JP2020180796A - Obstacle detector and obstacle detection method - Google Patents

Abstract

To provide an obstacle detector and an obstacle detection method with which it is possible to determine whether the detected obstacle is a near-distance or a far-distance obstacle.SOLUTION: An ultrasonic detector comprises an ultrasonic sensor, a transmission command unit for causing an ultrasonic wave to be repeatedly transmitted by the ultrasonic sensor, and a detection unit for detecting an obstacle from the result of having received a reflected wave by the ultrasonic sensor. The transmission command unit causes an ultrasonic wave to be transmitted at a first transmission interval Ta by the ultrasonic sensor and causes an ultrasonic wave to be transmitted at a second transmission interval Tb different from the first transmission interval Ta by the ultrasonic sensor when the detection unit detects an obstacle as a reflected wave is received by the ultrasonic sensor. The ultrasonic detector includes a determination unit for calculating a time for determination which is a difference between the receive time of a reflected wave for detection which is a reflected wave used for detecting an obstacle and the receive time of a reflected wave for determination which is a reflected wave received after the reflected wave for detection, and determining whether the obstacle is a near-distance or a far-distance obstacle on the basis of the result of comparison of the time for determination with a threshold.SELECTED DRAWING: Figure 7

Description

The present invention relates to an obstacle detection device and an obstacle detection method.

Patent Document 1 describes an obstacle detection device that detects an obstacle by ultrasonic waves. The obstacle detection device includes an ultrasonic sensor that transmits ultrasonic waves and receives the reflected waves reflected by the obstacles, a transmission command unit that controls the transmission of ultrasonic waves by the ultrasonic sensors, and reflected waves by the ultrasonic sensor. It is provided with a detection unit that detects obstacles from the reception result of. When the detection unit detects an obstacle, the ultrasonic sensor measures the time from when the ultrasonic sensor transmits ultrasonic waves to when the ultrasonic sensor receives the reflected wave reflected by the obstacle. You can see the distance from to the obstacle. The longer the distance from the ultrasonic sensor to the obstacle, the longer the time from when the ultrasonic sensor transmits ultrasonic waves to when the ultrasonic sensor receives the reflected wave reflected by the obstacle.

By the way, in such an obstacle detection device, the transmission command unit repeatedly detects an obstacle by causing an ultrasonic sensor to repeatedly transmit ultrasonic waves. At this time, if the ultrasonic wave transmission interval by the ultrasonic sensor is shortened, the obstacle detection interval is also shortened, so that the obstacle can be detected at an early stage.

Japanese Unexamined Patent Publication No. 2014-169927

On the other hand, if the ultrasonic wave transmission interval is shortened, the time required from the ultrasonic wave transmission to the reception of the reflected wave may be longer than the ultrasonic wave transmission interval depending on the distance from the ultrasonic sensor to the obstacle. .. A short-range obstacle is an obstacle in which the time required from the transmission of ultrasonic waves to the reception of reflected waves is shorter than the transmission interval of ultrasonic waves, and the time required from the transmission of ultrasonic waves to the reception of reflected waves is ultrasonic waves. Obstacles that exceed the transmission interval of are defined as long-distance obstacles.

For example, as shown in FIG. 12A, the ultrasonic sensor of the obstacle detection device transmits the first ultrasonic wave Us1 at time t0, and the second ultrasonic wave Us2 at time t1 after the time Tp has elapsed from time t0. To send. That is, the transmission interval of ultrasonic waves is Tp. Examples 1 and 2 of obstacle detection using this obstacle detection device are shown in FIGS. 12 (b) and 12 (c).

In the detection example 1 shown in FIG. 12B, an obstacle 101 that was not present at the time t0 appears at the time t1. The obstacle 101 is a short-range obstacle located at a distance L1 from the ultrasonic sensor 100. In this case, the second ultrasonic wave Us2 transmitted at time t1 is reflected by the obstacle 101, and the ultrasonic sensor 100 receives the second reflected wave Ur2 of the second ultrasonic wave Us2. The time Tq required from the transmission of the second ultrasonic wave Us2 by the ultrasonic sensor 100 to the reception of the second reflected wave Ur2 is shorter than the transmission interval Tp of the ultrasonic waves. As shown in FIG. 12A, the ultrasonic sensor 100 receives the second reflected wave Ur2 at the time t2 after the time Tq elapses from the time t1 when the second ultrasonic wave Us2 is transmitted.

In the detection example 2 shown in FIG. 12 (c), the obstacle 102 exists at time t0. The obstacle 102 is a long-distance obstacle located at a distance L2 longer than the distance L1 from the ultrasonic sensor 100. In this case, the first ultrasonic wave Us1 transmitted at time t0 is reflected by the obstacle 102, and the ultrasonic sensor 100 receives the first reflected wave Ur1 of the first ultrasonic wave Us1. The time Tr required from the transmission of the first ultrasonic wave Us1 by the ultrasonic sensor 100 to the reception of the first reflected wave Ur1 is longer than the ultrasonic wave transmission interval Tp. As shown in FIG. 12A, the ultrasonic sensor 100 receives the first reflected wave Ur1 at the time t2 after the time Tr has elapsed from the time t0 when the first ultrasonic wave Us1 was transmitted. That is, the ultrasonic sensor 100 receives the first reflected wave Ur1 after transmitting the second ultrasonic wave Us2. Note that FIG. 12A shows a case where the time Tr coincides with Tp + Tq, which is the sum of the time Tp and the time Tq.

As described above, in the detection example 1 and the detection example 2, the ultrasonic sensor 100 receives the reflected wave at the same time t2 even though the distances from the ultrasonic sensor 100 to the obstacles 101 and 102 are different. However, from the timing of transmitting and receiving the ultrasonic waves shown in FIG. 12A, it is not known whether the reflected wave received by the ultrasonic sensor 100 at time t2 is the first reflected wave Ur1 or the second reflected wave Ur2. Therefore, it is not possible to determine whether the ultrasonic waves are reflected by a short-range obstacle or a long-range obstacle. As a result, it cannot be determined whether the detected obstacles 101 and 102 are short-distance obstacles or long-distance obstacles.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an obstacle detection device and an obstacle detection method capable of determining whether a detected obstacle is a short-distance obstacle or a long-distance obstacle. To do.

Obstacle detection devices for solving the above problems include an ultrasonic sensor that transmits ultrasonic waves and receives reflected waves reflected by the obstacle, and a transmission command unit that causes the ultrasonic sensor to repeatedly transmit ultrasonic waves. An obstacle detection device including a detection unit that detects the obstacle from the reception result of the reflected wave by the ultrasonic sensor, and the transmission command unit superimposes on the ultrasonic sensor at the first transmission interval. When the detection unit detects an obstacle by transmitting an ultrasonic wave and receiving the reflected wave by the ultrasonic sensor, the ultrasonic sensor is made to transmit ultrasonic waves at a second transmission interval different from the first transmission interval. , Judgment that is the difference between the reception time of the detection reflected wave, which is the reflected wave used for detecting the obstacle, and the reception time of the determination reflected wave, which is the reflected wave received after the detection reflected wave. The gist is to include a determination unit for calculating the usage time and determining whether the obstacle is a short-range obstacle or a long-range obstacle based on the comparison result between the determination time and the threshold value.

The reflected waves received by the ultrasonic sensor include the case where the ultrasonic waves transmitted immediately before the reception of the reflected waves are reflected by a short-range obstacle and the ultrasonic waves transmitted immediately before the reception of the reflected waves. It is considered that the ultrasonic waves transmitted to the above are reflected by a long-distance obstacle. In the former case, the timing of receiving the reflected wave is determined by the timing of transmitting the ultrasonic wave immediately before the reception of the reflected wave, and in the latter case, the timing of receiving the reflected wave is determined by the timing of the ultrasonic wave immediately before the reception of the reflected wave. It depends on the timing of ultrasonic transmission that occurs before transmission. Therefore, if the ultrasonic wave transmission interval is different between the first transmission interval and the second transmission interval, the determination time differs between the former case and the latter case. Therefore, by comparing the determination time with the threshold value, it is possible to determine whether the obstacle detected from the comparison result is a short-distance obstacle or a long-distance obstacle.

Further, with respect to the obstacle detection device, the reception time of the detection reflected wave is the difference between the reception time of the detection reflected wave and the ultrasonic transmission time performed immediately before the reception of the detection reflected wave. The reception time of the determination reflected wave is the difference between the reception time of the determination reflected wave and the transmission time of the ultrasonic wave performed immediately before the reception of the determination reflected wave.

Further, it is preferable to change the threshold value of the obstacle detection device according to the speed of the moving body on which the obstacle detection device is mounted.
The reception time of the reflected wave depends on the distance from the obstacle to the ultrasonic sensor. Therefore, when a moving body equipped with an obstacle detection device detects an obstacle while moving, the distance from the obstacle to the ultrasonic sensor changes, so that the reception time of the reflected wave changes, and further, the determination is made. Usage time may change. Therefore, by changing the threshold value according to the speed of the moving body, it is possible to determine whether the detected obstacle is a short-distance obstacle or a long-distance obstacle even while the moving body is moving.

The obstacle detection method for solving the above-mentioned problems is an obstacle detection method in which the obstacle is detected from the reception result of the reflected wave by the ultrasonic sensor that transmits ultrasonic waves and receives the reflected wave reflected by the obstacle. The method is a step of transmitting ultrasonic waves from the ultrasonic sensor at the first transmission interval and a second transmission interval different from the first transmission interval when the ultrasonic sensor receives the reflected wave. The step of transmitting ultrasonic waves from the ultrasonic sensor, the step of acquiring the reception time of the detected reflected wave which is the reflected wave used for detecting the obstacle, and the step of receiving the reflected wave after the detection reflected wave. The step of acquiring the reception time of the reflected wave for determination which is the reflected wave, the step of calculating the determination time which is the difference between the reception time of the reflected wave for detection and the reception time of the reflected wave for determination, and the determination. The gist is to include a step of determining whether the obstacle is a short-range obstacle or a long-range obstacle based on the comparison result between the usage time and the threshold value.

