CN111220816A

CN111220816A - Time difference type ultrasonic flow velocity measuring method adopting frequency hopping signal

Info

Publication number: CN111220816A
Application number: CN202010061886.6A
Authority: CN
Inventors: 晏生剑; 杨忠涛; 刘天华
Original assignee: Haisheng Technology Co Ltd Of China Shipbuilding Industry Corp
Current assignee: Haisheng Technology Co Ltd Of China Shipbuilding Industry Corp
Priority date: 2020-01-19
Filing date: 2020-01-19
Publication date: 2020-06-02
Anticipated expiration: 2040-01-19
Also published as: CN111220816B

Abstract

The invention discloses a time-difference ultrasonic flow velocity measurement method using a frequency hopping signal. The second transducer receives the ultrasonic signal emitted by the first transducer, detects the demarcation point of different signal segments, that is, the frequency hopping point, and determines the receiving time of the ultrasonic signal according to the time of the frequency hopping point and the duration of each signal segment; The transducer receives the ultrasonic signal emitted by the second transducer, detects the demarcation point of different signal segments, that is, the frequency hopping point, and determines the receiving time of the ultrasonic signal according to the time of the frequency hopping point and the duration of each signal segment; compares the receiving time of the ultrasonic signal time, calculate the time difference; using the time difference method, according to the time difference, calculate the flow rate of the fluid. The method of the invention has high measurement accuracy, high flow velocity measurement stability, strong anti-interference ability and good environmental adaptability.

Description

Time difference type ultrasonic flow velocity measuring method adopting frequency hopping signal

Technical Field

The invention belongs to the field of fluid flow velocity measurement, and particularly relates to a time difference type ultrasonic flow velocity measurement method adopting frequency hopping signals.

Background

The time difference method for measuring the average flow velocity of the end face of a river (channel) channel measures the difference between the forward flow propagation time and the reverse flow propagation time of an acoustic signal by utilizing the characteristic that the propagation velocities are different due to different flow directions of fluid when an acoustic wave propagates in the fluid, so as to calculate the flow velocity of the fluid, and the principle is shown in figure 1.

The existing ultrasonic current meter mainly uses a single-frequency pulse signal amplitude detection method to measure the sound wave propagation time, and the detection method is shown in fig. 2. The receiving circuits at two ends of the river (channel) channel detect the amplitude of the received single-frequency pulse signal, compare the detected amplitude with a threshold value, the time when the detected amplitude is higher than the threshold value is the signal receiving time, and the time difference between the detected amplitude and the signal transmitting time is the sound wave propagation time. The accuracy of the sound wave propagation time measurement is greatly influenced by the amplitude consistency of 2-path received signals, the requirements on the parameter consistency of the transducer and the equipment matching and debugging are high, the production efficiency is reduced, and the production cost is increased. The underwater acoustic signal amplitude is greatly influenced by factors such as water surface, underwater reflection, foreign matter shielding and the like, the requirement on the equipment installation environment is high, the installation difficulty is increased, and the environmental adaptability of the equipment is reduced.

Disclosure of Invention

The invention aims to solve the problems, and provides a time difference type ultrasonic flow velocity measurement method adopting frequency hopping signals, wherein the ultrasonic signals used for measurement comprise a plurality of signal sections, different signal sections have different signal frequencies, and the dividing points of the signal sections are frequency hopping points.

The technical scheme of the invention is that a time difference type ultrasonic flow velocity measuring method of frequency hopping signals is adopted, a first transducer and a second transducer are arranged on two side walls of a fluid channel at intervals, a connecting line of the first transducer and the second transducer forms a certain included angle with the flow direction of fluid, the first transducer and the second transducer transmit the same 2-path ultrasonic signals in turn and receive the ultrasonic signals transmitted by the opposite side to determine the receiving time difference of the 2-path ultrasonic signals, the measuring method comprises the following steps,

step 1: the first transducer and the second transducer transmit ultrasonic signals comprising a plurality of signal segments in turn, and different signal segments have different signal frequencies;

step 2: the second transducer receives the ultrasonic signals transmitted by the first transducer, detects boundary points, namely frequency hopping points, of different signal segments, and determines the receiving time of the ultrasonic signals according to the time of the frequency hopping points and the duration of each signal segment;

and step 3: the first transducer receives the ultrasonic signals transmitted by the second transducer, detects boundary points, namely frequency hopping points, of different signal segments, and determines the receiving time of the ultrasonic signals according to the time of the frequency hopping points and the duration of each signal segment;

and 4, step 4: comparing the receiving time of the ultrasonic signals in the step 2 and the step 3, and calculating the time difference;

and 5: and (4) calculating the flow rate of the fluid according to the time difference in the step (4) by adopting a time difference method.

Further, in step 2 or step 3, before the boundary point of the different signal segments is detected, the received ultrasonic signal is subjected to smoothing filtering.

