Determining the position of a conveying unit relative to load carriers

Abstract

The invention relates to a method for determining the spatial position of a conveying unit (1) for conveying load carriers (2) relative to a load carrier (2) under which the conveying unit (1) travels, comprising the following steps: • - acquiring at least one distance of at least one reference point (3A-3D) associated with the conveying unit (1) relative to at least one surface (4A-4C) associated with the load carrier (2); • - acquiring model data which contains an assignment of the at least one acquired distance to a cross-sectional portion (6A-6E) of the load carrier (2); • - determining a spatial position of the conveying unit (1) relative the load carrier (2) on the basis of the at least one acquired distance and the acquired model data. The invention further relates to a conveying unit having at least one sensor (3A-3D) designed to acquire the at least one distance and having a control system connected to the at least one sensor (3A-3D), for controlling the conveying unit (1), wherein the control system is designed to carry out the method according to the invention.

Description

[0001] Applicant: FILICS GmbH Legal file: P102373WO XX

[0002] Determination of the relative position of a conveying unit with respect to load carriers

[0003] The invention relates to a method for determining the spatial position of a conveying unit for transporting load carriers relative to a load carrier under which the conveying unit passes. The invention further relates to a conveying unit controlled according to the method.

[0004] For internal transport of goods, load carriers are regularly used. These can be driven under by forklifts, lifted together with the goods stored on them, and then set down again at the destination after transport. A well-known example of such a load carrier is the standardized and reusable "Euro pallet".

[0005] Various types of industrial trucks, referred to below as conveying devices, are known from the prior art. A distinction can be made between single-unit and multi-unit conveying devices. In the former, as shown, for example, in EP 2 336 075 Al, the sections of the conveying device that pass under the load carrier are rigidly connected to one another. Multi-unit conveying devices, as shown, for example, in DE 10 2007 046 868 Al, usually comprise a first and a second conveying unit that are not physically connected to each other. Conveying devices can also be distinguished by their actuation. On the one hand, manual or motorized actuation is possible, as is the case, for example, with hand pallet trucks, which are regularly used for loading and unloading trucks. On the other hand, autonomously operated conveying devices are also known; see again EP 2 336 075 Al.

[0006] For autonomously operated conveyor systems, it is essential to determine the spatial position of the conveyor. This is typically achieved by markings on the floor surface traversed by the conveyor or on adjacent walls, which can be detected by sensors on the conveyor. Detecting these markings initially reveals the relative position of the sensors, and thus of the conveyor, with respect to the markings. Knowing the absolute position of the markings within a predefined coordinate system, such as that assigned to a warehouse, allows the absolute position of the conveyor within this coordinate system to be calculated.It should be noted at this point that the term “spatial position” can include the spatial location (one, two or even three translational degrees of freedom) and / or the spatial orientation (one, two or even three rotational degrees of freedom).

[0007] For autonomously operated, and moreover, two-part conveyor units that completely pass underneath the load carriers being transported, precise detection of the relative position between the conveyor unit and the load carrier is crucial, especially since neither the conveyor unit itself nor the load carrier can provide a physical stop surface that serves for the exact positioning of the conveyor unit relative to the load carrier. Furthermore, existing approaches to position detection for autonomously operated conveyor systems regularly reach their limits where markings used for position detection can no longer be detected by the conveyor system's sensors, for example, when the conveyor system has moved under a load carrier and the optical line of sight between the sensors and the markings is interrupted.An alternative method of position detection using distance measurement with the aid of sensors that detect the rotation of the wheels of the conveyor system only provides a limited remedy here, since slippage between the wheels and the ground is often unavoidable and inevitably leads to unacceptable deviations in position detection.

[0008] The object of the present invention is to provide a method and a conveying unit which enables reliable detection of the position of a conveying unit relative to a load carrier under which the conveying unit passes.

