Positioning system for positioning work object, industrial system, and method of controlling positioning system

Abstract

A positioning system (10) for positioning a work object (16), the positioning system comprising a first mobile robot (12) including a first base (26a), a first traction arrangement (28a) for moving the first base over a surface (24), and a first work object support (30a); and a second mobile robot (14) including a second base (26b), a second traction arrangement (28b) for moving the second base over the surface, and a second work object support (30b); wherein the first and second work object supports are configured to support the work object and collectively drive the work object to rotate around a rotation axis (18) relative to the first and second bases; and wherein the first0 and second traction arrangements are configured to move the first and second bases in a synchronized manner over the surface while the first and second work object supports support the work object.

Description

[0001] POSITIONING SYSTEM FOR POSITIONING WORK OBJECT, INDUSTRIAL SYSTEM, AND METHOD OF CONTROLLING POSITIONING SYSTEM

[0002] Technical Field

[0003] The present disclosure generally relates to positioning systems. In particular, a positioning system comprising two mobile robots, an industrial system comprising such positioning system and an industrial processing device, and a method of controlling a positioning system, are provided.

[0004] Background

[0005] A conventional workpiece positioner may comprise a headstock and a tailstock at a fixed distance from the headstock. The headstock is active and drives rotation of a fixture holding a workpiece around a rotation axis while the workpiece is being processed by an industrial processing device, such as a welding robot. The tailstock is passive and is driven to rotate around the rotation axis by the rotation of the fixture. As an alternative, a conventional workpiece positioner may comprise two headstocks.

[0006] A handling robot may be used to load a workpiece to the workpiece positioner and to unload the workpiece from the workpiece positioner after processing. A use of both such workpiece positioner and such handling robot becomes relatively complex and occupies floor space. Moreover, the fixture typically needs to be changed if another type of workpiece is to be processed.

[0007] Summary

[0008] One object of the invention is to provide an improved positioning system for positioning a work object.

[0009] A further object of the invention is to provide an improved industrial system comprising a positioning system and an industrial processing device. A still further object of the invention is to provide an improved method of controlling a positioning system.

[0010] These objects are achieved by the positioning system according to appended claim i, the industrial system according to appended claim 7 and the method according to appended claim 8.

[0011] The invention is based on the realization that by splitting a workpiece positioner to provide a positioning system where a first work object support is carried by a first mobile robot and a second work object support is carried by a second mobile robot, the positioning system becomes more flexible and less space-demanding than a conventional positioning system comprising a workpiece positioner and a handling robot.

[0012] According to a first aspect, there is provided a positioning system for positioning a work object, the positioning system comprising a first mobile robot including a first base, a first traction arrangement for moving the first base over a surface, and a first work object support; and a second mobile robot including a second base, a second traction arrangement for moving the second base over the surface, and a second work object support; wherein the first and second work object supports are configured to support the work object and collectively drive the work object to rotate around a rotation axis relative to the first and second bases; and wherein the first and second traction arrangements are configured to move the first and second bases in a synchronized manner over the surface while the first and second work object supports support the work object.

[0013] The principle of providing the first work object support on the first mobile robot and the second work object support on the second mobile robot, physically separated from the first mobile robot, provides several advantages. The first and second mobile robots enable the work object to be both transported to and from a processing location by the first and second traction arrangements and to rotate the work object around the rotation axis by the first and second work object supports at the processing location or during transportation to or from the processing location. Thus, a dedicated positioner and a handling robot for loading and unloading the work object to such positioner may not be needed, which in turn enables space savings and cost reductions. The ability of the positioning system to simultaneously transport the work object over the surface and to rotate the work object around the rotation axis also enables elimination of any downtime for orienting the work object around the rotation axis.

[0014] Moreover, due to the physical separation, a distance between the first and second mobile robots can be adapted to support work objects of different lengths along the rotation axis. A flexibility of the positioning system is thereby improved. Such flexibility improvement is especially advantageous for processing environments with a relatively high variation of different workpieces and a relatively low volume of workpieces.

[0015] Moreover, due to the physical separation, the first and second mobile robots can be driven towards each other to engage, and then optionally lift, the work object. The first and second mobile robots can also be driven away from each other to disengage the work object.

[0016] The first and second mobile robots are configured to locate the first and second work object supports for rotation around the rotation axis, e.g., concentric with each other. Due to a rotation of the work object around the rotation axis, the work object can be processed circumferentially around the rotation axis, e.g., by an industrial processing device. The processing may for example be welding or cutting. The first and second work object supports may collectively drive the work object to rotate endlessly, e.g., a plurality of full turns, around the rotation axis.

