JP7680944B2 - Distance measuring device, road surface recognition method, and estimation device - Google Patents

Description

This disclosure relates to a distance measuring device, a road surface recognition method, and an estimation device.

A known distance measuring device is one that emits a transmitted wave such as an ultrasonic wave or a laser, receives the reflected wave reflected by the road surface, and detects the road surface based on the received wave. Patent Document 1 discloses a technology that determines the presence of a depression in the road surface by comparing the shape of the received wave with the shape of previously received waves to detect missing parts.

JP 2015-132511 A

The technology in Patent Document 1 can detect the presence of depressions in the road surface, but cannot detect the height of the depressions in the road surface. Therefore, there has been a demand for technology that can detect the height of depressions in the road surface.

According to one embodiment of the present disclosure, a distance measuring device (100) is provided. The distance measuring device includes a sensor unit (10) that has a wave emitting unit (11) that emits waves and a receiving unit (12) that receives reflected waves generated when the waves are reflected by a target, and that can measure the distance to an object present in a predetermined detection range in the front-rear direction of the emitting unit using the reflected waves, and a calculation unit (20) that calculates a step height, which is the height of a downward step on a road surface, using the distance measured by the sensor unit. When a non-reflection section exists between a first reflection section caused by a reflected wave from a first road surface and a second reflection section caused by a reflected wave from a second road surface that is a road surface farther from the distance measuring device in the front-rear direction than the first reflection section, the calculation unit detects the non-reflection section from the reception intensity of the reflected wave, and calculates the step height based on the positional relationship between the sensor unit and the non-reflection section and the first distance, which is the straight-line distance from the end point of the first reflection section to the start point of the second reflection section.

This type of distance measuring device can calculate the step height based on the positional relationship between the sensor unit and the non-reflective section and the first distance.

FIG. 1 is an explanatory diagram showing an outline of the configuration of a distance measuring device. FIG. 13 is an explanatory diagram showing an example of a downward step. 11 is a flowchart showing an example of a step height calculation process. 1 is a graph showing the relationship between distance and reception strength. FIG. 11 is an explanatory diagram showing a non-reflection section in the second embodiment. FIG. 13 is an explanatory diagram showing a non-reflection section in the third embodiment. 13 is a graph showing the relationship between distance and reception intensity in the fourth embodiment. FIG. 13 is an explanatory diagram showing an example of a downward step in the fifth embodiment.

A. First embodiment:
As shown in Fig. 1, the distance measuring device 100 includes a sensor unit 10, a calculation unit 20, and an output unit 30. The distance measuring device 100 detects the distance to a surrounding object. The distance measuring device 100 is, for example, a sonar mounted on a vehicle. As the distance measuring device 100, a millimeter wave radar, LiDAR (Light Detection and Ranging), or a TOF camera (TOF: Time Of Flight) capable of measuring a three-dimensional position by using the flight time of light can be adopted.

The sensor unit 10 has an emission unit 11 that emits an emission wave, and a receiving unit 12 that receives various reflected waves generated when the emission wave is reflected by a target. The sensor unit 10 can measure the distance to an object that exists in a predetermined detection range in the forward and backward directions of the emission unit 11, using the reflected waves received by the receiving unit 12. The forward and backward directions of the emission unit 11 are directions that are determined based on the distance measuring device 100. In this embodiment, the emission unit 11 emits sound waves as the emission wave. The emission unit 11 may also emit radio waves or light waves.

The calculation unit 20 uses the distance measured by the sensor unit 10 to calculate the step height, which is the height of a downward step on the road surface. As shown in FIG. 2, a "downward step" is a step 303 that exists between a first road surface 301 and a second road surface 302 that is farther from the distance measuring device 100 than the first road surface 301 in the extension direction of the road surface, and is a step 303 that descends from the first road surface 301. In this disclosure, a recess that exists between the first road surface 301 and the second road surface 302 is also included in the downward step. Below, a method in which the calculation unit 20 calculates the step height ht is described using the shape of the road surface shown in FIG. 2 as an example. Details of how the calculation unit 20 calculates the step height ht will be described later.

