KR101696087B1

KR101696087B1 - Method of object searching with supersonic wave and apparatus therefor

Info

Publication number: KR101696087B1
Application number: KR1020150113500A
Authority: KR
Inventors: 유선철; 조한길; 구정회; 조현우; 표주현
Original assignee: 포항공과대학교 산학협력단
Priority date: 2015-08-11
Filing date: 2015-08-11
Publication date: 2017-01-24

Abstract

A method and apparatus for searching an object with an ultrasonic wave are provided. The method for searching an object with an ultrasonic wave according to an exemplary embodiment of the present invention includes a) a step of propagating an ultrasonic wave to a plurality of profiles, acquiring an echo signal for each profile, and obtaining a plurality of echo profiles; B) a step of comparing the echo profile with a previously obtained echo profile; and c) a step of identifying a change in signal strength from the previously obtained echo profile in the echo profile and determining that an object has been searched if the change in the signal strength is confirmed. So, the object can be automatically confirmed.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a method and apparatus for searching an ultrasonic object.

In general, underwater object recognition in shallow water is required in a variety of fields such as underwater pipeline exploration, ocean surface ecological survey, engineering, civil engineering, environment, disaster prevention, and so on.

However, in case of deep sea, turbidity of water is generally high, and therefore, there is a limitation because it is difficult to obtain visibility by using an optical camera. At this time, when the ultrasonic probe is used, it is more effective than the optical camera because it can confirm tens of meters or more even in a state where the turbidity of water is high.

At this time, underwater object recognition must be performed at very high speed in order to shorten the search time because it must be performed over a wide marine area. Therefore, there is a demand for a technique for automatically confirming appearance of a specific object in an ultrasound image photographed while moving a large underwater region at a high speed.

On the other hand, in order to detect the appearance of a specific object in the image, a method of analyzing the difference of pixels between two consecutive image frames is mainly used. At this time, as the difference between the two frames becomes larger, a new object that has not appeared in the previous image frame appears. However, in the case of an ultrasound image, even if a specific object does not appear due to noise or unevenness of the sea floor, there is a difference that can not be ignored between two ultrasound image frames, so that it is difficult to apply to an ultrasound image.

An embodiment of the present invention is to provide an ultrasonic object searching method for automatically confirming the appearance of an object in an image taken while moving a wide underwater region at a high speed.

Also, an embodiment of the present invention is to provide an ultrasonic object searching apparatus which can automatically check the appearance of an object in an image taken while moving at a high speed in a wide underwater region by using an ultrasonic object searching method.

A method for searching an ultrasonic object according to an embodiment of the present invention is a method for searching an ultrasonic object in an ultrasonic object searching apparatus, comprising the steps of: a) propagating an ultrasonic wave to a plurality of profiles and obtaining an echo signal for each profile, Obtaining a plurality of echo profiles, b) comparing the echo profile and the previously obtained echo profile using Equation 1, c) comparing the change in signal strength from the echo profile obtained in the echo profile And determining that the object has been searched if the signal intensity change is confirmed.
The step (c) includes the steps of: (1) generating a graph in which values of an index (k) in which the maximum value of r _i (k) is located through the following equation 1 are arranged in order of echo profiles; If the width and height of the region where the value of the index k is not 0 are less than the threshold value, it is determined that the non-object is searched. If the width and the height of the region are less than the threshold value,
The threshold value is determined according to the size of the object to be searched and the moving speed of the ultrasonic object searching apparatus, and the plurality of echo profiles each have a one-dimensional array and constitute an ultrasound image that is a two-dimensional bitmap image.
At this time, Equation (1) is as follows.
r _i (k) =

(Wherein, p _i (k): group i-th echo of the obtained echo frame profile, q _i (k): i-th echo profile, of the acquired echo frame L: the length of the array in each of the echo profile, the p _i (k) , q _i (k): 1? k? L, r _i (k): -L + 1 = k =
The range of the threshold value with respect to the width of the region where the value of the index (k) is not 0 in the graph is determined according to the size of the search object, and the height of the region where the value of the index (k) The range of the threshold value is determined according to the moving speed of the object to be searched.
In the step c), it is determined that the region where the value of the index (k) is smaller than 0 in the graph is closer to the object, and the region where the value of the index (k) It may be determined that the object searching apparatus is distant from the target object and that the region where the value of the index k is 0 in the graph is determined to be in a stop state.

