Heterogeneous palletization method and system

Abstract

The invention relates to a palletization method, in which: - items (i) are transported towards a loading point, where the items (i) are loaded by a loading device onto a container (5) placed at a loading station, - the loading device is controlled by computer control means, the method further comprising a step for generating a stable arrangement of the items (i) on the container upstream of their loading, - the stable arrangement comprises placing items having substantially similar heights to form a layer, where a partial layer (Ci) having a first height occupies a part of the container and at least one complementary partial layer (Ci') having a second height occupies a second unoccupied part so as to occupy the entire surface area of ​​the container. The invention also relates to a system for carrying out the method.

Description

[Technical field]

[0001] The present invention relates to the field of logistics platforms for large and medium-sized distribution, and to a process and system for palletizing goods before delivery to a customer. [Background technology]

[0002] The logistics platform acts as an intermediary between suppliers and the various sales points. Suppliers send their products to these platforms, where they are received and processed for storage. The sales points then send their replenishment requests to these platforms. For each request, the requested products are distributed and sent to an order preparation zone. In the preparation zone, robots are used to place the products on shipping pallets, which are then transported to their destination.

[0003] In addition to managing the distribution of products and transporting orders to customers, several decisions must be made including how many pallets to use, which pallets to place the goods on, and how to place the goods on each pallet. There are two main manifestations of layered solutions when it comes to placing goods on pallets. The first representation consists of a stack of interchangeable layers of the same width / length dimensions. The second expression consists in laying down layers of any size, without any precise rules to follow.

[0004] Due to the diversity of the objects to be placed, the first representation is too restrictive, since many objects cannot be placed in a full layer, for example with a size of 1200×800 mm, due to their small quantity. The near-optimal solution obtained by the method dedicated to this representation therefore involves too few objects to be placed.

[0005] Moreover, in the second representation, the variety of possible layer dimensions makes the design of the layered solution too complicated: known methods are unable to achieve a quality solution, resulting in a layout with a low number of placed objects and lacking stability. Summary of the Invention [Problem to be solved by the invention]

[0006] It is therefore an object of the present invention to provide a palletization system and process for solving the problems of the above mentioned methods and achieving a layered arrangement of articles on a container that is efficient in terms of the articles placed thereon as well as their stability. [Means for solving the problem]

[0007] To this end, according to a first aspect, the present invention provides a method for producing a method for treating a cancer cell comprising: - articles of heterogeneous shape (especially having variable dimensions) are transported by conveying means to a loading station, - the goods are then loaded in several layers by a loading device onto containers placed at the loading station, The present invention relates to a palletization process, wherein the loading device is controlled by computer control means and the process further comprises the step of generating a stable arrangement of said articles on the containers upstream of their loading.

[0008] According to the invention, the stable arrangement includes placing articles of substantially similar height to form either a full layer occupying substantially the entire surface area of ​​the container, or partial layers each occupying a portion of the surface area of ​​the container; A first partial layer having the height of the first layer occupies a portion of the container, and at least one complementary partial layer having the height of the second layer occupies a second portion not occupied by the first layer so as to occupy the entire surface area of ​​the container.

[0009] Given the variability of the dimensions of the objects to be placed (especially their height), the process according to the invention defines a layer of objects to be placed which can be complete (occupying the entire surface area of ​​the container) or partial (occupying a part of the surface area), the layer being formed by objects having substantially similar heights (with small gaps between them).

[0010] By combining full and partial layers in the solution, the process allows for a large number of items to be placed on a container, thus limiting the volume that can be lost.

[0011] Additionally, by placing the items in layers and ensuring that they are properly positioned in height, the stability of the container is enhanced.

[0012] Thus, unlike known methods, the process according to the invention allows efficient palletization in terms of the number of articles placed and in terms of stability.

[0013] The container may be any container used to palletize goods, for example for shipping of goods to a customer. By way of example, it may be a pallet.

[0014] According to an exemplary embodiment, the partial layer may occupy half of the surface area of ​​the container (e.g., half the length and the entire width, or vice versa), or may occupy other proportions, such as 1 / 3 or 1 / 4.