The reflected waves received by the ultrasonic sensor include the case where the ultrasonic waves transmitted immediately before the reception of the reflected waves are reflected by a short-range obstacle and the ultrasonic waves transmitted immediately before the reception of the reflected waves. It is considered that the ultrasonic waves transmitted to the above are reflected by a long-distance obstacle. In the former case, the timing of receiving the reflected wave is determined by the timing of transmitting the ultrasonic wave immediately before the reception of the reflected wave, and in the latter case, the timing of receiving the reflected wave is determined by the timing of the ultrasonic wave immediately before the reception of the reflected wave. It depends on the timing of ultrasonic transmission that occurs before transmission. Therefore, if the ultrasonic wave transmission interval is different between the first transmission interval and the second transmission interval, the determination time differs between the former case and the latter case. Therefore, by comparing the determination time with the threshold value, it is possible to determine whether the obstacle detected from the comparison result is a short-distance obstacle or a long-distance obstacle.

According to the present invention, it is possible to determine whether the detected obstacle is a short-distance obstacle or a long-distance obstacle.

Schematic side view of a forklift equipped with an obstacle detection device. The block diagram which shows the structure of a forklift. The block diagram which shows the structure of the obstacle detection apparatus. The schematic diagram which shows the detection range of an obstacle. A flowchart showing an obstacle detection method. (A) is a schematic diagram showing the arrangement of the ultrasonic sensor and obstacles in Example 1-1, and (b) is a diagram showing the transmission / reception timing of ultrasonic waves in Example 1-1. (A) is a schematic view showing the arrangement of the ultrasonic sensor and obstacles in Example 1-2, and (b) is a diagram showing the transmission / reception timing of ultrasonic waves in Example 1-2. (A) is a schematic diagram showing the arrangement of the ultrasonic sensor and obstacles in Example 2-1 and (b) is a diagram showing the transmission / reception timing of ultrasonic waves in Example 2-1. (A) is a schematic diagram showing the arrangement of the ultrasonic sensor and obstacles in Example 2-2, and (b) is a diagram showing the transmission / reception timing of ultrasonic waves in Example 2-2. (A) and (b) are diagrams showing the transmission / reception timing of ultrasonic waves in another example. (A) and (b) are diagrams showing the transmission / reception timing of ultrasonic waves in another example. (A) is a diagram showing the transmission / reception timing of ultrasonic waves, and (b) and (c) are schematic views showing the arrangement of ultrasonic sensors and obstacles.

(First Embodiment)
Hereinafter, the first embodiment in which the obstacle detection device and the obstacle detection method are embodied will be described with reference to FIGS. 1 to 7.

As shown in FIG. 1, the forklift 10 as a moving body includes a vehicle body 11, a cargo handling device 12 provided in front of the vehicle body 11, and a counterweight 13 provided behind the vehicle body 11. The forklift 10 of the present embodiment is a forklift that is operated by a passenger.

As shown in FIG. 2, the forklift 10 is a key switch that switches between a main controller 17, a cargo handling mechanism 14 that operates a cargo handling device 12, a drive mechanism 15 that runs the forklift 10, and a start state and a stop state of the forklift 10. It is provided with 16.

The main controller 17 includes a CPU 18 and a memory 19. A program or the like for operating the forklift 10 is stored in the memory 19. When the forklift 10 is activated by the key switch 16, the main controller 17 controls the drive mechanism 15 and the cargo handling mechanism 14 to cause the forklift 10 to perform cargo handling operations and traveling operations. On the other hand, when the forklift 10 is stopped by the key switch 16, the main controller 17 does not allow the forklift 10 to perform a cargo handling operation or a traveling operation.

The forklift 10 is equipped with an obstacle detection device 20 that detects obstacles by ultrasonic waves. The obstacle detection device 20 includes an ultrasonic sensor 21. The ultrasonic sensor 21 is a transmission / reception type that performs both transmission and reception of ultrasonic waves with one element.

The ultrasonic sensor 21 includes a piezoelectric vibrator (not shown). The piezoelectric vibrator can convert an electric signal into a vibration and can also convert a vibration into an electric signal. The piezoelectric vibrator vibrates when a transmission signal is input from the transmission command unit 31, which will be described later. When the piezoelectric vibrator vibrates, ultrasonic waves are transmitted from the ultrasonic sensor 21. When there is an obstacle ahead of the transmission direction of the ultrasonic wave, the ultrasonic wave becomes a reflected wave that hits the obstacle and is reflected. The piezoelectric vibrator vibrates when it receives the reflected wave, and outputs a received signal indicating that the reflected wave has been received to the detection unit 32 described later. That is, the ultrasonic sensor 21 has a transmission function for transmitting ultrasonic waves and a reception function for receiving reflected waves. In the ultrasonic sensor 21 of the present embodiment, the threshold value of the reception intensity of the reflected wave for determining whether or not to transmit the received signal to the detection unit 32 is set to a constant value. Further, since the piezoelectric vibrator of the present embodiment is a transmission / reception type, the reflected wave cannot be received while the ultrasonic sensor 21 transmits ultrasonic waves. Further, since the number of ultrasonic sensors 21 included in the obstacle detection device 20 of the present embodiment is "1", the transmission of ultrasonic waves and the reception of reflected waves are performed by the same ultrasonic sensors 21.

As shown in FIGS. 1 and 4, the ultrasonic sensor 21 is attached to the counterweight 13 and transmits ultrasonic waves to the rear of the vehicle body 11. Therefore, the obstacle detected by the obstacle detection device 20 is an obstacle existing behind the forklift 10. The obstacle detection device 20 of the present embodiment aims to detect an obstacle within a range of 3.0 m behind the forklift 10. Therefore, the detection target range A (see FIG. 4) by the obstacle detection device 20 in the present embodiment is defined as a range having a margin with respect to the range in which the obstacle is actually detected, from the ultrasonic sensor 21 to the forklift 10. It is set within a range of 3.4 m behind. Hereinafter, an obstacle within the detection target range A will be referred to as a short-distance obstacle, and an obstacle outside the detection target range A will be referred to as a long-distance obstacle.

As shown in FIG. 3, the obstacle detection device 20 includes a control ECU 30. The control ECU 30 is an electronic control unit: an electronic control unit including a CPU and a storage unit including a RAM and a ROM. Various programs for controlling the obstacle detection device 20 are stored in the storage unit. The control ECU 30 may be provided with dedicated hardware that executes at least a part of various processes, for example, an integrated circuit for a specific application: ASIC. The control ECU 30 may be configured as one or more processors operating according to a computer program, one or more dedicated hardware circuits such as an ASIC, or a circuit including a combination thereof. The processor includes a CPU and a memory such as RAM and ROM. The memory stores a program code or a command configured to cause the CPU to execute the process. Memory, or computer-readable medium, includes anything that can be accessed by a general purpose or dedicated computer. The control ECU 30 is connected to the main controller 17 so as to be able to communicate with each other. In this embodiment, the control ECU 30 is formed separately from the main controller 17.

The control ECU 30 includes a transmission command unit 31 connected to the ultrasonic sensor 21. The transmission command unit 31 outputs a transmission signal to the ultrasonic sensor 21 to cause the ultrasonic sensor 21 to transmit ultrasonic waves. The transmission command unit 31 repeatedly outputs a transmission signal while the forklift 10 is activated by the key switch 16. The ultrasonic sensor 21 transmits ultrasonic waves each time a transmission signal from the transmission command unit 31 is input. Therefore, the output interval of the transmission signal by the transmission command unit 31 is the same as the transmission interval of the ultrasonic waves by the ultrasonic sensor 21.

The control ECU 30 includes a detection unit 32 connected to the ultrasonic sensor 21. When the ultrasonic sensor 21 receives the reflected wave, the received signal is input from the ultrasonic sensor 21 to the detection unit 32. The detection unit 32 detects the presence or absence of an obstacle from the reception result of the reflected wave by the ultrasonic sensor 21. The detection unit 32 detects that there is an obstacle behind the forklift 10 by inputting a received signal of the reflected wave from the ultrasonic sensor 21.

The control ECU 30 includes a measurement unit 33 connected to the transmission command unit 31 and the detection unit 32, and a determination unit 34 connected to the measurement unit 33. The measuring unit 33 measures the time required from the transmission of the ultrasonic wave to the reception of the reflected wave (hereinafter, referred to as the reception time of the reflected wave). The determination unit 34 determines whether the detected obstacle is a short-distance obstacle or a long-distance obstacle. Further, the determination unit 34 outputs the determination result to the main controller 17. When the main controller 17 determines that the obstacle is a short-distance obstacle, the main controller 17 does not cause the forklift 10 to perform a traveling operation. When the main controller 17 determines that the obstacle is a long-distance obstacle, the main controller 17 causes the forklift 10 to perform a traveling operation.

The obstacle detection device 20 detects the presence or absence of an obstacle, and when the detection unit 32 detects an obstacle, determines whether the detected obstacle is a short-distance obstacle or a long-distance obstacle. The obstacle detection device 20 is designed to detect the presence or absence of an obstacle in the initial state, and when the determination unit 34 finishes determining whether the obstacle is a short-distance obstacle or a long-distance obstacle, the obstacle is detected. Resume detection of the presence or absence of objects. When the obstacle detection device 20 detects the presence or absence of an obstacle, the transmission command unit 31 causes the ultrasonic sensor 21 to transmit ultrasonic waves at the first transmission interval Ta. Further, when determining whether the obstacle detected by the obstacle detection device 20 is a short-distance obstacle or a long-distance obstacle, the transmission command unit 31 superimposes on the ultrasonic sensor 21 at the second transmission interval Tb. Send ultrasonic waves. As will be described later, the first transmission interval Ta is set based on the obstacle detection target range A, and the second transmission interval Tb is set to be different from the first transmission interval Ta.

