Method and system for transporting items

Abstract

The invention relates to a method for controlling mobile robots in an intralogistics system (1) comprising a first working zone and a second working zone separated by an insertion section (Si), in which the mobile robots are arranged in ranks, and a distribution section (Sd), in which each robot (2) moves along a predetermined path, the method comprising the following steps: • identifying a robot at an entrance of the insertion section (Si); • assigning the robot a rank number and a route to follow through the distribution section (Sd); and • calculating an engagement time for the robot so that it follows its route while avoiding collisions in the distribution section. The invention also relates to a system implementing the method.

Description

METHOD AND SYSTEM FOR TRANSPORTING ARTICLES Technical field of the invention

[0001] The invention relates to the field of intralogistics and relates to a system and method for transporting objects using autonomous mobile robots, each capable of moving at least one item.

[0002] Such a transport system can have applications, for example, in a sorting facility or in an automatic storage system. State of the art

[0003] Autonomous mobile robots (AMRs) are commonly used to transport objects in an intralogistics facility. However, the large number of these robots circulating simultaneously in the circuit generates a risk of collisions between them. To avoid this, it is necessary to manage their movements taking this factor into account. The risk of collisions is generally limited by circuits without crossings or by implementing specific rules. However, these rules are not sufficient when the tasks to be performed require a high rate, for example to sort objects, to store them or to remove them from stock in order to prepare orders.

[0004] Known systems only address certain situations by reducing the speed. For example, if two robots meet at a crossing point, one of them must stop to allow the other to pass without collision. Repeated slowdowns and / or stops of this kind inevitably reduce the work rate of the robots and thus of the entire system.

[0005] The invention aims to offer an innovative solution to increase the fluidity of movement of autonomous mobile robots on an intralogistics circuit while avoiding traffic jams and collisions.

[0006] For this purpose, the invention relates to a computer-implemented method for controlling a set of autonomous mobile robots circulating in an intralogistics system comprising a first work area and a second work area separated by a transit area, the transit area comprising an introduction section in which the mobile robots coming from the first work area are organized in ranks, and a distribution section adjacent to the introduction section, in which each mobile robot coming from the introduction section circulates along a predetermined path to reach a destination in the second work area, the method comprising the following steps:receiving identification information of an autonomous mobile robot which arrives at an entrance of the introduction section,assigning said mobile robot a rank number in the introduction section and a route to follow in the distribution section,calculates a date of engagement of said mobile robot in the distribution section so that said autonomous mobile robot completes its journey in the distribution section without collision with the robots present in said section.,

[0007] The method according to the invention makes it possible to manage the movements of autonomous mobile robots (AMRs) in such a way as to avoid collisions by managing priorities upstream of the AMRs entering the distribution section. As a result, this guarantees smooth and safe traffic in the distribution section, since each robot can circulate in this section without having to stop.

[0008] Advantageously, the method may further comprise a step of placing the autonomous mobile robot on hold in the introduction section until the engagement date.

[0009] So we organize the AMRs in the introductory section according to their dates of engagement and ranks.

[0010] Advantageously, the movement of the autonomous mobile robots in the distribution section may be subject to a precedence rule according to which when two mobile robots must simultaneously take a crossing point or a common portion of their respective trajectories, then the mobile robot with a lower rank number has priority at said crossing point or on the common portion.

[0011] In this way, collision-free movements are guaranteed regardless of the topology of the AMRs' movement circuit.

[0012] The method may further comprise: a step of creating a time table presenting minimum time differences required between the respective engagement dates of any pair of mobile robots circulating simultaneously in the distribution section while respecting the precedence rule, and a step of calculating a engagement date of an autonomous mobile robot identified at the input of the introduction section with reference to said time table.

[0013] The advantage of this is that the creation of the delay table is done in one go, for example at the beginning, for a distribution section. Since this creation can be expensive in terms of computing time and memory resources, it may be advantageous to do it only once.

[0014] The calculation of a robot's engagement date is thus advantageously accelerated and compatible with real-time operation because it only consists of searching for the correct time in the table.

