阅读说明：本技术 用于测量液压泵转速的方法和系统 (Method and system for measuring the rotational speed of a hydraulic pump ) 是由 周密愉 孔洁 朱良杰 顾星 于 2021-09-07 设计创作，主要内容包括：本发明公开了一种用于测量液压泵转速的方法,包括：通过声音采集装置采集液压泵转动时的声音以获得声音信号；对该声音信号进行时频分析以获得该声音信号的频率；基于该声音信号的频率来确定该液压泵的转速。(The invention discloses a method for measuring the rotating speed of a hydraulic pump, which comprises the following steps: collecting the sound generated by the rotation of the hydraulic pump through a sound collecting device to obtain a sound signal; performing time-frequency analysis on the sound signal to obtain the frequency of the sound signal; the rotational speed of the hydraulic pump is determined based on the frequency of the sound signal.)

1. A method for measuring a rotational speed of a hydraulic pump, comprising:

collecting the sound generated by the rotation of the hydraulic pump through a sound collecting device to obtain a sound signal;

performing time-frequency analysis on the sound signal to obtain the frequency of the sound signal;

determining a rotational speed of the hydraulic pump based on a frequency of the sound signal.

2. The method of claim 1, wherein collecting the sound of the hydraulic pump while rotating by the sound collection device further comprises:

and collecting the sound generated when the hydraulic pump rotates by the sound collection device at a position within a range of 0.5m to 5m from the hydraulic pump.

3. The method of claim 1, wherein the sound collection device has an initial sampling rate, and further comprising:

determining from the acquired sound signal whether the initial sampling rate meets a threshold, wherein meeting the threshold represents being above a lower sampling rate limit and below an upper sampling rate limit;

downsampling the sound signal at a first sampling rate that meets the threshold if it is determined that the initial sampling rate is above the upper sampling rate limit; and

if it is determined that the initial sampling rate is below the lower sampling rate limit, prompting to re-sample the sound while the hydraulic pump is rotating at a second sampling rate that meets the threshold or to up-sample the sound signal at a third sampling rate that meets the threshold.

4. The method of claim 1, wherein performing a time-frequency analysis on the sound signal comprises: and carrying out short-time Fourier transform on the sound signal.

5. The method of claim 1, further comprising: and before the time-frequency analysis is carried out on the sound signal, carrying out noise reduction processing on the sound signal.

6. The method of claim 1, wherein determining the rotational speed of the hydraulic pump based on the frequency of the sound signal further comprises determining the rotational speed of the hydraulic pump based on:

n＝60f/p

wherein n is the rotation speed of the hydraulic pump, f is the frequency of the sound signal, and p is the number of pole pairs of the driving motor of the hydraulic pump.

7. A system for measuring a rotational speed of a hydraulic pump, comprising:

a sound collection unit configured to collect sound when the hydraulic pump rotates to obtain a sound signal;

a signal analysis unit configured to perform a time-frequency analysis on the sound signal to obtain a frequency of the sound signal;

a rotational speed determination unit configured to determine a rotational speed of the hydraulic pump based on a frequency of the sound signal.

8. The system of claim 7, wherein the sound collection unit is further configured to: collecting sound when the hydraulic pump rotates at a position within a range of 0.5m to 5m from the hydraulic pump.

9. The system of claim 7, wherein the sound collection unit has an initial sampling rate, and further comprising a sampling rate adjustment unit configured to: determining from the acquired sound signal whether the initial sampling rate meets a threshold, wherein meeting the threshold represents being above a lower sampling rate limit and below an upper sampling rate limit; downsampling the sound signal at a first sampling rate that meets the threshold if it is determined that the initial sampling rate is above the upper sampling rate limit; and prompting to reacquire the sound while the hydraulic pump is rotating at a second sampling rate that meets the threshold or to upsample the sound signal at a third sampling rate that meets the threshold if it is determined that the initial sampling rate is below the lower sampling rate limit.

