Ultrasonic sensor for distinguishing material of object and operating method thereof

Abstract

An ultrasonic sensor according to the present invention comprises: an ultrasonic generator for emitting ultrasonic waves to an object in response to a control signal; an ultrasonic receiver for receiving a plurality of reflected waves generated by being reflected from a surface of the object; and a control circuit for controlling the ultrasonic generator and the ultrasonic receiver, wherein the control circuit distinguishes the material of the object using the magnitude and arrival time of the plurality of reflected waves.

Description

Ultrasonic sensor for distinguishing the material of an object and its operating method

[0001] The present technology relates to an ultrasonic sensor capable of distinguishing the material of an object and an operating method thereof.

[0002] An ultrasonic sensor includes a transducer that generates ultrasonic waves and receives the ultrasonic waves and converts them into electrical signals.

[0003] Since the speed of sound is a predetermined value, the distance to an object can be measured by generating an ultrasonic signal and measuring the time it takes for the ultrasonic signal to reflect from the object and return.

[0004] However, there is a problem in that it is impossible to distinguish the material of an object by measuring the time until the reflected wave is received.

[0005] The present technology provides an ultrasonic sensor capable of distinguishing the material of an object using ultrasonic waves and an operating method thereof.

[0006] An ultrasonic sensor according to one embodiment of the present invention includes: an ultrasonic generator that emits ultrasonic waves to an object according to a control signal; an ultrasonic receiver that receives a plurality of reflected waves generated by reflection from the surface of the object; and a control circuit that controls the ultrasonic generator and the ultrasonic receiver, wherein the control circuit distinguishes the material of the object using the magnitude and arrival time of the plurality of reflected waves.

[0007] According to one embodiment of the present invention, a method for operating an ultrasonic sensor includes an ultrasonic generator that emits ultrasonic waves to an object according to a control signal; and an ultrasonic receiver that receives a plurality of reflected waves generated by reflection from a surface of the object, the method comprising: measuring the magnitude of the plurality of reflected waves in the ultrasonic receiver; calculating a travel distance of the plurality of reflected waves according to arrival times of the plurality of reflected waves; calculating a reflectivity according to the magnitude of the plurality of reflected waves and the travel distance of the plurality of reflected waves; and determining a material of the object according to the reflectivity.

[0008] The ultrasonic sensor according to this technology can not only measure the distance to an object using ultrasonic waves, but also distinguish the material of the object.

[0009] Fig. 1 is a block diagram showing an ultrasonic sensor according to one embodiment of the present invention.

[0010] FIG. 2 is an explanatory diagram showing the phenomenon of ultrasonic reflection between an ultrasonic sensor and an object according to one embodiment of the present invention.

[0011] Figures 3 and 4 are graphs showing the size of a reflected wave received by an ultrasonic sensor according to one embodiment of the present invention.

[0012] Figure 5 is a flowchart showing the operation of an ultrasonic sensor according to one embodiment of the present invention.

[0013] Hereinafter, an embodiment of the present invention is disclosed with reference to the attached drawings.

[0014] FIG. 1 is a block diagram showing an ultrasonic sensor (1000) according to one embodiment of the present invention.

[0015] The ultrasonic sensor (1000) includes an ultrasonic transducer (100) and a control circuit (200).

[0016] The ultrasonic transducer (100) includes an ultrasonic generator (110) and an ultrasonic receiver (120).

[0017] Since the ultrasonic generator (110) and the ultrasonic receiver (120) themselves are well known to those skilled in the art, a detailed description thereof will be omitted.

[0018] In this embodiment, the ultrasonic generator (110) and the ultrasonic receiver (120) are implemented as one module sharing a circuit board.

[0019] In another embodiment, the ultrasonic generator (110) and the ultrasonic receiver (120) may be implemented as independent modules that do not share a circuit board, and various other design changes may be possible.

[0020] The control circuit (200) controls the operation of the ultrasonic transducer (100) to perform operations such as measuring the distance to an object and distinguishing the material of the object.

[0021] The control circuit (200) can control the ultrasonic generator (110) to emit ultrasonic waves using a control signal. Hereinafter, the ultrasonic waves emitted from the ultrasonic generator (110) are referred to as radiated waves.

[0022] The control circuit (200) can control the ultrasonic receiver (120) to measure the size of the ultrasonic waves received by the ultrasonic receiver (120) along with the elapsed time since the ultrasonic waves were emitted. Hereinafter, the ultrasonic waves received by the ultrasonic receiver (120) are referred to as reflected waves.

[0023] The control circuit (200) can perform an operation of measuring the distance to an object to be measured and an operation of distinguishing the material of the object by using the size and reception time information of the reflected wave received by the ultrasonic receiver (120).