[0015] The creation of the time table can, for example, be done experimentally or by simulating possible routes.

[0016] It may include a step of creating a database comprising efficient routes for an autonomous mobile robot traveling the distribution section between each entrance and each exit, each route including a trajectory and a kinematic profile.

[0017] The route database contains, among other things, the fastest / most efficient routes for completing missions. This is advantageous in reducing the range of possible routes to those that provide a certain efficiency (throughput) and also simplifies the calculation of the time table.

[0018] Advantageously, the engagement date of a mobile robot of rank N is greater than the engagement date of each mobile robot of lower rank Nx by a delay between said mobile robot of rank N and said mobile robot of lower rank Nx indicated by the delay table, x being an integer greater than zero.

[0019] This ensures that an AMR engaged in the distribution section will not collide with any of the AMRs engaged before it in the distribution section.

[0020] Advantageously, the method may further comprise an optimization step, when there are several possible routes, a step in which the best route is selected which allows the robot of rank N to engage as soon as possible in the distribution section by applying a minimization function to the engagement dates calculated according to the routes.

[0021] This reduces the waiting time of each mobile robot and therefore improves traffic flow.

[0022] Advantageously, the method may comprise an additional step in which the rank numbers of a group of mobile robots present in the introduction section are modified by applying an optimization function so as to reduce the waiting time of at least some of the robots in this group.

[0023] This further reduces the waiting time of mobile robots and makes traffic flow more smoothly.

[0024] The invention also relates to a computer program comprising instructions which when executed cause it to execute the steps of the control method described above.

[0025] The invention also relates to a computer-readable medium comprising the computer program described above.

[0026] The invention also relates to an intralogistics transport system comprising:a plurality of autonomous mobile robots each capable of transporting an article,at least one first work zone and at least one second work zone connected to each other by at least one transit zone comprising an introduction section and a distribution section in which the autonomous mobile robots can circulate to move from one work zone to another, anda computer program as described above.

[0027] According to a first application of the above system, the first work area is an item storage area having a plurality of storage levels and means of ascent and descent connecting said levels and allowing the movement of mobile robots from and to said storage levels.

[0028] According to a second application of the system, the first work area is an item sorting area comprising sorting containers and at least one aisle allowing the movement of items to be sorted towards the containers by the mobile robots.

[0029] Definitions: within the framework of the invention we use the following definitions for certain elements described or mentioned.

[0030] Distribution section: it is a space, not necessarily consisting of a single connected area (it is generally a meeting of several disjoint areas), nor restricted to a horizontal surface, including for example elevators, having entry points and exit points, in which the robots enter through entry points and exit through exit points after having traveled predefined trajectories inside the section. These trajectories can cross thus creating a risk of collision between robots evolving on these trajectories in this section. At the entry points of the distribution section, we can find virtual or real barriers. Once engaged in the distribution section the robots no longer change trajectory or kinematic profile.

[0031] Introduction section: This is the set of injection lines upstream of the distribution section.

[0032] Trajectory: These are the predefined paths within the distribution section. Each trajectory connects an input to an output. An input and an output can be connected by several different trajectories.

[0033] Kinematic profile: Along the trajectories, the speed and acceleration instructions that the mobile robots must respect are defined. These instructions can vary along the trajectory to allow the robot to perform a particular maneuver such as turning or stopping. The choice of the kinematic profile is generally made in such a way as to minimize the time taken to travel the trajectory and to avoid waiting times.

[0034] Route: To execute the parcel transport process in the distribution section, a control device assigns a route to a robot, i.e. a particular trajectory of the distribution section associated with a kinematic profile with the aim of quickly reaching the destination (an exit).

[0035] Precedence rule: When two robots have to pass through the same position in the distribution section, for example in a sector of intersection of trajectories or an entrance or exit of the distribution section or a portion common to two trajectories, the robot with the lowest rank number must pass through this position first. The application of this rule guarantees the absence of collisions and congestion in the distribution section.