The output unit 30 (see FIG. 1) outputs the step height calculated by the calculation unit 20. The output unit 30 outputs the step height, for example, to a vehicle equipped with the distance measuring device 100. The calculation unit 20 and the output unit 30 are collectively referred to as the estimation device 200.

The step height calculation process shown in FIG. 3 is a process in which the calculation unit 20 calculates the step height ht. In step S100, the calculation unit 20 acquires the reception intensity of the reflected waves. More specifically, the calculation unit 20 acquires the reception intensity of each reflected wave generated by the sensor unit 10 reflecting off the road surface and acquired by the receiving unit 12 at a certain point in time.

In step S110, the calculation unit 20 detects a non-reflection section from the reception intensity acquired in step S100. More specifically, if a non-reflection section exists between a first reflection section due to a reflected wave from the first road surface 301 and a second reflection section due to a reflected wave from the second road surface 302, the calculation unit 20 detects the non-reflection section from the reception intensity of the reflected wave. In this embodiment, a "non-reflection section" is a section in which there are successive positions where the reception intensity is lower than a predetermined value. A non-reflection section is a section of the road surface where the emitted wave from the sensor unit 10 does not reach due to a step 303. If a non-reflection section is not detected, the calculation unit 20 may end the step height calculation process.

The vertical axis of the graph shown in FIG. 4 indicates the reception strength of the reflected wave acquired by the receiving unit 12. The horizontal axis indicates the distance from the sensor unit 10. In this embodiment, the calculation unit 20 detects a section where the reception strength is 0 as a non-reflection section. The section from distance d1 to distance d2 in FIG. 4 is the first reflection section A1, and the section from distance d3 to distance d4 is the second reflection section A2. The section between the first reflection section A1 and the second reflection section A2 is the non-reflection section A3. Note that in this embodiment, the reception strength in the non-reflection section A3 is 0, but this is not limited thereto, and the reception strength in the non-reflection section A3 may be greater than 0.

In this embodiment, the start point S1 (see FIG. 2) of the first reflection section A1 is located at a distance d1 from the sensor section 10, and the end point E1 (see FIG. 2) of the first reflection section A1 is located at a distance d2 from the sensor section 10. The start point S2 (see FIG. 2) of the second reflection section A2 is located at a distance d3 from the sensor section 10, and the end point E2 (see FIG. 2) of the second reflection section A2 is located at a distance d4 from the sensor section 10. The start points S1, S2 and the end points E1, E2 are points that indicate three-dimensional coordinates. The start points S1, S2 and the end points E1, E2 are located on the same straight line in the front-to-rear direction of the emission section 11.

In step S120 (see FIG. 3), the calculation unit 20 estimates a first distance Ln (see FIG. 2), which is the straight-line distance from the end point E1 of the first reflection interval A1 to the start point S2 of the second reflection interval A2. In this embodiment, the calculation unit 20 calculates the difference between the straight-line distance Ru (see FIG. 2) to the end point E1 measured by the sensor unit 10 and the straight-line distance Rl (see FIG. 2) to the start point S2 measured by the sensor unit 10 as the first distance Ln. In other words, the calculation unit 20 calculates the distance obtained by subtracting the distance d2 from the distance d3 as the first distance Ln.

In FIG. 2, for ease of explanation, the straight line represented by the two-dot chain line connecting the distance measuring device 100 and the end point E2 of the second reflection section A2 is shifted upwards, but in reality, it partially overlaps with the straight line represented by the one-dot chain line connecting the distance measuring device 100 and the end point E1 of the first reflection section A1 and the straight line represented by the solid line connecting the end point E1 and the start point S2 of the second reflection section A2.

