JPH0229600B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention aims to move the fork of an unmanned forklift to the height position of a pallet hole in a pallet on which a predetermined load out of multiple layers of loads is placed. The present invention relates to a device for positioning a fork in a pallet hole in an unmanned forklift for positioning a fork in a pallet hole.

Prior Art As this type of device, for example,
As disclosed in Publication No. 33600, a detector is attached to the tip of the fork, and the output signal of the detector is turned ON.
It is known that the number of stages of loads is counted by counting -OFF, and the fork is stopped at the position of the pallet hole of the pallet on which the target number of stages of loads is placed.

Problem to be Solved by the Invention In the above device, the output signal of the detector is turned on and off.
Since the number of stages of the load is counted by counting the number of stages of the load, the detector detects objects other than the pallet holes, such as the gap between the footrest and the pallet when the pallet is placed through the footrest (this (The distance between pallet holes is usually much narrower than the pallet holes) is also counted as the number of stages. cannot be positioned.

An object of the present invention is to solve the above-mentioned problems, and to improve the pallet hole of a fork in an unmanned forklift, which can accurately position the fork at the height of the pallet hole on which a target number of stages of loads are placed. The object of the present invention is to provide a positioning device for.

Means for Solving the Problems A device for positioning forks in pallet holes in an unmanned forklift according to the present invention positions the fork of the unmanned forklift at a predetermined target stage of loads stacked in multiple stages. A device for positioning a pallet on which a pallet is placed at the height of the target pallet hole, which includes a fork lifting device, a pallet hole detector attached to the tip of the fork, and a fork at a predetermined position in front of the load. a first control means for controlling the fork lifting device to raise or lower it from a predetermined height reference position; a movement amount detector that outputs a pulse every time the fork moves a predetermined distance in the vertical direction; pulse counting means for counting the number of pulses output from the movement amount detector while the detection signal is continuously output from the pallet hole detector during the fork movement by the control means; The count value counted by the pallet hole determining means and the pulse counting means determines whether the count value is within a predetermined range predetermined corresponding to the vertical distance between the pallet holes. stage number counting means for updating the counted value when it is determined by the pallet hole determining means that the number is within the range;
a stage number determining means for determining whether the counted value of the stage number counting means matches a predetermined target number of stages; A second control means is provided for controlling the fork lifting device so that the fork stops at the height position of the target pallet hole when the determination is made.

Function The device for positioning a fork in a pallet hole in an unmanned forklift according to the present invention includes a fork lifting device, a pallet hole detector attached to the tip of the fork, and a fork at a predetermined position in front of a load. Since the first control means is provided for controlling the fork lifting device to raise or lower the fork from the height reference position, the fork is raised or lowered by the lifting device, and the pallet is lifted or lowered as the fork is raised or lowered. The hole detector is raised or lowered.

Furthermore, a movement amount detector that outputs a pulse every time the fork moves a predetermined distance in the vertical direction, and a movement amount detector that outputs a pulse every time the fork moves a predetermined distance in the vertical direction; The pulse counting means for counting the number of pulses output from the quantity detector and the count value counted by the pulse counting means are within a predetermined range predetermined corresponding to the vertical distance of the pallet hole. Since the pallet hole determination means is provided to determine whether the pallet hole is in If the count value is within a predetermined range that corresponds to the vertical distance between the pallet holes, it is determined that the pallet hole detector has passed through the position facing the pallet holes. It will be judged.

Further, when the count value counted by the pulse counting means is determined by the pallet hole determining means to be within the predetermined range, the count value is updated by the stage number counting means and the counter of the stage number counting means. a stage number determining means for determining whether the numerical value matches a predetermined target number of stages; and when the stage number determining means determines that the counted value of the stage number counting means matches the predetermined target number of stages; ,
Since the second control means is provided to control the fork lifting device so that the fork stops at the height position of the target pallet hole, the count value counted by the pulse counting means is within the above-mentioned predetermined range. When the pallet hole determining means determines that there is a hole, the count value of the stage number counting means is updated, and when it is determined that the updated count value matches the predetermined target number of stages, the fork moves to the target pallet. It is stopped at the height of the hole.

Embodiments Hereinafter, embodiments in which the present invention is applied to an unmanned forklift that travels along guide lines, light reflectors, etc. will be described with reference to the drawings.

FIGS. 1 and 2 show a plurality of loads stacked in a predetermined cargo storage area and an unmanned forklift stopped at a predetermined position in front of the cargo storage area.