[0036] Delay table: This is a table of values ​​that depend on a list of routes (trajectories and kinematic profiles) of the distribution section. It allows to calculate the waiting time necessary for a robot at the entrance to the distribution section in order to allow it to respect the precedence rule without having to stop, outside the positions predefined by its kinematic profile, to avoid collisions. Brief description of the figures

[0037] Other features and advantages of the invention will appear in the description below in relation to the appended drawings, given as non-limiting examples, in which:

[0038] schematically represents an intralogistics system according to the invention with two work areas separated by a transit area;

[0039] schematically represents a first application of the system of the;

[0040] shows a second example of application of the system.

[0041] In the remainder of the description, elements having an identical structure or similar functions will be designated by the same references. Detailed description

[0042] The diagram shows schematically an example of an intralogistics system 1 according to the invention. The system 1 comprises a first work zone WZ1 and a second work zone WZ2 which are separated by a transit zone Zt.

[0043] The transit zone Zt comprises 2 parts, an introduction section Si and a distribution section Sd adjacent to Si. The introduction section Si comprises a plurality of inlets 5 and a plurality of outlets 8 which are also inlets of the distribution section Sd. The distribution section Sd also comprises a plurality of outlets 6.

[0044] The movements of the robots in this system are managed by a computer program.

[0045] Typically, a mobile robot 2 starting from the first work zone WZ1 arrives at an entrance 6 of the introduction section. If it then takes one of the tracks 4 connecting the entrances 5 to an exit 8, then it passes to the distribution section to follow a trajectory 3 which will take it to one of the exits 6 of said distribution section in order to reach the second work zone 2 WZ2.

[0046] Given the large number of AMR 2s in this system, it is necessary to manage their movements well to avoid collisions and / or significant waiting times, thus reducing the system's throughput.

[0047] To streamline the traffic of mobile robots 2 passing from the first zone WZ1 to the second zone WZ2, the system according to the invention is controlled by the computer program implementing the method according to the following method steps:receiving identification information from an autonomous mobile robot 2 which arrives at an entrance 5 of the introduction section Si,assigning to said mobile robot 2 a rank number in the introduction section Si and a route to follow in the distribution section,calculating a date of engagement of said mobile robot in the distribution section so that said mobile robot 2 completes its journey without collision in the distribution section.

[0048] Optionally, the method may further comprise a step of placing the mobile robot 2 on hold in the introduction section Si until the engagement date.

[0049] Optionally, the movement of the autonomous mobile robots in the distribution section may be subject to a precedence rule according to which when two mobile robots 2 should simultaneously take a crossing point or a common portion of their respective trajectories, then the mobile robot having a lower rank number has priority at said crossing point or on the common portion.

[0050] According to examples of the embodiments, the method may further comprise: a step of creating a time table presenting minimum time differences necessary between the engagement dates of mobile robots 2 circulating simultaneously in the distribution section Sd while respecting the precedence rule, and a step of calculating a engagement date of an autonomous mobile robot 2 identified at the input of the introduction section Si with reference to said time table.

[0051] The creation of the time table can, for example, be done experimentally or by simulating possible routes.

[0052] It may comprise a step of creating a database comprising efficient routes for an autonomous mobile robot 2 traveling the distribution section Sd between each entrance and each exit, each route including a trajectory and a kinematic profile.

[0053] Advantageously, the engagement date of a mobile robot of rank N is greater than the engagement date of each mobile robot of lower rank Nx by a delay between said mobile robot of rank N and said mobile robot of lower rank Nx indicated by the delay table, x being an integer greater than zero.

[0054] Advantageously, the method may further comprise an optimization step in which the best route is selected which allows the robot of rank N to engage as early as possible in the distribution section by applying a minimization function to the engagement dates calculated according to the routes.

[0055] To further reduce the waiting time of the AMRs, the method may comprise an additional step in which the rank numbers of a group of mobile robots present in the introduction section are modified by applying an optimization function so as to reduce the waiting time of at least some of the robots in this group. Different types of optimization functions may be applied, such as a perturbation function or a minimization.

