POSITIONING APPARATUS AND METHOD FOR POSITIONING A FLEXIBLE, FLAT WORKPIECE

Abstract

A positioning device for positioning a limp flat workpiece has a provisioning area for providing the flat workpiece to be positioned and a camera for generating a camera image of the flat workpiece to be positioned. Furthermore, the positioning device comprises a first manipulator having a first gripper, a second gripper and a third gripper. The second gripper and the third gripper are configured to take over at least a portion of the limp flat workpiece from the first gripper. In addition, a method of positioning a limp flat workpiece is presented.

Claims

1. A positioning device for positioning a limp flat workpiece, comprising: a provisioning area for providing the limp flat workpiece to be positioned; a camera which is arranged and configured to generate a camera image of the limp flat workpiece which is positioned and which is located in the provisioning area; a first manipulator which carries a first gripper configured to grip at least a portion of the limp flat workpiece from the provisioning area; a second gripper; and a third gripper, wherein the second gripper and the third gripper are each configured to take over at least a portion of the limp flat workpiece from the first gripper, and wherein: the second gripper and the third gripper are drivingly coupled to a linear drive unit, wherein the second gripper and the third gripper are each movable along the linear drive unit, or the second gripper is carried by a second manipulator and the third gripper is carried by a third manipulator.

2. The positioning device according to claim 1, wherein the linear drive unit together with the second gripper and the third gripper is mounted in the positioning device so as to be rotatable about an axis extending parallel to its longitudinal extent.

3. The positioning device according to claim 1, wherein the provisioning area comprises a manipulation surface for providing the limp flat workpiece.

4. The positioning device according to claim 1, wherein the provisioning area comprises a provisioning container in which one or more limp flat workpieces can be provided.

5. The positioning device according to claim 3, wherein a provisioning manipulator has a provisioning gripper, wherein the provisioning manipulator is configured to transfer flat workpieces provided by a provisioning container onto the manipulation surface.

6. The positioning device according to claim 1, wherein the first gripper comprises two gripper jaw pairs, wherein a free space is provided between the two gripper jaw pairs.

7. The positioning device according to claim 6, wherein the free space is dimensioned such that it can receive at least a portion of the second gripper and at least a portion of the third gripper when the second gripper and the third gripper are arranged at a minimum distance and/or in their initial positions.

8. The positioning device according to claim 1, wherein a control unit is provided comprising at least one of: a first machine learning module which is adapted to identify a grippable edge of the limp flat workpiece on a basis of the camera image, generated by the camera, of the flat workpiece, or a second machine learning module which is adapted to determine a gripping point for the first gripper on the basis of the camera image, generated by the camera, of the limp flat workpiece, or a third machine learning module which is adapted to identify a type of the limp flat workpiece on the basis of the camera image, generated by the camera, of the limp flat workpiece.

9. A method of positioning a limp flat workpiece using a positioning device, the method comprising the steps of: a) providing the flat workpiece in a provisioning area, the flat workpiece assuming a random state; b) gripping an edge of the flat workpiece using a first gripper; c) transferring the flat workpiece from the first gripper to a second gripper and a third gripper wherein the second gripper and the third gripper grip the edge of the flat workpiece; and d) depositing the flat workpiece in a flat condition using the second gripper and the third gripper.

10. The method according to claim 9, wherein a camera image which shows the flat workpiece located in the provisioning area is generated by a camera; the camera image is transmitted to a first machine learning module of the control unit; and the first machine learning module identifies a position of the edge of the flat workpiece based on the camera image.

11. The method according to claim 10, wherein for identifying the position of the edge, the camera image is subdivided into a plurality of partial images by the control unit, and characteristic image features are extracted by the first machine learning module of the control unit for each partial image and, based on the characteristic image features, for each partial image a probability is established with which it shows the edge of the flat workpiece, wherein, for each partial image, probabilities are established with which it belongs to one of a plurality of predefined categories.

12. The method according to claim 10, wherein the camera image or at least a partial image of the camera image is transmitted to a second machine learning module of the control unit, and the second machine learning module identifies a gripping point for the first gripper on a basis of the camera image or the partial image of the camera image.