As shown in FIG. 4, the distance L [m] from the ultrasonic sensor 21 to the obstacle X is L = V × t / 2 from the speed of sound V [m / sec] and the reception time t [sec] of the reflected wave. It is represented by. Therefore, the longer the distance L [m] from the ultrasonic sensor 21 to the obstacle X, the longer the reception time t [sec] of the reflected wave. As described above, in the present embodiment, the range within 3.4 m behind the forklift 10 from the ultrasonic sensor 21 is set as the detection target range A by the obstacle detection device 20. Therefore, for example, when the sound velocity V is 340 [m / sec], if the ultrasonic sensor 21 does not receive the reflected wave within about 20 ms after transmitting the ultrasonic wave, it is within the detection target range A at a short distance. It can be said that there are no obstacles.

The detection target range A is a range set for convenience in order to detect an obstacle to the traveling operation of the forklift 10. The ultrasonic waves transmitted from the ultrasonic sensor 21 actually reach further behind the forklift 10 which is the detection target range A, 3.4 m behind. The ultrasonic waves transmitted from the ultrasonic sensor 21 of the present embodiment shall reach 10.0 m behind the forklift 10. Therefore, the range within 10.0 m behind the forklift 10 from the ultrasonic sensor 21 is the detectable range B (see FIG. 4) by the obstacle detection device 20. The ultrasonic wave is reflected not only by hitting a short-distance obstacle within the detection target range A, but also by hitting a long-distance obstacle outside the detection target range A and within the detectable range B. The ultrasonic sensor 21 receives the reflected wave reflected by the obstacle regardless of whether it is inside or outside the detection target range A. Therefore, the ultrasonic sensor 21 may receive the reflected wave reflected by a long-distance obstacle outside the detection target range A between about 20 to 58.8 ms after transmitting the ultrasonic wave. is there.

Based on this, it is conceivable to set the ultrasonic wave transmission interval to, for example, 60 ms, but due to the nature of detecting by utilizing the fact that the transmitted ultrasonic wave hits an obstacle and is reflected, the ultrasonic wave transmission interval is lengthened. The longer it takes to detect an obstacle. Conversely, the shorter the ultrasonic transmission interval, the shorter the time required to detect an obstacle, and the presence or absence of an obstacle can be detected at an early stage. In the present embodiment, the first transmission interval Ta is set to 20 ms in order to detect an obstacle at an early stage while enabling detection of a short-distance obstacle within the detection target range A. When the obstacle is a short-distance obstacle, the reception time of the reflected wave is the first transmission interval Ta: 20 ms or less, and when the obstacle is a long-distance obstacle, the reception time of the reflected wave is the first transmission interval Ta: Ta. : Longer than 20 ms. When the obstacle detection device 20 detects the presence or absence of an obstacle, the transmission command unit 31 outputs a transmission signal to the ultrasonic sensor 21 every 20 ms, and the ultrasonic sensor 21 transmits ultrasonic waves every 20 ms.

Next, an obstacle detection method will be described.
When the forklift 10 is activated by the key switch 16, the operation of the obstacle detection device 20 is started. The obstacle detection device 20 first detects the presence or absence of an obstacle.

Specifically, as shown in FIG. 5, ultrasonic waves are transmitted from the ultrasonic sensor 21 at the first transmission interval Ta (step S10). When the ultrasonic sensor 21 does not receive the reflected wave (NO in step S11), the detection unit 32 detects that there is no obstacle in the detectable range B behind the forklift 10 (step S12). When the ultrasonic sensor 21 receives the reflected wave (YES in step S11), the detection unit 32 detects that there is an obstacle in the detectable range B behind the forklift 10 (step S13). The reflected wave received by the ultrasonic sensor 21 in step S11 is used as the detected reflected wave. The detection reflected wave is a reflected wave used for detecting an obstacle.

Next, the obstacle detection device 20 determines whether the detected obstacle is a short-distance obstacle or a long-distance obstacle.
Specifically, the measuring unit 33 measures the first detection time Tc. The first detection time Tc is the difference between the reception time of the reflected reflected wave for detection and the transmission time of the ultrasonic wave performed immediately before the reception of the reflected reflected wave for detection. In other words, it is the time required to go back from the time when the ultrasonic sensor 21 receives the reflected wave for detection to the time when the ultrasonic sensor 21 transmits the ultrasonic wave immediately before receiving the reflected wave for detection. The measuring unit 33 transmits the measured first detection time Tc to the transmission command unit 31 and the determination unit 34. The transmission command unit 31 sets the second transmission interval Tb based on the first transmission interval Ta and the first detection time Tc. The second transmission interval Tb is set to be different from the first transmission interval Ta and different from Ta + Tc, which is the sum of the first transmission interval Ta and the first detection time Tc.

Ultrasonic waves are transmitted twice from the ultrasonic sensor 21 at the second transmission interval Tb (step S14). The ultrasonic waves transmitted at the second transmission interval Tb hit an obstacle and are reflected. Therefore, the ultrasonic sensor 21 receives the reflected wave of the ultrasonic wave transmitted at the second transmission interval Tb. The reflected wave received by the ultrasonic sensor 21 after the detected reflected wave is defined as the determination reflected wave. Further, among the reflected waves for determination, the reflected wave received for the first time after receiving the reflected wave for detection is used as the reflected wave for first determination, and the reflected wave received after receiving the reflected wave for first determination is used for the second determination. Let it be a reflected wave.

The measuring unit 33 measures the second detection time Td and the third detection time Te. The second detection time Td is the difference between the reception time of the reflected wave for first determination and the transmission time of ultrasonic waves performed immediately before the reception of the reflected wave for first determination. In other words, the second detection time Td goes back from the time when the ultrasonic sensor 21 receives the first determination reflected wave to the time when the ultrasonic sensor 21 transmits the ultrasonic wave immediately before the reception of the first determination reflected wave. It is the time required for. The third detection time Te is the difference between the reception time of the reflected wave for the second determination and the transmission time of the ultrasonic wave performed immediately before the reception of the reflected wave for the second determination. In other words, the third detection time Te goes back from the time when the ultrasonic sensor 21 receives the reflected wave for the second determination to the time when the ultrasonic sensor 21 transmits the ultrasonic wave immediately before the reception of the reflected wave for the second determination. It is the time required for. The measuring unit 33 outputs the measured second detection time Td and third detection time Te to the determination unit 34.

The determination unit 34 is a first reception time T1 which is a reception time of the reflected wave for detection, a second reception time T2 which is a reception time of the reflected wave for the first determination, and a reception time of the reflected wave for the second determination. Acquire the third reception time T3 (step S15). In the present embodiment, the determination unit 34 acquires the first detection time Tc input from the measurement unit 33 as the first reception time T1. The determination unit 34 acquires the second detection time Td input from the measurement unit 33 as the second reception time T2. The determination unit 34 acquires the third detection time Te input from the measurement unit 33 as the third reception time T3.

The determination unit 34 calculates the first determination time ΔT1 and the second determination time ΔT2 as the determination time (step S16). The first determination time ΔT1 is the difference between the first reception time T1 and the second reception time T2 | T1-T2 |, and the second determination time ΔT2 is the first reception time T1 and the third reception time T3. Difference | T1-T3 | The determination unit 34 compares the first determination time ΔT1 and the second determination time ΔT2 with the preset threshold value ΔTx (step S17). The threshold value ΔTx is a preset time for making it possible to distinguish whether the obstacle is a short-distance obstacle or a long-distance obstacle from the calculation result of the determination time. When both the first determination time ΔT1 and the second determination time ΔT2 are equal to or less than the threshold value ΔTx (YES in step S17), the determination unit 34 determines that the obstacle is a short-distance obstacle (step S18). When at least one of the first determination time ΔT1 and the second determination time ΔT2 is larger than the threshold value ΔTx (NO in step S17), the determination unit 34 determines that the obstacle is a long-distance obstacle (step S19). ..

The obstacle detection device 20 repeats the flow shown in FIG. 5 until the forklift 10 is stopped by the key switch 16. That is, when it is detected that there is no obstacle in step S12, when it is determined that the obstacle is a short-distance obstacle in step S18, or when it is determined that the obstacle is a long-distance obstacle in step S19. Transmits ultrasonic waves from the ultrasonic sensor 21 at the first transmission interval Ta.

Hereinafter, specific examples of detecting obstacles will be described in detail with reference to Examples 1-1 and 1-2. In Examples 1-1 and 1-2, it is assumed that the forklift 10 does not run and is stopped while the obstacle is detected. The threshold value ΔTx is set to 1 ms.

In Example 1-1, as shown in FIG. 6A, consider a case where an obstacle X11 that did not exist behind the forklift 10 at time 0s appears behind the forklift 10 at time 20ms. The obstacle X11 is a short-distance obstacle existing 1.02 m behind the ultrasonic sensor 21 within the detection target range A. The shape of the obstacle X11 is shown in a simplified manner. Further, it is assumed that the obstacle X11 does not move after appearing at the time of 20 ms.

As shown in FIG. 6B, the ultrasonic sensor 21 transmits ultrasonic waves at the first transmission interval Ta (step S10). The time when the first ultrasonic wave S1 is transmitted from the ultrasonic sensor 21 is 0 s. In Example 1-1, since the obstacle X11 does not exist in the detection target range A at time 0s, the first ultrasonic wave S1 is attenuated without hitting the obstacle X11. Therefore, the ultrasonic sensor 21 does not receive the reflected wave from the time 0s to the elapse of 20ms. The ultrasonic sensor 21 transmits the second ultrasonic wave S2 at a time 20 ms 20 ms after the time 0 s when the first ultrasonic wave S1 is transmitted according to the first transmission interval Ta. At time 20 ms, the obstacle X11 exists within the detection target range A. Therefore, the second ultrasonic wave S2 is reflected by hitting the obstacle X11. The ultrasonic sensor 21 receives the reflected wave R2 of the second ultrasonic wave S2 (YES in step S11). Since the obstacle X11 exists 1.02 m behind the ultrasonic sensor 21, the time required from the transmission of the second ultrasonic wave S2 to the reception of the reflected wave R2 is 6 ms. Therefore, the time when the ultrasonic sensor 21 receives the reflected wave R2 is 26 ms after 6 ms from the time when the second ultrasonic wave S2 is transmitted. The detection unit 32 detects that the obstacle X11 is within the detectable range B behind the forklift 10 (step S13). The reflected wave R2 is a reflected wave for detection, and the second ultrasonic wave S2 is an ultrasonic wave transmitted immediately before receiving the reflected wave R2.

