JP7294162B2 - driverless forklift - Google Patents

Description

The present invention relates to an unmanned forklift.

As a guidance system for unmanned forklifts, the system moves while detecting magnetic bars embedded in the floor with guide sensors. (For example, Patent Document 1).

JP-A-8-166821

By the way, as a configuration example of an unmanned forklift of a guideless guidance system, as shown in FIG. 104. Furthermore, the environment sensor (distance sensor) 105 installed on the upper part of the vehicle body 103 measures the distance α to the wall 106 of the building and the obstacles such as facilities, thereby estimating the self position while traveling.

In this case, in contrast to the state shown in FIG. join. As a result, the height of the vehicle body 103 is increased around the front wheels 101, and the vehicle body 103 is tilted forward, resulting in deviation from the actual position. That is, when the height S of the vehicle body 103 changes, the distance α to the wall 106 shifts by an amount Y, and the position shifts when estimating the self-position.

SUMMARY OF THE INVENTION An object of the present invention is to provide an unmanned forklift capable of accurately measuring the distance to an object existing in the surroundings.

An unmanned forklift for solving the above problems comprises a vehicle body equipped with a fork that moves up and down at the front, a distance sensor installed on the vehicle body for detecting a distance to an object existing around the vehicle body, and the distance sensor. and a control unit that controls traveling while estimating the self-position based on the distance to the object, wherein the vehicle height change amount detects the amount of change in the height of the vehicle body in the front-rear direction. The gist of the present invention is that it comprises detection means, and correction means for correcting the distance to an object detected by the distance sensor based on the amount of change in the height of the vehicle body detected by the vehicle height change amount detection means.

According to this, the correction means corrects the distance to the object detected by the distance sensor based on the amount of change in the height of the vehicle body detected by the vehicle height change amount detection means for detecting the amount of change in the height of the vehicle body in the longitudinal direction. Thus, it is possible to accurately measure the distance to an object existing in the surroundings.

Further, in the unmanned forklift truck, the vehicle body height change amount detecting means is supported such that a rear wheel support member for supporting the rear wheel with respect to the vehicle body can swing up and down in a state in which the rear wheel is urged toward the ground. and an extendable cylinder is interposed between the vehicle body and the rear wheel support member, and the vehicle body height variation detection means includes an extension sensor for measuring the extension and retraction amount of the cylinder, It is preferable to detect the amount of change in height of the vehicle body in the longitudinal direction based on the change in the amount of expansion and contraction of the cylinder detected by the amount of expansion and contraction sensor.

Further, in the unmanned forklift, the vehicle body height variation detection means includes a floor distance sensor that is provided on the bottom surface of the vehicle body and measures the distance from the floor. It is preferable to detect the amount of change in height of the vehicle body in the longitudinal direction based on the change in distance.

Also, in the unmanned forklift, the distance sensor may be a laser range finder.

ADVANTAGE OF THE INVENTION According to this invention, the distance to the object which exists in the circumference|surroundings can be measured accurately.

The side view of the unmanned forklift in embodiment. A perspective view of an unmanned forklift. The figure which looked at the drive unit of an unmanned forklift from the back. The side view of the drive unit of the unmanned forklift. A block diagram showing an electrical configuration of an unmanned forklift. The side view of the drive unit of the unmanned forklift. (a) is a side view of the drive unit without a load, and (b) is a side view of the drive unit with a load. (a) is a side view of the unmanned forklift without a load, and (b) is a side view of the unmanned forklift with a load. (a) is a side view of the unmanned forklift without a load, and (b) is a side view of the unmanned forklift with a load. (a) is a perspective view of an unmanned forklift for explaining another example, and (b) is a rear view of the unmanned forklift of another example. (a) and (b) are side views of an unmanned forklift for explaining problems.

An embodiment embodying the present invention will be described below with reference to the drawings.
In this embodiment, an unmanned forklift is applied to a reach-type forklift, which travels based on map information and its own position. The self-position is estimated by detecting surrounding objects using sensors and comparing them with map information.

As shown in FIGS. 1 and 2, a pair of left and right reach legs 12 are provided at the front of a vehicle body 11 of an unmanned forklift 10 . A front wheel 13 is supported at the tip of each reach leg 12 .

