Method And a Device for Picking and Placing Items

Abstract

A method for picking and placing items includes the steps of: providing a picking conveyor transporting items to be picked; providing a placing conveyor to which the items are to be placed; and providing a plurality of robots configured to move the items from pick positions on the picking conveyor to place positions on the placing conveyor. For at least one of the plurality of robots there is defined an actual work area A.sub.ac that fulfils the condition A.sub.ac<A.sub.th−(A.sub.ol+A.sub.ex), wherein A.sub.th is a theoretical work area, A.sub.ol is an overlapping work area and A.sub.ex is an excessive work area of the respective robot. By limiting the actual work area A.sub.ac of the robots more than what is done conventionally, the total workload between the robots in pick and place systems may be balanced.

Claims

1. A method for picking and placing items, the method comprising the steps of: providing a picking conveyor transporting items to be picked; providing a placing conveyor to which the items are to be placed; and providing a plurality of robots configured to move the items from pick positions on the picking conveyor to place positions on the placing conveyor; wherein defining for at least one of the plurality of robots an actual work area A.sub.ac that fulfils the condition A.sub.ac<A.sub.th−(A.sub.ol+A.sub.ex), wherein A.sub.th is a theoretical work area, A.sub.ol is an overlapping work area and A.sub.ex is an excessive work area of the respective robot.

2. The method according to claim 1, wherein each actual work area A.sub.ac consists of a pick area A.sub.pick and a place area A.sub.place.

3. The method according to claim 2, further comprising the step of dynamically changing at least one of the shape, size and location of at least one pick area A.sub.pick or at least one place area A.sub.place.

4. The method according to claim 3, wherein the change in the shape, size and/or location is based on pick and place tasks carried out in the past.

5. The method according to claim 1, further comprising the step of defining for each of a plurality of robots an actual work area A.sub.ac that fulfils the condition A.sub.ac<A.sub.th−(A.sub.ol+A.sub.ex).

6. The method according to claim 1, further comprising the step of defining for at least one of the plurality of robots an actual work area A.sub.ac that fulfils the condition A.sub.ac≥A.sub.th−(A.sub.ol+A.sub.ex).

7. The method according to claim 6, further comprising the step of defining for the most downstream robot an actual work area A.sub.ac that fulfils the condition A.sub.ac≥A.sub.th−(A.sub.ol+A.sub.ex).

8. The method according to claim 1, further comprising the step of defining the pick area A.sub.pick of at least one robot to be further away from the placing conveyor than that of a more downstream robot.

9. The method according to claim 1, further comprising the step of defining the place area A.sub.place of at least one robot to be further away from the picking conveyor than that of a more downstream robot.

10. The method according to claim 1, further comprising the step of defining the pick area A.sub.pick and/or the place area A.sub.place of at least one robot to be smaller in size than that of a more downstream robot.

11. The method according to claim 1, further comprising the step of illustrating to an operator at least part of at least one actual work area A.sub.ac.

12. A pick and place system comprising: a picking conveyor transporting items to be picked, a placing conveyor to which the items are to be placed, and a plurality of robots configured to move the items from pick positions on the picking conveyor to place positions on the placing conveyor, wherein at least one of the plurality of robots has an actual work area A.sub.ac that fulfils the condition A.sub.ac<A.sub.th−(A.sub.ol+A.sub.ex), wherein A.sub.th is a theoretical work area, A.sub.ol is an overlapping work area and A.sub.ex is an excessive work area of the respective robot.

13. The pick and place system according to claim 12, further comprising a master controller configured to allocate to each robot an actual work area A.sub.ac consisting of a pick area A.sub.pick and a place area A.sub.place, and further configured to dynamically change at least one of the shape, size and location of at least one pick area A.sub.pick or one place area A.sub.place.

14. The method according to claim 1, wherein each of the plurality of robots is a parallel kinematics robot such as a delta robot.

15. The method according to claim 1, wherein at least one overlapping work area A.sub.ol fulfils the condition A.sub.ol>0.

16. The pick and place system according to claim 12, wherein each of the plurality of robots is a parallel kinematics robot such as a delta robot.