An ultrasonic object search apparatus according to an embodiment of the present invention includes: (1) a signal transmitting / receiving unit that transmits an ultrasonic signal in a plurality of profiles, acquires an echo signal for each profile, and receives a plurality of echo profiles having a one- And (2) a search unit for comparing the echo profile with the previously obtained echo profile to confirm whether or not an object is searched. If a change in signal intensity is confirmed from the echo profile obtained in the echo profile, .
The searching unit may include: (1) a sampling unit for sampling the echo signal received by the signal receiving unit and converting the sampled echo signal into an echo profile; (2) an echo profile converted by the sampling unit, And calculating the correlation using Equation (1).
In this case, the ultrasonic-wave object search apparatus according to an embodiment of the present invention generates a graph in which the values of the index k where the maximum value of r _i (k) is located through the following Equation 1 are arranged in the order of the echo profiles Then, when the width and height of the region where the value of the index (k) is not 0 in the graph are less than the threshold value, it is determined that the non-object has been searched, and if it exceeds the threshold, it is determined that the object is searched.
The threshold value is determined according to the size of the object to be searched and the moving speed of the ultrasonic object searching apparatus, and the plurality of echo profiles each have a one-dimensional array and constitute an ultrasound image which is a two-dimensional bitmap image.
At this time, Equation (1) is as follows.
r _i (k) =

(Wherein, p _i (k): group i-th echo of the obtained echo frame profile, q _i (k): i-th echo profile, of the acquired echo frame L: the length of the array in each of the echo profile, the p _i (k) , q _i (k): 1? k? L, r _i (k): -L + 1 = k =
The range of the threshold value with respect to the width of the region where the value of the index (k) is not 0 in the graph is determined according to the size of the search object, and the height of the region where the value of the index (k) The range of the threshold value is determined according to the moving speed of the object to be searched.
The search unit determines that the region where the index k is smaller than 0 is closer to the target object in the graph, and the region where the value of the index k is larger than 0 in the graph is an ultrasound object search It is determined that the device is distant from the target object. In the graph, the region where the value of the index (k) is 0 determines that the ultrasonic object search apparatus is stopped.

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The ultrasonic object searching method according to an embodiment of the present invention can provide a method of searching for an underwater object at a higher reliability with a higher reliability.

The ultrasonic object searching apparatus according to an embodiment of the present invention can photograph an image while moving at high speed in water and automatically analyze the photographed image to automatically inform the user when an object is searched.

1 is a flowchart illustrating an ultrasonic object searching method according to an embodiment of the present invention.
FIG. 2 is a view illustrating an echo profile obtained when an object is present according to an ultrasonic object searching method according to an embodiment of the present invention. FIG.
FIG. 3 is a view illustrating an echo profile obtained when an object is not present by an ultrasonic object searching method according to an embodiment of the present invention. FIG.
FIG. 4 is a diagram showing an echo profile of a previous frame (a) and an echo profile of the frame (b) obtained by the ultrasonic object searching method according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating a correlation function obtained using a previous frame and a 50th echo profile of the frame.
FIG. 6 is a graph showing a photograph of an object in a moving image of a submersible robot according to an embodiment of the present invention, and a graph using a correlation function. FIG.
7 is a diagram illustrating a method for identifying an object according to an embodiment of the present invention.
FIG. 8 is a block diagram briefly showing a configuration of an ultrasonic object searching apparatus according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

1, an ultrasonic object search method 100 according to an embodiment of the present invention includes propagating an ultrasonic wave to a plurality of profiles, acquiring an echo signal for each profile, and acquiring a plurality of echo profiles (S110 Comparing the obtained echo profile to the previously obtained echo profile (S120), and confirming a change in signal intensity from the echo profile acquired in the acquired echo profile (S130).

The ultrasonic object searching method of the present invention is a method of searching for an object using ultrasonic waves without any particular limitation. In an embodiment of the present invention, the case of detecting an object using ultrasonic waves in water whose visual field is not secured for convenience is referred to as center .

Hereinafter, a method of searching an object using ultrasound in water according to an embodiment of the present invention will be described in detail.

First, the ultrasonic waves are propagated to a plurality of profiles, and an echo signal is acquired for each profile to acquire a plurality of echo profiles (step S110).

In an embodiment of the present invention, the underwater robot uses sonar, which is one of the underwater search equipment, to search underwater objects using ultrasonic waves.