The unmanned forklift 10 has a cargo handling device 14 on the front part of the vehicle body 11 . The cargo handling device 14 includes a pair of left and right masts 15 that move back and forth along each reach leg 12 by driving the reach cylinder. A pair of left and right forks 16 are provided in front of the mast 15 via lift brackets 17 . The fork 16 can move up and down along the mast 15 . A pair of left and right forks 16 that can move up and down are moved up and down by lift cylinders.

As shown in FIG. 3, drive steering wheels 18 are provided on the left side of the rear portion of the vehicle body 11 . A caster wheel 19 is provided on the right side of the rear portion of the vehicle body 11 .
As shown in FIGS. 1 and 2, a standing-type driver's seat 20 is provided on the rear right side of the vehicle body 11, and the unmanned forklift 10 is configured to be operated by the driver. An unmanned forklift without a driver's seat may be used. A driver's seat 20 is surrounded by a plurality of pillars 21 erected on the vehicle body 11 and a head guard 22 fixed to the upper ends of the pillars 21 . The head guard 22 is arranged horizontally. A steering wheel 23 as an operation member, various operation levers 24 and the like are arranged in the driver's seat 20 .

As shown in FIGS. 3 and 4 , the vehicle body 11 and the drive steering wheel 18 and caster wheel 19 are connected by a suspension device 30 . The suspension device 30 has a drive unit 31 .

The drive unit 31 arranged at the rear portion of the vehicle body 11 includes a travel motor 32, a support arm 33 that supports the travel motor 32, a rotary shaft 34 connected to the support arm 33, and provided below the support arm 33, and a gear housing 35 that supports the drive steering wheels 18 . Further, the drive unit 31 is provided with a suspension spring 36 and a swing cylinder 37 .

As shown in FIG. 4, the support arm 33 is formed in a substantially crank shape, and a rotating shaft 34 is fixed to the base of the support arm 33, which is the front portion. As shown in FIG. 3 , the rotating shaft 34 is supported by bearings 38 and 39 provided on the vehicle body 11 so as to extend in the vehicle width direction, and is rotatable relative to the vehicle body 11 . Therefore, the drive unit 31 can be vertically displaced with respect to the vehicle body 11 .

The travel motor 32 is attached to the top of the support arm 33 . The rotational force of the travel motor 32 is transmitted to the driving steered wheels 18 via a rotation transmission mechanism accommodated in the gear housing 35 . The traveling motor 32 drives the steered wheels 18 , and the unmanned forklift 10 travels on the floor surface F by driving the steered wheels 18 .

A gear housing 35 provided below the support arm 33 is rotatable with respect to the support arm 33 . A gear wheel 40 is provided on the top of the gear housing 35 . A steering motor 41 (see FIG. 5) is connected to the gear wheel 40, and the direction of the drive steering wheel 18 is changed by the steering motor 41 to be steered. Further, as shown in FIG. 3, the caster wheel 19 is also connected to and supported by the rotating shaft 34 .

As shown in FIG. 4, the suspension spring 36 biases the vehicle body 11 via the support arm 33 so as to displace the drive steering wheel 18 downward. The vicinity of the upper end of the suspension spring 36 is connected to a bracket 42 in front of the drive unit 31 provided on the vehicle body 11 , and the lower end is connected to a bracket 43 provided on the upper surface of the support arm 33 . The suspension spring 36 is supported in an oblique posture in which the axis of expansion and contraction is parallel to the tangential direction of the swing locus of the support arm 33 .

A swing cylinder 37 regulates the vertical displacement of the support arm 33 . As shown in FIG. 4 , one end of the swing cylinder 37 is connected to a bracket portion 44 provided on the support arm 33 via a connecting pin 45 , and the other end of the swing cylinder 37 is connected to the vehicle body 11 . It is connected via a connecting pin 47 to a bracket 46 provided at the rear. The swing cylinder 37 is supported in an oblique posture in which the axis of expansion and contraction is parallel to the tangential direction of the swing locus of the support arm 33 .

