JP7533259B2 - Device and method for detecting obstacles behind a towing vehicle - Google Patents

Description

This invention relates to a rear obstacle detection device for a towing vehicle and a rear obstacle detection method for a towing vehicle.

In recent years, automated guided vehicles that transport cargo such as products and parts have become common in manufacturing plants and logistics warehouses, leading to more efficient and labor-saving cargo transportation. Automated guided vehicles that transport cargo are often equipped with obstacle sensors that detect obstacles in the direction of travel (see, for example, Patent Document 1). Therefore, when an obstacle is present in the direction of travel, a controller equipped in the automated guided vehicle, when the obstacle sensor detects the obstacle, will, for example, control the automated guided vehicle to stop traveling or control the vehicle to change course so as not to interfere with the obstacle.

On the other hand, the transportation of cargo using a towing vehicle is also widely known. In the transportation of cargo using a towing vehicle, the towing vehicle tows a group of carriages carrying cargo. In this case, when the towing vehicle makes a turn, the travel path of the towing vehicle and the travel path of the group of carriages differ. Specifically, the travel path of the group of carriages being towed passes on the inside of the curve of the travel path of the towing vehicle. Incidentally, the rearmost carriage passes on the inside.

Japanese Unexamined Patent Publication No. 2-302805

Therefore, when transporting cargo using an autonomously driven unmanned towing vehicle, it is necessary to detect not only obstacles in the direction of travel, but also obstacles that may interfere with the group of carts being towed. However, Patent Document 1 only detects obstacles in front of the unmanned guided vehicle and does not disclose the detection of obstacles behind the towing vehicle when it is traveling along a curve.

On the other hand, it is possible to provide obstacle detection sensors to detect obstacles on each bogie towed by the towing vehicle, but this would require connecting electrical wiring each time the bogies are coupled to each other and to the towing vehicle, and disconnecting the electrical wiring when the bogies are detached, resulting in a problem of reduced work efficiency.

The present invention was made in consideration of the above problems, and the object of the present invention is to provide a rear obstacle detection device for a towing vehicle and a rear obstacle detection method for a towing vehicle that can reliably detect obstacles that may interfere with a group of bogies when traveling around a curve.

In order to solve the above problems, the present invention provides a rear obstacle detection device for a towing vehicle that includes a towing vehicle and a group of bogies towed by the towing vehicle and detects obstacles rear of the towing vehicle, the device comprising: a laser sensor provided at the rear of a side of the towing vehicle and including the sides of the group of bogies in a scanning area of laser light; a front reflector provided at the frontmost part of the side of the group of bogies and detectable as a characteristic point by the laser sensor; a rear reflector provided at the rearmost part of the side of the group of bogies and detectable as a characteristic point by the laser sensor; a specific detection area setting unit that sets a specific detection area defined by the front reflector and rear reflector detected by the laser sensor and the laser sensor; and an obstacle discrimination unit that discriminates an object as an obstacle when the laser sensor detects an object in the specific detection area.

In the present invention, when the towing vehicle travels around a curve so that the front reflector and rear reflector are on the inside of the curve, the laser sensor detects the front reflector and rear reflector, and the specific detection area setting unit sets a specific detection area defined by the laser sensor, the front reflector, and the rear reflector. The specific detection area is an area that includes the planned route along which the group of trolleys will travel on the side of the group of trolleys, and the obstacle discrimination unit discriminates an object as an obstacle when the laser sensor detects an object in the specific detection area. Therefore, by discriminating an object in the specific detection area as an obstacle, it is possible to reliably detect obstacles that may interfere with the group of trolleys when traveling around a curve.

Furthermore, in the above-described rear obstacle detection device for a towing vehicle, the towing vehicle may be configured to include a travel drive unit and a travel control unit that controls the travel drive unit, and the travel control unit may be configured to control the travel drive unit so as to stop the towing vehicle when the obstacle discrimination unit discriminates the object as an obstacle.
In this case, when the obstacle discrimination unit discriminates an object detected by the laser sensor in a specific detection area as an obstacle, the travel control unit controls the travel drive unit so that the towing vehicle stops, thereby preventing interference between the group of carts and the obstacle.

Furthermore, in the above-described rear obstacle detection device for a towing vehicle, the towing vehicle may be configured to include a feature point discrimination unit that discriminates an object reflecting laser light from the laser sensor as a feature point when the reflectance of the reflected laser light received by the laser sensor is equal to or greater than a threshold, and the front reflector and the rear reflector may have reflecting units that reflect the laser light from the laser sensor so that the reflectance of the reflected laser light received by the laser sensor is equal to or greater than a threshold.
In this case, the reflecting portions of the front reflector and the rear reflector reflect the laser light from the laser sensor so that the reflectance of the reflected laser light received by the laser sensor is equal to or greater than a threshold value, and therefore the feature point determination unit can reliably determine the front reflector and the rear reflector as feature points by the laser sensor receiving the reflected laser light from the front reflector and the rear reflector.

