Industrial truck with a lifting height assistance system

Abstract

A forklift truck with a lifting height assistance system that supports a storage or retrieval operation, with a camera (5) in the area of ​​a height-adjustable load carrier (4) directed towards an area in front of the load carrier, and with a control unit (15) that optically recognizes a target position for the load carrier (4) from a temporal sequence of images recorded by the camera (5) and is configured to optically monitor the approach to the target position, wherein during a storage or retrieval operation an upper edge of the shelf support in the target position is recognized and the control unit is configured to stop a lifting movement in response to a predetermined additional lifting height above the upper edge.

Description

[0001] The present invention relates to a forklift truck with a lifting height assistance system.

[0002] In many areas of logistics, particularly intralogistics, industrial trucks are used. In the transport of general cargo, load carriers such as pallets and wire mesh containers are frequently employed to group individual, small items into loading units. These units can then be transported, loaded, and stacked efficiently and economically using industrial trucks. The assembled loading units are picked up and moved by load carriers or fork arms on the industrial trucks. In racking systems, stacking heights reach 10 to 13 meters, with the operator remaining close to the ground on the industrial truck. At such a distance, and with the typically unfavorable viewing angle, potentially poor lighting, and other visual obstructions, performing a stacking or unstacking operation is very difficult and therefore also unsafe and dangerous.Furthermore, the required clearance above the loaded storage units in the racks is kept as small as possible for storage and retrieval to increase warehouse efficiency. Operating these industrial trucks therefore requires considerable experience to carry out these operations quickly, safely, and effectively.

[0003] To improve the described situation regarding stacking and unstacking at great heights, systems have been developed in the past to facilitate the stacking and unstacking of load units at significant lifting heights. One known system is a so-called lift height preselection, which requires a measuring device to determine the current lifting height. Furthermore, all heights at which stacking or unstacking is to take place must be communicated to the system via input or a "teach-in" function. On the associated display and control unit, the target height and the desired function—stacking or unstacking—must be selected before the lifting process begins. The system automatically stops the lifting process when the desired target height is reached.

[0004] In a further development of the described system, the preselection of the target height is eliminated. Instead, the system is signaled that the next known storage and retrieval height is the target height by reducing the setpoint for the lifting speed. A disadvantage of the described system is the requirement for a height measuring device and the input of all possible lifting heights for storage and retrieval.

[0005] Furthermore, camera-monitor systems are known in the prior art in which a camera is integrated into the tip of the load-bearing device and / or positioned laterally next to the fork tine or in the load carriage near the back of the fork. The camera image is displayed to the driver on a monitor, allowing them to determine the position of the load-bearing devices in relation to the rack support or the entry openings of the load units to be retrieved. A disadvantage of this system is that the driver must interpret the camera image and, due to the unfamiliar hand-eye coordination required when the camera is moving, must position the load-bearing devices.

[0006] From DE 10 2008 027 695 A1, a method for controlling storage positions in industrial trucks with at least one sensor for detecting the environment in front of a load-handling attachment is known. When the known industrial truck is in front of or approaching a selected storage position, the control device determines the storage position from sensor data. In a second step, the control device assumes a target position of the load-handling attachment for approaching this storage position, and in a third step, the control device corrects the actual position of the load-handling attachment until it matches the target position. In the known method, it is also necessary that storage positions be preselected.

[0007] From EP 2 439 165 A1, a forklift truck with a height-adjustable load-bearing device, a lifting height control for the load-bearing device in which several predetermined lifting heights for the load-bearing device are stored, and a lifting height detection system for the load-bearing device became known. With a control element that allows manual adjustment of the lifting height of the load-bearing device at different speeds, reducing the speed for adjusting the load-bearing device displays a target lifting height corresponding to a predetermined lifting height.