[0017] The work object may comprise one or more workpieces. Optionally, the work object may also comprise a fixture holding the one or more workpieces. Universal fixtures can not be used for all types of workpieces. Instead, each workpiece often requires a specific fixture. The workpieces may for example be battery trays or yellow goods, i.e., material for construction and earthmoving equipment, quarrying equipment and fork-lift trucks.

[0018] Each of the first and second mobile robots may be an automated guided vehicle, AGV, such as an autonomous mobile robot, AMR. The positioning system may comprise only two mobile robots, i.e., the first and second mobile robots.

[0019] When the first and second bases move in a synchronized manner, a distance and an orientation between the first and second work object supports maybe kept substantially fixed, or fixed. In order to move the first and second mobile robots in a synchronized manner over the surface, the first and second mobile robots maybe electronically linked. To this end, one or more parameters associated with the first mobile robot may be used to control the second traction arrangement, or vice versa. Examples of parameters include a position, an orientation, a velocity and an acceleration of the first base and a load on the first mobile robot, such as a force or a torque on the first work object support. A position, an orientation, a velocity and / or an acceleration of the second base may then be controlled by controlling the second traction arrangement based on the one or more parameters associated with the first mobile robot.

[0020] Each of the first and second bases may for example be a platform. Each of the first and second traction arrangements may for example comprise one or more wheels and / or one or more continuous tracks for engaging the surface. The surface may for example be a horizontal surface, such as a floor.

[0021] The first work object support maybe drivable to rotate around the rotation axis, e.g., by a first rotation motor. In these cases, the first mobile robot may comprise a headstock including the first work object support. The second work object support may or may not be drivable. In cases where the second work object support is drivable, the second mobile robot may comprise a headstock including the second work object support drivable to rotate around the rotation axis, e.g., by a second rotation motor. In cases where the second work object support is passive, i.e., not drivable, the second mobile robot may comprise a tailstock including the second work object support rotationally supported around the rotation axis. In any case, the above variants enable the first and second work object supports to collectively drive the work object to rotate around the rotation axis. Each of the first and second work object supports may for example be a turning disc.

[0022] The first mobile robot may comprise a first support structure between the first base and the first work object support for rotationally supporting the first work object support around the rotation axis. Correspondingly, the second mobile robot may comprise a second support structure between the second base and the second work object support for rotationally supporting the second work object support around the rotation axis.

[0023] The first and second mobile robots may be configured to perform an omnidirectional motion of the first and second work object supports, respectively, in a horizontal plane relative to the surface while the work object is supported by the first and second work object supports. This enables the work object to be moved in an arbitrary horizontal direction and rotated around a vertical direction by the first and second traction arrangements, at the same time as the work object is rotated around the rotation axis by the first and second work object supports. With omnidirectional motion, the first work object support maybe driven in any horizontal direction at the same time as the first work object support rotates around a vertical axis.

[0024] Omnidirectional motion of the first and second work object supports can be realized by the first and second traction arrangements comprising at least two independently drivable (in a respective heading direction) and independently steerable (around a respective vertical steering axis) drive wheels. Alternatively, omnidirectional motion of the first and second work object supports can be realized by the first and second traction arrangements comprising mecanum wheels. As a further example, omnidirectional motion of the first and second work object supports can be realized by each of the first and second traction arrangements comprising a differential drive and where the first and second support structures are rotatable relative to the first and second bases, respectively, around a vertical axis.

[0025] The positioning system may be configured such that a mechanical compliance of the first work object support is lower than a mechanical compliance of the second work object support, or vice versa. Thus, the first mobile robot may be controlled such that the first work object support is relatively stiff while the second work object support is relatively compliant. This concept enables the positioning system to prevent malfunctioning of the positioning system due to any inaccuracies associated therewith, such as with positions and orientations of the first and second bases.

[0026] The first and second work object supports may be configured to orient the rotation axis at least in a horizontal plane. This enables the work object to be positioned upside down by the first and second work object supports.

[0027] The positioning system may further comprise a control system comprising at least one data processing device and at least one memory having at least one computer program stored therein, the at least one computer program comprising program code which, when executed by the at least one data processing device, causes the at least one data processing device to control the first and second traction arrangements and at least one of the first and second work object supports. The control system may be embodied in many different ways. In some variants, the control system includes a first controller in the first mobile robot and a second controller in the second mobile robot. The control system may alternatively or additionally comprise an external controller, i.e., external to the first and second mobile robots.

