CN114397473A - Wind speed and direction measuring method and measuring system based on ultrasonic echo signals - Google Patents
Wind speed and direction measuring method and measuring system based on ultrasonic echo signals Download PDFInfo
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- CN114397473A CN114397473A CN202111303874.0A CN202111303874A CN114397473A CN 114397473 A CN114397473 A CN 114397473A CN 202111303874 A CN202111303874 A CN 202111303874A CN 114397473 A CN114397473 A CN 114397473A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/24—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the direct influence of the streaming fluid on the properties of a detecting acoustical wave
- G01P5/245—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the direct influence of the streaming fluid on the properties of a detecting acoustical wave by measuring transit time of acoustical waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P13/00—Indicating or recording presence, absence, or direction, of movement
- G01P13/02—Indicating direction only, e.g. by weather vane
Abstract
The invention discloses a wind speed and wind direction measuring method based on ultrasonic echo signals, which comprises the following steps of: step S1: converting the excitation signal generated by the singlechip into an ultrasonic detection signal; step S2: the ultrasonic detectors in multiple directions alternately send ultrasonic detection signals and receive echo signals; step S3: calculating the actual echo time of the echo signal in the corresponding direction by adopting the echo time point based on the envelope gravity center; step S4: and calculating the component velocity of each direction according to the actual echo time of the echo signal, and calculating the resultant velocity and the wind direction by using a vector synthesis method. Compared with the existing method, the method for calculating the echo time point by enveloping the gravity center can not be influenced by signal amplitude fluctuation, and has the advantages of simple algorithm, high stability and high measurement precision.
Description
Technical Field
The invention relates to the technical field of ultrasonic waves, in particular to a wind speed and direction measuring method and a wind speed and direction measuring system based on ultrasonic echo signals.
Background
The ultrasonic wind speed measurement mainly adopts a time difference method, and the principle of the method is as follows: the propagation speed of the ultrasonic wave in the fluid changes along with the change of the flow speed of the fluid, so that due to the fact that the propagation time under the forward flow condition and the propagation time under the reverse flow condition are different, the relation between the time difference and the fluid flow speed can be established according to the forward flow and reverse flow time difference, and the instantaneous flow value is obtained.
It is important to accurately measure the echo time. For the most simple and common threshold comparison method to measure the leading edge at present, due to the existence of the comparison voltage, the method has the time error that the leading edge of the echo reaches the amplitude which is larger than the comparison voltage, and the error changes due to the amplitude of the echo, so that the error is uncertain and cannot be compensated. Further, when the echo signal is missing or trapped, the measured time lags by one or more cycles, and the error caused by the delay becomes large accordingly, and the calculated flow rate value becomes more greatly different. The currently mainstream echo time algorithms include a threshold comparison method, a level comparison method of an auxiliary threshold, a method of adaptive filter parameter estimation and a cross-correlation algorithm.
The threshold comparison method allows for setting a threshold level, and when the echo signal or its envelope is greater than the voltage, its position is taken as the echo time characteristic point. However, due to the existence of the comparison voltage, the method has a time error between the arrival of the echo front and the amplitude of the echo front being greater than the comparison voltage, and the error changes with the amplitude of the echo signal, so that the error is uncertain and cannot be compensated. Further, when a notch or an open wave occurs in an echo signal segment, the measured time lags by one cycle, and when more open waves or notches occur, the measured time lags by more cycles, the error caused by the delay increases accordingly, and the calculated flow rate value deviates more.
The level comparison method of the auxiliary threshold value considers that Hilbert transformation is carried out on an echo signal, an auxiliary threshold value level is additionally arranged under the condition that the initial part of an envelope curve and the time increase are in a linear relation, and an echo initial time point is obtained by adopting a linear fitting mode through two threshold value-time coordinates, so that the echo time is obtained. However, the method is more limited, and more auxiliary threshold levels are required to be added for envelope which is not linear or nearly linear, and a parabolic fitting mode is adopted; the final experimental result error is also in the order of 0.1ms, which is far from the accuracy requirement of 0.1us required by the present subject.
The method for estimating parameters of the adaptive filter considers that time domain delay of signals is converted into filter parameter design on a frequency domain, mean square error iteration comparison is carried out on a filtering signal obtained by an excitation signal through an adaptive filter and an echo signal, iteration is stopped after the mean square error is smaller than a threshold value, and then the delay time is reversely deduced through the filter parameters at the moment, namely the echo time under the threshold value error. The method can achieve high precision theoretically, but when the wave defect and the trapped wave occur in the first two oscillation periods, the error of the method can reach more than 5%, and the precision is far from enough, so the method needs to be improved.