In step S130 (see FIG. 3), the calculation unit 20 calculates the step height ht based on the positional relationship of the non-reflective section A3 detected in step S110 and the first distance Ln estimated in step S120. More specifically, the calculation unit 20 calculates the step height ht using one or more of the straight-line distance Ru, the straight-line distance Rl, and the section distance Lst (see FIG. 2), which is the distance of the first reflective section A1, as well as the first distance Ln and the straight-line distance hs. In this embodiment, the calculation unit 20 calculates the step height ht using the following formula (1).

ht=Ln×(hs/Ru)…(1)
Here, hs is the height from the first road surface 301 to the distance measuring device 100. In this embodiment, the calculation unit 20 stores a previously measured distance from the road surface to the sensor unit 10. That is, in this embodiment, the calculation unit 20 calculates the step height ht assuming that the ratio between the straight-line distance hs and the straight-line distance Ru is the same as the ratio between the step height ht and the first distance Ln.

According to the distance measuring device 100 of this embodiment described above, the non-reflective section A3 is detected from the reception intensity. The calculation unit 20 calculates the step height ht based on the positional relationship between the detected non-reflective section A3 and the sensor unit 10 and the first distance Ln. Therefore, the step height ht of the downward step can be calculated.

In addition, in this embodiment, the calculation unit 20 calculates the first distance Ln by setting the linear distance Ru to the end point E1 measured by the sensor unit 10 as distance d2, and the linear distance Rl to the start point S2 measured by the sensor unit 10 as distance d3. Therefore, the calculation unit 20 can calculate the step height ht using the estimated first distance Ln without using any other sensors.

B. Second embodiment:
5, the second embodiment differs from the first embodiment in that the calculation unit 20 detects sections in which the reception intensity is equal to or greater than a threshold as the first reflection section A1b and the second reflection section A2b. The configuration of the distance measuring device 100 of the second embodiment is the same as that of the distance measuring device 100 of the first embodiment, and therefore a description of the configuration of the distance measuring device 100 will be omitted.

In this embodiment, the threshold is a value determined according to the distance from the distance measuring device 100. More specifically, the calculation unit 20 determines the threshold using a predetermined function Fth. The function Fth has a smaller threshold as the distance increases. The calculation unit 20 detects a position at a distance d1b from the sensor unit 10 where the reception intensity rises above the threshold as the start point of the first reflection interval A1b, and detects a position at a distance d2b from the sensor unit 10 farther than the start point of the first reflection interval A1b where the reception intensity first falls below the threshold as the end point of the first reflection interval A1. In addition, the calculation unit 20 detects a position that is a distance d3b from the sensor unit 10, which is a position farther than the end point of the first reflection interval A1b and where the reception intensity first rises above the threshold, as the start point of the second reflection interval A2b, and detects a position that is a distance d4b from the sensor unit 10, which is a position farther than the start point of the second reflection interval A2b and where the reception intensity first falls below the threshold, as the end point of the second reflection interval A2.

According to the distance measuring device 100 of the second embodiment described above, the calculation unit 20 can detect the section where the reception strength is equal to or greater than the threshold as the first reflection section A1b and the second reflection section A2b. In other words, it can detect the section where the reception strength is equal to or less than the threshold as the non-reflection section A3b.

C. Third embodiment:
6, the third embodiment differs from the first embodiment in that the calculation unit 20 detects a non-reflection section A3c based on the maximum values P1 to P9 in a graph showing the relationship between the reception intensity and the distance. Since the configuration of the distance measuring device 100 of the third embodiment is the same as that of the distance measuring device 100 of the first embodiment, a description of the configuration of the distance measuring device 100 will be omitted.