10. The system of claim 7, wherein performing a time-frequency analysis on the sound signal comprises: and carrying out short-time Fourier transform on the sound signal.

11. The system of claim 7, further comprising a noise reduction unit configured to: and before the time-frequency analysis is carried out on the sound signal, carrying out noise reduction processing on the sound signal.

12. The system of claim 7, wherein the rotational speed determination unit is further configured to determine the rotational speed of the hydraulic pump based on:

n＝60f/p

wherein n is the rotation speed of the hydraulic pump, f is the frequency of the sound signal, and p is the number of pole pairs of the driving motor of the hydraulic pump.

13. A computer-readable storage medium storing a computer program executable by a processor to perform the method of any one of claims 1-6.

Technical Field

The present invention relates to hydraulic systems, and more particularly to a method and system for measuring the rotational speed of a hydraulic pump.

Background

In the process of hydraulic system test and data analysis, the change of the rotating speed of the hydraulic pump is required to be known frequently. The rotation speed measurement of the hydraulic pump usually adopts the form of additionally installing a rotation speed sensor. The rotation speed sensor can be roughly classified into several types, such as a laser type, a magneto-electric type, a capacitor type, a variable reluctance type, and the like, according to its operating principle. However, some hydraulic pumps are not suitable for installing a rotation speed sensor due to the narrow installation space and special structure thereof. According to the prior art, the rotational speed of such hydraulic pumps cannot be measured.

In response to the deficiencies of the prior art methods of measuring the rotational speed of a hydraulic pump, it is desirable to provide an improved method and system for measuring the rotational speed of a hydraulic pump.

Disclosure of Invention

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

The invention provides a method for measuring the rotating speed of a hydraulic pump, which comprises the following steps: collecting the sound generated by the rotation of the hydraulic pump through a sound collecting device to obtain a sound signal; performing time-frequency analysis on the sound signal to obtain the frequency of the sound signal; the rotational speed of the hydraulic pump is determined based on the frequency of the sound signal.

In some embodiments, collecting the sound of the hydraulic pump while rotating by the sound collection device further comprises: the sound when the hydraulic pump is rotated is collected by the sound collection device at a position within a range of 0.5m to 5m from the hydraulic pump.

In some embodiments, the sound collection device has an initial sampling rate, and the method further comprises: determining whether the initial sampling rate meets a threshold value according to the acquired sound signals, wherein the threshold value is met and represents that the initial sampling rate is higher than a lower sampling rate limit and lower than an upper sampling rate limit; downsampling the sound signal at a first sampling rate that meets a threshold if it is determined that the initial sampling rate is above the upper sampling rate limit; and prompting to reacquire the sound while the hydraulic pump is rotating at a second sampling rate that meets a threshold or to upsample the sound signal at a third sampling rate that meets the threshold if it is determined that the initial sampling rate is below the lower sampling rate limit.

In some embodiments, performing the time-frequency analysis on the sound signal comprises: a short-time fourier transform is performed on the sound signal.

In some embodiments, the method further comprises: before time-frequency analysis is carried out on the sound signal, noise reduction processing is carried out on the sound signal.

In some embodiments, determining the rotational speed of the hydraulic pump based on the frequency of the acoustic signal further comprises determining the rotational speed of the hydraulic pump based on:

n＝60f/p

wherein n is the rotation speed of the hydraulic pump, f is the frequency of the sound signal, and p is the number of pole pairs of the driving motor of the hydraulic pump.

The present invention also provides a system for measuring the rotational speed of a hydraulic pump, comprising: a sound collection unit configured to collect sound when the hydraulic pump rotates to obtain a sound signal; a signal analysis unit configured to perform time-frequency analysis on the sound signal to obtain a frequency of the sound signal; a rotational speed determination unit configured to determine a rotational speed of the hydraulic pump based on a frequency of the sound signal.

