CN114499057A - Method for eliminating magnetic interference of brushless direct current motor - Google Patents
Method for eliminating magnetic interference of brushless direct current motor Download PDFInfo
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- CN114499057A CN114499057A CN202210248214.5A CN202210248214A CN114499057A CN 114499057 A CN114499057 A CN 114499057A CN 202210248214 A CN202210248214 A CN 202210248214A CN 114499057 A CN114499057 A CN 114499057A
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- 238000001514 detection method Methods 0.000 abstract description 11
- 230000000694 effects Effects 0.000 description 6
- 238000004422 calculation algorithm Methods 0.000 description 4
- 230000008030 elimination Effects 0.000 description 3
- 238000003379 elimination reaction Methods 0.000 description 3
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
- H02K11/02—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection for suppression of electromagnetic interference
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T3/00—Geometric image transformations in the plane of the image
- G06T3/40—Scaling of whole images or parts thereof, e.g. expanding or contracting
- G06T3/4007—Scaling of whole images or parts thereof, e.g. expanding or contracting based on interpolation, e.g. bilinear interpolation
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2218/00—Aspects of pattern recognition specially adapted for signal processing
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/64—Electric machine technologies in electromobility
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Abstract
The invention discloses a method for eliminating magnetic interference of a brushless direct current motor, which eliminates the magnetic interference of the brushless direct current motor on a magnetometer by establishing the relation between the rotating speed of the brushless direct current motor and the magnetic interference, and smoothes the signals of the rotating speed and the magnetic interference of the brushless direct current motor to obtain signals without the magnetic interference. The method can effectively eliminate the interference of the brushless direct current motor to the received signal of the magnetometer, and improve the detection accuracy of the magnetometer.
Description
Technical Field
The invention relates to the field of signal magnetic elimination, in particular to a method for eliminating magnetic interference of a brushless direct current motor.
Background
Brushless dc motors can interfere with magnetometers operating around them during operation. Most of the previous research has focused on adding a shielding cover to the brushless dc motor or optimizing the structure of the brushless dc motor to reduce magnetic interference, such as patent nos. CN210927364U and CN208143025U, but this method requires changing or replacing the existing structure. Some studies also propose algorithms to eliminate magnetic interference, but the algorithms are more complex and not suitable for real-time systems.
The detection of the submarine cable plays a very important role in maintaining and repairing the submarine cable and ensuring the smoothness of communication and power transmission. The detection, maintenance and repair of submarine cables is usually based on Remote Operated Vehicle (ROV) platforms. The signal acquired by the magnetometer carried by the ROV is an important basis for magnetic detection of submarine cables. In recent years, as ROVs have been increased in size and become more motorized, the efficiency of maintaining submarine cables has been increasing. However, the magnetic field generated during the operation of the brushless dc motor can seriously interfere with the signal of the magnetometer carried by the ROV, thereby greatly reducing the accuracy of detecting the submarine cable by using the magnetometer. Furthermore, other tasks that require the use of magnetometers, such as detection of the earth's magnetic field, detection of unexploded bombs (UXO) on the sea floor, are affected.
It is therefore necessary to eliminate magnetometer interference caused by brushless dc motors. The invention mainly researches the interference characteristic of the motor magnetic field, provides the relation between the magnetic interference frequency and the motor rotating speed, and provides a feasible method for inhibiting the influence of interference on the magnetometer signal, thereby improving the accuracy of the submarine cable positioning by using the magnetometer.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for eliminating the magnetic interference of a brushless direct current motor, which can ensure that the detection accuracy of a magnetometer is improved and the algorithm complexity is low.
The purpose of the invention is realized by the following technical scheme:
a brushless DC motor magnetic interference elimination method, utilize brushless DC motor rotational speed and magnetic interference relation of the frequency to eliminate the interference, the following step of this method:
s1: acquiring a magnetometer original signal with brushless direct current motor magnetic interference;
s2: filtering the original signal of the magnetometer with the magnetic interference of the brushless direct current motor;
s3: obtaining the envelope surface s of the filtered signalEnv；
S4: collecting the rotating speed of the brushless direct current motor which is the same as the starting and stopping time period of the magnetometer original signal;
s5: according to the relation between the rotating speed of the brushless DC motor and the magnetic interference frequency, calculating to obtain n of the rotating speed of the brushless DC motor, setting a speed interval including n, and transmitting a signal s of the brushless DC motor in a corresponding time period of the speed intervalEnvDiscarding;
the relationship between the rotating speed of the brushless direct current motor and the magnetic interference frequency is as follows:
wherein, p is the number of the magnetic pole pairs of the brushless DC motor, n is the rotating speed of the brushless DC motor, and the unit is RPM, f is the frequency of the magnetic interference generated by the brushless DC motor, and the unit is Hz;
s6: filling the signal interval discarded in the step S5 by adopting an interpolation method to obtain a signal SIC；
S7: for signal sICSmoothing is carried out to obtain a signal s without magnetic interferencefinal。
Further, the interpolation method in S6 is linear interpolation.
