A method for measuring the skew polar angle of a brushless motor rotor

Abstract

The present invention discloses a method for measuring the skew polar angle of a brushless motor rotor, comprising the following steps: controlling a servo motor to drive a brushless motor rotor to be measured to rotate at a constant speed; each Hall sensor real-timely collecting voltage fluctuation data of a magnetic flux signal, an angle encoder real-timely collecting rotation angle data of the rotor, and forming a magnetic flux density curve based on the voltage fluctuation data and the rotation angle data; solving the angle difference of magnets between layers based on each magnetic flux density curve; and obtaining the skew polar angle of the brushless motor to be measured based on the angle difference of magnets between layers. Compared with measuring the skew polar angle by a mechanical method, the skew polar angle measured by this method has a more accurate measurement result and can better cope with motor torque fluctuations caused by rotor magnetic lines of force.

Description

[0001] This case is a divisional application of the patent application with application number 201910662967.9, application date 2019-07-22, and title “A method for measuring the skew pole angle of a brushless motor rotor based on magnetic flux density” as the parent case. Technical Field

[0002] The present invention relates to the field of motor rotor skew polar angle measurement, and in particular to a brushless motor rotor skew polar angle measurement method. Background Art

[0003] Cogging torque is a key performance metric for brushless motors, and the rotor's skew angle significantly impacts cogging torque. The rotor's external structure is typically featureless, making skew angle measurement difficult. Rotors typically have six or more poles, making measurement challenging. After magnetization, rare earth magnets create an extremely strong magnetic field, typically exceeding 3300 mT, making skew angle measurement difficult using mechanical methods. Summary of the Invention

[0004] In view of the defects of the prior art, the technical problem to be solved by the present invention is to provide a method for measuring the skew pole angle of a brushless motor rotor based on magnetic flux density, aiming to solve the problem that the skew pole angle of the motor rotor is difficult to be accurately measured by mechanical methods.

[0005] To achieve the above object, the present invention provides a method for measuring the skew polar angle of a brushless motor rotor based on magnetic flux density, characterized in that the method comprises the following steps:

[0006] Step S1: Controlling a servo motor to drive the rotor of a brushless motor to be tested to rotate at a constant speed; the rotor of the brushless motor to be tested includes N layers of magnets, each layer of the magnets includes M poles, and the magnets in each layer are staggered; N Hall sensors are sequentially provided on the periphery of each layer of the magnets in the rotor of the brushless motor to be tested along the axial direction of the rotor, the Hall sensors corresponding one to one to each layer of the magnets, and the rotor is also connected to a first angle encoder;

[0007] Step S2: Each of the Hall sensors collects voltage fluctuation data of the magnetic flux signal in real time, and the first angle encoder collects rotation angle data of the rotor in real time, and forms a magnetic flux density curve B according to the voltage fluctuation data and the rotation angle data. i (θ); i is the layer number of the magnet, and the rotation angle θ collected by the first angle encoder is used as the magnetic flux density curve B i The abscissa of (θ);

[0008] Step S3: According to each of the magnetic flux density curves B i (θ), solve for the angle difference Δθ between the magnets in each layer (a,b); a and b are numbers of the magnetic flux density curves;

[0009] Step S4: According to the angle difference Δθ between the magnets in each layer (a,b) , obtain the skew polar angle of the brushless motor to be tested

[0010] In this technical solution, compared with the traditional mechanical method of measuring the oblique polar angle, the oblique polar angle measured by this method has more accurate measurement results and can better cope with the motor torque fluctuations caused by the rotor magnetic lines.

[0011] Furthermore, the step S2 further includes:

[0012] For the magnetic flux density curve B i (θ) performs high-frequency filtering, wherein the frequency of the high-frequency filtering is greater than 5MNω / 2π.

[0013] It is worth mentioning that high-frequency filtering cannot affect the magnetic flux density curve B i The overall waveform of (θ) is as follows: each layer of the brushless motor contains M magnets, and during one revolution of the rotor there are M / 2 peaks and troughs, and there are N layers, so the frequency of the high-frequency filter is set to be greater than 5MNω / 2π.

[0014] In this technical solution, by the magnetic flux density curve B i (θ) performs high frequency filtering to improve the magnetic flux density curve B i The accuracy of (θ) makes the calculated angle difference Δθ between the magnets in each layer (a,b) More accurate.

[0015] Furthermore, step S3 includes:

[0016] Step S31, specify the magnetic flux density B set ;

[0017] Step S32: According to the specified magnetic flux density B set , obtain each of the magnetic flux density curves B i (θ) reaches the magnetic flux density B set The corresponding rotation angle θ i ;

[0018] Step S33: according to the rotation angle θ i , obtain each magnetic flux density curve B i (θ) the magnet angle difference Δθ between (a,b) .