In some embodiments, the sound collection unit is further configured to: the sound when the hydraulic pump is rotated is collected at a position within a range of 0.5 to 5m from the hydraulic pump.

In some embodiments, the sound collection unit has an initial sampling rate, and the system further comprises a sampling rate adjustment unit configured to: determining whether the initial sampling rate meets a threshold value according to the acquired sound signals, wherein the threshold value is met and represents that the initial sampling rate is higher than a lower sampling rate limit and lower than an upper sampling rate limit; downsampling the sound signal at a first sampling rate that meets a threshold if it is determined that the initial sampling rate is above the upper sampling rate limit; and prompting to reacquire the sound while the hydraulic pump is rotating at a second sampling rate that meets a threshold or to upsample the sound signal at a third sampling rate that meets the threshold if it is determined that the initial sampling rate is below the lower sampling rate limit.

In some embodiments, performing the time-frequency analysis on the sound signal comprises: a short-time fourier transform is performed on the sound signal.

In some embodiments, the system further comprises a noise reduction unit configured to: before time-frequency analysis is carried out on the sound signals, noise reduction processing is carried out on the sound signals.

In some embodiments, the rotational speed determination unit is further configured to determine the rotational speed of the hydraulic pump based on:

n＝60f/p

wherein n is the rotation speed of the hydraulic pump, f is the frequency of the sound signal, and p is the number of pole pairs of the driving motor of the hydraulic pump.

The present invention also provides a computer-readable storage medium storing a computer program executable by a processor to perform the aforementioned method for measuring a rotational speed of a hydraulic pump.

The method for measuring the rotating speed of the hydraulic pump does not need to be additionally provided with a rotating speed sensor, and the rotating speed of the hydraulic pump is obtained through collection and analysis of sound when the hydraulic pump works. The method is not limited by the installation space of the hydraulic pump and the structure of the equipment, does not need to disassemble and assemble the hydraulic pump and peripheral pipelines, and can conveniently, quickly, economically and practically realize the measurement of the rotating speed of the hydraulic pump practically and accurately.

Drawings

The features, nature, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings. In the drawings, like reference numerals are used to designate corresponding parts throughout the several views. It is noted that the drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes.

Fig. 1 shows a flow chart of a method according to the invention for measuring the rotational speed of a hydraulic pump.

Fig. 2 shows a block diagram of the system for measuring the rotational speed of a hydraulic pump of the present invention.

Fig. 3 shows a block diagram of an apparatus including the system for measuring the rotational speed of a hydraulic pump of the present invention.

Fig. 4 shows a schematic diagram of a frequency-time curve obtained using the method of the invention in the case of a smooth running hydraulic pump.

Fig. 5 shows a schematic diagram of a frequency-time curve obtained using the method of the invention in the case of a non-steady running hydraulic pump.

Fig. 6A and 6B illustrate exemplary test results for measuring the rotational speed of a hydraulic pump using the method of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with specific embodiments. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the described exemplary embodiments. It will be apparent, however, to one skilled in the art, that the described embodiments may be practiced without some or all of these specific details. In other exemplary embodiments, well-known structures have not been described in detail to avoid unnecessarily obscuring the concepts of the present disclosure. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Meanwhile, the various aspects described in the embodiments may be arbitrarily combined without conflict.

The conventional method for measuring the rotating speed of the hydraulic pump usually needs to be additionally provided with a rotating speed sensor and is easily limited by the installation space of the hydraulic pump and the structure of equipment.

According to the method for measuring the rotating speed of the hydraulic pump, the frequency and the rotating speed are obtained through calculation and analysis of the working sound of the hydraulic pump, a rotating speed sensor does not need to be additionally arranged, and the problem of measuring the rotating speed of the hydraulic pump, which cannot be additionally provided with the rotating speed sensor due to the limitation of the installation space and the structure of equipment, is solved.

Fig. 1 shows a flow chart of a method 100 for measuring the rotational speed of a hydraulic pump according to the invention. Where the steps in the dashed box may be optional.