In the above-described rear obstacle detection device for a towing vehicle, when the characteristic point discrimination section discriminates only one of the characteristic points, the specific detection area setting section may be configured not to set the specific detection area.
In this case, when the feature point discrimination unit discriminates that there is only one feature point, the specific detection area setting unit does not set the specific detection area, since it determines that the towing vehicle and the group of carts are traveling straight ahead. Therefore, when traveling straight ahead, processing to detect obstacles behind the towing vehicle is not performed, and the load on the obstacle discrimination unit can be reduced.

Furthermore, in the above-mentioned rear obstacle detection device for a towing vehicle, when the rear reflector is not detected as a feature point by the laser sensor after the obstacle discrimination unit discriminates the object as an obstacle, the specific detection area setting unit may be configured to maintain the specific detection area for a fixed period of time.
In this case, even if an object detected in the specific detection area blocks the laser light so that the laser sensor is no longer able to detect a rear reflector, the specific detection area is not immediately reduced or eliminated, and the object can be detected as an obstacle for a certain period of time.

Furthermore, the above-mentioned rear obstacle detection device for a towing vehicle may be configured to include a tilting mechanism that enables the front reflector and the rear reflector to be tilted relative to the group of trolleys, and a biasing member that enables the front reflector and the rear reflector in a tilted state to be returned to their original positions before tilting.
In this case, by making the front reflector and the rear reflector tiltable relative to the carriages of the carriage group, even if the front reflector and the rear reflector interfere with an object, the front reflector and the rear reflector themselves are unlikely to become an obstacle to the interfering object. In addition, since the biasing member allows the tilted front reflector and the rear reflector to return to their original positions before tilting, the function as the front reflector and the rear reflector can be maintained.

In the above-described rear obstacle detection device for a towing vehicle, the reflecting member may be configured to have a reflecting surface that is a convex curved surface.
In this case, the laser light from the laser sensor can be reliably reflected toward the laser sensor regardless of the curvature of the curve on which the towing vehicle and the group of carriages are traveling.

Moreover, the present invention provides a method for detecting obstacles behind a towing vehicle towing a group of carts, the method comprising: a laser sensor provided at the rear of a side of the towing vehicle and including the sides of the group of carts in a scanning area of laser light; a front reflector provided at the frontmost part of the side of the group of carts and detectable as a characteristic point by the laser sensor; and a rear reflector provided at the rearmost part of the side of the group of carts and detectable as a characteristic point by the laser sensor; and when the laser sensor detects the front reflector and the rear reflector, a specific detection area partitioned by at least the front reflector, the rear reflector, and the laser sensor is set, and when an object is detected in the specific detection area, the object is discriminated as an obstacle.
According to the present invention, it is possible to reliably detect an obstacle that may interfere with a group of bogies when traveling around a curve.

The present invention provides a rear obstacle detection device for a towing vehicle and a rear obstacle detection method for a towing vehicle that can reliably detect obstacles that may interfere with a group of bogies when traveling around a curve.

1 is a schematic side view of a rear obstacle detection device for a towing vehicle according to a first embodiment. 1 is a schematic plan view of a rear obstacle detection device for a towing vehicle according to a first embodiment; 1 is a control block diagram of a rear obstacle detection device for a towing vehicle according to a first embodiment. FIG. FIG. 2A is a perspective view showing a front reflector, and FIG. 2B is a perspective view showing a rear reflector. 4 is a flowchart showing a procedure for a rear obstacle detection device to detect a rear obstacle. FIG. FIG. 2 is a plan view of a towing vehicle towing a group of bogies when the towing vehicle is traveling around a curve. FIG. 11 is a schematic plan view of a rear obstacle detection device for a towing vehicle according to a second embodiment.

First Embodiment
Hereinafter, a rear obstacle detection device and a rear obstacle detection method for a towing vehicle according to a first embodiment will be described with reference to the drawings. The towing vehicle of this embodiment is an autonomous small towing vehicle capable of autonomously driving while estimating its own position and traveling unmanned, and travels by autonomously towing a plurality of dollies on which loads can be placed.