The swing cylinder 37 has a cylinder body 48 and a piston rod 49 . The swing cylinder 37 includes a lock electromagnetic valve 50 that allows or restricts the movement of the piston rod 49 with respect to the cylinder body 48 . The lock solenoid valve 50 regulates the retracting movement of the piston rod 49 with respect to the cylinder body 48 when the driving current is not supplied from the outside, and permits the retracting movement when the driving current is supplied. Even if an external force that causes the vehicle body 11 to tilt toward the steering wheels 18 is applied due to lateral acceleration during traveling or a moment load due to the load of cargo, the locking solenoid valve 50 is controlled and the swing cylinder 37 causes the steering wheels 18 to tilt. is restricted, the tilting of the vehicle body 11 toward the drive steering wheels 18 is restricted. As a result, the running stability of the vehicle can be ensured.

In this way, the drive unit 31 as a rear wheel support member for supporting the steering wheel 18, which is the rear wheel, of the vehicle body 11 swings up and down in a state in which the suspension spring 36 biases the steering wheel 18 toward the ground. supported as possible. An extendable swing cylinder 37 is interposed between the vehicle body 11 and the drive unit 31 .

When the height of the vehicle body 11 is displaced up and down, the swing cylinder 37 expands and contracts to raise and lower the drive steering wheel 18, which is the rear wheel, so that it is always grounded. For example, when the rear of the vehicle body 11 is raised, the swing cylinder 37 is contracted in order to ground the driving steering wheel 18 and the caster wheel 19 which are the rear wheels.

Further, the vertical swing of the suspension device 30 is locked by fixing the length of the swing cylinder 37 by the lock electromagnetic valve 50 as required during turning.
As shown in FIG. 4 , the swing cylinder 37 is equipped with an expansion/contraction amount sensor 60 that measures the expansion/contraction amount of the swing cylinder 37 . For example, a light projecting/receiving sensor can be used as the expansion/contraction amount sensor 60 . Specifically, the light projector 61 is fixed to the cylinder body 48 and the light receiver 62 is fixed to the piston rod 49 so as to face the light projector 61 .

As described above, the expansion/contraction amount sensor 60 for measuring the expansion/contraction amount of the swing cylinder 37 is installed. can be detected.

As shown in FIGS. 1 and 2, a laser range finder (LRF) 63 is installed above the head guard 22 . The laser range finder 63 as a distance sensor is for acquiring information about objects existing around the vehicle body 11, and by irradiating the laser at 360° while changing the irradiation angle, the laser range finder 63 changes the irradiation direction of the laser. It is possible to measure the distance to a positioned object. For example, as shown in FIG. 8A, a laser range finder 63 can detect a distance α to a building wall 90 as an object existing in the surroundings. In addition, a laser range finder (LRF) 63 can be used to detect the distance to an obstacle such as equipment as an object existing in the surroundings.

Here, in FIG. 6, "a" is the distance between the connecting pin 45 and the connecting pin 47 in the swing cylinder 37. As shown in FIG. “b” is the distance between the rotary shaft 34 and the connecting pin 47 of the swing cylinder 37 . “c” is the distance between the connecting pin 45 and the rotating shaft 34 in the swing cylinder 37 . "d" is the distance between the pivot axis 34 and the center of the drive steerable wheels 18; “β” is an angle between a line connecting the connecting pin 45 of the swing cylinder 37 and the pivot shaft 34 and a line connecting the pivot shaft 34 and the center of the drive steering wheel 18 . “L” is the distance (wheel height ).

In FIG. 6, the b value, c value, and d value are constant, the β value is constant, and the distances b, c, d and the angle β are constant, so if the distance (cylinder length) a changes, , the distance (wheel height) L also changes. The difference between the distance (wheel height) L before and after the distance (cylinder length) a changes becomes the change amount X of the height S of the vehicle body 11 in FIGS. 9(a) and 9(b).

As shown in FIG. 5, a laser range finder (LRF) 63 is connected to the controller 64 . The controller 64 can detect the distance to the wall 90 as an object existing around the vehicle body 11 from the signal from the laser range finder (LRF) 63 . Specifically, the laser range finder 63 associates both the irradiation angle of the laser and the distance to the object positioned at the irradiation angle and outputs them to the controller 64 so that the controller 64 can detect the wall existing in the detection range. and obstacles can be recognized. This allows the vehicle to travel while estimating its own position.

The expansion/contraction amount sensor 60 is connected to the controller 64 . The controller 64 detects the amount of extension/contraction of the swing cylinder 37 from the signal from the extension/contraction amount sensor 60, and detects the amount of change X in the height S of the vehicle body 11 in the longitudinal direction based on the change in the amount of extension/contraction of the swing cylinder 37. You can do it.