[0028] The at least one computer program may comprise program code which, when executed by the at least one data processing device, causes the at least one data processing device to perform, or command performance of, any operation described herein, such as to control the first and second traction arrangements to move the first and second bases in a synchronized manner over the surface, and to control the first and / or the second work object support to drive the work object to rotate around the rotation axis,

[0029] The at least one computer program may comprise program code which, when executed by the at least one data processing device, causes the at least one data processing device to provide length data indicative of a length of the work object; and control the first and second traction arrangements based on the length data. This enables an efficient loading, transportation, orientation and unloading of the work object. The first and second traction arrangements may be controlled such that a distance between the first and second work object supports corresponds to the length, and such that an orientation of each of the first and second work object supports is oriented transverse to the rotation axis, while the first and second mobile robots travel over the surface.

[0030] The first and second work object supports may be configured to orient the rotation axis at an angle, e.g., of at least five degrees, to a horizontal plane. To this end, the first mobile robot may for example comprise a first vertical motor arranged to move the first work object support, e.g., along the first support structure, relative to the first base, and a first tilting motor arranged to tilt the first work object support, e.g., around a horizontal axis relative to the first base. Correspondingly, the second mobile robot may for example comprise a second vertical motor arranged to move the second work object support, e.g., along the second support structure, relative to the second base, and a second tilting motor arranged to tilt the second work object support, e.g., around a horizontal axis relative to the second base. The first and second vertical motors may for example be controlled such that the first work object support is vertically raised and / or the second work object support is vertically lowered, or vice versa. One of the first and second tilting motors may optionally be replaced with a passive tilting joint, such as a universal joint.

[0031] The at least one computer program may comprise program code which, when executed by the at least one data processing device, causes the at least one data processing device to provide angle data indicative of the angle; and control the first and second traction arrangements based on the angle data. The first and second traction arrangements may for example be controlled such that a horizontal distance between the first and second mobile robots is changed in synchronization with the change of the angle. For example, when the angle increases, this distance decreases, and vice versa. The angle data may for example be sent from an angle sensor, associated with the first or second tilting motor, to the control system.

[0032] According to a second aspect, there is provided an industrial system comprising the positioning system according to the first aspect including the control system, and an industrial processing device, wherein the at least one computer program comprises program code which, when executed by the at least one data processing device, causes the at least one data processing device to control the industrial processing device to perform an operation on the work object; and control the first and / or the second work object support to rotate the work object around the rotation axis simultaneously with controlling the industrial processing device to perform the operation. The control system of this aspect may comprise a controller external to the first and second mobile robots and / or associated with the industrial processing device.

[0033] Alternatively, or in addition, the at least one computer program may comprise program code which, when executed by the at least one data processing device, causes the at least one data processing device to control the first and second traction arrangements to move the first and second bases simultaneously with controlling the industrial processing device to perform the operation.

[0034] According to a third aspect, there is provided a method of controlling a positioning system for positioning a work object, the method comprising providing a first mobile robot including a first base, a first traction arrangement and a first work object support; and providing a second mobile robot including a second base, a second traction arrangement and a second work object support; supporting the work object by the first and second work object supports; controlling, by a control system, the first and second traction arrangements to move the first and second bases in a synchronized manner over a surface while the first and second work object supports support the work object; and controlling, by the control system, the first and / or the second work object support to rotate the work object around a rotation axis relative to the first and second bases. The method according to the third aspect may comprise any operation described in connection with the first and second aspects, or vice versa.

[0035] The first and second work object supports may be configured to orient the rotation axis at least in a horizontal plane.

[0036] The method may further comprise providing, in the control system, length data indicative of a length of the work object; and controlling, by the control system, the first and / or the second traction arrangement based on the length data.

[0037] The method may further comprise controlling, by the control system, the first and second work object supports to orient the rotation axis at an angle to a horizontal plane.

[0038] The method may further comprise providing, in the control system, angle data indicative of the angle; and controlling, by the control system, the first and second traction arrangement based on the angle data.

[0039] The method may further comprise providing an industrial processing device; and controlling, by the control system, the industrial processing device to perform an operation on the work object while the work object is supported by the first and second work object supports.

[0040] The method may further comprise controlling the first and / or the second work object support to rotate the work object around the rotation axis simultaneously with controlling the industrial processing device to perform the operation. The method may further comprise controlling the first and second traction arrangements to move the first and second bases simultaneously with controlling the industrial processing device to perform the operation.