As shown in Figures 1 and 2, the rear obstacle detection device for a towing vehicle (hereinafter referred to as the "rear obstacle detection device") 10 comprises a towing vehicle 11 and a number of bogies 12 towed by the towing vehicle 11. The towing vehicle 11 has steering wheels 14 as front wheels at the front of its body 13. The rear of the body 13 has a pair of left and right drive wheels 15 as rear wheels. The body 13 comprises a drive motor 16 that drives the drive wheels 15, a battery 17 that stores power to drive the drive motor 16, and a control device 18 that controls each part of the towing vehicle 11.

The towing vehicle 11 has an automatic steering mechanism 19 that automatically steers the steering wheels 14. The automatic steering mechanism 19 is controlled by a control device 18 to steer the steering wheels 14 so that the towing vehicle 11 travels along a route to a preset destination. The towing vehicle 11 shown in FIG. 1 has a driver's seat, but travels unmanned by automatic driving while estimating its own position. The drive wheels 15 are driven by a drive motor 16. The drive motor 16 is driven by a supply of power from a battery 17 and is controlled by a control device 18. The drive motor 16 corresponds to a travel drive unit, and the control device 18 corresponds to a travel control unit. The battery 17 is capable of charging and discharging, and also has a function of storing the power generated during regeneration of the drive motor 16.

As shown in FIG. 3, the control device 18 has a central processing unit (CPU) 20, a memory unit 21, and a motor drive unit 22. The central processing unit 20 executes various programs and performs processing required for automatic driving of the towing vehicle 11. The memory unit 21 stores various programs and data. The motor drive unit 22 has a drive circuit (not shown) for controlling the drive motor 16. In addition, the control device 18 performs processing required for the rear obstacle detection device 10 to detect obstacles behind the towing vehicle 11.

As shown in FIG. 2, a laser sensor 25 is provided at the rear of each of the left and right side surfaces 32 of the body 13 of the towing vehicle 11. The laser sensor 25 can set a laser light scanning area at the rear of the body 13, and the laser light scanning area is fan-shaped in a plan view. The maximum scanning angle θ at which the laser light can scan is, for example, 120 degrees. The maximum scanning distance is set to be longer than the rear end of the maximum number of carts 12 that can be connected to the towing vehicle 11. For example, when the maximum number of carts 12 to be towed is six, the maximum scanning distance is 30 m, but the maximum scanning distance can be adjusted.

The laser sensor 25 is attached to the vehicle body 13 so that it is positioned lower than the top end of the bogie 12. Therefore, when the towing vehicle 11 is traveling straight, the scanning area of the laser light is narrowed by an amount corresponding to the scanning angle blocked by the bogie 12. In addition, the scanning area of the laser light varies depending on whether the towing vehicle 11 and the bogie 12 are traveling straight or curved. When distinguishing between the left and right laser sensors 25, they are referred to as the right laser sensor 25R and the left laser sensor 25L.

When an object is present in the scanning area of the laser light, the laser light of the laser sensor 25 is reflected by the object, and the laser sensor 25 receives the reflected laser light reflected by the object, making it possible to detect the object. By receiving the reflected laser light, the laser sensor 25 also acquires and outputs information such as the distance and direction to the object, as well as the reflectance of the reflected laser light. The laser sensor 25 is connected to the control device 18, and the output of the laser sensor 25 is transmitted to the control device 18.

The towing vehicle 11 is provided at the front of the vehicle with an obstacle sensor 26 that detects obstacles ahead in the direction of travel. The obstacle sensor 26 may be a laser sensor that detects objects by scanning laser light, similar to the laser sensor 25, or a stereo camera equipped with multiple lenses. The obstacle sensor 26 is connected to the control device 18, and the output of the obstacle sensor 26 is transmitted to the control device 18.

Next, the bogie 12 will be described. The bogie body 27 of the bogie 12 has front wheels 28 and rear wheels 29. The front wheels 28 and rear wheels 29 are freely rolling wheels. The front wheels 28 are wheels whose direction can be changed depending on the direction of travel. The bogie body 27 has a loading platform 30 on which a load W can be loaded. A connecting rod 31 is provided at the front of the bogie 12. The leading bogie 12 is connected to the rear of the towing vehicle 11 via the connecting rod 31. The bogies 12 are connected to each other by connecting the connecting rod 31 to the rear of the bogie 12. In this embodiment, the towing vehicle 11 can connect up to six bogies 12 at the maximum, but for the sake of convenience, an example in which three bogies 12 are connected will be described. In this case, the rearmost bogie 12 is connected to the second bogie 12 behind the leading bogie 12 and towed. A bogie group consisting of three bogies 12 is formed. Note that a group of carriages consists of one or more carriages 12.