The traveling motor 32 is connected to the controller 64 . The controller 64 is adapted to control the traction motor 32 to drive the drive steered wheels 18 .
A steering motor 41 is connected to the controller 64 . The controller 64 can perform steering by controlling the steering motor 41 to change the direction of the drive steering wheels 18 .

In this embodiment, the controller 64 constitutes a control unit that controls traveling while estimating the self-position based on the distance to an object detected by a laser range finder (LRF) 63 as a distance sensor. The expansion/contraction amount sensor 60 and the controller 64 constitute vehicle height change amount detection means for detecting the amount of change in the height of the vehicle body 11 in the longitudinal direction. Further, the controller 64 constitutes correction means for correcting the distance to the object by the laser range finder 63 based on the amount of change in the height of the vehicle body 11 detected by the vehicle height change amount detection means.

Next, the action will be described.
9(a) shows the unmanned forklift 10 with no load W loaded, and FIG. 9(b) shows the unmanned forklift 10 with the load W loaded. , the height of the laser range finder 63 from the floor F. “Q” is the distance between the contact point of the front wheel 13 and the laser range finder 63 . "R" is the distance between the front wheels 13 and the drive steerable wheels 18; "S" is the height of the vehicle body 11 from the floor surface F when the load W is not mounted on the forks 16 shown in FIG. 9(a).

FIG. 8(a) shows the unmanned forklift 10 with no load W loaded, and FIG. 8(b) shows the unmanned forklift 10 with the load W loaded. , the distance from the laser range finder 63 to the wall 90 as shown in FIG. "Y" is the deviation amount with respect to the distance α from the laser range finder 63 to the wall 90, as shown in FIG. 8(b).

The angle θ between the line connecting the grounding point of the front wheel 13 and the laser range finder 63 and the floor surface F when the load W is not loaded in FIG. From the height P and the distance Q between the grounding point of the front wheel 13 and the laser range finder 63, it can be expressed as in Equation (1).

θ=sin ^-1 (P/Q)
... (1)
On the other hand, the deviation amount Φ of the aforementioned angle θ when the load W of FIG. Using R, it can be expressed as in formula (2).

Φ=tan ⁻¹ {(S+X)/R}−tan ⁻¹ (S/R)
... (2)
The amount of deviation Y when the load W is loaded is the distance Q between the grounding point of the front wheel 13 and the laser range finder 63, the angle θ between the line connecting the grounding point of the front wheel 13 and the laser range finder 63 and the floor surface F, From the deviation amount Φ of the angle θ, the equation (3) is obtained.

Y = Q x cos θ - Q x cos (θ + Φ)
... (3)
The controller 64 controls the longitudinal direction of the laser range finder 63 when the load W is loaded on the fork 16 shown in FIG. In order to calculate the deviation amount Y of the position of the load W on the fork 16 shown in FIG. A change amount X of the height S of the vehicle body 11 when mounted is calculated. The controller 64 calculates the amount of deviation Y of the laser range finder 63 from the amount of change X of the height S of the vehicle body 11, thereby accurately estimating the self-position in consideration of the amount of deviation Y.

A detailed description will be given below.
When the vehicle body 11 is displaced vertically as shown in FIGS. 8(a) and 8(b), the urging force of the suspension spring 36 causes driving steering as shown in FIGS. 7(a) and 7(b). The ring 18 is always grounded. At this time, the swing cylinder 37 expands and contracts.

Specifically, when the load W is not loaded, the swing cylinder 37 is extended and the drive steering wheel 18 is grounded as shown in FIG. 7(a). When the rear of the vehicle body 11 is lifted by loading the load W as shown in FIG. 7(b), the swing cylinder 37 is contracted in order to ground the drive steering wheel 18 to the ground.

As shown in FIG. 4, the expansion/contraction amount of the swing cylinder 37 is measured by the expansion/contraction amount sensor 60 . Based on the measurement result of the expansion/contraction amount of the swing cylinder 37 by the expansion/contraction amount sensor 60, the change amount X of the height S of the vehicle body 11 is calculated as follows.