[0008] From DE 10 2010 055 774 A1, a forklift truck with a lifting mast is known, on which a load-bearing device with two forks is guided in a height-adjustable manner. A sensor arranged on the load-bearing device is provided for detecting the spatial environment. An evaluation unit is designed to determine a storage position from the data acquired by the sensor to support a storage process, wherein the sensor is a time-of-flight camera system with a light source. A time-of-flight camera system has a light source and a light sensor that emits pulsed light which is reflected by the objects in the field of view. Differences in the time of flight of the light are evaluated so that, in the case of a matrix-shaped sensor, a value for the distance of the object is generated for each point of light.

[0009] From EP 1 408 001 A1, a forklift truck is known in which a display is provided that shows position information to assist in steering to the desired loading position. Markers are provided to locate the steering position.

[0010] German patent DE 20 2007 005 697 U1 discloses a device that assists forklift drivers in handling loads. This device includes sensors for measuring quantities related to load handling and limit setting devices for setting limit values. A comparator compares the measured quantity with the limit value and calculates a difference that can be continuously displayed graphically.

[0011] A control method for setting down a load with a forklift truck is disclosed in DE 10 2012 108 028 A1. The forklift truck has a camera focused on the area of ​​a load-handling attachment, a monitor, and a control device. The position of the load relative to its storage position is detected and displayed on a monitor. After release by means of a confirmation input, the forklift truck is automatically adjusted and aligned, with any functions of the forklift truck that cannot be automatically controlled being displayed accordingly on a screen.

[0012] The invention is based on the objective of equipping a forklift truck with a lifting height assistance system that supports a driver during storage and retrieval operations at high storage heights using the simplest possible means and in a flexible manner.

[0013] According to the invention, the problem is solved by a forklift truck with the features of claim 1. Advantageous embodiments are the subject matter of the dependent claims.

[0014] The industrial truck according to the invention has a lifting height assistance system that supports storage and retrieval operations. The lifting height assistance system includes a camera in the area of ​​the load-bearing tip, which uses a sequence of images to determine a target position for the load-bearing elements. Responding to a reduction in the setpoint for the lifting speed, the system further reduces the speed when the load-bearing elements are near the target position. With the lifting height assistance system according to the invention, it is not necessary for lifting heights to be predefined. Instead, lifting heights are optically detected, and the operator is assisted in controlling them. The desired lifting height is selected by the operator reducing the lifting speed when near the target position. The control unit then uses the sequence of images to determine the desired lifting height.The camera can then be used to visually monitor the precise approach to the target position. Unlike a technically complex time-of-flight camera, a conventional optical camera can be used. Preferably, the optical camera and the evaluation of its images can be activated in response to a reduction in the lifting speed. In the lifting height assistance system according to the invention, a sequence of images is captured and evaluated by the camera, thus monitoring the approach to the target position.

[0015] The intention here is to reduce the lifting speed in order to enable precise approach to the target position, whether automatically or manually.

[0016] In the industrial truck according to the invention, during a storage or retrieval operation, the upper edge of a shelf support is detected in the target position, and the lifting movement is stopped when a predetermined additional lifting height above the upper edge is reached. The predetermined additional lifting height preferably depends on whether a storage or retrieval operation is taking place. In a storage operation, the predetermined additional lifting height is a value that allows collision-free entry into the receiving openings of the load unit. The load unit can, for example, consist of a pallet with receiving openings for the load-bearing elements or another load carrier. Generally, the terminology used to define the storage location height above the floor is the height of the upper edge of the storage location support, which serves as a load support for a load unit in the storage location.When determining the additional lifting height, the height of the load-bearing devices must also be taken into account, since the underside of the load-bearing devices must be positioned above the top edge of the storage platform support.

[0017] For a storage operation, a predetermined additional lift height is stored to allow collision-free entry into the storage location. Due to potential vibrations and movements of the raised load unit, a different additional lift height is required for collision-free entry than for retrieval. The required additional lift height is determined based on the amplitude of the potential vibrations and the length and height dimensions of the load-handling device.

[0018] In a preferred embodiment, the images recorded by the camera can also be evaluated during an insertion process in order to correct the insertion speed into the loading unit being received. Correcting the insertion speed can also include adjusting a manually set insertion speed, for example, by slowing it down as the forks increasingly approach the loading unit. Alternatively, it is also possible to control the desired insertion depth via the preset insertion speed until the load-bearing device is fully inserted.