The calculation unit 20 performs the process of calculating the difference between the distance value, which is the position on the horizontal axis of the first maximum value, and the distance value, which is the position on the horizontal axis of the second maximum value, which is located farther from the sensor unit 10 than the first maximum value and is adjacent to the first maximum value, at least once, and detects the position of the first maximum value as the end point of the first reflection section A1c and the position of the second maximum value as the start point of the second reflection section A2c among the first maximum value and the second maximum value whose difference is first equal to or greater than a predetermined threshold distance. The "threshold distance" is a distance determined according to the step height ht of the downward step to be detected and the length of the non-reflective section A3c. In this embodiment, the calculation unit 20 detects the non-reflective section A3 based on the maximum value equal to or greater than a threshold value determined using a predetermined function Fth. That is, the calculation unit 20 detects the non-reflective section A3 based on the maximum values P1 to P9.

More specifically, the calculation unit 20 first obtains the difference between the distance d1c of the maximum value P1 and the distance d1c2 of the maximum value P2. It is determined whether the difference is equal to or greater than the threshold distance. The calculation unit 20 also repeatedly obtains the difference between the maximum value P2 and the maximum value P3, the maximum value P3 and the maximum value P4, and the maximum value P4 and the maximum value P5, and determines whether the difference is equal to or greater than the threshold distance. Since the difference between the distance d2c of the maximum value P4 and the distance d3c of the maximum value P5 is the first to be equal to or greater than the threshold distance, the calculation unit 20 detects the position of the maximum value P4 as the end point of the first reflection section A1c and detects the position of the maximum value P5 as the start point of the second reflection section A2c. That is, the calculation unit 20 detects the position of the maximum value P4 as the start point of the non-reflection section A3c and detects the position of the maximum value P5 as the end point of the non-reflection section A3c. In this embodiment, the calculation unit 20 detects the position of the maximum value P1, which is a distance d1c from the sensor unit 10, as the start point of the first reflection interval A1c, and detects the position of the maximum value P9, which is a distance d4c from the sensor unit 10, as the end point of the second reflection interval A2c.

The distance measuring device 100 of the third embodiment described above detects the non-reflection section A3c based on the maximum values P1 to P9 in the graph showing the relationship between reception intensity and distance, so that the section where the distance between adjacent maximum values is equal to or greater than the threshold distance can be detected as the non-reflection section A3.

D. Fourth embodiment:
The fourth embodiment differs from the first embodiment in that the calculation unit 20 determines erroneous detection of the sensor unit 10. Since the configuration of the distance measuring device 100 of the fourth embodiment is the same as the configuration of the distance measuring device 100 of the first embodiment, a description of the configuration of the distance measuring device 100 will be omitted.

The vertical axis of the graph shown in FIG. 7 indicates the reception strength of the reflected wave acquired by the receiving unit 12. The horizontal axis indicates the distance from the sensor unit 10. As shown in FIG. 7, in the first reflection section A1, the reception strength is 0 in the non-reflection section A4 from distance d1x to distance d1y. Since FIG. 7 shows the case where the shape of the road surface shown in FIG. 2 was measured, the non-reflection section A4 is a non-reflection section that is not caused by a downward step.

The calculation unit 20 determines whether the sensor unit 10 has detected an erroneous detection by comparing the reception strength of the reflected wave before and after the movement of the sensor unit 10. More specifically, the calculation unit 20 determines whether the sensor unit 10 has detected an erroneous detection when the difference between the amount of change in the distance of the start point of the non-reflective section A4 detected based on the reception strength of the reflected wave before and after the movement of the sensor unit 10 and the amount of movement of the sensor unit 10 is equal to or greater than a predetermined value. Since the non-reflective section A4 not caused by a downward step detected due to the erroneous detection of the sensor unit 10 does not occur due to the movement of the sensor unit 10, it is possible to determine whether the non-reflective section A4 is not caused by a downward step by comparing the reception strength of the reflected wave before and after the movement of the sensor unit 10.

According to the distance measuring device 100 of the fourth embodiment described above, it is possible to determine whether the sensor unit 10 has detected an erroneous detection by comparing the reception strength of the reflected wave before and after the sensor unit 10 moves.