[0024] The control circuit (200) may include an operation circuit (210) that performs operations during distance measurement or material discrimination operations. The operation circuit (210) may perform mathematical operations and logical operations.

[0025] FIG. 2 is an explanatory diagram showing an ultrasonic reflection phenomenon between an ultrasonic sensor and an object according to one embodiment of the present invention.

[0026] In Figure 2, the radiated wave is indicated by a solid line, and the reflected wave is indicated by a dotted line.

[0027] In (A), multiple solid lines represent radiated waves in wave form, and multiple dotted lines represent reflected waves in wave form.

[0028] (B) represents the reflection phenomenon of ultrasonic waves between the ultrasonic transducer (100) and the surface (1) of the object. Hereinafter, the surface (1) of the object may be briefly referred to as the object (1).

[0029] The primary radiation wave initially radiated from the ultrasonic transducer (110) is reflected from the object (1) to generate a primary reflected wave.

[0030] The primary reflected wave is reflected again from the surface of the ultrasonic transducer (110) to generate a secondary radiated wave.

[0031] The secondary radiation wave is reflected again from the object (1) to generate a secondary reflected wave.

[0032] This phenomenon continues until the size of the ultrasound is reduced to a negligible level.

[0033] The ultrasonic receiver (120) detects the peak of the reflected wave and sequentially detects a plurality of reflected waves generated according to the echo phenomenon.

[0034] FIG. 3 and FIG. 4 are graphs showing the size of a reflected wave measured by an ultrasonic sensor (1000) according to one embodiment of the present invention.

[0035] Figure 3 corresponds to the case where the object (1) is made of a hard material, and Figure 4 corresponds to the case where the object (1) is made of a soft material.

[0036] The horizontal axis of the graph represents elapsed time converted into distance, expressed by the relationship (distance) = (elapsed time) x (speed of sound) / 2. The speed of sound was assumed to be 340 m / s.

[0037] The time between adjacent peaks in the graph corresponds to the time it takes for the sound wave to travel back and forth between the ultrasonic sensor (1000) and the object (1). Applying the above relationship, the distance of 30 mm between adjacent peaks in the graph corresponds to the gap between the ultrasonic sensor (1000) and the object (1).

[0038] The vertical axis of the graph represents the size of the reflected wave in arbitrary units (AU).

[0039] In Fig. 3, the initial peak indicates that the maximum signal is received by the ultrasonic receiver (120) due to the electrical and mechanical resonance phenomenon between the ultrasonic transmitter (110) and the ultrasonic receiver (120) immediately after the primary radiation wave is generated.

[0040] That is, the initial peak is not received after the primary radiation wave is reflected from the object (1), so it is not used to measure the distance between the ultrasonic sensor (1000) and the object (1).

[0041] In Fig. 3, the first peak corresponds to the point in time when the first reflected wave is received, the second peak corresponds to the point in time when the second reflected wave is received, the third peak corresponds to the point in time when the third reflected wave is received, and the fourth peak corresponds to the point in time when the fourth reflected wave is received.

[0042] Subsequent reflections are received and corresponding peaks are generated.

[0043] In this embodiment, peaks below the peak threshold are ignored in the process of determining the reflectance.

[0044] In Figures 3 and 4, it is assumed that the peak threshold is set to 90 and peaks below 90 are ignored.

[0045] Details regarding the determination of reflectivity are disclosed again below.

[0046] The graph in Figure 3 corresponds to an object made of a hard material.

[0047] In Fig. 3, the receiving start point is D A and mark the receiving end point as D B It was marked as .

[0048] 0 ~ D A The interval in between is the interval including the initial peak, and is the interval in which a signal is received by the ultrasonic receiver (120) due to the resonance phenomenon between the ultrasonic transmitter (110) and the ultrasonic receiver (120) immediately after the primary radiation wave is generated, as described above.

[0049] Below, 0 ~ D AThe interval in between can be referred to as the resonance interval.

[0050] When the distance between the ultrasonic sensor (1000) and the object (1) is shorter than the resonance section, it is difficult to measure the distance to the object (1).

[0051] D, where the size of the reflected wave gradually increases A It can be seen that the first reflected wave begins to be received after the point. The point where the magnitude of the first reflected wave is maximum is indicated as the first peak.

[0052] Afterwards, the second, third, and fourth reflected waves are received, and the second, third, and fourth peaks occur sequentially.

[0053] When the peak threshold is set to 90, the receiving end point is D B corresponds to . After the receiving end point, no peaks exceeding the peak threshold occur.

[0054] Below, D A ~ D B The interval in between can be referred to as the reflected wave reception interval.

[0055] By integrating the amplitude of the sound waves received during the reflected wave reception period, the total energy of the reflected wave can be measured.