[0019] In a preferred further development, an optical and / or acoustic signal is triggered when the detected lifting height has been reached and the storage or retrieval process can be carried out.

[0020] Advantageously, a lowering process can be automatically stopped when the loading unit is detached. This is achieved by optical or other sensing whether the load-bearing device is free from the loading unit. It can also be detected whether a load has been placed on the load-bearing device.

[0021] In a further preferred embodiment, a load sensor is provided that reports a detected load on the load-bearing device to the control unit, whereby the control unit only performs a storage or unloading operation when a load is detected. If a load is detected during lifting, a storage operation takes place. If, on the other hand, no load is detected, a storage operation occurs. The load sensor can also be used to determine whether the load-bearing device is released from the loading unit or whether a load has been picked up.

[0022] In another preferred embodiment, the control unit, responding to a first reduced and then later increased lifting speed, deletes the detected target position in order to detect a new target position when the target value for the lifting speed is reduced again. By simply deleting a previously detected target position, the operator is given the opportunity to quickly abandon an erroneously selected target position and thus abort any approach to the detected target position that may have already begun.

[0023] In a preferred embodiment, once the target position has been detected, the control unit takes over the entire process of moving to it. In this embodiment, the operator initially has no direct influence on the lifting height or the speed at which the lifting height is adjusted. In an alternative embodiment, the control unit can reduce the speed when adjusting the lifting height, thus giving the operator more time to more precisely position the device.

[0024] Preferred embodiments of the invention are explained below using a few examples. These show: Fig. 1 a forklift truck with the assistance system according to the invention in a schematic view, Fig. 2 load-bearing devices with integrated camera and light source, Fig. 3 load-bearing devices with camera and light source mounted laterally on a tine, Fig. 4 Load-bearing devices with camera and light source arranged in the load carriage, Fig. 5 a load block diagram for the assistance system according to the invention, Fig. 6 A partial view of a shelf and a lifting frame of a forklift truck at the start of an unloading process, Fig. 7 A partial view of a shelf and the lifting frame of the forklift truck at the end of the positioning process for unstacking, Fig. 8 a partial view of a shelf and the lifting frame of the industrial truck according to the invention at the start of a stacking process and Fig. 9 A partial view of a shelf and the lifting frame of the industrial truck at the end of the positioning process during stacking.

[0025] Fig. 1, Fig. 6 and Fig. 9 are published in this or a similar form, but in a different technical context, in DE 10 2010 055 774 A1, which is part of the state of the art.

[0026] Fig. Figure 1 shows a counterbalance forklift truck equipped with an assistance system for loading and unloading load units. The vehicle consists of a chassis 2 with front and rear axles. A lifting mast 3 with a height-adjustable load carriage 12 is mounted on the chassis 2. A driver's station module 9 is mounted on the chassis 2 and has an operating station 11 for the driver. The control element 8, shown schematically, is used to operate the lifting and lowering functions. Two load carriers 4 are attached to the load carriage 12, at least one of which has a camera 5 near the tip of the load carrier, positioned laterally next to the tip. The camera 5 is electrically connected to an evaluation unit 15 located in the vehicle for power supply and signal exchange.A display and control unit 7 for communication with the driver is attached to the driver's seat module and is also electrically connected to the evaluation unit 15. The camera's beam path is shown in principle by the arrows 10.

[0027] Any inclination of the load-bearing elements 4 can be detected via a sensor 13. A signal indicating a horizontal orientation of the load-bearing elements 4 is displayed to the driver on the display and control unit 7. The position of the sensor for detecting the inclination of the load-bearing elements depends on the design of the lifting frame 3. If the load-bearing elements are arranged to be tiltable relative to the lifting frame, the sensor 13 is preferably arranged on the load carriage 12. In the schematic representation of the sensor 13 on the lifting frame 3, the frame is tiltable relative to the vehicle body 2.

