Method for dynamically reassigning autonomous guided vehicles to destinations

Abstract

The invention relates to a method for controlling the movement of a fleet of autonomous guided vehicles on a traffic lane to reach destinations, said method comprising successive phases of assigning autonomous guided vehicles to said destinations, characterized in that each assignment phase is carried out by a central unit and comprises the steps of: - updating (100) a list of destinations in order of priority and a list of autonomous guided vehicles available to move to said destinations, - calculating (200), for each destination, a travel time for each vehicle to move to said destination, - assigning (300), for each destination to be reached in order of priority,an autonomous guided vehicle among the available autonomous guided vehicles not yet assigned to a destination during the current assignment phase and whose calculated travel time is the shortest to reach said destination. Figure to be published: Fig. 1,

Description

Title of the invention: Method for dynamic reassignment of autonomous guided vehicles to destinations Technical field

[0001] The invention falls within the field of logistics and relates more particularly to a method for controlling the movement of a fleet of autonomous guided vehicles on a traffic lane to reach destinations with successive phases of allocation of said destinations for said autonomous guided vehicles. Prior art

[0002] Some logistics centers are now equipped with autonomous guided vehicles, also called AGVs, designed to move on a traffic lane and carry out tasks of handling objects such as parcels or parcel receptacles.

[0003] The movement of the autonomous guided vehicles is controlled by a central unit configured to assign each vehicle to a destination where an object to be recovered or deposited is located while taking into account the availability of the vehicles, the objects to be handled and a predetermined order of priority in which the destinations must be reached, for example according to the order of a postman's delivery round.

[0004] However, the initially planned travel time of a vehicle to reach its destination according to the order of priority may be different from the travel time actually taken by the vehicle, in particular due to traffic problems on the road.

[0005] It is therefore common for vehicles not to reach their destination in order of priority.

[0006] This type of situation is generally dealt with on the one hand by limiting the number of tasks executed in parallel, for example by limiting the number of vehicles in operation, and on the other hand by providing a zone for reordering the vehicles at a common traffic point, the order being maintained after this reordering by then forcing traffic in single file.

[0007] If this previous solution works, it has multiple drawbacks, particularly in terms of performance. Indeed, when a vehicle has reached its destination, it can only move on to the next one if it is the first vehicle expected in the order of priority. In this case, it will have to wait in the reordering zone for the other vehicles to reach their destination in turn in order to let the highest priority vehicle pass. This wastes a lot of time in the reordering process. handling of objects, especially when the highest priority vehicle is experiencing traffic problems. Summary of the invention

[0008] The invention therefore aims to remedy the aforementioned problems.

[0009] To this end, the invention relates to a method for controlling the movement of a fleet of autonomous guided vehicles on a traffic lane to reach destinations, said method comprising successive phases of assigning the autonomous guided vehicles to said destinations, characterized in that each assignment phase is carried out by a central unit and comprises the steps consisting of:

[0010] - update a list of destinations to be reached in order of priority by the autonomous guided vehicles and a list of autonomous guided vehicles available to travel to said destinations to be reached among the autonomous guided vehicles in the fleet,

[0011] - calculate, for each destination to be reached, a travel time for each autonomous guided vehicle available to travel to said destination,

[0012] - assign, for each destination to be reached in order of priority, a vehicle autonomous guided vehicle among the available autonomous guided vehicles not yet assigned to a destination during the current assignment phase and whose calculated travel time is the shortest to reach said destination.

[0013] The idea behind the invention is to dynamically reassign the autonomous guided vehicles to the most appropriate destinations to reach the destinations in the predetermined priority order. The invention also makes it possible to reduce the travel time of the vehicles of all the assignment phases.