In this example, three loads 1 of different heights are stacked at the load storage area. 1 load each
are placed on pallets 2 having fork insertion holes (pallet holes) 3 so that they can be loaded and unloaded by an unmanned forklift 4. Each palette 2 is the same.

A pair of left and right forks 5 of unmanned forklift 4
First and second reflective photoelectric switches 6L and 6R are attached to the tips of L and 5R, respectively, facing forward. Each photoelectric switch 6L, 6R
It turns on when an object such as the following is detected. Therefore, when each photoelectric switch 6L, 6R is in the desired position in the pallet hole 3 of the pallet 2, each photoelectric switch 6L, 6R is turned off.

A rotary encoder 8 is attached to the mast 7 of the unmanned forklift 4. The rotation axis of the rotary encoder 8 is a fork 5L, 5
It is designed to be rotated via a mechanism (not shown) that converts the vertical movement of R into rotational movement. Therefore, from rotary encoder 8, fork 5
A pulse is output every time L and 5R move a predetermined distance in the vertical direction.

When loading, for example, the topmost (third stage) load 1 out of the three loads 1 placed at the storage area onto the unmanned forklift 4, the fork positioning device provided on the unmanned forklift 4 Therefore, the forks 5L and 5R are automatically positioned at the height of the pallet holes 3 of the third stage pallet 2.

FIG. 3 shows the electrical configuration of the fork positioning device. The fork positioning device is controlled by a central processing unit (CPU) 10 that controls each part of the unmanned forklift 4. CPU10 is
It is equipped with a ROM 11 for storing the program and a RAM 12 for storing various data.

A detection signal from the first photoelectric switch 6L, a detection signal from the second photoelectric switch 6R, and a pulse signal from the rotary encoder 8 are input to the CPU 10 via an input interface 13.

From the CPU 10, command signals for raising, lowering, and stopping the fork are sent via the output interface 14 to a drive control device 15 for a lift cylinder 16 for raising and lowering the fork, such as a drive circuit for an electromagnetic proportional valve.

Figure 4 shows the contents of the RAM. RAM1
2 is an area E used as a pulse counter (count value is indicated by P) for pallet hole determination.
1. Area E2 used as a pulse counter for centering (count value indicated by Q); Area E3 used as a stage number counter (count value indicated by R); Area E4 for storing reference value L for pallet hole determination; Area E that stores the tolerance value α
5. Area E for storing reference value M for centering
6. An area E7 for storing the set number of loading stages N is provided.

The reference value L for pallet hole judgment is the number of pulses output from the rotary encoder 8 while the forks 5L and 5R move vertically over a distance corresponding to the height of the pallet hole 3, and is determined in advance and is It is stored in Elijah E4. As will be described later, in this positioning device, the number of pulses output from the rotary encoder 8 while the photoelectric switches 6L and 6R are off while the fork is rising (counted by the pallet judgment pulse counter) is within the range (L±α) from the reference value L for pallet hole determination to the allowable value α (L±α), it is determined that the pallet hole 3 has been detected. The allowable value α is also predetermined and stored in area E5.

The reference value M for centering is fork 5L, 5
The fork 5 at the time when the photoelectric switches 6L and 6R stop detecting the pallet hole 3 from the state in which they are detecting the pallet hole 3 while R is rising (the photoelectric switches 6L and 6R change from OFF to ON).
The distance between the height center position of L and 5R and the center position of the pallet hole 3 is the number of pulses output from the rotary encoder 8 while the forks 5L and 5R move in the vertical direction, and is determined in advance. and stored in area E6.

The set number of loading stages N is the number of stages of the lowest load 1 among the loads 1 to be loaded onto the unmanned forklift 4, and is transmitted from, for example, a stage number input device (not shown) or a control center (not shown). in advance from a communication control device (not shown) that receives commands.
Area E7 of RAM 12 that is input to CPU 10
is memorized.

FIG. 5 shows the fork positioning processing means by the CPU 10, and FIG. 6 shows the positions and on/off states of the photoelectric switches 6L and 6R during fork positioning processing, and the count values P, Q, R of each counter (areas E1, E2, Contents of E3) Indicates a change.