Further, the ultrasonic signal is a sine wave signal.

Further, in step 2 or step 3, the boundary points of different signal segments are detected, all peak points and valley points of the ultrasonic signal are searched, each sine wave signal period is calculated through the peak points or the valley points, and the boundary points, namely frequency hopping points, of different signal segments are determined according to the signal periods.

Preferably, the different signal segments contain the same number of signal cycles.

Preferably, the frequencies of the different signal segments of the ultrasonic signal are 204kHz, 210kHz, 205kHz, 209kHz, 206kHz, 208kHz, 207kHz in this order.

Compared with the prior art, the invention has the beneficial effects that:

1) the method has the advantages of high measurement precision, good real-time performance, high flow velocity measurement stability, strong anti-interference capability and good environmental adaptability;

2) the frequency hopping points are easy to detect, and compared with an amplitude comparison method, the requirements on transducer parameter consistency and equipment matching and debugging are low, the production efficiency is improved, and the production cost is reduced;

3) the ultrasonic signal comprises a plurality of signal segments and frequency hopping points, each frequency hopping point can be used as a receiving time reference point for determining the ultrasonic receiving time, and even if the received ultrasonic signal is partially distorted, the accurate measurement of the propagation time difference cannot be influenced.

Drawings

The invention is further illustrated by the following figures and examples.

FIG. 1 is a schematic diagram of a method for measuring transit time ultrasonic flow velocity;

FIG. 2 is a schematic diagram of single frequency pulse signal amplitude detection;

FIG. 3 is a waveform diagram of a first ultrasonic signal according to an embodiment;

FIG. 4 is a waveform diagram of a second ultrasonic signal according to the embodiment;

in the figure, T1 is a first signal segment signal period, T2 is a second signal segment signal period, T3 is a third signal segment signal period, Td1 is a signal duration from a first frequency hopping point to a receiving time, Td2 is a signal duration from a second frequency hopping point to the receiving time, and T₁₀Is the receiving time t of the first ultrasonic signal₁₁The time t of the first frequency hopping point of the first path of ultrasonic signal₁₂The time t of the second frequency hopping point of the first path of ultrasonic signal₂₀Is the receiving time t of the second path of ultrasonic signal₂₁Is the time of the first frequency hopping point of the second path of ultrasonic signals, t₂₂The time of the second frequency hopping point of the second path of ultrasonic signals.

Detailed Description

As shown in figure 1, the time difference type ultrasonic flow velocity measurement method adopting frequency hopping signals comprises the following steps of arranging a first transducer and a second transducer at intervals on two sides of a river channel, forming a certain included angle between a connecting line of the first transducer and the second transducer and the flow direction of river water, transmitting the same 2 paths of sinusoidal ultrasonic signals by the first transducer and the second transducer in turn, receiving ultrasonic signals transmitted by the opposite side, and determining the receiving time difference of the 2 paths of ultrasonic signals,

step 1: the ultrasonic wave signal generator comprises a first transducer, a second transducer, a first signal acquisition module, a second signal acquisition module and a signal processing module, wherein the first transducer and the second transducer transmit ultrasonic wave signals comprising 7 signal sections in turn, and different signal sections have different signal frequencies;

step 2: the second transducer receives the first path of ultrasonic signals transmitted by the first transducer, performs smooth filtering, detects boundary points, namely frequency hopping points, of different signal segments, and determines the receiving time of the ultrasonic signals according to the time of the frequency hopping points and the duration of each signal segment, as shown in fig. 3;

step 2.1: receiving an ultrasonic signal transmitted by a first transducer, and performing smooth filtering;

step 2.2: searching all peak points and valley points of the received ultrasonic signals, calculating each sine wave signal period through the peak points or the valley points, and determining boundary points, namely frequency hopping points, of different signal segments according to the signal periods;

step 2.3: one of the frequency hopping points is selected, if the first frequency hopping point is used as a reference point of the receiving time, the receiving time t of the first path of ultrasonic signal is calculated₁₀，t₁₀＝t₁₁-Td1；

And step 3: the first transducer receives the second path of ultrasonic signals transmitted by the second transducer, performs smooth filtering, detects boundary points, namely frequency hopping points, of different signal segments, and determines the receiving time of the ultrasonic signals according to the time of the frequency hopping points and the duration of each signal segment, as shown in fig. 4;

step 3.1: receiving a second path of ultrasonic signals transmitted by a second transducer, and performing smooth filtering;

step 3.2: searching all peak points and valley points of the received ultrasonic signals, calculating each sine wave signal period through the peak points or the valley points, and determining boundary points, namely frequency hopping points, of different signal segments according to the signal periods;

step 3.3: one of the frequency hopping points is selected, if the second frequency hopping point is used as a reference point of the receiving time, the receiving time t of the second path of ultrasonic signal is calculated₂₀，t₂₀＝t₂₁-Td2；

And 4, step 4: comparing the reception times of the ultrasonic signals in step 2 and step 3, calculating a time difference Δ t ═ t₂₀-t₁₀；

And 5: and (4) calculating the flow velocity of the river water by adopting a time difference method according to the time difference delta t in the step (4).