On the other hand, an underwater robot sends ultrasonic waves. The ultrasonic waves transmitted at this time may be in the form of a plurality of beams having a narrow front and a wide fan shape. The underwater robot acquires an echo signal reflected from an object existing in the traveling direction of a plurality of transmitted beams. At this time, each of the obtained echo signals is a plurality of echo profiles, and the echo profile is data obtained by sampling the intensity of the reflected signals with respect to time, and thus can be expressed in a one-dimensional array. Further, arranging the echo profiles of the one-dimensional array side by side can constitute a two-dimensional bitmap, and such a two-dimensional bitmap constitutes one ultrasound image.

Next, the obtained echo profile is compared with the previously obtained echo profile (step S120).

The underwater robot continuously repeats the process of transmitting the plurality of beams and acquiring the echo profile at predetermined time intervals during movement. Referring to FIG. 2, when the underwater robot moves, it is possible to confirm the echo profile change in the case where an object exists in front of the robot.

When the underwater robot is moving, the relative position between the underwater robot and the object at the moment of acquiring the previous ultrasound image frame and the relative position between the underwater robot and the object at the moment of acquiring the current ultrasound image frame are different. Therefore, it can be seen that the echo profile acquired in the current frame changes in position compared to the echo profile of the previous frame.

Meanwhile, referring to FIG. 3, when the underwater robot moves, it is possible to confirm the echo profile change in the case where a very low-height object is present or an object is not present.

When the underwater robot moves, when the undersurface is uniform, and when an object with a very low height is detected, there is a change in the relative position between the robot and the object in the moment of acquiring the previous ultrasound image frame and the current ultrasound image frame, The degree of profile change is very small. As a result, in the case of small objects, such as gravel, marine litter, and small rocks, which are not objects to be searched for, objects do not exist on the seafloor.

Therefore, in the ultrasonic object search method according to an embodiment of the present invention, when the change amount of the echo profile between the previous frame and the current frame is measured above a predetermined threshold value, it is determined that an object appears.

Meanwhile, referring to FIG. 4, an actual ultrasonic image taken by a moving underwater robot can be confirmed. 4 (a) shows the echo profile of the previous frame, and Fig. 4 (b) shows the echo profile of the current frame.

In the present embodiment, for convenience of explanation, the echo profiles of the previous frame and the echo profile of the current frame are respectively used as the 50th echo profile of the plurality of echo frames.

Comparing the 50th echo profile among a plurality of echo profiles constituting an ultrasound image, the echo profile graph of the previous frame and the current frame show the same object, so the overall shape is similar.

However, since the relative position between the underwater robot and the object changes as the underwater robot moves, the positional change appears in the signal pattern between the echo profile of the previous frame and the echo profile of the current frame.

In one embodiment of the present invention, the positional change of the signal pattern between the two echo profiles can be expressed by Equation (1).

Equation 1

r _i (k) =

(Wherein, p _i (k): the previous frame i-th echo profile, q _i (k): i-th echo profile, L of the current frame: length, p _i (k of each echo profile), q _i (k) : 1? K? L, r _i (k): -L + 1 = k = L-1)

For example, when comparing the 50th echo profile, p _i (k) is represented by p ₅₀ (k) as the 50th echo profile of the previous frame, and q _i (k) ₅₀ (k), and r _i (k) is expressed as r ₅₀ (k) as a correlation function of the 50 th frame.

Finally, a change in the signal strength is confirmed from the echo profile acquired in the obtained echo profile (step S130).

Specifically, by acquiring the correlation function in Equation (1) as an example of FIGS. 4 (a) and 4 (b), a function graph as shown in FIG. 5 can be obtained.

As shown in Fig. 5, the correlation function between the 50th echo profile of the previous frame and the 50th echo profile of the current frame has a maximum value at the point where the index k is -38. That is, since the correlation function shown in Fig. 5 shows that the index k of the position where the correlation function has the maximum value is represented by -38, the 50th echo profile q _i (k) of the current frame is the 50th echo profile p _i (k). At this time, the relative position of the underwater robot and the object can be determined according to the sign of the index k.

If the value of the index k with the maximum correlation function value is less than 0, the echo profile of the current frame moves to the left in comparison with the echo profile of the previous frame. In other words. The echo profile of the current frame is temporally ahead of the echo profile of the previous frame, which means that the relative position of the underwater robot and the object is getting closer.

If the value of the index k having the maximum value of the correlation function is larger than 0, the echo profile of the current frame moves to the right compared with the echo profile of the previous frame. That is, since the echo profile of the current frame is temporally lagging behind the echo profile of the previous frame, it means that the relative position between the underwater robot and the object is distant.

