Control method, control device, and control system for detecting abnormality in automatic forklift operation

Patent metadata

Field	Value
Publication number	US-12454448-B2
Application number	US-202318315038-A
Country	US
Kind code	B2
Filing date	May 10, 2023
Priority date	May 30, 2022
Publication date	Oct 28, 2025
Grant date	Oct 28, 2025

Abstract

A control system configured to control a forklift to unload a transport pallet onto an unloading place includes a control device configured to control at least one of movement of the forklift and horizontal movement of a fork, the forklift including a load sensor configured to detect load of an item placed on the fork, and a lift height sensor configured to detect a lift height of the fork, control raising and lowering of the fork, acquire load information of the transport pallet placed on the fork and lift height range information, the lift height range information indicating a lift height range, the lift height range being a range of height in which the fork is able to be inserted when unloading onto the unloading place is successful, and determine whether an abnormality is present.

First claim

What is claimed is:

1. A control method for controlling a forklift to unload a transport pallet onto an unloading place, the forklift including a load sensor configured to detect load of an item placed on a fork, and a lift height sensor configured to detect a lift height of the fork, the control method comprising:
acquiring load information of the transport pallet placed on the fork and lift height range information, the lift height range information indicating a lift height range, the lift height range being a range of height in which the fork is estimated to be positioned when unloading onto the unloading place is successful, the lift height range being determined based at least on a height of the unloading place;
performing a lowering operation based on the acquired load information and the acquired lift height range information, the lowering operation being an operation of lowering the fork with the transport pallet from above the unloading place;
performing an operation of pulling out the fork when a load value detected by the load sensor is equal to or less than a predetermined value and a lift height value detected by the lift height sensor is within the lift height range; and
determining that an abnormality is present when one of a first condition and a second condition is satisfied during the lowering operation, wherein:
the first condition is a determination by a processor that the lift height value is equal to or less than a lower limit value of the lift height range,
the second condition is a determination by the processor that the load value is equal to or less than the predetermined value and the lift height value is equal to or larger than an upper limit value of the lift height range,
the lift height value is a numerical height value detected by the lift height sensor on the forklift, and the lift height range is a range of numerical values starting from the lower limit value to the upper limit value, which is retrieved from a database outside the forklift, and
the database stores a plurality of lift height ranges each having a different numerical range, and one of the lift height ranges is selected based on the unloading place and retrieved by the forklift to be used in abnormality determination.

2. The control method according to claim 1 , wherein:
the lift height range is a range in which the fork is estimated to be positioned when the unloading place is a ground or an object that is not transportable by the forklift and the transport pallet is successfully placed onto the ground or the object; and
the lift height range is a range in which the fork is estimated to be positioned when the unloading place is an unload pallet and the transport pallet is successfully placed onto the unload pallet, the unload pallet being a transport pallet on which the transport pallet is to be stacked.

3. The control method according to claim 1 , further comprising, when determination is made during the lowering operation that the abnormality is present, resuming the lowering operation at an initial position by returning to the initial position that is a position where the lowering operation is started.

4. The control method according to claim 3 , further comprising, stopping control for the unloading onto the unloading place when a number of determination times that the abnormality is present during the lowering operation reaches a predetermined value.

5. The control method according to claim 1 , further comprising, resuming at a predetermined position an operation of moving the forklift to a position where the lowering operation is to be performed by returning the forklift to the predetermined position when determination is made that the abnormality is present during the lowering operation.

6. The control method according to claim 1 , wherein:
the lift height range is a range that is to be used for determination that the abnormality is present; and
the lift height range is calculated based on a type of the transport pallet and is set by adding a variation value among a plurality of the transport pallets.

7. The control method according to claim 1 , wherein the forklift is an unmanned forklift.

8. The control method according to claim 1 , further comprising:
acquiring first information at a position where the transport pallet is to be placed onto the fork, the first information being information on the transport pallet;
performing a checking process of checking the acquired first information against second information, the second information being information on the transport pallet corresponding to the acquired load information and the acquired lift height range information; and
performing the lowering operation when the checking process is successful.

9. A control device configured to control a forklift to unload a transport pallet onto an unloading place, the forklift including a load sensor configured to detect load of an item placed on a fork, and a lift height sensor configured to detect a lift height of the fork, the control device comprising:
a processor configured to:
control at least one of movement of the forklift and horizontal movement of the fork;
control raising and lowering of the fork;
acquire load information of the transport pallet placed on the fork and lift height range information, the lift height range information indicating a lift height range, the lift height range being a range of height in which the fork is estimated to be positioned when unloading onto the unloading place is successful, the lift height range being determined based at least on a height of the unloading place; and
determine whether an abnormality is present, wherein
the processor is configured to perform a lowering operation based on the load information and the lift height range information that are acquired, the lowering operation being an operation of lowering the fork with the transport pallet from above the unloading place,
the processor is configured to perform an operation of pulling out the fork when a load value detected by the load sensor is equal to or less than a predetermined value and a lift height value detected by the lift height sensor is within the lift height range,
the processor is configured to determine that an abnormality is present when one of a first condition and a second condition is satisfied during the lowering operation,
the first condition is a determination by the processor that the lift height value is equal to or less than a lower limit value of the lift height range,
the second condition is a determination by the processor that the load value is equal to or less than the predetermined value and the lift height value is equal to or larger than an upper limit value of the lift height range,
the lift height value is a numerical height value detected by the lift height sensor on the forklift, and the lift height range is a range of numerical values starting from the lower limit value to the upper limit value, which is retrieved from a database outside the forklift, and
the database stores a plurality of lift height ranges each having a different numerical range, and one of the lift height ranges is selected based on the unloading place and retrieved by the forklift to be used in abnormality determination.

10. A control system configured to control a forklift to unload a transport pallet onto an unloading place, the control system comprising a control device configured to:
control at least one of movement of the forklift and horizontal movement of a fork, the forklift including a load sensor configured to detect load of an item placed on the fork, and a lift height sensor configured to detect a lift height of the fork;
control raising and lowering of the fork;
acquir

Assignees

• Toyota Motor Co Ltd
• Shinmei Ind Co Ltd
• Toyota Jidoshokki Kk

Inventors

• Shigemasa Takumi
• Asami Daisuke
• Sato Yoshiaki
• Oshima Yutaka
• Mita Tatsuya

Classifications

• B66F9/063

  Automatically guided · CPC title

• B66F9/24

  Electrical devices or systems · CPC title

• B66F9/06

  movable, with their loads, on wheels or the like, e.g. fork-lift trucks (vehicle aspects B60 - B62; vehicles predominantly for transporting loads and modified to facilitate loading or unloading B60P1/00; low-lift hand trucks for transporting goods B62B3/06) · CPC title

• B66F9/07504

  Accessories, e.g. for towing, charging, locking · CPC title

• B66F9/0755 Primary

  Position control; Position detectors · CPC title