JPS6240280B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling cargo handling operations in an unmanned forklift.

In general, an unmanned forklift is guided unmanned along a guide cable laid on a travel path, and when moved to a cargo storage position, it automatically performs cargo pick-up or cargo loading operations. When carrying out this loading work or loading work, if the loads W1 to W3 are normally stacked on pallets P1 to P3 as shown in Fig. 1a, the loads are mounted on the forklift. The left and right pair of forks 6 and 7 correspond well to the holes M in the third pallet P3, allowing for smooth loading and unloading of the second pallet W2.
The work of placing the load W3 on top of the load W3 can also be carried out smoothly without causing any problems.

However, as shown in Fig. 1b, the load W1 in the lowest tier collapses, and the pallets P in the second and third tiers collapse.
2, P3 and the loads W2, W3 are inclined, a pair of forks 6,
7 cannot be inserted at the same time, and if you try to move the forklift forward to pick up goods with forks 6 and 7 as shown in FIG. There is a defect in that the load W3 on the third tier is pushed by the load W3, causing an accident in which the load W3 falls.

Also, as shown in Figure 1c, the third stage pallet P
Even when the pallet P3 and the load W3 are moving laterally, one of the forks 6 and 7 will come off the pallet P3, so it is dangerous to carry out the load handling operation. It is also very dangerous to place the load W3 in a state where the load W2 is displaced laterally.

The present invention was made in order to eliminate the above-mentioned defects, and its purpose is to allow the loading operation or loading operation to be performed when the load is normally loaded at the loading position, and to prevent the load from collapsing and causing abnormalities. To provide a cargo handling work control method for an unmanned forklift capable of preventing cargo falling accidents and improving safety by stopping cargo pick-up work or cargo loading work when the condition is present.

An embodiment embodying the present invention is shown in FIGS.
To explain FIG. 11, 1 in FIG. 2 is an unmanned forklift that is guided unmanned along a guidance cable (not shown) laid in advance on the ground R.
A pair of left and right forks 6 and 7 are mounted in front of the vehicle body 2 and are moved up and down by an outer mast 3, an inner mast 4, a lift cylinder 5, and the like.

A load W1 is placed at a load position on the ground R via a first pallet P1, and a load W2 is placed on the upper surface of the load W1 via a second pallet P2.

At the tips of the pair of forks 6 and 7, a third
As shown in the figure, a light reflecting type right fork tip sensor 10 and a left fork tip sensor 11 each consisting of a light emitter 8 and a light receiver 9 are installed. These fork tip sensors 10 and 11 are configured so that the light beam emitted from the light emitter 8 is reflected by the surfaces of the loads W1 and W2 and enters the light receiver 9, and the light beams emitted from the light emitter 8 are reflected by the surfaces of the loads W1 and W2 and enter the light receiver 9. As shown in FIG. 4, the output voltage V changes depending on the distance L from the tip of the pin 7. That is, in this embodiment, the longer the distance L, the higher the output voltage V.
increases proportionally, and this output voltage V is output as a fork destination signal.

Load number sensors 12 and 13 are attached to the outer surface of the outer mast 3 so as to be able to adjust the angle forward and upward to detect the presence or absence of second and third loads W2 and W3. These loading stage number sensors 12, 13 are also of a light emitting/receiving type,
3, a load detection signal is output by receiving the light reflected from the loads W2 and W3.

FIG. 5 shows a traveling control and cargo handling control circuit of an unmanned forklift, in which 14 to 17 are first to fourth comparators, and the first and second comparators 14 and 15 are connected to the right fork tip sensor 10. The output voltage V from is inputted,
The output voltage V from the left fork tip sensor 11 is input to the third and fourth comparators 16 and 17. Further, a constant voltage v1 is inputted to the first and third comparators 14 and 16 from a separately provided constant voltage generation circuit (not shown), and a constant voltage v2 is inputted to the second and fourth comparators 15 and 17. It is now being entered.

A 10R circuit 18 is connected to the first and third comparators 14 and 16 to output the operating signal S5, and the second and fourth comparators 15 and
17 is connected to a 20R circuit 19 for outputting an operation signal S6. Further, the first and third comparators 14 and 16 receive an operating signal S7.
An AND circuit 20 for outputting is connected.

The first and second OR circuits 18 and 19 are connected to a control device 21, such as a computer, mounted on the upper part of the forklift, as shown in FIG. This control device 21 outputs, for example, a fork stop signal S9, a cargo pick-up stop signal S1, as will be described later.
0 or a loading stop signal S11 or the like is output.

