Method for calculating mechanical speed of electric rotating machine

Abstract

The invention relates to a method (100) for calculating a mechanical speed of an electric rotating machine (400). The method (100) comprises: calculating (101) a spectrum from signals measured by at least one vibration sensor (403) attached to the rotating machine (400); extracting (103) a mechanical velocity component from the calculated spectrum; a mechanical speed of the rotating machine (400) is calculated (105) as a function of a mechanical speed component, where the mechanical speed component is extracted as a function of a frequency component greater than a given threshold (303).

Description

Technical Field

[0001] The invention disclosed herein relates to a method for calculating the mechanical speed of an electric rotating machine and to an electric rotating machine according to the accompanying claims. Background Art

[0002] Vibration monitoring is a known condition monitoring technique for rotating machines. It is based on accelerometers or piezoelectric sensors mounted on the machine.

[0003] Advanced monitoring methods often deploy spectrum analysis to detect and diagnose one type of fault. For example, a misalignment of a motor shaft results in a characteristic peak in the flow chart of radial motion on the rotational sequence of a rotating machine.

[0004] For fault classification, the actual speed of the rotating machine rotor needs to be known to identify relevant peaks, since different faults (i.e., unbalance, eccentricity, etc.) will result in different measured fault modes. However, the frequency of the fault mode is usually related to the rotational speed.

[0005] Furthermore, it is known to use rotor position estimation techniques in frequency converters to control the speed of the motor. In order to estimate the speed of the motor, electrical signals such as current and voltage are fed to a mathematical motor model, which outputs an estimated position of the rotor. The parameters of the mathematical motor model are usually measured during commissioning. Therefore, a problem arises in that the parameters of the mathematical model may be inaccurate and they may change over time during operation, for example due to changes in temperature wear of the motor, faults in the windings and / or changes in the motor load, which leads to inaccurate results, i.e. an inaccurate estimate of the motor speed.

[0006] In this context, there is a need to accurately calculate the motor speed of an electric rotating machine. Summary of the invention

[0007] Thus, according to a first aspect of the present invention, a method for calculating the mechanical speed of an electric rotating machine is disclosed.

[0008] The method according to the present invention comprises: accelerating the motor speed, calculating the frequency spectrum of a signal measured by at least one vibration sensor attached to the rotating machine, extracting a mechanical speed component from the calculated frequency spectrum, and calculating the mechanical speed of the rotating machine as a function of the mechanical speed component, wherein the mechanical speed component is extracted as a function of a frequency component greater than a given threshold.

[0009] In the context of the present invention, the mechanical speed component is to be understood as a mathematical expression relative to the speed variation of the rotor of the electric rotating machine. In particular, the mechanical speed component may be a mathematical expression describing the level of imbalance, misalignment or eccentricity, which exists in practically every application, even if it is not considered a fault but normal. The mathematical expression may be based on or contain peaks in the spectral pattern relative to the rotational speed of the electric motor.

[0010] By using the mechanical speed component, the speed of the rotating machine can be calculated very accurately. In addition, the mechanical speed component can change over time according to the changing characteristics of the rotating machine. Therefore, by periodically calculating the speed of the rotating machine using the mechanical speed component, the changing characteristics of the rotating machine are included in the calculation of the speed of the rotating machine, thereby generating very accurate information about the state, i.e., the rotational speed of the rotating machine. Therefore, the parameters of the mathematical motor model of the rotating machine measured during the commissioning of the rotating machine can be updated so as to generate an accurate mathematical motor model representing the current state of the rotating machine.

[0011] By extracting the mechanical speed component as a function of the frequency components greater than a given threshold, only significant vibrations are used as indicators of the speed of the rotating machine. Thus, the influence of background noise unrelated to the speed of the rotating machine on the calculated mechanical speed is minimized.

[0012] To calculate the mechanical speed of the rotating machine as a function of the mechanical speed component, the value of the extracted mechanical speed component may be used as the mechanical speed, or the value may be mathematically converted to a rotational speed or angular speed, or eg a corresponding exponential value.

