JP7263952B2 - Obstacle detection device and obstacle detection method - Google Patents

Description

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

2. Description of the Related Art There is known an obstacle detection device that detects an obstacle using an ultrasonic sensor that has a transmission function of transmitting ultrasonic waves and a reception function of receiving reflected waves reflected by an obstacle. The obstacle detection device includes a transmission command section that controls transmission of ultrasonic waves by the ultrasonic sensor, and a detection section that detects the presence or absence of an obstacle based on the result of reception of reflected waves by the ultrasonic sensor. When an ultrasonic wave is transmitted from the ultrasonic sensor, if an obstacle exists within the detectable range of the ultrasonic sensor, the transmitted ultrasonic wave hits the obstacle and is reflected. On the other hand, if there is no obstacle within the detectable range of the ultrasonic sensor, the transmitted ultrasonic wave hits the obstacle and is attenuated without being reflected. The detection unit detects that there is an obstacle when the ultrasonic sensor receives the reflected wave.

As disclosed in Patent Literature 1, some obstacle detection devices include a plurality of ultrasonic sensors. For example, the obstacle detection device disclosed in Patent Document 1 includes first to fourth ultrasonic sensors. The first to fourth ultrasonic sensors are arranged in order. The first ultrasonic sensor and the third ultrasonic sensor constitute a first ultrasonic sensor group, and the second ultrasonic sensor and the fourth ultrasonic sensor constitute a second ultrasonic sensor group. That is, the obstacle detection device includes two ultrasonic sensor groups each made up of two ultrasonic sensors. The transmission command unit causes the two ultrasonic sensors constituting the ultrasonic sensor group to simultaneously transmit ultrasonic waves while switching between the plurality of ultrasonic sensor groups. Specifically, the transmission command unit causes the first ultrasonic sensor and the third ultrasonic sensor constituting the first ultrasonic sensor group to simultaneously transmit ultrasonic waves, and then the second ultrasonic sensor constituting the second ultrasonic sensor group. The second ultrasonic sensor and the fourth ultrasonic sensor are caused to transmit ultrasonic waves at the same time. In this case, the presence or absence of an obstacle can be detected earlier than when ultrasonic waves are individually transmitted from the first to fourth ultrasonic sensors.

JP 2006-298266 A

By the way, when the detection unit detects that there is an obstacle when the ultrasonic sensor receives the reflected wave once, the possibility of erroneous detection increases. For this reason, it is preferable that the transmission command unit repeats transmission of ultrasonic waves by the ultrasonic sensor, and the detection unit detects that there is an obstacle when the number of receptions of the reflected waves during that time reaches a predetermined number or more. However, repeating the transmission of ultrasonic waves by the ultrasonic sensor causes a delay in detecting the presence or absence of obstacles.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide an obstacle detection device and an obstacle detection method capable of early detection of the presence or absence of an obstacle while suppressing erroneous detection. It is in.

An obstacle detection device for solving the above problems is a plurality of ultrasonic waves composed of two or more ultrasonic sensors each having a transmitting function of transmitting ultrasonic waves and a receiving function of receiving reflected waves reflected by obstacles. Obstacle detection comprising: a group of sound wave sensors; a transmission command unit that controls transmission of ultrasonic waves by the ultrasonic sensor; and a detection unit that detects the presence or absence of the obstacle from a reception result of the reflected wave by the ultrasonic sensor. In the apparatus, the transmission command unit performs a first transmission process of causing two or more ultrasonic sensors constituting the ultrasonic sensor group to simultaneously transmit ultrasonic waves while switching between the plurality of ultrasonic sensor groups. and when the detection unit tentatively detects that there is an obstacle because at least one of the plurality of ultrasonic sensors receives a reflected wave in the first transmission process, one of the plurality of ultrasonic sensors, the first performing a second transmission process for causing an ultrasonic sensor set as a retransmission sensor to transmit an ultrasonic wave based on the reception result of the reflected wave by the first transmission process, wherein the detection unit receives the reflected wave by the second transmission process; The gist of this is that the presence or absence of an obstacle is actually detected based on the number of times.

According to this, since the detection unit actually detects the presence or absence of an obstacle based on the number of times the reflected wave is received by the ultrasonic sensor, the presence of the obstacle is detected when the ultrasonic sensor receives the reflected wave once. False detection can be suppressed compared to the case.

Further, when the detection unit tentatively detects that there is an obstacle, the transmission command unit performs the second transmission process, and the detection unit actually detects the presence or absence of the obstacle based on the number of times the reflected wave is received by the second transmission process. do. In the first transmission process, the transmission command unit causes each ultrasonic sensor group to transmit ultrasonic waves in order. Cause the transmitting sensor to transmit ultrasonic waves. In the second transmission process, the time required for the second transmission process is shorter than the time required for the first transmission process because ultrasonic waves are not sequentially transmitted from a plurality of ultrasonic sensor groups. Therefore, even after the detection unit provisionally detects the presence of an obstacle, the transmission command unit repeats the first transmission process, and the detection unit actually detects the presence of an obstacle. The time required for detection can be shortened. Therefore, the presence or absence of an obstacle can be detected early while suppressing erroneous detection.

Further, in the obstacle detection device, it is preferable that the transmission command section continuously performs the first transmission process a plurality of times.
According to this, erroneous detection can be further suppressed as compared with the case where the transmission command unit performs the first transmission process once.

Further, in the obstacle detection device, the ultrasonic sensor that has received the reflected wave by the first transmission process is set as a receiving sensor, and the ultrasonic sensor group that transmits the ultrasonic wave immediately before the receiving sensor receives the reflected wave. is the transmission sensor group, the detection distance calculated based on the time required from the transmission sensor group to transmit the ultrasonic wave until the reception sensor receives the reflected wave is within the detection target range of the obstacle If the distance is equal to or less than the judgment distance set based on the above, the transmission command unit performs the second transmission process and the detection unit actually detects the presence or absence of an obstacle, and if the detected distance is longer than the judgment distance, It is preferable that the detection unit actually detects that there is no obstacle.

Obstacle detection devices are required to detect obstacles within a detection target range. Therefore, when the detection target range is smaller than the obstacle detectable range of the ultrasonic sensor, it is not necessary to detect obstacles outside the detection target range and within the detectable range. However, the ultrasonic sensor receives not only reflected waves reflected by obstacles within the detection target range, but also reflected waves reflected by obstacles outside the detection target range and within the detectable range.

When the ultrasonic waves transmitted by the first transmission process are reflected by an obstacle outside the detection target range and within the detectable range, the detection distance becomes longer than the determination distance. On the other hand, when the ultrasonic waves transmitted by the first transmission process hit an obstacle within the detection target range and are reflected, the detection distance becomes equal to or less than the determination distance. Therefore, when the detection distance is longer than the judgment distance, the detection unit actually detects that there is no obstacle. Therefore, it can be detected earlier that there is no obstacle within the detection target range. Further, when the detected distance is equal to or less than the judgment distance, the transmission command section performs the second transmission process, and the detection section performs main detection of the presence or absence of an obstacle. Therefore, erroneous detection of the presence or absence of an obstacle within the detection target range can be suppressed.

Further, in the obstacle detection device, the transmission command unit performs the second transmission process a plurality of times, and sets the transmission interval of the ultrasonic waves by the retransmission sensor in the second transmission process to Different from the transmission interval of the ultrasonic waves by the ultrasonic sensor group, the detection unit detects the reception time of the reflected wave of the ultrasonic wave transmitted by the first transmission process and the ultrasonic wave performed before the reception of the reflected wave a first determination time that is the difference between the transmission time and the reception time of the reflected wave of the ultrasonic wave transmitted by the second transmission process and the transmission time of the ultrasonic wave performed before the reception of the reflected wave a difference between the first determination time and the second determination time is acquired, and the obstacle is determined to be a short-range obstacle based on a comparison result between a threshold value and a determination value that is the difference between the first determination time and the second determination time. or a long range obstacle.

The reflected waves received by the ultrasonic sensor include the case where the ultrasonic wave transmitted immediately before the reflected wave is reflected by a short-range obstacle, and the ultrasonic wave transmitted immediately before the reflected wave is received. It is conceivable that the ultrasonic waves transmitted to the object are reflected by a distant obstacle. In the former case, the timing of receiving the reflected wave is determined by the timing of the transmission of the ultrasonic wave immediately before receiving the reflected wave. It is determined by the timing of the transmission of ultrasonic waves that precedes the transmission. Therefore, by making the transmission interval of the ultrasonic waves in the first transmission process different from the transmission interval of the ultrasonic waves in the second transmission process, the determination value and the threshold, which are the difference between the first determination time and the second determination time The results of comparison with are different between the former case and the latter case. Therefore, it can be determined whether the detected obstacle is a short-distance obstacle or a long-distance obstacle.

An obstacle detection method for solving the above problems includes a plurality of ultrasonic sensors configured by two or more ultrasonic sensors having a transmission function for transmitting ultrasonic waves and a reception function for receiving reflected waves reflected by obstacles. With regard to the group of ultrasonic sensors, performing a first transmission process for simultaneously transmitting ultrasonic waves to two or more ultrasonic sensors constituting the group of ultrasonic sensors while switching the group of ultrasonic sensors; When at least one of the plurality of ultrasonic sensors tentatively detects that there is an obstacle by receiving the reflected wave, the plurality of ultrasonic sensors based on the reception result of the reflected wave by the first transmission process a step of setting a transmission sensor; a step of performing a second transmission process of causing the retransmission sensor to transmit an ultrasonic wave; and a step of actually detecting the presence or absence of an obstacle based on the number of receptions of reflected waves in the second transmission process. and

According to this, since the presence or absence of an obstacle is actually detected based on the number of times the reflected wave is received by the ultrasonic sensor, compared with the case where the presence of an obstacle is detected when the ultrasonic sensor receives the reflected wave once. can suppress false positives.

Further, when it is tentatively detected that there is an obstacle, the second transmission process is performed, and the presence or absence of the obstacle is actually detected based on the number of times the reflected wave is received by the second transmission process. In the first transmission process, ultrasonic waves are transmitted in order from each ultrasonic sensor group. to be sent. In the second transmission process, the time required for the second transmission process is shorter than the time required for the first transmission process because ultrasonic waves are not sequentially transmitted from a plurality of ultrasonic sensor groups. Therefore, even after provisionally detecting the presence of an obstacle, the first transmission process is repeatedly performed, and the time required for the actual detection of the presence of an obstacle can be shortened compared to the case of performing the actual detection of the presence of an obstacle. Therefore, the presence or absence of an obstacle can be detected early while suppressing erroneous detection.

ADVANTAGE OF THE INVENTION According to this invention, the presence or absence of an obstacle can be detected early, suppressing false detection.