E. Fifth embodiment:
The fifth embodiment differs from the first embodiment in that the calculation unit 20 determines whether or not the step is a downward step. Since the configuration of the distance measuring device 100 of the fifth embodiment is the same as the configuration of the distance measuring device 100 of the first embodiment, the description of the configuration of the distance measuring device 100 is omitted.

As shown in FIG. 8, when there is a recess 304 between the first road surface 301 and the second road surface 302, the calculation unit 20 determines that the recess 304 is a downward step 303 if a predetermined condition in the positional relationship between the sensor unit 10 and the recess 304 is satisfied. The predetermined condition is, for example, that the linear distance Rl from the sensor unit 10 to the position Px of the bottom surface of the recess 304 passing through the upper end Pt of the recess 304 that contacts the first road surface 301 is shorter than the linear distance xu from the sensor unit 10 to the upper end Pt2 of the recess 304 that contacts the second road surface 302, and that the linear distance Rl is shorter than the linear distance xl from the sensor unit 10 to the lower end Pb of the recess 304 that faces the upper end Pt2.

According to the distance measuring device 100 of the fifth embodiment described above, the calculation unit 20 determines that the recess 304 is a downward step 303 when a predetermined condition is satisfied. Therefore, an extremely narrow and deep recess 304 can be excluded from the calculation of the step height ht.

F. Other embodiments:
(F1) In the above-described embodiment, the distance measuring device 100 includes the sensor unit 10, the calculation unit 20, and the output unit 30. Instead of this, the distance measuring device 100 may be configured to include only the sensor unit 10 and the calculation unit 20.

(F2) In the above-described embodiment, the sensor unit 10 may be a directional sensor. Compared to a non-directional sensor, it is possible to suppress reflected waves from the road surface that exist in an equidistant circle, and therefore it is possible to detect non-reflective sections with greater accuracy. The sensor unit 10 may also be a phased array in which multiple MEMS (Micro Electro Mechanical System) devices are arranged. The sensor unit 10 may have, for example, a PMUT (Piezoelectric Micromachined Ultrasonic Transducers) in which the emission unit 11 and the receiving unit 12 are integrated, or may have a microphone array as the receiving unit 12.

(F3) In the above-described embodiment, the calculation unit 20 calculates the step height ht based on the first distance Ln measured by the sensor unit 10 and the straight-line distance Ru, the straight-line distance hs, etc. Without being limited to this, the calculation unit 20 may calculate the step height ht based on the first distance Ln and the straight-line distance Ru, the straight-line distance hs, etc. measured by other sensors. In addition, the calculation unit 20 calculates the distance d1 obtained by subtracting the distance d2 from the distance d3 measured by the sensor unit 10 as the first distance Ln, but the first distance Ln may be obtained using the distances measured by other sensors.

(F4) In the above-described embodiment, the calculation unit 20 may correct the distance measured by the sensor unit 10 using at least one of the measured values of the temperature and humidity. More specifically, the calculation unit 20 may correct the attenuation of sound waves caused by absorption by air as they propagate. The higher the temperature, the greater the attenuation of sound waves. Also, the higher the humidity, the greater the attenuation of sound waves as they propagate. According to this embodiment, the calculation unit 20 can accurately estimate the first distance Ln, and therefore can accurately calculate the step height ht. The calculation unit 20 corrects the reception intensity, for example, based on the fact that the reception intensity is proportional to the following formula (2).

T∝exp(-αx)…(2)
Here, α is the sound absorption coefficient, and x is the distance measured by the sensor unit 10. Note that it is preferable that the calculation unit 20 performs correction when the emission unit 11 emits sound waves or radio waves.