Next, the operation will be described in the case where the unmanned forklift configured as described above performs second-stage cargo collection.

Now, in FIG. 2, when the unmanned forklift is traveling unmanned at high speed in the direction approaching the load W1 along the guidance cable (not shown), the load W1
When the distance L between the forks 6 and 7 becomes 40 cm and the voltage V output from the right and left fork tip sensors 10 and 11 becomes less than v1, the operation signals S1 and S3 are output from the first and third comparators 14 and 16. The operation signal S5 is outputted from the 10R circuit 18, and therefore the deceleration signal S5' is outputted from the control device 21, and the forklift is switched from high speed to low speed. Note that the operation signals S1 and S3 are AND
The signal is also input to the circuit 20, and the operation signal S7 is output from the AND circuit 20, but since the forklift is being controlled, the control device 21 makes it an invalid signal.

Furthermore, the forklift moves forward and the distance L
becomes 20cm, right and left fork tip sensors 10,1
When the voltage V output from the circuit 1 becomes equal to or lower than v2, the operation signals S2 and S4 are output from the second and fourth comparators 15 and 17, and therefore the 20R circuit 1
9 outputs an operation signal S6, and therefore a stop signal S6' is output from the control device 21, and the forklift is stopped 20 cm in front of the load W1.

In addition, since the first and second OR circuits 18 and 19 are used in this embodiment, if the output voltage V of either one of the fork tip sensors 10 and 11 becomes below v1 or v2, the first 1OR circuit 18
An operation signal S5 is output from the second OR circuit 19, and an operation signal S6 is output from the second OR circuit 19.

When the signals from the loading stage number sensors 12 and 13 come to be recognized as valid signals by the control device 21 in synchronization with the stoppage of the forklift, the second stage load W2 is detected by the loading stage number sensor 12. When the number of stages of the load is detected in this way, the control device 21 outputs a load command signal S8 for picking up the load W2, and the forks 6 and 7 are raised from the fork lift height F (height from the ground is 50 cm, for example) when traveling. Then, the cargo picking operation is performed by the cargo picking sequence control of the control device 21.

By the way, in this embodiment, as shown in FIG. 2, the height position calculated to correspond to the center C of the hole M in the second pallet P2 is set as the reference lifting height position H for loading.
The control device 21 stores this reference lifting height position H, the upper limit position H1 of the detection range H1, and the lower limit position H2 of the detection range, which are respectively displaced by a certain distance h (for example, 20 cm) upward and downward from the lifting height position H. Based on these positions H, H1, and T2, the pallet P2 is searched as follows.

When the forks 6 and 7 rise, move to the upper limit position H1 and are stopped, both fork tip sensors 1
The signals from 0 and 11 are recognized as valid signals by the control device 21, and the control device 21 switches so that the operation signal S7 from the AND circuit 20 becomes a valid signal.

Thereafter, the forks 6 and 7 are lowered from the upper limit position H1 to the lower limit position H2, and the operation of digging holes in the pallet P2 is finally started, but the cargoes W1 and W2 are normal as shown in FIG. Sometimes, since the distance L between the fork tip sensors 10, 11 and the load W2 is both 20 cm, both sensors 10, 1
The output voltage V from 1 is both v2,
Since the operation signals S1 and S3 are not output to the first and third comparators 14 and 16, the AND circuit 20
The operation signal S7 is never outputted from.

Furthermore, forks 6 and 7 descend to release the pallet P.
When the hole M is moved to a position corresponding to the upper edge t of the hole M, the light emitted from both sensors 10 and 11 is transmitted to the hole M.
As a result, the output voltages V from both sensors 10 and 11 become equal to or higher than v1, and the AND circuit 20 outputs the operation signal S7 to the control device 21. When both forks 6 and 7 move from the upper edge t of the hole M to the center C, a stop signal S9 for the forks 6 and 7 is output from the control device 21, and the digging operation is completed. Thereafter, the control device 21 transfers control to the next step of the cargo picking sequence control.

By the way, as mentioned above, when the forks 6 and 7 are moved to the upper edge t of the hole M of the pallet P2,
The AND circuit 20 immediately outputs the operation signal S7, but the forks 6 and 7 must not be stopped until they are moved to the center C of the hole M. Therefore, in this embodiment, the control device 21 The stop signal S9 is output only when the fork is moved to the center C of the hole M by a lift height signal from a timer (not shown) or a lift height detection device (not shown).