[0056] Lamontre a first application in which the system 10 comprises a first work zone Wz1 which here is an automated stock composed of a set of article storage levels. In a known manner, the storage levels are connected by means of raising / lowering the AMRs 2 which are capable of moving articles 9 to be stored or removed from the stock. The second work zone Wz2 is in the example an order preparation station, however in other exemplary embodiments not shown the second zone may be any other work zone found in an automated storage system.

[0057] The two work zones Wz1 and Wz2 are separated by two transition zones Zt1 and Zt2 each comprising an introduction section (respectively Si1, Si2) and a distribution section (respectively Sd1, Sd2). Zt1 is arranged to allow the robots 2 to pass from the first zone Wz1 to the second zone Wz2. Zt2 is arranged to allow the passage from Wz2 to Wz1.

[0058] As known in Wz2, the robots transfer the items 9 taken out of stock to an order preparation station in which an operator 7 transfers them to order preparation containers.

[0059] Advantageously, according to the example the system can include a third work area.

[0060] Possible movements of robots between different zones are indicated by arrows.

[0061] Lamontre shows a second application in which the system 10' comprises a first work zone Wz1' which is an automated sorting zone composed of a set of sorting containers 11 separated by aisles 12 in which robots 2 can circulate, transporting articles to be sorted.

[0062] The second work zone Wz2' is in the example a loading station in which empty robots 2 are loaded with articles 6 to be sorted, however in other embodiments not shown the second zone can be any other work zone found in a sorting system.

[0063] The two work zones Wz1' and Wz2' are separated by two transit zones Zt1' and Zt2' each comprising an introduction section (respectively Si1', Si2') and a distribution section (respectively Sd1', Sd2'). Zt1' is arranged to allow passage of the robots 2 from the first zone Wz1' to the second zone Wz2'. Zt2' is arranged to allow passage from Wz2' to Wz1'.

[0064] To implement the control method described above, the systems described with reference to each of Figures 1 to 3, each comprise a computer program which comprises instructions which when executed lead to the execution of at least part of the steps described above.

[0065] Example of calculating the time table:

[0066] Calculating the time table associated with the distribution section can, according to an exemplary embodiment, be done as follows:

[0067] For any pair of routes of the distribution section, we choose a robot of rank to browse the distribution section following the route and a robot of rank , less priority ( ), to browse the distribution section following the route and we note the robot's engagement date And the robot's engagement date .

[0068] It is assumed that the priority robot enters the distribution section before the lower priority robot , the latter committing after a period , that is to say that and that .

[0069] The deadline between the robot engagement dates And in the distribution section on the routes And must be chosen so that the rule of precedence between the two robots is respected throughout the presence of the robots And in the distribution section, that is, the robot engage sufficiently after the robot in order to never get ahead of him and also avoid any collision.

[0070] If we note the duration of a route by a robot, how to set the deadline is to choose to wait for the priority robot leaves the distribution section before engaging the robot following, which amounts to having but this choice is clearly not optimal.

[0071] So, for any pair of routes of the distribution section, it is more advantageous to look for the smallest delay by calculation, simulation or experimentally. This calculation is done by a digital device at the time of establishing the list routes (trajectories and kinematic profiles) of the distribution section.

[0072] Example of commitment date calculation:

[0073] On the arrival of a new robot at an entry of the introductory section, there is already robots in the transit zone whose first are in the distribution section. The robots have the ranks respectively and respectively the routes . We will also note the effective dates of engagement for the first robots and planned engagement dates for the following robots and the earliest arrival dates at the entry barrier of each of the robots upon arrival at the entrance to the introductory section and the exit destinations of each robot crossing the transit zone.

[0074] The allocation to the new robot of a rank and an itinerary is done as follows: We calculate the rank of the new robot: Among the routes from the list of routes in the distribution section, we look for the one that allows the robot to engage as soon as possible in the distribution section: For each route possible for the robot allowing him to reach the exit desired, we calculate the engagement date: We identify the best route which allows the robot to engage as soon as possible in the distribution section: The expected engagement date for the robot East : .