Here, of the three loads 1 placed at the storage area as shown in FIGS. 1 and 2, the case where the topmost (third stage) load 1 is loaded onto the unmanned forklift 4 will be explained. The fork positioning process will be explained. Therefore, the set number of loading stages N is three. The fork positioning process involves moving the unmanned forklift 4 to a predetermined position in front of the cargo 1 placed at the cargo storage area.
This is carried out after the forks 5L and 5R have been positioned at a predetermined reference height position U by known means. In this example, the reference height position U is set at a position slightly above the lowermost (first stage) pallet 2, as shown in FIG.

When the forks 5L and 5R are positioned at the reference height position U (time t1), the centering pulse counter and the stage number counter are cleared, that is, the contents Q and R of areas E2 and E3 are set to zero (step t1). (twenty one)). Then, a fork lift command signal is output (step (22)) and sent to the drive control device 15. As a result, Fork 5L,
5R is raised.

Next, the on/off state of the first photoelectric switch 6L is checked (step (23)), and if it is off, the process moves to pallet hole and stage number detection processing by the first photoelectric switch 6L (step (25)). If 6L is on, the on/off state of the second photoelectric switch 6R is checked (step (24)), and if it is off, the process moves to pallet hole and stage number detection processing by the second photoelectric switch 6R (step (26)). .
If the second photoelectric switch 6R is also on, the process returns to step (23).

Immediately after forks 5L and 5R start rising in step (22) above, both photoelectric switches 6
L and 6R are located at a reference height position U above the pallet 2 on the first stage, and are turned on when the load 1 on the first stage is detected. Therefore, NO at step (23), NO at step (24),
Steps (23) and (24) are repeated.

When the forks 5L, 5R rise and each photoelectric switch 6L, 6R detects the pallet hole 3 of the second stage pallet 2, each photoelectric switch 6L, 6R is turned off. The point at which each photoelectric switch 6L, 6R turns off generally deviates depending on the inclination of the pallet 2 and the like. Here, it is assumed that the first photoelectric switch 6L is turned off before the second photoelectric switch 6R.
When the first photoelectric switch 6L is turned off (time t2),
The answer to step (23) is YES, and the process moves to step (25), where the first photoelectric switch 6L performs pallet hole and stage number detection processing.

In this pallet hole and stage number detection process, first, the pallet hole determination pulse counter is reset, that is, the content P of area E1 of the RAM 12 is made zero (step (41)).

Next, it is determined whether the first photoelectric switch 6L is off (step (42)), and since it is off, the process advances to step (43) and reading of pulses from the rotary encoder 8 is started. Ru. When the pulse from the rotary encoder 8 is input, the content P of the area E1 of the RAM 12, which is used as a pulse counter for pallet hole determination, is incremented by 1 and updated (step (44)).
Then, it is determined whether the first photoelectric switch 6L is off (step (45)), and if it is still off, the process returns to step (43) and waits for the next pulse input from the rotary encoder 8. . When the next pulse is input, the content P of area E1 of RAM 12 is incremented by 1 and updated (step (44)). Then, it is determined again whether the first photoelectric switch 6L is off (step (45)), and if it remains off, the process returns to step (43).

While repeating steps (43) to (45) in this way, the first photoelectric switch 6L switches to the second photoelectric switch 6L.
When the first photoelectric switch 6L is turned on (time t3) by moving above the pallet hole 3 of the pallet 2 in the third stage, the state becomes NO at step (45), and the RAM is turned on.
Contents P of area 12 (corresponds to the number of pulses output from the rotary encoder 8 between when the first photoelectric switch 6L is turned off at time t2 and when the first photoelectric switch 6L is turned on at time t3) ) is the allowable value α centered on the reference value L for pallet hole judgment.
Whether it is within the range ((L-α)≦P≦(L+
α)) is examined (step (46)).

As mentioned above, when the first photoelectric switch 6L detects the pallet hole 3, P is within the above range (L±α), so the process moves to step (47) and is used as a stage number counter. RAM1
The content R of area E3 of No. 2 is incremented by +1 and updated. Then, the number S (=R+1) obtained by adding 1 to the contents R of area E3 of the RAM 12 is the set number of loading stages N (=
3) is determined (step (48)). When the pallet has finished passing through the pallet hole 3 of the second pallet 2 as described above, it will proceed to step (47).
Since R=1 and S=2, S and the set number of loading stages N are not equal. Therefore, the result in step (48) is NO, and the process returns to step (41).
The pulse counter for pallet hole judgment is cleared (P=
0) to be done. Then, wait until the first photoelectric switch 6L is turned off (step (42)).