On the other hand, if the value of k in the index having the maximum correlation function value is 0, the echo profile of the current frame and the echo profile of the previous frame are the same. That is, since the time difference between the echo profile of the current frame and the echo profile of the previous frame does not appear, it means a situation where the relative position of the underwater robot and the object is the same as the underwater robot's stop state.

Next, FIG. 6 is a diagram showing an image in which an object is detected during movement of the underwater robot and a maximum value position index graph of the correlation function. In this case, the position index is obtained by arranging the maximum value index of the correlation function between each echo profile of the current frame and each echo profile of the previous frame in order of profiles. That is, the maximum value location index graph of the correlation function can be obtained by arranging the indexes having the maximum value of the correlation function in the profile order.

Intervals 1 and 3 in FIG. 6 do not have any objects. Therefore, the index having the maximum value of the correlation function in the frames corresponding to the intervals 1 and 3 appears to oscillate around zero. At this time, theoretically, if there is no object, the index should be represented as 0 without any change, but it may not be accurately expressed by the noise of the ultrasound image or the unevenness of the undersurface.

On the other hand, in the interval 2 of FIG. 6, a specific object appears. Therefore, the index having the maximum value of the correlation function in the frame corresponding to interval 2 has a constant value other than zero. At this time, it is possible to automatically analyze the size of an object appearing in the search image of the underwater robot by detecting a range having a non-zero index.

FIG. 7 illustrates a method of detecting a non-zero index range according to an embodiment of the present invention. The width of the non-zero index range can be set according to the size of the object of interest. If the non-zero index range is equal to or less than the set threshold value, it is determined that an object smaller than the target object is detected and ignored.

Also, the height of the non-zero index range can be set according to the moving speed of the underwater robot. If the speed of the underwater robot is fast, the amount of change between the echo profile of the current frame and the echo profile of the previous frame increases. Therefore, the maximum value of the correlation function between profiles occurs at the index farther from 0, and the height of the non-zero index range increases in the maximum value position index graph of the correlation function. At this time, if the height of the non-zero index range is smaller than the set threshold value, it is ignored.

That is, it can be determined that an object is detected only when a non-zero index range satisfying both the width and the height of the non-zero index range set through the size of the object to be searched and the moving speed of the robot underwater occurs.

In an embodiment of the present invention, the width and height of the non-zero index range are used as predetermined thresholds for distinguishing objects, but the present invention is not limited thereto.

In addition, when an underwater robot detects an object, that is, when a change in an echo profile is confirmed, it is possible to output the appearance of an object to the outside. In this case, the output may be achieved by providing an information signal to an AUV or a user, for example.

The ultrasonic object search method 100 of FIG. 1 may be implemented through the ultrasonic object search apparatus 800 shown in FIG. Referring to FIG. 8, an ultrasound object searching apparatus 800 according to an embodiment of the present invention includes a signal transmitting / receiving unit 810 and a searching unit 830.

The signal transmitting / receiving unit 810 transmits an ultrasonic signal to search for an underwater object, and receives a reflected echo signal. At this time, the signal transmitting / receiving unit 810 may be included in the sonar mounted on the underwater robot. When the sonar is a passive sonar, the signal transmitting / receiving unit 810 receives a signal transmitted by the object without transmitting the ultrasonic signal. The ultrasonic waves transmitted by the signal transmitting / receiving unit 810 may be in the form of a plurality of beams having a narrow front and a wide fan shape.

The search unit 830 instructs the signal transmission / reception unit 810 to transmit the ultrasonic signal, and analyzes the echo signal received by the signal transmission / reception unit 810. The echo receiving unit 810 compares the echo signal received by the signal transmitting / receiving unit 810 with the previously obtained echo signal to check whether or not the object is searched. At this time, if the change of the signal intensity is confirmed between the received echo signal and the previously obtained echo signal, it is determined that the object is detected. The search unit 830 may include a sampling unit 831 and a calculation unit 833 in more detail.

The sampling unit 831 samples the echo signal received by the signal transmitting / receiving unit 810 and converts it into an echo profile. At this time, the sampling unit 831 acquires the echo profile by sampling the intensity of the echo signal with time. Also, the sampling unit 831 can generate a two-dimensional bitmap image, which is an ultrasound image, using the converted echo profiles.