The method 100 begins at 102, where at 102, sound is collected as the hydraulic pump rotates by a sound collection device to obtain a sound signal. For example, the sound collection may be performed by a device such as a mobile phone, a computer, or a recording pen having a recording function.

The sound collection of the hydraulic pump should be carried out as close as possible to the hydraulic pump and as far as possible to avoid environmental noise. In some embodiments, sound collection may be performed by a sound collection device at a position in a range of 0.5m to 5m from the hydraulic pump. Preferably, the sound collection may be performed at a position about 1m from the hydraulic pump.

At 104, it is determined whether the initial sampling rate of the sound collection device meets a threshold, wherein meeting the threshold represents being above a lower sampling rate limit and below an upper sampling rate limit. If the initial sampling rate meets the threshold ("yes" at 104), the method 100 proceeds to step 114. If the initial sampling rate does not meet the threshold, it is determined whether the initial sampling rate is above an upper sampling rate limit or below a lower sampling rate limit. If it is determined that the initial sampling rate is above the upper sampling rate limit ("yes" at 106), the sound signal is downsampled at a first sampling rate that meets a threshold (108). If it is determined that the initial sampling rate is below the lower sampling rate limit ("yes" at 110), then the sound signal is prompted to be resampled at a second sampling rate that meets the threshold or to be upsampled at a third sampling rate that meets the threshold (112). In various embodiments, the first, second, and third sampling rates may be the same or different.

For example, in the actual rotation speed measurement process, if the initial sampling rate of the sound collection device is too high, too many data points are collected, which brings a large computational burden to the subsequent analysis and processing. If the sampling rate is too low, too few data points are collected, thereby reducing the accuracy and reliability of subsequent analysis and processing. To this end, the upper and lower sampling rate limits may be set based on the performance of the subsequent analysis and processing equipment. If the initial sampling rate is higher than the upper sampling rate limit, the subsequent devices will not have sufficient performance to analyze and process the acquired sound signals. When the initial sampling rate is higher than the upper sampling rate limit, the sound signal may be downsampled (downsampled at a sampling rate lower than the upper sampling rate limit and higher than the lower sampling rate limit). If the initial sampling rate is below the lower sampling rate limit, the user may be prompted to re-acquire the acoustic signal of the hydraulic pump at a sampling rate that is above the lower sampling rate limit (and below the upper sampling rate limit). For a sound collection device with a plurality of sampling rates, the sampling rate satisfying the above sampling rate condition can be selected from the sampling rates for sound collection. If the highest sampling rate of the sound collection device is lower than the lower limit of the sampling rate, another sound collection device meeting the above sampling rate condition can be used for sound collection again. In the alternative, if the initial sampling rate is below the lower sampling rate limit, the sampling rate may also be increased by upsampling the sound signal (e.g., by interpolation) to be above the lower sampling rate limit and below the upper sampling rate limit. It should be noted that if the initial sampling rate is too low, the captured sound may not represent a detailed portion of the original sound. In this case, although the sampling rate may be increased by processing (e.g., upsampling) the sound, it does not contribute to the details. Therefore, in the case that the initial sampling rate is lower than the lower limit of the sampling rate, if it is desired to embody the details of the original sound as much as possible, it is preferable to adopt a scheme of re-collecting the sound signal.

Subsequently, at 114, the sound signal is subjected to noise reduction processing. For example, the sound signal may be subjected to noise reduction processing by a filter to filter out background noise.

At 116, a time-frequency analysis is performed on the sound signal to obtain a frequency of the sound signal.

In some embodiments, a short-time fourier transform may be performed on the sound signal to obtain a time-frequency spectrum (frequency-time curve) of the sound signal, and the frequencies of the sound signal at various times are obtained based on the time-frequency spectrum. The mathematical definition of the short-time fourier transform is as follows:

where s (t) is the sound signal and γ (t) is a window function (e.g., a square window function, a triangular window function, a gaussian function, etc.).