[0015] By setting a number of possible layer sizes, the number of layers considered is thus limited, which may make it easier to arrive at a quick solution.

[0016] For example, add two quarter-ply stacks to a half-ply stack. Depending on the dimensions of the objects to be placed, this alternative may prove to be much more effective. This alternative may be particularly useful when there are many small objects of very different heights.

[0017] Advantageously, two partial layers of substantially the same surface area can be superimposed, which makes it possible to fill containers such as pallets by creating columns that maximize the occupied volume and stability.

[0018] Advantageously, two partial layers are separated by a partial spacer plate of substantially the same surface area as said partial layers. The use of spacers between partial layers of the same stack significantly adds stability to the container after loading, thus increasing the robustness of the arrangement.

[0019] Optionally, the nature of the spacers may allow them to compensate for variations in height of the layer on which they are placed while still maintaining rigidity, thereby further increasing stability.

[0020] According to an exemplary embodiment, the partial layer and at least one complementary partial layer are placed on the complete layer. By choosing this strategy, the occupied volume and the stability are increased.

[0021] Advantageously, a complete spacer plate may also separate the complete layer from the partial layer, said complete spacer plate having substantially the same surface area as the container, which further increases stability.

[0022] According to an embodiment, the process may include generating a catalog of layers likely to be placed on the container, said catalog including at least one partial layer.

[0023] The advantage of the catalog is that it defines the possible layers upstream of any layer design and the process is restricted to using them in the most efficient way. The fact that the layer catalog also includes partial layers makes it easier to obtain an arrangement of items on a container (e.g., a pallet) that maximizes the occupied volume and stability.

[0024] According to an embodiment, the catalog can be incrementally improved by adding new possible layers with strictly negative reduced costs, said reduced costs being estimated from the solution of the following linear problem, which can be produced by methods known to those skilled in the art (e.g., the simplex method):

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number

[0025] This dynamic generation method assigns to each object in a given set of layers a target value using the formula above. This value, which can be positive or negative, is used to evaluate layers that do not yet belong to the catalog. If said layer has a strictly negative reduced cost, it is added to the set of layers included in the catalog in order to improve the resulting layered arrangement of the articles before palletization.

[0026] Another advantage is that if there are no more layers that satisfy the above condition, it allows the set of layers to represent the optimal solution, so this property not only allows us to know when to stop, but also allows us to use other formulas to determine the limit of the quality of the optimal solution.

[0027] The costs saved are:

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[0028] The layer gain can be described by the following formula:

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[0029] In the formula, ν c is the volume of the layer and α is a sufficiently small real number, so that the benefits of the two layers are first evaluated according to the volume of the object placed on them.

[0030] For this same volume, the benefits are compared according to the volume that the layer occupies (also called the "density" of the layer).

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[0031] variable

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[0032] It is also possible to reformulate the objective of maximizing volume as minimizing the unplaced volume:

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[0033] According to an exemplary embodiment, to generate a stable arrangement of items, a layer is selected from the catalog that maximizes the total profit, subject to the constraint that all layers can be placed on the container without exceeding the container height limit set upstream.

[0034] For a catalog C at layer c, it is possible to determine which layers to choose to construct the solution by, for example, solving the following linear program (a solution methodology known to operations research specialists):

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[0035] The constraint h(A) ensures that the collection of layers can be placed without any of the layers exceeding a set height limit, denoted as H.

[0036] Optionally, the process can include the use of learning methods to generate layers given as parameters to a "linear programming in integers", which results in improvements when the objects to be palletized change little from one solution to another.

[0037] Optionally, the computer means may include an internal memory and thus be able to store the iterative layers passed as parameters to the "Linear Programming in Integers".

[0038] Optionally, the process may include applying the method to a set of objects that are placed on two or more pallets, whereby the distribution of the objects should be taken into account and their consolidation facilitated by the concept of layers.

[0039] The invention according to a second aspect also relates to a palletization system implementing a process according to one of the combinations of characteristics mentioned above.

[0040] The palletization system: a loading station which may be equipped with a zone for receiving a container and a loading device; - conveying means for transporting goods of heterogeneous shape to a loading station so that they are loaded in several layers onto the container by the loading device;

[0033] The loading device is controlled by a computer control means configured to carry out the above process to generate a stable arrangement of said items on the container.

