Patent Description:
In known systems, the tiles also serve for preventing collisions between vehicles. In that case the control server takes as the starting point that a tile may only be occupied by a vehicle that travels along a movement path defined for the vehicle, if this tile is (temporarily) reserved for that vehicle. It is not possible to reserve a tile at the moment when this tile is occupied by another vehicle or is already reserved for another vehicle. In certain systems it may also be that a tile is not available to be reserved, for example in order to prevent a deadlock situation arising or to limit the density of vehicles in a certain part of the movement area, even if the tile in question is not at that moment occupied by another vehicle or is not reserved for another vehicle. In particular, as the density of vehicles within a movement area increases, the risk of this kind of deadlock situation arising also increases. A deadlock situation is a situation in which a number of vehicles are unable to continue on their respective movement paths because they would be in each other's way if they were to continue on their respective movement paths. In a deadlock situation there is always a so-called circular waiting state wherein each vehicle of a group of vehicles would have to reserve a tile in order to be able to continue on its movement path, which is already reserved for another vehicle of that group. A deadlock situation of this kind would also include a situation in which two vehicles are opposite each other and their respective movement paths are directed toward each other.

European patent <CIT> discloses a goods handling system. In use of this system vehicles transport racks to an operator station. At least a portion of a transportation path is transmitted to the vehicle and locations of the vehicle along the transportation path are monitored based on marker information that is detected by the vehicle. The markers are located at predetermined positions. A method according to the preamble of claim <NUM> and a system according to the preamble of claim <NUM> is known from <CIT>.

The invention aims to provide a method for implementing a system for transporting products that can be applied with increased efficiency. For this purpose the invention firstly provides a method as claimed in claim <NUM>. According to the present description, the central control server can be implemented both in hardware and in software; in hardware because the functionality is for example implemented in a Field Programmable Gate Array, FPGA, or an Application Specific Integrated Circuit, ASIC; in software because the functionality is for example carried out by one or more Central Processing Units, CPUs, microcontrollers, or something similar. The central server may be a standalone server, a cloud implemented server, a distributed server or processing sources in a data center. The word "next" in the phrase "next tile" expresses that it concerns one or at least one tile not yet reserved for the vehicle in question, which adjoins the or a first tile that is already reserved for that vehicle or that is occupied by that vehicle, to allow the vehicle to travel along the movement path that the central control server has defined for that vehicle.

The invention is based on the understanding that the application of tiles may admittedly be very useful and effective for preventing collisions and possible deadlock situations, but that if, when determining the movement paths, no use is made of the tiles, the efficiency of the system may increase. By defining movement paths independently of the tiles, there is in principle an increased degree of freedom for the central control server to determine the movement paths, so that for example a straight line may be selected between two points within the movement area as (part of a) movement path even if this straight line does not fit in the structure of the tiles used. In the case of square tiles of equal size, said tiles defining two principal directions that are oriented perpendicular to each other, it can for example easily be recognized that for movement of a vehicle along the two catheti of a right-angled triangle, extending parallel to the respective principal directions, it is possible to choose to follow the hypotenuse of the triangle, wherein the length of the hypotenuse and thus of the path to be travelled by the vehicle is by definition less than the sum of the lengths of the other two sides. Despite this greater freedom for defining efficient movement paths, in the invention the tiles can be used effectively for prevention of collisions between vehicles and optionally for prevention of deadlock situations in a manner that is already familiar to a person skilled in the art.

The advantages of the invention may in particular be under discussion if at least two vehicles of the plurality of vehicles differ from one another with regard to shape and/or size and/or the drive devices or drive units thereof and/or the control devices or control units thereof. There is then said to be a heterogeneous fleet of vehicles. The vehicles will differ from one another with regard to their movement behavior, for example with regard to their maximum speed, their maximum acceleration/deceleration, the radius of curvature of bends that they may encounter and/or the space that they take up. Thus, it may be that the respective movement paths between points A and B as determined by the central control server differ by type of vehicle.

If the shape and dimensions of at least one tile, preferably of the greatest proportion of the number of tiles, more preferably of all tiles, is such that at least one of the vehicles, preferably each vehicle, does not fit within the perimeter of the at least one tile, a fine-meshed system is obtained, so that it can be established more accurately whether collisions or deadlock situations are likely to arise, and so that the chance of that occurring is in principle smaller, so that the system can be applied more efficiently.

