current sensor probe (2); S2. Divide the voltage signal collected by the eddy current sensor (13) according to intervals, and establish the corresponding relationship within different intervals. The corresponding relationship includes: the corresponding relationship between the distance information between the eddy current sensor probe (2) and the detection surface (6) and the motion parameters of the rotor; S3. Identify the rotation angle interval of the rotor and determine the rotation angle of the rotor of the bearingless motor; S4. Use the rotation angle of the rotor of the bearingless motor to obtain the radial displacements of the rotor in the x-axis and y-axis directions. Among them, the obtained radial displacements are fed back to the control system of the bearingless motor for closed-loop control.

8. The method according to claim 7, wherein In S2, dividing the voltage signal collected by the eddy current sensor (13) according to the intervals of the rotor rotation angle and establishing the corresponding relationships in different intervals includes: When the rotor rotation angle is 0°, the normal directions of the four detection surfaces of the rotor position detection reference ring (1) respectively correspond to the four basic directions of the xy coordinate system, and the rotor rotates counterclockwise; Among them, in the angle interval of 0° to 45°, the distance between the eddy current sensor probe (2) and the detection surface (6) shows a decreasing trend, and the distance between the eddy current sensor probe (2) and the detection surface (6) is the smallest at 45°; In the angle interval of 45° to 90°, the change trend of the distance between the eddy current sensor probe (2) and the detection surface (6) is opposite to that in the angle interval of 0° to 45°; 9. The method according to claim 8, wherein At time t, the determination method of the interval of the rotor rotation angle is: where Δt represents a detection period, and ΣL t represents the total distance detected by the four eddy current sensors (13) at time t.

10. The method according to claim 9, wherein In the angular range of 0° to 45°, the correspondence between the distance information between the eddy current sensor probe (2) and the detection surface (6) and the motion parameters of the rotor is as follows: d represents the initial distance when the rotor rotation angle is 0°, a represents the perpendicular distance from the geometric center of the rotor position detection reference ring (1) to any one of its sides, L i represents the distance between each eddy current sensor probe (2) and the detection surface (6), and θ represents the rotor angle; In the angle range of 45° to 90°, the correspondence between the distance information between the eddy current sensor probe (2) and the detection surface (6) and the motion parameters of the rotor is as follows:

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