IMPROVED STEERING OF GRIPPER HEAD OF A VACUUM GRIPPER OF A DIGITAL CUTTING SYSTEM

Abstract

The invention relates to a computer-implemented method for a cutting system, the cutting system at least comprising a digital cutter and a gripper for picking up cut parts.

Therein, the digital cutter is built for cutting a part of a sheet according to a cut design, the cut part having a specific pathway of its boundary line.

The gripper is built for picking up the cut part from the sheet, wherein the gripper comprises a gripper head and a movement apparatus. Thus, the gripper head is provided with a plurality of degrees of freedom of motorized movement including a variable heading angle (Ψ) and/or variable lateral position (x- and y-position) in a plane parallel to the sheet. The gripper head comprises a plurality of suction spots having known geometric arrangement, said arrangement of suction spots defining a mean grid spacing.

According to the invention, the method comprises carrying out an optimization algorithm for determining a gripping pose in which the cut part is to be gripped by the gripper head. Therein, the optimization algorithm being programmed for maximizing a number of cut-part-facing suction spots coming to lie on the cut part in the gripping pose, wherein the optimization algorithm optimizes over heading angle candidates (Ψ) for the gripping pose within a range extending consistently over at least 90° and/or lateral position candidates for the gripping pose within sub-mean-grid-spacing range

under exploitation of first input data consistently representing the complete specific pathway of the boundary line of the cut part and second input data relating to the known geometric arrangement.

The determined gripping pose will be provided as output data.

Claims

1. A computer-implemented method for a cutting system, the cutting system at least comprising a digital cutter for cutting a part of a sheet according to a cut design, the cut part having a specific pathway of its boundary line, and a gripper for picking up the cut part from the sheet, the gripper comprising a gripper head and a movement apparatus, in particular a gripper arm, such that the gripper head is provided with a plurality of degrees of freedom of motorized movement at least including a variable lateral position (x- and y-position) and/or a variable heading angle (Ψ) in a plane parallel to the sheet, the gripper head comprising a plurality of suction spots having known geometric arrangement, said arrangement of suction spots defining a mean grid spacing, characterised in that the method comprising carrying out an optimization algorithm for determining a gripping pose in which the cut part is to be gripped by the gripper head, the optimization algorithm being programmed for maximizing a number of cut-part-facing suction spots coming to lie on the cut part in the gripping pose, the optimization algorithm optimizing over at least one of heading angle candidates (Ψ) for the gripping pose within a range extending consistently over at least 90° and lateral position candidates for the gripping pose within sub-mean-grid-spacing range under exploitation of first input data consistently representing the complete specific pathway of the boundary line of the cut part and second input data relating to the known geometric arrangement, and providing the determined gripping pose as output data.

2. The method according to any one of the preceding claims, wherein the variable lateral position being a variable x- and a variable y-position of the gripper head in the plane parallel to the sheet, and the optimization algorithm optimizes over x-position candidates and y-position candidates for the gripping pose within sub-mean-grid-spacing range, in particular with at least millimeter resolution.

3. The method according to any one of the preceding claims, wherein the second input data relating to the known geometric arrangement includes knowledge about geometric positioning of each of the plurality of suction spots within the suction-spot-arrangement, in particular wherein the suction-spot-arrangement has matrix form with fix positioning of the suction spots forming a regular rectangular grid, having constant grid spacing in the directions of extend of the rectangular grid, the constant grid spacing thus forming the mean grid spacing.

4. The method according to any one of the preceding claims, wherein the optimization algorithm optimizes over heading angle candidates for the gripping pose within the range extending consistently over at least 90° with at least five degree resolution or higher, the range in particular extending consistently over at least 180°, more particular over 360°.

5. The method according to any one of the preceding claims, wherein the optimization algorithm optimizes consistently over the complete available range of motorized movement for the gripper head including all available of the plurality of degrees of freedom of motorized movement, with sub-mean-grid-spacing resolution.

6. The method according to any one of the preceding claims, wherein the known geometric arrangement forms an irregular pattern, with fix positioning of the suction spots in an irregularly distributed form, wherein an average spacing in-between each pair of directly neighboring suction spots forming the mean grid spacing.