17. The pick and place system according to claim 12, wherein at least one overlapping work area A.sub.ol fulfils the condition A.sub.ol>0.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The invention will be explained in greater detail with reference to the accompanying drawings, wherein

[0029] FIG. 1a shows a conventional pick and place system,

[0030] FIG. 1b shows a theoretical work area A.sub.th of a robot,

[0031] FIG. 1c shows an overlapping work area A.sub.ol of a robot,

[0032] FIG. 1d shows an excessive work area A.sub.ex of a robot,

[0033] FIG. 1e shows actual work areas A.sub.ac of four robots, and

[0034] FIG. 2 shows a pick and place system according to one embodiment of the invention.

DETAILED DESCRIPTION

[0035] Referring to FIG. 2, a pick and place system 10 according to one embodiment of the present invention may comprise, in addition to the elements of the conventional pick and place system 10 of FIG. 1a, pick areas A.sub.pick 180 and place areas A.sub.place 190 which define within which areas the respective robots 50 are allowed to pick items 30 and place items 30, respectively, and which together define the actual work area A.sub.ac 170 of the respective robot 50. This can be expressed as

A.sub.ac=A.sub.pick+A.sub.place  (1),

wherein A.sub.ac is the actual work area 170, A.sub.pick is the pick area 180 and A.sub.place is the place area 190 of the respective robot 50.

[0036] According to the example of FIG. 2, the most upstream robot 50 is only allowed to pick items 30 at the part of the picking conveyor 20 furthest away from the placing conveyor 40, and to place items 30 at the part of the placing conveyor 40 furthest away from the picking conveyor 20. The actual work area A.sub.ac 170 of the most upstream robot 50 is thereby smaller in relative terms than in many conventional pick and place systems 10. This can be expressed as

A.sub.ac<A.sub.th−(A.sub.ol+A.sub.ex)  (2),

wherein A.sub.ac is the actual work area 170, A.sub.th is a theoretical work area 140, A.sub.ol is an overlapping work area 150 and A.sub.ex is an excessive work area 160 of the respective robot 50 (the right side of the equation representing an example of an actual work area A.sub.ac 170 in a conventional pick and place system 10). Pick areas A.sub.pick 180 and place areas A.sub.place 190 for the two middlemost robots 50 are defined in a corresponding way, while for the most downstream robot 50 the actual work area A.sub.ac 170 is defined in a conventional way.

[0037] The pick areas A.sub.pick 180 and the place areas A.sub.place 190 may have any appropriate shapes, sizes and locations as long as they fulfil the conditions of equations (1) and (2). The pick areas A.sub.pick 180 or the place areas A.sub.place 190 do not need to consist of single continuous areas i.e., each of them may be divided into a plurality of portions. The shapes, sizes and locations may change dynamically i.e., during the pick and place process. For example, the pick areas A.sub.pick 180 and the place areas A.sub.place 190 may be allocated by the master controller 120. Initially the actual work areas A.sub.ac 170 of all the robots 50 may be defined in a conventional way according to FIG. 1e. Each robot controller 110 may report to the master controller 120 the pick or place positions 60, 70 they have used, and the master controller 120 may contain one or more area algorithms 200 that calculate, based on the pick and place tasks carried out in the past, new pick areas A.sub.pick 180 and place areas A.sub.place 190 to better balance the workload. For example, if the most upstream robot 50 executes three times as many picks as the most downstream robot 50, the pick area A.sub.pick 180 of the most upstream robot 50 may be decreased to even out the number of picks between the two robots.

[0038] The pick and place system 10 may furthermore comprise visualizing means (not shown) to visually illustrate to an operator (not shown) some or all of the pick areas A.sub.pick 180 and the place areas A.sub.place 190. For example, the master controller 120 may comprise a digital twin of the pick and place system 10, and a display may show a real time illustration of the digital twin together with illustrations of the current pick areas A.sub.pick 180 and the current place areas A.sub.place 190. The operator could e.g., be able to see an illustration corresponding to FIG. 2. Alternatively, the visualizing means may comprise an augmented reality (AR) headset illustrating to the operator an environment of the real pick and place system 10 together with AR illustrations of the current pick areas A.sub.pick 180 and the current place areas A.sub.place 190.

[0039] The master controller 120 may furthermore contain one or more machine learning algorithms 210 designed to constantly improve the area algorithms 200 based on the earlier experience. As the actual work area A.sub.ac 170 may change dynamically, it can be appropriate that the master controller 120 sends all the pick positions 60 and all the place positions 70 to all robot controllers 110 even if the respective positions would lie outside of the actual work area A.sub.ac 170 of one or more robots 50.