(a) is a schematic side view of a forklift equipped with an obstacle detection device, and (b) is a schematic rear view of a forklift equipped with an obstacle detection device. The block diagram which shows the structure of a forklift. 1 is a block diagram showing the configuration of an obstacle detection device; FIG. (a), (b) is a schematic diagram showing a detection range of an obstacle. 4 is a flowchart showing an obstacle detection method according to the first embodiment; (a) to (f) are schematic diagrams showing the arrangement of ultrasonic sensors and obstacles in Example 1. FIG. FIG. 4 is a diagram showing transmission/reception timings of ultrasonic waves in Example 1; 8 is a flowchart showing an obstacle detection method according to the second embodiment; The flowchart which shows the obstacle detection method of 4th Embodiment. (a) to (f) are schematic diagrams showing the arrangement of ultrasonic sensors and obstacles in Example 4-1. FIG. 10 is a diagram showing transmission/reception timing of ultrasonic waves in Example 4-1; (a) to (f) are schematic diagrams showing the arrangement of ultrasonic sensors and obstacles in Example 4-2. FIG. 13 is a diagram showing transmission/reception timing of ultrasonic waves in Example 4-2;

(First embodiment)
A first embodiment embodying an obstacle detection device and an obstacle detection method will be described below.
As shown in FIG. 1( a ), the forklift 10 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 . As shown in FIG. 1B, the rear end surface of the counterweight 13 includes a first surface 13a, a second surface 13b which is a surface continuous with the first surface 13a and is located on the left side of the first surface 13a, It has a third surface 13c that is continuous with the first surface 13a and located on the right side of the first surface 13a. The first surface 13a is orthogonal to the front-rear direction. The second surface 13b is slanted such that the left end is located forward of the right end. The third surface 13c is slanted such that the right end is positioned forward of the left end. The forklift 10 is a forklift that is operated by a passenger.

As shown in FIG. 2, the forklift 10 includes a cargo handling mechanism 14 that operates the cargo handling device 12, a drive mechanism 15 that causes the forklift 10 to travel, a key switch 16 that switches the forklift 10 between a start state and a stop state, and a main controller. 17.

The main controller 17 has a CPU 18 and a memory 19 . The memory 19 stores programs and the like for operating the forklift 10 . The CPU 18 performs calculations using information input to the main controller 17 and information such as programs 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 carry out 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 carry out the cargo handling operation or the traveling operation.

The forklift 10 is equipped with an obstacle detection device 20 that detects obstacles using ultrasonic waves.
As shown in FIG. 3, the obstacle detection device 20 includes a plurality of ultrasonic sensors. The obstacle detection device 20 of this embodiment includes six ultrasonic sensors, first to sixth ultrasonic sensors 21a to 21f. Each of the ultrasonic sensors 21a to 21f is of a transmitting/receiving type in which one element performs both transmission and reception of ultrasonic waves.

Each of the ultrasonic sensors 21a-21f has a piezoelectric vibrator (not shown). A piezoelectric vibrator can convert an electric signal into vibration and can convert vibration into an electric signal. The piezoelectric vibrator vibrates when a transmission signal is input from a transmission command section 31, which will be described later. Ultrasonic waves are transmitted from the ultrasonic sensors 21a to 21f by vibrating the piezoelectric transducers. The ultrasonic waves transmitted from the ultrasonic sensors 21a to 21f have the same frequency. When there is an obstacle ahead of the transmission direction of the ultrasonic wave, the transmitted ultrasonic wave hits the obstacle and is reflected to become a reflected wave. The piezoelectric vibrator vibrates when it receives the reflected wave, and outputs a received signal to the detector 32, which will be described later. That is, each of the ultrasonic sensors 21a to 21f has a transmitting function of transmitting ultrasonic waves and a receiving function of receiving reflected waves.

Since the piezoelectric transducer is of a transmission/reception type, the ultrasonic sensors 21a to 21f cannot receive reflected waves while transmitting ultrasonic waves. Further, each of the ultrasonic sensors 21a to 21f can receive not only the reflected ultrasonic waves transmitted by itself but also the reflected ultrasonic waves transmitted by other ultrasonic sensors. In the first embodiment, it is assumed that the ultrasonic sensor that transmits the ultrasonic wave and the ultrasonic sensor that receives the reflected wave of the ultrasonic wave are the same.

The obstacle detection device 20 of this embodiment is used to detect obstacles behind the forklift 10 . In addition, since the steering angle of the steering wheels of the forklift 10 is larger than that of a passenger car, the obstacle detection device 20 can also detect obstacles in the lateral range behind the forklift 10. Desired.

As shown in FIG. 1(b), the first to sixth ultrasonic sensors 21a to 21f are attached to the rear end surface of the counterweight 13 in a row from left to right in the horizontal direction. The first ultrasonic sensor 21 a is attached to the second surface 13 b of the counterweight 13 . The second to fifth ultrasonic sensors 21b to 21e are attached to the first surface 13a of the counterweight 13. As shown in FIG. A sixth ultrasonic sensor 21 f is attached to the third surface 13 c of the counterweight 13 .

As shown in FIGS. 4(a) and 4(b), each of the ultrasonic sensors 21a to 21f transmits ultrasonic waves to the rear of the vehicle body 11. As shown in FIG. In this embodiment, the range in which each of the ultrasonic sensors 21a to 21f can detect obstacles (hereinafter referred to as detectable range A) is assumed to be a range up to 5.10 m behind each of the ultrasonic sensors 21a to 21f. is set. In other words, the ultrasonic waves transmitted from the ultrasonic sensors 21a to 21f can reach at least 5.10 m ahead.

As shown in FIG. 3 , the first ultrasonic sensor 21 a and the fourth ultrasonic sensor 21 d constitute the first ultrasonic sensor group 21 . The second ultrasonic sensor 21 b and the fifth ultrasonic sensor 21 e constitute a second ultrasonic sensor group 22 . The third ultrasonic sensor 21 c and the sixth ultrasonic sensor 21 f constitute a third ultrasonic sensor group 23 . Therefore, the obstacle detection device 20 of this embodiment includes three ultrasonic sensor groups each composed of two ultrasonic sensors.

As shown in FIG. 2 , the obstacle detection device 20 has a control ECU 30 . The control ECU 30 is an Electronic Control Unit that includes a CPU and a storage section including a RAM, a ROM, and the like. Various programs for controlling the obstacle detection device 20 are stored in the storage unit. The control ECU 30 may include dedicated hardware that executes at least part of the various types of processing, such as an application specific integrated circuit (ASIC). The control ECU 30 may be configured as a circuit including one or more processors operating according to a computer program, one or more dedicated hardware circuits such as ASIC, or a combination thereof. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to perform processes. Memory, or computer-readable media, includes anything that can be accessed by a general purpose or special purpose computer. The control ECU 30 is connected to the main controller 17 so as to be able to communicate with each other. Incidentally, in this embodiment, the control ECU 30 is formed separately from the main controller 17 .

As shown in FIG. 3, the control ECU 30 includes a transmission command section 31 connected to each of the ultrasonic sensors 21a-21f. The transmission command unit 31 controls transmission of ultrasonic waves by the first to sixth ultrasonic sensors 21a to 21f. Specifically, the transmission command unit 31 causes the ultrasonic sensors 21a to 21f to transmit ultrasonic waves by outputting transmission signals to the ultrasonic sensors 21a to 21f. The transmission command unit 31 repeatedly outputs a transmission signal while the forklift 10 is activated by the key switch 16 . Each of the ultrasonic sensors 21a to 21f transmits ultrasonic waves each time a transmission signal from the transmission command unit 31 is input. The timing at which the ultrasonic sensors 21a to 21f transmit ultrasonic waves corresponds to the timing at which the transmission command section 31 outputs transmission signals to the ultrasonic sensors 21a to 21f.

The control ECU 30 includes a detection section 32 connected to each of the ultrasonic sensors 21a-21f. The detection unit 32 recognizes that each of the ultrasonic sensors 21a to 21f has received the reflected wave by receiving the received signal from each of the ultrasonic sensors 21a to 21f. The detection unit 32 is connected to the transmission command unit 31 .

The transmission command unit 31 performs a first transmission process of simultaneously transmitting ultrasonic waves to the two ultrasonic sensors forming the ultrasonic sensor group while switching between the first to third ultrasonic sensor groups 21 to 23 . In this embodiment, the transmission command unit 31 switches the ultrasonic sensor groups in the order of the first ultrasonic sensor group 21 →second ultrasonic sensor group 22 →third ultrasonic sensor group 23 . That is, the transmission command unit 31 first causes the first ultrasonic sensor 21a and the fourth ultrasonic sensor 21d, which constitute the first ultrasonic sensor group 21, to simultaneously transmit ultrasonic waves. The transmission command unit 31 next causes the second ultrasonic sensor 21b and the fifth ultrasonic sensor 21e, which constitute the second ultrasonic sensor group 22, to transmit ultrasonic waves at the same time. The transmission command unit 31 next causes the third ultrasonic sensor 21c and the sixth ultrasonic sensor 21f, which constitute the third ultrasonic sensor group 23, to transmit ultrasonic waves at the same time. The transmission command unit 31 causes the first to third ultrasonic sensor groups 21 to 23 to transmit ultrasonic waves at a first transmission interval Ta, which will be described later.

When an obstacle exists within the detectable range A of at least one of the first to sixth ultrasonic sensors 21a to 21f, at least one of the first to sixth ultrasonic sensors 21a to 21f receives reflected waves. The ultrasonic sensor that received the reflected wave of the ultrasonic wave transmitted by the first transmission process is defined as the receiving sensor, and the ultrasonic sensor group that transmitted the ultrasonic wave immediately before the receiving sensor receives the reflected wave is defined as the transmitting sensor group.

When at least one of the first to sixth ultrasonic sensors 21a to 21f receives a reflected wave through the first transmission process, the detection unit 32 tentatively detects that there is an obstacle behind the forklift 10. FIG. Further, the detection unit 32 sets a retransmission sensor from the first to sixth ultrasonic sensors 21a to 21f based on the reception result of the reflected wave by the first transmission process. In this embodiment, the detection unit 32 sets the reception sensor as the retransmission sensor. When the first to sixth ultrasonic sensors 21a to 21f do not receive the reflected wave by the first transmission process, the detection unit 32 can detect the first to sixth ultrasonic sensors 21a to 21f behind the forklift 10. If there is no obstacle within the range A, the actual detection is performed.

The transmission command unit 31 performs a second transmission process of causing the ultrasonic sensor set as the retransmission sensor to transmit ultrasonic waves. When a plurality of ultrasonic sensors are set as retransmission sensors, the transmission command unit 31 causes all the ultrasonic sensors set as retransmission sensors to simultaneously transmit ultrasonic waves. The transmission command unit 31 causes the retransmission sensor to transmit ultrasonic waves at a second transmission interval Tb, which will be described later. In this embodiment, the transmission command unit 31 repeats the second transmission process three times.