As shown in equation (4), the distance L to the center of the drive steering wheel 18 in the direction perpendicular to the line connecting the pivot shaft 34 and the connecting pin 47 of the swing cylinder 37 in FIG. distance a between the connecting pin 45 and the connecting pin 47 in the distance a, distance b between the rotating shaft 34 and the connecting pin 47 of the swing cylinder 37, distance c between the rotating shaft 34 and the connecting pin 45 of the swing cylinder 37, and rotating shaft The distance d between 34 and the center of the drive steering wheel 18, the angle β between the line connecting the connecting pin 45 of the swing cylinder 37 and the pivot shaft 34, and the line connecting the pivot shaft 34 and the center of the drive steering wheel 18 is represented by

L=d×sin[β−cos ⁻¹ {(b ² +c ² +a ² )/2bc}]
... (4)
Here, since the distances b, c, d and the angle β are constant, when the distance (cylinder length) a changes, the distance (wheel height) L also changes. The height change amount X is the difference between the distance (wheel height) L before and after the distance (cylinder length) a is changed.

Based on the relationship shown in the formula (4), the controller 64 can find the distance (cylinder length) _a1 when the load W is not mounted on the fork 16, so the distance _L1 is calculated from the formula (5). do.

L ₁ =d×sin[β−cos ⁻¹ {(b ² +c ² +a ₁ ² )/2bc}]
... (5)
Further, based on the relationship shown in formula (4), the controller 64 knows the distance (cylinder length) _a2 when the load W is mounted on the fork 16, so the distance _L2 is calculated by formula (6). Calculate from

L ₂ =d×sin[β−cos ⁻¹ {(b ² +c ² +a ₂ ² )/2bc}]
... (6)
Then, the controller 64 obtains the difference from the distance _L1 when the load W is not loaded on the forks 16 and the distance _L2 when the load W is loaded on the forks 16 by the formula (7). Thus, the change amount X of the height S of the vehicle body 11 is calculated.

X=L ₂ -L ₁
... (7)
9A from the height S of the vehicle body 11, the amount of change X in the height S of the vehicle body 11, and the distance R between the front wheels 13 and the drive steered wheels 18, according to the above equation (2). 9B with respect to the angle θ formed by the line connecting the grounding point of the front wheel 13 and the laser range finder 63 and the floor surface F when the load W is not loaded.

Furthermore, the controller 64 uses the above-described formula (3) to determine the displacement amount Y in the longitudinal direction of the laser range finder 63 when the load W is mounted on the forks 16 shown in FIG. It is calculated from the angle θ between the line connecting the grounding point of the front wheel 13 and the laser range finder 63 and the floor F, the amount of deviation Φ, and the distance Q between the grounding point of the front wheel 13 and the laser range finder 63 .

Then, the controller 64 subtracts the deviation amount Y from the distance measurement result obtained by the laser range finder 63 to obtain the corrected distance to the wall 90, that is, the corrected true distance.
In this way, the unmanned forklift 10 equipped with a laser range finder (LRF) 63 and traveling while estimating its own position by measuring the distance to obstacles such as building walls 90 and equipment, The weight of the load W is added to the vehicle body 11 when the load W is loaded on the forks 16 as opposed to the state where the load W is not loaded on the forks 16, so the height S of the vehicle body 11 with the front wheels 13 as the axis increases. , tilting forward causes a deviation from the actual position.

On the other hand, in the present embodiment, by detecting the amount of change in the amount of expansion and contraction of the swing cylinder 37, the amount of change X in the height S of the vehicle body 11 is calculated, and the amount of change Y is calculated from the amount of change X. . By doing so, the amount of deviation of the self-position to be corrected can be known.

According to the above embodiment, the following effects can be obtained.
(1) The configuration of the unmanned forklift 10 includes a vehicle body 11 having a fork 16 that moves up and down at the front, and a distance sensor installed on the vehicle body 11 that detects the distance to a wall 90 as an object existing around the vehicle body 11. A laser range finder (LRF) 63 as a controller, and a controller 64 as a control unit that controls traveling while estimating the self-position based on the distance to a wall 90 as an object by the laser range finder (LRF) 63. . A stretching amount sensor 60 and a controller 64 as vehicle body height variation detecting means for detecting a variation X in the height S of the vehicle body 11 in the longitudinal direction, and changes in the height S of the vehicle body 11 by the stretching amount sensor 60 and the controller 64. A controller 64 is provided as correction means for correcting the distance to the wall 90 as an object by the laser range finder (LRF) 63 based on the quantity X. Therefore, it is possible to accurately measure the distance to the surrounding object.