7. The method according to any one of the preceding claims, wherein the plurality of suction spots having known individual physical properties including at least one of a spot diameter and a suction strength, and the optimization algorithm is programmed for—as further optimization objective or objectives— maximizing an overall suction effect caused on the cut part by cut-part-facing suction spots overlaying the cut part in the gripping pose, and/or maximizing a total area as the sum of cut-part-facing suction spot areas overlaying the cut part in the gripping pose, the optimization algorithm further exploiting third input data relating to the known individual physical properties of the suction spots.

8. The method according to any one of the preceding claims, wherein the optimization algorithm is programmed for—as further optimization objective— maximizing a number of cut-part-facing suction spots coming to lie on the cut part within a defined edge area close to the boundary line of the cut part in the gripping pose.

9. The method according to any one of the preceding claims, wherein two or more cut parts are to be cut by the digital cutter according to respective cut designs, each of the two or more cut parts having a specific pathway of its boundary line and a specific localization within the sheet, wherein the optimization algorithm being programmed for—as further optimization objective—maximizing a number of cut-part-facing suction spots coming to lie in sum on the two or more cut parts in the gripping pose, the optimization algorithm optimizing over heading angle candidates (Ψ) and/or lateral position candidates for the gripping pose further under exploitation of further input data consistently representing the complete specific pathway of the boundary line of each of the two or more cut parts and the specific localization within the sheet of each of the two or more cut parts.

10. The method according to any one of the preceding claims, wherein the gripper is built such that each of the plurality of suction spots is individually positionable to individual suction spot deflection-positions within the arrangement by an extend of maximal half of the mean grid spacing in at least one direction in a plane parallel to the sheet, such that the known geometric arrangement being variable, wherein the optimization algorithm further optimizes over individual suction spot deflection-position candidates for each of the plurality of suction spots for the gripping pose, further wherein, as the output data, the determined gripping pose including the optimized individual suction spot deflection-position for each of the plurality of suction spots being provided.

11. The method according to any one of the preceding claims, wherein the optimization algorithm is based on at least one of a graphical best fit approach, a linear programming approach, in particular the simplex algorithm, an iterative approach, in particular coordinate descent methods or the Newton's method, and a global convergence approach, and an heuristic approach, in particular a Hill climbing technique or the downhill simplex method.

12. The method according to any one of the preceding claims, wherein each suction spot of the plurality of suction spots is individually and selectively controllable and activatable, and wherein the automatic controller being further configured for providing indication about the cut-part-facing suction spots coming to lie on the cut part in the determined gripping pose as further output data.

13. An automatic controller for use as part of and within a cutting system, the cutting system at least comprising a digital cutter for cutting a part of a sheet according to a cut design and a gripper for picking up a cut part of the sheet, the gripper comprising a gripper head and a movement apparatus such that the gripper head is provided with a plurality of degrees of freedom of motorized movement including a variable heading angle and variable lateral position (as x- and y-position) in a plane parallel to the sheet, the gripper head comprising a plurality of suction spots having known geometric arrangement, said arrangement defining a mean grid spacing, characterised in that the automatic controller being configured to perform the method of any one of the preceding claims.

14. A computer program product comprising instructions which, when the program is executed by a computing unit, cause the computing unit to carry out the method of any one of claims 1 to 13.

15. A computer-readable data carrier having stored thereon the computer program product of claim 14, or a data carrier signal carrying the computer program product of claim 14.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] By way of example only, preferred embodiments of the invention will be described more fully hereinafter with reference to the accompanying figures, wherein:

[0052] FIG. 1 shows a generic cutter system comprising a digital cutter and a gripper in a first embodiment;

[0053] FIG. 2 shows the gripper head of FIG. 1 more closely;

[0054] FIG. 3 shows the gripper head of FIG. 1 more closely from a further perspective;

[0055] FIG. 4 shows a generic cutting system comprising a digital cutter and a gripper in a second embodiment;

[0056] FIG. 5 shows the embodiment of FIG. 4 with the gripper gripping a cut part;

[0057] FIG. 6 shows a generic cutting system comprising a digital cutter and a gripper in a third embodiment;