13. The method according to claim 9, wherein for transferring the flat workpiece from the first gripper to the second gripper and the third gripper, the second gripper and the third gripper substantially simultaneously grip a portion of the edge located in a free space between two gripper jaw pairs of the first gripper.

14. The method according to claim 9, wherein after transferring the flat workpiece to the second gripper and the third gripper, the flat workpiece is held using the second gripper and the third gripper is moved away from the second gripper until the third gripper has reached a first corner of the flat workpiece, or after transferring the flat workpiece to the second gripper and the third gripper, the flat workpiece is held using the third gripper and the second gripper is moved away from the third gripper until the second gripper has reached a second corner of the flat workpiece, or after transferring the flat workpiece to the second gripper and the third gripper, the second gripper and the third gripper are simultaneously moved away from each other until the third gripper has reached a first corner of the flat workpiece and the second gripper has reached a second corner of the flat workpiece.

15. The method according to claim 14, wherein for moving the second gripper away from the third gripper and/or for moving the third gripper away from the second gripper, a gripping force of the second gripper and/or of the third gripper is reduced compared with a predefined initial gripping state, or for moving the second gripper away from the third gripper and/or for moving the third gripper away from the second gripper, the second gripper and/or the third gripper is/are opened by a specified amount.

16. The positioning device according to claim 2, wherein the provisioning area comprises a manipulation surface for providing the limp flat workpiece.

17. The positioning device according to claim 4, wherein a provisioning manipulator has a provisioning gripper, wherein the provisioning manipulator is configured to transfer flat workpieces provided by the provisioning container onto the manipulation surface.

18. The method according to claim 11, wherein the camera image or at least a partial image of the camera image is transmitted to a second machine learning module of the control unit, and the second machine learning module identifies a gripping point for the first gripper on a basis of the camera image or the partial image of the camera image.

19. The method according to claim 10, wherein for transferring the flat workpiece from the first gripper to the second gripper and the third gripper, the second gripper and the third gripper substantially simultaneously grip a portion of the edge located in a free space between two gripper jaw pairs of the first gripper.

20. The method according to claim 10, wherein after transferring the flat workpiece to the second gripper and the third gripper, the flat workpiece is held using the second gripper and the third gripper is moved away from the second gripper until the third gripper has reached a first corner of the flat workpiece, or after transferring the flat workpiece to the second gripper and the third gripper, the flat workpiece is held using the third gripper and the second gripper is moved away from the third gripper until the second gripper has reached a second corner of the flat workpiece, or after transferring the flat workpiece to the second gripper and the third gripper, the second gripper and the third gripper are simultaneously moved away from each other until the third gripper has reached a first corner of the flat workpiece and the second gripper has reached a second corner of the flat workpiece.

Description

[0074] The invention will be discussed below with reference to various exemplary embodiments which are shown in the accompanying drawings, in which:

[0075] FIG. 1 shows a positioning device according to the invention in accordance with a first embodiment, by means of which a method according to the invention for positioning a limp flat workpiece can be carried out, as well as a further processing machine and a flat workpiece to be positioned;

[0076] FIG. 2 shows a first gripper of the positioning device from FIG. 1 in an isolated, perspective illustration;

[0077] FIG. 3 shows the first gripper from FIG. 2 in a top view;

[0078] FIG. 4 shows the first gripper from FIG. 2 in a side view;

[0079] FIG. 5 shows the first gripper from FIGS. 2 to 4 in a side view corresponding to FIG. 4, with the first gripper being open;

[0080] FIG. 6 shows a handling assembly of the positioning device from FIG. 1, which comprises a second gripper and a third gripper, in an isolated representation, with the flat workpiece being gripped by the second gripper and the third gripper;

[0081] FIG. 7 shows the handling assembly from FIG. 6, with the second gripper and the third gripper each assuming a different position and further with the flat workpiece being gripped by the second gripper and the third gripper;

[0082] FIG. 8 shows the handling assembly and the flat workpiece from FIG. 7 in a perspective illustration;

[0083] FIG. 9 shows an alternative to the handling assembly from FIGS. 6 to 8, with the flat piece being gripped again;

[0084] FIG. 10 shows a positioning device according to the invention in accordance with a second embodiment, by means of which a method according to the invention for positioning a limp flat workpiece can be carried out, as well as a further processing machine and a flat workpiece to be positioned;

[0085] FIG. 11 shows a positioning device according to the invention in accordance with a third embodiment, by means of which a method according to the invention for positioning a limp flat workpiece can be carried out, as well as a further processing machine and two flat workpieces to be positioned;

[0086] FIG. 12 shows a schematic diagram for illustrating the invention; and

[0087] FIG. 13 shows a further schematic diagram for illustrating the invention.