(2) A drive unit 31 as a rear wheel support member for supporting the steering wheels 18, which are the rear wheels, with respect to the vehicle body 11 is supported so as to be able to swing vertically while urging the steering wheels 18 toward the ground. In addition, a swing cylinder 37 is interposed between the vehicle body 11 and the drive unit 31, and the vehicle body height variation detection means includes an extension sensor 60 for measuring the extension and retraction amount of the swing cylinder 37. The change amount X of the height S of the vehicle body 11 in the front-rear direction is detected based on the change in the expansion/contraction amount of the swing cylinder 37 detected by the sensor 60 . Therefore, it is possible to accurately measure the distance to the surrounding object.

(3) Since the distance sensor is a laser range finder (LRF) 63, it is practical.
Embodiments are not limited to the above, and may be embodied as follows, for example.

○As shown in FIGS. 10(a) and 10(b), a floor surface distance sensor 71 is attached to a plate 70 provided on the bottom portion of the rear portion of the vehicle body 11, and the distance to the floor surface F is directly measured to measure the height. A change amount X is detected. Specifically, a light projection sensor can be used as the floor distance sensor 71 .

Thus, the vehicle body height change amount detection means includes the floor surface distance sensor 71 that is provided on the bottom surface of the vehicle body 11 and measures the distance from the floor surface F. The amount of change X in the height S of the vehicle body 11 in the front-rear direction is detected based on the change in distance, and the distance to an object present in the surroundings can be accurately measured.

The distance sensor is not limited to the laser range finder (LRF) 63, and may be another laser sensor or an ultrasonic sensor. Alternatively, a stereo camera may be used as the distance sensor.

The laser range finder (LRF) 63 is attached to the head guard 22 , but it is not limited to this, and may be provided to other parts of the vehicle body 11 .
○ Forklifts are not limited to reach-type forklifts, and may be applied to other forklifts, such as counter-type forklifts.

DESCRIPTION OF SYMBOLS 10... Unmanned forklift, 11... Vehicle body, 16... Fork, 18... Driving steering wheel, 31... Drive unit, 37... Swing cylinder, 60... Extension amount sensor, 63... Laser range finder, 64... Controller, 71... Floor distance sensor , 90... wall, S... height of vehicle body, X... amount of change.

Claims (3)

A vehicle body equipped with a fork that moves up and down at the front,
a distance sensor installed on the vehicle body for detecting a distance to an object existing around the vehicle body;
A control unit that controls traveling while estimating its own position based on the distance to the object by the distance sensor,
vehicle body height change amount detection means for detecting the amount of change in the height of the vehicle body in the longitudinal direction;
a correction means for correcting the distance to an object detected by the distance sensor based on the amount of change in the height of the vehicle body detected by the vehicle height change amount detection means ;
A rear wheel support member for supporting the rear wheel with respect to the vehicle body is supported so as to be able to swing up and down while urging the rear wheel toward the ground, and expands and contracts between the vehicle body and the rear wheel support member. A cylinder capable of
The vehicle body height change amount detection means includes an expansion/contraction amount sensor that measures the expansion/contraction amount of the cylinder, and the amount of change in the vehicle body height in the longitudinal direction based on the change in the expansion/contraction amount of the cylinder detected by the expansion/contraction amount sensor. An unmanned forklift characterized by detecting A vehicle body equipped with a fork that moves up and down at the front,
a distance sensor installed on the vehicle body for detecting a distance to an object existing around the vehicle body;
A control unit that controls traveling while estimating its own position based on the distance to the object by the distance sensor,
vehicle body height change amount detection means for detecting the amount of change in the height of the vehicle body in the longitudinal direction;
a correction means for correcting the distance to an object detected by the distance sensor based on the amount of change in the height of the vehicle body detected by the vehicle height change amount detection means ;
The vehicle body height change amount detection means includes a floor distance sensor that is provided on the bottom surface of the vehicle body and measures the distance from the floor surface. An unmanned forklift characterized by detecting a change amount of the height of the vehicle body in the longitudinal direction . 3. The unmanned forklift truck according to claim 1 , wherein said distance sensor is a laser range finder.

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