A first reflector 33 is provided at the front of each of the left and right side surfaces 32 of the bogie body 27. A second reflector 34 is provided at the rear of each of the side surfaces 32. The first reflector 33 of the leading bogie 12 corresponds to a front reflector provided at the frontmost side of the bogie group, and the second reflector 34 of the rearmost bogie 12 corresponds to a rear reflector provided at the rearmost side of the bogie group. When distinguishing between the left and right first reflectors 33 and the left and right second reflectors 34, they are referred to as the right first reflector 33R and right second reflector 34R, and the left first reflector 33L and left second reflector 34L.

The first reflector 33 protrudes laterally from the side surface 32 of the cart body 27 and can be tilted relative to the side surface 32. Specifically, as shown in FIG. 4(a), the first reflector 33 includes a cylindrical reflecting portion 35 that reflects the laser light with high reflectivity and allows the reflected laser light to be received by the laser sensor 25, and a support portion 36 as a tilting mechanism that allows the reflecting portion 35 to be tilted relative to the side surface 32. The reflecting portion 35 is cylindrical in shape and has a reflecting surface 37 that is the same convex curved surface that is the outer circumferential surface of the cylinder. Therefore, the reflecting surface 37 reflects the laser light with a reflectivity equal to or greater than a threshold value.

The support portion 36 is a plate member that supports the reflector 35, and the support portion 36 can tilt forward and backward with respect to the side surface 32, with the pin 38 as a fulcrum. In other words, when an external force in the forward and backward direction is applied to the reflector 35, the support portion 36 tilts forward or backward with respect to the side surface 32. Coil springs 39 and 40 are provided at the front and rear of the support portion 36 as biasing members that bias the support portion 36 so that the support portion 36 faces the side. In addition, when the support portion 36 is tilted by the application of an external force, the reflector 35 returns to its original position before tilting due to the restoring force of the coil springs 39 and 40 when the external force is released. Therefore, the support portion 36 corresponds to a tilting mechanism that allows the first reflector 33 to tilt with respect to the cart 12. The coil springs 39 and 40 correspond to biasing members that allow the first reflector 33 in a tilted state to return to its original position before tilting.

The second reflector 34 has the same configuration as the first reflector 33, protrudes laterally from the side surface 32 of the carriage body 27, and can tilt with respect to the side surface 32. As shown in FIG. 4B, the second reflector 34 includes a cylindrical reflecting portion 41 for reflecting the laser light with high reflectivity and receiving the reflected laser light at the laser sensor 25, and a support portion 42 for tilting the reflecting portion 41 with respect to the side surface 32. The shape of the reflecting portion 41 is the same as that of the reflecting portion 41, and has a reflecting surface 43. The support portion 42 is a horizontal shaft member that supports the reflecting portion 41, and the support portion 42 can tilt back and forth with a pin 44 as a fulcrum with respect to the side surface 32. Coil springs 45 and 46 are provided at the front and rear of the support portion 42 as biasing members that bias the support portion 42 so that the support portion 42 faces the side. The support portion 42 corresponds to a tilting mechanism. The coil springs 45 and 46 correspond to biasing members.

Next, the procedure for detecting an obstacle by the rear obstacle detection device 10 will be described. Figure 5 shows a series of steps S01 to S11 in which the rear obstacle detection device 10 detects an obstacle behind the towing vehicle 11. A program for carrying out the series of steps S01 to S11 shown in Figure 5 is stored in the control device 18.

When the towing vehicle 11 starts moving, the rear obstacle detection device 10 starts scanning the laser sensor 25 (see step S01). For example, as shown in FIG. 6, when the towing vehicle 11 towing three carts 12 curves to the right, the scanning area AR of the laser sensor 25R and the scanning area AL of the laser sensor 25L shown by dotted hatching are different. The scanning area AL of the laser sensor 25L is fan-shaped, but the scanning area AR of the laser sensor 25R is narrower than the scanning area AL of the laser sensor 25L because the laser light of the laser sensor 25 is blocked by the cart 12. The laser sensor 25R detects the cart 12 as an object. The scanning area AR of the laser sensor 25R includes a specific detection area T, which is shown in white in FIG. 6 and will be described later.

Next, it is determined whether or not two or more feature points have been detected on one side by the laser sensor 25 (see step S03). When the laser sensor 25 detects an object that reflects the laser light of the laser sensor 25 with a reflectance equal to or greater than a threshold, the control device 18 determines that the object is a feature point. Therefore, the control device 18 corresponds to a feature point determination unit that determines that an object that reflects the laser light from the laser sensor 25 is a feature point when the reflectance of the reflected laser light received by the laser sensor 25 is equal to or greater than a threshold.

The first reflector 33 and the second reflector 34 of the bogie 12 reflect the laser light of the laser sensor 25 with a reflectance equal to or greater than a threshold value, and therefore can be characteristic points. "One side" refers to either the left or right side of the bogie 12. In FIG. 6, the first reflector 33R and the second reflector 34R of the right side 32 of each bogie 12 that faces the inside of the curve are identified as characteristic points.

