Forklift and forklift control method

Abstract

To provide a forklift capable of handling cargo while taking into account the tilt of the loading platform. [Solution] The forklift according to the present disclosure is a forklift that performs loading and unloading of an object onto the loading platform of a vehicle, and includes forks that are inserted into insertion holes provided in the object, a calculation unit that calculates the inclination of the loading platform, and a tilt control unit that controls the inclination of the forks according to the calculated inclination of the loading platform. It further includes an illumination unit that irradiates a reference light from the side of the loading platform toward the mounting surface of the loading platform, and an observation unit that observes the reference light irradiated onto the loading platform, and the calculation unit determines the inclination of the loading platform based on the observed reference light.

Description

Technical Field

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[0001] The present disclosure relates to a forklift and a method for controlling a forklift.

Background Art

[0002] Patent Document 1 discloses a cargo handling system capable of taking a load from a cargo bed with an unmanned forklift even when the ground height of the cargo bed of a truck changes. The cargo handling system described in Patent Document 1 includes a truck having a cargo bed on which a load is stacked and an unmanned forklift for taking the load. The truck includes an information transmission unit that transmits ground height information related to the ground height of the cargo bed. The unmanned forklift controls the raising and lowering of the forks based on the ground height information when taking a load with the forks.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] [[ID=3s4]] In the cargo handling system of Patent Document 1, the ground height information of the cargo bed is estimated on the truck side based on load data indicating the load applied to the cargo bed (the loading amount of the load stacked on the cargo bed) and a ground height estimation model, and is transmitted to the unmanned forklift side.

[0005] However, in Patent Document 1, only the height information of the cargo bed is provided from the truck side to the unmanned forklift, and the inclination of the cargo bed caused by the progress of the cargo handling is not considered. When the cargo bed is inclined, the forklift may not be able to insert the forks into the insertion holes of the pallet, and there is a risk that the cargo handling cannot be performed.

[0006] This disclosure was made in view of the above problems and aims to provide a forklift capable of handling cargo while taking into account the tilt of the loading platform. [Means for solving the problem]

[0007] The forklift relating to this disclosure is a forklift that performs loading and unloading of an object onto the loading platform of a vehicle, and includes forks that are inserted into insertion holes provided in the object, a calculation unit that calculates the inclination of the loading platform, and a tilt control unit that controls the inclination of the forks according to the calculated inclination of the loading platform.

[0008] The forklift control method according to this disclosure is a forklift control method for loading and unloading an object onto the loading platform of a vehicle, and includes the steps of: calculating the inclination of the loading platform; and controlling the inclination of the forks inserted into insertion holes provided in the object according to the calculated inclination of the loading platform. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide a forklift capable of performing cargo handling while taking into account the inclination of the loading platform. [Brief explanation of the drawing]

[0010] [Figure 1] This is a diagram showing the configuration of a forklift according to Embodiment 1. [Figure 2] This block diagram shows an example of the configuration of the control device shown in Figure 1. [Figure 3] This diagram illustrates the tilt of the truck bed and the region where the reference light is placed on the mounting surface. [Figure 4] This diagram illustrates the tilt of the truck bed and the region where the reference light is placed on the mounting surface. [Figure 5] This diagram illustrates the tilt of the truck bed and the region where the reference light is placed on the mounting surface. [Figure 6] This diagram shows the configuration of the forklift according to Embodiment 2. [Modes for carrying out the invention]

[0011] Embodiments of this disclosure will be described below with reference to the drawings. For clarity of explanation, the following descriptions and drawings have been omitted and simplified as appropriate. In addition, the same elements are denoted by the same reference numerals in each drawing, and redundant explanations have been omitted where necessary.

[0012] The embodiment relates to an unmanned forklift having the function of loading and unloading cargo onto the cargo bed of a freight vehicle such as a truck.

[0013] Embodiment 1. Figure 1 is a diagram showing the configuration of a forklift 10 according to Embodiment 1. Figure 1 shows a view of the forklift 10 from the left side and a view of the truck 30 from the rear. The truck 30 is positioned in front of the forklift 10. The truck 30 is a vehicle that transports objects 40 on which cargo 42 is loaded onto cargo materials 41 such as pallets or skids.

[0014] The forklift 10 performs cargo handling operations, including unloading objects 40 from a truck 30 and loading objects 40 onto a truck 30, for example, in a workplace such as a factory or commercial facility. The cargo material 41 has a storage section for accommodating the cargo 42 and insertion holes (neither shown) provided below the storage section into which the forks 15 of the forklift 10, which will be described later, are inserted.