[0088] FIG. 1 shows a positioning device 10 for positioning a limp flat workpiece 12.

[0089] In the embodiment shown, the positioning device 10 is configured to place the limp flat workpiece 12, which is provided in a random state, into a further processing machine 14 in a flat spread-out state. More specifically, the limp flat workpiece 12 is placed in a flat spread-out state onto the belt conveyor 16 comprising a plurality of conveyor belts.

[0090] The limp flat workpiece 12 is, for example, a towel.

[0091] The positioning device 10 comprises a provisioning area 18 which, in the first embodiment according to FIG. 1, comprises a manipulation surface 20 for providing the limp flat workpiece 12.

[0092] Furthermore, the positioning device 10 includes a camera 22 which is positioned within the positioning device 10 and adapted to generate a camera image B of the flat workpiece 12 provided in the provisioning area 18, more specifically on the manipulation surface 20.

[0093] In the present case, the camera 22 is fastened in an area of a frame 24 of the positioning device 10 which is located above the manipulation surface 20 in the vertical direction. The manipulation surface 20 is fully within the detection field of the camera 22.

[0094] The positioning device 10 further comprises a first manipulator 26, which in the embodiment shown is in the form of an industrial robot.

[0095] The first manipulator 26 carries a first gripper 28.

[0096] The latter is configured to grip a portion of the limp flat workpiece 12 that is located in the provisioning area 18.

[0097] The first gripper 28 is illustrated in detail in FIGS. 2 to 5.

[0098] It comprises a first gripper jaw pair 30, which includes a lower gripper jaw 32 and an upper gripper jaw 34.

[0099] Furthermore, the first gripper 28 is equipped with a second gripper jaw pair 36.

[0100] The latter also comprises a lower gripper jaw 38 and an upper gripper jaw 40.

[0101] It should be appreciated here that, due to the fact that the gripper 28 is fastened to the first manipulator 26, it can assume almost any desired orientations in space. Thus, the indications “upper” and “lower” merely serve to simplify the designation of the gripper jaws 32, 34, 38, 40 and essentially refer to the orientation of the first gripper 28 as illustrated in FIG. 2.

[0102] The lower gripper jaws 32, 38 are rigidly connected to each other.

[0103] Likewise, the upper gripper jaws 34, 40 are rigidly connected to each other.

[0104] The first gripper 28 further comprises an actuator 42 configured to selectively lift the upper gripper jaws 34, 40 off the respectively associated lower gripper jaws 32, 38 or to move the upper gripper jaws 34, 40 closer to the lower gripper jaws 32, 38 (see in particular FIGS. 4 and 5 for comparison).

[0105] Furthermore, a free space 44 is provided between the gripper jaw pairs 30, 36 (see in particular FIG. 3). The gripper jaw pairs 30, 36 thus have a distance d from each other.

[0106] Moreover, for easy pick-up and retaining of the flat workpiece 12, the respective lower gripper jaws 32, 38 are each equipped with a curved retaining surface 46, 48 in the area of their tip.

[0107] The upper gripper jaws 34, 40 each include a holding tip 50, 52 for pressing the flat workpiece 12 against the lower gripper jaws 32, 38. In particular, the flat workpiece 12 is pressed against the retaining surfaces 46, 48.

[0108] The positioning device 10 further comprises a handling assembly 54.

[0109] The handling assembly 54 is shown in detail in FIGS. 6 to 8.

[0110] It comprises a linear drive unit 56 as well as a second gripper 58 and a third gripper 60.

[0111] The second gripper 58 and the third gripper 60 are drivingly coupled to the linear drive unit 56 here so that the second gripper 58 and the third gripper 60 are each movable along a direction of movement L of the linear drive unit 56.

[0112] The driving coupling of the grippers 58, 60 to the linear drive unit 56 is designed in such a way here that the second gripper 58 and the third gripper 60 can only be moved interdependently. In other words, the third gripper 60 is moved when the second gripper 58 is moved, and vice versa.