[0056] The graph in Fig. 4 corresponds to an object (1) made of soft material.

[0057] In the graph of Figure 4, since there are peaks below the peak threshold, the distance between peaks can be measured.

[0058] However, in the graph of Fig. 4, the reflected wave reception section is significantly reduced compared to Fig. 3, indicating that only the first peak exists within the reflected wave reception section.

[0059] It is known that the amplitude of an ultrasonic signal in free space decreases proportionally to the square of the travel distance.

[0060] When ultrasound hits a rough surface or an object smaller than the wavelength, a scattering effect occurs, causing it to scatter in all directions. It is known that the scattering effect is proportional to the fourth power of the frequency.

[0061] Additionally, it is known that when ultrasound passes through the boundary between two media with different refractive indices, some of it is refracted and absorbed.

[0062] Unlike hard objects such as wooden floors, soft fibrous objects such as carpets have a higher sound absorption rate and are characterized by more sound scattering from their surfaces.

[0063] Accordingly, the reflectivity on the surface of a soft object tends to decrease significantly compared to the surface of a hard object.

[0064] Taking these points into account, this technology distinguishes the material of an object using reflectance.

[0065] Physically, the reflectance (R) can be defined as in mathematical equation 1.

[0066]

[0067] In mathematical expression 1, a is a proportional constant, G RX is the gain of the ultrasonic receiver (120), P TX represents the energy used to emit ultrasonic waves from the ultrasonic transmitter (110), and P r (x) represents the energy of the reflected wave at point x. The integration period can be limited to the aforementioned reflected wave reception period.

[0068] The reflectivity of ultrasonic waves is not only affected by the material of the object, but can also vary due to various factors such as the angle between the ultrasonic sensor (1000) and the surface of the object and the relative movement speed.

[0069] Accordingly, in this embodiment, the modified reflectance (R) of mathematical expression 2 is used instead of the physical reflectance of mathematical expression 1. M ) is used.

[0070] Below, the transformed reflectance (R M ) is referred to as reflectance.

[0071] In this example, the reflectance (R M ) considers both the size of the reflected wave received by the ultrasonic receiver (120) and the travel distance of the reflected wave.

[0072] At this time, the size and travel distance of the reflected wave are based on the peak.

[0073]

[0074] In mathematical expression 2, v represents the proportionality constant, and V i represents the output value of the ultrasonic receiver (120) corresponding to the i-th peak, and D i represents the total travel distance of the reflected wave corresponding to the ith peak.

[0075] Additionally, N is determined by the number of peaks having values ​​greater than the peak threshold. Assuming the peak threshold is 90, N=4 in the case of Fig. 4, and N=1 in the case of Fig. 5.

[0076] Figure 5 is a flowchart showing the operation of an ultrasonic sensor (1000) according to one embodiment of the present invention.

[0077] First, the peak size of the reflected wave received by the ultrasonic receiver (120) is measured (S100).

[0078] The reflected wave corresponding to the i-th peak, i.e. the peak magnitude (V) of the i-th reflected wave i ) corresponds to the Vi value in mathematical expression 2.

[0079] In the case of Fig. 3, V1= 240, V2= 215, V3= 200, V4= 180 correspond, and in the case of Fig. 4, V1= 210 correspond.

[0080] Next, the travel distance of the reflected wave is calculated based on the arrival time of the reflected wave (S200).

[0081] At this time, the total travel distance (D) of the reflected wave corresponding to the i-th peak, i.e., the i-th reflected wave i ) represents the distance traveled by the ultrasound until the ith peak occurs after the first emission of the ultrasound.

[0082] As described above, the distance between the ultrasonic sensor (1000) and the object (1) in FIGS. 3 and 4 is 30 mm.

[0083] Therefore, in the case of Fig. 3, D1= 60 mm, D2= 120 mm, D3= 180 mm, D4= 240 mm corresponds, and in the case of Fig. 4, D1= 60 mm corresponds.

[0084] Next, the magnitude of the reflected wave (V i ) and travel distance (D i ) and calculate the reflectance (S300).

[0085] Mathematical expression 2 gives the magnitude of the peak and the peak (V) for each peak located within the reflected wave reception section. i ) total travel distance (D) i ) is calculated by accumulating the value obtained by multiplying the square of the reflectance.

[0086] In mathematical expression 2, the proportional constant v is a single expression that synthesizes the factors that have a constant influence each time the reflectance is measured.

[0087] For example, in mathematical expression 1, a, G RX , P TX Elements such as these are components that do not change and remain at a constant value each time the reflectance is measured.

[0088] The proportional constant v in Equation 2 is a single expression of these and can be adjusted according to the embodiment. For example, the proportional constant v can be set to a value within a certain range that does not cause the reflectivity of Equation 2 to overflow or underflow.