[0015] Truck 30 comprises a cargo bed 31, tires 32, and side walls 33. The cargo bed 31 is loaded with the object 40. The surface of the cargo bed 31 on which the object 40 is loaded is designated as the loading surface 34. The tires 32 support the load applied to the cargo bed 31. The side walls 33 constitute a cargo compartment 35 that houses the object 40. By flipping up the side walls 33, the side of the cargo compartment 35 is opened. With the cargo compartment 35 open, the forklift 10 can load and unload the object 40 inside the cargo compartment 35 from the side of the truck 30.

[0016] Since the tire 32 is deformed according to the weight of the object 40 loaded on the loading platform 31, the ground height of the loading platform 31 (i.e., the distance from the ground surface to the placement surface 34) changes. Also, when the object 40 is placed on the loading platform 31, the suspension of the truck 30 sinks. Therefore, depending on the placement position of the object 40 on the loading platform 31, there may be a tilt of the loading platform 31 with respect to the forklift 10 in the front-rear direction. Hereinafter, a state where the back side is lowered and the front side is raised when viewed from the forklift 10 side of the loading platform 31 is referred to as a "front-lowered state", and a state where the back side is raised and the front side is lowered is referred to as a "front-raised state".

[0017] The forklift 10 includes a vehicle body 11 and a cargo handling device 12. The cargo handling device 12 includes a mast 13, a lift bracket 14, and forks 15. The mast 13 is configured, for example, by an outer mast (not shown) and an inner mast being slidably engaged with each other. The lift bracket 14 is connected to the inner mast of the mast 13, for example. The lift bracket 14 is provided so as to be able to move up and down with respect to the inner mast.

[0018] The forks 15 are attached to the lift bracket 14. The forks 15 extend toward the front of the forklift 10. The forks 15 are the portions that are inserted into the insertion holes provided in the object 40.

[0019] Also, the forklift 10 includes a lift cylinder and a tilt cylinder (not shown). The lift cylinder is a fork lifting mechanism for lifting and lowering the forks 15 and is, for example, a hydraulic cylinder. By supplying and discharging hydraulic oil to the lift cylinder, the forks 15 move up and down together with the lift bracket 14. The tilt cylinder is a fork tilting mechanism for tilting the forks 15 in the front-rear direction and is, for example, a hydraulic cylinder. The forks 15 are tilted by supplying and discharging hydraulic oil to the tilt cylinder.

[0020] Note that the forklift 10 includes a drive mechanism and a hydraulic mechanism not shown in the figure. The drive mechanism is a member for driving the forklift 10. For example, in the case of a forklift in which drive wheels are driven by a travel motor, the drive mechanism may include a travel motor, a motor driver, a steering device, and the like.

[0021] The hydraulic mechanism is a member for controlling the supply and discharge of hydraulic oil to the lift cylinder and the tilt cylinder. The hydraulic mechanism includes a cargo handling motor for driving a pump that discharges hydraulic oil, a control valve for distributing the hydraulic oil, and the like. The control device 1 operates the cargo handling device 12 by controlling the hydraulic mechanism. The forklift 10 is an unmanned forklift that automatically operates under the control of the control device 1. [[ID=??]]

[0022] The forklift 10 further includes an irradiation device 16 and an imaging device 17. The irradiation device 16 irradiates reference light from the side of the load platform 31 toward the placement surface 34 of the load platform 31. The irradiation device 16 is fixed to, for example, the mast 13. The imaging device 17 is an observation unit that observes the reference light irradiated on the load platform 31. In Embodiment 1, the imaging device 17 may be a camera that captures an area on the placement surface 34 of the load platform 31 where the reference light hits. The imaging device 17 is provided, for example, at the upper part of the mast 13. The imaging device 17 can output an image of the captured placement surface 34 to the control device 1.

[0023] The forklift 10 includes a control device 1 that controls the operations of each part. FIG. 2 is a block diagram showing the configuration of the control device 1 of the forklift 10 according to Embodiment 1. The control device 1 includes a storage unit 2 and a processing unit 3. The storage unit 2 is an example of a storage device including a non-volatile memory such as a flash memory or an SSD (Solid State Drive). In the storage unit 2, a program for causing a computer to execute each process of the control method of the forklift 10 according to Embodiment 1 is stored.