Further, in S7, the signal S is processed by wavelet methodICSmoothing is performed.
Further, in S5, when the calculated n of the rotation speed of the brushless dc motor is less than 1000rpm, a deviation between the upper and lower thresholds of the speed interval and n is 20% to 50%; and when the calculated n of the rotating speed of the brushless direct current motor is more than or equal to 1000rpm, the deviation between the upper threshold and the lower threshold of the speed interval and the n is 5-50%.
Further, the utilization rate is smallWave method for signal sICThe smoothing is carried out by the following specific steps:
(1) selecting the number L of layers of wavelet decomposition and the type of the decomposition wavelet;
(2) calculating a signal sICWavelet decomposition at the L-th layer;
(3) calculating a threshold value for each layer from the first layer to the lth layer;
(4) and processing the detail coefficient by applying a soft threshold method;
(5) computing a magnetic interference free signal s from threshold processing detail coefficients of the order from 1 to Lfinal。
The invention has the following beneficial effects:
(1) the method for eliminating the magnetic interference of the brushless direct current motor provides the relation between the rotating speed of the brushless direct current motor and the magnetic interference frequency, and can provide reference for the following invention.
(2) The method for eliminating the magnetic interference of the brushless direct current motor can effectively eliminate the influence of the brushless direct current motor on the magnetometer.
(3) The method for eliminating the magnetic interference of the brushless direct current motor has the advantages of low algorithm complexity and small burden on a system.
(4) The method for eliminating the magnetic interference of the brushless direct current motor is suitable for underwater ROV magnetic detection, and improves the detection accuracy.
Drawings
FIG. 1 is a flow chart of the method.
Fig. 2 shows the single channel interference cancellation effect.
Fig. 3 is a signal comparison diagram at different stages of processing.
Fig. 4 is a comparison graph of positioning effects before and after signal interference cancellation.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments, and the objects and effects of the present invention will become more apparent, it being understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.
As shown in fig. 1, the method for eliminating magnetic interference of a brushless dc motor of the present invention specifically includes the following steps:
s1: acquiring a magnetometer original signal with brushless direct current motor magnetic interference;
s2: filtering the original signal of the magnetometer with the magnetic interference of the brushless direct current motor;
s3: obtaining the envelope surface s of the filtered signalEnv；
S4: collecting the rotating speed of the brushless direct current motor which is the same as the starting and stopping time period of the magnetometer original signal;
s5: calculating n of the rotating speed of the brushless direct current motor according to the relation between the rotating speed of the brushless direct current motor and the magnetic interference frequency, setting a speed interval including n, and when the rotating speed of the motor reaches the speed, enabling a signal s of the brushless direct current motor in a corresponding time period of the speed intervalEnvAnd (5) discarding.
The specific derivation of the relationship between the rotating speed of the brushless direct current motor and the magnetic interference frequency is as follows:
the brushless direct current motor is composed of a stator, a rotor and a commutator, when the rotor rotates in a main magnetic field generated by the stator, an armature winding on the rotor can cut a magnetic induction line to generate electromotive force, the generated electromotive force causes fluctuation of current, and the fluctuation of the current forms a leakage magnetic field outwards through an antenna effect of an electric wire outside the motor. This leakage field is external magnetic interference to the magnetometer. If the number of the magnetic pole pairs of the motor is m, when the rotating speed is constant, the running condition of each group of the magnetic pole pairs is the same, which can be regarded as a period, and the magnetic field radiated outwards is the same, so that the corresponding relation between the frequency of the leakage magnetic field radiated outwards and the rotating speed of the brushless direct current motor is as follows:
wherein, p is the number of the magnetic pole pairs of the brushless DC motor, n is the rotating speed of the brushless DC motor, and the unit is RPM, and f is the frequency of the magnetic interference generated by the brushless DC motor, and the unit is Hz.
S6: by means of a socketThe value method fills the signal interval discarded in step S5 to obtain signal SIC. The interpolation method preferably adopts a linear difference value, is simple and convenient to operate and has small calculation amount.
S7: for signal sICSmoothing is carried out to obtain a signal s without magnetic interferencefinal. Smoothing the signal can be performed by various methods, preferably by a wavelet method, and the signal s is smoothed by the wavelet methodICThe smoothing is carried out by the following specific steps:
(1) selecting the number L of layers of wavelet decomposition and the type of the decomposition wavelet;
(2) calculating a signal sICWavelet decomposition at the L-th layer;
(3) calculating a threshold value for each layer from the first layer to the lth layer;
(4) and processing the detail coefficient by applying a soft threshold method;
(5) computing a magnetic interference free signal s from threshold processing detail coefficients of the order from 1 to Lfinal。
The method for eliminating the magnetic interference of the brushless direct current motor is specifically applied to the detection of submarine cables. In the underwater scene, the original signals are obtained by introducing current with any frequency of 0-50 Hz into the submarine cable and obtaining the original signals by the ROV carrying the magnetometer in the motion process.