[0009] This problem is solved by the subject matter of method claim 1 and the subject matter of apparatus claim 9. The dependent claims define preferred embodiments of the present invention. The inventive method for determining the spatial position of a conveying unit for transporting load carriers relative to a load carrier under which the conveying unit passes therefore comprises the following steps:

[0010] - Detecting at least one distance between at least one reference point assigned to the conveying unit and at least one surface assigned to the charge carrier;

[0011] - Acquisition of model data which includes an assignment of at least one recorded distance to a cross-sectional section of the charge carrier;

[0012] - Determine, based on at least one recorded distance and the recorded model data, a spatial position of the conveying unit relative to the load carrier.

[0013] In other words, according to the inventive method, position detection is achieved by one or more distance measurements as the conveying unit passes under the load carrier. The invention takes advantage of the fact that reusable load carriers, in particular, generally have standardized dimensions and geometries, and that one or more suitable distance measurements allow conclusions to be drawn about the final position of the conveying unit relative to the load carrier. Furthermore, the invention is based on the idea that the conveying unit is already sufficiently aligned with the load carrier before it passes under it, so that subsequently only a translational movement of the conveying unit is essentially necessary to completely pass under the load carrier.To determine the relative position between the conveying device and the load carrier, only the position along the single remaining translational degree of freedom in the longitudinal direction of the conveying unit or the load carrier needs to be determined using the position detection system. It should be noted here that position detection is also possible with respect to non-standardized load carriers, provided that geometric data of the load carriers can be accessed.

[0014] In principle, it is conceivable that a single position measurement would suffice for determining the position, for example, if this indicates the start of the conveyor unit's movement under the load carrier. Due to the comparatively short distance traveled until the conveyor unit has completely moved under the load carrier, distance measurement using wheel sensors could be used after the initial position measurement, without having to worry about significant measurement errors, such as those caused by wheel slippage. However, it is equally conceivable that the distance is measured at least at two consecutive times, with continuous position measurement being particularly feasible.

[0015] According to a further embodiment, the spatial position of the conveying unit relative to the load carrier can be determined on the basis of at least one recorded change in position.

[0016] As mentioned above, the spatial position of the conveying unit relative to the load carrier can also be determined based on the distance traveled by the conveying unit since the distance / change in position was detected. Measuring distance is particularly advantageous when the geometry of the load carrier is such that position determination based solely on distance measurements would be too inaccurate. This could be the case, for example, if the load carrier has a constant cross-sectional profile along its length or the direction of travel of the conveying unit, so that distance measurements within this constant cross-sectional profile do not allow for an assignment to a specific position on the load carrier.

[0017] To clarify, it should be mentioned that ideally, a cross-sectional profile that changes across the entire length of the load carrier could allow for a unique assignment of a measured distance to a specific position relative to the load carrier, thus eliminating the need for additional distance measurements. In reality, the familiar "Euro pallet," for example, essentially has five sections, across the length of which the cross-sectional profile of the load carrier does not change significantly. These are, firstly, the three sections defined by the blocks of the load carrier, in which the deck boards rest on the bottom boards via the blocks, and secondly, the two intermediate sections, which are spanned by both the deck boards and the bottom boards.

[0018] According to a further embodiment, the detection of at least one distance is carried out in a direction predefined relative to the conveying unit. In particular, this can be transverse to the longitudinal direction of the conveying unit and / or in a horizontal direction when the conveying unit is in its intended orientation. With regard to a Euro pallet, a single distance detection sensor can determine whether the distance occurs within a cross-sectional section of the Euro pallet in which pallet blocks are arranged, or in an intermediate cross-sectional section spanned by the top and bottom boards.

[0019] In a preferred embodiment, the at least one distance is detected by means of at least one sensor arranged on the conveying unit. In particular, the sensor(s) can define or represent the respective reference points assigned to the conveying unit. In particular, the sensor(s) can be designed for time-of-flight measurement.

[0020] Position determination based solely on position detection becomes more accurate the more sensors are arranged on the conveyor unit for this purpose. This allows for the simultaneous detection of multiple distances using an array of sensors, which are specifically designed for distance measurement in essentially parallel directions and / or arranged primarily along the longitudinal axis of the conveyor unit. By strategically arranging individual sensors, a very precise position determination can be achieved even with a relatively small number of sensors, without the need for additional measures such as the aforementioned distance measurement.