The detection unit 32 actually detects the presence or absence of an obstacle based on the number of receptions of the reflected wave by the second transmission process. In this embodiment, the detection unit 32 acquires the number of times of reception N, which is the number of times the retransmission sensor has received the reflected wave through the second transmission process for three times. Note that when a plurality of ultrasonic sensors are set as retransmission sensors, the detection unit 32 acquires the number of reception times N of reflected waves by the second transmission process for three times for each retransmission sensor.

The detection unit 32 performs actual detection of the presence or absence of an obstacle by comparing the number of receptions N of reflected waves with a predetermined number of determinations Nh. The determination count Nh is set to, for example, two times. When the number of times of reception N is equal to or greater than the number of times of determination Nh, the detection unit 32 actually detects that there is an obstacle behind the forklift 10 . In addition, when a plurality of ultrasonic sensors are set as retransmission sensors, the detection unit 32 detects that the number of receptions N of at least one of the plurality of retransmission sensors is equal to or greater than the threshold value Nh, and the forklift 10 If there is an obstacle behind, it will be detected. When the number of times of reception N is less than the number of times of determination Nh, the detection unit 32 actually detects that there is no obstacle within the detectable range A of the first to sixth ultrasonic sensors 21 a to 21 f behind the forklift 10 .

The detector 32 outputs the detection result to the main controller 17 . The main controller 17 does not allow the forklift 10 to travel when the detection unit 32 actually detects that there is an obstacle behind the forklift 10 .

By the way, as shown in FIG. 4(a), the distance X [m] from the ultrasonic sensor to the obstacle P is determined by the ultrasonic wave reflected by the ultrasonic sensor after the ultrasonic sensor transmits the ultrasonic wave. From the transmission/reception time t [sec], which is the time required for reception, and the speed of sound V [m/sec], X=V×t/2. Therefore, the longer the distance X [m] from the ultrasonic sensor to the obstacle P, the longer the transmission/reception time t [sec]. As described above, in this embodiment, the detectable range A of the ultrasonic sensor is set to 5.10 m. For this reason, for example, if the speed of sound V is 340 [m/sec], if the ultrasonic sensor does not receive the reflected wave within about 30 ms after transmitting the ultrasonic wave, the obstacle P does not exist.

In this embodiment, the first transmission interval Ta is set to 30 ms in order to detect obstacles within the detectable range A at an early stage while enabling detection of obstacles. Therefore, in the first transmission process, the second ultrasonic sensor group 22 transmits ultrasonic waves 30 ms after the first ultrasonic sensor group 21 transmits ultrasonic waves, and the second ultrasonic sensor group 22 transmits ultrasonic waves. is transmitted, the third ultrasonic sensor group 23 transmits ultrasonic waves 30 ms later. The second transmission interval Tb is also set to 30 ms, like the first transmission interval Ta. Therefore, the retransmitting sensor transmits the first ultrasonic wave 30 ms after the time when the third ultrasonic sensor group 23 transmits the ultrasonic wave, and from the time when the retransmitting sensor transmits the first ultrasonic wave, After 30 ms, the retransmitting sensor transmits ultrasound for the second time. Further, the retransmitting sensor transmits the ultrasonic wave for the third time 30 ms after the time when the retransmitting sensor transmits the ultrasonic wave for the second time.

Next, the obstacle detection method of the first embodiment will be described together with Example 1. FIG.
As shown in FIGS. 6A to 6F, in Example 1, an obstacle P1 exists within the detectable range A of the first ultrasonic sensor 21a, and the detectable range of the third ultrasonic sensor 21c An obstacle P2 exists in A. It is assumed that the forklift 10 and the obstacles P1 and P2 do not move. Also, in FIGS. 6A to 6F, the shapes of the obstacles P1 and P2 are illustrated in simplified form.

When the forklift 10 is activated by the key switch 16, the obstacle detection device 20 starts operating. The transmission command unit 31 performs first transmission processing.
Specifically, as shown in FIG. 5, the transmission command unit 31, as a part of the first transmission process, firstly detects the first ultrasonic sensor 21a and the fourth ultrasonic wave that constitute the first ultrasonic sensor group 21. At the same time, the sensor 21d is caused to transmit ultrasonic waves (step S11). The ultrasonic wave transmitted from the first ultrasonic sensor 21a is referred to as a first ultrasonic wave Us1, and the ultrasonic wave transmitted from the fourth ultrasonic sensor 21d is referred to as a fourth ultrasonic wave Us4.

As shown in FIG. 6A, in Example 1, the obstacle P1 exists within the detectable range A of the first ultrasonic sensor 21a. It reflects toward the ultrasonic sensor 21a. Since there is no obstacle within the detectable range A of the fourth ultrasonic sensor 21d, the fourth ultrasonic wave Us4 attenuates without hitting the obstacle. Therefore, as shown in FIG. 7, the first ultrasonic sensor 21a receives the reflected wave Ur1 of the first ultrasonic wave Us1. The first ultrasonic sensor 21a is a receiving sensor, and the first ultrasonic sensor group 21 is a transmitting sensor group.

As shown in FIG. 5, as a part of the first transmission process, the transmission command unit 31 then sends signals to the second ultrasonic sensor 21b and the fifth ultrasonic sensor 21e that constitute the second ultrasonic sensor group 22 simultaneously. Ultrasonic waves are transmitted (step S12). The ultrasonic wave transmitted from the second ultrasonic sensor 21b is referred to as a second ultrasonic wave Us2, and the ultrasonic wave transmitted from the fifth ultrasonic sensor 21e is referred to as a fifth ultrasonic wave Us5.

As shown in FIG. 6B, in Example 1, there is no obstacle within the detectable range A of the second ultrasonic sensor 21b and the fifth ultrasonic sensor 21e. The sound wave Us5 attenuates without hitting an obstacle. Therefore, as shown in FIG. 7, the first to sixth ultrasonic sensors 21a to 21f do not receive reflected waves.

As shown in FIG. 5, as a part of the first transmission process, the transmission command unit 31 then sends signals to the third ultrasonic sensor 21c and the sixth ultrasonic sensor 21f that constitute the third ultrasonic sensor group 23 simultaneously. Ultrasonic waves are transmitted (step S13). The ultrasonic wave transmitted from the third ultrasonic sensor 21c is referred to as a third ultrasonic wave Us3, and the ultrasonic wave transmitted from the sixth ultrasonic sensor 21f is referred to as a sixth ultrasonic wave Us6.

As shown in FIG. 6(c), in Example 1, the obstacle P2 exists within the detectable range A of the third ultrasonic sensor 21c. It reflects toward the ultrasonic sensor 21c. Since there is no obstacle within the detectable range A of the sixth ultrasonic sensor 21f, the sixth ultrasonic wave Us6 attenuates without hitting the obstacle. Therefore, as shown in FIG. 7, the third ultrasonic sensor 21c receives the reflected wave Ur3 of the third ultrasonic wave Us3. The third ultrasonic sensor 21c is a receiving sensor, and the third ultrasonic sensor group 23 is a transmitting sensor group.

As shown in FIG. 5, when the first to sixth ultrasonic sensors 21a to 21f do not receive the reflected wave in the first transmission process (NO in step S14), the detection unit 32 performs the main detection that there is no obstacle. (step S15). When at least one of the first to sixth ultrasonic sensors 21a to 21f receives a reflected wave by the first transmission process (YES in step S14), the detection unit 32 provisionally detects that there is an obstacle (step S16), The receiving sensor is set as a retransmitting sensor (step S17).

In example 1, since the first ultrasonic sensor 21a receives the reflected wave Ur1 and the third ultrasonic sensor 21c receives the reflected wave Ur3, the detector 32 tentatively detects that there is an obstacle. Further, the detection unit 32 sets the first ultrasonic sensor 21a and the third ultrasonic sensor 21c as retransmission sensors.

The transmission command unit 31 performs a second transmission process of causing the retransmission sensor to transmit ultrasonic waves. The transmission command unit 31 repeats the second transmission process three times (steps S18 to S20).
As shown in FIG. 6D, the transmission command unit 31 causes the first ultrasonic sensor 21a to transmit the first ultrasonic wave Us11 and causes the third ultrasonic sensor 21c to transmit the first ultrasonic wave Us11 as the first second transmission process. 3 Transmit an ultrasonic wave Us31. The first ultrasonic wave Us11 is reflected toward the first ultrasonic sensor 21a by hitting the obstacle P1. The third ultrasonic wave Us31 hits the obstacle P2 and is reflected toward the third ultrasonic sensor 21c. As shown in FIG. 7, the first ultrasonic sensor 21a receives the reflected wave Ur11 of the first ultrasonic wave Us11. The third ultrasonic sensor 21c receives the reflected wave Ur31 of the third ultrasonic wave Us31.

As shown in FIG. 6(e), the transmission command unit 31 causes the first ultrasonic sensor 21a to transmit the first ultrasonic wave Us12 and causes the third ultrasonic sensor 21c to transmit the first ultrasonic wave Us12 as the second transmission process for the second time. 3 Transmit an ultrasonic wave Us32. The first ultrasonic wave Us12 is reflected toward the first ultrasonic sensor 21a by hitting the obstacle P1. The third ultrasonic wave Us32 is reflected toward the third ultrasonic sensor 21c by hitting the obstacle P2. As shown in FIG. 7, the first ultrasonic sensor 21a receives the reflected wave Ur12 of the first ultrasonic wave Us12. The third ultrasonic sensor 21c receives the reflected wave Ur32 of the third ultrasonic wave Us32.

As shown in FIG. 6(f), the transmission command unit 31 causes the first ultrasonic sensor 21a to transmit the first ultrasonic wave Us13 and the third ultrasonic sensor 21c to transmit the first ultrasonic wave Us13 as the third second transmission process. 3 Transmit an ultrasonic wave Us33. The first ultrasonic wave Us13 is reflected toward the first ultrasonic sensor 21a by hitting the obstacle P1. The third ultrasonic wave Us33 is reflected toward the third ultrasonic sensor 21c by hitting the obstacle P2. As shown in FIG. 7, the first ultrasonic sensor 21a receives the reflected wave Ur13 of the first ultrasonic wave Us13. The third ultrasonic sensor 21c receives the reflected wave Ur33 of the third ultrasonic wave Us33.

As shown in FIG. 5, the detection unit 32 acquires the number of times N of reception of the reflected wave by the second transmission process for three times (step S21). In Example 1, the detection unit 32 acquires the number of times N1 of reflected waves received by the first ultrasonic sensor 21a: 3 times and the number of times N3 of times of received reflected waves by the third ultrasonic sensor 21c: 3 times.