In this embodiment, a current of 25Hz is applied to the submarine cable, the large-scale electric ROV mounted magnetometer detects the magnetic signal emitted from the submarine cable, and the acquired magnetic signal must contain time information for aligning with time data contained in the rotating speed v of the brushless dc motor. The acquired magnetometer signals are filtered using a band pass filter. The center frequency of the band-pass filter is 25Hz, and the pass-band width is 2 Hz. Then carrying out envelope detection on the filtered signal to obtain an envelope signal sEnv。sEnvIncluding time data. The rotation speed of the brushless DC motor is obtained by a brushless DC motor rotation speed v sensor and contains time data.
The position information of the submarine cable in the magnetometer, i.e. the magnetic signal frequency of the submarine cable, is 25 Hz. According to formula (1), corresponding toThe brush dc motor speed is 300 RPM. The speed bandwidth is thus set to 200RPM-400RPM, and when the speed is within this range, the signal sEnvThe corresponding time section is partially discarded, and the vacancy is filled by a linear interpolation method. The signal subjected to interference cancellation is a signal sIC. The interference cancellation effect is shown in fig. 2.
In this embodiment, the signal s is wavelet processedICSmoothing is performed and the wavelet selected is the sym4 wavelet in Symlet, decomposing the signal to level 12. The signal pairs for the different processing stages are shown in fig. 3. The final signal positioning effect after interference cancellation is shown in fig. 4. By using the interference elimination method of the brushless direct current motor, the positioning error of the magnetometer is reduced by more than 80%.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and although the invention has been described in detail with reference to the foregoing examples, it will be apparent to those skilled in the art that various changes in the form and details of the embodiments may be made and equivalents may be substituted for elements thereof. All modifications, equivalents and the like which come within the spirit and principle of the invention are intended to be included within the scope of the invention.
Claims (5)
1. A method for eliminating magnetic interference of a brushless direct current motor is characterized in that the relationship between the rotating speed of the brushless direct current motor and the magnetic interference frequency is utilized to eliminate the interference, and the method comprises the following steps:
s1: acquiring a magnetometer original signal with brushless direct current motor magnetic interference;
s2: filtering the original signal of the magnetometer with the magnetic interference of the brushless direct current motor;
s3: obtaining the envelope surface s of the filtered signalEnv；
S4: collecting the rotating speed of the brushless direct current motor which is the same as the starting and stopping time period of the magnetometer original signal;
s5: calculating n of the brushless DC motor rotation speed according to the relation between the brushless DC motor rotation speed and the magnetic interference frequency, and settingSetting a speed interval including n, and enabling the brushless direct current motor to be at a signal s of a corresponding time period of the speed intervalEnvDiscarding;
the relation between the rotating speed of the brushless direct current motor and the magnetic interference frequency is as follows:
wherein, p is the number of the magnetic pole pairs of the brushless DC motor, n is the rotating speed of the brushless DC motor, and the unit is RPM, f is the frequency of the magnetic interference generated by the brushless DC motor, and the unit is Hz;
s6: filling the signal interval discarded in the step S5 by adopting an interpolation method to obtain a signal SIC；
S7: for signal sICSmoothing is carried out to obtain a signal s without magnetic interferencefinal。
2. The method of eliminating magnetic interference in a brushless dc motor according to claim 1, wherein the interpolation method in S6 is linear interpolation.
3. The method for eliminating magnetic interference of a brushless DC motor according to claim 1, wherein in S7, the signal S is processed by wavelet methodICSmoothing is performed.
4. The method according to claim 1, wherein in step S5, when n of the calculated rotation speed of the brushless dc motor is less than 1000rpm, the deviation between the upper and lower thresholds of the speed interval and n is 20% to 50%; and when the calculated n of the rotating speed of the brushless direct current motor is more than or equal to 1000rpm, the deviation between the upper threshold and the lower threshold of the speed interval and the n is 5-50%.
5. The method of claim 3, wherein the method further comprises: the signal s is processed by using wavelet methodICThe smoothing is specifically performedThe method comprises the following steps:
(1) selecting the number L of layers of wavelet decomposition and the type of the decomposition wavelet;
(2) calculating a signal sICWavelet decomposition at the L-th layer;
(3) calculating a threshold value for each layer from the first layer to the lth layer;
(4) and processing the detail coefficient by applying a soft threshold method;
(5) computing a magnetic interference free signal s from threshold processing detail coefficients of the order from 1 to Lfinal。
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