[0028] Fig. Figure 2 shows a top view of the load-bearing elements 4 on the load carriage 12, with other components of the industrial truck omitted for clarity. The camera 5, shown with a dashed line, is positioned centrally at the tip of one of the forks. Since the forks, and especially their tips, are subjected to high mechanical stresses during daily use, it is advantageous to integrate the camera into the fork so that it does not protrude beyond the contour of the fork tip at any point. For this purpose, a corresponding cavity or recess must be provided in this part of the fork so that the camera can be flush-mounted.

[0029] For the camera to function reliably, it is helpful that the object being measured is illuminated by a light source, for example, an infrared light source. A beam path 21 from a light source located, for example, in the immediate vicinity of the camera 5 is shown in the Fig. 2 to 4 are shown schematically.

[0030] In addition to the central arrangement according to Fig. 2 shows Fig. 3. A lateral arrangement is an alternative. In the lateral arrangement, the space between the load-bearing elements is narrowed. However, cable routing 19 can be particularly easy in the interior space between the two load-bearing elements 4.

[0031] Fig. Figure 4 shows a third possible arrangement of the camera 5 in the area of ​​the fork back on a load carriage 12. A deflector 22 is provided laterally on the lower fork tine in the image, which is designed, for example, as a flat profile that leaves a gap between the transporting load unit and the fork tine, through which the camera looks into the space in front of the load fork.

[0032] Fig. Figure 5 shows the main electrical components of the assistance system in a block diagram. The camera 5 is electrically connected to an evaluation unit 15 to perform image analysis. For improved illumination, especially in dimly lit shelves, a light source 6 can be provided, which is also electrically connected to the evaluation unit 15 or alternatively to the camera 5. If the load status of the load-bearing elements 4 cannot be detected by the camera 5, an additional load sensor 14 can be provided, which is also connected to the evaluation unit 15. The connection for signal transmission from the vehicle electronics and control unit 30 is made via a CAN bus connection 33, shown with a dashed line. The operating elements 8, a lifting control 31, and a display and control unit 7 of the vehicle are connected to the same signal circuit, among other things.The signals from the operating elements 8 for lifting and lowering are continuously monitored by the control unit 30, and the lifting control is supplied with target values ​​accordingly. If there is a noticeable reduction in the target speed, the system according to the invention is activated to determine the position of the fork tine 4 relative to a front shelf support.

[0033] Fig. Figure 6 shows a partial side view of a retrieval operation at the moment when the driver noticeably reduces the target lifting speed because he wants to retrieve the loading unit 54. It may be intended that, for example, a differential value is specified by which the lifting speed must be reduced within a predetermined time period. Alternatively or additionally, a minimum lifting speed can also be defined, below which a retrieval or storage operation is detected. Now, camera 5 is activated, and image processing by evaluation unit 15 is activated. Evaluation unit 15 then analyzes a series of sequentially captured images. The shelf support is within the range of the illuminated beam path 10, and the load-bearing elements are lifted at a positioning speed specified by evaluation unit 15.

[0034] In Fig. 7 The assistance system detected the front shelf support 51, and in particular its upper edge, and positioned the load-bearing elements 4 at a height required to allow the loading unit 54 to enter the opening without collision. The lifting process was completed without driver intervention, and this can advantageously be indicated to the driver audibly or visually via the display and control unit 7.

[0035] Fig. Figure 8 shows a partial side view of a storage operation at the moment when the driver noticeably reduces the target lifting speed because he wants to store the loading unit 55. Camera 5 is now activated and the image is evaluated by unit 15. The shelf support is located within the illuminated beam path 10 of the camera, and the load-bearing elements are lifted at a positioning speed specified by evaluation unit 15.

[0036] In Fig. 9 The system has detected the front shelf support 51 and, in particular, its upper edge 52, and positioned the load-bearing elements 4 at the height required to insert the load unit into the shelf without collision. The lifting process was completed without any intervention from the driver, and this can advantageously be additionally indicated to the driver audibly and / or visually by means of the display and control unit 7.