[0113] Furthermore, the second gripper 58 and the third gripper 60 are each adapted to take over a portion of the limp flat workpiece 12 from the first gripper 28.

[0114] For this purpose, the second gripper 58 includes a gripper jaw pair that comprises a first gripper jaw 62 and a second gripper jaw 64.

[0115] The first gripper jaw 62 and the second gripper jaw 64 can be moved relative to each other by means of an actuator 65 in order to selectively clamp the flat workpiece 12 between them or to release it.

[0116] The third gripper 60 likewise comprises a gripper jaw pair having a first gripper jaw 66 and a second gripper jaw 68.

[0117] Here, the first gripper jaw 66 and the second gripper jaw 68 can be moved relative to each other by means of an actuator 69 in order to selectively clamp the flat workpiece 12 between them or to release it.

[0118] An actuator 70 is provided for moving the second gripper 58 and the third gripper 60 along the direction of movement L.

[0119] Moreover, the handling assembly 54 is mounted for rotation on the frame 24.

[0120] Here, an axis of rotation is oriented parallel to the longitudinal extent of the handling assembly 54. That is, the axis of rotation is also parallel to the direction of movement L, which corresponds to the longitudinal extent.

[0121] For this purpose, the handling assembly is mounted on the frame 24 by means of a first rotary bearing 72 and a second rotary bearing 74.

[0122] Furthermore, a rotary drive 76 is provided, by means of which the handling assembly 54 can be rotated relative to the frame 24.

[0123] With regard to their distance and with regard to their rotational position, which results from the rotational position of the handling assembly 54, the second gripper 58 and the third gripper 60 can assume an initial position in which the grippers 58, 60 are positioned at a comparatively small distance, in particular a minimum distance, from each other (see in particular FIG. 6).

[0124] Starting therefrom, the second gripper 58 and the third gripper 60 can be moved away from each other and thus transferred to positions apart from each other (see FIGS. 7 and 8).

[0125] The initial positions of the second gripper 58 and the third gripper 60 are coordinated with the first gripper 28 here in such a way that, in this initial position, the second gripper 58 and the third gripper 60 can move into the free space 44 of the first gripper 28 at least in sections (see also FIG. 11).

[0126] In other words, the free space 44 is dimensioned such that it can accommodate at least a portion of the second gripper 58 and of the third gripper when the latter are in the initial position.

[0127] As an alternative to the handling assembly 54, the positioning device 10 may comprise a second manipulator 54a and a third manipulator 54b, the second manipulator 54a carrying the second gripper 58 and the third manipulator 54b carrying the third gripper 60 (see FIG. 9).

[0128] In the present case, the manipulators 54a, 54b are in the form of two independent industrial robots which, however, cooperate with each other to handle the flat workpiece 12.

[0129] Since the grippers 58, 60 can be positioned and oriented essentially freely in space by means of the manipulators 54a, 54b, they are not mounted for rotation, in contrast to the handling assembly 54.

[0130] Apart from that, reference may be made to the discussions regarding the handling assembly 54, which apply analogously to the alternative with the second manipulator 54a and the third manipulator 54b.

[0131] In particular, the grippers 58, 60 are identical in configuration to the alternative comprising the handling assembly 54.

[0132] For operating the positioning device 10, a control unit 78 is also provided (see FIG. 1).

[0133] The control unit comprises a first machine learning module 80, which is adapted to identify a grippable edge K of the limp flat workpiece 12 based on the camera image B, generated by the camera 22, of the flat workpiece 12.

[0134] To this end, the first machine learning module is equipped with a trained artificial neural network 82.

[0135] Furthermore, a second machine learning module 84 is provided, which is adapted to determine a gripping point for the first gripper 28 based on the camera image B, generated by the camera 22, of the limp flat workpiece 12. The gripping point includes a gripper position as well as a gripper orientation of the first gripper 28 and is located, in particular, in the region of the grippable edge K.

[0136] The second machine learning module 84 is also equipped with a trained artificial neural network 86.

[0137] In addition, a third machine learning module 88 is provided, which is adapted to identify a type of the limp flat workpiece 12 based on the camera image B, generated by the camera 22, of the limp flat workpiece 12.