The first photoelectric switch 6L is the third stage pallet 2.
When pallet hole 3 is detected and turned off (at the time
t4), and from that point until the first photoelectric switch is turned on (time t5), the rotary encoder 8
The number of pulses output from the area E1 is counted (steps (42) to (45)), and the count value (area E1
It is determined whether P is within the range (L±α) (step (46)). In this case as well, since P is within the range of (L±α), the content R of area E3 is +1 and becomes R=2 (step (47)).
Then, S (=R+1) and N are compared. In this case, since S and N match (S=N=3), the pallet hole and stage number detection process is completed.

In the above step (46), the first photoelectric switch 6L checks whether P is within the range (L±α) when the first photoelectric switch 6L detects the object other than the pallet hole 3, for example, when the load 1 is placed on the pallet 2 with a footrest. When a hole (space) between the footrest and the pallet 2 is detected and the pallet 2 is placed on the pallet 2, the contents of area E3 of the RAM 12 are updated based on the detection of this hole. This is to prevent this from happening. That is, when a hole other than the pallet hole 3 is detected and the first photoelectric switch 6L is turned off, the pulse output from the rotary encoder 8 while the first photoelectric switch 6L passes in front of that hole is The number is counted by the above steps (43), (44), and (45), but since the height of the hole is generally not equal to the height of the pallet hole 3, the count value P in this case is within the range ( Do not fall within L±α). Therefore, in this case, the answer is NO in step (46), and the process returns to step (41) without proceeding to step (47), so that the content R of area E3 of RAM 12 is not updated.

When the pallet hole and number of stages detection process (step (25)) is completed, the process moves to step (27), where a fork stop command signal is output (step (27)) and sent to the drive control device 15. This causes the forks 5L and 5R to stop. Subsequently, a fork lowering command signal is output (step (28)) and sent to the drive control device 15. As a result, the forks 5L and 5R are lowered. When the forks 5L and 5R start descending, reading of pulses from the rotary encoder 8 starts (step (29)).

When a pulse is input, area E2 of RAM 12, which is used as a pulse counter for centering.
The content Q is incremented by +1 and updated (step (30)). Then, it is determined whether the updated content Q is equal to the centering reference value M (step (31)). If they are not equal, step 2
Return to step 9 and wait for the next pulse input. When the next pulse is input, the content Q of area E2 increases by +1.
It is determined whether the updated content Q is equal to M (step (31)), and if they are not equal, the process returns to step (29). In this way, step (29)~
(31) is repeated, and in step (31) Elijah
When the content Q of 2 becomes equal to the centering reference value M (time t6), a fork stop designation signal is output (step (32)) and sent to the drive control device 15. This causes the forks 5L and 5R to stop. In this case, the height center position of fork 5L is
It comes to the height center position of the pallet hole 3 of the third stage pallet 2.

Next, the on and off states of the first photoelectric switch 6L and the second photoelectric switch 6R are checked in sequence (steps (33) and (34)), and if both switches 6L and 6R are off, the positioning process ends. . If either switch 6L or 6R is on, it is determined that there is an abnormality in the positioning process or that the pallet 2 of the load 1 to be loaded is tilted too much, and an abnormality signal is output. An alarm device (not shown) etc. is activated (step (35)). In this case, it is determined that loading is not possible and the positioning process ends.

By upper positioning process, fork 5L, 5R
When the positioning of forks 5L and 5R is completed,
(or the unmanned forklift 4) is advanced (or moved forward) and the forks 5L and 5R are inserted into the pallet holes 3 of the third stage pallet 2. Then, Fork 5L and 5R were raised, and Fork 5L and 5R were raised.
5R (or the unmanned forklift 4) is moved back (or retreated), the forks 5L and 5R are lowered, and the third stage load 1 is loaded onto the unmanned forklift 4. This cargo 1 is then transported to a predetermined unloading location by an unmanned forklift 4.

In the above embodiment, a case has been described in which the first photoelectric switch 6L is turned off before the second photoelectric switch 6L after the forks 5L and 5R are raised in step (22). If the photoelectric switch 6R is turned off before the first photoelectric switch 6L, the second photoelectric switch 6R performs pallet hole and stage number detection processing (see steps (23), (24), and (26)). The pallet hole and stage number detection processing by the second photoelectric switch 6R is almost the same as the detection processing by the first photoelectric switch 6L described above, and the first photoelectric switch 6L is turned on and off in steps (42) and (45). The only difference is that instead of checking the state, the on/off state of the second photoelectric switch 6R is checked, so a description thereof will be omitted.

