Motor speed estimation method and system

Abstract

The present invention relates to a motor speed estimation method and system, and the scheme includes a motor to be tested, an acceleration sensor, an edge collector and a remote processor. The motor speed is estimated by cloud-edge collaboration: the acceleration signal collected by each sensor is integrated into a speed signal; according to the motor frequency type and speed working range sent by the server, the maximum value that meets the conditions in the frequency range on the speed signal spectrum of each sensor is taken out, which corresponds to each spectral line position; the motor speed estimated by each sensor is obtained according to each spectral line position; according to the motor speed estimated by each sensor, the speed with the most appearance or the smallest difference between any two speeds is used as the speed value of the group of collected data; the speed value estimated by multiple groups of data within a data upload time, the speed with the most appearance or the smallest difference between any two speeds is used as the final speed value of the data collected in the upload period. The scheme accurately estimates the motor speed through the vibration acceleration sensor.

Description

Technical Field

[0001] The present invention relates to a motor speed estimation method and system, and belongs to the field of mechanical equipment health monitoring and fault diagnosis. Background Art

[0002] Speed ​​is an essential parameter in the health monitoring, comprehensive evaluation, and fault diagnosis of mechanical equipment. Most mechanical equipment uses electric motors as drive devices. Motors can be categorized by frequency type as fixed-frequency motors or variable-frequency motors.

[0003] For fixed-frequency motors, the rated speed is usually used as the actual speed. However, for asynchronous motors, especially those with broken rotor bars, there is a significant difference between the actual speed and the rated speed. If the rated speed is used as the actual speed, the fault may be missed or misjudged. In addition, the actual speed is also very meaningful for calculating the load factor of the asynchronous motor and monitoring the motor load condition.

[0004] For variable-frequency motors, speed is typically read from the inverter or CNC system. However, if the systems cannot communicate, speed data cannot be obtained from the inverter or CNC system. Installing a speed sensor on-site is difficult and costly. Furthermore, the equipment site may not have the necessary conditions to install a speed sensor.

[0005] At this time, in order to realize equipment health monitoring and fault diagnosis, how to obtain or estimate the motor speed becomes an important issue. Summary of the Invention

[0006] The purpose of the present invention is to provide a motor speed estimation method and system to solve the problem of difficulty in obtaining the speed when there is a lack of conditions for installing a speed sensor on the motor equipment site and the real speed cannot be obtained from a third-party system.

[0007] To achieve the above object, the solution of the present invention includes:

[0008] A technical solution of a motor speed estimation method of the present invention includes the following steps:

[0009] 1) Collect the vibration signal of the motor to be tested and obtain the corresponding speed signal spectrum according to the vibration signal;

[0010] 2) Determine the upper and lower limits of the operating frequency on the speed signal spectrum based on the speed operating range of the motor to be tested, and select the spectrum data with a frequency between the upper and lower limits of the operating frequency and an amplitude greater than the set value as the candidate data;

[0011] 3) Determine the rotation frequency of the motor to be tested;

[0012] If the motor to be tested is a fixed-frequency motor, the frequency corresponding to the maximum value in the selected data is used as the rotational frequency of the motor to be tested;

[0013] If the motor to be tested is a variable frequency motor, determine whether there is an integer multiple relationship between the frequencies of the spectrum data in the corresponding selected data; if there is no integer multiple relationship, then the frequency corresponding to the maximum amplitude in the corresponding selected data is used as the rotational frequency of the motor to be tested; if there is an integer multiple relationship between the frequencies of two or more spectrum data, then the fundamental frequency is taken as the rotational frequency of the motor to be tested;

[0014] 4) Calculate the speed of the motor to be tested based on the rotational frequency of the motor to be tested.

[0015] The motor speed estimation method and system described in this invention utilizes vibration signals for speed estimation, reducing the need for speed sensors installed in motor equipment. For fixed-frequency asynchronous motors, speed estimation can be used to derive the motor's operating load factor and monitor whether the motor is overloaded. Furthermore, combined with the motor's pole count and rated frequency, the decibel level indicating a broken rotor bar fault can be calculated. For variable-frequency motors, speed estimation addresses the problem of equipment health monitoring and assessment systems requiring real-time speed information from the inverter or a third-party control system.

[0016] The present invention can be used as an important component of the predictive maintenance system of supporting equipment of motor manufacturing enterprises, and can also be used as a simple method for obtaining motor speed in the equipment health monitoring and evaluation system of energy, chemical, electric power, building materials, water and other industries.