At 118, a rotational speed of the hydraulic pump is determined based on the frequency of the acoustic signal. Specifically, the rotational speed of the hydraulic pump may be determined by:

n＝60f/p

wherein n is the rotation speed of the hydraulic pump, f is the frequency of the sound signal, and p is the number of pole pairs of the driving motor of the hydraulic pump.

FIG. 2 shows a block diagram of a system 200 for measuring the rotational speed of a hydraulic pump of the present invention.

As shown in fig. 2, the system 200 may include a sound collection unit 202, a signal analysis unit 204, a rotational speed determination unit 206, a sampling rate adjustment unit 208, and a noise reduction unit 210. Each of these units may be connected to or communicate with each other, directly or indirectly, over one or more buses 212.

In various embodiments of the present invention, the sound collection unit 202 may be configured to collect sound when the hydraulic pump is rotating to obtain a sound signal. In some embodiments, the sound collection unit 202 may be further configured to collect sounds when the hydraulic pump rotates at a position within a range of 0.5m to 5m from the hydraulic pump.

The signal analysis unit 204 may be configured to perform a time-frequency analysis on the sound signal to obtain a frequency of the sound signal. In some embodiments, performing a time-frequency analysis on the sound signal includes performing a short-time fourier transform on the sound signal.

The rotational speed determination unit 206 may be configured to determine the rotational speed of the hydraulic pump based on the frequency of the sound signal. In some embodiments, the rotational speed determination unit 206 may be further configured to determine the rotational speed of the hydraulic pump based on the following equation:

n＝60f/p

wherein n is the rotation speed of the hydraulic pump, f is the frequency of the sound signal, and p is the number of pole pairs of the driving motor of the hydraulic pump.

In some embodiments, the sound collection unit 202 has an initial sampling rate, and the sampling rate adjustment unit 208 may be configured to: determining whether the initial sampling rate meets a threshold value according to the acquired sound signals, wherein the threshold value is met and represents that the initial sampling rate is higher than a lower sampling rate limit and lower than an upper sampling rate limit; downsampling the sound signal at a first sampling rate that meets a threshold if it is determined that the initial sampling rate is above the upper sampling rate limit; and prompting to reacquire the sound while the hydraulic pump is rotating at a second sampling rate that meets a threshold or to upsample the sound signal at a third sampling rate that meets the threshold if it is determined that the initial sampling rate is below the lower sampling rate limit.

The noise reduction unit 210 may be configured to: before time-frequency analysis is carried out on the sound signals, noise reduction processing is carried out on the sound signals. For example, the sound signal may be subjected to noise reduction processing by a filter to filter out background noise.

While specific elements of system 200 are shown in FIG. 2, it should be understood that these elements are exemplary only and not limiting. In different implementations, one or more of the units may be combined, divided, removed, or additional units may be added. For example, in some implementations, the sound collection unit 202 and the sample rate adjustment unit 208 may be combined into a single unit. In some implementations, the system 200 may include an output unit (not shown) to output the determined hydraulic pump rotational speed (e.g., to a display device).

Fig. 3 shows a block diagram of an apparatus 300 comprising the system for measuring the rotational speed of a hydraulic pump of the present invention.

The apparatus illustrates a general hardware environment in which the present invention may be applied in accordance with an exemplary embodiment of the present invention.

A device 300 will now be described with reference to fig. 3, which is an exemplary embodiment of a hardware device that may be applied to aspects of the present invention. Device 300 may be any machine configured to perform processing and/or computing, and may be, but is not limited to, a workstation, a server, a desktop computer, a laptop computer, a tablet computer, a Personal Digital Assistant (PDA), a smartphone, or any combination thereof. The above-described system may be implemented in whole or at least in part by device 300 or a similar device or system.