When it is determined in step S02 that two or more characteristic points are detected on one side, the control device 18 recognizes that the towing vehicle 11 is towing the curve and sets a specific detection area T (see step S03). The specific detection area T is an area defined by the laser sensor 25 and the multiple detected characteristic points, and is set on the side of the bogie 12 that is on the inside of the curve. Therefore, the control device 18 corresponds to a specific detection area setting unit that sets the specific detection area T defined by the first reflector 33 and the second reflector 34 detected by the laser sensor 25 and the laser sensor 25. Note that the specific detection area T includes the first reflector 33 of the leading bogie 12 and the second reflector 34 of the rearmost bogie 12 as characteristic points, and includes the first reflector 33 and the second reflector 34 of the bogies 12 other than the leading bogie 12 and the rearmost bogie 12 as characteristic points. Therefore, it can be said that the specific detection area T is defined by the front reflector and rear reflector detected by the laser sensor 25 and the laser sensor 25 itself .

The specific detection area T includes the planned route along which the bogie 12 is scheduled to pass. The rearmost bogie 12 will pass on the innermost side of the curve in the specific detection area T. The position and shape of the specific detection area T changes as the towing vehicle 11 and the bogie 12 proceed around the curve. In FIG. 6, the specific detection area T is the white area in the scanning area AR of the laser sensor 25R.

Next, the control device 18 determines whether or not an object has been detected in the specific detection zone T (see step S04). When the laser sensor 25 detects an object in the specific detection zone T, the control device 18 determines that the object detected in the specific detection zone T is an obstacle (see step S05). Thus, when the laser sensor 25 detects an object in the specific detection zone T, the control device 18 corresponds to an obstacle determination unit that determines that the object is an obstacle.

Next, the control device 18 stops the towing vehicle 11 because there is a risk that an obstacle in the specific detection zone T may interfere with the trolley 12 (see step S06). Therefore, the trolley 12 will not interfere with an obstacle in the specific detection zone T.

In step S02, there are cases where it is not determined that two or more characteristic points are detected on one side. In this case, the control device 18 determines whether one characteristic point is detected on both sides of the bogie 12 (see step S07). If it is determined that one characteristic point is detected on both sides of the bogie 12, the control device 18 determines that the towing vehicle 11 is traveling straight ahead (see step S10). In this case, the process returns to step S02.

If it is determined in step S07 that one characteristic point is not detected on either side of the bogie 12, the control device 18 determines whether the laser sensor 25 detects the characteristic point and the bogie 12 (see step S08). If it is determined that the characteristic point and the bogie 12 are not detected, the control device 18 determines that the towing vehicle 11 is traveling alone without towing the bogie 12 (see step S09). Then, the control device 18 ends the process.

When it is not determined in step S08 that the characteristic points and the bogie 12 are not detected, the control device 18 determines that a detection abnormality has occurred (see step S11). Specifically, for example, this is the case when the laser sensor 25 detects the characteristic points but does not detect the bogie 12. When the control device 18 determines that a detection abnormality has occurred, it stops the towing vehicle 11.

Next, we will explain a specific example of a rear obstacle detection method in which the rear obstacle detection device 10 detects obstacles behind the towing vehicle 11. First, we will explain the rear obstacle detection method when the towing vehicle 11 is towing three carts 12.

The towing vehicle 11 is automatically driven toward the destination while estimating its own position. As shown in FIG. 6, when the towing vehicle 11 curves to the right, the laser sensor 25R detects the first reflector 33R and the second reflector 34R on the right side surface 32 of each bogie 12 as characteristic points, and also detects the bogie 12 as an object. There is no detection target in the scanning area AL of the laser sensor 25L.

The control device 18 sets a specific detection area T using the first reflector 33R and the second reflector 34R detected as characteristic points and the laser sensor 25R, and determines whether an object is detected by the laser sensor 25R in the specific detection area T. As shown in FIG. 6, when a moving object M enters the specific detection area T, the laser sensor 25R detects the moving object M, and the control device 18 determines that the moving object M is an obstacle and controls the motor drive unit 22 so that the towing vehicle 11 stops. The moving object M is, for example, a mobile work vehicle or may be a worker. The control device 18 does not determine that an object detected by the laser sensor 25 in an area other than the specific detection area T in the laser light scanning area AR is an obstacle.