[0013] According to an embodiment, the threshold value is a multiple, in particular three times, of the average value of the plurality of frequencies of the spectrum.

[0014] By dynamically calculating the threshold for extracting the mechanical velocity component from the spectrum, i.e. based on multiple frequencies of the spectrum, in particular each frequency of the spectrum, it is possible to avoid the situation where the threshold is too high or too low. In particular, it has been found that a threshold of three times the average value of all frequencies of the spectrum is sufficient to identify a representative mechanical velocity component.

[0015] According to another embodiment, the threshold value is a multiple, in particular three times, of the standard deviation of the frequencies of the spectrum.

[0016] By taking into account the standard deviation of the threshold calculation, the impact of extreme values ​​on the threshold is minimized, making the threshold representative of the overall performance of the rotating machine.

[0017] According to another embodiment, the mechanical velocity component is extracted as a function of a number of frequencies greater than a given threshold.

[0018] By considering multiple frequencies for calculating the mechanical speed, the mechanical speed can be calculated very accurately using multiple mechanical origins, such as multiple deformations at multiple points on a rotating machine.

[0019] According to another embodiment, the method further comprises estimating a rotor position of a rotor of the rotating machine as a function of at least one electrical parameter measured during operation of the rotating machine, determining an estimated motor speed based on the estimated rotor position, and minimizing a difference between the machine speed and the estimated motor speed by adjusting a control parameter of the rotating machine.

[0020] According to another embodiment, the difference between the machine speed and the estimated motor speed is minimized by adjusting a control parameter of the rotating machine so that the estimated motor speed approaches the calculated machine speed.

[0021] To control the rotating machine based on the calculated machine speed, a control parameter may be adjusted based on a difference between the calculated machine speed and an estimated motor speed used in a control loop for controlling the rotating machine.

[0022] Therefore, the accelerometer signal can be used to adjust the motor model parameters during operation.

[0023] The adjustment can be based on a spectrum analysis algorithm that provides accurate motor model parameters adapted to any operating condition. In one aspect of the algorithm, the spectrum analysis of the accelerometer signal is a node for extracting an accurate measurement of the mechanical speed of the rotating machine. In another aspect, the estimated rotor position is used to derive the estimated rotor speed. Then, the difference between the calculated motor speed and the estimated rotor speed is calculated. Based on the difference, the motor parameters are adjusted in a way that minimizes the difference.

[0024] According to another embodiment, the mechanical speed is fed into a mathematical motor model of the rotating machine for use in controlling the rotating machine.

[0025] By feeding the mechanical speed into the mathematical motor model, the mathematical motor model will automatically adjust itself to control the rotating machine based on the calculated mechanical speed and is therefore very accurate.

[0026] According to another embodiment, multiple frequency spectra from multiple signals measured by multiple vibration sensors attached at different locations of the rotating machine are used and the machine speed is calculated as a function of the machine speed component having the maximum value and / or the minimum variance.

[0027] By using multiple vibration sensors, the best point for measuring a signal representing the speed of the rotating machine can be found.

[0028] According to another embodiment, the calculated machine speed is sent as a redundant speed feedback signal to the safety function.

[0029] By using the redundant signal, an estimated failure of the main signal can be identified. In addition, by using the mechanical speed for controlling the rotating machine instead of the main signal, the rotating machine can be further operated in the event of a failure for estimating the main signal.

[0030] According to another embodiment, a fault message is output in case the difference between the calculated mechanical speed and the speed calculated based on the signals measured by the encoder and / or the resolver is larger than a tolerance threshold.

[0031] By using the calculated machine speed as a reference, a faulty speed signal can be easily identified. Therefore, in the event that a faulty speed signal is identified, the sensor underlying the faulty speed signal must also be faulty.

[0032] According to a second aspect, the invention relates to an electric rotating machine. The rotating machine comprises a rotor, a plurality of vibration sensors and a processor, wherein the processor is configured to perform an embodiment of the method disclosed herein.

[0033] According to an embodiment, a plurality of vibration sensors are part of a monitoring system.