[0021] Another aspect of the present invention relates to a conveying unit for transporting load carriers, comprising an elongated frame structure movable by means of an arrangement of several rollers, a support element which can be raised and lowered in a vertical direction relative to the frame structure by means of a lifting device, at least one sensor designed to detect a distance between a reference point assigned to the conveying unit and a surface assigned to the load carrier, and a control system connected to the at least one sensor for controlling the conveying unit, wherein the control system is designed to carry out a method as described above.

[0022] In particular, the conveying unit according to the invention can have one or more of the following features: the conveying unit forms a conveying device with another, in particular structurally identical, conveying unit, wherein the two conveying units are designed for mutual communication with each other; the at least one sensor is designed to detect the at least one distance in a direction predefined relative to the conveying unit, in particular transverse to the longitudinal direction of the conveying unit and / or in a horizontal direction when the conveying unit is oriented as intended; the at least one sensor is a sensor designed for time-of-flight measurement; the conveying unit comprises an arrangement of several sensors, which are designed in particular for distance measurement in substantially parallel directions and / or are arranged substantially along the longitudinal direction of the conveying unit;The conveying unit comprises at least one sensor designed to detect a distance traveled by the conveying unit, in particular to detect a rotational movement, specifically to detect the number of revolutions of at least one roller of the conveying unit.

[0023] The present invention is described in more detail below with reference to a preferred embodiment and the accompanying figures. The invention can comprise all the features described herein individually or in any meaningful combination. The figures show:

[0024] Figure 1 shows a conveying system comprising two conveying units according to the present

[0025] Invention;

[0026] Figure 2 shows two conveying units according to the invention immediately before entering a load carrier;

[0027] Figure 3 shows two conveying units according to the invention immediately before completely passing under a load carrier.

[0028] Figure 1 shows a two-part conveyor system with two physically unconnected conveyor units 1. Such autonomously operated conveyor systems are known, for example, from DE 10 2007 046 868 Al and DE 10 2019 001 125 Al. Figure 1 further shows how the conveyor units, in their lowered position, can completely pass under a load carrier (transport pallet / “Euro pallet”) in order to subsequently lift the load carrier for transport.

[0029] Figure 2 shows a view from below. The two identical conveyor units 1 are already aligned with respect to the load carrier 2 such that they can each move into a clear space beneath the load carrier 2 with a simple translational movement. For this purpose, each conveyor unit 1 has four rollers 5 arranged in pairs, some or all of which may include a drive mechanism and enable the respective conveyor units 1 to traverse and steer.

[0030] Both conveying units 1 also have several sensors 3 A to 3D, which are designed to perform level measurements in the horizontal direction and perpendicular to the longitudinal axis of the extended conveying units 1, thus detecting their distance to any solid bodies that are located in their respective detection area.

[0031] In the example shown here, the conveyor units 1 have four sensors 3A to 3D on both sides. Of course, any other number and / or arrangement of sensors 3A to 3D is possible within the scope of the present invention.

[0032] The load carrier 2 shown is a so-called "Euro pallet," whose upper deck boards are supported by a total of 9 blocks on 3 bottom boards, which in turn rest on the ground. Of the 9 blocks, those arranged on both longitudinal sides of the load carrier 2 are designated 4A to 4C. Transverse to the longitudinal direction of the load carrier 2, and thus also transverse to the extent of the clear space or the direction of entry of the conveyor units 1, blocks 4A to 4C form a total of three cross-sectional sections 6A, 6C and 6E, with the spaces between them, spanned by the deck boards and the bottom boards of the load carrier 2, forming two cross-sectional sections 6B and 6D.