[0024] The processing unit 3 is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or a DSP (Digital Signal Processor). The processing unit 3 loads a program into memory such as RAM (Random Access Memory), which is not shown in the diagram, and executes it. In this way, the processing unit 3 realizes the functions of the calculation unit 4 and the tilt control unit 5.

[0025] Furthermore, each component of the control device 1 may be implemented using hardware circuits such as ASICs (Application Specific Integrated Circuits) or FPGAs (Field Programmable Gate Arrays). Also, some or all of the components of each device may be implemented using general-purpose or dedicated circuits, processors, etc., or combinations thereof. These may be configured as a single chip or as multiple chips connected via a bus. Some or all of the components of each device may also be implemented using combinations of the aforementioned circuits, etc., and programs.

[0026] The calculation unit 4 calculates the inclination of the truck bed 31 of the truck 30. Here, the calculation unit 4 calculates the inclination of the truck bed based on the observed reference light. Specifically, the calculation unit 4 acquires an image of the mounting surface 34 input from the imaging device 17. Then, the calculation unit 4 performs known image processing to calculate the length of the area on the mounting surface 34 that is illuminated by the reference light along the direction of illumination. The calculation unit 4 can determine the inclination of the truck bed 31 according to this length. The tilt control unit 5 controls the tilt of the forks 15 according to the calculated inclination angle of the truck bed 31.

[0027] Here, with reference to Figures 3, 4, and 5, the inclination of the truck bed and the region corresponding to the mounting surface of the reference light will be explained. The region on the mounting surface 34 that is illuminated by the reference light is defined as the illumination region LT. In Figures 3 to 5, the illumination region LT is shown above the truck bed 31 when the mounting surface 34 is viewed from above. The inclination angle of the truck bed 31 is assumed to be the angle between the horizontal plane and the mounting surface 34 when the truck bed 31 is viewed from the rear.

[0028] As shown in Figure 3, when the mounting surface 34 is horizontal, i.e., when the inclination angle of the loading platform 31 is 0°, the reference light emitted from the illumination device 16 hits the entire width of the mounting surface 34. In this case, the length L1 of the illumination area LT along the direction of illumination of the reference light is equal to the width of the mounting surface 34. The calculation unit 4 can determine the inclination angle of the loading platform 31 according to the length L1.

[0029] The tilt control unit 5 can control the tilt of the forks 15 according to the calculated tilt angle of the loading platform 31. When the tilt angle of the loading platform 31 is 0°, the insertion holes of the object 40 placed on the mounting surface 34 extend horizontally. In this case, the tilt control unit 5 can control the tilt of the forks 15 so that the forks 15 inserted into the insertion holes are horizontal.

[0030] As shown in Figure 4, when the loading platform 31 is tilted upwards at the front, the reference light emitted from the illumination device 16 hits a portion of the mounting surface 34 in the width direction. In this case, the length L2 of the illumination area LT along the direction of illumination of the reference light is shorter than the length L1 when the loading platform 31 is horizontal. The calculation unit 4 can determine the inclination angle of the loading platform 31 according to the length L2. The tilt control unit 5 can control the tilt of the forks 15 according to the calculated inclination angle of the loading platform 31.

[0031] As shown in Figure 5, when the loading platform 31 is tilted downwards at the front, the reference light emitted from the illumination device 16 does not illuminate the mounting surface 34. In this case, the calculation unit 4 can output information to the tilt control unit 5 indicating that the reference light is not illuminating the mounting surface 34. When the loading platform 31 is tilted downwards at the front, the forks 15 cannot pick up the object 40. In this case, the tilt control unit 5 may notify the worker, for example, by sound or light, that it is impossible to load or unload the object 40 with the forklift 10.

[0032] Thus, according to this embodiment, the tilt of the forks 15 can be controlled according to the tilt angle of the loading platform 31 using a simple system consisting of an inexpensive illumination device 16 and an imaging device 17. This makes it possible to achieve unmanned loading and unloading by the forklift 10, taking into account the tilt of the loading platform.

[0033] Next, we will explain how to control the forklift. Here, we will describe an example where the forklift 10 performs unloading work when the loading platform 31 of the truck 30 is raised at the front, as viewed from the forklift 10.

[0034] First, the illumination device 16 shines a reference light from the side of the loading platform 31 toward the mounting surface 34. Then, the imaging device 17 observes the reference light shining on the loading platform 31. Specifically, the imaging device 17 photographs the illumination area LT on the mounting surface 34 of the loading platform 31 that is illuminated by the reference light. The imaging device 17 transmits the captured image to the control device 1.