When the number of receptions N of the reflected waves by the retransmission sensor is equal to or greater than the threshold value Nh (YES in step S22), the detection unit 32 actually detects that there is an obstacle behind the forklift 10 (step S23). When the number N of receptions of the reflected waves by the retransmission sensor is not equal to or greater than the determination number Nh (NO in step S22), that is, when the number N of receptions of the reflected waves by the retransmission sensor is less than the determination number Nh, the forklift 10 It is actually detected that there is no obstacle within the detectable range A of the first to sixth ultrasonic sensors 21a to 21f behind the (step S24).

In Example 1, the number of times N1 of reception of the reflected wave by the first ultrasonic sensor 21a is 3, and the number of times of determination Nh is 2 or more (Nh≦N1). In addition, the number of reception times N3 of the reflected wave by the third ultrasonic sensor 21c: 3 times is equal to or greater than the number of judgment times Nh: 2 (Nh≦N3). Therefore, the detection unit 32 actually detects that there is an obstacle behind the forklift 10 .

The obstacle detection device 20 repeats the flow shown in FIG. 5 until the forklift 10 is stopped by the key switch 16 .
The operation of the first embodiment will be described while comparing it with a comparative example.

First, the obstacle detection method of the comparative example will be described.
In the comparative example, the transmission command unit 31 performs the first transmission process as in the first embodiment. That is, the transmission command unit 31 causes the first to third ultrasonic sensor groups 21 to 23 to transmit ultrasonic waves in order at the first transmission interval Ta. When at least one of the first to sixth ultrasonic sensors 21a to 21f receives a reflected wave by the first transmission process, the detector 32 provisionally detects that there is an obstacle. When the detection unit 32 tentatively detects that there is an obstacle, the transmission command unit 31 repeats the first transmission process three times. The detection unit 32 acquires the number of reception times N1 to N6, which is the number of times each of the ultrasonic sensors 21a to 21f receives the reflected wave by the first transmission process for three times after the obstacle is tentatively detected. The detecting unit 32 determines that, for at least one of the first to sixth ultrasonic sensors 21a to 21f, when the number of reception times N1 to N6 of the reflected waves is the number of determination times Nh: 2 or more, there is an obstacle behind the forklift 10. and this detection. For each of the ultrasonic sensors 21a to 21f, the detection unit 32 detects the first to sixth ultrasonic sensors 21a to 21f behind the forklift 10 when the number of reception times N1 to N6 of the reflected waves is less than the determination number Nh: 2 times. If there is no obstacle within the detectable range A, the actual detection is performed.

Thus, in the comparative example, the detection unit 32 actually detects the presence or absence of an obstacle based on the number of receptions N1 to N6 of reflected waves by the ultrasonic sensors 21a to 21f. Also in the first embodiment, the detection unit 32 actually detects the presence or absence of an obstacle based on the number of reception times N of reflected waves by the retransmission sensor. For this reason, compared to the case where the detection unit 32 detects that there is an obstacle when at least one of the first to sixth ultrasonic sensors 21a to 21f receives the reflected wave once in the first transmission process. erroneous detection is suppressed.

By the way, in the first transmission process, the transmission command unit 31 causes the first to third ultrasonic sensor groups 21 to 23 to transmit ultrasonic waves in order at the first transmission interval Ta. Therefore, the time required for one first transmission process is the first transmission interval Ta: 30 ms.times.the number of ultrasonic sensor groups: 3 to 90 ms. In the second transmission process, the transmission command unit 31 causes the retransmission sensor to transmit ultrasonic waves at the second transmission interval Tb. Therefore, the time required for one second transmission process is 30 ms. That is, the time required for the second transmission process is shorter than the time required for the first transmission process.

In the comparative example, when the detection unit 32 tentatively detects that there is an obstacle, the transmission command unit 31 repeats the first transmission process three times, and the detection unit 32 detects the obstacle based on the number of times the reflected wave is received by the first transmission process. Main detection of the presence or absence of Therefore, in the comparative example, the time required from the time when the detection unit 32 tentatively detects the presence of an obstacle to the time when the actual detection of the presence of an obstacle is performed is 270 ms, which is the first transmission process times three times.

On the other hand, in the first embodiment, when the detection unit 32 tentatively detects that there is an obstacle, the transmission command unit 31 repeats the second transmission process three times, and the detection unit 32 receives the reflected wave by the second transmission process. The actual detection of the presence or absence of an obstacle is performed based on this. Therefore, in the present embodiment, the time required from when the detection unit 32 tentatively detects the presence of an obstacle to when the actual detection of the presence of an obstacle is performed is 90 ms, which is the second transmission process times three times.

In the first embodiment, when the detection unit 32 tentatively detects that there is an obstacle, the detection unit 32 sets the retransmission sensor, and the transmission command unit 31 performs the second transmission process to cause the retransmission sensor to transmit ultrasonic waves. . In the second transmission process, ultrasonic waves are transmitted from the ultrasonic sensors necessary for the main detection of the presence of obstacles, and ultrasonic waves are not transmitted from ultrasonic sensors unnecessary for the main detection of the presence of obstacles. In the second transmission process, the time required for the second transmission process is shorter than the time required for the first transmission process because the ultrasonic waves are not transmitted in order from the first to third ultrasonic sensor groups 21-23. As a result, in the first embodiment, the presence or absence of an obstacle can be fully detected earlier than in the comparative example while suppressing erroneous detection.

Effects of the first embodiment will be described.
(1) Since the detection unit 32 actually detects the presence or absence of an obstacle based on the number of times the ultrasonic sensor receives the reflected wave, when the ultrasonic sensor detects the presence of an obstacle when the reflected wave is received once. False positives can be suppressed compared to

Further, when the detection unit 32 tentatively detects that there is an obstacle, the transmission command unit 31 performs the second transmission process, and the detection unit 32 detects the presence or absence of the obstacle based on the number of times the reflected wave is received by the second transmission process. to be detected. In the first transmission process, the transmission command unit 31 sequentially transmits ultrasonic waves from each of the ultrasonic sensor groups 21 to 23, while in the second transmission process, based on the reception result of the reflected wave in the first transmission process. Causes the set retransmission sensor to transmit ultrasound. In the second transmission process, the time required for the second transmission process is shorter than the time required for the first transmission process because ultrasonic waves are not sequentially transmitted from the plurality of ultrasonic sensor groups 21 to 23 . Therefore, even after the detection unit 32 tentatively detects the presence of an obstacle, the transmission command unit 31 repeats the first transmission process, and the detection unit 32 actually detects the presence or absence of an obstacle. It is possible to shorten the time required for final detection of the presence or absence. Therefore, the presence or absence of an obstacle can be detected early while suppressing erroneous detection.

(Second embodiment)
A second embodiment of an obstacle detection device and an obstacle detection method will be described below. In addition, description is abbreviate|omitted about the same structure as 1st Embodiment.

As shown in FIG. 4(b), depending on the situation in which obstacle detection is performed, the range in which obstacle detection is required (hereinafter referred to as detection target range B) is smaller than the detectable range A. There is In the second embodiment, the detection target range B is set assuming a range up to 3.40 m behind each of the ultrasonic sensors 21a to 21f.

If an obstacle within the detection target range B is defined as a short-distance obstacle and an obstacle outside the detection target range B and within the detectable range A is defined as a long-distance obstacle, the presence/absence detection is required for the near distance obstacle. Since it is a distance obstacle, it is not necessary to detect the presence or absence of a long distance obstacle. However, each of the ultrasonic sensors 21a to 21f receives not only reflected waves reflected by obstacles within the detection target range B, but also reflected waves reflected by obstacles outside the detection target range B and within the detectable range A. receive. Therefore, in the first embodiment, when at least one of the first to sixth ultrasonic sensors 21a to 21f receives a reflected wave in the first transmission process, the detection unit 32 detects that the reflected wave is caused by a short-range obstacle. The presence of an obstacle is tentatively detected regardless of whether it is reflected or reflected by a distant obstacle.

In the second embodiment, when at least one of the first to sixth ultrasonic sensors 21a to 21f receives a reflected wave in the first transmission process, the detector 32 measures the first detection time Tx of the reflected wave. Here, the first detection time Tx is, as shown in FIG. 7, the time required from when the transmitting sensor group transmits ultrasonic waves to when the receiving sensors receive the reflected waves. In other words, the first detection time Tx is the difference between the time when the receiving sensor receives the reflected wave in the first transmission process and the time when the ultrasonic wave is transmitted immediately before the reflected wave is received. Note that when the first to sixth ultrasonic sensors 21a to 21f receive the reflected wave multiple times by the first transmission process, the detector 32 measures the first detection time Tx of the reflected wave each time.

The detection unit 32 calculates the detection distance L=V×Tx/2 from the measured first detection time Tx and the speed of sound V. FIG. The detection unit 32 compares the calculated detection distance L and the determination distance Lh. The determination distance Lh is a distance set based on the detection target range B. As shown in FIG. In this embodiment, the determination distance Lh is set to the detection target range B: 3.40 m. If the obstacle is a close-range obstacle, the detection distance L is equal to or less than the judgment distance Lh. If the obstacle is a long-distance obstacle, the detection distance L is longer than the determination distance Lh.

When the detection distance L is equal to or less than the judgment distance Lh, the transmission command unit 31 performs the second transmission processing on the assumption that the reflected wave received by the reception sensor is reflected by a short-range obstacle, and the detection unit 32 detects the presence or absence of the obstacle. Perform main detection. If the detection distance L is longer than the determination distance Lh, the reflected wave received by the receiving sensor is assumed to have been reflected by a long-distance obstacle, and the detector 32 actually detects that there is no obstacle. In this case, the transmission command unit 31 does not perform the second transmission process.

The obstacle detection method of the second embodiment will be described together with Example 2. FIG.
In example 2, the obstacle P1 exists at a position 4.42 m away from the first ultrasonic sensor 21a, and the obstacle P2 exists at a position 1.02 m away from the third ultrasonic sensor 21c. . That is, the obstacle P1 is a long-distance obstacle existing outside the detection target range B of the first ultrasonic sensor 21a and within the detectable range A, and the obstacle P2 is the detection target range of the third ultrasonic sensor 21c. It is a short-range obstacle that exists within B.

When the forklift 10 is activated by the key switch 16, the obstacle detection device 20 starts operating.
As shown in FIG. 8, the transmission command unit 31 performs first transmission processing (steps S31 to S33). Specifically, the transmission command unit 31 first causes the first ultrasonic sensor 21a and the fourth ultrasonic sensor 21d, which constitute the first ultrasonic sensor group 21, to simultaneously transmit ultrasonic waves (step S31). The transmission command unit 31 next causes the second ultrasonic sensor 21b and the fifth ultrasonic sensor 21e, which constitute the second ultrasonic sensor group 22, to simultaneously transmit ultrasonic waves (step S32). The transmission command unit 31 next causes the third ultrasonic sensor 21c and the sixth ultrasonic sensor 21f, which constitute the third ultrasonic sensor group 23, to simultaneously transmit ultrasonic waves (step S33).