However, when the moving body M enters the specific detection area T, the moving body M is positioned between the second reflector 34R on the right of the rearmost trolley 12 and the laser sensor 25R, and the laser sensor 25R is therefore unable to detect the second reflector 34R on the right of the rearmost trolley 12. In this embodiment, even if the laser sensor 25R is no longer able to detect the second reflector 34R on the right of the rearmost trolley 12, the control device 18 does not immediately reduce the specific detection area T, but maintains the specific detection area T for a certain period of time (e.g., one second). This prevents the moving body M from not being identified as an obstacle.

When there is no obstacle entering the specific detection area T and the towing vehicle 11 continues to curve to the right, the specific detection area T changes shape in response to the curve travel of the bogie 12. As the rearmost bogie 12 approaches the end of its curve travel, the number of characteristic points detected by the laser sensor 25R decreases, and the specific detection area T shrinks. When the rearmost bogie 12 travels straight, the left and right laser sensors 25R, 25L detect only the first reflectors 33R, 33L of the leading bogie 12, so no specific detection area T is set on the left or right sides of the bogie 12. In other words, only one characteristic point is detected on each of the left and right sides of the bogie 12, and the control device 18 recognizes the straight travel.

Next, detection of an obstacle when the towing vehicle 11 is towing one bogie 12 will be described. When one bogie 12 is towed, the bogie 12 is both the leading bogie and the trailing bogie. When the towing vehicle 11 curves to the right, a specific detection area T is set by detecting characteristic points using the laser sensor 25R. The specific detection area T is set by three points: the first reflector 33R and the second reflector 34R on the right side 32 of the bogie 12, and the laser sensor 25R. When an object is detected in the specific detection area T, the control device 18 determines that the object in the specific detection area T is an obstacle.

When the towing vehicle 11 is traveling alone without towing the bogie 12, the bogie 12 and characteristic points are not detected by the laser sensors 25R and 25L even when traveling around a curve, so the specific detection area T is not set. If the bogie 12 is detected even though the characteristic points are not detected, the control device 18 determines that there is a detection abnormality. Examples of detection abnormalities include an abnormality in the first reflector 33 and the second reflector 34, or a failure of the laser sensor 25.

This embodiment provides the following advantages.
(1) When the towing vehicle 11 travels around a curve so that the first reflector 33 and the second reflector 34 are on the inside of the curve, the laser sensor 25 detects the first reflector 33 and the second reflector 34 as characteristic points. The control device 18 sets a specific detection area T that is partitioned by the first reflector 33 and the second reflector 34 as characteristic points and the laser sensor 25. The specific detection area T is an area that includes the planned course along which the cart 12 will pass on the side of the cart 12, and when an object is detected in the specific detection area T by the laser sensor 25, the control device 18 determines that the object is an obstacle. Therefore, by determining that an object in the specific detection area T is an obstacle, it is possible to reliably detect an obstacle that may interfere with the cart 12 when traveling around a curve. In other words, it is possible to determine whether or not the moving body M has entered as an obstacle into the specific detection area T behind the towing vehicle 11 that has passed.

(2) The towing vehicle 11 is equipped with a drive motor 16 and a motor drive unit 22 that controls the drive motor 16, and the control device 18 controls the motor drive unit 22 to stop the towing vehicle 11 when it determines that an object is an obstacle. This makes it possible to prevent interference between the bogie 12 and an obstacle when the towing vehicle 11 and the bogie 12 are traveling around a curve.

(3) The towing vehicle 11 is equipped with a control device 18 that determines that an object reflecting laser light from the laser sensor 25 is a feature point when the reflectance of the reflected laser light received by the laser sensor 25 is equal to or greater than a threshold value. The first reflector 33 (second reflector 34) has a reflecting portion 35 (41) that reflects the laser light from the laser sensor 25 so that the reflectance of the reflected laser light received by the laser sensor 25 is equal to or greater than the threshold value. Therefore, the reflecting portion 35 of the first reflector 33 and the reflecting portion 41 of the second reflector 34 reflect the laser light from the laser sensor 25 so that the reflectance of the reflected laser light received by the laser sensor 25 is equal to or greater than the threshold value. Therefore, the control device 18 can reliably determine that the first reflector 33 and the second reflector 34 are feature points by the laser sensor 25 receiving the reflected laser light from the first reflector 33 and the second reflector 34.

(4) When only one feature point is identified, the control device 18 does not set a specific detection area T, assuming that the towing vehicle 11 and the carriage 12 are traveling straight ahead. Therefore, when the towing vehicle 11 and the carriage 12 are traveling straight ahead, no processing is performed to detect obstacles behind the towing vehicle 11, thereby reducing the load on the control device 18.