[0014] The method according to the invention may also have the following particularities:

[0015] - repeat the allocation phases cyclically;

[0016] - repeat the assignment phases at each destination reached by a guided vehicle autonomous ;

[0017] - repeat the assignment phases each time an autonomous guided vehicle travels a certain distance on the traffic lane;

[0018] - an object is loaded onto each available autonomous guided vehicle reaching its destination ;

[0019] - the central unit is configured for, when all the guided vehicles autonomous vehicles have reached their destination, order the movement of autonomous guided vehicles to another destination to be reached one after the other in order of priority;

[0020] - each object loaded onto an autonomous guided vehicle is unloaded when said autonomous guided vehicle reaches the other destination;

[0021] - said certain order of priority of the destinations to be reached corresponds to a tour factor distribution;

[0022] - the calculated travel times are calculated considering a speed equivalent nominal value for each autonomous guided vehicle moving on the traffic lane, of the spatial position of each destination to be reached and of the spatial position of each autonomous guided vehicle available on the traffic lane;

[0023] - the central unit is set to compare the calculated travel time of a autonomous guided vehicle to reach the first destination in the order of priority in a current assignment phase compared to the travel time of said autonomous guided vehicle to reach the first destination calculated in a previous assignment phase, and if the travel time calculated during the current assignment phase is not greater by at least a certain ratio compared to the travel time calculated during the previous assignment phase, the central unit does not apply the current assignment phase and maintains the previous assignment phase. Description of the drawings

[0024] The present invention will be better understood and other advantages will appear on reading the detailed description of the invention taken as a non-limiting example and illustrated by the appended drawings, in which:

[0025] [Fig. 1] The figure is a diagram representing an embodiment of the method according to the invention. Detailed description of the invention

[0026] The method according to the invention, as shown in the diagram of [Fig.l], makes it possible to control the movement of a fleet of autonomous guided vehicles on a traffic lane to reach predetermined destinations. This method is particularly suitable for implementation in a logistics center or a parcel sorting center.

[0027] The predetermined destinations may be loading or unloading points for parcel-type objects or parcel receptacles.

[0028] Autonomous guided vehicles, also called AGVs, are mobile robots designed to move along a traffic lane, for example, dedicated AGV aisles in a logistics center. AGVs can also perform handling tasks, such as retrieving or depositing said objects.

[0029] The VGAs according to the invention are controlled by a central unit configured to store digital data characterizing the VGAs and the destinations, operate a processing algorithm from the digital data and control the movement of said VGAs according to the results of the algorithm.

[0030] Thus, thanks to these settings, the central unit is capable of dynamically reassigning the VGAs to the different destinations. By dynamic reassignment it is understood that the central unit is designed to carry out successive phases of assignment of said VGAs to said predetermined destinations.

[0031] Thus, each allocation phase comprises a plurality of steps carried out by the central unit.

[0032] A first step 100 consists of updating a list of destinations to be reached in order of priority by the VGAs. The order of priority of the destinations to be reached could, for example, correspond to a delivery round of the postman. In this case, each destination could, for example, be associated with a destination of the postman's round.

[0033] The first step 100 also consists of updating a list of available VGAs to move to the destinations to be reached among the VGAs of the fleet. By available VGA is meant for example a VGA not loaded with an object, such as a parcel or a parcel receptacle.

[0034] A second step 200 then consists of calculating, for each destination to be reached, a travel time for each autonomous guided vehicle available to travel to said destination. Without restricting the scope of the invention, the calculated travel times may, for example, take into account an equivalent nominal speed for each autonomous guided vehicle traveling on the traffic lane, a spatial position of each destination to be reached and a spatial position of each autonomous guided vehicle available on the traffic lane. The acceleration and deceleration times of the AGVs may be considered negligible in the calculation of the travel times. The AGVs and the destinations may be equipped with spatial position sensors designed to transmit digital data corresponding to their spatial position to the central unit via a wireless link.

[0035] Finally, a third step 300 consists of assigning, for each destination to be reached in the order of priority, an autonomous guided vehicle from among the available autonomous guided vehicles not yet assigned to a destination during the current assignment phase and whose calculated travel time is the shortest to reach said destination. By current assignment phase is meant an assignment phase currently being executed by the central unit. Temporally, it is therefore understood that the current assignment phase is carried out after a previous assignment phase already executed and before a following assignment phase not yet executed.

[0036] Several allocation phases can therefore take place before all the VGAs, or even a single VGA, reaches its destination.