[0089] Next, the material of the object surface is distinguished by comparing the produced reflectance with the material critical point (S400).

[0090] If the reflectivity is above a predetermined material threshold, the material of the object can be judged as a hard material, and if the reflectivity is below a predetermined material threshold, the material of the object can be judged as a soft material.

[0091] At this time, the hard material can be referred to as the first material, and the soft material can be referred to as the second material.

[0092] In order to determine the material critical point, experiments are conducted using various hard objects and various soft objects, and for each case, graphs such as those in Figs. 3 and 4 are determined, and then the reflectance as in mathematical expression 2 can be calculated for each case.

[0093] The material critical point can be determined by considering the statistical distribution of reflectivity corresponding to a hard object and the statistical distribution of reflectivity corresponding to a soft object as a result of the experiment.

[0094] For example, the average value of the reflectivity corresponding to a hard object and the average value of the reflectivity corresponding to a soft object can be calculated, and the median value of these can be determined as the material critical point.

[0095] The experimental method for predetermining the material critical point can be varied in various ways by a person skilled in the art, so further disclosure is omitted.

[0096] The scope of the present invention is not limited by the above disclosure. The scope of the present invention should be interpreted based on the scope literal in the claims and their equivalents.

Claims

1. An ultrasonic generator that radiates ultrasonic waves to an object according to a control signal; An ultrasonic receiver that receives a plurality of reflected waves generated by reflection from the surface of the object; and A control circuit that controls the ultrasonic generator and the ultrasonic receiver Including, but not limited to, The above control circuit is an ultrasonic sensor that distinguishes the material of the object by using the size and arrival time of the plurality of reflected waves.

2. In claim 1, the control circuit calculates an i-th partial product which is the product of the size of the i-th peak (i ​​is a natural number) among the plurality of peaks corresponding to the plurality of reflected waves and the square of the movement distance of the i-th peak, and calculates a reflectivity by accumulating the plurality of partial products corresponding to the plurality of peaks, wherein the movement distance of the i-th peak is (2i) x (the distance between the ultrasonic sensor and the object).

3. An ultrasonic sensor according to claim 2, wherein the plurality of peaks have values ​​greater than a predetermined peak threshold.

4. In claim 2, when the reflectivity is equal to or greater than a predetermined material threshold, the control circuit determines the material of the object as a first material, and when the reflectivity is less than the predetermined material threshold, the control circuit determines the material of the object as a second material, wherein the first material is a harder material than the second material.

5. A method of operating an ultrasonic sensor, comprising: an ultrasonic generator that emits ultrasonic waves to an object according to a control signal; and an ultrasonic receiver that receives a plurality of reflected waves generated by reflection from the surface of the object. A step of measuring the size of the plurality of reflected waves in the ultrasonic receiver; A step of calculating the travel distance of the plurality of reflected waves based on the arrival times of the plurality of reflected waves; A step of calculating a reflectivity based on the sizes of the plurality of reflected waves and the travel distance of the plurality of reflected waves; and A step of determining the material of the object based on the above reflectivity A method of operating an ultrasonic sensor including:

6. In claim 5, the operating method of the ultrasonic sensor, wherein the size of the plurality of reflected waves corresponds to the size of the plurality of peaks corresponding to the plurality of reflected waves.

7. In claim 5, the step of calculating the travel distance of the plurality of reflected waves is A step of determining the distance between the ultrasonic sensor and the object based on the occurrence time of a plurality of peaks corresponding to the plurality of reflected waves; and A step of calculating the travel distance of the plurality of reflected waves based on the occurrence time of the plurality of peaks. Including, but not limited to, An operating method of an ultrasonic sensor, wherein the travel distance of the i-th reflected wave (i is a natural number) among the above plurality of reflected waves is (2i) x (the distance between the ultrasonic sensor and the object).

8. In claim 5, the step of calculating the reflectance is A step of calculating the ith partial product, which is the product of the size of the ith peak (i ​​is a natural number) among the plurality of peaks corresponding to the plurality of reflected waves and the square of the moving distance of the ith peak; and A step of accumulating a plurality of partial products corresponding to the plurality of peaks. A method of operating an ultrasonic sensor including:

9. A method for operating an ultrasonic sensor according to claim 5, wherein the plurality of peaks have values ​​greater than a predetermined peak threshold.

10. In claim 5, the step of determining the material of the object comprises: A step of comparing the above reflectivity with a predetermined material critical point; and A step of determining the material of the object as a first material if the reflectivity is greater than or equal to a predetermined material threshold, and determining the material of the object as a second material if the reflectivity is less than or equal to a predetermined material threshold. A method of operating an ultrasonic sensor, wherein the first material is harder than the second material.

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