[0035] The control device 1 determines the length of the area on the mounting surface 34 illuminated by the reference light along the direction of illumination from the received image, and calculates the inclination of the loading platform 31 according to that length. Then, the control device 1 controls the inclination of the forks 15 that are inserted into the insertion holes provided in the object 40 according to the calculated inclination of the loading platform 31. This makes it possible to tilt the forks 15 to match the inclination of the insertion holes in the object 40 placed on the mounting surface 34.

[0036] Subsequently, by moving the forklift 10 forward towards the truck 30, the forks 15 can be smoothly inserted into the insertion holes of the object 40, making it possible to unload the object 40 from the truck 30.

[0037] When the forklift 10 performs loading operations, the loading control is performed when the object 40 is loaded onto the forks 15. The state in which the object 40 is loaded onto the forks 15 means that the forks 15 are inserted into the insertion holes of the object 40 and the object 40 is supported by the forks 15. As described above, the control device 1 determines the length along the direction of illumination of the area on the loading surface 34 of the loading platform 31 that is illuminated by the reference light, and calculates the inclination of the loading platform 31 according to that length. The forklift 10 can load the object 40 onto the truck 30 while controlling the inclination angle of the forks 15 according to the inclination of the loading platform 31.

[0038] Furthermore, if the reference light spreads vertically, even if the inclination of the loading platform 31 changes, the reference light will hit the entire width of the loading platform 31, and there will be no change in the length of the area hit by the reference light along the direction of illumination, which may prevent accurate calculation of the inclination of the loading platform 31. For this reason, it is preferable that the reference light emitted from the illumination device 16 has a small vertical spread.

[0039] The reference light emitted from the illumination device 16 can be, for example, a spot light or a slit light extending horizontally. The illumination device 16 can convert diffused light emitted from a light source such as an LED into a spot light by passing it through an aperture. The illumination device 16 can also convert diffused light into slit light by passing it through an optical slit. By reducing the vertical spread of the reference light, the length of the illumination area LT along the illumination direction can be changed according to the inclination of the cargo bed 31, making it possible to accurately calculate the inclination of the cargo bed 31.

[0040] Embodiment 2. Figure 6 shows the configuration of the forklift 10A according to Embodiment 2. Figure 2 shows a view of the forklift 10 from the left side and a view of the truck 30 from the rear. The truck 30 is positioned in front of the forklift 10. As shown in Figure 6, the side 11A of the forklift 10A's body 11 facing the truck 30 is opposite the side 36 of the cargo bed 31. The side 11A and the side 36 are approximately parallel in the vertical direction (direction of gravity). In Figure 6, the same reference numerals are used for components that are the same as those in Figure 1, and their descriptions are omitted.

[0041] The forklift 10A has a first distance measuring unit 18A and a second distance measuring unit 18B instead of the illumination device 16 and imaging device 17 of Embodiment 1. The first distance measuring unit 18A and the second distance measuring unit 18B are sensors capable of measuring the distance between the forklift 10 and the truck 30. The first distance measuring unit 18A and the second distance measuring unit 18B may be, for example, a millimeter-wave radar, a laser sensor, or LiDAR (Laser Imaging Detection and Ranging).

[0042] The first distance measuring unit 18A measures a first distance from the reference position to the upper part of the side surface 36 of the loading platform 31. The second distance measuring unit 18B measures a second distance from the reference position to the lower part of the side surface 36 of the loading platform 31. The "reference position" can be any position on the forklift 10. In the example shown in Figure 6, the "reference position" is the position of the first distance measuring unit 18A and the second distance measuring unit 18B, which are provided on the surface 11A of the vehicle body 11 facing the side surface 36. The "upper part" and "lower part" of the side surface 36 of the loading platform 31 refer, for example, to the upper and lower parts of the side surface 36 on a predetermined vertical line.

[0043] In Embodiment 2, the calculation unit 4 can determine the inclination of the loading platform 31 using the first distance and the second distance. When the loading platform 31 is tilted upwards at the front, the first distance becomes shorter than the second distance. The calculation unit 4 can calculate the inclination of the loading platform 31 based on the difference between the first distance and the second distance. The tilt control unit 5 can control the tilt angle of the forks 15 according to the calculated inclination. When the inclination of the loading platform 31 and the tilt angle of the forks 15 become equal, the distances measured by the first distance measuring unit 18A and the second distance measuring unit 18B become equal. That is, in Embodiment 2, the forklift 10 tilts the forks 15 so that the first distance measured by the first distance measuring unit 18A and the second distance measured by the second distance measuring unit 18B become equal.