[0037] The central unit according to the invention may also be configured to compare the calculated travel time of an autonomous guided vehicle to reach the first destination in the order of priority in a current assignment phase with the travel time of said autonomous guided vehicle to reach the same first destination calculated in a previous assignment phase, and if the travel time calculated during the current assignment phase is greater by at least a certain ratio with respect to the travel time calculated during the previous assignment phase, the central unit does not apply, in step 310, the current assignment phase and maintains the previous assignment phase.On the contrary, if the travel time calculated during the current assignment phase is less than at least said certain ratio compared to the travel time calculated during the previous assignment phase, the central unit applies, in step 320, the current assignment phase instead of the previous assignment phase. For example, a ratio of 1 / 10 can be applied so as to avoid too frequent assignment changes, the time savings of which for all the VGAs to reach the destinations would be negligible.

[0038] Once each destination to be reached has received the assignment of an autonomous guided vehicle, the central unit is configured to control in a step 400 the movement of all the assigned AGVs towards the destinations.

[0039] By way of non-limiting example, the allocation phases may be repeated, as represented by the dotted arrow, according to at least one of the following three possibilities: cyclically (for example every 5 minutes), at each destination reached by an autonomous guided vehicle and each time an autonomous guided vehicle travels a certain distance on the traffic lane (for example every 10 meters).

[0040] It is thus understood that the autonomous guided vehicles assigned to a destination will continue to move for at least a certain time before receiving a new assignment which may be the same assignment as the previous assignment or another assignment.

[0041] In step 500, the central unit determines whether all destinations are reached by the VGAs.

[0042] If not, the central unit returns to step 400.

[0043] If yes, the central unit commands in step 600 the movement of the VGAs to carry out another mission.

[0044] An example of the progress of an allocation phase followed by a phase of moving the VGAs of the method according to the invention represented in [Fig.l] is described below.

[0045] In step 100, the central unit updates the list of destinations to be reached comprising three destinations from DI to D3 to be reached in a certain order of priority (DI then D2 then D3) and the list of available VGAs comprising two available VGAs VGA01 and VGA02 from a fleet of three VGAs from VGA01 to VGA03.

[0046] In step 200, the central unit calculates, for each destination to be reached, a travel time for each autonomous guided vehicle available to travel to said destination.

[0047] During this allocation phase only VGA01 and VGA02 are available. • DAi = time for VGA01 to reach DI • DBi = time for VGA02 to reach DI

[0048] and • DA2 = time for VG01 to reach D2 • DB2 = time for VG02 to reach D2

[0049] In step 300, the central unit assigns, for each destination to be reached in order of priority, an autonomous guided vehicle from among the available autonomous guided vehicles not yet assigned to a destination during the current assignment phase and whose calculated travel time is the shortest to reach said destination. • For DI considered as the highest priority destination • If DBi < DAi then send VGA02 to DI • VGA02 is no longer available • VGA01 is available • For D2 considered as the highest priority destination after DI • DA2 = time for VG01 to reach D2 • No other VGA • Send VGA01 to D2

[0050] In step 400, the central unit controls the movement of the assigned VGAs to the corresponding destinations.

[0051] During step 400, VGA01 has traveled 10 meters, the central unit then commands a new allocation phase by restarting the process from step 100, as represented by the dotted arrow. VGA03 is now available, in addition to VGA01 and VGA02. • For DI considered as the highest priority destination • DAi = time for VGA01 to reach DI • DBi = time for VGA02 to reach DI • DCi = time for VGA03 to reach DI • Min(DAi, DBi, Dci) = DBi • VGA02 remains assigned to DI • For D2 considered as the highest priority destination after DI • DA2 = time for VGA01 to reach D2 • DC2 = time for VGA03 to reach D2 • Min(DA2, DC2 ) = DA2 • VGA01 remains assigned to D2 • For D3 considered as the highest priority destination after D2 • DC3 = time for VGA03 to reach D3 • No other VGA • VGA03 is assigned to D3

[0052] After a certain time, VGA02 reaches D1, VGA02 is therefore no longer available within the meaning of the invention and D1 is removed from the list of destinations to be reached.