[0058] FIG. 7 shows the embodiment of FIG. 6 with the gripper gripping cut parts;

[0059] FIG. 8 shows a flat working surface from above and a not-optimized suction-spot-arrangement with respect to a cut part to be gripped;

[0060] FIG. 9 shows the embodiment of FIG. 8 with an optimized suction-spot-arrangement with respect to the cut part to be gripped;

[0061] FIG. 10 shows a flat working surface from above and a not-optimized suction-spot-arrangement with respect to a cut part to be gripped; and

[0062] FIG. 11 shows the embodiment of FIG. 10 with an optimized suction-spot-arrangement with respect to the cut part to be gripped.

DETAILED DESCRIPTION OF THE DRAWINGS

[0063] FIG. 1 shows a generic cutting system 1 comprising a digital cutter 2 (i.e. a cutting machine) and a gripper 3 in a first embodiment. As a flat-bed cutting machine 2, it has a table with a flat working surface 10, on which there is placed, by way of example, a sheet of material 14 with several objects 40 to be cut out from the sheet.

[0064] Above the working surface 10 there is arranged a working group 12 with a cutting tool 15, in particular a blade or knife. The working group 12 is displaceable two-dimensionally relative to the working surface 10 in a motorized manner so as to be able to approach any point of the working surface 10. To this end, the working group 12 is mounted movably in the X direction on a bridge/beam 13, which is in turn mounted movably in the Y direction on the table.

[0065] A camera unit (not shown) may be arranged above the working surface 10 so that images of the entire working surface 10 can be recorded.

[0066] In particular, the cutting machine 1 may also have a cutting tool 15 driven in oscillation and/or may be designed for cutting multi-walled composite plates, as described for example in EP 2 894 014 B1.

[0067] The cutting machine 1 additionally has an automatic controller or controlling unit 30. As shown here, the computing unit may be embodied as an external computer, which has a data connection to the machine 1, and/or may be integrated in the form of an internal control unit into the machine 1 itself.

[0068] The automatic controller or controlling unit 30 additionally controls the gripper 3 configured to grip cut part(s) 40 cut out from the sheet. The gripper 3 comprises a movement apparatus 62 configured for moving a gripper head 61 in 3D, which gripper head 61 is configured for gripping the cut part(s) 40. The automatic controller or controlling unit 30 may use images of the working surface 10 acquired by the camera unit (not shown) based on which it may control the gripper 3.

[0069] FIG. 2 shows the gripper head 61 of FIG. 1 more closely. The gripper head 61 is attached to the movement apparatus 62 shown in FIG. 1. Suction spots 63 are attached to the gripper head 61, wherein the suction spots 63 are configured to grip cut part(s) 40. Different arrangements of suction spots 63 are feasible, i.e. the three times five suction spots arrangement of FIG. 2 is purely exemplary.

[0070] FIG. 3 shows the gripper head 61 of FIG. 1 more closely from a further perspective. The geometric arrangement of suction spots 63 is clearly visible in FIG. 3.

[0071] FIG. 4 shows a generic cutting system 1 comprising a digital cutter 2 (i.e. a cutting machine) and a gripper 3 in a second embodiment. The embodiment shown in FIG. 4 is similar to the embodiment shown in FIG. 1 and differs from that embodiment in that the gripper 3 is changed. Specifically, both the movement apparatus 62 as well as the gripper head 61 are altered as compared to the embodiment of FIG. 1. As indicated by the letter LP above the gripper head 61, the gripper head 61 can be rotated by the movement apparatus 62 around an axis, for example the axis defined along the last rigid segment (last rotary joint) of the articulated robot arm movement apparatus 62.

[0072] FIG. 5 shows the embodiment of FIG. 4, with the gripper 3 gripping a cut part 40 cut out from the sheet 14.

[0073] FIG. 6 shows a generic cutting system 1 comprising a digital cutter 2 (i.e. a cutting machine) and a gripper 3 in a third embodiment. The embodiment shown in FIG. 6 is similar to the embodiments shown in FIGS. 1 and 4 and differs from these embodiments in that the gripper 3 is changed. Specifically, both the movement apparatus 62 as well as the gripper head 61 are altered as compared to the embodiments of FIGS. 1 and 4.