[0017] Furthermore, in step 1), the vibration signal includes vibration signals at different positions of the motor to be tested; multiple speed signal spectra of the motor to be tested are obtained based on the vibration signals at different positions of the motor to be tested; in steps 2) and 3), multiple rotational frequency values ​​of the motor to be tested are obtained based on the multiple speed signal spectra of the motor to be tested;

[0018] In step 3), if two or more of the multiple frequency values ​​of the motor to be tested are equal, then the equal frequency values ​​are taken as the frequency of the motor to be tested; if the multiple frequency values ​​of the motor to be tested are different, then the average value is taken as the frequency of the motor to be tested.

[0019] Furthermore, in step 1), the vibration signal includes vibration signals at different positions of the motor to be tested; multiple speed signal spectra of the motor to be tested are obtained based on the vibration signals at different positions of the motor to be tested; in steps 2) and 3), multiple rotational frequency values ​​of the motor to be tested are obtained based on the multiple speed signal spectra of the motor to be tested;

[0020] In step 4), multiple motor speed values ​​are calculated according to the multiple frequency values ​​of the motor to be tested; if two or more speed values ​​are equal among the multiple speed values ​​of the motor to be tested, the equal speed values ​​are taken as the speed of the motor to be tested; if the speed values ​​are different among the multiple speed values ​​of the motor to be tested, the average value is taken as the speed of the motor to be tested.

[0021] Vibration data from multiple motors under test is acquired through multiple vibration measurement points. Each set of vibration data yields a frequency value, and thus a speed value. Multiple sets of data are analyzed and processed at multiple frequency values ​​or speed data points for the motor under test. Data filtering or merging are used to obtain a frequency value, which is then calculated to obtain the speed, or the speed is directly obtained. Data collected from multiple measurement points can prevent large deviations in speed estimation caused by interference from external vibration at a single measurement point. Fusion of data from multiple measurement points improves the accuracy of speed estimation.

[0022] Furthermore, in step 3), if the frequency values ​​of the motor to be tested are different, it is also determined whether the frequency values ​​are in an arithmetic progression. If not, the larger of any two frequency values ​​with the smallest absolute value of the difference is taken as the frequency of the motor to be tested.

[0023] Furthermore, in step 4), if the speed values ​​of the motor to be tested are different, it is also determined whether the speed values ​​are in an arithmetic progression. If not, the larger of any two speed values ​​with the smallest absolute value of the difference is taken as the speed of the motor to be tested.

[0024] Furthermore, considering the presence of arithmetic progressions across multiple data points, the data is merged using average values, considering that such progressions may be the result of a uniform increase or decrease in motor speed. In cases where there is no regular pattern and no two values ​​are equal, the two closest values ​​are considered equal, taking into account measurement accuracy, interference, and errors, and the larger value is used. This solution uses data processing to reduce external influences and improve estimation accuracy.

[0025] Furthermore, the vibration signal is an acceleration vibration signal collected by a vibration acceleration sensor.

[0026] The vibration state is reflected by acceleration, and the solution is mature, reliable and easy to implement.

[0027] Furthermore, the positions for collecting the acceleration vibration signal of the motor to be tested include one or more of the following: radial horizontal position, radial vertical position, and axial position of the motor drive end bearing, and radial horizontal position, radial vertical position, and axial position of the motor free end bearing.

[0028] Vibration acceleration data in multiple directions is detected at the bearings of the motor rotor main shaft. The fusion of multiple vibration data with low mutual correlation further improves the accuracy of speed estimation.

[0029] Furthermore, a method for obtaining a corresponding speed signal spectrum according to the vibration signal is: integrating the vibration signal through a collector hardware circuit, or integrating the vibration signal through an embedded software algorithm to obtain a speed signal.

[0030] Furthermore, in step 1), before collecting the vibration signal of the motor to be tested, the following steps are also included to determine whether the sensor for collecting the vibration signal is working normally and whether the motor is turned on:

[0031] If the sensor output DC voltage value is within the set range, it is judged that the corresponding sensor is working normally;

[0032] If the vibration signals output by the set number of sensors working normally are greater than the set amplitude, the motor is judged to be turned on;

[0033] If the motor is not turned on, do not execute the subsequent steps.