[0044] Next, we will explain how to control the forklift. Here, we will describe an example where the forklift 10 performs unloading work when the loading platform 31 of the truck 30 is raised at the front, as viewed from the forklift 10.

[0045] First, the first distance measuring unit 18A measures a first distance from the reference position to the top of the side surface 36 of the loading platform 31. The second distance measuring unit 18B measures a second distance from the reference position to the bottom of the side surface 36 of the loading platform 31. The control device 1 can then tilt the forks 15 so that the first distance and the second distance are equal. After that, by moving the forklift 10 forward in the direction of the truck 30, the forks 15 can be smoothly inserted into the insertion holes of the object 40, and the object 40 can be unloaded from the truck 30.

[0046] When the forklift 10 performs loading operations, the loading control is performed with the object 40 loaded onto the forks 15. As described above, the control device 1 calculates the inclination of the loading platform 31 using the first distance and second distance measured by the first distance measuring unit 18A and the second distance measuring unit 18B, respectively. The forklift 10 can load the object 40 onto the truck 30 while controlling the inclination angle of the forks 15 in accordance with the inclination of the loading platform 31.

[0047] As described above, according to the embodiment, the forklift 10 can automatically perform cargo handling operations, taking into account the tilt of the cargo bed 31 that occurs as the cargo handling progresses.

[0048] In the examples described above, the program includes a set of instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more of the functions described in the embodiments. The program may be stored on a non-temporary computer-readable medium or a physical storage medium. Examples, but not limited to, include RAM, read-only memory (ROM), flash memory, SSD or other memory technologies, CD-ROM, digital versatile disc (DVD), Blu-ray® disc or other optical disc storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage devices. The program may be transmitted over a temporary computer-readable medium or a communication medium. Examples, but not limited to, include, a temporary computer-readable medium or a communication medium that includes an electrical, optical, acoustic or other form of propagating signal.

[0049] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure can be made as can be understood by those skilled in the art within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0050] Each drawing is merely illustrative to illustrate one or more embodiments. Each drawing may be associated with one or more other embodiments rather than with only one specific embodiment. As those skilled in the art will understand, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings, for example, to create embodiments not explicitly shown or described. Not all features or steps shown in any one drawing to illustrate an exemplary embodiment are necessarily required, and some features or steps may be omitted. The order of steps shown in any of the drawings may be changed as appropriate.

[0051] This disclosure is not limited to the embodiments described above, and may be modified as appropriate without departing from the spirit of the invention. [Explanation of symbols]

[0052] 1 Control device 2 Storage section 3 Processing Unit 4. Calculation Unit 5. Tilt control unit 10 Forklifts 11 Car body 12. Cargo handling equipment 13 Mast 14 Lift Bracket 15 Forks 16 Irradiation device 17 Imaging device 18 Tilt Sensor 18A 1st ranging section 18B 2nd ranging section 30 tracks 31 Cargo bed 32 tires 33 Side wall 34 Mounting surface 35 Cargo area 36 Side view 40 Objects 41 Packing materials 42 loads LT irradiation area

Claims

1. A forklift used for loading and unloading objects onto the loading platform of a vehicle, A fork inserted into an insertion hole provided in the object, A calculation unit for calculating the inclination of the cargo bed, A tilt control unit controls the tilt of the forks according to the calculated tilt of the cargo bed, including, forklift.

2. An illumination unit that irradiates a reference light from the side of the cargo bed toward the mounting surface of the cargo bed, An observation unit for observing the reference light irradiated onto the cargo bed, It further includes, The calculation unit determines the inclination of the cargo bed based on the observed reference light. The forklift according to claim 1.

3. The observation unit observes the length of the region on the loading surface of the cargo bed that is illuminated by the reference light, along the direction of illumination. The calculation unit determines the inclination of the cargo bed according to the length. The forklift according to claim 2.

4. A first distance measuring unit that measures a first distance from a reference position to the upper part of the side of the cargo bed, A second distance measuring unit measures a second distance from the aforementioned reference position to the lower part of the side of the cargo bed, It further includes, The calculation unit uses the first distance and the second distance to determine the inclination of the cargo bed. The forklift according to claim 1.

5. A control method for a forklift that performs loading and unloading of objects onto the loading platform of a vehicle, The steps include calculating the inclination of the cargo bed, A step of controlling the inclination of the forks inserted into the insertion holes provided in the object, according to the calculated inclination of the cargo bed, including, Forklift control methods.

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