[0138] The third machine learning module 88 likewise comprises a trained artificial neural network 90.

[0139] It is understood that the control unit 78 has to be coupled at least indirectly to each actuator and each sensor of the positioning device 10. In FIG. 1, for the sake of greater clarity, only some of these couplings are drawn in by dashed lines in an exemplary manner.

[0140] The functionality of the control unit 78 and of the positioning device 10 as a whole will be discussed below together with a method of positioning the limp flat workpiece 12.

[0141] The aim of the method is to transfer the limp flat workpiece 12 starting from a random, in particular irregularly folded, state to a flat spread-out state and to place it in the further processing machine 14.

[0142] In this process, the flat workpiece 12 is first provided in its random state on the manipulation surface 20.

[0143] In this state, a camera image B of the flat workpiece 12 is generated by the camera 22 and transmitted to the control unit 78.

[0144] The camera image B is then subdivided into partial images by the control unit 78.

[0145] The partial images are transmitted to the first machine learning module 80, in particular to the associated artificial neural network 82, which, by extracting characteristic image features for each partial image, establishes a probability with which it shows a grippable edge K of the flat workpiece 12.

[0146] More precisely, for each partial image a probability is established with which it belongs to one of the categories “no edge”, “grippable edge” and “ungrippable edge”. A grippable edge K is considered to have been established when the partial image with the relatively highest probability of the category “grippable edge” has been found.

[0147] In this way, the position of a grippable edge K of the flat workpiece 12 can be identified by means of the first machine learning module 80.

[0148] At least the partial image of the camera image B showing the edge K is furthermore transmitted to the second machine learning module 84.

[0149] By extracting characteristic image features of at least this partial image by means of the artificial neural network 86, the second machine learning module identifies a gripping point for the first gripper 28, which is located at the edge K identified by means of the first machine learning module 80.

[0150] Optionally, the camera image B is also transmitted to the third machine learning module 88. The artificial neural network 90 comprised by this machine learning module 88 can identify a type of the flat workpiece by extracting characteristic image features. In this way, for example, flat workpieces 12 that do not conform to a specified type can be identified and eliminated from the provisioning area 18.

[0151] In the present example, flat workpieces 12 other than towels can thus be detected and excluded from processing.

[0152] Subsequently, the identified grippable edge K of the flat workpiece 12 is gripped by means of the first gripper 28.

[0153] To this end, the respective lower gripper jaws 32, 38, which comprise the arcuate retaining surfaces 46, 48, are guided under the edge K to be gripped in a pivoting movement of the first gripper 28. In the position resulting from this movement, the flat workpiece 12 is then gripped by closing the gripper 28, i.e. by the respective upper gripper jaws 34, 40 approaching the lower gripper jaws 32, 38.

[0154] The flat workpiece 12, more precisely the portion of the grippable edge K located between the two gripper jaw pairs 30, 36, is then transferred to the second gripper 58 and the third gripper 60, which assume their initial positions for this purpose (see FIG. 6).

[0155] In the case that instead of the handling assembly 54, the positioning device comprises the second manipulator 54a and the third manipulator 54b, which carry the second gripper 58 and the third gripper 60, respectively, the second gripper 58 and the third gripper 60 are transferred to a position corresponding to that depicted in FIG. 6, by means of the manipulators 54a, 54b.

[0156] Using the first manipulator 26, the first gripper 28 together with the gripped flat workpiece 12 is positioned relative to the second gripper 58 and the third gripper such that the second gripper 58 and the third gripper 60 move substantially simultaneously into the free space 44 between the gripper jaw pairs 30, 36 (see FIG. 12).

[0157] Thereafter, the first gripper 28 is moved to a position spaced apart from the handling assembly 54 by means of the first manipulator 26.

[0158] Now the flat workpiece 12 has to be transferred to a flat spanned position.

[0159] For this purpose, a gripping force for both the second gripper 58 and the third gripper 60 is reduced in comparison to an initial gripping state, which corresponds to the gripping state in which these two grippers 58, 60 have taken over the flat workpiece 12 from the first gripper 28.

[0160] Here, the reduced gripping force is sufficiently large to continue to hold the flat workpiece 12 by means of the second gripper 58 and by means of the third gripper 60. This means that the flat workpiece 12 cannot slip out of these grippers 58, 60.