[0041] Further characteristics and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, given as a non-limiting example of the invention, in which: [Brief description of the drawings]

[0042] [Figure 1] 1 illustrates an example of a palletization system according to the present invention. [Diagram 2] FIG. 1 is a diagram of a loaded pallet with a full layer and a half layer of items. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] Figure 1 shows an example of a palletization system according to the invention. The system 1 comprises a conveying means 2 for transporting objects i to a loading station and loading them onto empty containers 5 (pallets) placed at the loading station. In this example, the conveying means 2 is a conveyor, but other conveying means can be used, in particular automatically guided robots (AMR / AGV).

[0044] The palletization system 1 also comprises loading means 4 for loading the items i onto the pallets 5. The loading means 4 is for example a multi-axis robot equipped with grippers 4a for gripping the items i one by one and placing them on the pallet 5. The grippers 4a can have a grid as shown in the figure or any other known shape, for example equipped with suction cups.

[0045] In one alternative, not shown, the palletization system 1 may also comprise article detection means, for example a camera, arranged above the conveying means 2 in the vicinity of the loading station.

[0046] The system 1 also comprises control means, not shown, arranged to manage the loading of the articles by the loading means 4. It may also control the conveying means.

[0047] The control means may comprise computational means, such as software, capable of determining the arrangement and spatial position sequence of the items i to be stacked on the pallet 5 .

[0048] Advantageously, the control means may also comprise a memory arranged to host a database containing characteristics of the parcels to be stacked, for example as a result of a customer order. The database may include dimensions, weight or other characteristics of the items.

[0049] Figure 2 shows an example of an arrangement of articles on a pallet 5 being loaded using the process according to the invention. In the arrangement of articles shown, the process lays down two full layers Cc superimposed on each other, each comprising a set of articles of similar height. Articles i-1 to i-4 of similar height are then placed in a partial layer Ci occupying half of the surface area of ​​the pallet 5. Articles i-5 to i-8 of similar height are placed in a complementary partial layer Ci' occupying the other half of the surface area of ​​the pallet.

[0050] Further partial layers can be added to the layers Ci and Ci', for example one or several layers of the same dimensions can be superimposed on Ci'. These two layers can also be separated by a spacer plate to enhance the stability of the pallet. Spacer plates can also be added between the full layers and between the upper full layer Cc and the partial layers Ci, Ci' to increase stability.

[0051] Dynamic generation of layer catalogs : To generate the catalog and to improve it progressively by taking into account items not yet included, software included in the computer control means calculates the reduced cost of each possible full layer Cc or partial layer Ci, which is:

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[0052] If the reduced cost value is strictly negative, the tier is added to the catalog.

[0053] The operation is repeated until the new partial or full layer no longer satisfies the above conditions.

[0054] In the above formula, u i is the dual value of the layer c considered (the only constraint in the problem).

[0055] u i The value of and the reduced cost are solved for the following linear problem:

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number

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[0056] Methods for solving such problems are not detailed here, as they are familiar to operations research specialists. Well-known solvers such as GLPK may be used to solve this problem.

[0057] Selection of layers to be laid: In this step, a process is implemented by the software to select from a catalogue the complete or partial layers to be placed on the container (pallet) by the robot 4. The layers selected from the catalogue C are selected based on the profit (p c ) is maximized.

[0058] The layers are selected by solving the following linear programming problem (the solution method is known to operations research experts):

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[0059] The constraint h(A) ensures that the collection of layers can be placed without any of the layers exceeding a set height limit, denoted as H.

[0060] For example, in the case of a full sheaf, the constraint h(A) can be expressed as:

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[0061] If a full layer and a half layer with dimensions 600x800 or a half layer with dimensions 1200x400 are used, the additional constraints are:

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[0062] During the ceremony,

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[0063] variable

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[0064] Dynamic vs. Random methods: To evaluate the effectiveness of the dynamic generation method described above, it is compared with a random generation method known from the prior art.

[0065] The results obtained for Z(C) in both cases, as well as for the Lagrangian limit (known to those skilled in the art) used as a reference, are given below.