[0037] The assistance system for the lifting height provided in the industrial truck according to the invention has the task of supporting the driver in operating his vehicle during the process of loading and unloading.

[0038] During the unloading process, the operator positions the forklift truck with unloaded load carriers 4 in front of the rack 50. The lifting function is activated via the control element 8, and the empty load carriers are raised. As soon as they are near the height of the rack support 51 containing the load unit 54 to be unloaded, the operator noticeably reduces the lifting speed by appropriately controlling the system. The assistance system according to the invention interprets this as the nearby rack support being the target support. In one possible embodiment of the method, control of the lifting speed is transferred to the assistance system from this point onward. Alternatively, the assistance system can also reduce the lifting speed near the target support to facilitate the unloading process and allow for more precise control via the control element 8.

[0039] Depending on the camera's design and arrangement, a load sensor 14 is also used to check whether the load-bearing elements are unloaded and thus whether a load unit 54 located on the shelf support 51 can be recorded. The shelf support, and in particular its upper edge 52, is detected by evaluating an image sequence from the camera 5. This is achieved using well-known pattern and object recognition methods. Once the upper edge 52 is detected, the load-bearing elements are positioned at a height suitable for inserting them into the designated openings of the load unit 54. The resulting height difference between the upper edge 52, the shelf support 51, and the upper edge of the load-bearing elements 4 is stored in the control unit 15 as a parameterizable value dependent on the shape of the load unit.The required lifting distance is determined by evaluating the individual camera images, specifically the relative movement of the shelf support's upper edge relative to a predefined position in the camera image, such as the center. Once the load-bearing elements 4 have reached the lifting height required to enter the opening of the loading unit 54, the lifting process is stopped. The corresponding command is then transmitted to the vehicle's control unit 15, for example, via CAN bus connection 33. Additionally, the user can receive an audible signal or a notification via the vehicle's display and control unit 7 indicating that the lifting height has been reached and the fork is authorized to enter the opening of the loading unit 54.

[0040] If the target value for the lifting speed is significantly increased by the driver during the positioning process described above, the assistance system according to the invention interprets this as a command to abort the positioning process, since the driver no longer wishes to carry out the relocations at this height.

[0041] The driver then drives the vehicle forward or activates the mast extension function. The load-bearing elements 4 are fully inserted into the openings of the loading unit. Depending on the load sensor design, it detects whether the required insertion depth has been reached. This is indicated audibly by the control unit or visually on the display and control unit 7, and the driver stops the insertion process. A short lifting operation then follows, which the driver initiates by operating the control element 8. The driver then extends the loading unit by retracting the mast and / or reversing and lowers the loaded load-bearing elements to transport height.

[0042] When the camera is positioned to the side of the fork, as for example in Fig. 3 or in the back of the fork according to Fig. 4. Both parts of the load-bearing equipment and the loading unit are within the camera's field of view. Image analysis can then detect whether the loading unit is moving vertically relative to the load-bearing equipment. This allows the system to recognize during the unloading process that the loading unit is moving in the same direction as the load-bearing equipment. If this is the case, the driver receives an audible or visual signal indicating that the load has been lifted far enough to allow for collision-free unloading.

[0043] During the storage process, the operator positions the industrial truck 1, with its load-bearing elements carrying the load unit 54 and at transport height, in front of the rack 50 such that the load-bearing elements only need to be moved slightly laterally once they have been raised to the correct lifting height for storing the load unit. The operator then activates the lifting function using the control element 8, and the loaded load-bearing elements 4 are raised. As soon as they are near the height of the rack support 51, on which the load unit 54 is to be placed, the operator noticeably reduces the lifting speed by appropriately operating the control element 8. The assistance system according to the invention interprets this as indicating that the nearby rack support 51 represents the target support. From this point on, the system according to the invention completely takes over control of the lifting speed.A load sensor 14 is used to check whether the load-bearing elements 4 are loaded and therefore need to be raised to a height that allows the loading unit to be placed on the shelf. By evaluating the sequentially captured images from the camera, the shelf 51, and in particular its upper edge 52, is clearly identified. The load-bearing elements are then positioned at the height required for the loading unit to enter the rack without collision. The resulting height difference between the upper edge of the shelf 51 and the load-bearing elements 4 is stored in the control unit 15 as a parameterizable value that depends on the shape of the loading unit. The required lifting distance is determined by evaluating the individual camera images, using, for example, the relative movement of the upper edge of the shelf to the center of the camera image for this purpose.As soon as the load-bearing devices reach the lifting height required to lower the loading unit, the lifting process is stopped. The corresponding command is transmitted to the vehicle's control unit 15 via CAN bus connection 33. The driver can also be informed visually and audibly that the detected lifting height has been reached and that the load-bearing devices, loaded with the loading unit, are authorized to enter the rack.