In Example 1-2, as shown in FIG. 7A, consider the case where the obstacle X12 exists behind the forklift 10 at time 0s. The obstacle X12 is a long-distance obstacle existing 4.41 m behind the ultrasonic sensor 21 which is outside the detection target range A and within the detectable range B. The shape of the obstacle X12 is shown in a simplified form. Further, it is assumed that the obstacle X12 does not move when the obstacle detection device 20 detects the obstacle.

As shown in FIG. 7B, the ultrasonic sensor 21 transmits ultrasonic waves at the first transmission interval Ta (step S10). The time when the first ultrasonic wave S1 is transmitted from the ultrasonic sensor 21 is 0 s. In Example 1-2, the obstacle X12 exists within the detectable range B at time 0s. Therefore, the first ultrasonic wave S1 is reflected by hitting the obstacle X12. The ultrasonic sensor 21 receives the reflected wave R10 of the first ultrasonic wave S1 (YES in step S11). Since the obstacle X12 exists 4.41 m behind the ultrasonic sensor 21, the time required from the transmission of the first ultrasonic wave S1 to the reception of the reflected wave R10 is 26 ms. Therefore, the time when the ultrasonic sensor 21 receives the reflected wave R10 is 26 ms after the time 0 s when the first ultrasonic wave S1 is transmitted. The ultrasonic sensor 21 does not receive the reflected wave between the time 0s and the elapse of 20ms. The ultrasonic sensor 21 transmits the second ultrasonic wave S2 at a time 20 ms 20 ms after the time 0 s when the first ultrasonic wave S1 is transmitted according to the first transmission interval Ta. The detection unit 32 detects that the obstacle X12 is within the detectable range B behind the forklift 10 (step S13). The reflected wave R10 is a reflected wave for detection, and the second ultrasonic wave S2 is an ultrasonic wave transmitted immediately before receiving the reflected wave R10.

In Examples 1-1 and 1-2, the measuring unit 33 measures the first detection time Tc. The first detection time Tc is the time required from the transmission of the second ultrasonic wave S2 to the reception of the reflected waves R2 and R10, which is 6 ms. The measuring unit 33 outputs the measured first detection time Tc: 6 ms to the transmission command unit 31 and the determination unit 34. The transmission command unit 31 sets the second transmission interval Tb. The first transmission interval Ta is 20 ms, and the first detection time Tc is 6 ms. Therefore, the second transmission interval Tb is set to be different from 20 ms and different from 26 ms. In Examples 1-1 and 1-2, the second transmission interval Tb is set to, for example, 22 ms.

The ultrasonic sensor 21 transmits ultrasonic waves twice at a second transmission interval Tb: 22 ms (step S14). That is, the ultrasonic sensor 21 transmits the third ultrasonic wave S3 at a time 42 ms 22 ms after the time 20 ms when the second ultrasonic wave S2 was transmitted. Further, the ultrasonic sensor 21 transmits the fourth ultrasonic wave S4 at a time 64 ms 22 ms after the time 42 ms when the third ultrasonic wave S3 was transmitted.

In Example 1-1, the third ultrasonic wave S3 hits the obstacle X11 and is reflected. The ultrasonic sensor 21 receives the reflected wave R3 of the third ultrasonic wave S3, and the detection unit 32 again detects that the obstacle X11 is behind the forklift 10. At this time, the time required from the transmission of the third ultrasonic wave S3 to the reception of the reflected wave R3 is 6 ms. Therefore, as shown in FIG. 6B, the ultrasonic sensor 21 receives the reflected wave R3 at a time of 48 ms, which is 6 ms after the time of transmitting the third ultrasonic wave S3, 42 ms. The reflected wave R3 is a reflected wave for the first determination, and the third ultrasonic wave S3 is an ultrasonic wave transmitted immediately before the reception of the reflected wave R3.

The fourth ultrasonic wave S4 hits the obstacle X11 and is reflected. The ultrasonic sensor 21 receives the reflected wave R4 of the fourth ultrasonic wave S4, and the detection unit 32 again detects that the obstacle X11 is behind the forklift 10. At this time, the time required from the transmission of the fourth ultrasonic wave S4 to the reception of the reflected wave R4 is 6 ms. Therefore, as shown in FIG. 6B, the ultrasonic sensor 21 receives the reflected wave R4 at a time of 70 ms 6 ms after the time of transmitting the fourth ultrasonic wave S4. The reflected wave R4 is a reflected wave for the second determination, and the fourth ultrasonic wave S4 is an ultrasonic wave transmitted immediately before the reception of the reflected wave R4.

The measuring unit 33 measures the second detection time Td and the third detection time Te, and outputs the measured second detection time Td and the third detection time Te to the determination unit 34. The second detection time Td is the time required from the transmission of the third ultrasonic wave S3 to the reception of the reflected wave R3, which is 6 ms. The third detection time Te is the time required from the transmission of the fourth ultrasonic wave S4 to the reception of the reflected wave R4, which is 6 ms. The determination unit 34 acquires the first to third reception times T1 to T3 (step S15). The determination unit 34 acquires the first detection time Tc: 6 ms input from the measurement unit 33 as the first reception time T1. The determination unit 34 acquires the second detection time Td: 6 ms input from the measurement unit 33 as the second reception time T2. The determination unit 34 acquires the third detection time Te: 6 ms input from the measurement unit 33 as the third reception time T3.

In Example 1-2, the second ultrasonic wave S2 hits the obstacle X12 and is reflected. The ultrasonic sensor 21 receives the reflected wave R20 of the second ultrasonic wave S2, and the detection unit 32 again detects that the obstacle X12 is behind the forklift 10. At this time, the time required from the transmission of the second ultrasonic wave S2 to the reception of the reflected wave R20 is 26 ms. Therefore, as shown in FIG. 7B, the ultrasonic sensor 21 receives the reflected wave R20 at a time of 46 ms 26 ms after the time of transmitting the second ultrasonic wave S2. The reflected wave R20 is a reflected wave for the first determination, and the third ultrasonic wave S3 is an ultrasonic wave transmitted immediately before the reception of the reflected wave R20.

The third ultrasonic wave S3 hits the obstacle X12 and is reflected. The ultrasonic sensor 21 receives the reflected wave R30 of the third ultrasonic wave S3, and the detection unit 32 again detects that the obstacle X12 is behind the forklift 10. At this time, the time required from the transmission of the third ultrasonic wave S3 to the reception of the reflected wave R30 is 26 ms. Therefore, as shown in FIG. 7B, the ultrasonic sensor 21 receives the reflected wave R30 at a time of 68 ms 26 ms after the time of transmitting the third ultrasonic wave S3. The reflected wave R30 is a reflected wave for the second determination, and the fourth ultrasonic wave S4 is an ultrasonic wave transmitted immediately before the reception of the reflected wave R30.

The measuring unit 33 measures the second detection time Td and the third detection time Te, and outputs the measured second detection time Td and the third detection time Te to the determination unit 34. The second detection time Td is the time required from the transmission of the third ultrasonic wave S3 to the reception of the reflected wave R20, which is 4 ms. The third detection time Te is the time required from the transmission of the fourth ultrasonic wave S4 to the reception of the reflected wave R30, which is 4 ms. The determination unit 34 acquires the first to third reception times T1 to T3 (step S15). The determination unit 34 acquires the first detection time Tc: 6 ms input from the measurement unit 33 as the first reception time T1. The determination unit 34 acquires the second detection time Td: 4 ms input from the measurement unit 33 as the second reception time T2. The determination unit 34 acquires the third detection time Te: 4 ms input from the measurement unit 33 as the third reception time T3.

In Examples 1-1 and 1-2, the determination unit 34 calculates the first determination time ΔT1 and the second determination time ΔT2 (step S16). In Example 1-1, the first determination time ΔT1 and the second determination time ΔT2 are 0 ms, respectively. In Example 1-2, the first determination time ΔT1 and the second determination time ΔT2 are 2 ms, respectively. The determination unit 34 compares the calculated first determination time ΔT1 and the second determination time ΔT2 with the preset threshold value ΔTx (step S17).

In Example 1-1, since both the first determination time ΔT1 and the second determination time ΔT2 are equal to or less than the threshold value ΔTx (YES in step S17), the determination unit 34 uses the detected obstacle X11 as a short-distance obstacle. (Step S18). On the other hand, in Example 1-2, since both the first determination time ΔT1 and the second determination time ΔT2 are larger than the threshold value ΔTx (NO in step S17), the determination unit 34 makes the detected obstacle X12 a long-distance obstacle. It is determined that it is a thing (step S19).

The operation of the first embodiment will be described.
The reflected waves received by the ultrasonic sensor 21 include the case where the ultrasonic waves transmitted immediately before the reception of the reflected waves are reflected by a short-range obstacle as in Example 1-1 and the case where the reflected waves are reflected by a short-range obstacle as in Example 1-2. It is considered that the ultrasonic wave transmitted before the ultrasonic wave transmitted immediately before the reception of the reflected wave is reflected by a long-distance obstacle.

In the case of Example 1-1, the timing of receiving the reflected wave is determined by the timing of transmitting the ultrasonic wave immediately before the reception of the reflected wave. Therefore, even if the ultrasonic wave transmission interval is different between the first transmission interval Ta and the second transmission interval Tb, the first reception time T1 and the second reception time T2 are almost the same, and the first reception time T1 and the third reception time T3 are almost the same. Therefore, the first determination time ΔT1 and the second determination time ΔT2 are equal to or less than the threshold value ΔTx.