[0040] It is not excluded that actual work areas A.sub.ac 170 of two or more neighboring robots 50 overlap a common overlapping work area A.sub.ol 150 of the robots 50, or that the actual work areas A.sub.ac 170 of two or more neighboring robots 50 overlap each other. Provided that prevention of collisions between the robots 50 is managed in an alternative way, it is fully possible to allow the robots 50 to operate within actual work areas A.sub.ac 170 that overlap each other.

[0041] It will be appreciated that there are numerous ways of defining whether an item 30 or a place position 70 shall be considered to be within a pick area A.sub.pick 180 or a place area A.sub.place 190 of a robot 50 or not. There is both a space aspect and a time aspect. For example, the question may be whether the whole item/place position 30, 70 or just a certain part of it shall be within, and at what moment the item/place position 30, 70 shall be within. One solution is to define that when a certain point of each item/place position 30, 70 which the tool center point (TCP) of the robot 50 needs to reach in order to pick or to place the item 30 is within the respective pick area A.sub.pick 180 or place area A.sub.place 190, the respective item/place position 30, 70 shall be considered to be within that area. Furthermore, as according to the present embodiment of the invention the actual work area A.sub.ac 170 is defined to be the sum of the pick area A.sub.pick 180 and the place area A.sub.place 190 (equation 1), it is logical to define that the decisive point in time is the instant of the respective pick or place action. It will be appreciated that there is a delay between a decision by the respective robot controller 110 to pick or place an item 30 and the instant at which the respective pick or place action takes place. According to the present embodiment of the invention the respective robot controller 110 calculates an estimation of the delay for each item/place position 30, 70, and only considers those items/place positions 30, 70 that are within the respective pick area A.sub.pick 180 or place area A.sub.place 190 at an estimated instant of the respective pick or place action.

[0042] Further elaborating the example of FIG. 2, the robot controller 110 of the most upstream robot 50 receives from the master controller 120 all the pick positions 60 and place positions 70 detected by the vision system 130. The robot controller 110 saves the positions in a list that it constantly updates, calculates estimated pick delays (delay in picking an item 30 from the current robot position) for all available pick positions 60, and furthermore calculates for each pick position 60 place delays (delay in placing an item 30 from the respective pick position 60) for all available place positions 70. The robot controller 110 then takes a decision to pick one of the items 30 based on the robots 50 current pick area A.sub.pick 180 together with an algorithm governing the picking order, excluding all the pick positions 60 considered to be outside of the current pick area A.sub.pick 180. As soon as the item 30 is picked, the robot controller 110 takes a decision to place it in one of the place positions 70 based on the robots 50 current place area A.sub.place 190 together with an algorithm governing the placing order, excluding all the place positions 70 considered to be outside of the current place area A.sub.place 190. As soon as an item 30 is picked or placed the respective robot controller 110 removes the respective pick or place position 60, 70 from its list. The same applies when an item 30 or a place position 70 passes the respective theoretical work area A.sub.th 140 of a robot 50.

[0043] It may be advantageous to let the more upstream robots 50 to make the largest movements i.e., to define the pick areas A.sub.pick 180 to be further away from the placing conveyor 40 and/or the place areas A.sub.place 190 to be further away from the picking conveyor 20 than those of more downstream robots 50. It may furthermore be advantageous to let the pick areas A.sub.pick 180 and/or the place areas A.sub.place 190 of more upstream robots 50 to be smaller in size than those of more downstream robots 50. It may furthermore be advantageous to define the pick areas A.sub.pick 180 to overlap in the first direction 90 and/or to define the place areas A.sub.place 190 to overlap in the second direction 100. In case of ambiguity, locations of pick areas A.sub.pick 180 and place areas A.sub.place 190 are to be defined by their assumed mass centers. It may furthermore be advantageous not to limit the actual work area Aar 170 of the most downstream robot 50 more than what follows from the reasons mentioned in the background section of this disclosure i.e. the actual work area A.sub.ac 170 of the most downstream robot 50 may advantageously be defined in a conventional way whereby it is configured to execute as many pick and place tasks as possible.

[0044] The invention is not limited to the embodiments shown above, but the person skilled in the art may modify them in a plurality of ways within the scope of the invention as defined by the claims.