[0019] In this technical solution, according to the specified magnetic flux density B set and the respective magnetic flux density curves B i(θ) can be used to get the angle difference Δθ between the magnets in each layer (a,b) The method is simple and the data obtained are accurate.

[0020] Furthermore, the step S3 further includes:

[0021] According to the magnetic flux density curve B i (θ), respectively obtain the magnet angle difference Δθ of each pole of each layer (a,b,c) ; The c is the pole number;

[0022] In this technical solution, the angle difference Δθ of the magnets of each pole in each layer is obtained. (a,b,c) , so that the angle difference between the magnets in each layer is Δθ (a,b) More specific.

[0023] Furthermore, in step S4, according to the angle difference Δθ between the magnets in each layer, (a,b) , obtain the skew polar angle of the brushless motor to be tested Also includes:

[0024] The angle difference Δθ between the magnets in each layer (a,b) The average value of the oblique polar angle

[0025] In this technical solution, the angle difference Δθ between the magnets in each layer is (a,b) The average value of the oblique polar angle Achieved the skew polar angle of the brushless motor rotor to be tested measurement.

[0026] Furthermore, the method further comprises:

[0027] The calculated oblique polar angle Compare with the set limit value β to determine whether the brushless motor rotor to be tested is qualified;

[0028] If the brushless motor rotor to be tested is unqualified, an alarm is output;

[0029] If the brushless motor rotor to be tested is qualified, a qualified label is printed out and affixed to the brushless motor rotor.

[0030] In this technical solution, whether the brushless motor rotor to be tested is qualified is predicted in advance through online detection.

[0031] The beneficial effects of the present invention are as follows: in the present invention, the motor rotor skew angle can be calculated through the magnetic flux density curve; compared with measuring the skew angle by mechanical methods, the skew angle measured by this method can better cope with the motor torque fluctuations caused by the rotor magnetic lines; it is applied to online detection to predict in advance whether the motor slot torque exceeds the specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flowchart of a specific embodiment of the present invention;

[0033] Figure 2 1 is a schematic structural diagram of a brushless motor rotor magnetic flux measurement mechanism according to a specific embodiment of the present invention;

[0034] Figure 3 1 is a front view of a brushless motor rotor magnetic flux measuring mechanism according to a specific embodiment of the present invention;

[0035] Figure 4 is a magnetic flux density curve diagram of a specific embodiment of the present invention;

[0036] Figure 5 It is a partial enlarged view of a magnetic flux density curve of a specific embodiment of the present invention;

[0037] Figure 6 is a calculation data diagram of a specific embodiment of the present invention;

[0038] Figure 7 It is a structural schematic diagram of a brushless motor rotor to be tested according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the accompanying drawings and examples:

[0040] like Figure 1 The flowchart of this embodiment includes the following steps:

[0041] Step S1: Controlling a servo motor to drive the rotor of a brushless motor to be tested to rotate at a constant speed; the rotor of the brushless motor to be tested includes N layers of magnets, each layer of the magnets includes M poles, and the magnets in each layer are staggered; N Hall sensors are sequentially provided along the axial direction of the rotor around each layer of the magnets in the rotor of the brushless motor to be tested, the Hall sensors corresponding one to one with each layer of the magnets, and the rotor is also connected to a first angle encoder 500;

[0042] Step S2: Each of the Hall sensors collects voltage fluctuation data of the magnetic flux signal in real time, and the first angle encoder 500 collects the rotation angle data of the rotor in real time, and forms a magnetic flux density curve B according to the voltage fluctuation data and the rotation angle data. i(θ); i is the layer number of the magnet, and the rotation angle θ collected by the first angle encoder 500 is used as the magnetic flux density curve B i The abscissa of (θ);

[0043] Step S3: According to each of the magnetic flux density curves B i (θ), solve for the angle difference Δθ between the magnets in each layer (a,b) ; a and b are numbers of the magnetic flux density curves;

[0044] Step S4: According to the angle difference Δθ between the magnets in each layer (a,b) , obtain the skew polar angle of the brushless motor to be tested

[0045] The present invention will be described below by way of examples:

[0046] The method is implemented on a brushless motor rotor magnetic flux measurement mechanism, which includes a positioning assembly 100, a support frame 200, and a measuring assembly 300; the measuring assembly 300 includes a positioning rod 301, a measuring member 302, and a movable assembly mounted on the positioning rod 301, the movable assembly including a first movable member 303 and a second movable member 304; the measuring member 302 includes a measuring end and a rotating end, and the measuring end is equipped with a Hall sensor; the measuring assembly 300 is mounted on the support frame 200 through the positioning rod 301; the positioning assembly 100 is mounted on the support frame 200; the brushless motor to be measured is mounted on the positioning assembly 100 The motor rotor 400 and the first angle encoder 500, the brushless motor rotor 400 to be tested includes N layers of magnets, each layer of the magnets includes M poles, and the magnets in each layer are staggered; the periphery of the magnets in each layer of the rotor of the brushless motor to be tested is sequentially provided with N Hall sensors along the axial direction of the rotor, and the Hall sensors correspond one-to-one to the magnets in each layer; the positioning assembly 100 includes a first positioning sleeve 101, a second positioning sleeve 102, a first sleeve 103, and a second sleeve 104; the support frame 200 includes two support side plates 201, a first support plate 202, a second support plate 203, and a support bottom plate 204; an operating box 600 is also installed on the support frame 200.

[0047] In this embodiment, if Figure 6 As shown, the brushless motor rotor 400 to be tested is divided into three layers, each layer has 8 magnets, and forms 8 poles after magnetization.

[0048] A first embodiment of the present invention provides a method for measuring the skew angle of a brushless motor rotor based on magnetic flux density, comprising the following steps:

[0049] Step S1: Controlling a servo motor to drive the rotor of a brushless motor to be tested to rotate at a constant speed; the rotor of the brushless motor to be tested includes N layers of magnets, each layer of the magnets includes M poles, and the magnets in each layer are staggered; N Hall sensors are sequentially provided along the axial direction of the rotor around each layer of the magnets in the rotor of the brushless motor to be tested, the Hall sensors corresponding one to one with each layer of the magnets, and the rotor is also connected to a first angle encoder 500;

[0050] Step S2: Each of the Hall sensors collects voltage fluctuation data of the magnetic flux signal in real time, and the angle encoder 500 collects the rotation angle data of the rotor in real time, and forms a magnetic flux density curve B according to the voltage fluctuation data and the rotation angle data. i (θ); i is the layer number of the magnet, and the rotation angle θ collected by the first angle encoder 500 is used as the magnetic flux density curve B i (θ) horizontal axis; magnetic flux density curve B i (θ) Figure 4 As shown: there are three flux curves in total, each curve has 4 cycles, corresponding to the 8 poles of the rotor;

[0051] Specifically, the step S2 further includes:

[0052] For the magnetic flux density curve B i (θ) performs high-frequency filtering, wherein the frequency of the high-frequency filtering is greater than 5MNω / 2π.

[0053] It is worth mentioning that high-frequency filtering cannot affect the magnetic flux density curve B i The overall waveform of (θ) is as follows: each layer of the brushless motor contains M magnets, and during one revolution of the rotor there are M / 2 peaks and troughs, and there are N layers, so the frequency of the high-frequency filter is set to be greater than 5MNω / 2π.

[0054] Step S3: According to each of the magnetic flux density curves B i (θ), solve for the angle difference Δθ between the magnets in each layer (a,b) ; a and b are numbers of the magnetic flux density curves;

[0055] Specifically, step S3 includes:

[0056] Step S31, specify the magnetic flux density B set ;

[0057] Step S32: According to the specified magnetic flux density B set , obtain each of the magnetic flux density curves B i (θ) reaches the magnetic flux density B set The corresponding rotation angle θ i ;

[0058] Step S33: according to the rotation angle θ i , obtain each magnetic flux density curve B i (θ) the magnet angle difference Δθ between (a,b) .

[0059] The step S3 further includes:

[0060] According to the magnetic flux density curve B i (θ), respectively obtain the magnet angle difference Δθ of each pole of each layer (a,b,c) ; The c is the pole number;

[0061] like Figure 4 The 8 boxes shown can be used to calculate the magnet angle difference Δθ (a,b) , to enlarge the description of the first box from the left, such as Figure 5 As shown:

[0062] A is the angle difference between the first magnet in the first layer and the first magnet in the second layer;

[0063] B is the angle difference between the first magnet of the second layer and the first magnet of the third layer;

[0064] The angle difference Δθ of all magnets is (a,b) Calculate, the result is Figure 6 As shown:

[0065] Step S4: According to the angle difference Δθ between the magnets in each layer (a,b) , obtain the skew polar angle of the brushless motor to be tested

[0066] In step S4, according to the angle difference Δθ between the magnets in each layer (a,b) , obtain the rotor skew angle of the brushless motor to be tested Also includes:

[0067] The angle difference Δθ between the magnets in each layer (a,b) The average value of the oblique polar angle

[0068] Optionally, the angle difference Δθ between the magnets in each layer is (a,b) The weighted average of the slant polar angle

[0069] Furthermore, the method further comprises:

[0070] The calculated oblique polar angle Compare with the set limit value β to determine whether the brushless motor rotor 400 to be tested is qualified;

[0071] If the brushless motor rotor 400 to be tested is unqualified, an alarm is output;

[0072] If the brushless motor rotor 400 to be tested is qualified, a qualified label is printed out and affixed to the brushless motor rotor.