In Example 2, the first ultrasonic sensor 21a receives the reflected wave Ur1 of the first ultrasonic wave Us1. The transmission/reception time t1 of the reflected wave Ur1 is 26 ms. The third ultrasonic sensor 21c also receives the reflected wave Ur3 of the third ultrasonic wave Us3. The transmission/reception time t3 of the reflected wave Ur3 is 6 ms.

When at least one of the first to sixth ultrasonic sensors 21a to 21f receives a reflected wave through the first transmission process (YES in step S34), the detector 32 measures the first detection time Tx of the reflected wave. In Example 2, the detector 32 measures a first detection time Tx1 of 26 ms for reflected wave Ur1 and a first detection time Tx2 of 6 ms for reflected wave Ur3, as shown in FIG. Note that FIG. 7 illustrates a case where the first detection times Tx1 and Tx2 are the same, and does not correspond to the first detection times Tx1 and Tx2 in the second example.

The detection unit 32 calculates the detection distance L from the measured first detection time Tx and the speed of sound V (step S36). In Example 2, the detection unit 32 calculates the detection distance L1: 4.42 m from the first detection time Tx1 and the sound velocity V of the reflected wave Ur1. Further, the detection unit 32 calculates the detection distance L2: 1.02 m from the first detection time Tx2 and the sound velocity V of the reflected wave Ur3.

The detection unit 32 compares the calculated detection distance L with the determination distance Lh (step S37). If the detection distance L is equal to or less than the determination distance Lh: 3.40 m (YES in step S37), the detection unit 32 tentatively detects that there is an obstacle (step S38). On the other hand, when the calculated detection distance L is not equal to or less than the determination distance Lh: 3.40 m (NO in step S37), that is, when the detection distance L is longer than the determination distance Lh, the detection unit 32 actually detects that there is no obstacle. (Step S39). In Example 2, the detection distance L1: 4.42 m is longer than the determination distance Lh: 3.40 m, and the detection distance L2: 1.02 m is less than or equal to the determination distance Lh: 3.40 m. Therefore, the detection unit 32 tentatively detects that there is an obstacle.

The flow after the detection unit 32 tentatively detects that there is an obstacle is the same as in the first embodiment, so description thereof will be omitted.
Actions and effects of the second embodiment will be described. In the second embodiment, the following effects can be obtained in addition to the effect (1-1) of the first embodiment.

(2-1) The obstacle detection device 20 only needs to be able to detect the presence or absence of a short-distance obstacle within the detection target range B. Therefore, when the detection target range B is smaller than the obstacle detectable range A by each of the ultrasonic sensors 21a to 21f, the presence or absence of a distant obstacle outside the detection target range B and within the detectable range A is determined. No detection required.

When the ultrasonic waves transmitted by the first transmission process hit a short-range obstacle and are reflected, the detection distance L becomes equal to or less than the determination distance Lh. On the other hand, when the ultrasonic waves transmitted by the first transmission process hit a distant obstacle and are reflected, the detection distance L becomes longer than the determination distance Lh. When the detection distance L is equal to or less than the determination distance Lh, the detection unit 32 tentatively detects that there is an obstacle. In this case, the transmission command unit 31 performs the second transmission process, and the detection unit 32 performs main detection of the presence or absence of the obstacle based on the number of times the reflected wave is received by the second transmission process. On the other hand, when the detection distance L is longer than the determination distance Lh, the detection unit 32 actually detects that there is no obstacle. In this case, the transmission command unit 31 does not perform the second transmission process. Therefore, erroneous detection of the presence or absence of an obstacle within the detection target range B can be suppressed, and the presence or absence of an obstacle can be detected earlier.

(Third embodiment)
A third embodiment, which embodies an obstacle detection device and an obstacle detection method, will be described below. Note that portions different from the first embodiment will be described, and descriptions of the same portions as the first embodiment will be omitted.

When an obstacle P1 is present within the detectable range A of the first ultrasonic sensor 21a, the first ultrasonic wave Us1 transmitted from the first ultrasonic sensor 21a hits the obstacle P1 and is reflected. At this time, as in the first embodiment, the first ultrasonic wave Us1 is often reflected toward the first ultrasonic sensor 21a. Depending on the environment in which the first ultrasonic wave Us1 is transmitted, the first ultrasonic wave Us1 may be reflected toward an ultrasonic sensor different from the first ultrasonic sensor 21a that is the transmission source. For example, the first ultrasonic wave Us1 may be reflected toward the second ultrasonic sensor 21b closest to the first ultrasonic sensor 21a, which is the transmission source. Similarly, the second to sixth ultrasonic waves Us2 to Us6 transmitted from the second to sixth ultrasonic sensors 21b to 21f are also reflected toward an ultrasonic sensor different from the ultrasonic sensor that is the transmission source. Sometimes. That is, in the first embodiment, it is assumed that the ultrasonic sensor that transmits the ultrasonic wave and the ultrasonic sensor that receives the reflected wave of the ultrasonic wave are the same. The ultrasonic sensor that transmits the ultrasonic wave and the ultrasonic sensor that receives the reflected ultrasonic wave may be different.

In the third embodiment, when the receiving sensor is an ultrasonic sensor that constitutes a group of transmitting sensors, the detection unit 32 sets the receiving sensor as a retransmitting sensor. On the other hand, if the receiving sensor is different from the ultrasonic sensors forming the transmitting sensor group, the detection unit 32 selects the ultrasonic sensor closest to the receiving sensor among the ultrasonic sensors forming the transmitting sensor group as the re-transmitting sensor. set.

The obstacle detection method of the third embodiment will be described together with Example 3.
The transmission command unit 31 performs first transmission processing.
As shown in FIG. 6A, the transmission command unit 31 first causes the first ultrasonic sensor 21a and the fourth ultrasonic sensor 21d, which constitute the first ultrasonic sensor group 21, to simultaneously transmit ultrasonic waves. In Example 3, as indicated by the two-dot chain line in FIG. 6A, the first ultrasonic wave Us1 hits the obstacle P1 and is reflected toward the second ultrasonic sensor 21b. The second ultrasonic sensor 21b receives the reflected wave Ur1 of the first ultrasonic wave Us1. The fourth ultrasonic wave Us4 attenuates without hitting the obstacle. Therefore, the second ultrasonic sensor 21b is a receiving sensor, and the first ultrasonic sensor group 21 is a transmitting sensor group.

As shown in FIG. 6B, the transmission command unit 31 next causes the second ultrasonic sensor 21b and the fifth ultrasonic sensor 21e, which constitute the second ultrasonic sensor group 22, to simultaneously transmit ultrasonic waves. The second ultrasonic wave Us2 and the fifth ultrasonic wave Us5 are attenuated without hitting the obstacle.

As shown in FIG. 6(c), the transmission command unit 31 next causes the third ultrasonic sensor 21c and the sixth ultrasonic sensor 21f, which constitute the third ultrasonic sensor group 23, to simultaneously transmit ultrasonic waves. The third ultrasonic wave Us3 is reflected toward the third ultrasonic sensor 21c by hitting the obstacle P2. The third ultrasonic sensor 21c receives the reflected wave Ur3 of the third ultrasonic wave Us3. Therefore, the third ultrasonic sensor 21c is a receiving sensor, and the third ultrasonic sensor group 23 is a transmitting sensor group.

When the second ultrasonic sensor 21b and the third ultrasonic sensor 21c receive the reflected waves, the detection unit 32 provisionally detects that there is an obstacle, and sets the retransmission sensor. In Example 2, the second ultrasonic sensor 21b, which is the receiving sensor, is different from the ultrasonic sensors forming the first ultrasonic sensor group 21, which is the transmitting sensor group. For this reason, the detection unit 32 selects the first ultrasonic sensor 21a and the fourth ultrasonic sensor 21d that constitute the first ultrasonic sensor group 21, which is the transmission sensor group, from the first ultrasonic sensor 21a and the fourth ultrasonic sensor 21d that are closer to the second ultrasonic sensor 21b. 1 sets the ultrasonic sensor 21a as a retransmission sensor. The third ultrasonic sensor 21c, which is a receiving sensor, is an ultrasonic sensor that constitutes the third ultrasonic sensor group 23, which is a transmitting sensor group. Therefore, the detection unit 32 sets the third ultrasonic sensor 21c as the reception sensor.

Note that the flow after the detection unit 32 sets the retransmission sensor is the same as in the first embodiment, so the description is omitted.
Actions and effects of the third embodiment will be described. In the third embodiment, the following effects can be obtained in addition to the effects (1-1) of the first embodiment.

(3-1) The detection unit 32 sets the receiving sensor as a retransmitting sensor when the receiving sensor is an ultrasonic sensor forming a transmitting sensor group. On the other hand, if the receiving sensor is different from the ultrasonic sensors forming the transmitting sensor group, the detecting unit 32 sets the ultrasonic sensor closest to the receiving sensor among the ultrasonic sensors forming the transmitting sensor group as the re-transmitting sensor. . Therefore, even if the ultrasonic waves transmitted by the first transmission process are reflected toward an ultrasonic sensor different from the ultrasonic sensor that is the transmission source, the presence or absence of an obstacle can be detected while suppressing erroneous detection. It can be detected early.

(Fourth embodiment)
A fourth embodiment, which embodies an obstacle detection device and an obstacle detection method, will be described below. In addition, description is abbreviate|omitted about the same structure as 1st Embodiment.

As described in the second embodiment, the detection target range B may be smaller than the detectable range A depending on the situation in which obstacle detection is performed. If the obstacle is a short distance obstacle, the transmission/reception time t will be 20 ms at maximum, and if the obstacle is a long distance obstacle, the transmission/reception time t will be longer than 20 ms and 30 ms or less. In the fourth embodiment, the first transmission interval Ta is set to 20 ms in order to detect obstacles at an early stage while enabling detection of short-distance obstacles. That is, the first transmission interval Ta of the fourth embodiment: 20 ms is set shorter than the first transmission interval Ta of the first embodiment: 30 ms.