(F5) In the above-described embodiment, the calculation unit 20 may detect the non-reflective section A3 using a model that has learned the relationship between the reception intensity and the non-reflective section A3 by supervised machine learning. More specifically, the calculation unit 20 can use the model learned by supervised machine learning to output whether or not a position at each distance from the distance measuring device 100 is included in the first reflection section A1 or the second reflection section A2, and the start point S1 and end point E1 of the first reflection section A1 and the start point S1 and end point E1 of the second reflection section A2. For example, a support vector machine (SVM), a deep neural network (DNN), or a random forest can be used as the supervised machine learning.

(F6) In the above-mentioned embodiment, the calculation unit 20 stores the distance from the road surface to the sensor unit 10 measured in advance. Instead, the calculation unit 20 may determine the straight-line distance hs from the sensor unit 10 to the start point S1 of the first reflection section A1 as the height from the road surface to the sensor unit 10. In this case, it is preferable that the sensor unit 10 can measure the distance to the road surface directly below the sensor unit 10. "Directly below" refers to a position vertically lowered from the sensor unit 10 toward the road surface at ±5°. This makes it possible to calculate the step height ht using the straight-line distance hs acquired without using other sensors. Also. The calculation unit 20 may calculate the height from the road surface to the sensor unit 10 using the difference between the distance measured by the sensor unit 10 and the distance measured by an additional sensor unit that can perform the same function as the sensor unit 10 and is provided above the sensor unit 10. In this case, the additional sensor unit may be provided in the distance measuring device 100 or an external sensor device. The calculation unit 20 calculates the height from the road surface to the sensor unit 10, for example, using the following formula (3).

hs=Ru×(Rud−Ru)/D…(3)
Here, Rud is the linear distance from the additional sensor unit to the end point E1, and D is the vertical distance between the sensor unit 10 and the additional sensor.

(F7) In the above-described embodiment, the calculation unit 20 may calculate the step height ht based on Pythagoras' theorem or the principles of triangulation or trilateration. The calculation unit 20 may also calculate the step height ht using a model that has learned the positional relationship between the distance measuring device 100 and the non-reflective section A3 and the relationship with the first distance Ln by supervised machine learning.

(F8) In the first and second embodiments described above, the calculation unit 20 may correct the distance measured by the sensor unit 10 using the width of the reflected wave of the single emitted wave emitted by the emitter 11, which has been acquired in advance. More specifically, the calculation unit 20 corrects the distance using a value obtained by converting the width from the rising edge to the falling edge of the reflected wave of the single wave emitted by the emitter 11 into a distance. In this manner, the first distance Ln can be calculated with higher accuracy. The calculation unit 20 can correct the linear distance Ru by subtracting the width of the reflected wave from the distance d2. That is, the calculation unit 20 can estimate the first distance Ln, for example, using the following formula (4).

Ln=d3-d2+w1...(4)
Here, w1 is the width of the reflected wave.

(F9) In the second embodiment described above, the calculation unit 20 uses a value determined according to the distance from the distance measuring device 100 as the threshold value. However, this is not limited to the above, and the calculation unit 20 may use a constant threshold value regardless of the distance from the distance measuring device 100.

(F10) In the second embodiment described above, the calculation unit 20 may detect the non-reflective section A3c based on the maximum value P1 of the reception strength in a predetermined range. That is, the calculation unit 20 may detect the non-reflective section A3c based on the maximum value that is equal to or greater than the first threshold and equal to or less than the second threshold. The second threshold is greater than the first threshold. This makes it possible to detect the non-reflective section A3c even if an obstacle is present on the road surface.

(F11) In the third embodiment described above, the calculation unit 20 detects the non-reflective section A3c based on the maximum values P1 to P9 that are equal to or greater than the threshold value. Without being limited to this, the calculation unit 20 may detect the non-reflective section A3c based on all the maximum values in a graph showing the relationship between reception strength and distance. The calculation unit 20 may also detect the non-reflective section A3c based on the maximum value P1 in a predetermined range of reception strength. That is, the calculation unit 20 may detect the non-reflective section A3c based on the maximum value that is equal to or greater than the first threshold value and equal to or less than the second threshold value. The second threshold value is greater than the first threshold value. This makes it possible to detect the non-reflective section A3c even when an obstacle is present on the road surface.