[0074] FIG. 7 shows the embodiment of FIG. 6, with the gripper 3 gripping cut parts 40 cut out from the sheet 14.

[0075] FIG. 8 shows a flat working surface 10 from above and a not-optimized suction-spot-arrangement 64 with respect to a cut part 40 to be gripped. Before gripping the cut part 40, the cutter working group 12 is moved aside. The suction-spot-arrangement 64 on the flat working surface 10 is determined by the orientation and position of the gripper head 61 resp. the suction spots 61—provided the gripper 3 comprises suction spots 63—with respect to the flat working surface 10. In the case of suction spots 63 being present and in particular for a flat cut part 40 lying on the flat working surface 10, the suction-spot-arrangement 64 corresponds to those suction spots 63 which reach the flat working surface 10 first in case of a (virtual) orthogonal projection of the suction spots 63 onto the flat working surface 10. If all suction spots 63 have a same distance to the flat working surface 10, the suction-spot-arrangement 64 corresponds to the positioning of the suction spots 63 on a gripper head 61.

[0076] In FIG. 8 as well as in FIGS. 9, 10 and 11 it is assumed that the gripper head 61 resp. the suction spots 63 are not inclined with respect to the flat working surface 10, i.e. e.g. all suction spots 63 have the same distance to the flat working surface 10. When gripping a cut part 40, the gripper head 61 resp. the suction spots 63 may in general, however, also be inclined with respect to the flat working surface 10.

[0077] The flat working surface 10 can be geometrically described using a coordinate system, e.g. a Cartesian coordinate system. An orientation and position of the suction-spot-arrangement 64 can be described in the coordinate system, wherein the position can e.g. be described using a center point of the suction-spot-arrangement 64, for example embodied as a symmetrical center point, and orientation can be described by a rotation angle in the coordinate system. When gripping the cut part 40, some of the suction spots 63 exert a suction force on the cut part 40 (shown in black in FIG. 8), while other suction spots 63 do not exert a suction force on the cut part 40 (shown in white in FIG. 8).

[0078] FIG. 9 differs from FIG. 8 in that the suction-spot-arrangement 64 is optimized according to the invention. The suction-spot-arrangement 64 is positioned and oriented in such a way that a maximum number of suction spots 63 exert a suction force on the cut part 40 which is assumed to lie flatly on the flat working surface 10. This way, the cut part 40 can be gripped in a more firm and stable way. In general, the gripper head may be positioned and oriented in such a way as to maximize the number of suction spots 63 or suction holes touching a cut part 40. Such a generalization may hold for cut parts to be gripped which potentially protrude from the flat working surface 10, i.e. for cut parts which are not flat.

[0079] FIGS. 10 and 11 show a similar situation as shown in FIGS. 8 and 9, that is a not-optimized and an optimized suction-spot-arrangement 64 with respect to a cut part 40. The suction-spot-arrangement 64 of FIG. 11 is optimized according to the invention as compared to FIG. 10, i.e. the suction-spot-arrangement 64 of FIG. 11 is positioned and oriented in such a way as to maximize the number of suction spots (or suction holes as shown in the gripper head of FIGS. 5 and 6, for example) which exert a suction force on the cut part 40 to be gripped.

[0080] Although the invention is illustrated above partly with reference to some preferred embodiments, it must be understood that numerous modifications and combinations of different features of the embodiments can be made. All of these modifications lie within the scope of the appended claims.

LIST OF REFERENCE NUMERALS

[0081] (1) cutting system [0082] (2) digital cutter [0083] (3) gripper [0084] (10) working surface, defining x- and y-direction [0085] (12) cutter head/cutter working group, moveable relative to bridge in x-direction [0086] (13) bridge/x-beam of the digital cutter, moveable relative to table in y-direction [0087] (14) sheet (sheet of material) [0088] (15) cutting tool (e.g. knife) [0089] (30) automatic controller (computer) [0090] (40) cut parts(s) [0091] (61) gripper head [0092] (62) movement apparatus [0093] (63) suction spots [0094] (64) suction-spot-arrangement