The transmission command unit 31 performs first transmission processing. In the first transmission process, the transmission command unit 31 causes the first to third ultrasonic sensor groups 21 to 23 to transmit ultrasonic waves at a first transmission interval Ta of 20 ms. The transmission command unit 31 repeats the second transmission process three times. In the first second transmission process, the transmission command unit 31 causes the retransmission sensor to transmit ultrasonic waves at the second transmission interval Tb1. The second transmission interval Tb1 is set to 20 ms, which is the same as the first transmission interval Ta. In the second transmission process performed for the second time, the transmission command unit 31 causes the retransmission sensor to transmit ultrasonic waves at the second transmission interval Tb2. The second transmission interval Tb2 is set to 18 ms, which is shorter than the first transmission interval Ta. In the third second transmission process, the transmission command unit 31 causes the retransmission sensor to transmit ultrasonic waves at the second transmission interval Tb3. The second transmission interval Tb3 is set to 22 ms, which is longer than the first transmission interval Ta.

Since the number of reception times N of the reflected waves by the retransmission sensor is equal to or greater than the determination number of times Nh, the detection unit 32 detects that there is an obstacle behind the forklift 10, and at least one of the obstacles detected is close. Determine whether the obstacle is a distance obstacle or a long distance obstacle.

The detection unit 32 obtains a first determination time Tp, which is the difference between the reception time of the reflected ultrasonic waves transmitted by the first transmission process and the transmission time of the ultrasonic waves performed before the reception of the reflected waves. do. Further, the detection unit 32 detects a second determination time Tq, which is the difference between the reception time of the reflected ultrasonic waves transmitted by the second transmission process and the transmission time of the ultrasonic waves performed before the reception of the reflected waves. to get In this embodiment, the first detection time Tx of the reflected wave in the first transmission process is set as the first determination time Tp, and the second detection time Ty of the reflected wave in the second transmission process is set as the second determination time Tq. Here, the second detection time Ty is the time required from when the retransmitting sensor transmits the ultrasonic wave to when the ultrasonic sensor receives the reflected wave of the ultrasonic wave. In other words, the second detection time Ty is the difference between the time when the ultrasonic sensor receives the reflected wave by the second transmission process and the time when the ultrasonic wave is transmitted immediately before receiving the reflected wave.

The detection unit 32 calculates a determination value ΔT=|Tp−Tq|, which is the absolute value of the difference between the first determination time Tp and the second determination time Tq, and compares the calculated determination value ΔT with the threshold value ΔTh. Based on the results, it is determined whether the obstacle is a short-distance obstacle or a long-distance obstacle. In this embodiment, the threshold ΔTh is set to 1 ms. When the determination value ΔT is equal to or less than the threshold ΔTh, the detection unit 32 determines that the obstacle is a long-distance obstacle. Note that when there are a plurality of determination values ΔT, if at least one is equal to or less than the threshold ΔTh, it is determined that at least one of the obstacles is a close-range obstacle. When the calculated determination value ΔT is larger than the threshold ΔTh, the detection unit 32 determines that at least one of the obstacles is a long-distance obstacle.

The obstacle detection method of the fourth embodiment will be described together with Examples 4-1 and 4-2.
As shown in FIGS. 10(a) to 10(f), in Example 4-1, the obstacle P41 is located 4.42 m away from the fourth ultrasonic sensor 21d and 4.42 m away from the fifth ultrasonic sensor 21e. .42m away. That is, the obstacle P41 exists outside the detection target range B and within the detectable range A of the fourth ultrasonic sensor 21d, and exists outside the detection target range B and within the detectable range A of the fifth ultrasonic sensor 21e. It is a long range obstacle that

As shown in FIGS. 12(a) to 12(f), in Example 4-2, the obstacle P42 exists at a position 1.02 m away from the fifth ultrasonic sensor 21e. In other words, the obstacle P42 is a short distance obstacle that exists within the detection target range B of the fifth ultrasonic sensor 21e.

When the forklift 10 is activated by the key switch 16, the obstacle detection device 20 starts operating.
As shown in FIG. 9, the transmission command unit 31 performs first transmission processing (steps S51 to S53). The transmission command unit 31 first causes the first ultrasonic sensor 21a and the fourth ultrasonic sensor 21d constituting the first ultrasonic sensor group 21 to simultaneously transmit ultrasonic waves (step S51). For convenience of explanation, the time at which the first ultrasonic sensor group 21 transmits ultrasonic waves is assumed to be 0 ms.

As shown in FIG. 10A, in Example 4-1, there is no obstacle within the detectable range A of the first ultrasonic sensor 21a, so the first ultrasonic wave Us1 attenuates without hitting the obstacle. Since the obstacle P41 exists within the detectable range A of the fourth ultrasonic sensor 21d, the fourth ultrasonic wave Us4 hits the obstacle P41 and is reflected toward the fifth ultrasonic sensor 21e. Therefore, the fifth ultrasonic sensor 21e receives the reflected wave Ur4 of the fourth ultrasonic wave Us4. As shown in FIG. 11, since the transmission/reception time t4 of the reflected wave Ur4 is 26 ms, the fifth ultrasonic sensor 21e receives the reflected wave Ur4 at the time when the first ultrasonic sensor group 21 transmits ultrasonic waves. The time is 26 ms after 26 ms from 0 ms.

As shown in FIG. 12A, in Example 4-2, there is no obstacle within the detectable range A of the first ultrasonic sensor 21a and the fourth ultrasonic sensor 21d. 4 Ultrasound Us4 attenuates without hitting an obstacle. Therefore, as shown in FIG. 13, the first to sixth ultrasonic sensors 21a to 21f do not receive reflected waves.

As shown in FIG. 9, the transmission command unit 31 then simultaneously transmits ultrasonic waves to the second ultrasonic sensor 21b and the fifth ultrasonic sensor 21e that constitute the second ultrasonic sensor group 22 at the first transmission interval Ta. It is transmitted (step S52). As shown in FIGS. 11 and 13, the second ultrasonic sensor 21b and the fifth ultrasonic sensor 21e emit ultrasonic waves at time 20 ms after 20 ms from time 0 ms when the first ultrasonic sensor group 21 transmits ultrasonic waves. Send. Therefore, in Example 4-1, the fifth ultrasonic sensor 21e receives the reflected wave Ur4 of the fourth ultrasonic wave Us4 after the second ultrasonic sensor group 22 has transmitted the ultrasonic wave.

As shown in FIG. 10B, in Example 4-1, there is no obstacle within the detectable range A of the second ultrasonic sensor 21b, so the second ultrasonic wave Us2 attenuates without hitting the obstacle. Since the obstacle P41 exists within the detectable range A of the fifth ultrasonic sensor 21e, the fifth ultrasonic wave Us5 hits the obstacle P41 and is reflected toward the fifth ultrasonic sensor 21e. Therefore, the fifth ultrasonic sensor 21e receives the reflected wave Ur5 of the fifth ultrasonic wave Us5. As shown in FIG. 11, since the transmission/reception time t5 of the reflected wave Ur5 is 26 ms, the fifth ultrasonic sensor 21e receives the reflected wave Ur5 at the time when the second ultrasonic sensor group 22 transmits ultrasonic waves. The time is 46 ms after 26 ms from 20 ms.

As shown in FIG. 12B, in Example 4-2, there is no obstacle within the detectable range A of the second ultrasonic sensor 21b, so the second ultrasonic wave Us2 attenuates without hitting the obstacle. Since the obstacle P42 exists within the detectable range A of the fifth ultrasonic sensor 21e, the fifth ultrasonic wave Us5 hits the obstacle P42 and is reflected toward the fifth ultrasonic sensor 21e. Therefore, the fifth ultrasonic sensor 21e receives the reflected wave Ur5 of the fifth ultrasonic wave Us5. As shown in FIG. 13, since the transmission/reception time t5 of the reflected wave Ur5 is 6 ms, the fifth ultrasonic sensor 21e receives the reflected wave Ur5 at the time when the second ultrasonic sensor group 22 transmits the ultrasonic wave. The time is 26 ms after 6 ms from 20 ms.

As shown in FIG. 9, the transmission command unit 31 then simultaneously transmits ultrasonic waves to the third ultrasonic sensor 21c and the sixth ultrasonic sensor 21f that constitute the third ultrasonic sensor group 23 at the first transmission interval Ta. (step S53). As shown in FIGS. 11 and 13, the third ultrasonic sensor 21c and the sixth ultrasonic sensor 21f emit ultrasonic waves at 40 ms after 20 ms from the time 20 ms when the second ultrasonic sensor group 22 transmits ultrasonic waves. Send. Therefore, in example 4-1, after the third ultrasonic sensor group 23 transmits ultrasonic waves, the fifth ultrasonic sensor 21e receives the reflected wave Ur5 of the fifth ultrasonic wave Us5.

As shown in FIGS. 10(c) and 12(c), in Examples 4-1 and 4-2, there is an obstacle within the detectable range A of the third ultrasonic sensor 21c and the sixth ultrasonic sensor 21f. , the third ultrasonic wave Us3 and the sixth ultrasonic wave Us6 are attenuated without hitting the obstacle.

As shown in FIG. 9, when the first to sixth ultrasonic sensors 21a to 21f do not receive the reflected wave by the first transmission process (NO in step S54), the detection unit 32 performs the main detection that there is no obstacle. (step S55). When at least one of the first to sixth ultrasonic sensors 21a to 21f receives the reflected wave by the first transmission process (YES in step S54), the detection unit 32 provisionally detects that there is an obstacle (step S56), The receiving sensor is set as a retransmitting sensor (step S57).

In example 4-1, since the fifth ultrasonic sensor 21e receives the reflected waves Ur4 and Ur5, the detection unit 32 tentatively detects that there is an obstacle, and sets the fifth ultrasonic sensor 21e as a retransmitting sensor. . In example 4-2, since the fifth ultrasonic sensor 21e receives the reflected wave Ur5, the detection unit 32 tentatively detects that there is an obstacle, and sets the fifth ultrasonic sensor 21e as a retransmitting sensor.

Next, the transmission command unit 31 performs a second transmission process for causing the retransmission sensor to transmit ultrasonic waves. The transmission command unit 31 repeats the second transmission process three times (steps S58 to S60). In the first second transmission process, the transmission command unit 31 causes the retransmission sensor to transmit ultrasonic waves at the second transmission interval Tb1 (step S58). In the second transmission process performed for the second time, the transmission command unit 31 causes the retransmission sensor to transmit ultrasonic waves at the second transmission interval Tb2 (step S59). In the third second transmission process, the transmission command unit 31 causes the retransmission sensor to transmit ultrasonic waves at the second transmission interval Tb3 (step S60).

In Examples 4-1 and 4-2, the transmission command unit 31 causes the fifth ultrasonic sensor 21e to transmit the fifth ultrasonic wave Us51 at the second transmission interval Tb1 as the first second transmission process. As shown in FIGS. 11 and 13, the fifth ultrasonic sensor 21e transmits the fifth ultrasonic wave Us51 at time 60 ms after 20 ms from time 40 ms when the third ultrasonic sensor group 23 transmitted the ultrasonic wave.