In the above embodiment, the case where the third stage load is loaded has been explained, but the above positioning device can also be used when loading both the second stage load and the third stage load at the same time. The fork can be positioned. In this case, the set number N of loading stages may be set to 2.

Further, in step (48), the value S obtained by adding 1 to R and the set number of loading stages N is compared, but R may be compared with the value obtained by subtracting 1 from N. Also, 1 more than the number of stages of cargo to be loaded.
Set a small value as the set number of loading stages N,
You may also compare R and N.

In addition, the reference height position U of forks 5L and 5R
may be set at the height center position of the first stage pallet 2. Also, the thickness of Fork 5L and 5R is
If the plate thickness is smaller than the thickness of the pallet 2 (thickness between the lower surface of the pallet and the lower surface of the pallet hole), the reference height position U may be the position where the lower surfaces of the forks 5L and 5R touch the floor surface. In this case, the pallet hole 3 of the first pallet 2 is also detected by the pallet hole and stage number detection process and counted by the stage number counter, so in step (48), area E3 is detected. It is checked whether the contents R and the set number N of loading stages match.

Furthermore, the reference height position U of fork 5L, 5R
is set at a position higher than the expected maximum height position of the uppermost pallet 2, and the forks 5L and 5R are lowered from that position, and the set number of loading stages (in this case In this case, the forks 5L and 5R are stopped when the pallet holes 3 are detected (the number of loading stages is set as the first, second... nth stage in order from the top), and the forks 5L and 5R are set to the reference value M for centering. Fork positioning may be performed by raising the corresponding distance.

Effects of the Invention According to this invention, the fork is raised or lowered by the lifting device, the pallet hole detector is raised or lowered as the fork is raised or lowered, and the pallet hole detector is moved to a position facing the pallet hole. Then, the movement amount detector outputs pulses corresponding to the movement amount, the output pulses are counted by the counting means, and the counted value falls within a predetermined range corresponding to the vertical distance of the pallet hole. If the pulse counting means is within the predetermined range, it is determined that the pallet hole detector has passed through the position facing the pallet hole. When this is determined, the count value of the stage number counting means is updated, and when it is determined that the updated count value matches the predetermined target number of stages, the fork stops at the height position of the target pallet hole. Therefore, the fork can be accurately positioned at the height of the pallet hole of the pallet on which the target number of stages of loads are placed.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIGS. 1 and 2 show the appearance of a plurality of loads stacked on a cargo storage area and an unmanned forklift, and FIG. 1 is a front view; Fig. 2 is a plan view, Fig. 3 is a block diagram showing the electrical configuration of the fork positioning device, Fig. 4 is a diagram showing the contents of the RAM, Fig. 5 is a flowchart showing the positioning processing procedure by the CPU, Fig. 6 The figure is a time chart showing the height position of the fork, the on/off state of the photoelectric detector, and the count value of each counter during the positioning process. 1...Load, 2...Pallet, 3...Pallet hole, 4...Unmanned forklift, 5L, 5R...
Fork, 6L, 6R... Opposite type photoelectric switch,
8...Rotary encoder, 10...CPU,
11...ROM, 12...RAM, 15...drive control device.

Claims (1)

[Scope of Claims] 1. Positioning the fork of an unmanned forklift at the height of a target pallet hole of a pallet on which a load of a predetermined target level is placed among loads loaded in multiple stages. A fork lifting device, a pallet hole detector attached to the tip of the fork, and a fork lifting/lowering device to raise or lower the fork from a predetermined height reference position at a predetermined position in front of the load. A first control means for controlling the device, a movement amount detector that outputs a pulse every time the fork moves a predetermined distance in the vertical direction, and a detection signal is continuously output from the pallet hole detector while the fork is being moved by the first control means. pulse counting means for counting the number of pulses output from the movement amount detector while the pulses are being output;
A pallet hole determining means for determining whether or not the pallet hole is within a predetermined range corresponding to the vertical distance between the pallet holes, and a count value counted by the pulse counting means,
A stage number counting means whose count value is updated when the pallet hole determination means determines that it is within the predetermined range; The fork is configured to stop at a height position of the target pallet hole when the stage number determining means determines that the counted value of the stage number determining means and the stage number counting means match a predetermined target number of stages. A device for positioning a fork in a pallet hole in an unmanned forklift, comprising: second control means for controlling a fork lifting device.