(F12) In the third embodiment described above, the calculation unit 20 may detect the non-reflection section A3c based on a maximum value above a threshold in a graph obtained by differentiating a graph showing the relationship between reception strength and distance with respect to distance.

(F13) In the third embodiment described above, the calculation unit 20 detects the non-reflective section A3c based on the maximum value of a graph obtained by differentiating a graph showing the relationship between reception strength and distance with respect to distance. Alternatively, the calculation unit 20 may detect the non-reflective section A3c based on an intersection point with a function Fth in a graph showing the relationship between reception strength and distance. Also, the calculation unit 20 may detect the non-reflective section A3c based on an intersection point with a predetermined threshold value in a graph obtained by differentiating a graph showing the relationship between reception strength and distance with respect to distance.

(F14) In the fourth embodiment described above, the calculation unit 20 determines whether the sensor unit 10 has detected an erroneous detection by comparing the reception strength of the reflected wave before and after the sensor unit 10 moves. Alternatively, the calculation unit 20 may determine whether the sensor unit 10 has detected an erroneous detection by comparing the reception strength of the reflected wave of multiple sensor units 10.

The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features in the embodiments corresponding to the technical features in each form described in the Summary of the Invention column can be replaced or combined as appropriate to solve the above-described problems or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

10: sensor unit, 11: emission unit, 12: reception unit, 20: calculation unit, 30: output unit, 100: distance measuring device, 200: estimation device, 301: first road surface, 302: second road surface, 303: step, 304: recessed portion

Claims (13)