Next, while the forks 6 and 7 are digging holes in the pallet P2, if the loads W1 and W2 are collapsed as shown in FIG.
When the forks 6 and 7 descend a certain distance from 1, one of the forks 6 first corresponds to the upper edge t of the pallet hole M, and the output from the fork tip sensor 10 exceeds v1. Then, when the fork 6 crosses the lower edge b of the pallet hole M, the fork 7
However, in this state, the output voltages V from both sensors 10 and 11 will not exceed v1, so the AND circuit 2
0, the operation signal S7 is not output, and as a result, the control device 21 outputs the loading stop signal S10, and the forks 6 and 7 are lowered and stopped moving to the lowest position, and the forklift also remains stopped. Retained.

Furthermore, if the inclination of pallet P2 is relatively gentle, the outputs of both fork tip sensors 10 and 11 may become equal to or higher than v1 at the same time, and the operation signal S7 may be output. If the signal S7 is checked and the signal S7 is output, it is determined to be normal and the process proceeds to the next step of the cargo picking sequence control.

In the case of an abnormal load as shown in FIG. 8, when carrying out the loading operation, the forks 6 and 7 start descending from the upper limit position H1, and at the same time one of the forks 7 does not correspond to the load W2, and the fork sensor 1
Since the output of the sensor 1 becomes v1 or more and the output of the fork tip sensor 10 becomes v2 or less, an abnormality is detected, and the forks 6 and 7 are lowered and stopped at the lowest position, and the forklift is also stopped.

Next, the third tier load W3 is placed on top of the second tier load W2.
This section explains the cargo loading work.

In this case, as shown in Figure 9, the second stage load W
The point where the forks 6 and 7 are moved upward by a certain distance from the upper surface of the load W2, that is, the distance that allows the forks 6 and 7 to advance above the load W2, is set as the reference lifting height position H, and the forks 6 and 7 with the load placed thereon are stopped and the The lift is moved forward to perform cargo loading work.
The control device 21 also determines the reference lifting height position H and the lower limit position H2 of the detection range that is displaced downward by a certain distance h (for example, 20 cm) from the lifting height position H.
Based on these positions H and H2, the load position detection operation of the forks 6 and 7 is performed as follows. In this embodiment, it is not necessary to set the upper limit position of the detection range above the reference position H, and this reference position H becomes the upper limit position.

When the forks 6 and 7 rise and are moved to the lower limit position H2, the control device 21
Switching is performed so that the operation signal S7 from the AND circuit 20 becomes a valid signal.

Thereafter, the forks 6 and 7 are raised from the lower limit position H2 toward the reference position H, and the fork cargo position detection operation is finally started.
As shown in the figure, when the loads W1 and W2 are normal, the distances L between the first forks 6 and 7 and the load W2 are both 20 cm, so the voltage v2 is output from both sensors 10 and 11, respectively. After the forks 6 and 7 pass the upper surface of the load W2, the light emitted from both the sensors 10 and 11 is not reflected, and the outputs from the sensors 10 and 11 both exceed v1, so the AND circuit 20 The operation signal S7 is output. If the signal S7 is continuously output until the forks 6 and 7 are moved to the reference position H,
A fork stop signal S9 is output from the control device 21, the forks 6 and 7 are stopped at a constant height position from the top surface of the load W2, and control is transferred to the next step of the load placement sequence control.

On the other hand, in the cargo position detection operation of the forks 6 and 7 described above, when the second stage cargo W2 is collapsed as shown in FIG. 10, when the fork rises a certain distance from the lower limit H2, one of the The fork 7 first passes over the top surface of the load W2, and the voltage v1 is output from the fork tip sensor 11. A little later, the other fork 6 passes over the top surface of the load W2, and the voltage v1 is output from the fork tip sensor 10. Ru. At this time, different voltages v1 and v from both sensors 10 and 11
When the time J for outputting 2 exceeds the reference time K stored in the control device 21, the control device 21 outputs a loading stop signal S11, the forks 6 and 7 are lowered and stopped at the lowest position, and the forklift is stopped. will also be suspended.

Furthermore, when the cargo is in an abnormal state as shown in FIG.
2, the output of the fork tip sensor 11 is v
1 or more and the output of the fork tip sensor 10 becomes v2 or less, an abnormality is detected, and the forks 6 and 7 are lowered and stopped at the lowest position, and the fork lift is also stopped.

Now, in the embodiment of the present invention, while the pair of forks 6 and 7 descend from the detection upper limit position H1 to the lower limit position H2, both fork tip sensors 10 and 11
When the forks 6 and 6 continue to detect no obstacles while moving within a certain detection range at almost the same time, this is considered normal and the fork 6 is placed at the center C of the hole M in the pallet.
7 is stopped and the cargo picking operation continues, and on the other hand, if one of the two fork-end sensors detects an obstacle and the other sensor does not detect an obstacle, this continues for a certain detection range. Since this is regarded as an abnormality and the loading operation is stopped, safety can be improved by stopping loading loading when the load collapses.