In order to be able to anticipate local situations within the movement area and make efficient use of the available computing power of the central control server, it may be preferable that at least two tiles of the plurality of tiles differ from one another with regard to shape and/or size. Thus, for example, in practice for relatively busy parts of the movement area it may be preselected to use smaller tiles than in relatively calm parts of the movement area. Furthermore, the shape of the tiles may be adapted to the available space. In a long narrow passageway where vehicles cannot pass each other it may for example be chosen to use a tile whose shape and size matches that of the passageway, although it may also be chosen to divide said passageway into a larger number of tiles so that vehicles can follow each other relatively closely in a passageway of this kind.

The aforementioned advantages may also be under discussion if two tiles that differ from one another with regard to shape and/or size do not adjoin an edge of the movement area, where for geometric reasons it may be that tiles are preselected that differ with regard to their shape or size from tiles that do not adjoin an edge of the movement area.

In particular, to promote smooth and efficient movement of vehicles along their movement paths, in one embodiment the method may advantageously comprise the steps of.

This embodiment could also find useful application if a vehicle is located in a part of the movement area where it is less busy, so that there is relatively little likelihood of collisions or deadlock situations. This embodiment will also be rather advantageous if the tiles in the movement path are relatively small and for example so small that the vehicle in question cannot fit in them.

In a further embodiment of the method according to the invention, the central control server comprises a library of a number of path segments within the movement area and comprises the step of determining, by the central control server, a movement path for the vehicle, making use, by the central control server, of the library in such a way that the movement path is formed at least partly, preferably completely, by a single path segment or is constructed from contiguous path segments. A method of this kind offers the advantage that determination of a movement path by the central control server, for which limited computing capacity is required, can be carried out extremely efficiently, and in addition the risk of collisions or deadlock situations can be reduced effectively because movement paths that are determined for different vehicles at least partly overlap, as the same path segments are used and in these path segments the vehicles are able to move one after another.

The invention is suitable in particular for application in sorting of products. In particular, for this application it may be advantageous if the method comprises the steps of.

The invention also relates to a system according to claim <NUM>.

The advantages of this kind of application have already been explained above on the basis of the explanation of the method according to the invention.

The invention will be explained in more detail on the basis of the description of an embodiment of a method and system according to the invention, not to be interpreted as limiting the invention, referring to <FIG>.

<FIG> shows a schematic top view of a part of a system according to the invention. More specifically, <FIG> shows a square part <NUM> of a movement area, with two fixed obstacles <NUM>, <NUM>, such as a column or rack, located within said part <NUM> of the movement area. The movement area is formed by a floor or at least a part thereof. The floor may be provided covered inside a building. The system further comprises a central control server, not shown in more detail, which has divided the movement area into square virtual tiles <NUM>. These tiles <NUM> are thus in reality not visible or at least need not be visible. The size of the tiles <NUM>, which on account of the nature of tiles in general have or cover an area, is such that none of the vehicles of the heterogeneous fleet fits completely within a tile <NUM>. The tiles <NUM> that border on an obstacle <NUM>, <NUM> have a shape that deviates from a square shape, on account of said obstacles <NUM>, <NUM>. It is also possible, also at a distance from the obstacles <NUM>, <NUM>, to represent the movement area with other than square tiles, for example with a larger tile the size of two by three tiles <NUM> as shown with the thickened line <NUM>. The tiles used may also be of a size such that vehicles 5a and 5b to be designated hereunder or optionally even also vehicle <NUM>, would each be able to fit within the perimeter of a tile of this kind.

The system further comprises a heterogeneous fleet of vehicles, with <FIG> showing vehicles 5a, 5b and <NUM> located within part <NUM> of the movement area. Vehicles 5a and 5b are of identical configuration and are smaller and more maneuverable than vehicle <NUM>. Each of the vehicles 5a, 5b, <NUM> has a drive motor or at least arrangements by which in each case they move within the movement area as well as a carrying platform for carrying an object for example such as a parcel thereon.

The central control server and each of the vehicles 5a, 5b, <NUM> are configured to send and to receive wireless signals. By means of these signals, the central control server is for example able to send instructions to each of the vehicles 5a, 5b, <NUM>, which can be received by each of the vehicles 5a, 5b, <NUM>, at least in so far as they are intended for said vehicles 5a, 5b, <NUM>. On the basis of these instructions, the vehicles 5a, 5b, <NUM> will among other things move over the movement area. The vehicles 5a, 5b, <NUM> may for example send information about their position within the movement area and/or about a path travelled by the vehicles within the movement area, to the central control server which is configured to receive and process this information.