In the case of Example 1-2, the timing of receiving the reflected wave is determined by the timing of transmitting the ultrasonic wave two times before the reception of the reflected wave. Therefore, if the ultrasonic wave transmission interval is different between the first transmission interval Ta and the second transmission interval Tb, the first reception time T1 and the third reception are different from the first reception time T1 and the second reception time T2. Different from time T3. Therefore, the first determination time ΔT1 and the second determination time ΔT2 are larger than the threshold value ΔTx.

As described above, the first determination time ΔT1 and the second determination time ΔT2 when the obstacle is a short-distance obstacle are the first determination time ΔT1 and the second determination time when the obstacle is a long-distance obstacle. It is different from the judgment time ΔT2. Therefore, from the comparison result between the first determination time ΔT1 and the threshold value ΔTx and the comparison result between the second determination time ΔT2 and the threshold value ΔTx, the detected obstacle is a short-distance obstacle or a short-distance obstacle. Can be determined.

The effect of the first embodiment will be described.
(1-1) The reflected wave received by the ultrasonic sensor 21 includes a case where the ultrasonic wave transmitted immediately before the reception of the reflected wave is reflected by a short-range obstacle and a case where the reflected wave is transmitted immediately before the reception of the reflected wave. It is conceivable that the ultrasonic waves transmitted before the ultrasonic waves are reflected by a long-distance obstacle. In the former case, the timing of receiving the reflected wave is determined by the timing of transmitting the ultrasonic wave immediately before the reception of the reflected wave, and in the latter case, the timing of receiving the reflected wave is determined by the timing of the ultrasonic wave immediately before the reception of the reflected wave. It depends on the timing of ultrasonic transmission that occurs before transmission.

The obstacle detection device 20 detects the presence or absence of an obstacle, and when the obstacle is detected, determines whether the detected obstacle is a short-distance obstacle or a long-distance obstacle. When the obstacle detection device 20 detects the presence or absence of an obstacle, the transmission command unit 31 causes the ultrasonic sensor 21 to transmit ultrasonic waves at the first transmission interval Ta. When determining whether the obstacle detected by the obstacle detection device 20 is a short-distance obstacle or a long-distance obstacle, the transmission command unit 31 has a second transmission interval Tb different from the first transmission interval Ta. The ultrasonic sensor 21 is made to transmit ultrasonic waves. When the transmission interval of ultrasonic waves is different between the first transmission interval Ta and the second transmission interval Tb, the first determination time ΔT1 and the second determination time ΔT2 are reflected waves reflected by a short-distance obstacle. And the case where the reflected wave is reflected by a long-distance obstacle. Therefore, the determination unit 34 of the obstacle detection device 20 determines whether the detected obstacle is a short-distance obstacle or a long-distance obstacle based on the comparison result between the first determination time ΔT1 and the second determination time ΔT2 and the threshold value ΔTx. It can be determined whether it is a distance obstacle.

(Second Embodiment)
Hereinafter, a second embodiment embodying the obstacle detection device and the obstacle detection method will be described with reference to FIGS. 8 and 9. The description of the same configuration as that of the first embodiment will be omitted.

As shown in FIGS. 8A and 9A, the obstacle detection device 20 includes two ultrasonic sensors 21. The two ultrasonic sensors 21 are attached side by side to the counterweight 13 in the left-right direction. Each ultrasonic sensor 21 transmits ultrasonic waves to the rear of the vehicle body 11. A transmission command unit 31 and a detection unit 32 are connected to each ultrasonic sensor 21. The transmission command unit 31 transmits an ultrasonic transmission signal to each ultrasonic sensor 21, and each ultrasonic sensor 21 transmits an ultrasonic wave when a transmission signal is input from the transmission command unit 31. When each ultrasonic sensor 21 receives the reflected wave, it transmits a received signal to the detection unit 32, and the detection unit 32 detects an obstacle by inputting a transmission signal from each ultrasonic sensor 21.

One of the two ultrasonic sensors 21 is a first ultrasonic sensor 21a, and the other is a second ultrasonic sensor 21b. The transmission command unit 31 causes the first ultrasonic sensor 21a and the second ultrasonic sensor 21b to alternately transmit ultrasonic waves. The first ultrasonic sensor 21a can receive not only the reflected wave of the ultrasonic wave transmitted by the first ultrasonic sensor 21a but also the reflected wave of the ultrasonic wave transmitted by the second ultrasonic sensor 21b. Similarly, the second ultrasonic sensor 21b can receive not only the reflected wave of the ultrasonic wave transmitted by the second ultrasonic sensor 21b but also the reflected wave of the ultrasonic wave transmitted by the first ultrasonic sensor 21a. Therefore, in the second embodiment, the ultrasonic sensor 21 that transmits ultrasonic waves and the ultrasonic sensor 21 that receives reflected waves may or may not be the same.

In the second embodiment, as in the first embodiment, the detection target range A is within 3.4 m behind the forklift 10 from the ultrasonic sensor 21. Further, the first transmission interval Ta is set to 20 ms in order to detect an obstacle within the detection target range A at an early stage while making it possible to detect the obstacle. Therefore, when the obstacle detection device 20 detects the presence or absence of an obstacle, the transmission command unit 31 alternately outputs a transmission signal to the first ultrasonic sensor 21a and the second ultrasonic sensor 21b every 20 ms. That is, the second ultrasonic sensor 21b transmits the ultrasonic wave 20 ms after the first ultrasonic sensor 21a transmits the ultrasonic wave, and the first ultrasonic sensor 21a transmits the ultrasonic wave 20 ms after the second ultrasonic sensor 21b transmits the ultrasonic wave. Send ultrasonic waves. In the second embodiment, the second transmission interval Tb refers to the interval from the transmission of ultrasonic waves by the first ultrasonic sensor 21a to the transmission of ultrasonic waves by the second ultrasonic sensor 21b.

Next, a specific example of detecting an obstacle will be described with reference to Examples 2-1 and 2-2. In Examples 2-1 and 2, it is assumed that the forklift 10 does not run and is stopped while the obstacle is detected. The threshold value ΔTx is set to 1 ms.

In Example 2-1 as shown in FIG. 8A, consider a case where an obstacle X21 that did not exist behind the forklift 10 at time 0s appears behind the forklift 10 at time 20ms. The obstacle X21 is a short-distance obstacle existing 1.02 m behind the second ultrasonic sensor 21b, which is within the detection target range A of the second ultrasonic sensor 21b. The shape of the obstacle X21 is shown in a simplified form. Further, it is assumed that the obstacle X21 does not move after appearing at the time of 20 ms.

As shown in FIG. 8B, the first ultrasonic sensor 21a and the second ultrasonic sensor 21b transmit ultrasonic waves at the first transmission interval Ta (step S10). The time when the first ultrasonic wave S1 is transmitted from the first ultrasonic wave sensor 21a is set to 0s. In Example 2-1 because the obstacle X21 does not exist in the detection target range A of the first ultrasonic sensor 21a at time 0s, the first ultrasonic wave S1 is attenuated without hitting the obstacle X21. Therefore, the first ultrasonic sensor 21a and the second ultrasonic sensor 21b do not receive the reflected wave from the time 0s to the elapse of 20ms. The second ultrasonic sensor 21b transmits the second ultrasonic wave S2 at a time 20 ms 20 ms after the time 0 s when the first ultrasonic wave S1 is transmitted according to the first transmission interval Ta. At the time of 20 ms, the obstacle X21 exists within the detection target range A of the second ultrasonic sensor 21b. Therefore, the second ultrasonic wave S2 is reflected toward the second ultrasonic wave sensor 21b by hitting the obstacle X21. The second ultrasonic sensor 21b receives the reflected wave R2 of the second ultrasonic wave S2 (YES in step S11). At this time, the time required from the transmission of the second ultrasonic wave S2 to the reception of the reflected wave R2 is 6 ms. Therefore, the time when the second ultrasonic sensor 21b receives the reflected wave R2 is 26 ms after 6 ms from the time when the second ultrasonic wave S2 is transmitted. The detection unit 32 detects that the obstacle X21 is within the detectable range B behind the forklift 10 (step S13). The reflected wave R2 is a reflected wave for detection, and the second ultrasonic wave S2 is an ultrasonic wave transmitted immediately before receiving the reflected wave R2.

In Example 2-2, as shown in FIG. 9A, consider the case where the obstacle X22 is behind the forklift 10 at time 0s. The obstacle X22 is a long-distance obstacle that is outside the detection target range A and within the detectable range B of the first ultrasonic sensor 21a and exists 4.41 m behind the first ultrasonic sensor 21a. The shape of the obstacle X22 is shown in a simplified form. Further, it is assumed that the obstacle X22 does not move when the obstacle detection device 20 detects the obstacle.

As shown in FIG. 9B, the first ultrasonic sensor 21a and the second ultrasonic sensor 21b transmit ultrasonic waves at the first transmission interval Ta (step S10). The time when the first ultrasonic wave S1 is transmitted from the first ultrasonic wave sensor 21a is set to 0s. In Example 2-2, the obstacle X22 exists within the detectable range B of the first ultrasonic sensor 21a at time 0s. Therefore, the first ultrasonic wave S1 is reflected toward the second ultrasonic wave sensor 21b by hitting the obstacle X22. The second ultrasonic sensor 21b receives the reflected wave R10 of the first ultrasonic wave S1. At this time, the time required from the transmission of the first ultrasonic wave S1 to the reception of the reflected wave R10 is 26 ms (YES in step S11). Therefore, the time when the second ultrasonic sensor 21b receives the reflected wave R10 is 26 ms after the time 0s when the transmission of the first ultrasonic wave S1 is performed. The first ultrasonic sensor 21a and the second ultrasonic sensor 21b do not receive the reflected wave between the time 0s and the elapse of 20ms. The second ultrasonic sensor 21b transmits the second ultrasonic wave S2 at a time 20 ms 20 ms after the time 0 s when the first ultrasonic wave S1 is transmitted according to the first transmission interval Ta. Since the obstacle X22 does not exist in the detection target range A of the second ultrasonic sensor 21b, the second ultrasonic wave S2 is attenuated without hitting the obstacle X22. The detection unit 32 detects that there is an obstacle X22 behind the forklift 10 (step S13). The reflected wave R10 is a reflected wave for detection, and the second ultrasonic wave S2 is an ultrasonic wave transmitted immediately before the reception of the reflected wave R10.