[0053] The central unit then commands a new allocation phase by restarting the process from step 100, as represented by the dotted arrow,

[0054] In the meantime, VGA01 was held up in a traffic jam due to a technical fault and therefore did not move forward. • For D2 considered as the highest priority destination after Dl • DA2 = time for VGA01 to reach D2 • DC2 = time for VGA03 to reach D2 • Min(DA2, DC2 ) = DC2 • VGA03 is assigned to D2 • For D3 considered as the highest priority destination after D2 • DA3 = time for VGA01 to reach D3 • No other VGA • VGA01 is assigned to D3

[0055] The assignment and movement phases continue until the VGAs gradually reach their destination and are each loaded with an object.

[0056] In step 500, the central unit determines whether all destinations are reached by the VGAs.

[0057] If not, the central unit restarts the process from step 400.

[0058] If yes, the central unit commands in step 600 the movement of all of the VGA to carry out other missions.

Claims

Claims

1. Method for controlling the movement of a fleet of autonomous guided vehicles on a traffic lane to reach destinations, said method comprising successive phases of assigning the autonomous guided vehicles to said destinations, characterized in that each assignment phase is carried out by a central unit and comprises the steps of: - updating (100) a list of destinations to be reached in order of priority by the autonomous guided vehicles and a list of the autonomous guided vehicles available to move to said destinations to be reached among the autonomous guided vehicles of the fleet, - calculating (200), for each destination to be reached, a travel time for each autonomous guided vehicle available to move to said destination, - assigning (300), for each destination to be reached in order of priority,an autonomous guided vehicle among the available autonomous guided vehicles not yet assigned to a destination during the current assignment phase and whose calculated travel time is the shortest to reach said destination.,

2. Method for controlling the movement of a fleet of autonomous guided vehicles according to claim 1, characterized in that the allocation phases are repeated cyclically.

3. Method for controlling the movement of a fleet of autonomous guided vehicles according to claim 1 or 2, characterized in that the allocation phases are repeated at each destination reached by an autonomous guided vehicle.

4. Method for controlling the movement of a fleet of autonomous guided vehicles according to any one of the preceding claims, characterized in that the allocation phases are repeated each time an autonomous guided vehicle travels a certain distance on the traffic lane.

5. A method of controlling the movement of a fleet of autonomous guided vehicles according to any one of the preceding claims, characterized in that an object is loaded onto each available autonomous guided vehicle reaching its destination.

6. Method for controlling the movement of a fleet of autonomous guided vehicles according to any one of the preceding claims, ca- characterized in that the central unit is configured to, when all the autonomous guided vehicles have reached their destination, command the movement of the autonomous guided vehicles to another destination to be reached one after the other in order of priority.

7. A method of controlling the movement of a fleet of autonomous guided vehicles according to claim 6, characterized in that each object loaded onto an autonomous guided vehicle is unloaded when said autonomous guided vehicle reaches the other destination.

8. Method for controlling the movement of a fleet of autonomous guided vehicles according to any one of the preceding claims, characterized in that said certain order of priority of the destinations to be reached corresponds to a distribution round of the postman.

9. Method for controlling the movement of a fleet of autonomous guided vehicles according to any one of the preceding claims, characterized in that the calculated travel times are calculated by considering an equivalent nominal speed for each autonomous guided vehicle moving on the traffic lane, the spatial position of each destination to be reached and the spatial position of each autonomous guided vehicle available on the traffic lane.

10. Method for controlling the movement of a fleet of autonomous guided vehicles according to any one of the preceding claims, characterized in that the central unit is configured to compare the calculated travel time of an autonomous guided vehicle to reach the first destination in the order of priority in a current assignment phase with the travel time of said autonomous guided vehicle to reach the first destination calculated in a previous assignment phase, and if the travel time calculated during the current assignment phase is not greater by at least a certain ratio with respect to the travel time calculated during the previous assignment phase, the central unit does not apply the current assignment phase and maintains the previous assignment phase.

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