As shown in FIG. 10(d), in Example 4-1, the fifth ultrasonic wave Us51 hits the obstacle P41 and is reflected toward the fifth ultrasonic sensor 21e. Therefore, the fifth ultrasonic sensor 21e receives the reflected wave Ur51 of the fifth ultrasonic wave Us51. As shown in FIG. 11, the transmission/reception time t51 of the reflected wave Ur51 is 26 ms. The time is 86 ms, which is 26 ms after the time 60 ms.

As shown in FIG. 12(d), in Example 4-2, the fifth ultrasonic wave Us51 hits the obstacle P42 and is reflected toward the fifth ultrasonic sensor 21e. Therefore, the fifth ultrasonic sensor 21e receives the reflected wave Ur51 of the fifth ultrasonic wave Us51. As shown in FIG. 13, the transmission/reception time t51 of the reflected wave Ur51 is 6 ms. The time is 66 ms, which is 6 ms after the time 60 ms.

As shown in FIG. 9, in Examples 4-1 and 4-2, the transmission command unit 31 transmits the fifth ultrasonic wave Us52 to the fifth ultrasonic sensor 21e at the second transmission interval Tb2 as the second transmission process for the second time. to be sent. As shown in FIGS. 11 and 13, the fifth ultrasonic sensor 21e transmits the fifth ultrasonic wave Us52 at time 78 ms after 18 ms from the time 60 ms when the fifth ultrasonic sensor 21e transmitted the fifth ultrasonic wave Us51. . Therefore, in Example 4-1, after the fifth ultrasonic sensor 21e transmits the fifth ultrasonic wave Us52, the fifth ultrasonic sensor 21e receives the reflected wave Ur51.

As shown in FIG. 10(e), in Example 4-1, the fifth ultrasonic wave Us52 hits the obstacle P41 and is reflected toward the fifth ultrasonic sensor 21e. Therefore, the fifth ultrasonic sensor 21e receives the reflected wave Ur52 of the fifth ultrasonic wave Us52. As shown in FIG. 11, the transmission/reception time t52 of the reflected wave Ur52 is 26 ms. The time is 104 ms, which is 26 ms after the time 78 ms.

As shown in FIG. 12(e), in Example 4-2, the fifth ultrasonic wave Us52 hits the obstacle P42 and is reflected toward the fifth ultrasonic sensor 21e. Therefore, the fifth ultrasonic sensor 21e receives the reflected wave Ur52 of the fifth ultrasonic wave Us52. As shown in FIG. 13, the transmission/reception time t52 of the reflected wave Ur52 is 6 ms. The time is 84 ms, which is 6 ms after the time 78 ms.

In Examples 4-1 and 4-2, the transmission command unit 31 causes the fifth ultrasonic sensor 21e to transmit the fifth ultrasonic wave Us53 at the second transmission interval Tb3 as the third second transmission process. As shown in FIGS. 11 and 13, the fifth ultrasonic sensor 21e transmits the fifth ultrasonic wave Us53 at 100 ms after 22 ms from the time 78 ms when the fifth ultrasonic sensor 21e transmitted the fifth ultrasonic wave Us52. . Therefore, in example 4-1, after the fifth ultrasonic sensor 21e transmits the fifth ultrasonic wave Us53, the fifth ultrasonic sensor 21e receives the reflected wave Ur52.

As shown in FIG. 10(f), in Example 4-1, the fifth ultrasonic wave Us53 hits the obstacle P41 and is reflected toward the fifth ultrasonic sensor 21e. Therefore, the fifth ultrasonic sensor 21e receives the reflected wave Ur53 of the fifth ultrasonic wave Us53. As shown in FIG. 11, the transmission/reception time t53 of the reflected wave Ur53 is 26 ms. The time is 126 ms, which is 26 ms after the time 100 ms.

As shown in FIG. 12(f), in Example 4-2, the fifth ultrasonic wave Us53 hits the obstacle P42 and is reflected toward the fifth ultrasonic sensor 21e. Therefore, the fifth ultrasonic sensor 21e receives the reflected wave Ur53 of the fifth ultrasonic wave Us53. As shown in FIG. 13, the transmission/reception time t53 of the reflected wave Ur53 is 6 ms. The time is 106 ms, which is 6 ms after the time 100 ms.

As shown in FIG. 9, the detection unit 32 acquires the number of times N of reception of the reflected wave by the second transmission process for three times for the retransmission sensor (step S61). In Example 4-1, the detection unit 32 acquires the number of reception times N5 of the reflected wave by the fifth ultrasonic sensor 21e: 2 times. In Example 4-2, the detection unit 32 acquires the number of reception times N5 of the reflected wave by the fifth ultrasonic sensor 21e: 3 times.

When the number of receptions N of the reflected waves by the retransmission sensor is equal to or greater than the threshold value Nh (YES in step S62), the detection unit 32 actually detects that there is an obstacle behind the forklift 10 (step S63). When the number N of receptions of the reflected waves by the retransmission sensor is not equal to or greater than the determination number Nh (NO in step S62), that is, when the number N of receptions of the reflected waves by the retransmission sensor is less than the determination number Nh, the forklift 10 It is actually detected that there is no obstacle within the detectable range A of the first to sixth ultrasonic sensors 21a to 21f in the rear (step S64).

In Example 4-1, the number N5 of reception of reflected waves by the fifth ultrasonic sensor 21e: 2 is equal to the number of determinations Nh: 2 or more (Nh≦N5). Therefore, the detection unit 32 actually detects that there is an obstacle behind the forklift 10 . In Example 4-2, the number of times N5 of reception of the reflected wave by the fifth ultrasonic sensor 21e: 3 times is equal to the number of times of determination Nh: 2 times or more (Nh≦N5). Therefore, the detection unit 32 actually detects that there is an obstacle behind the forklift 10 .

The detection unit 32 acquires the first determination time Tp and the second determination time Tq (step S65). As described above, in the present embodiment, the first detection time Tx is the first determination time Tp, and the second detection time Ty is the second determination time Tq. Therefore, the detection unit 32 obtains the first judgment time Tp and the second judgment time Tq by measuring the first detection time Tx and the second detection time Ty.

In Example 4-1, the detector 32 measures the first detection time Tx1: 6 ms for the reflected wave Ur4 and the first detection time Tx2: 6 ms for the reflected wave Ur5. The detection unit 32 also measures a second detection time Ty1 of 8 ms for the reflected wave Ur51 and a second detection time Ty2 of 4 ms for the reflected wave Ur52.

In Example 4-2, the detector 32 measures the first detection time Tx1: 6 ms of the reflected wave Ur5. The detection unit 32 also measures a second detection time Ty1 of 6 ms for the reflected wave Ur51, a second detection time Ty2 of 6 ms for the reflected wave Ur52, and a second detection time Ty3 of 6 ms for the reflected wave Ur53.

The detection unit 32 calculates a determination value ΔT=|Tp−Tq|, which is the difference between the first determination time Tp and the second determination time Tq (step S66). In this embodiment, the detection unit 32 calculates the determination value ΔT=|Tx−Ty|, which is the difference between the first detection time Tx and the second detection time Ty. When the calculated determination value ΔT is equal to or less than the threshold ΔTh (YES in step S67), the detection unit 32 determines that the obstacle is a short-range obstacle (step S68). If the determination value ΔT is not equal to or less than the threshold ΔTh (NO in step S67), that is, if the determination value ΔT is greater than the threshold ΔTh, the detection unit 32 determines that the obstacle is a long-distance obstacle (step S69).

In Example 4-1, the first detection times Tx1 and Tx2 have the same length. Therefore, the detection unit 32 calculates the determination value ΔT1=|Tx1−Ty1| and the determination value ΔT2=|Tx1−Ty2|. Each of the judgment values ΔT1 and ΔT2 is 2 ms. Since each of the determination values ΔT1 and ΔT2 is greater than the threshold ΔTh, the detection unit 32 determines that the obstacle is a long-distance obstacle.

In example 4-2, the detection unit 32 calculates the determination value ΔT1=|Tx1−Ty1|, the determination value ΔT2=|Tx1−Ty2|, and the determination value ΔT3=|Tx1−Ty3|. Each of the judgment values ΔT1, ΔT2, ΔT3 is 0 ms. Since each of the determination values ΔT1, ΔT2, and ΔT3 is equal to or less than the threshold ΔTh, the detection unit 32 determines that the obstacle is a short-distance obstacle.

The operation of the fourth embodiment will be described.
As the reflected wave received by the fifth ultrasonic sensor 21e, the ultrasonic wave transmitted before the ultrasonic wave transmitted immediately before the reflected wave is received is reflected by a distant obstacle as in Example 4-1. and the case where the ultrasonic waves transmitted immediately before the reflected waves are received are reflected by a short distance obstacle as in Example 4-2.

In the case of example 4-1, the timing at which the receiving sensor receives the reflected wave is determined by the timing of the transmission of the ultrasonic wave that is performed two times before the reception of the reflected wave. Therefore, if the second transmission interval Tb2 in the second transmission process for the second time is made different from the first transmission interval Ta, the first detection time Tx1 and the second detection time Ty1 will be different. Therefore, the determination value ΔT1 becomes larger than the threshold ΔTh. Also, if the second transmission interval Tb3 in the third second transmission process is made different from the first transmission interval Ta, the first detection time Tx1 and the second detection time Ty2 will be different. Therefore, the determination value ΔT2 becomes larger than the threshold ΔTh.

In the case of example 4-2, the timing at which the receiving sensor receives the reflected wave is determined by the timing at which the ultrasonic wave is transmitted immediately before receiving the reflected wave. Therefore, even if the second transmission interval Tb2 in the second transmission process for the second time is made different from the first transmission interval Ta, the first detection time Tx1 and the second detection time Ty1 are substantially the same. Therefore, the determination value ΔT1 becomes equal to or less than the threshold ΔTh. Also, even if the second transmission interval Tb3 in the third second transmission process is made different from the first transmission interval Ta, the first detection time Tx1 and the second detection time Ty2 are substantially the same. Therefore, the determination value ΔT2 becomes equal to or less than the threshold ΔTh.

From the above, it is possible to determine whether the detected obstacle is a close-range obstacle or a close-range obstacle based on the result of comparison between the determination value ΔT and the threshold value ΔTh.
Actions and effects of the fourth embodiment will be described. In the fourth embodiment, the following effects can be obtained in addition to the effects (1-1) of the first embodiment.