Claims

A computer-implemented method for controlling a set of autonomous mobile robots (2) circulating in an intralogistics system (1; 10; 10') comprising a first work area (Wz1) and a second work area (Wz2) separated by a transit area (Zt), the transit area (Zt) comprising an introduction section (Si; Si1; Si2) in which the mobile robots (2) coming from the first work area (Zw1) are organized in ranks, and a distribution section (Sd; Sd1; Sd2) adjacent to the introduction section, in which each mobile robot (2) coming from the introduction section (Si; Si1; Si2) circulates along a predetermined trajectory to reach a destination in the second work area (Wz2), the method comprising the following steps:receiving identification information of an autonomous mobile robot (2) which presents itself at an entrance (5) of the introduction section (Si; Si1 ;Si2), assigning to said mobile robot (2) a rank number in the introduction section (Si) and a route to follow in the distribution section (Sd), calculating a date of engagement of said mobile robot (2) in the distribution section (Sd) so that said autonomous mobile robot completes its journey in the distribution section without collision with robots present in said section.; Method according to the preceding claim comprising a step of placing said autonomous mobile robot (2) on hold in the introduction section (Si; Si1; Si2) until the engagement date. Method according to one of the preceding claims in which the movement of the autonomous mobile robots (2) in the distribution section (Sd; Sd1; Sd2) is subject to a precedence rule according to which when two mobile robots (2) should simultaneously take a crossing point or a common portion of their respective trajectories, then the mobile robot (2) having a lower rank number has priority at said crossing point or on the common portion. Method according to the preceding claim, comprising: a step of creating a time table presenting minimum time differences necessary between the respective engagement dates of any pair of mobile robots (2) circulating simultaneously in the distribution section (Sd; Sd1; Sd2) while respecting the precedence rule, and a step of calculating a engagement date of an autonomous mobile robot (2) identified at the input of the introduction section (Si) with reference to said time table. Method according to the preceding claim in which the creation of the time table is done experimentally or by simulation of the possible routes. Method according to the preceding claim in which the creation of the time table comprises a step of creating a database comprising efficient routes for an autonomous mobile robot (2) traveling the distribution section between each entrance and each exit, each route including a trajectory and a kinematic profile. Method according to the preceding claim in which the engagement date of a mobile robot (2) of rank N is greater than the engagement date of each mobile robot (2) of lower rank Nx of the delay between said mobile robot of rank N and said mobile robot of lower rank Nx indicated by the delay table, x being an integer greater than zero. Method according to the preceding claim further comprising an optimization step in which when there are several possible routes, the best route is selected which allows the robot (2) of rank N to engage as soon as possible in the distribution section by applying a minimization function to the engagement dates calculated according to the routes. Method according to one of the preceding claims comprising an additional step in which the rank numbers of a group of mobile robots (2) present in the introduction section (Si) are modified by applying an optimization function so as to reduce the waiting time of at least some of the robots (2) of this group. Computer program comprising instructions which, when the program is executed by a computer, cause the latter to execute the steps of the control method according to one of the preceding claims. Computer-readable medium comprising a computer program according to the preceding claim. Intralogistics system comprising:a plurality of autonomous mobile robots (2) each capable of transporting an article,at least one first work zone (Wz1) and at least one second work zone (Wz2) connected to each other by at least one transit zone (Zt) comprising an introduction section (Si) and a distribution section (Sd) in which the autonomous mobile robots (2) can circulate to move from one work zone (Wz1, Wz2) to another, anda computer program according to claim 10. System (10) according to the preceding claim, wherein the first work area (Wz1) is an item storage area having a plurality of storage levels and raising and lowering means connecting said levels and allowing the movement of the mobile robots (2) from and to said storage levels. System (10') according to claim 12, wherein the first work area (Wz1') is an item sorting area comprising sorting containers (12) and at least one aisle (11) allowing the movement by the mobile robots (2) of items to be sorted towards the containers (12).

Images