During application of the system, the central control server receives orders to move a vehicle within the movement area from a starting position of that vehicle to an end position. In reaction to this, the central control server determines a movement path for the vehicle in question, said movement path extending between the aforementioned starting position and end position. Line <NUM> shows, at least in the part of the movement area shown in <FIG>, overlapping parts of movement paths for vehicles 5a and 5b, while line <NUM> shows a part of the movement path for vehicle <NUM>. When determining the movement paths, the central control server takes no account of the tiles <NUM>, or the structure thereof. This is also clear from the shape and direction of lines <NUM> and <NUM> in <FIG>, representing parts of movement paths. The central control server does take into account the boundaries of the movement area and obstacles, such as obstacles <NUM>, <NUM>, within the movement area. The arrows on the vehicles 5a, 5b and <NUM> point to the end position of the respective movement paths <NUM>, <NUM> or at least in the direction of movement of the respective vehicles 5a, 5b, <NUM>.

When determining the movement path of a vehicle, in one embodiment of the invention it is possible that the central control server has a library of a number of path segments, wherein the central control server at least partly constructs a movement path, to be determined by the central control server, from a single path segment or from a plurality of path segments, whether or not contiguous. The part of movement path <NUM> shown in <FIG> could for example be a path segment of this kind or said contiguous path segments. It is also possible or often even advantageous that the central control server is then configured to assume, when determining a movement path, that a path segment may only be travelled by a vehicle in one of two opposite directions.

On the basis of information that is available to the central control server relating to the position of each of the vehicles 5a, 5b and <NUM>, the central control server determines which of the tiles <NUM> are occupied partly or completely by the vehicles 5a, 5b and <NUM>. In so far as there is mention hereunder or there is mention in the foregoing about a tile that is occupied by a vehicle, said tile may be occupied both partly and completely. Moreover, an occupied tile is by definition also reserved. This reservation is only removed when the vehicle in question has left the tile completely.

The aforementioned occupied tiles are indicated with reference number <NUM>' and are cross-hatched. Dotted tiles <NUM>" indicate the tiles <NUM> that have been reserved by the central control server for an associated vehicle 5a, <NUM>. Reserving of successive tiles <NUM> for a vehicle may take place by the central control server at the moment when that vehicle has reached the front tile(s) of the currently already reserved tiles <NUM> but still before said front tile/tiles <NUM> has/have been reached.

For vehicle 5b, (still) no tiles <NUM>, not yet already occupied by vehicle 5b, have been reserved by the central control server, since the tile(s) <NUM> adjoining the present position of vehicle 5b, which on further movement of vehicle 5b along its movement path <NUM> would be occupied, is/are already reserved or at least is/are occupied by vehicle <NUM>. The rules that are followed by the central control server when reserving a tile for a vehicle oppose occurrence of this kind of reservation if the respective tile(s) is/are already occupied by or is/are reserved for another vehicle. Thus, by making use of the tiles <NUM>, collisions between vehicles of the system can be prevented in an effective manner.

Claim 1:
A method for implementing a system for transporting products, said system comprising
- a plurality of vehicles (5a, 5b, <NUM>), wherein each vehicle is configured to move over a floor within a movement area and is configured to carry at least one product to be transported;
- a central control server configured for controlling the vehicles, wherein the central control server comprises a digital representation of the movement area, said representation comprising a plurality of contiguous tiles (<NUM>, <NUM>', <NUM>");
in which the method comprises the steps of:
- receiving or generating, by the central control server, an order to move a vehicle within the movement area from a starting position of the vehicle to an end position,
- determining, by the central control server, in reaction to the order, independently of the tiles in accordance with the digital representation, a movement path (<NUM>, <NUM>) for the vehicle, said movement path extending from the starting position to the end position
- after the movement path for the vehicle has been determined by the central control server, determining by the central control server which contiguous tiles will be occupied by the respective vehicle during movement by the vehicle along the movement path,
- receiving or generating, by the central control server, a request for execution of a next step by the vehicle to reserve at least one successive tile in the movement path determined for the vehicle,
- at least on condition that it has been determined by the control server that the at least one successive tile is available, reserving, by the control server, the at least one successive tile for the vehicle and then movement of the vehicle along the movement path determined for the vehicle so that the at least one successive tile is occupied,
- after a vehicle has completely passed a tile reserved for that vehicle, removing the reservation by the central control server,
characterized in that said tiles are virtual tiles.