[0034] By using a vibration sensor as part of a monitoring system as a vibration sensor for calculating machine speed, the vibration sensor has a dual function. Thus, in the case of a rotating machine equipped with a vibration sensor-based monitoring system, no additional sensors are required to perform the method disclosed herein.

[0035] According to another embodiment, the plurality of vibration sensors includes at least one acceleration sensor.

[0036] In particular, acceleration sensors have been found to be suitable for identifying speed-dependent signals which are generated, for example, due to certain vibrations of a gearbox or a belt.

[0037] According to another embodiment, the electric rotating machine does not include an encoder and / or a resolver.

[0038] By using the method or machine disclosed herein, the speed of the machine can be calculated very accurately. Therefore, no additional sensors, such as encoders and / or resolvers, are required.

[0039] The effects and further embodiments of the estimation of the method for estimating the mechanical speed of an electric rotating machine according to the invention are similar to those according to the above description. Therefore, reference may be made to the above description. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Further features, details and advantages of the invention emerge from the wording of the claims and from the following description of exemplary embodiments based on the drawings. The drawings show:

[0041] Figure 1 is an embodiment of the method disclosed herein,

[0042] Figure 2 is a schematic overview of an algorithm based on the method disclosed herein,

[0043] Figure 3 is a schematic overview of the principles of the methods disclosed herein,

[0044] Figure 4 is an embodiment of the electric rotating machine disclosed herein. DETAILED DESCRIPTION

[0045] exist Figure 1 , a method 100 for calculating the mechanical speed of an electric rotating machine is shown.

[0046] The method 100 comprises a first calculation step 101. In the first calculation step 101, a frequency spectrum is calculated from a signal measured by at least one vibration sensor attached to a rotating machine.

[0047] Furthermore, the method 100 comprises an extraction step 103. In the extraction step 103, a mechanical velocity component is extracted from the calculated frequency spectrum, wherein the mechanical velocity component is extracted as a function of frequencies greater than a given threshold.

[0048] Furthermore, the method 100 comprises a second calculation step 105. In the second calculation step 105, the mechanical speed of the rotating machine is calculated as a function of the mechanical speed component.

[0049] exist Figure 2 In FIG. 2 , an algorithm 200 is shown. The algorithm 200 is based on motor signals 201 , such as current and / or voltage, initial motor model parameters 203 and acceleration signals 205 measured by an acceleration sensor attached to the rotating machine as input signals.

[0050] Based on the motor signal 201 , a rotor position estimation 207 is performed using the motor model parameters 203 .

[0051] Based on the acceleration signal 205, using Figure 1 The method 100 performs spectrum analysis 209. For example, the mechanical speed calculated in the spectrum analysis 209 is mathematically related to the rotor position estimated in the rotor position estimation 207 by converting the estimated rotor position to the estimated rotor speed, and by further subtracting the estimated rotor speed from the calculated mechanical speed, or vice versa.

[0052] The results of the spectrum analysis 209 are used for online motor parameter adaptation 211 of the mathematical motor model. Thus, the rotor position estimation 207 can be performed a second time using accurate motor model parameters.

[0053] exist Figure 3 , a graph 300 is shown having frequency on its x-axis and acceleration index on its y-axis.

[0054] The parameter 301 is calculated from the signal measured by the acceleration sensor attached to the rotating machine. At position P1 , a large value 307 can be seen, which is greater than the threshold 303 and therefore represents a mechanical velocity component.

[0055] Since the mechanical speed component is related to the actual speed of the rotating machine, the mechanical speed of the rotating machine may be calculated based on the value of the mechanical speed component.

[0056] Once the mechanical speed is calculated, it can be mathematically related to an estimated speed value 305 calculated based on the estimated position of the rotor of the rotating machine. The result of the mathematical relationship, which can be a division or subtraction, is used in a feedback loop for parameter adjustments in a mathematical motor model used to control the motor of the rotating machine.

[0057] exist Figure 4 In FIG. 4 , an electric rotating machine 400 is shown. The rotating machine 400 includes a rotor 401 , a plurality of vibration sensors 403 , and a processor 405 .