The calculation unit 833 acquires an echo profile and a two-dimensional bitmap image from the sampling unit 831, and calculates a correlation between the received echo profile and the previously obtained echo profile. At this time, Equation 1 can be used to calculate the correlation between the received echo profile and the previously obtained echo profile. If the value of r _i (k) derived through Equation (1) is less than a predetermined threshold value, the calculation unit 833 determines that the object is not searched. On the other hand, when the value of r _i (k) derived through Equation (1) exceeds a predetermined threshold value, the calculation unit 833 determines that the object is searched. The calculation unit 833 may transmit the correlation information to the sampling unit 831 so as to show the object in the ultrasound image of the sampling unit 831. [

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

800: Ultrasonic object search device
810: Signal transmitting / receiving unit 830:
831: Sampling unit 833:

Claims

A method of searching an ultrasonic object of an ultrasonic object searching apparatus,
a) propagating an ultrasonic wave to a plurality of profiles and obtaining an echo signal for each profile to obtain a plurality of echo profiles having a one-dimensional array;
b) comparing the echo profile and the previously obtained echo profile using Equation 1; And
c) checking a change in signal strength from the echo profile obtained in the echo profile, and determining that the object is searched if a change in signal strength is confirmed,
The step c)
Generating a graph in which values of an index (k) in which a maximum value of r _i (k) is located through Equation (1) are arranged in order of echo profiles; And
Determining that a non-object has been searched when the width and height of an area where the value of the index k is not 0 is less than a threshold value in the graph and determining that the object has been searched if the value is greater than a threshold value,
The threshold value may be set to &
The range is determined according to the size of the object to be searched and the moving speed of the ultrasonic object searching apparatus,
Wherein the plurality of echo profiles comprise:
Dimensional array, each of which is a one-dimensional array, and constitutes an ultrasound image, which is a two-dimensional bitmap image.
Equation 1
r _i (k) =

(Wherein, p _i (k): group i-th echo of the obtained echo frame profile, q _i (k): i-th echo profile, of the acquired echo frame L: the length of the array in each of the echo profile, the p _i (k) , q _i (k): 1? k? L, r _i (k): -L + 1 = k =

The method according to claim 1,
The range of the threshold value with respect to the width of the region where the value of the index (k) is not 0 in the graph is determined according to the size of the search object,
Wherein the range of the threshold value for the height of the region where the value of the index (k) is not 0 in the graph is determined according to the moving speed of the object to be searched.

The method according to claim 1,
The step c)
In the graph, the region where the value of the index k is smaller than 0 determines that the ultrasonic-wave object search apparatus approaches the object,
In the graph, the region where the value of the index (k) is larger than 0 determines that the ultrasonic wave object search apparatus is distant from the object,
Further comprising the step of determining that the region where the value of the index (k) is 0 in the graph indicates that the ultrasonic object search apparatus is in a stop state.

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In the ultrasonic object searching apparatus,
A signal transceiver for transmitting an ultrasonic signal in a plurality of profiles, acquiring an echo signal for each profile, and receiving a plurality of echo profiles having a one-dimensional array; And
And a search unit for comparing the echo profile with the previously acquired echo profile to check whether the object is searched,
If the change in the signal strength is confirmed from the echo profile obtained in the echo profile, it is determined that the object has been found,
The searching unit searches,
A sampling unit for sampling the echo signal received by the signal transmitting and receiving unit and converting the echo signal into an echo profile; And
And calculating a correlation between an echo profile of a previous frame and an echo profile of the current frame by obtaining an echo profile converted by the sampling unit using Equation (1)
A graph in which the value of the index k where the maximum value of r _i (k) is located through the following Equation 1 is arranged in the order of each echo profile is generated, and then a value of the index (k) If the width and height of the area are less than the threshold value, it is determined that the non-object is searched. If the width and height are greater than the threshold value,
The threshold value may be set to &
The range is determined according to the size of the object to be searched and the moving speed of the ultrasonic object searching apparatus,
Wherein the plurality of echo profiles comprise:
Dimensional image, each of which has a one-dimensional array and constitutes an ultrasound image as a two-dimensional bitmap image.
Equation 1
r _i (k) =

10. The method of claim 9,
The range of the threshold value with respect to the width of the region where the value of the index (k) is not 0 in the graph is determined according to the size of the search object,
Wherein the range of the threshold value for the height of the region where the value of the index (k) is not 0 in the graph is determined according to the moving speed of the object to be searched.

10. The method of claim 9,
The searching unit searches,
In the graph, the region where the value of the index k is smaller than 0 determines that the ultrasonic-wave object search apparatus approaches the object,
In the graph, the region where the value of the index (k) is larger than 0 determines that the ultrasonic wave object search apparatus is distant from the object,
Wherein the ultrasonic object search apparatus determines that the region where the value of the index (k) is 0 in the graph is in the stop state.

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