(4-1) The reflected waves received by each of the ultrasonic sensors 21a to 21f include the case where the ultrasonic wave transmitted immediately before the reflected wave is reflected by a short-range obstacle, and the case where the ultrasonic wave is reflected immediately before the reflected wave is received. It is conceivable that an ultrasonic wave that was transmitted earlier than the ultrasonic wave that was transmitted to the target was reflected by a distant obstacle. In the former case, the timing of receiving the reflected wave is determined by the timing of the transmission of the ultrasonic wave immediately before receiving the reflected wave. It is determined by the timing of the transmission of ultrasonic waves that precedes the transmission. Therefore, by making the first transmission interval Ta different from the second transmission interval Tb, the comparison result between the judgment value ΔT, which is the difference between the first judgment time Tp and the second judgment time Tq, and the threshold ΔTh is The former case differs from the latter case. Therefore, it can be determined whether the detected obstacle is a short-distance obstacle or a long-distance obstacle.

This embodiment can be implemented with the following modifications. This embodiment and modifications can be implemented in combination with each other within a technically consistent range.
O The number of ultrasonic sensor groups included in the obstacle detection device 20 is not limited to three, and may be changed as appropriate as long as the number is two or more.

O The number of ultrasonic sensors constituting the ultrasonic sensor group is not limited to two, and may be three or more. Also, the number of ultrasonic sensors forming an ultrasonic sensor group may be different for each ultrasonic sensor group.

○ In the first transmission process, the order in which the transmission command unit 31 switches the first to third ultrasonic sensors 21a to 21c is limited to the first ultrasonic sensor 21a→second ultrasonic sensor 21b→third ultrasonic sensor 21c. may be changed as appropriate.

O The number of times the transmission command unit 31 performs the first transmission process is not limited to one. The transmission command unit 31 may continuously perform the first transmission process multiple times. In this case, erroneous detection can be suppressed more than when the transmission command unit 31 performs the first transmission process once. The number of times the first transmission process is performed is set, for example, in consideration of the accuracy and time required for provisional detection of obstacles.

O The number of times the transmission command unit 31 repeats the second transmission process is not limited to three times. The transmission command unit 31 may perform the second transmission process only once, may repeat it twice, or may repeat it four times or more. The number of times the second transmission process is performed is set, for example, in consideration of the accuracy and time required for actual detection of the presence or absence of an obstacle.

○ The detection unit 32 acquires the total Ns of the number of receptions of the reflected waves by the first transmission process and the number of receptions of the reflected waves by the second transmission process, and compares the total number of receptions Ns with the number of determinations Nh. Based on this, the presence or absence of an obstacle may be fully detected.

(circle) in 4th Embodiment, you may change the definition of the 1st time for determination Tp and the 2nd time for determination Tq. For example, Ta+Tx, which is the sum of the first transmission interval Ta and the first detection time Tx, is set as the first determination time Tp, and Tb+Ty, which is the sum of the second transmission interval Tb and the second detection time Ty, is set as the second determination time Tp. It may be time Tq. In this case, when the determination value ΔT is equal to or less than the threshold ΔTh (YES in step S67), the detection unit 32 determines that the obstacle is a long-distance obstacle (step S69). (NO in step S67), the obstacle is determined to be a short distance obstacle (step S68).

○ In the fourth embodiment, if at least one of the plurality of determination values ΔT is equal to or less than the threshold ΔTh, it is determined that the obstacle is at a short distance. However, the determination conditions may be changed as appropriate. For example, the detection unit 32 may determine that the obstacle is a close-range obstacle when a majority of the plurality of determination values ΔT is equal to or less than the threshold ΔTh.

○ The first to sixth ultrasonic sensors 21a to 21f may be attached to the counterweight 13 by inserting the ultrasonic sensors into holes formed in the counterweight 13, or may be attached to a pillar or the like via a bracket or the like. It may be attached to the side frame, the counterweight 13, or the like by screwing.

O The ultrasonic sensors may not be attached to all the first to third surfaces 13a to 13c of the rear end surface of the counterweight 13. For example, the ultrasonic sensor may be attached only to the first surface 13a.

O The direction in which the first to sixth ultrasonic sensors 21a to 21f are arranged is not limited to the horizontal direction. The first to sixth ultrasonic sensors 21a to 21f may be arranged vertically, for example.

O The obstacle detection device 20 may detect an obstacle present 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 ultrasonic waves are transmitted in the direction in which the obstacle is to be detected. The obstacle detection device 20 may detect obstacles in any of the forward, rearward, and lateral directions, or may detect obstacles in a plurality of directions. good.

O Each of the ultrasonic sensors 21a to 21f may be an ultrasonic sensor comprising a piezoelectric transducer for transmission and a piezoelectric transducer for reception. In this case, each of the ultrasonic sensors 21a to 21f can receive reflected waves while transmitting ultrasonic waves.

(circle) the specific numerical value of the detectable range A may be suitably changed according to the mobile body in which the obstacle detection apparatus 20 is mounted, or the obstacle to detect, for example.
○ The specific numerical value of the detection target range B varies depending on the specifications of each of the ultrasonic sensors 21a to 21f, for example.

o The speed of sound V may be corrected, for example, by the temperature and medium of the environment in which obstacle detection is performed.
(circle) the specific numerical value of the determination frequency|count Nh may be suitably changed according to the precision calculated|required by the main detection of the presence or absence of an obstacle, for example.

O The determination distance Lh may be set longer than the detection target range B: 3.40 m, for example, in consideration of an error in transmission/reception time of ultrasonic waves.
O The threshold value ΔTh may be appropriately changed according to, for example, the accuracy required for determining whether a long-distance obstacle or a short-distance obstacle is determined.

○ In the first to third embodiments, specific numerical values of the first transmission interval Ta and the second transmission interval Tb may be appropriately changed according to, for example, the obstacle detection status.
○ In the fourth embodiment, specific numerical values of the second transmission intervals Tb1 to Tb3 may be changed as appropriate. However, the second transmission intervals Tb2 and Tb3 are different from the first transmission interval Ta and different from the sum Ta+Tx of the first transmission interval Ta and the first detection time Tx.

O The control ECU 30 may be integrated with the main controller 17 .
O The threshold value of the received intensity of the reflected wave for determining whether to transmit the received signal to the detector 32 may be variable.

O The forklift 10 may be an automatically operated forklift.
O The obstacle detection device 20 may be mounted on any moving body that requires obstacle detection, such as a passenger car, an industrial vehicle such as a towing tractor, and an autonomously moving robot.

20... Obstacle detection device 21a to 21f... First to sixth ultrasonic sensors as ultrasonic sensors 21 to 23... First to third ultrasonic sensor groups as ultrasonic sensor groups 31... Transmission command unit , 32 . . . Detector.

Claims (5)

a plurality of ultrasonic sensor groups composed of two or more ultrasonic sensors having a transmission function for transmitting ultrasonic waves and a reception function for receiving reflected waves reflected by obstacles;
a transmission command unit that controls transmission of ultrasonic waves by the ultrasonic sensor;
a detection unit that detects the presence or absence of the obstacle from the reception result of the reflected wave by the ultrasonic sensor;
An obstacle detection device comprising
The transmission command unit,
By simultaneously transmitting ultrasonic waves to two or more ultrasonic sensors constituting the ultrasonic sensor group while switching the plurality of ultrasonic sensor groups, from all the ultrasonic sensors to each ultrasonic sensor group in order a first transmission process for transmitting ultrasonic waves ;
When at least one of the plurality of ultrasonic sensors receives a reflected wave in the first transmission process and the detection unit provisionally detects that there is an obstacle, the first ultrasonic sensor among the plurality of ultrasonic sensors a second transmission process for simultaneously transmitting ultrasonic waves from all the ultrasonic sensors set as retransmission sensors based on the reception results of the reflected waves by the transmission process ;
The detection unit actually detects the presence or absence of an obstacle based on the number of times the reflected wave is received by the second transmission process ,
The transmission command unit performs a process of simultaneously transmitting ultrasonic waves from all the ultrasonic sensors set as the retransmission sensors in the second transmission process after the first transmission process. detection device. The obstacle detection device according to claim 1, wherein the transmission command unit continuously performs the first transmission process a plurality of times. When the ultrasonic sensor that received the reflected wave by the first transmission process is defined as a receiving sensor, and the ultrasonic sensor group that transmits the ultrasonic wave immediately before the receiving sensor receives the reflected wave is defined as a transmitting sensor group,
The detection distance calculated based on the time required for the transmission sensor group to transmit the ultrasonic wave until the reception sensor receives the reflected wave is equal to or less than the judgment distance set based on the detection target range of the obstacle. , the transmission command unit performs the second transmission process and the detection unit actually detects the presence or absence of an obstacle;
3. The obstacle detection device according to claim 1, wherein when the detection distance is longer than the judgment distance, the detection unit actually detects that there is no obstacle. The transmission command unit performs the second transmission process a plurality of times, and sets the transmission interval of the ultrasonic waves by the retransmission sensor in the second transmission process to the transmission interval of the ultrasonic waves by the ultrasonic sensor group in the first transmission process. be different from the transmission interval,
The detection unit includes a first determination time, which is the difference between the reception time of the reflected ultrasonic wave transmitted in the first transmission process and the transmission time of the ultrasonic wave performed before the reception of the reflected wave, Acquiring a second determination time, which is the difference between the reception time of the reflected ultrasonic waves transmitted by the second transmission process and the transmission time of the ultrasonic waves performed before the reception of the reflected waves,
It is determined whether the obstacle is a short distance obstacle or a long distance obstacle based on a result of comparison between a threshold value and a judgment value, which is the difference between the first judgment time and the second judgment time. The obstacle detection device according to claim 1 or 2. A plurality of ultrasonic sensors configured by two or more ultrasonic sensors having a transmission function to transmit ultrasonic waves and a reception function to receive reflected waves reflected by obstacles , and whose transmission of ultrasonic waves is controlled by a transmission command unit An obstacle detection method in which a detection unit detects the presence or absence of an obstacle from a reception result of a reflected wave by a group of sound wave sensors,
The transmission command unit simultaneously transmits ultrasonic waves to two or more ultrasonic sensors constituting the ultrasonic sensor group while switching the ultrasonic sensor group , so that all the ultrasonic sensors from the ultrasonic sensor A first step of performing a first transmission process for sequentially transmitting ultrasonic waves for each group ;
When the transmission command unit temporarily detects that there is an obstacle because at least one of the plurality of ultrasonic sensors receives a reflected wave in the first transmission process, the plurality of ultrasonic sensors Among them, a second step of performing a second transmission process for simultaneously transmitting ultrasonic waves from all ultrasonic sensors set as retransmission sensors based on the reception result of the reflected wave by the first transmission process;
a third step in which the detection unit performs actual detection of the presence or absence of an obstacle based on the number of times the reflected wave is received in the second transmission process;
has
The obstacle detection method, wherein the process of simultaneously transmitting ultrasonic waves from all the ultrasonic sensors set as the retransmission sensors in the second step is performed after the first transmission process.

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