[0034] The data statistics method is used to simply and efficiently determine whether the sensor is faulty or not, and further determine whether the motor is running. When it is not running, the data transmission to the remote end and further processing at the remote end are stopped. It is possible to know whether the motor is working without interconnecting with the motor and its control system.

[0035] The technical solution of a motor speed estimation system of the present invention includes a sensor for collecting vibration signals of a motor to be measured, a processor connected to the sensor and obtaining the vibration signals, and the processor executes instructions to implement the motor speed estimation method described above.

[0036] The system of the present invention can provide motor speed estimation based on vibration signals for equipment health monitoring and assessment systems, providing a low-cost solution when the true speed cannot be obtained and it is inconvenient to modify and install a speed sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 1 is a schematic diagram of the principle of a motor speed estimation system according to an embodiment of the present invention;

[0038] Figure 2 FIG. 4 is a flow chart of a method for estimating motor speed according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below with reference to the accompanying drawings.

[0040] Motor speed estimation method embodiment:

[0041] The present invention provides a method for estimating the motor speed, which is suitable for Figure 1 The motor speed estimation system of the present invention is shown in FIG. 1 , and the hardware components and connection structure of the system are as follows: Figure 1 As shown, it includes: a motor to be estimated for speed, a vibration sensor for collecting vibration data of the motor to be measured, an edge collector located at the motor equipment site, and a remote server for executing a speed estimation algorithm.

[0042] Among them, the vibration sensor can be a vibration acceleration sensor, which reflects the vibration of the motor through the acceleration signal; the vibration acceleration sensor can be installed in the radial horizontal, radial vertical or axial direction of the motor drive end bearing position, as well as the radial horizontal, radial vertical or axial direction of the motor free end bearing position. Figure 1 As shown in the figure, vibration acceleration sensors are set in the radial horizontal and radial vertical directions of the bearing at the bearing positions of the motor drive end and the free end, respectively, and are marked as sensor 1, sensor 2, sensor 3, and sensor 4 respectively. The vibration signal collection position is preferably at the main shaft bearing, and the present invention does not limit the number. The vibration acceleration sensor is connected to the edge side collector through a signal cable, and the collector and the server communicate through 5G, WiFi or RJ45 wired network cable; the server can be a local area network server or a wide area network cloud server.

[0043] Those skilled in the art should understand that Figure 1 The illustrated system with both edge and remote endpoints is one example of a system suitable for the method of the present invention. Alternatively, edge acquisition and estimation can be performed, with the results uploaded to a remote server or cloud. Alternatively, the vibration acceleration sensor can be a wireless IoT sensor, with the acquisition results uploaded to a remote endpoint for signal processing and speed estimation.

[0044] The core of the method of the present invention is to estimate the speed of the motor under test by installing a vibration sensor on the motor under test at the equipment site to collect data. This can be done quickly and easily without disassembling or modifying the equipment, and the sensor can be installed without even shutting down the machine. This is particularly convenient at sites where speed sensors cannot be installed. Figure 1 A motor speed estimation system implementing the method of the present invention is provided, which can quickly complete sensor installation and modification on site and remotely monitor the motor operating status. However, the present invention does not limit the system architecture for implementing the method.

[0045] like Figure 2 As shown, the motor speed estimation method of the present invention is as follows:

[0046] (1) First, the operating status and monitoring values ​​of each vibration acceleration sensor are obtained to determine whether the sensor is working normally and whether the motor is turned on. Whether the sensor is working normally can be determined based on the DC voltage output by each sensor. If the DC voltage value is within the preset value range, the sensor is judged to be working normally. Otherwise, the sensor is judged to be working abnormally. The preset value range can be calibrated by actually operating the sensor that is working normally.

[0047] The motor start and stop judgment is performed when a set number of sensors are working normally. Whether the motor is turned on is judged based on the vibration value (amplitude of the output voltage) monitored by the normal working sensors. If the vibration value monitored by half or more of the sensors is greater than the preset value, the motor is judged to be turned on, otherwise it is judged to be stopped. The values ​​of half of the sensors and the preset vibration value can be adjusted according to the actual situation or on-site calibration, and the present invention does not limit this.

[0048] If a certain number of sensors are judged to be working abnormally, or the sensors are working normally but the motor is turned off, the speed is directly set to zero; if more than a certain number of sensors are working normally and the motor is judged to be on, the next step of speed estimation is continued.