[0033] During the movement under the load carrier 2, the individual sensors 3A to 3D detect whether any of the blocks 4A to 4C are within their respective detection range. It should be noted here that the terms "position detection" and "distance measurement" used here do not necessarily refer to the recording of a specific numerical value for the distance between a sensor and a detected object, but can also refer simply to the presence of an object within the sensor's detection range. However, a quantitative distance measurement offers the advantage of eliminating potential detection errors. For example, assuming a standardized width for the free space available to the conveyor units 1 under the load carrier 2, there is only a specific range of values ​​for the possible distance between the blocks 4A to 4C and the sensors 3A to 3D that pass by them during the movement.If a distance value measured by sensor 3A to 3D for a detected body lies outside this value range, it can be ruled out that the detected body is a block of the charge carrier 2. In this way, the actual insertion under a charge carrier can be verified. Additionally or alternatively, the actual insertion of the F order units 1 under a charge carrier 2 can also be verified using further sensors, for example, using one or more sensors with a vertically oriented detection range that detect the presence of cover boards of the charge carrier 2.

[0034] In the example shown in Figure 2, as soon as sensor 3A detects the presence of block 4C, a distance measurement using one or more sensors on the rollers 5 would be sufficient to achieve complete underpassing of the load carrier 2. The conveyor unit 1 could then continue moving under the load carrier 2 until the rollers 5 have traveled a predefined distance and complete underpassing of the load carrier 2 has been achieved. Alternatively, as the unit continues moving, sensor 3A could "count" the subsequent blocks 4B and finally 4A, with the detection of the third block 4A indicating complete or near-complete underpassing of the load carrier 2.

[0035] To ensure complete insertion under the load carrier 2, the example shown utilizes additional sensors 3B to 3D, which also perform distance measurements from the current position, oriented horizontally and perpendicular to the direction of entry of the conveyor unit 1. Thus, when the conveyor unit 1 has not yet entered under the load carrier 2, none of the blocks 4A to 4C are detected by any of the sensors 3A to 3D, as is the case with the conveyor unit 1 shown on the left in Figure 2. At the beginning of insertion under the load carrier 2, only the foremost sensor 3A detects a block 4C, while the remaining sensors 3B to 3D detect a distance approaching infinity, as is the case with the conveyor unit shown on the right in Figure 2. The respective distance measurements are symbolically represented by horizontal lines in Figures 2 and 3.

[0036] As the conveyor unit 1 continues to move inwards, sensors 3A to 3D pass by blocks 4A to 4C, as shown in Figure 3. In the example shown, complete passage under the load carrier 2 is achieved when sensors 3A and 3D, located at the front and rear of the conveyor unit 1, detect blocks 4A and 4C, while sensors 3B and 3C, located in the middle of the conveyor unit 1, measure a distance towards infinity.

[0037] When fully under the load carrier, the conveying units 1 can move the load carrier 2 they have passed under laterally, i.e., perpendicular to the direction of entry, after lifting it. If one imagines that the physically unconnected conveying units 1 can pass through any number of load carriers 2 positioned one behind the other and aligned with each other within the available clearance space, in order to position themselves under a specific load carrier 2, lift it, and finally move it laterally out of the arrangement of load carriers, the importance of reliably determining the position of the conveying units under a load carrier they have passed under becomes clear. The counting logic described above can be used to approach a specific load carrier 2 within an arrangement of load carriers.For example, sensors 3A to 3D can be used to detect how many load carriers 2 have already been traversed by the conveyor units 1 in order to position the conveyor units 1 under the desired load carriers 2. In this way, the recurring pattern of the individual blocks 4A to 4C can also be detected for each load carrier. When traversing an arrangement of several load carriers 2 positioned one behind the other, it is also conceivable to detect the spaces or gaps formed between the individual load carriers 2 using the sensors 3A to 3D described above, in order to deduce the position of the conveyor unit 1 in relation to the load carrier arrangement.With regard to the aforementioned "Euro pallet," the chamfered or rounded vertical edges of the blocks could also be detected using distance measurement, so that even if there is no free space between the individual load carriers 2, the transition from one load carrier 2 to a second load carrier 2 can be detected. A faulty distance measurement due to possible wheel slippage could, for example, be verified by measurements using the distance sensors 3A to 3D. Similarly, communication between the individual conveying units forming a conveying system could reveal possible wheel slippage, for example, if the distances measured by the individual conveying units 1 and communicated between them differ.