A distance measuring device (100),
a sensor unit (10) having an emission unit (11) that emits an emission wave and a receiving unit (12) that receives a reflected wave generated when the emission wave is reflected by a target, and capable of measuring a distance to an object present within a predetermined detection range in a forward and backward direction of the emission unit using the reflected wave;
A calculation unit (20) that calculates a step height, which is the height of a downward step on a road surface, using the distance measured by the sensor unit,
The calculation unit is
when a non-reflection interval exists between a first reflection interval of a wave reflected from a first road surface and a second reflection interval of a wave reflected from a second road surface, the second road surface being a road surface farther from the distance measuring device in the front-rear direction than the first reflection interval, the non-reflection interval is detected from the reception intensity of the reflected wave;
A distance measuring device that calculates the step height based on a positional relationship between the sensor unit and the non-reflective section and a first distance that is a straight-line distance from an end point of the first reflective section to a start point of the second reflective section. 2. A distance measuring device according to claim 1,
When the calculation unit represents the reception intensity on a graph with the vertical axis representing the reception intensity and the horizontal axis representing the distance from the sensor unit,
a position on the graph where the reception intensity rises to or above a threshold is detected as a start point of the first reflection interval, and a position on the graph where the reception intensity first falls to or below the threshold, the position being farther from the sensor unit than the start point of the first reflection interval, is detected as an end point of the first reflection interval;
A ranging device that detects a position on the graph farther from the sensor unit than the end point of the first reflection interval and where the receiving intensity first rises above the threshold as the start point of the second reflection interval, and detects a position on the graph farther from the sensor unit than the start point of the second reflection interval and where the receiving intensity first falls below the threshold as the end point of the second reflection interval. 3. A distance measuring device according to claim 2,
The calculation unit corrects the distance measured by the sensor unit using a width of the reflected wave acquired in advance. 2. A distance measuring device according to claim 1,
When the calculation unit represents the reception intensity on a graph with the vertical axis representing the reception intensity and the horizontal axis representing the distance from the sensor unit,
a distance measuring device which performs a process of determining a difference between a position on the horizontal axis of a first maximum value in the graph and a position on the horizontal axis of a second maximum value that is located at a distance farther from the sensor unit than the first maximum value and is adjacent to the first maximum value, the distance measuring device detects the position of the first maximum value as the end point of the first reflection interval, and detects the position of the second maximum value as the start point of the second reflection interval, among the first maximum value and second maximum value for which the difference first becomes equal to or greater than a predetermined threshold distance. 2. A distance measuring device according to claim 1,
A ranging device in which the calculation unit detects the start and end points of the first reflection interval and the start and end points of the second reflection interval using a model that learns the relationship between the reception strength and the non-reflection interval through supervised machine learning. A distance measuring device according to any one of claims 1 to 5,
A distance measuring device, wherein the calculation unit calculates the difference between the distance to the end point of the first reflection interval measured by the sensor unit and the distance to the start point of the second reflection interval measured by the sensor unit as the first distance. A distance measuring device according to any one of claims 1 to 6,
The calculation unit corrects the distance measured by the sensor unit using a measured value of at least one of air temperature and humidity. A distance measuring device according to any one of claims 1 to 7,
A distance measuring device in which the calculation unit calculates the step height using one or more of the straight-line distance from the sensor unit to the end point of the first reflection interval, the straight-line distance from the sensor unit to the start point of the second reflection interval, and the distance of the first reflection interval, the first distance, and the height from the road surface to the sensor unit. 9. A distance measuring device according to claim 8,
The sensor unit can measure a distance to a road surface directly below the sensor unit,
A distance measuring device in which the calculation unit determines the distance from the sensor unit to the start point of the first reflection interval to be the height from the road surface to the sensor unit. 9. The distance measuring device according to claim 8, further comprising:
an additional sensor unit that can perform the same function as the sensor unit and is provided above the sensor unit;
A distance measuring device, wherein the calculation unit calculates a height from the road surface to the sensor unit using a difference between the distance measured by the sensor unit and the distance measured by the additional sensor unit. A distance measuring device according to any one of claims 1 to 10,
The distance measuring device, wherein the emission unit emits a sound wave or an electric wave as the emitted wave. A road surface recognition method for calculating a step height, which is the height of a downward step on a road surface, comprising:
a step of acquiring a distance measured by a sensor unit having an emission unit that emits an emission wave and a receiving unit that receives a reflected wave generated when the emission wave is reflected by a target, the sensor unit being capable of measuring a distance to an object present within a predetermined detection range in a forward and backward direction of the emission unit using the reflected wave, and a reception intensity of the reflected wave;
a step of detecting a non-reflection section from a reception intensity of the reflected wave when a non-reflection section exists between a first reflection section caused by a reflected wave from a first road surface and a second reflection section caused by a reflected wave from a second road surface, the second road surface being a road surface farther from the sensor unit in the front-rear direction than the first reflection section;
and calculating the step height based on a positional relationship between the sensor unit and the non-reflective section and a first distance which is a straight-line distance from an end point of the first reflective section to a start point of the second reflective section. An estimation device (200) for estimating a step height, which is the height of a downward step on a road surface, comprising:
a calculation unit that calculates the step height using a distance measured by a sensor unit that has an emission unit that emits an emission wave and a receiving unit that receives a reflected wave generated when the emission wave is reflected by a target, and that can measure a distance to an object that exists in a predetermined detection range in a front-rear direction of the emission unit using the reflected wave;
and an output unit (30) that outputs the step height,
The calculation unit is
When a non-reflection interval exists between a first reflection interval due to a reflected wave from a first road surface and a second reflection interval due to a reflected wave from a second road surface, the second road surface being a road surface farther from the sensor unit in the front-rear direction than the first reflection interval, the non-reflection interval is detected from the reception intensity of the reflected wave,
An estimation device that calculates the step height based on a positional relationship between the sensor unit and the non-reflective section and a first distance that is a straight-line distance from an end point of the first reflective section to a start point of the second reflective section.

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