[0049] (2) Integrating the acceleration signals collected by each vibration acceleration sensor into a velocity signal;

[0050] Integration can be achieved through the collector hardware integration circuit or embedded software integration algorithm.

[0051] (3) According to the motor frequency type and speed operating range sent by the server, the maximum value corresponding to each spectral line position that meets the conditions within the frequency range of the speed signal spectrum of each sensor is taken out;

[0052] For fixed-frequency motors, the maximum amplitude of all values ​​within the range of ±a (R+a, Ra) with the rated frequency R as the center on the speed signal spectrum of each sensor is taken. The spectral line position with an amplitude greater than b is added to the filterable motor frequency parameter pool as candidate data;

[0053] For variable frequency motors, the frequency spectrum of each sensor speed signal is taken from the interval (Rl, Rh) with the minimum operating frequency as the lower limit Rl and the maximum operating frequency Rh as the upper limit. The spectral line position with an amplitude greater than b is added to the filterable motor frequency parameter pool as the candidate data;

[0054] Here, R, a, and b are parameters that can be configured on the server or sent from the cloud. The spectral line position is the vertical and horizontal coordinates (Xi, Yi), where Xi is the frequency and Yi is the amplitude. The maximum value is taken from Yi, and the data added to the frequency conversion parameter pool is in the form of [(X1, Y1), (X2, Y2), ..., (Xi, Yi)].

[0055] (4) Determine the motor speed estimated by each sensor based on the position of each spectrum line;

[0056] For a fixed-frequency motor, the frequency corresponding to the maximum amplitude in the frequency parameter pool is directly taken as the frequency, that is, the Xi corresponding to the maximum value in Yi is taken as the frequency;

[0057] For variable frequency motors, the parameters in the frequency parameter pool are arranged in ascending order of frequency. The integer multiple relationship between each two frequencies is determined in turn. If there is no integer multiple relationship between them, the frequency corresponding to the maximum amplitude is taken as the frequency. If there is an integer multiple relationship between two or more frequencies, the fundamental frequency is taken as the frequency.

[0058] For example: For variable frequency motor, assuming X1<X2<…<Xi;

[0059] If X1, X2, ..., Xi do not have an integer multiple relationship with each other, then the Xi corresponding to the maximum value Ymax in (Y1, Y2, ..., Yi) is taken as the rotation frequency;

[0060] If x1, x2, ..., Xi are integer multiples of each other, such as X2 = 2 × X1 or Xi = n × X1, then X1 is taken as the rotation frequency;

[0061] The above-calculated rotational frequency is multiplied by 60 to obtain the motor speed estimated by each sensor.

[0062] (5) Arrange the motor speeds estimated by each sensor in ascending order. Assume that the speeds estimated by the four sensors are R1, R2, R3, and R4 respectively.

[0063] If two or more values ​​in (R1, R2, R3, R4) are equal, then the equal values ​​are taken as the speed values ​​of the set of sampling data;

[0064] If (R1, R2, R3, R4) are different and do not form an arithmetic progression, then take one of the two values ​​with the smallest absolute value of the difference as the speed value; preferably, take the larger of the two values ​​as the speed value;

[0065] For example, the set of absolute values ​​of the difference between any two speed values ​​is (|R1-R2|, |R1-R3|, |R1-R4|, |R2-R3|, |R2-R4|, |R3-R4|), and the larger of the two speed values ​​with the minimum absolute value is selected as the speed value of the set of sampling data;

[0066] If (R1, R2, R3, R4) forms an arithmetic progression, then take its average value as the speed value of this group of sampling data.

[0067] (6) Arrange multiple groups of speed values ​​within a certain data upload time in ascending order of size; assuming that the data upload cycle set by the collector is 10 seconds, and the collector collects and estimates a speed value every 2 seconds, there are 5 groups of speed values ​​within the upload cycle, which are arranged in ascending order of size as Rt1, Rt2, Rt3, Rt4, and Rt5.