Claims

Applicant: FILICS GmbH Legal file: P102373WO XX Patent claims 1. Method for determining the spatial position of a conveying unit (1) for conveying load carriers (2) relative to a load carrier (2) under which the conveying unit (1) passes, comprising the following steps: - Detecting at least one distance between at least one reference point (3A-3D) assigned to the conveying unit (1) and at least one surface (4A-4C) assigned to the charge carrier (2); - Acquisition of model data which includes an assignment of at least one acquired distance to a cross-sectional section (6A-6E) of the charge carrier (2); - Determine, based on the at least one recorded distance and the recorded model data, a spatial position of the conveying unit (1) relative to the load carrier (2).

2. Method according to claim 1, wherein the at least one distance is recorded at at least two successive points in time, in particular continuously.

3. Method according to claim 2, wherein the spatial position of the conveying unit (1) relative to the load carrier (2) is determined on the basis of at least one detected change in position.

4. Method according to one of claims 1 to 3, wherein the spatial position of the conveying unit (1) relative to the load carrier (2) is additionally determined on the basis of a distance traveled by the conveying unit (1) since the detection of the distance / change in position.

5. Method according to claim 4, wherein the distance traveled is detected by means of a detected rotational movement, in particular a detected number of revolutions of at least one roller (5) of the conveying unit (1).

6. Method according to any one of claims 1 to 5, wherein the detection of the at least one distance is carried out in a direction predefined relative to the conveying unit (1), in particular transverse to the longitudinal direction of the conveying unit (1) and / or in a horizontal direction when the conveying unit (1) is oriented as intended.

7. Method according to one of claims 1 to 6, wherein the detection of the at least one distance is carried out by means of at least one sensor (3A-3D) arranged on the conveying unit (1), in particular at least one sensor (3A-3D) designed for time-of-flight measurement.

8. Method according to claim 7, wherein simultaneous detection of several distances is carried out by means of an arrangement of several sensors (3A-3D), which are designed in particular for measuring the position in substantially parallel directions and / or are arranged substantially along the longitudinal direction of the conveying unit (1).

9. Conveyor unit for conveying load carriers (2), comprising an elongated frame structure (7) movable by means of an arrangement of several rollers (5), a support element (8) which can be raised and lowered in a vertical direction relative to the frame structure (7) by means of a lifting device, at least one sensor (3A-3D) designed to detect a distance between a reference point (3A-3D) assigned to the conveyor unit (1) and a surface (4A-4C) assigned to the load carrier (2), and a control system connected to the at least one sensor (3A-3D) for controlling the conveyor unit (1), wherein the control system is configured to carry out the method according to one of claims 1 to 8.

10. Conveying unit according to claim 9, wherein the conveying unit (1) has one or more of the following features: - the conveying unit (1) forms a conveying device with another, in particular identical, conveying unit (1), wherein the two conveying units (1) are designed for mutual communication with each other; - the at least one sensor (3 A-3D) is designed to detect the at least one distance in a direction predefined relative to the conveying unit (1), in particular transverse to the longitudinal direction of the conveying unit (1) and / or in a horizontal direction when the conveying unit (1) is oriented as intended; - at least one sensor (3 A-3D) is a sensor (3A-3D) designed for time-of-flight measurement; - the conveying unit (1) comprises an arrangement of several sensors (3 A-3D), which are designed in particular for distance measurement in substantially parallel directions and / or substantially along the longitudinal direction of the conveying unit (1) are arranged; - the conveying unit (1) includes at least one sensor designed to detect a distance traveled by the conveying unit (1), in particular to detect a rotational movement, specifically to detect a number of revolutions of at least one roller (5) of the conveying unit (1).

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