METHOD AND SYSTEM FOR TRANSPORTING ARTICLES

Abstract

The invention relates to a method for controlling mobile robots (2) in an intralogistics system (1) comprising a first and a second working area (Wz1, Wz2) separated by an introduction section (Si) in which the mobile robots (2) are organized in ranks, and a distribution section (Sd) in which each robot (2) circulates according to a predetermined trajectory, the method comprising the following steps: identifying a robot (2) at an entrance (5) of the introduction section (Si), assigning to said robot (2) a rank number and a route to follow in the distribution section (Sd), and calculating an engagement date of said robot (2) so that it completes its path without collision in the distribution section. The invention also relates to a system implementing the method. Figure for abstract: Figure 1.

Description

Title of the invention: 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 installation 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 at the same time 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 risks of collisions are generally limited with circuits without crossings or by implementing specific rules. However, these rules are not sufficient when the tasks to be performed require a high rate, either to sort the objects, to store them or to remove them from stock to prepare orders.

[0004] Known systems only address certain situations by influencing the rate downwards. For example, in the case where two robots meet at a crossing point, it is necessary for one of the two to stop to allow the other to pass without collision. The repetition of such slowdowns and / or stops inevitably reduces the work rate of the robots and therefore of the entire installation.

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

[0006] To this end, 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 trajectory to reach a destination in the

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[0014] second working area, the method comprising the following steps: - receiving identification information from an autonomous mobile robot that presents itself at an entrance to the introductory section, - allocation to said mobile robot of 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. 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 secure traffic in the distribution section. Advantageously, the method may further comprise a step of placing the autonomous mobile robot on hold in the introduction section until the engagement date. So we organize the AMRs in the introductory section according to their dates of engagement and ranks. 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 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. In this way, collision-free movements are guaranteed regardless of the topology of the AMRs' movement circuit. The method may further comprise: - a step of creating a time table presenting the minimum time gaps required between the respective commitment dates of any pair of mobile robots circulating simultaneously in the distribution section while respecting the precedence rule, and - a step of calculating a date of engagement of an autonomous mobile robot identified at the input of the introductory section with reference to said time table. 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 costly in terms of computing time and memory resources, it is advantageous to do it only once. The calculation of the engagement date of a robot is thus advantageously accelerated and compatible with real-time operation because it only consists of searching for the correct delay in the table.

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

[0016] It may comprise 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, in particular, the fastest / most efficient routes for carrying out missions. It is advantageous to thus reduce the range of possible routes to those which 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 have a collision with any of the AMRs engaged before it in the distribution section.

[0020] Advantageously, the method can 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 as a function of the routes.

[0021] This makes it possible to reduce the waiting time of each mobile robot and consequently to streamline traffic.

[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 further streamlines traffic.

[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, and - a 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 raising and lowering means 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 zone (it is generally a meeting of several disjoint zones), 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, virtual or real barriers can be found. Once engaged in the distribution section the robots no longer change either 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 are defined the speed and acceleration instructions that the mobile robots must respect, 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.

[0034] Route: To execute the parcel transport process in the distribution section, a control device assigns a route to a robot, i.e. a tra particular jectory of the distribution section associated with a kinematic profile in order to quickly reach 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 collision 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 of 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] [Fig.l] [Fig.l] schematically represents an intralogistics system according to the invention with two work zones separated by a transit zone;

[0039] [Fig.2] [Fig.2] schematically represents a first application of the system of [Fig.l];

[0040] [Fig.3] [Fig.3] shows a second example of application of the system of [Fig.l]

[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] [Fig.l] schematically shows 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 present at an entrance 6 of the introduction section If then it 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 AMRs 2 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: - reception of identification information of an autonomous mobile robot 2 which presents itself 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 can further comprise: - a step of creating a time table presenting minimum time differences necessary between the dates of engagement of mobile robots 2 circulating simultaneously in the distribution section Sd while respecting the precedence rule, and - a step of calculating a date of engagement of an autonomous mobile robot 2 identified at the input of the introductory section If with reference to said time table.

[0051] The creation of the time table can, for example, be done experimentally or by simulation of 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 tra- jectory 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 soon as possible in the distribution section by applying a minimization function to the engagement dates calculated as a function of 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] [Fig.2] shows a first application in which the system 10 comprises a first work area 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 area Wz2 is in the example an order preparation station, however in other exemplary embodiments not shown the second area may be any other work area found in an automated storage system.

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

[0058] In a known manner in Wz2 the robots transfer the articles 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 comprise a third work zone.

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

[0061] [Fig.3] shows a second application in which the system 10' comprises a first work zone Wzl' which is an automated sorting zone composed of a set of sorting containers 11 separated by aisles 12 in which can circulate robots 2 carrying items 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 Wzl' and Wz2' are separated by two transit zones Ztl' and Zt2' each comprising an introduction section (respectively Sil', Si2') and a distribution section (respectively Sdl', Sd2'). Ztl' is arranged to allow passage of the robots 2 from the first zone Wzl' to the second zone Wz2'. Zt2' is arranged to allow passage from Wz2' to Wzl'.