[0068] If two or more values ​​among (Rt1, Rt2, Rt3, Rt4, Rt5) are equal, then the equal value is taken as the final speed value within the acquisition period;

[0069] If (Rt1, Rt2, Rt3, Rt4, Rt5) are different and do not form an arithmetic progression, then take one of the two values ​​with the smallest absolute value of the difference as the speed value; preferably, take the larger of the two values ​​as the speed value;

[0070] For example, the set of absolute values ​​of the difference between any two speed values ​​is (|Rt1-Rt2|, |Rt1-Rt3|, |Rt1-Rt4|, |Rt1-Rt5|, |Rt2-Rt3|, |Rt2-Rt4|, |Rt2-Rt5|, |Rt3-Rt4|, |Rt3-Rt5|, |Rt4-Rt5|), and the larger of the two speed values ​​with the minimum absolute value is selected as the final speed value in the acquisition period;

[0071] If (Rt1, Rt2, Rt3, Rt4, Rt5) forms an arithmetic progression, then take their average as the final speed value within the acquisition period.

[0072] At this point, the motor speed estimation method of the present invention ends.

[0073] Motor speed estimation system embodiment:

[0074] The motor speed estimation system of the present invention can implement the motor speed estimation method of the present invention in the motor speed estimation method embodiment. The motor speed estimation system and the motor speed estimation method have been clearly introduced in the motor speed estimation method embodiment and will not be repeated here.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for estimating motor speed, characterized in that: The steps include: 1) Sensors are set at the bearing positions at the motor drive end and the free end in the radial horizontal and radial vertical directions of the bearing to collect vibration signals at different positions of the motor to be tested, and multiple speed signal spectra of the motor are obtained based on the vibration signals at different positions; 2) For fixed-frequency motors, take the spectrum of the speed signal of each sensor, with the rated speed frequency as the center, and the spectrum data with the maximum value of all amplitudes within the range of ±a, and the amplitude greater than b as the candidate data; For variable frequency motors, the spectrum data of the speed signal spectrum of each sensor, with the minimum operating frequency as the lower limit and the maximum operating frequency as the upper limit, that meets the requirement that the amplitude is greater than b is selected as the candidate data; 3) Determine the rotation frequency of the motor to be tested; If the motor to be tested is a fixed-frequency motor, the frequency corresponding to the maximum value in the selected data is used as the rotational frequency of the motor to be tested; If the motor to be tested is a variable frequency motor, determine whether there is an integer multiple relationship between the frequencies of the corresponding spectrum data in the selected data; If there is no integer multiple relationship, the frequency corresponding to the maximum amplitude in the selected data is used as the rotation frequency of the motor to be tested; if there is an integer multiple relationship between the frequencies of two or more spectrum data, the fundamental frequency is taken as the rotation frequency of the motor to be tested; Obtaining multiple rotation frequency values ​​of the motor to be tested according to multiple speed signal spectra of the motor to be tested; 4) Calculating a plurality of rotational speed values ​​of the motor to be tested according to a plurality of rotational frequency values ​​of the motor to be tested; If two or more speed values ​​of the motor to be tested are equal, then the equal speed value is taken as the speed of the motor to be tested; if the multiple speed values ​​of the motor to be tested are different and do not form an arithmetic progression, Then take one of the two values ​​with the smallest absolute difference as the speed; if the multiple speed values ​​of the motor to be tested form an arithmetic progression, take their average value as the speed.

2. The motor speed estimation method according to claim 1, characterized in that: In step 4), if the speed values ​​of the motor to be tested are different and do not form an arithmetic progression, the larger of any two speed values ​​with the smallest absolute value of the difference is taken as the speed of the motor to be tested.

3. The motor speed estimation method according to claim 1, characterized in that: The vibration signal is an acceleration vibration signal collected by a sensor.

4. The motor speed estimation method according to claim 1, wherein: The method for obtaining the corresponding speed signal spectrum according to the vibration signal is: integrating the vibration signal through the collector hardware circuit, or integrating the vibration signal through the embedded software algorithm to obtain the speed signal.

5. The motor speed estimation method according to claim 1, characterized in that: In step 1), before collecting the vibration signal of the motor to be tested, the following steps are also included to determine whether the sensor for collecting the vibration signal is working normally and whether the motor is turned on: If the sensor output DC voltage value is within the set range, it is judged that the corresponding sensor is working normally; If the vibration signals output by the set number of sensors working normally are greater than the set amplitude, the motor is judged to be turned on; If the motor is not turned on, do not execute the subsequent steps.

6. A motor speed estimation system, characterized in that: The method comprises a sensor for collecting vibration signals of a motor to be measured, and a processor connected to the sensor and obtaining the vibration signals, wherein the processor executes instructions to implement the motor speed estimation method according to any one of claims 1 to 5.

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