[0044] If the target value for the lifting speed is significantly increased by the driver during the positioning process described above, the system according to the invention interprets this as a command to abort the positioning process, since the driver no longer wishes to carry out the storage at this height.

[0045] The driver drives the vehicle forward or activates the mast extension function, and the load-bearing devices loaded with the loading unit are fully immersed in the rack compartment. Once the required immersion depth is reached, a short lowering process follows, which the driver initiates by operating control element 8.

[0046] When the camera is positioned to the side of the load-bearing devices according to Fig. 3 or in the back of the fork according to Fig.Four of the load-bearing elements are within the camera's field of view. Image analysis allows the system to detect whether the load-bearing element is moving vertically relative to the load-bearing elements. During the storage process, the system can identify when the load-bearing element is lowering onto the shelf support while the load-bearing elements continue to descend. If this occurs, the operator receives a visual or audible signal indicating that the unit has been lowered sufficiently. The lowering process can then be automatically stopped. The operator then removes the load-bearing elements from the lowered load-bearing element and thus from the shelf compartment by retracting the mast and / or reversing.

[0047] The assistance system according to the invention has at least one camera in the load-bearing tips, on the side of the load-bearing element, or on the load carriage / fork back, which, together with image data processing, is designed for the detection of shelves or supports. The assistance system according to the invention intervenes in the vehicle control system.

Claims

[1] Industrial truck with a lifting height assistance system that supports a storage or retrieval operation, with a camera (5) in the area of ​​a height-adjustable load carrier (4) directed towards an area in front of the load carrier, and with a control unit (15) that optically recognizes a target position for the load carrier (4) from a temporal sequence of images recorded by the camera (5) and is configured to optically monitor the approach to the target position, wherein during a storage or retrieval operation an upper edge of the shelf support in the target position is recognized and the control unit is configured to stop a lifting movement in response to a predetermined additional lifting height above the upper edge. [2] Industrial truck according to claim 1, characterized by , that during the unloading process the predetermined additional lifting height has a value that allows collision-free entry into the receiving openings of the loading unit (54). [3] Industrial truck according to claim 1 or 2, characterized by , that during the storage process the predetermined additional lift height has a value that allows collision-free entry into a storage location. [4] Industrial truck according to any one of claims 1 to 3, characterized by , that the camera (5) evaluates images during an entry process and corrects an entry speed. [5] Industrial truck according to any one of claims 1 to 4, characterized by , that an optical and / or acoustic signal is triggered when the detected lifting height has been reached. [6] Industrial truck according to any one of claims 1 to 5, characterized by, that a lowering process of the load-bearing device (4) is automatically terminated, in particular when the load-bearing device (4) is released again during a storage process. [7] Industrial truck according to any one of claims 1 to 6, characterized by , that a load sensor is provided which reports a recorded load to the control unit, which only triggers the storage or unloading process when a load is detected. [8] Industrial truck according to any one of claims 1 to 7, characterized by , that the control unit, responding to a lifting speed that is initially reduced and later increased again, deletes the recognized target position in order to recognize a new target position when the target value for the lifting speed is reduced again. [9] Industrial truck according to any one of claims 1 to 8, characterized by , that after the target position is detected, the control unit takes over complete control of the lifting position until the target position has been reached.

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