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 travel path in order to reach destinations, the method comprising successive phases of assigning autonomous guided vehicles to the destinations, characterised in that each assignment phase is carried out by a central unit and comprises the steps of: - updating (100) a list of destinations by order of priority and a list of autonomous guided vehicles available to travel to the destinations; - calculating (200), for each destination, a travel time for each vehicle to travel to the destination; and - assigning (300), from among the available autonomous guided vehicles not yet assigned to a destination during the current assignment phase, for each destination to be reached in the order of priority, an autonomous guided vehicle which has the shortest calculated travel time for reaching the destination.

Description

Method for dynamic reassignment of autonomous guided vehicles to destinations

[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.

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

[0003] The movement of autonomous guided vehicles is controlled by a central unit configured to assign each vehicle to a destination where an object to be collected or deposited is located, while taking into account the availability of 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 journey time for a vehicle to reach its destination according to the order of priority may be different from the journey time actually spent 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 vehicles at a common traffic point, the order being maintained after this reordering by then forcing traffic to flow in single file.

[0007] While this previous solution works, it has multiple drawbacks, particularly in terms of performance. Indeed, once a vehicle has reached its destination, it can only move on to the next one if it is the first vehicle expected in the priority order. 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 object handling process, especially when the highest priority vehicle experiences traffic problems.

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

[0009] To this end, the subject of the invention is 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, 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.

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

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

[0015] - repeat the assignment phases cyclically;

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

[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 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;

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

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

[0022] - 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;

[0023] - 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. 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] 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 the, 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 known as AGVs, are mobile robots designed to navigate a traffic lane, such as dedicated AGV aisles in a logistics center. AGVs can also perform handling tasks, such as retrieving or depositing 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 able to dynamically reassign the VGAs to the different destinations. By dynamic reassignment we understand 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 in the fleet. An available VGA is understood to mean, 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 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 at a step 400 the movement of all the assigned AGVs to the destinations.

[0039] By way of non-limiting example, the assignment 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 could be the same assignment as the previous assignment or another assignment.

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

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

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

[0044] An example of the sequence of an allocation phase followed by a phase of moving the VGAs of the method according to the invention shown on the are described below.

[0045] In step 100, the central unit updates the list of destinations to be reached comprising three destinations from D1 to D3 to be reached according to a certain order of priority (D1 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.D A1= time for VGA01 to reach D1D B1 = time for VGA02 to reach D1

[0048] andD A2 = time for VG01 to reach D2D B2 = 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 D1 considered as the highest priority destination If D B1 < D A1 then send VGA02 to D1VGA02 is no longer availableVGA01 is availableFor D2 considered as highest priority destination after D1D A2 = time for VG01 to reach D2No other VGASend VGA01 to D2

[0050] In step 400, the central unit commands 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 D1 considered as the highest priority destinationD A1 = time for VGA01 to reach D1D B1 = time for VGA02 to reach D1D C1 = time for VGA03 to reach D1Min(D A1 , D B1 , D C1 ) = D B1 VGA02 remains assigned to D1For D2 considered as the highest priority destination after D1D A2 = time for VGA01 to reach D2D C2 = time for VGA03 to reach D2Min(D A2 , D C2 ) = D A2VGA01 remains assigned to D2For D3 considered as the highest priority destination after D2D C3 = time for VGA03 to reach D3No other VGAVGA03 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 D1D A2 = time for VGA01 to reach D2D C2 = time for VGA03 to reach D2Min(D A2 , D C2 ) = D C2 VGA03 is assigned to D2For D3 considered as the highest priority destination after D2D A3= time for VGA01 to reach D3No other VGAVGA01 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 CPU determines whether all destinations are reached by the VGAs.

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

[0058] If so, the central unit commands at step 600 the movement of all the VGAs to carry out other missions.

Claims

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., 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. 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. 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. 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. 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, when all the autonomous guided vehicles have reached their destination, control the movement of the autonomous guided vehicles to another destination to be reached one after the other in order of priority. Method for 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. 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. 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. 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 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.

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