[0161] At the same time, however, the gripping force is sufficiently small so that a relative movement between the flat workpiece 12 and the grippers 58, 60 along the direction L is possible.

[0162] In this connection, both the second gripper 58 and the third gripper 60 are moved outward until both grippers 58, 60 arrive at a respectively allocated corner E of the flat workpiece 12 (see FIG. 13; starting position of the grippers 58, 60 shown in dashed lines).

[0163] For detecting the corners E, both grippers 58, 60 are equipped with an appropriate sensor, in particular an optical sensor 92, 94.

[0164] In this relative position of the second gripper 58 and the third gripper 60 with respect to the flat workpiece 12, in the positioning device 10 equipped with the handling assembly 54, the handling assembly 54 is pivoted by means of the rotary drive 76 toward the belt conveyor 16 and the flat workpiece 12 is deposited thereon in a flat condition by opening the grippers 58, 60, thus releasing the flat workpiece 12.

[0165] In the variant of the positioning device 10 which comprises the second manipulator 54a and the third manipulator 54b, a corresponding movement of the grippers 58, 60 is realized by means of the manipulators 54a, 54b in order to deposit the flat workpiece 12 in a planar state.

[0166] The above-described traversing movements of the grippers 58, 60 can be made easier if the gripped edge K of the flat workpiece 12 is provided with a hem comprising a thickened portion on the edge of the flat workpiece 12. Such a thickened portion prevents slipping out of the grippers 58, 60, but allows the grippers 58, 60 to be traversed relative to the edge K.

[0167] In one variant of the method, the grippers 58, 60 are not moved relative to the flat workpiece at the same time, but one after the other. That is, the flat workpiece 12 is first held by one of the grippers 58, 60 the gripping force of which is not reduced. The respective other gripper 58, 60 is then traversed by means of the linear drive unit 56 until it arrives at an associated corner E.

[0168] Then the flat workpiece 12 is held by means of the gripper 58, 60 which has arrived at the corner E and the gripping force of which is then no longer reduced. The other gripper 58, 60 is traversed accordingly until it arrives at the other corner E.

[0169] FIG. 10 illustrates a positioning device 10 according to a second embodiment.

[0170] In the following, only the differences from the first embodiment shown in FIGS. 1 to 9 will be discussed.

[0171] Moreover, identical or mutually corresponding elements of the positioning device 10 are provided with the same reference numbers.

[0172] In the second embodiment, the provisioning area 18 comprises a provisioning container 96 instead of the manipulation surface 20. One or more limp flat workpieces 12 are provided in this container, with only a single flat workpiece 12 being illustrated by way of example in FIG. 10.

[0173] In this case, the camera 22 is again adapted and arranged such that it can generate a camera image of the flat workpiece 12 in the provisioning container 96.

[0174] The method of positioning the limp flat workpiece 12 proceeds in the same way as in the first embodiment. This applies both to the variant involving the handling assembly 54 and to the variant involving the second manipulator 54a and the third manipulator 54b. The flat workpiece 12 is merely gripped from the provisioning container 96 rather than from the manipulation surface 20.

[0175] FIG. 11 shows a third embodiment of the positioning device 10. Only the differences from the first and second embodiments will be discussed here.

[0176] Identical or corresponding elements of the positioning device 10 are provided with the same reference numbers.

[0177] The provisioning area 18 of the positioning device 10 now comprises both a manipulation surface 20 and a provisioning container 96. In this regard, the third embodiment is a combination of the first embodiment and the second embodiment.

[0178] Further provided is a provisioning manipulator 98, which is shown only schematically in FIG. 11 and is in the form of an industrial robot.

[0179] A provisioning gripper 100 is fitted to the provisioning manipulator 98.

[0180] Here, a limp flat workpiece 12 is transferred from the provisioning container 96 onto the manipulation surface 20 by means of the provisioning manipulator 98 and the provisioning gripper 100. For this purpose, the provisioning manipulator 98 and the provisioning gripper 100 are coupled to the control unit 78.

[0181] Proceeding from a state in which the flat workpiece 12 lies on the manipulation surface 20, the method of positioning the limp flat workpiece 12 proceeds as in the first embodiment. Again, this applies to both variants of the first embodiment.