And performing cross-correlation convolution processing on the template echo signal and the real sampling echo signal by a cross-correlation algorithm, and performing envelope detection on the processed waveform to obtain the time corresponding to the maximum amplitude point, namely the echo time. The method has the advantages that the method theoretically has the precision reaching the minimum error of ADC sampling, can reach 0.1us magnitude and even lower, and has strong noise immunity, and the result is not greatly influenced by wave shortage and notch; however, the method uses the template, the template sampling is required to be carried out again on each probe, and the convolution algorithm is used, so that the resource occupation is high, the calculation amount is large, and the simplification needs to be considered.
Therefore, the echo time algorithms of the above-mentioned several mainstream methods have the problems of large calculation amount, complex hardware structure, and easy interference of noise to the measurement accuracy.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a wind speed and direction measuring method and a wind speed and direction measuring system based on ultrasonic echo signals, and aims to solve the problems that the conventional echo time algorithm in the prior art is large in calculated amount, complex in hardware structure and easy to interfere with the measurement precision by noise.
The invention is realized by adopting the following technical scheme:
a wind speed and wind direction measuring method based on ultrasonic echo signals comprises the following steps:
step S1: converting the excitation signal generated by the singlechip into an ultrasonic detection signal;
step S2: the ultrasonic detectors in multiple directions alternately send ultrasonic detection signals and receive echo signals;
step S3: calculating the actual echo time of the echo signal in the corresponding direction by adopting the echo time point based on the envelope gravity center;
step S4: and calculating the component velocity of each direction according to the actual echo time of the echo signal, and calculating the resultant velocity and the wind direction by using a vector synthesis method.
In order to optimize the technical scheme, the specific measures adopted further comprise:
further, in step S2, the plurality of ultrasonic probes are arranged at intervals in a direction at ninety degrees to each other.
Further, the specific process of calculating the actual echo time of the corresponding direction echo signal by using the echo time point based on the envelope gravity center in step S3 is as follows:
s31: calculating a correlation characteristic value of the echo signal, and fitting by adopting a linear fitting method to obtain a waveform envelope;
s32: calculating the gravity center of the waveform envelope;
s33: acquiring the sending time of an ultrasonic detection signal and the time point of receiving the envelope gravity center of an echo, and calculating the actual echo time;
s34: and (4) optimizing the actual echo time by combining channel delay, and calculating the theoretical echo time.
Further, the step S31 is to calculate a correlation eigenvalue of the echo signal waveform, and obtain a waveform envelope by fitting using a linear fitting method, which specifically includes:
s311: calculating a waveform average value, and translating the waveform average value upwards by four to six data points;
s312: acquiring rising zero-crossing points and falling zero-crossing points according to the waveform average value and by combining waveform characteristics;
s313: calculating the coordinates of peak points according to the middle points of the rising zero-crossing points and the falling zero-crossing points;
s314: and fitting by adopting a linear fitting method according to the coordinates of the rising zero-crossing point, the falling zero-crossing point and the peak point to obtain the waveform envelope.
Further, the step S34 optimizes the actual echo time by combining the channel delay, and calculates the theoretical echo time, which specifically includes:
s341: calibrating channel delay according to the zero wind speed condition;
s342: and removing the channel delay of the corresponding direction from the actual echo time of each direction, and calculating to obtain the theoretical echo time.
Further, the specific process of calculating the barycenter of the waveform envelope in step S32 is as follows: establishing an upper envelope function of the echo signal, calculating the envelope gravity center according to the upper envelope function,
wherein: f (x) represents the upper envelope function, xcRepresenting the envelope center of gravity and x the coordinates of the point in time.
Further, the step S4 calculates the component velocity of each direction according to the echo time of the echo signal, and calculates the resultant velocity and the wind direction by using a vector synthesis method, which specifically includes:
s41: establishing two-dimensional coordinate systems about an X axis and a Y axis, respectively calculating the component speeds in the X axis direction and the Y axis direction,
wherein: t is tRWIndicates the time, t, at which the ultrasonic detector A receives the echo of the ultrasonic detection signal on the X-axisReIndicating the time, t, at which the ultrasonic detector B receives the echo of the ultrasonic detection signal on the X-axisRnIndicating the ultrasonic detector C receives the ultrasonic detection signal echo on the X axisTime of (t)RsThe time of the ultrasonic detector D receiving the ultrasonic detection signal echo on the X axis is shown, L shows the path length of the ultrasonic detection signal, u shows the wind speed of the ultrasonic detection signal, and theta shows the emission angle of the ultrasonic detection signal;
s42: the component velocities of the X axis and the Y axis are used for calculating the resultant velocity and the wind direction angle by a vector synthesis method,
wherein: u represents the resultant velocity, and α represents the wind direction angle.