The frequencies of the 7 signal segments of the ultrasonic signal are 204kHz, 210kHz, 205kHz, 209kHz, 206kHz, 208kHz and 207kHz in sequence.

As shown in fig. 1, the time difference method depends on the time difference at which the transducers receive ultrasonic signals simultaneously transmitted by the opposite transducers,

Δt＝t₂-t₁(1)

V_p＝V cosα (4)

wherein L is the distance between the first transducer and the second transducer, C is the sound velocity in the fluid, V is the fluid flow velocity, α is the installation angle of the transducers relative to the fluid channel, V is the installation angle of the transducers relative to the fluid channel_pThe velocity component of the fluid flow velocity in the direction of the transducer, t₁Is the propagation time, t, of the ultrasonic signal from transducer A to transducer B₂Is the travel time of the ultrasonic signal from transducer B to transducer A;

by combining the formulas (1), (2), (3) and (4), the product can be obtained

Since the fluid flow velocity is much less than the sound velocity in the fluid, i.e. V < C, it can be obtained from the formula (5)

After transformation, can obtain

In step 5, the flow rate of the water flow can be calculated by using the formula (6).

The specific details of the time difference method refer to the international standard ISO6416-1992, ultrasonic (sound) wave method for flow measurement.

In the embodiment, frequency hopping points of the received sinusoidal ultrasonic signals, such as a first frequency hopping point and a second frequency hopping point, are easy to detect, and compared with an amplitude comparison method, the requirements on transducer parameter consistency and equipment matching and debugging are low, so that the production efficiency is improved, and the production cost is reduced; a plurality of frequency hopping points of the ultrasonic signals can be used as reference points of receiving time and used for determining the ultrasonic receiving time, effective data samples are added, and whether distortion or interruption occurs in the signal transmission process due to interference factors can be judged by comparing the plurality of frequency hopping points.

Claims

1. The time difference ultrasonic flow velocity measurement method of frequency hopping signal is adopted, and the first transducer and the second transducer are arranged at intervals on both side walls of the fluid channel, and the connecting lines of the first transducer and the second transducer and The flow direction of the fluid forms an included angle, the first transducer and the second transducer transmit the same two ultrasonic signals in turn, and receive the ultrasonic signals transmitted by the other party to determine the receiving time difference of the two ultrasonic signals, which is characterized in that including the following steps,

Step 1: The first transducer and the second transducer alternately transmit ultrasonic signals including multiple signal segments, and different signal segments have different signal frequencies;

Step 2: the second transducer receives the ultrasonic signal transmitted by the first transducer, detects the boundary point of different signal segments, that is, the frequency hopping point, and determines the receiving time of the ultrasonic signal according to the time of the frequency hopping point and the duration of each signal segment;

Step 3: the first transducer receives the ultrasonic signal transmitted by the second transducer, detects the boundary point of different signal segments, that is, the frequency hopping point, and determines the receiving time of the ultrasonic signal according to the time of the frequency hopping point and the duration of each signal segment;

Step 4: compare the receiving moments of the ultrasonic signals in Step 2 and Step 3, and calculate the time difference;

Step 5: Using the time difference method, according to the time difference in step 4, calculate the flow rate of the fluid.

2. The time-difference ultrasonic flow velocity measurement method using frequency hopping signal according to claim 1, is characterized in that, in step 2 or step 3, before the described detection of the demarcation point of different signal segments, the received ultrasonic signal is smoothed filter.

3 . The time-difference ultrasonic flow velocity measurement method using a frequency hopping signal according to claim 2 , wherein the ultrasonic signal is a sine wave signal. 4 .

4. the time difference ultrasonic flow velocity measurement method of adopting frequency hopping signal according to claim 3, is characterized in that, in step 2 or step 3, described detecting the demarcation point of different signal sections, searching for all peak points of ultrasonic signal, The trough point, calculates each sine wave signal cycle through the peak point or the trough point, and determines the demarcation point of different signal segments according to the signal cycle, that is, the frequency hopping point.

5 . The time-difference ultrasonic flow velocity measurement method using a frequency hopping signal according to claim 1 , wherein different signal segments contain the same number of signal periods. 6 .

6. the time-difference ultrasonic flow velocity measurement method using frequency hopping signal according to any one of claims 1-5, is characterized in that, the frequency of different signal segments of ultrasonic signal is successively 204kHz, 210kHz, 205kHz, 209kHz, 206kHz, 208kHz, 207kHz.