[0073] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for measuring the skew polar angle of a brushless motor rotor, characterized in that: The method comprises the following steps: Step S1: Controlling a servo motor to drive the rotor of a brushless motor to be tested to rotate at a constant speed; the rotor of the brushless motor to be tested includes N layers of magnets, each layer of the magnets includes M poles, and the magnets in each layer are staggered; N Hall sensors are sequentially provided on the periphery of each layer of the magnets in the rotor of the brushless motor to be tested along the axial direction of the rotor, the Hall sensors corresponding one to one to each layer of the magnets, and the rotor is also connected to a first angle encoder; Step S2: Each of the Hall sensors collects voltage fluctuation data of the magnetic flux signal in real time, and the first angle encoder collects rotation angle data of the rotor in real time, and forms a magnetic flux density curve B according to the voltage fluctuation data and the rotation angle data. i (θ); i is the layer number of the magnet, and the rotation angle θ collected by the first angle encoder is used as the magnetic flux density curve B i (θ) is the horizontal coordinate; Step S3: According to each of the magnetic flux density curves B i (θ), solve for the angle difference Δθ between the magnets in each layer (a,b) ; a and b are numbers of the magnetic flux density curves; Step S4: According to the angle difference Δθ between the magnets in each layer (a,b) , the angle difference Δθ between the magnets in each layer (a,b) The average value of the oblique polar angle Obtain the slant polar angle of the brushless motor to be tested The method is implemented on a brushless motor rotor magnetic flux measurement mechanism, which comprises a positioning assembly (100), a support frame (200), and a measuring assembly (300); the measuring assembly (300) comprises a positioning rod (301), a measuring member (302), and a movable assembly mounted on the positioning rod (301), the movable assembly comprising a first movable member (303) and a second movable member (304); the measuring member (302) comprises a measuring end and a rotating end, the measuring end being equipped with a Hall sensor; the measuring assembly (300) is mounted on the support frame (200) via the positioning rod (301); the positioning assembly (100) is mounted on the support frame (200); a brushless motor to be measured is mounted on the positioning assembly (100) A brushless motor rotor (400) and a first angle encoder (500) are provided. The brushless motor rotor (400) to be tested comprises N layers of magnets, each layer of the magnets comprises M poles, and the magnets in each layer are staggered. N Hall sensors are sequentially arranged on the periphery of each layer of the magnets of the brushless motor rotor to be tested along the axial direction of the rotor, and the Hall sensors correspond one to one to the magnets in each layer. The positioning assembly (100) comprises a first positioning sleeve (101), a second positioning sleeve (102), a first sleeve (103), and a second sleeve (104). The support frame (200) comprises two support side plates (201), a first support plate (202), a second support plate (203), and a support bottom plate (204). An operating box (600) is also installed on the support frame (200).

2. A brushless motor rotor skew angle measurement method according to claim 1, characterized in that: The brushless motor rotor (400) to be tested is divided into three layers, each layer has 8 magnets, and 8 poles are formed after magnetization.

3. The method for measuring the skew polar angle of a brushless motor rotor according to claim 1, wherein: The step S2 further includes: For the magnetic flux density curve B i (θ) performs high-frequency filtering, wherein the frequency of the high-frequency filtering is greater than 5MNω / 2π.

4. The method for measuring the skew polar angle of a brushless motor rotor according to claim 1, wherein: The step S3 comprises: Step S31, specify the magnetic flux density B set ; Step S32: According to the specified magnetic flux density B set , obtain each of the magnetic flux density curves B i (θ) reaches the magnetic flux density B set The corresponding rotation angle θ i ; Step S33: according to the rotation angle θ i , obtain each magnetic flux density curve B i (θ) the magnet angle difference Δθ between (a,b) .

5. The method for measuring the skew polar angle of a brushless motor rotor according to claim 1, wherein: The step S3 further includes: According to the magnetic flux density curve B i (θ), respectively obtain the magnet angle difference Δθ of each pole of each layer (a,b,c) ; The c is the pole number; 6. The method for measuring the skew polar angle of a brushless motor rotor according to claim 1, wherein: The method further comprises: The calculated oblique polar angle Compare with the set limit value β to determine whether the brushless motor rotor to be tested is qualified; If the brushless motor rotor to be tested is unqualified, an alarm is output; If the brushless motor rotor to be tested is qualified, a qualified label is printed out and affixed to the brushless motor rotor.

Images