In Examples 2-1 and 2, the measuring unit 33 measures the first detection time Tc. The first detection time Tc is the time required from the transmission of the second ultrasonic wave S2 to the reception of the reflected waves R2 and R10, which is 6 ms. The measuring unit 33 outputs the measured first detection time Tc: 6 ms to the transmission command unit 31 and the determination unit 34. The transmission command unit 31 sets the second transmission interval Tb. The second transmission interval Tb is set to be different from the first transmission interval Ta and different from Ta + Tc, which is the sum of the first transmission interval Ta and the first detection time Tc. In Examples 2-1 and 2, the second transmission interval Tb is set to, for example, 22 ms.

The first ultrasonic sensor 21a transmits the third ultrasonic wave S3 at a time of 40 ms 20 ms after the time when the second ultrasonic wave S2 is transmitted according to the first transmission interval Ta. The second ultrasonic sensor 21b transmits the fourth ultrasonic wave S4 at a time 62 ms 22 ms after the time 40 ms when the third ultrasonic wave S3 was transmitted according to the second transmission interval Tb. The first ultrasonic sensor 21a transmits the fifth ultrasonic wave S5 at a time 82 ms 20 ms after the time when the fourth ultrasonic wave S4 is transmitted according to the first transmission interval Ta. The second ultrasonic sensor 21b transmits the sixth ultrasonic wave S6 at a time of 104 ms 22 ms after the time when the fifth ultrasonic wave S5 is transmitted according to the second transmission interval Tb. That is, the second ultrasonic sensor 21b transmits ultrasonic waves twice at the second transmission interval Tb: 22 ms (step S14).

In Example 2-1 the fourth ultrasonic wave S4 is reflected toward the second ultrasonic sensor 21b by hitting the obstacle X21. The second ultrasonic sensor 21b receives the reflected wave R4 of the fourth ultrasonic wave S4, and the detection unit 32 again detects that the obstacle X21 is behind the forklift 10. At this time, the time required from the transmission of the fourth ultrasonic wave S4 to the reception of the reflected wave R4 is 6 ms. Since the obstacle X21 does not exist in the detection target range A of the first ultrasonic sensor 21a, the third ultrasonic wave S3 is attenuated without hitting the obstacle X21. Therefore, as shown in FIG. 8B, the second ultrasonic sensor 21b receives the reflected wave R4 of the fourth ultrasonic wave S4 at a time of 68 ms 6 ms after the time when the fourth ultrasonic wave S4 is transmitted. To do. The reflected wave R4 is a reflected wave for the first determination, and the fourth ultrasonic wave S4 is an ultrasonic wave transmitted immediately before the reception of the reflected wave R4.

The sixth ultrasonic wave S6 is reflected toward the second ultrasonic sensor 21b by hitting the obstacle X21. The second ultrasonic sensor 21b receives the reflected wave R6 of the sixth ultrasonic wave S6, and the detection unit 32 again detects that there is an obstacle behind the forklift 10. At this time, the time required from the transmission of the sixth ultrasonic wave S6 to the reception of the reflected wave R6 is 6 ms. The fifth ultrasonic wave S5 is attenuated without hitting the obstacle X21. Therefore, as shown in FIG. 8B, the second ultrasonic sensor 21b receives the reflected wave R6 of the sixth ultrasonic wave S6 at a time of 110 ms 6 ms after the time of transmitting the sixth ultrasonic wave S6. To do. The reflected wave R6 is a reflected wave for the second determination, and the fourth ultrasonic wave S4 is an ultrasonic wave transmitted immediately before the reception of the reflected wave R4.

The measuring unit 33 measures the second detection time Td and the third detection time Te, and outputs the measured second detection time Td and the third detection time Te to the determination unit 34. The second detection time Td is the time required from the transmission of the fourth ultrasonic wave S4 to the reception of the reflected wave R4, which is 6 ms. The third detection time Te is the time required from the transmission of the sixth ultrasonic wave S6 to the reception of the reflected wave R6, which is 6 ms. The determination unit 34 acquires the first to third reception times T1 to T3 (step S15). The determination unit 34 acquires the first detection time Tc: 6 ms input from the measurement unit 33 as the first reception time T1. The determination unit 34 acquires the second detection time Td: 6 ms input from the measurement unit 33 as the second reception time T2. The determination unit 34 acquires the third detection time Te: 6 ms input from the measurement unit 33 as the third reception time T3.

In Example 2-2, the third ultrasonic wave S3 is reflected toward the second ultrasonic wave sensor 21b by hitting the obstacle X22. The second ultrasonic sensor 21b receives the reflected wave R30 of the third ultrasonic wave S3, and the detection unit 32 again detects that there is an obstacle X22 behind the forklift 10. At this time, the time required from the transmission of the third ultrasonic wave S3 to the reception of the reflected wave R30 is 26 ms. Since the obstacle X22 does not exist in the detection target range A of the second ultrasonic sensor 21b, the fourth ultrasonic wave S4 is attenuated without hitting the obstacle X22. Therefore, as shown in FIG. 9B, the second ultrasonic sensor 21b receives the reflected wave R30 of the third ultrasonic wave S3 at a time of 66 ms 26 ms after the time of transmitting the third ultrasonic wave S3. To do. The reflected wave R30 is a reflected wave for the first determination, and the fourth ultrasonic wave S4 is an ultrasonic wave transmitted immediately before the reception of the reflected wave R30.

The fifth ultrasonic wave S5 is reflected toward the second ultrasonic wave sensor 21b by hitting the obstacle X22. The second ultrasonic sensor 21b receives the reflected wave R50 of the fifth ultrasonic wave S5, and the detection unit 32 again detects that there is an obstacle X22 behind the forklift 10. At this time, the time required from the transmission of the fifth ultrasonic wave S5 to the reception of the reflected wave R50 is 26 ms. Therefore, as shown in FIG. 9B, the second ultrasonic sensor 21b receives the reflected wave R50 of the fifth ultrasonic wave S5 at a time of 108 ms 26 ms after the time of transmitting the fifth ultrasonic wave S5. To do. The reflected wave R50 is a reflected wave for the second determination, and the sixth ultrasonic wave S6 is an ultrasonic wave transmitted immediately before the reception of the reflected wave R50.

The measuring unit 33 measures the second detection time Td and the third detection time Te, and outputs the measured second detection time Td and the third detection time Te to the determination unit 34. The second detection time Td is the time required from the transmission of the fourth ultrasonic wave S4 to the reception of the reflected wave R30, which is 4 ms. The third detection time Te is the time required from the transmission of the sixth ultrasonic wave S6 to the reception of the reflected wave R50, which is 4 ms. The determination unit 34 acquires the first to third reception times T1 to T3 (step S15). The determination unit 34 acquires the first detection time Tc: 6 ms input from the measurement unit 33 as the first reception time T1. The determination unit 34 acquires the second detection time Td: 4 ms input from the measurement unit 33 as the second reception time T2. The determination unit 34 acquires the third detection time Te: 4 ms input from the measurement unit 33 as the third reception time T3.

In Examples 2-1 and 2, the determination unit 34 calculates the first determination time ΔT1 and the second determination time ΔT2 (step S16). In Example 1-1, the first determination time ΔT1 and the second determination time ΔT2 are 0 ms, respectively. In Example 1-2, the first determination time ΔT1 and the second determination time ΔT2 are 2 ms, respectively. The determination unit 34 compares the calculated first determination time ΔT1 and the second determination time ΔT2 with the preset threshold value ΔTx (step S17).

In Example 2-1 because both the first determination time ΔT1 and the second determination time ΔT2 are equal to or less than the threshold value ΔTx (YES in step S17), the determination unit 34 uses the detected obstacle X11 as a short-distance obstacle. (Step S18). On the other hand, in Example 2-2, since both the first determination time ΔT1 and the second determination time ΔT2 are larger than the threshold value ΔTx (NO in step S17), the determination unit 34 makes the detected obstacle X12 a long-distance obstacle. It is determined that it is a thing (step S19).

The operation of the second embodiment will be described.
The reflected wave received by the second ultrasonic sensor 21b includes a case where the ultrasonic wave transmitted immediately before the reception of the reflected wave is reflected by a short-range obstacle as in Example 2-1 and Example 2-2. It is considered that the ultrasonic wave transmitted before the ultrasonic wave transmitted immediately before the reception of the reflected wave is reflected by a long-distance obstacle as in the above case.

In the case of Example 2-1 the reception timing of the reflected wave is determined by the transmission timing of the ultrasonic wave performed immediately before the reception of the reflected wave. Therefore, even if the ultrasonic wave transmission interval is different between the first transmission interval Ta and the second transmission interval Tb, the first reception time T1 and the second reception time T2 are almost the same, and the first reception time T1 and the third reception time T3 are almost the same. Therefore, the first determination time ΔT1 and the second determination time ΔT2 are equal to or less than the threshold value ΔTx.

In the case of Example 2-2, the timing of receiving the reflected wave is determined by the timing of transmitting the ultrasonic wave two times before the reception of the reflected wave. Therefore, if the ultrasonic wave transmission interval is different between the first transmission interval Ta and the second transmission interval Tb, the first reception time T1 and the third reception are different from the first reception time T1 and the second reception time T2. Different from time T3. That is, the first determination time ΔT1 and the second determination time ΔT2 are larger than the threshold value ΔTx.

As described above, the first determination time ΔT1 and the second determination time ΔT2 when the obstacle is a short-distance obstacle are the first determination time ΔT1 and the second determination time when the obstacle is a long-distance obstacle. It is different from the judgment time ΔT2. Therefore, from the comparison result between the first determination time ΔT1 and the threshold value ΔTx and the comparison result between the second determination time ΔT2 and the threshold value ΔTx, the detected obstacle is a short-distance obstacle or a short-distance obstacle. Can be determined.