(5) After the control device 18 has determined that an object in the specific detection zone T is an obstacle, when the object detected in the specific detection zone T blocks the laser light and therefore the second reflector 34 is not detected as a feature point, the control device 18 maintains the specific detection zone T for a certain period of time. Therefore, even if the object detected in the specific detection zone T blocks the laser light and therefore the laser sensor 25 is no longer able to detect the second reflector 34, the specific detection zone T is not immediately reduced or eliminated, and the object in the specific detection zone T can be detected as an obstacle for a certain period of time.

(6) The device includes a tilting mechanism that allows the first reflector 33 and the second reflector 34 to be tilted relative to the cart 12, and coil springs 39, 40 as biasing members that allow the first reflector 33 and the second reflector 34 in the tilted state to return to their original positions before tilting. Therefore, by allowing the first reflector 33 and the second reflector 34 to be tilted relative to the cart 12, even if the first reflector 33 and the second reflector 34 interfere with an object, the first reflector 33 and the second reflector 34 themselves are unlikely to become an obstacle to the interfering object. In addition, the coil springs 39, 40 allow the first reflector 33 and the second reflector 34 in the tilted state to return to their original positions before tilting, so that the function of the first reflector 33 and the second reflector 34 can be maintained.

(7) The reflecting portion 35 (41) has a convex curved reflecting surface 37 (43), so that the laser light of the laser sensor 25 can be reliably reflected toward the laser sensor 25 regardless of the curvature of the curve on which the towing vehicle 11 and the dolly 12 are traveling.

(8) Since there is no need to provide the bogie 12 with sensors for detecting obstacles or connectors for connecting wiring, there is no need to connect or disconnect wiring when connecting or disconnecting the towing vehicle 11 and the bogie 12, or when connecting or disconnecting bogies 12 from each other. Therefore, there is no decrease in the ease of connecting or disconnecting the towing vehicle 11 and the bogie 12, or when connecting or disconnecting bogies 12 from each other.

Second Embodiment
Next, a second embodiment will be described. This embodiment differs from the first embodiment in that the towing vehicle tows two or more dollies, and that the dollies are provided with a reflector only on the rear part of the side. In this embodiment, the same configuration as in the first embodiment will be described with reference to the first embodiment, and common reference numerals will be used.

As shown in FIG. 7, the rear obstacle detection device 50 of this embodiment has a towing vehicle 11 and three bogies 12. Reflectors 51 (51R, 51L) are provided at the rear of the left and right side surfaces 32 of the bogie 12. The reflectors 51 have the same configuration as the first reflector 33 and the second reflector 34. In this embodiment, the towing vehicle 11 tows three bogies 12, and a bogie group consisting of the three bogies 12 is formed. The reflector 51 of the leading bogie 12 corresponds to a front reflector provided at the forefront of the side of the bogie group, and the reflector 51 of the rearmost bogie corresponds to a rear reflector provided at the rear end of the side of the bogie group. As shown in FIG. 7, the specific detection area T set when turning to the right is set by the reflector 51R of each bogie 12 detected as a characteristic point and the laser sensor 25. In other words, the specific detection area T is defined by the front reflector and rear reflector detected by the laser sensor 25 and the laser sensor 25 itself.

According to this embodiment, if the towing vehicle 11 is towing two or more bogies 12 in a group, the specific detection area T can be set even if only one reflector 51 is provided on the side surface 32 of the bogie 12. Therefore, it is possible to reliably detect obstacles that may interfere with the bogie 12 when traveling around a curve while suppressing the manufacturing cost of the rear obstacle detection device 50. Note that when two bogies 12 are towed, the specific detection area T can be set by the reflector 51 of the leading bogie 12, which corresponds to the forward reflector, the reflector of the rearmost bogie 12, which corresponds to the rear reflector, and the laser sensor 25.

The present invention is not limited to the above embodiment, and various modifications are possible within the scope of the invention. For example, the following modifications may be made:

In the above embodiment, the front reflector and the rear reflector are provided with a tilting mechanism and a biasing member, but this is not limited thereto. The front reflector and the rear reflector do not necessarily have to have a tilting mechanism and a biasing member. In addition, the tilting mechanism may be configured to tilt the front reflector and the rear reflector relative to the dolly.
○ In the above embodiments, the case where three bogies are towed has been described as an example, but the number of bogies is not limited to three. In the first embodiment, the number of bogies in the bogie group may be one or more, for example, the towing vehicle may tow one bogie. When there is one towed bogie, the leading bogie is the rearmost bogie. Therefore, when one bogie in the first embodiment constitutes the bogie group, the first reflector provided in front of the side surface of the bogie corresponds to the front reflector provided at the forefront of the side surface of the bogie group, and the second reflector provided at the rear of the side surface of the bogie corresponds to the rear reflector provided at the rearmost of the side surface of the bogie group. In the second embodiment, the number of bogies may be two or more. When two bogies in the second embodiment constitute the bogie group, the reflector of the leading bogie corresponds to the front reflector provided at the forefront of the side surface of the bogie group, and the reflector of the rearmost bogie corresponds to the rearmost of the side surface of the bogie group.
In the above embodiment, a case has been described in which a moving object enters the specific detection area while the towing vehicle is traveling around a curve, and the moving object that has entered the specific detection area is determined to be an obstacle, but this is not limited to the above. For example, depending on the route of the towing vehicle, a pillar, shelf, etc. may be present in the specific detection area, and in this case, the pillar, shelf, etc. is determined to be an obstacle.