An anemometry system based on ultrasonic echo signals, comprising:
the power supply module is used for providing stable current;
the voltage conversion module is used for converting and boosting the current to high voltage;
the control module is used for controlling the high-voltage pulse module to generate an excitation signal and calculating the wind speed and the wind direction according to the ultrasonic echo signal;
the ultrasonic transduction module is used for generating and sending an ultrasonic signal according to the excitation signal and receiving an ultrasonic echo signal;
the signal processing module is used for amplifying and filtering the ultrasonic echo signal;
the digital-to-analog conversion module is used for performing analog-to-digital conversion on the ultrasonic echo signal and then sending the ultrasonic echo signal to the control module;
and the intelligent terminal is used for collecting, storing and calculating the wind speed and the wind direction.
The invention has the beneficial effects that:
compared with the existing method, the method for calculating the echo time point by enveloping the gravity center can not be influenced by signal amplitude fluctuation, and has the advantages of simple algorithm, high stability and high measurement precision. A wind speed and direction measuring system based on ultrasonic echo signals has the advantages of being low in implementation cost and simple in hardware structure.
Drawings
Fig. 1 is a schematic view of the working process of the present invention.
FIG. 2 is a flowchart illustrating the operation of step 3 of FIG. 1 according to the present invention.
FIG. 3 is a schematic block diagram of a wind speed and direction measuring system based on ultrasonic echo signals according to the present invention.
Detailed Description
In order to clarify the technical solution and the working principle of the present invention, the present invention is further described in detail with reference to the following embodiments in conjunction with the accompanying drawings, it should be noted that, in the premise of not conflicting, any combination between the embodiments described below or between the technical features may form a new embodiment.
1-2, a method for measuring wind speed and wind direction based on ultrasonic echo signals, the method comprises the following steps:
step S1: converting the excitation signal generated by the singlechip into an ultrasonic detection signal;
step S2: the ultrasonic detectors in multiple directions alternately send ultrasonic detection signals and receive echo signals;
specifically, in the process of measuring the wind speed and the wind direction by using the ultrasonic signals, because the wind speed and the wind direction change in multiple directions and multiple angles, multiple ultrasonic detectors need to be arranged in multiple directions, echo signals of multiple angles are acquired by adopting an alternate emission mode, and the processing and analysis of the echo signals in subsequent steps are facilitated.
Wherein: the four ultrasonic detectors are arranged at ninety degree intervals from each other in four directions.
Step S3: calculating the actual echo time of the echo signal in the corresponding direction by adopting the echo time point based on the envelope gravity center;
specifically, the echo time point of the envelope center of gravity is not changed by the amplitude fluctuation of the echo signal, and the detection accuracy is high.
S31: calculating a correlation characteristic value of the echo signal, and fitting by adopting a linear fitting method to obtain a waveform envelope, wherein the correlation characteristic value comprises a waveform average value, a rising zero-crossing point, a falling zero-crossing point and a peak point;
s311: calculating a waveform average value, and translating the waveform average value upwards by four to six data points;
s312: acquiring rising zero-crossing points and falling zero-crossing points according to the waveform average value and by combining waveform characteristics;
s313: calculating the coordinates of peak points according to the middle points of the rising zero-crossing points and the falling zero-crossing points;
s314: fitting by adopting a linear fitting method according to the coordinates of the rising zero crossing point, the falling zero crossing point and the peak point to obtain a waveform envelope;
s32: calculating the gravity center of the waveform envelope;
specifically, an upper envelope function of the echo signal is established, an envelope center of gravity is calculated from the upper envelope function,
wherein: f (x) represents the upper envelope function, xcRepresenting the envelope center of gravity and x the coordinates of the point in time.
S33: acquiring the sending time of an ultrasonic detection signal and the time point of receiving the envelope gravity center of an echo, and calculating the actual echo time;
s34: and (4) optimizing the actual echo time by combining channel delay, and calculating the theoretical echo time.