The effect of the second embodiment will be described.
(2-1) The reflected waves received by the first ultrasonic sensor 21a and the second ultrasonic sensor 21b include the case where the ultrasonic waves transmitted immediately before the reception of the reflected waves are reflected by a short-range obstacle. It is considered that the ultrasonic wave transmitted before the ultrasonic wave transmitted immediately before the reception of the reflected wave is reflected by a long-distance obstacle. In the former case, the timing of receiving the reflected wave is determined by the timing of transmitting the ultrasonic wave immediately before the reception of the reflected wave, and in the latter case, the timing of receiving the reflected wave is determined by the timing of the ultrasonic wave immediately before the reception of the reflected wave. It depends on the timing of ultrasonic transmission that occurs before transmission.

The obstacle detection device 20 detects the presence or absence of an obstacle, and when the obstacle is detected, determines whether the detected obstacle is a short-distance obstacle or a long-distance obstacle. When the obstacle detection device 20 detects the presence or absence of an obstacle, the transmission command unit 31 causes the first ultrasonic sensor 21a and the second ultrasonic sensor 21b to transmit ultrasonic waves at the first transmission interval Ta. When determining whether the obstacle detected by the obstacle detection device 20 is a short-distance obstacle or a long-distance obstacle, the transmission command unit 31 has a second transmission interval Tb different from the first transmission interval Ta. The second ultrasonic sensor 21b is made to transmit ultrasonic waves. When the transmission interval of ultrasonic waves is different between the first transmission interval Ta and the second transmission interval Tb, the first determination time ΔT1 and the second determination time ΔT2 are reflected waves reflected by a short-distance obstacle. And the case where the reflected wave is reflected by a long-distance obstacle. Therefore, the determination unit 34 of the obstacle detection device 20 determines whether the detected obstacle is a short-distance obstacle or a long-distance obstacle based on the comparison result between the first determination time ΔT1 and the second determination time ΔT2 and the threshold value ΔTx. It can be determined whether it is a distance obstacle.

The above embodiment can be modified and implemented as follows. The above-described embodiments and modifications can be implemented in combination with each other within a technically consistent range.
○ The number of ultrasonic sensors 21 included in the obstacle detection device 20 is not limited to 1 or 2, and may be 3 or more.

○ In the first embodiment and the second embodiment, the ultrasonic sensor 21 may be attached to the counterweight 13 by inserting the ultrasonic sensor 21 into a hole formed in the counterweight 13, a bracket or the like. It may be attached to the counterweight 13 by screwing via.

○ In the second embodiment, the direction in which the first ultrasonic sensor 21a and the second ultrasonic sensor 21b are arranged is not limited to the left-right direction. The first ultrasonic sensor 21a and the second ultrasonic sensor 21b may be arranged in the vertical direction, for example.

○ In the first embodiment and the second embodiment, the obstacle detection device 20 may detect obstacles existing in front of the forklift 10 or on the side of the forklift 10. In this case, the ultrasonic sensor may be attached to the forklift 10 so that the ultrasonic wave is transmitted in the direction in which the obstacle is to be detected. The obstacle detection device 20 may detect obstacles in any of the front, rear, and side directions, or may detect obstacles in a plurality of directions. Good.

○ In the first embodiment, the second transmission interval Tb may be set shorter than the first transmission interval Ta. Hereinafter, the case where the second transmission interval Tb is set to 18 ms will be described with reference to Examples 1-1 and 1-2 of the first embodiment.

As shown in FIG. 10A, in Example 1-1, the ultrasonic sensor 21 transmits the third ultrasonic wave S3 at a time of 38 ms 18 ms after the time of transmitting the second ultrasonic wave S2. The ultrasonic sensor 21 receives the reflected wave R3 of the third ultrasonic wave S3 at a time 44 ms 6 ms after the time 38 ms when the third ultrasonic wave S3 is transmitted. Further, the ultrasonic sensor 21 transmits the fourth ultrasonic wave S4 at a time of 56 ms 18 ms after the time of transmitting the third ultrasonic wave S3. The ultrasonic sensor 21 receives the reflected wave R4 of the fourth ultrasonic wave S4 at a time 62 ms 6 ms after the time 56 ms when the fourth ultrasonic wave S4 is transmitted. Therefore, the first to third reception times T1 to T3 are 6 ms each, and the first determination time ΔT1 and the second determination time ΔT2 are 0 ms, respectively.

As shown in FIG. 10B, in Example 1-2, the ultrasonic sensor 21 transmits the third ultrasonic wave S3 at a time of 38 ms 18 ms after the time of transmitting the second ultrasonic wave S2. The ultrasonic sensor 21 receives the reflected wave R20 of the second ultrasonic wave S2 at a time of 46 ms 26 ms after the time of transmitting the second ultrasonic wave S2 20 ms. Further, the ultrasonic sensor 21 transmits the fourth ultrasonic wave S4 at a time of 56 ms 18 ms after the time of transmitting the third ultrasonic wave S3. The ultrasonic sensor 21 receives the reflected wave R30 of the third ultrasonic wave S3 at a time of 64 ms 26 ms after the time of transmitting the third ultrasonic wave S3. Therefore, the first reception time T1 is 6 ms, and the second reception time T2 and the third reception time T3 are 8 ms, respectively. Further, the first determination time ΔT1 and the second determination time ΔT2 are 2 ms, respectively.

As described above, the first determination time ΔT1 and the second determination time ΔT2 when the obstacle X11 is a short-distance obstacle are the first determination time ΔT1 and the second determination time ΔT2 when the obstacle X12 is a long-distance obstacle. It is different from the second determination time ΔT2. Therefore, as described in the first embodiment, the obstacle is a short-distance obstacle or a long-distance obstacle based on the comparison result between the first determination time ΔT1 and the second determination time ΔT2 and the threshold value ΔTx. Can be determined.

○ In the second embodiment, the second transmission interval Tb may be set shorter than the first transmission interval Ta. Hereinafter, the case where the second transmission interval Tb is set to 18 ms will be described with reference to Examples 2-1 and 2-2 of the second embodiment.

As shown in FIG. 11 (a), in Example 2-1 the second ultrasonic sensor 21b has a third ultrasonic wave S3 at a time of 58 ms 18 ms after the transmission of the third ultrasonic wave S3 according to the second transmission interval Tb. 4 Ultrasonic wave S4 is transmitted. The second ultrasonic sensor 21b receives the reflected wave R4 of the fourth ultrasonic wave S4 at a time of 64 ms 6 ms after the time when the fourth ultrasonic wave S4 is transmitted 58 ms. The first ultrasonic sensor 21a transmits the fifth ultrasonic wave S5 at a time 78 ms 20 ms after the time 58 ms when the fourth ultrasonic wave S4 is transmitted according to the first transmission interval Ta. The second ultrasonic sensor 21b transmits the sixth ultrasonic wave S6 at a time 96 ms 18 ms after the time 78 ms when the fifth ultrasonic wave S5 is transmitted according to the second transmission interval Tb. The second ultrasonic sensor 21b receives the reflected wave R6 of the sixth ultrasonic wave S6 at a time 102 ms 6 ms after the time 96 ms when the sixth ultrasonic wave S6 is transmitted. Therefore, the first to third reception times T1 to T3 are 6 ms each, and the first determination time ΔT1 and the second determination time ΔT2 are 0 ms, respectively.

As shown in FIG. 11B, in Example 2-2, in Example 2-2, the second ultrasonic sensor 21b has a time 58 ms 18 ms after the time 40 ms when the third ultrasonic wave S3 is transmitted according to the second transmission interval Tb. 4 Ultrasonic wave S4 is transmitted. The second ultrasonic sensor 21b receives the reflected wave R30 of the third ultrasonic wave S3 at a time of 66 ms 26 ms after the time when the third ultrasonic wave S3 is transmitted 40 ms. The first ultrasonic sensor 21a transmits the fifth ultrasonic wave S5 at a time of 78 ms 20 ms after the time of transmitting the fourth ultrasonic wave S4 according to the first transmission interval Ta. The second ultrasonic sensor 21b transmits the sixth ultrasonic wave S6 at a time 96 ms 18 ms after the time 78 ms when the fifth ultrasonic wave S5 is transmitted according to the second transmission interval Tb. The second ultrasonic sensor 21b receives the reflected wave R50 of the sixth ultrasonic wave S6 at a time of 104 ms 26 ms after the time when the fifth ultrasonic wave S5 is transmitted 78 ms. Therefore, the first reception time T1 is 6 ms, and the second reception time T2 and the third reception time T3 are 8 ms, respectively. The first determination time ΔT1 and the second determination time ΔT2 are 2 ms, respectively.

As described above, the first determination time ΔT1 and the second determination time ΔT2 when the obstacle X21 is a short-distance obstacle are the first determination time ΔT1 and the second determination time ΔT2 when the obstacle X22 is a long-distance obstacle. It is different from the second determination time ΔT2. Therefore, as described in the second embodiment, the obstacle is a short-distance obstacle or a long-distance obstacle based on the comparison result between the first determination time ΔT1 and the second determination time ΔT2 and the threshold value ΔTx. Can be determined.

-In the first embodiment and the second embodiment, the definitions of the first to third reception times T1 to T3 may be changed as appropriate. For example, the first reception time T1 may be Ta + Tc, which is the sum of the first transmission interval Ta and the first detection time Tc. In this case, Tb + Td, which is the sum of the second transmission interval Tb and the second detection time Td, is defined as the second reception time T2, and Tb + Te, which is the sum of the second transmission interval Tb and the third detection time Te, is the third reception time. Let it be T3. In this case, the determination unit 34 determines that the obstacle is a long-distance obstacle if YES in step S19 (step S21), and determines the obstacle as a short-distance obstacle if NO in step S19 (step S20). ).