10, 50 Rear obstacle detection device for towing vehicle 11 Towing vehicle 12 Carriage 16 Drive motor (travel drive unit)
18 Control device (driving control unit, specific detection area setting unit, feature point discrimination unit)
22 Motor drive unit 25 Laser sensor 27 Cart body 28 Front wheels 29 Rear wheels 30 Cargo platform 31 Connecting rod 32 Side surface 33 (33R, 33L) First reflector 34 (34R, 34L) Second reflector 35, 41 Reflecting portion 37, 43 Reflecting surface 38, 44 Pin 39, 40, 45, 46 Coil spring (biasing member)
51 (51R, 51L) Reflector AR Laser light scanning area (right)
AL Laser light scanning area (left)
M Moving object (obstacle)
T Specific detection area θ Scanning angle

Claims (8)

A tow vehicle and
A group of carriages towed by the towing vehicle,
A rear obstacle detection device for a towing vehicle that detects an obstacle behind the towing vehicle,
a laser sensor provided at a rear portion of a side surface of the towing vehicle, the laser sensor including the side of the group of carriages in a scanning area of the laser light;
a front reflector that is provided at the frontmost side of the vehicle group and that can be detected as a characteristic point by the laser sensor;
a rear reflector provided at the rear end of a side surface of the group of carriages and detectable as a characteristic point by the laser sensor;
a specific detection area setting unit that sets a specific detection area defined by the front reflector and the rear reflector detected by the laser sensor and the laser sensor;
and an obstacle discrimination unit that, when the laser sensor detects an object in the specific detection area, discriminates the object as an obstacle. The towing vehicle is
A travel drive unit;
A travel control unit that controls the travel drive unit,
2. The rear obstacle detection device for a towing vehicle according to claim 1, wherein the travel control unit controls the travel drive unit so as to stop the towing vehicle when the obstacle discrimination unit discriminates the object as an obstacle. the towing vehicle includes a feature point discrimination unit that discriminates an object that reflects the laser light from the laser sensor as a feature point when a reflectance of the reflected laser light received by the laser sensor is equal to or greater than a threshold value;
3. The rear obstacle detection device for a towing vehicle according to claim 1, wherein the front reflector and the rear reflector have a reflective portion that reflects the laser light from the laser sensor so that the reflectance of the reflected laser light received by the laser sensor is equal to or greater than a threshold value. The rear obstacle detection device for a towing vehicle according to claim 3, characterized in that when the feature point discrimination unit determines that there is only one feature point, the specific detection area setting unit does not set the specific detection area. The rear obstacle detection device for a towing vehicle according to any one of claims 1 to 4, characterized in that, after the obstacle discrimination unit discriminates the object as an obstacle, when the rear reflector is not detected as a feature point by the laser sensor, the specific detection area setting unit maintains the specific detection area for a certain period of time. a tilting mechanism that enables the front reflector and the rear reflector to be tilted relative to the group of carriages;
6. The rear obstacle detection device for a towing vehicle according to claim 1, further comprising a biasing member that enables the front reflector and the rear reflector in a tilted state to return to their original positions before tilting. The rear obstacle detection device for a towing vehicle according to claim 3, characterized in that the reflecting portion has a convex curved reflecting surface. A method for detecting an obstacle behind a towing vehicle that tows a group of carriages, comprising:
a laser sensor provided at a rear portion of a side surface of the towing vehicle, the laser sensor including the side of the group of carriages in a scanning area of the laser light;
a front reflector that is provided at the frontmost side of the vehicle group and that can be detected as a characteristic point by the laser sensor;
a rear reflector provided at the rear end of a side surface of the group of carriages and detectable as a characteristic point by the laser sensor;
When the laser sensor detects the front reflector and the rear reflector, a specific detection area is set which is partitioned by at least the front reflector, the rear reflector, and the laser sensor;
A method for detecting an obstacle behind a towing vehicle, comprising: discriminating an object as an obstacle when an object is detected in the specific detection area.

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