[0066] Simple case: Z(C)(dynamic): 172; θ(u): 170; Z(C)(random): 179 Medium case: Z(C)(dynamic): 171; θ(u): 155; Z(c)(random): 230 Hard case: Z(C)(dynamic): 145; θ(u): 128; Z(C)(random): 190

[0067] To account for the difference between both methods, the GAP (percentage) between the value z(C), where C is the catalog generated by one method or the other, and the Lagrangian limit for z(C) is calculated. The lower the GAP, the more efficient the method.

[0068] The difference between the obtained z(C) value and the Lagrangian limit of z(C) is: Simple case: Dynamic: 1.18%; Random: 5.70% Medium cases: Dynamic: 10.30%; Random: 47.85% Hard cases: Dynamic: 13.54%; Random: 48.44%

[0069] These results clearly demonstrate the effectiveness of the dynamic method described above compared to the random methods known from the state of the art.

Claims

1. It is a palletization process, - An item (i) with an irregular shape is transported to a loading station by a transport means (2), Next, the item (i) is loaded into several layers (Cc, Ci) by the loading device (4) onto the container (5) placed at the loading station. The loading device (4) is controlled by computer control means, and the process further includes the step of generating a stable arrangement of the articles (i) on the container upstream of their loading, The stable arrangement includes placing articles of substantially similar height to form either a full layer (Cc) that substantially occupies the entire surface area of ​​the container, or partial layers (Ci, Ci') each that occupy a portion of the surface area of ​​the container. A palletization process characterized in that a first sublayer (Ci) having the height of the first layer occupies a portion of the container, and at least one complementary sublayer (Ci') having the height of the second layer occupies the second portion not occupied by the first layer, such that it occupies the entire surface area of ​​the container.

2. The palletization process according to claim 1, wherein two sublayers having substantially the same surface area are superimposed.

3. The palletization process according to claim 2, wherein the two sublayers are separated by a partial spacer plate having substantially the same surface area as the sublayers.

4. The palletization process according to claim 1, wherein a partial layer (Ci) and at least one complementary partial layer (Ci') are placed on a complete layer (Cc).

5. The palletization process according to claim 1, wherein a complete spacer plate separates a complete layer (Cc) from a partial layer (Ci, Ci'), and the complete spacer plate has substantially the same surface area as the container (5).

6. The palletization process according to claim 1, further comprising the step of generating a catalog C of layers that are likely to be placed on a container, wherein the catalog includes at least one sublayer.

7. The catalog is progressively improved by adding a new layer c which has a strictly negative cost, and the cost is determined by the following linear problem. [Math 1] It is estimated from the solution, and in the formula, - z(C): A value corresponding to the best possible layer benefit obtainable using the actual number of layers in catalog C. - p ｃ This is the benefit of layer c, which is evaluated as the volume of an object in layer c, plus a penalty proportional to the volume occupied by layer c in the container. - λ ｃ : This is the number of times layer c is used. － [Math 2] : This is the number of items i in layer c, - I: The set of item references i known to the system, ni: The number of times the reference i can be used, The aforementioned cost CR(c) is given by the formula [Math 3] It is represented by, In the formula, u ｉ is a constraint [Math 4] It is the dual of, Layer's profit p ｃ The following formula [Math 5] It is expressed as, in the formula, ν ｃ The volume of that layer is ν ｉ The palletization process according to claim 6, wherein is the volume of article i and α is a real number.

8. A complete or partial layer is selected from the catalog, and this is subject to the constraint that the set of selected layers can be placed on the container and does not exceed the height limit of the container set upstream, and the benefit (p ｃ The palletization process according to claim 7, which maximizes the sum of ).

9. It is a palletization system, - A loading station having zones for receiving containers (5) and loading devices (4), - A transport means (2) for transporting articles (i) of irregular shape to a loading station so that they are loaded in several layers (Cc, Ci) onto a container (5) by a loading device (4). Equipped with, A palletization system in which a loading device (4) is controlled by computer control means configured to generate a stable arrangement of the articles on a container by performing the process described in any one of claims 1 to 8.

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