S341: calibrating channel delay according to the zero wind speed condition;
s342: and removing the channel delay of the corresponding direction from the actual echo time of each direction, and calculating to obtain the theoretical echo time.
Step S4: calculating the component speed of each direction according to the actual echo time of the echo signal, and calculating the resultant speed and the wind direction by using a vector synthesis method;
specifically, the present invention is applied to a semiconductor device.
S41: establishing two-dimensional coordinate systems about an X axis and a Y axis, respectively calculating the component speeds in the X axis direction and the Y axis direction,
wherein: t is tRWIndicates the time, t, at which the ultrasonic detector A receives the echo of the ultrasonic detection signal on the X-axisReIndicating the time, t, at which the ultrasonic detector B receives the echo of the ultrasonic detection signal on the X-axisRnIndicating the time, t, at which the ultrasonic detector C receives the echo of the ultrasonic detection signal on the X-axisRsThe time of the ultrasonic detector D receiving the ultrasonic detection signal echo on the X axis is shown, L represents the path length of the ultrasonic detection signal, u represents the wind speed of the ultrasonic detection signal, and theta represents the emission angle of the ultrasonic detection signal;
s42: the component velocities of the X axis and the Y axis are used for calculating the resultant velocity and the wind direction angle by a vector synthesis method,
wherein: u represents the resultant velocity, and α represents the wind direction angle.
Detailed description of the invention
A wind speed and direction measuring system based on ultrasonic echo signals comprises a power supply module, a wind speed and direction measuring module and a wind direction measuring module, wherein the power supply module is used for supplying stable current; the voltage conversion module is used for converting and boosting the current to high voltage; the control module is used for controlling the high-voltage pulse module to generate an excitation signal and calculating the wind speed and the wind direction according to the ultrasonic echo signal; the ultrasonic transduction module is used for generating and sending an ultrasonic signal according to the excitation signal and receiving an ultrasonic echo signal; the signal processing module is used for amplifying and filtering the ultrasonic echo signal; the digital-to-analog conversion module is used for performing analog-to-digital conversion on the ultrasonic echo signal and then sending the ultrasonic echo signal to the control module; and the intelligent terminal is used for collecting the wind speed and wind direction data calculated and stored by the control module.
The power module adopts a stabilized voltage power supply, the control module adopts an STM32 series single chip microcomputer, the ultrasonic transduction module adopts an ultrasonic transducer, the transmitting end of the ultrasonic transducer is electrically connected with the high-voltage pulse module and used for generating ultrasonic signals, the receiving end of the ultrasonic transducer is electrically connected with the signal processing module and used for receiving echo signals, the digital-to-analog conversion module adopts an analog-to-digital (A/D) conversion module, the intelligent terminal adopts a computer, and the intelligent terminal and the control module are in serial port communication connection.
It should be understood that this embodiment is a system example corresponding to the first embodiment, and may be implemented in cooperation with the first embodiment. The related technical details mentioned in the first embodiment are still valid in this embodiment, and are not described herein again in order to reduce repetition. Accordingly, the related-art details mentioned in the present embodiment can also be applied to the first embodiment.
It should be noted that each module referred to in this embodiment is a logical module, and in practical applications, one logical unit may be one physical unit, may be a part of one physical unit, and may be implemented by a combination of multiple physical units. In addition, in order to highlight the innovative part of the present invention, elements that are not so closely related to solving the technical problems proposed by the present invention are not introduced in the present embodiment, but this does not indicate that other elements are not present in the present embodiment.
The foregoing is merely an example of the present invention, and common general knowledge in the field of known specific structures and characteristics is not described herein in any greater extent than that known in the art at the filing date or prior to the priority date of the application, so that those skilled in the art can now appreciate that all of the above-described techniques in this field and have the ability to apply routine experimentation before this date can be combined with one or more of the present teachings to complete and implement the present invention, and that certain typical known structures or known methods do not pose any impediments to the implementation of the present invention by those skilled in the art. It should be noted that, for those skilled in the art, without departing from the structure of the present invention, several changes and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.
Claims (8)
1. A wind speed and wind direction measuring method based on ultrasonic echo signals is characterized by comprising the following steps: comprises the following steps;
step S1: converting the excitation signal generated by the singlechip into an ultrasonic detection signal;
step S2: the ultrasonic detectors in multiple directions alternately send ultrasonic detection signals and receive echo signals;
step S3: calculating the actual echo time of the echo signal in the corresponding direction by adopting the echo time point based on the envelope gravity center;
step S4: and calculating the component velocity of each direction according to the actual echo time of the echo signal, and calculating the resultant velocity and the wind direction by using a vector synthesis method.