[0058] The processor 405 is configured to execute Figure 1 Method 100.

[0059] The present invention is not limited to one of the above-described embodiments. It can be modified in many ways.

[0060] All features and advantages arising from the claims, the description and the drawings, including construction details, spatial arrangements and procedural steps, may be essential to the study itself and in various combinations.

[0061] Reference numerals list

[0062] 100 Methods

[0063] 101 First Calculation Step

[0064] 103 Extraction steps

[0065] 105 Second calculation step

[0066] 200 Algorithms

[0067] 201 Motor signal

[0068] 203 Motor model parameters

[0069] 205 Acceleration signal

[0070] 207 Rotor Position Estimation

[0071] 209 Spectrum Analysis

[0072] 211 Motor parameter adaptation

[0073] 300 Graph

[0074] 301 Parameters

[0075] 303 Threshold

[0076] 400 Rotating Machines

[0077] 401 Rotor

[0078] 403 Vibration Sensor

[0079] 405 processor.

Claims

1. A method (100) for calculating a mechanical speed of an electric rotating machine (400), the method (100) comprising: - calculating (101) a frequency spectrum from a signal measured by at least one vibration sensor (403) attached to the rotating machine (400), - extracting (103) the mechanical velocity component from the calculated spectrum, - calculating (105) the mechanical speed of the rotating machine (400) as a function of the mechanical speed component, The mechanical velocity component is extracted as a function of a frequency component greater than a given threshold (303).

2. The method (100) according to claim 1, characterized in that: The threshold (303) is a multiple, in particular three times, of an average value of a plurality of frequencies of the spectrum.

3. The method (100) according to claim 1, characterized in that: The threshold (303) is a multiple, in particular three, of the standard deviation of the frequencies of the spectrum.

4. The method (100) according to any one of the preceding claims, characterized in that The mechanical velocity component is extracted as a function of a plurality of frequencies greater than the threshold (303).

5. The method (100) according to any one of the preceding claims, characterized in that The method (100) further comprises: - estimating (207) a rotor position of a rotor (401) of the rotating machine (400) as a function of at least one electrical parameter measured during operation of the rotating machine (400), - determining an estimated motor speed based on the estimated rotor position, - minimizing the difference between the machine speed and the estimated motor speed by adjusting control parameters of the rotating machine (400).

6. The method (100) according to claim 5, characterized in that: The difference between the machine speed and the estimated motor speed is minimized by adjusting control parameters of the rotary machine (400) so that the estimated motor speed approaches the calculated machine speed.

7. The method (100) according to claim 5 or 6, characterized in that: The mechanical speed is fed to a mathematical motor model of the rotating machine (400) for use in controlling the rotating machine (400).

8. The method (100) according to any one of the preceding claims, characterized in that A plurality of frequency spectra from a plurality of signals measured by a plurality of vibration sensors (403) attached at different locations of the rotating machine (400) are used, and the mechanical speed is calculated as a function of the mechanical speed component having a maximum value and / or a minimum variance.

9. The method (100) according to any one of the preceding claims, characterized in that The calculated mechanical speed is sent to the safety function as a redundant speed feedback signal.

10. The method (100) according to any one of the preceding claims, characterized in that In case the difference between the calculated mechanical speed and the speed calculated based on the signals measured by the encoder and / or the resolver is greater than a tolerance threshold, a fault message is output.

11. An electric rotating machine (400), the rotating machine (400) comprising: - a rotor (401), - a plurality of vibration sensors (403), - a processor (405), The processor (405) is configured to execute the method (100) according to any one of claims 1 to 9.

12. The electric rotating machine (400) according to claim 11, characterized in that The plurality of vibration sensors (403) are part of a monitoring system.

13. The electric rotating machine (400) according to claim 11, characterized in that The plurality of vibration sensors (403) include at least one acceleration sensor.

14. The electric rotating machine (400) according to claim 11, characterized in that The electric rotating machine (400) does not include an encoder and / or a resolver.

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