Further, in the embodiment of the present invention, while the pair of forks 6 and 7 are rising from the detection lower limit position H2 to the reference position H, the fork tip sensors 10 and 11 are continuously moved almost simultaneously and within a fixed detection range. When no obstacle is detected, it is assumed that this is normal and the fork is stopped at a predetermined position for loading the cargo to continue the loading operation. When an obstacle is detected and the other sensor does not detect the obstacle for a certain period of time, this is treated as an abnormality and the loading operation is stopped. Can be stopped to improve safety.

Note that the embodiments of the present invention can also be embodied in the following embodiments.

(1) In the embodiment described above, when the forks 6 and 7 are lowered from the upper limit position H1 to the lower limit position H2 during the loading operation, the pallet P2 is searched, but when both positions H2 and H1 are raised. Try to do some digging from time to time.

(2) In the above embodiment, when loading cargo, the lower limit position H
When raising the fork from 2 to the reference position H, the cargo position detection operation was performed.
The detection operation is performed when the fork descends from the reference position H to the lower limit position H2.
In this case, it is necessary to raise the fork when the cargo is normal.

(3) By inputting the operation signals S1 to S4 directly to the control device 21 without assembling the AND circuit 20 and the OR circuits 18 and 19 with hardware, the AND circuit 20 and the OR circuit 1
8, 19 etc. should be handled by software.

As described in detail above, the present invention is an excellent invention as a method for controlling cargo handling operations of an unmanned forklift, since it is possible to improve safety by stopping loading operations and loading operations when cargo collapses.

[Brief explanation of the drawing]

1A to 1C are front views showing the state of cargo, FIG. 2 is a right side view showing an embodiment of an unmanned forklift used in the cargo handling control method of the present invention, and FIG. is an enlarged perspective view of the tip of the fork,
FIG. 4 is a graph showing the voltage characteristics of the fork tip sensor, FIG. 5 is a cargo handling control circuit diagram, and FIGS. 6 to 11 are front views for explaining cargo handling operations. Unmanned forklift...1, Fork...6,
7. Right (left) fork tip sensor...10,11,
AND circuit...20, distance between fork tip and load...L, sensor output voltage...V, v1, v2,
Load...W1 to W3, Pallet...P1 to P3, Reference lifting height position...H, Upper (lower limit) position of detection range...H1, H2, Time...J, Reference time...K,
Signal...S7 to S11.

Claims (1)

[Scope of Claims] 1. A control device installed on an unmanned forklift detects upper and lower detection limit positions that are respectively displaced by predetermined distances upward and downward from the fork reference lifting height position for loading or unloading operations. It is stored in advance, and while the pair of forks moves between the detection upper limit position and the detection lower limit position, the fork tip sensors attached to the tips of the pair of forks move simultaneously and within a fixed detection range. When an obstacle is not detected continuously, this is regarded as normal and the loading operation or loading operation is continued, and conversely, when one of the pair of fork-end sensors detects an obstacle. A method for controlling cargo handling work in an unmanned forklift, characterized in that when the other sensor does not detect an obstacle for a certain detection range, this is regarded as an abnormality and the cargo handling work or cargo loading work is stopped. 2. While the pair of forks is moving from the upper detection limit position above the reference lifting height position corresponding to the center of the pallet hole of the uppermost load to the lower detection limit position below, the pallet A method for controlling cargo handling work in an unmanned forklift according to claim 1, wherein the forklift performs a hole digging operation. 3. While lowering the fork from the upper detection limit position to the lower detection limit position, if the loaded pallet is tilted and it is impossible to dig holes in the pallet, the fork is moved to the lowest position and stopped, and the automatic fork lift A method for controlling cargo handling work in an unmanned forklift according to claim 2, wherein the cargo handling work is stopped by stopping the operation. 4. The loading position of the fork is detected while the pair of forks moves from the lower detection limit position, which is lower than the reference position, which is slightly higher than the height of the load on the top shelf, to the reference position for loading work. A method for controlling cargo handling operations in an unmanned forklift according to claim 1. 5. While raising the fork from the lower detection limit position to the reference position, if the fork's loading position cannot be detected due to cargo collapse, the fork is moved to the lowest position and stopped, and the automatic operation of the fork lift is stopped. A method for controlling cargo handling work in an unmanned forklift according to claim 4, wherein cargo handling work is stopped.