2. The wind speed and wind direction measuring method based on the ultrasonic echo signal according to claim 1, characterized in that: in step S2, the plurality of ultrasonic probes are arranged at ninety degree intervals in the direction of each other.
3. The method for measuring wind speed and wind direction based on ultrasonic echo signals according to claim 2, wherein the specific process of calculating the actual echo time of the corresponding direction echo signal by using the echo time point based on the envelope gravity center in step S3 is as follows:
s31: calculating a correlation characteristic value of the echo signal, and fitting by adopting a linear fitting method to obtain a waveform envelope;
s32: calculating the gravity center of the waveform envelope;
s33: acquiring the sending time of an ultrasonic detection signal and the time point of receiving the envelope gravity center of an echo, and calculating the actual echo time;
s34: and (4) optimizing the actual echo time by combining channel delay, and calculating the theoretical echo time.
4. The method according to claim 3, wherein the step S31 of calculating the correlation eigenvalue of the echo signal waveform and fitting the waveform envelope by a linear fitting method includes:
s311: calculating a waveform average value, and translating the waveform average value upwards by four to six data points;
s312: acquiring rising zero-crossing points and falling zero-crossing points according to the waveform average value and by combining waveform characteristics;
s313: calculating the coordinates of peak points according to the middle points of the rising zero-crossing points and the falling zero-crossing points;
s314: and fitting by adopting a linear fitting method according to the coordinates of the rising zero-crossing point, the falling zero-crossing point and the peak point to obtain the waveform envelope.
5. The method for measuring wind speed and wind direction based on ultrasonic echo signals according to claim 4, wherein the step S34 is to optimize the actual echo time in combination with the channel delay, and calculate the theoretical echo time, and specifically includes:
s341: calibrating channel delay according to the zero wind speed condition;
s342: and removing the channel delay of the corresponding direction from the actual echo time of each direction, and calculating to obtain the theoretical echo time.
6. The method for measuring wind speed and wind direction based on ultrasonic echo signals according to claim 5, wherein the concrete process of calculating the gravity center of the waveform envelope in the step S32 is as follows: establishing an upper envelope function of the echo signal, calculating the envelope gravity center according to the upper envelope function,
wherein: f (x) represents the upper envelope function, xcRepresenting the envelope center of gravity and x the coordinates of the point in time.
7. The method according to claim 5, wherein the step S4 is to calculate the component velocity of each direction according to the echo time of the echo signal, and calculate the resultant velocity and the wind direction by using a vector synthesis method, and specifically includes:
s41; establishing two-dimensional coordinate systems about an X axis and a Y axis, respectively calculating the component speeds in the X axis direction and the Y axis direction,
wherein: t is tRWIndicates the time, t, at which the ultrasonic detector A receives the echo of the ultrasonic detection signal on the X-axisReIndicating the time, t, at which the ultrasonic detector B receives the echo of the ultrasonic detection signal on the X-axisRnIndicating the time, t, at which the ultrasonic detector C receives the echo of the ultrasonic detection signal on the X-axisRsThe time of the ultrasonic detector D receiving the ultrasonic detection signal echo on the X axis is shown, L shows the path length of the ultrasonic detection signal, u shows the wind speed of the ultrasonic detection signal, and theta shows the emission angle of the ultrasonic detection signal;
s42: the component velocities of the X axis and the Y axis are used for calculating the resultant velocity and the wind direction angle by a vector synthesis method,
wherein: u represents the resultant velocity, and α represents the wind direction angle.
8. A wind speed and wind direction measuring system based on ultrasonic echo signals is characterized in that: comprises that
The power supply module is used for providing stable current;
the voltage conversion module is used for converting and boosting the current to high voltage;
the control module is used for controlling the high-voltage pulse module to generate an excitation signal and calculating the wind speed and the wind direction according to the ultrasonic echo signal;
the ultrasonic transduction module is used for generating and sending an ultrasonic signal according to the excitation signal and receiving an ultrasonic echo signal;
the signal processing module is used for amplifying and filtering the ultrasonic echo signal;
the digital-to-analog conversion module is used for performing analog-to-digital conversion on the ultrasonic echo signal and then sending the ultrasonic echo signal to the control module;
and the intelligent terminal is used for collecting, storing and calculating the wind speed and the wind direction.
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