Device 300 may include components that may be connected to bus 312 or in communication with bus 312 via one or more interfaces. For example, device 300 may include, among other things, a bus 312, a processor 302, a memory 304, an input device 308, and an output device 310.

The processor 302 may be any type of processor and may include, but is not limited to, a general purpose processor and/or a special purpose processor (e.g., a special purpose processing chip), an intelligent hardware device (e.g., a general purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some cases, the processor 302 may be configured to operate a memory array using a memory controller. In other cases, a memory controller (not shown) may be integrated into the processor 302. The processor 302 may be responsible for managing the bus and general processing, including the execution of software stored on memory. The processor 302 may also be configured to perform various functions described herein related to measuring hydraulic pump rotational speed. For example, the processor 302 may be configured to: collecting the sound generated by the rotation of the hydraulic pump through a sound collecting device to obtain a sound signal; performing time-frequency analysis on the sound signal to obtain the frequency of the sound signal; and determining a rotational speed of the hydraulic pump based on the frequency of the sound signal.

Memory 304 may be any storage device that may enable storage of data. The memory 304 may include, but is not limited to, a magnetic disk drive, an optical storage device, a solid-state memory, a floppy disk, a hard disk, a magnetic tape or any other magnetic medium, an optical disk or any other optical medium, a ROM (read only memory), a RAM (random access memory), a cache memory and/or any other memory chip or cartridge, and/or any other medium from which a computer can read data, instructions and/or code. The memory 304 may store computer-executable software 306 comprising computer-readable instructions that, when executed, cause the processor to perform various functions described herein in connection with measuring hydraulic pump rotational speed.

Input device 308 may be any type of device that may be used to input information.

Output device 310 may be any type of device for outputting information. In one scenario, output device 310 may be any type of output device that can display information.

Fig. 4 shows a schematic diagram of a frequency-time curve 400 obtained using the method of the invention in the case of a smooth operation of the hydraulic pump.

In the example of fig. 4, a sound collection device (e.g., a mobile phone having a recording function) collects a sound signal for a period of 80 seconds(s) in the vicinity of the hydraulic pump (e.g., a position about 1m from the hydraulic pump), and the period covers various operation stages of starting, steady operation, and stopping of the hydraulic pump.

After a short time fourier transformation of the sound signal, a frequency-time curve 400 as shown in fig. 4 can be obtained. As shown in the graph 400, the frequency of the sound signal is gradually increased from zero over a period of about 0-35s, which corresponds to the start-up phase of the hydraulic pump. The frequency of the acoustic signal is substantially constant (substantially stabilized at 350Hz) during a period of about 35-45s, which corresponds to a stable operation phase of the hydraulic pump. The frequency of the acoustic signal is gradually reduced to zero during a period of about 45-80s, which corresponds to the stop phase of the hydraulic pump.

Based on the frequency-time curve 400, the frequency of the sound signal at each time can be found. It can be seen from the plot 400 that in the case of a smooth operation of the hydraulic pump (e.g., no failure of the hydraulic pump), the frequency-time curve is also relatively smooth without large fluctuations.

Although fig. 4 shows that the sound signal is collected for a period of 80s, and covers various working stages of starting, steady operation and stopping of the hydraulic pump. However, in different embodiments, sound signals of different durations may be acquired and different working phases of the hydraulic pump may be covered (e.g. only steady running phases of the hydraulic pump). Furthermore, although only a short-time Fourier transform of the sound signal is shown in FIG. 4, other time-frequency analysis methods, such as wavelet transforms, Wigner-Ville distributions, generalized S-transforms, and the like, may be employed in different implementations.

Fig. 5 shows a schematic diagram of a frequency-time curve 500 obtained using the method of the invention in the case of a non-steady running hydraulic pump.