[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] The calculation of the time table A = [A(I, J)]feI feI associated with the section of dis according to an example of implementation, the contribution can be made as follows:

[0067] For any pair of routes in the distribution section, a robot R; of rank ri is chosen to travel the distribution section following route I] and a robot R2 of rank r2, with less priority (^ 5 L), to travel the distribution section following route I2 and we note tj the engagement date of robot R, and L the engagement date of robot R2.

[0068] It is assumed that the priority robot R enters the distribution section before the lower priority robot R2, the latter entering after a delay A(Ij, I2), i.e. t1 < t2 and t2 = tj + A(Ib I9).

[0069] The delay A(I],I9) between the engagement dates of the robots R] and R2 in the distribution section on the routes Ij and I2 must be chosen so that the precedence rule between the two robots is respected throughout the presence of the robots Ri and R2 in the distribution section, that is to say that the robot R2 engages sufficiently after the robot R] so as never to get ahead of it and also to avoid any collision.

[0070] If we note d(I) the duration of the journey of a route I by a robot, the way to fix the delay A(I], I2) is to choose to wait for the priority robot R, to leave the distribution section before engaging the next robot R2, which amounts to having A(Ij, I2) — d(I( ) but this choice is clearly not optimal.

[0071] Thus, for any pair (Ij, I9) of routes in the distribution section, it is more advantageous to search for the smallest delay A(I], I2) by calculation, simulation or experiment. mentally. This calculation is done by a digital device at the time of establishing the Ip list of routes (trajectories and kinematic profiles) of the distribution section.

[0072] Example of calculation of commitment date:

[0073] On arrival of a new robot R^ at an entrance of the introduction section, there are already N - 1 robots Rj, • • • » Rn-i in the transit zone of which the first M Rj, R2, ..., Ry are in the distribution section. The robots Rj, R^ • ■ •, Rn-1 have respectively the ranks 11' r2' • • • ' rN-i and respectively the routes Ij, I2, • • •, In-1 . We will also note tj, , tM the effective dates of engagement for the first M robots and Im+1' Wr2' • • • ' planned engagement dates for the following robots and Th T2, ..., Tn the earliest arrival dates at the entry barrier of each of the N robots upon arrival at the entrance to the introduction section and Sk S2, ..., SN the exit destinations of each robot crossing the transit zone.

[0074] The assignment to the new robot R^ of a rank 1n and a route In is done as follows: 1. We calculate the rank of the new robot: rN = max(l\ ) + 1 k <N 2. Among the routes J in the list of routes of the distribution section, we search for the one which allows the earliest engagement of the robot R^ in the distribution section: a. For each possible route J for the robot Rn allowing it to arrive at the desired exit, we calculate the engagement date: f(J) =m <Mtk + A(Ik,J)) k<N b. We identify the best route In which allows the robot R^ to enter the distribution section as soon as possible: l1n c. The expected engagement date for robot R^ is: tN = t(IN) =max(tk+A(Ik,IN)).

Claims

Claims

1. 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 (Wzl) and a second work area (Wz2) separated by a transit area (Zt), the transit area (Zt) comprising an introduction section (Si; Sil; Si2) in which the mobile robots (2) coming from the first work area (Zwl) are organized in ranks, and a distribution section (Sd; Sdl; Sd2) adjacent to the introduction section, in which each mobile robot (2) coming from the introduction section (Si; Sil; 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 arrives at an entrance (5) of the section introductory (If; Sil;Si2), - allocation to said mobile robot (2) of a rank number in the introduction section (Si) and a route to follow in the distribution section (Sd), - calculation of 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.;

2. Method according to the preceding claim comprising a step of placing said autonomous mobile robot (2) on hold in the introduction section (Si; Sil; Si2) until the engagement date.

3. Method according to one of the preceding claims in which the movement of the autonomous mobile robots (2) in the distribution section (Sd; Sdl; 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.

4. 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; Sdl; 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.

5. Method according to the preceding claim in which the creation of the time table is done experimentally or by simulation of the possible routes.

6. 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.

7. 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.

8. 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.

9. 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.

10. A computer program comprising instructions which, when the program is executed by a computer, causing the latter to execute the steps of the control method according to one of the preceding claims.

11. A computer-readable medium comprising a computer program according to the preceding claim.

12. Intralogistics system comprising: - a plurality of autonomous mobile robots (2) each capable of transporting an article, - at least one first work zone (Wzl) 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 (Wzl, Wz2) to another, and - a computer program according to claim 10.

13. System (10) according to the preceding claim, in which the first work area (Wzl) is an article 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.

14. System (10') according to claim 12, in which the first work area (Wzl') 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).

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