In the first embodiment and the second embodiment, the parameter for determining the first reception time T1 is one of the first detection time Tc, whereas in the above example, the parameter for determining the first reception time T1 is determined. Is the first transmission interval Ta and the first detection time Tc. Therefore, the influence of the error of the first reception time T1 of the first embodiment and the second embodiment is relatively smaller than the influence of the error of the first reception time T1 of the above example. Similarly, the influence of the error of the second reception time T2 and the third reception time T3 is relatively smaller than the influence of the error of the second reception time T2 and the third reception time T3 in the above example. Therefore, the error between the first determination time ΔT1 and the second determination time ΔT2 is also reduced. As a result, the threshold value ΔTx can be set to a smaller value, and it is possible to more accurately determine whether the obstacle is a short-distance obstacle or a long-distance obstacle.

○ In the first embodiment and the second embodiment, the measurement unit 33 may be omitted, and the determination unit 34 may measure the first to third detection times Ta to Tc.
-In the first embodiment and the second embodiment, the ultrasonic wave sensor 21 may transmit the ultrasonic wave only once at the second transmission interval Tb. The determination unit 34 determines whether the obstacle is a short-distance obstacle or a long-distance obstacle by comparing the first determination time ΔT1 with the threshold value ΔTx. In this case, the determination time can be shortened.

○ In the first embodiment and the second embodiment, the ultrasonic wave sensor 21 may transmit ultrasonic waves three times or more at the second transmission interval Tb. The determination unit 34 may determine whether the obstacle is a short-distance obstacle or a long-distance obstacle by comparing three or more determination times with the threshold value ΔTx. In this case, the determination accuracy is high. Further, for example, when determining whether the obstacle is a short-distance obstacle or a long-distance obstacle based on the comparison result between the four determination times and the threshold value ΔTx, all the determination times are the threshold value ΔTx. If it is less than or equal to, it may be determined that it is a short-distance obstacle, or if it is three determination times of ΔTx or less, it may be determined that it is a short-distance obstacle.

○ When the ultrasonic sensor 21 transmits ultrasonic waves a plurality of times at the second transmission interval Tb as in the first embodiment, the second transmission interval Tb does not have to be a constant interval. For example, in Examples 1-1 and 1-2, the second transmission interval Tb between the transmission of the second ultrasonic wave S2 and the transmission of the third ultrasonic wave S3 is 22 ms, and the transmission of the third ultrasonic wave S3 and the fourth ultrasonic wave. The second transmission interval Tb with the transmission of S4 may be 18 ms. However, the second transmission interval Tb is different from the first transmission interval Ta.

○ When the second ultrasonic sensor 21b transmits ultrasonic waves a plurality of times at the second transmission interval Tb as in the second embodiment, the second transmission interval Tb does not have to be a constant interval. For example, in Examples 2-1, 2-2, the second transmission interval Tb between the transmission of the third ultrasonic wave S3 and the transmission of the fourth ultrasonic wave S4 is 22 ms, and the transmission of the fifth ultrasonic wave S5 and the sixth ultrasonic wave. The second transmission interval Tb with the transmission of S6 may be 18 ms. However, the second transmission interval Tb is different from the first transmission interval Ta.

○ In the first embodiment and the second embodiment, the first to third reception times T1 to T3 are collectively acquired in step S15, but the first to third reception times T1 to T3 are acquired in individual steps. May be good. For example, the first reception time T1 may be acquired immediately after the detection unit 32 detects an obstacle. Further, for example, the second reception time T2 may be acquired immediately after the ultrasonic sensor 21 receives the reflected wave for the first determination. Further, for example, the third reception time T3 may be acquired immediately after the ultrasonic sensor 21 receives the reflected wave for the second determination.

○ In the first embodiment and the second embodiment, the threshold value ΔTx does not have to be a constant value, and may be changed depending on the situation in which the obstacle is detected.
As an example of the situation where the obstacle is detected, the situation where the forklift 10 moves with respect to the obstacle that does not move can be considered. When the forklift 10 approaches the obstacle, that is, when the obstacle is detected while traveling backward, the distance between the obstacle and the ultrasonic sensor 21 becomes shorter as time passes. Therefore, the reception time of the determination reflected wave is shorter than the reception time of the detection reflected wave. Therefore, the determination time is longer than when both the forklift 10 and the obstacle are stopped. On the contrary, when the obstacle is detected in the direction away from the forklift 10 with respect to the obstacle, that is, while traveling forward, the distance between the obstacle and the ultrasonic sensor 21 becomes longer as time passes. Therefore, the reception time of the determination reflected wave is longer than the reception time of the detection reflected wave. Therefore, the determination time is longer than when both the forklift 10 and the obstacle are stopped.

Based on the above, the threshold value ΔTx may be set based on, for example, the speed of the forklift 10. Specifically, the obstacle detection device 20 acquires vehicle speed information of the forklift 10 from the vehicle speed sensor of the forklift 10, and uses the acquired vehicle speed of the forklift 10 to determine the amount of change in the distance between the obstacle and the ultrasonic sensor 21. The value of the threshold value ΔTx is increased or decreased based on the calculated amount of change. In this case, it is possible to more accurately determine whether the detected obstacle is a short-distance obstacle or a long-distance obstacle even while the forklift 10 is traveling.

-In the first embodiment and the second embodiment, the ultrasonic sensor 21 may be an ultrasonic sensor including a piezoelectric vibrator for transmission and a piezoelectric vibrator for reception. In this case, the reflected wave can be received even while the ultrasonic sensor 21 is transmitting ultrasonic waves. Therefore, the second transmission interval Tb may be the same as Ta + Tc, which is the sum of the first transmission interval Ta and the first detection time Tc, as long as it is different from the first transmission interval Ta.

○ In the first embodiment and the second embodiment, the specific numerical value of the detection target range A may be appropriately changed depending on, for example, the device on which the obstacle detection device 20 is mounted and the obstacle to be detected.

○ In the first embodiment and the second embodiment, the specific numerical value of the detectable range B differs depending on, for example, the specifications of the ultrasonic sensor 21.
-In the first embodiment and the second embodiment, the sound velocity V may be corrected by, for example, the temperature or medium of the environment in which the obstacle is detected.

○ In the first embodiment and the second embodiment, the specific numerical values of the first transmission interval Ta and the second transmission interval Tb may be appropriately changed depending on, for example, the detection status of obstacles.
○ In the first embodiment and the second embodiment, the control ECU 30 may be integrated with the main controller 17.

-In the ultrasonic sensor 21 of the first embodiment and the second embodiment, the threshold value of the reception intensity of the reflected wave for determining whether or not to transmit the received signal to the detection unit 32 may be variable.
○ The forklift 10 may be a forklift that is automatically operated.

○ The obstacle detection device 20 may be mounted on any moving body such as a passenger car, an industrial vehicle such as a towing tractor, or an autonomously moving robot, as long as it is a moving body that requires detection of an obstacle.

10 ... Forklift as a moving body, 20 ... Obstacle detection device, 21 ... Ultrasonic sensor, 31 ... Transmission command unit, 32 ... Detection unit, 34 ... Judgment unit, R2, R10 ... Reflected wave as a reflected wave for detection, R3, R4, R6, R20, R30, R50 ... The reflected wave as the judgment reflected wave, T1 ... The first reception time which is the reception time of the detection reflected wave, T2 ... The second reception time which is the reception time of the judgment reflected wave. Reception time, T3 ... Third reception time, which is the reception time of the reflected wave for determination, Ta ... First transmission interval, Tb ... Second transmission interval.

Claims (4)

An ultrasonic sensor that transmits ultrasonic waves and receives reflected waves reflected by obstacles,
A transmission command unit that causes the ultrasonic sensor to repeatedly transmit ultrasonic waves,
A detection unit that detects the obstacle from the reception result of the reflected wave by the ultrasonic sensor, and
It is an obstacle detection device equipped with
The transmission command unit causes the ultrasonic sensor to transmit an ultrasonic wave at the first transmission interval, and when the detection unit detects an obstacle by receiving the reflected wave by the ultrasonic sensor, the first transmission interval is set. Causes the ultrasonic sensor to transmit ultrasonic waves at different second transmission intervals.
For determination, which is the difference between the reception time of the detection reflected wave, which is the reflected wave used for detecting the obstacle, and the reception time of the determination reflected wave, which is the reflected wave received after the detection reflected wave. An obstacle characterized by including a determination unit for calculating a time and determining whether the obstacle is a short-range obstacle or a long-range obstacle based on a comparison result between the determination time and a threshold value. Detection device. The reception time of the detection reflected wave is the difference between the reception time of the detection reflected wave and the transmission time of the ultrasonic wave performed immediately before the reception of the detection reflected wave.
The obstacle detection according to claim 1, wherein the reception time of the determination reflected wave is the difference between the reception time of the determination reflected wave and the transmission time of the ultrasonic wave performed immediately before the reception of the determination reflected wave. apparatus. The obstacle detection device according to claim 1 or 2, wherein the threshold value is changed according to the speed of a moving body on which the obstacle detection device is mounted. An obstacle detection method that detects an obstacle from the reception result of the reflected wave by an ultrasonic sensor that transmits ultrasonic waves and receives the reflected wave reflected by the obstacle.
The step of transmitting ultrasonic waves from the ultrasonic sensor at the first transmission interval,
When the ultrasonic sensor receives the reflected wave, the step of transmitting ultrasonic waves from the ultrasonic sensor at a second transmission interval different from the first transmission interval, and
The step of acquiring the reception time of the reflected wave for detection, which is the reflected wave used for detecting the obstacle, and
The step of acquiring the reception time of the judgment reflected wave, which is the reflected wave received after the detection reflected wave, and
A step of calculating the determination time, which is the difference between the reception time of the detection reflected wave and the reception time of the determination reflection wave, and
A step of determining whether the obstacle is a short-distance obstacle or a long-distance obstacle based on the result of comparison between the determination time and the threshold value.
An obstacle detection method comprising.