In the example of fig. 5, a sound collection device (e.g., a mobile phone with a recording function) collects a sound signal for a duration of 2.7 minutes (min) (about 162 seconds) in the vicinity of (e.g., about 1m from) the hydraulic pump. Meanwhile, the rotation speed of the hydraulic pump fluctuates during the sound collection process (e.g., the hydraulic pump malfunctions, the rotation speed of the hydraulic pump varies due to human actions, etc.).

Based on the frequency-time curve 500, the frequency of the sound signal at each time can be found. It can be seen from the curve 500 that in the case of a non-steady operation of the hydraulic pump, the frequency-time curve fluctuates considerably.

In some embodiments, the determination of whether the hydraulic pump is malfunctioning may be made by fluctuations in the frequency-time curve. For example, if it is detected based on the frequency-time curve that the fluctuation of the frequency of the sound signal within a certain period of time (e.g., 5 seconds, 10 seconds, etc.) is less than a preset threshold (e.g., 15Hz, 20Hz, etc.), it may be determined that the hydraulic pump is not malfunctioning. Otherwise, if it is detected that the frequency of the sound signal fluctuates more than a preset threshold value within the period of time, it may be judged that the hydraulic pump is out of order. At this time, a prompt message may be given to remind the user to check the operating condition of the hydraulic pump.

Fig. 6A and 6B illustrate exemplary test results for measuring the rotational speed of a hydraulic pump using the method of the present invention.

In the test, the operating speed of the hydraulic pump was set to 2345rpm (i.e., the actual speed).

With the hydraulic pump rotational speed measuring method of the present invention, a sound signal having a duration of about 2.7min (about 162s) is collected in the vicinity of the hydraulic pump (e.g., at a position about 1m from the hydraulic pump) with a sound collecting device (e.g., a mobile phone having a sound recording function).

After a short time fourier transform of the sound signal, a frequency-time curve 600 as shown in fig. 6A can be obtained. Based on the frequency-time curve 600, the frequency of the sound signal at each time can be found. For example, it can be seen from the curve 600 that the frequency measured at time 2.133min is 351.6 Hz.

After obtaining the frequency-time curve 600, a rotation speed-time curve (a curve shown by a dotted line in fig. 6B) as shown in fig. 6B may be obtained by a frequency-rotation speed conversion formula. The frequency-rotation speed conversion formula is as follows:

n＝60f/p

wherein n is the rotation speed of the hydraulic pump, f is the frequency of the sound signal, and p is the number of pole pairs of the driving motor of the hydraulic pump.

Based on the speed-time curve, the real-time speed of the hydraulic pump at each time can be obtained. As shown, using the method of the present invention, the hydraulic pump speed measured at time 2.133min was 2345.5051 rpm.

For comparison, the hydraulic pump rotational speed measured using the rotational speed sensor is also shown in fig. 6B (the curve shown by the solid line in fig. 6B). The sampling rate of the adopted rotating speed sensor is 10Hz, and the uncertainty of the sensor is less than or equal to 1 percent. In the test, the stable rotation speed of the hydraulic pump measured by the rotation speed sensor was 2344.9274 rpm. Therefore, the method for measuring the rotating speed of the hydraulic pump can accurately measure the rotating speed of the hydraulic pump without additionally arranging an additional rotating speed sensor.

The detailed description set forth above in connection with the appended drawings describes examples and is not intended to represent all examples that may be implemented or fall within the scope of the claims. The terms "example" and "exemplary" when used in this specification mean "serving as an example, instance, or illustration," and do not mean "superior or superior to other examples.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, usage of such phrases may not refer to only one embodiment. Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean "one and only one" unless specifically so stated, but rather "one or more. The term "some" means one or more unless specifically stated otherwise. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims.

It is also noted that the embodiments may be described as a process which is depicted as a flowchart, a flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be rearranged.

While various embodiments have been illustrated and described, it is to be understood that the embodiments are not limited to the precise configuration and components described above. Various modifications, substitutions, and improvements apparent to those skilled in the art may be made in the arrangement, operation, and details of the devices disclosed herein without departing from the scope of the claims.