[0041] Brief Description of the Drawings

[0042] Further details, advantages and aspects of the present disclosure will become apparent from the following description taken in conjunction with the drawings, wherein:

[0043] Fig. 1: schematically represents a side view of a positioning system comprising two mobile robots;

[0044] Fig. 2: schematically represents a side view of the positioning system when the mobile robots have been driven towards a work object;

[0045] Fig. 3: schematically represents a side view of the positioning system when the work object has been vertically lifted by the mobile robots;

[0046] Fig. 4: schematically represents a side view of the positioning system when the work object has been rotated by the mobile robots;

[0047] Fig. 5: schematically represents a side view of the work object;

[0048] Fig. 6: schematically represents a side view of a work object according to a further example;

[0049] Fig. 7: schematically represents a side view of a work object according to a further example;

[0050] Fig. 8: schematically represents a top perspective view of an industrial system comprising the positioning system and an industrial processing device;

[0051] Fig. 9: schematically represents a side view of a positioning system according to a further example and a work object according to a further example;

[0052] Fig. 10: schematically represents a side view of the positioning system in Fig. 9 and a work object according to a further example;

[0053] Fig. 11: schematically represents a side view of a positioning system according to a further example; Fig. 12: schematically represents a side view of the positioning system in Fig. n when a work object has been tilted;

[0054] Fig. 13: schematically represents a block diagram of exemplifying components of the industrial system; and

[0055] Fig. 14: is a flowchart outlining general steps of a method.

[0056] Detailed Description

[0057] In the following, a positioning system comprising two mobile robots, an industrial system comprising such positioning system and an industrial processing device, and a method of controlling a positioning system, will be described. The same or similar reference numerals will be used to denote the same or similar structural features.

[0058] Fig. 1 schematically represents a side view of a positioning system 10a. The positioning system 10a comprises a first mobile robot 12a, here exemplified as a first AMR, and a second mobile robot 14a, here exemplified as a second AMR. Fig. 1 further shows a work object 16a. The positioning system 10a is configured to transport the work object 16a and to position the work object 16a around a rotation axis 18. In Fig. 1, the rotation axis 18 lies in a horizontal plane 20. Fig. 1 further shows a Cartesian global coordinate system 22. The global coordinate system 22 is fixed with respect to a horizontal surface 24, here exemplified as a floor.

[0059] The first mobile robot 12a comprises a first base 26a, a first traction arrangement 28a and a first turning disc 30a. The first traction arrangement 28a is configured to move the first base 26a over the surface 24.

[0060] Correspondingly, the second mobile robot 14b comprises a second base 26b, a second traction arrangement 28b and a second turning disc 30b. The second traction arrangement 28b is configured to move the second base 26b over the surface 24.

[0061] Each of the first and second bases 26a, 26b is here exemplified as a platform.

[0062] The first and second turning discs 30a, 30b are examples of a first and a second work object support, respectively. Fig. 1 further shows Cartesian first and second local coordinate systems 32a, 32b in fixed relationship with the first and second bases 26a, 26b, respectively.

[0063] In this example, each of the first and second traction arrangements 28a, 28b comprises a plurality of independently drivable and independently steerable wheels 34. The first and second mobile robots 12a, 14a are thereby configured to perform an omnidirectional motion of the first and second bases 26a, 26b, respectively, and thereby also of the first and second turning discs 30a, 30b, respectively, relative to the surface 24.

[0064] The first mobile robot 12a of this specific and non-limiting example further comprises a first rotation motor 36a for driving rotation of the first turning disc 30a relative to the first base 26a around the rotation axis 18, a first support structure 38a arranged on the first base 26a and supporting the first turning disc 30a, and a first vertical motor 40a for vertically raising or lowering the first turning disc 30a relative to the first base 26a. The first mobile robot 12a further comprises a first controller 42a configured to control the first traction arrangement 28a and thereby a position and an orientation of the first base 26a in the global coordinate system 22, control the first rotation motor 36a and thereby a rotational position of the first turning disc 30a in the first local coordinate system 32a, and control the first vertical motor 40a and thereby a vertical position of the first turning disc 30a in the first local coordinate system 32a. The first support structure 38a, the first turning disc 30a, the first rotation motor 36a and the first vertical motor 40a form one example of a first headstock arranged on the first base 26a.

[0065] Correspondingly, the second mobile robot 14b of this specific and nonlimiting example further comprises a second rotation motor 36b for driving rotation of the second turning disc 30b relative to the second base 26b around the rotation axis 18, a second support structure 38b arranged on the second base 26b and supporting the second turning disc 30b, and a second vertical motor 40b for vertically raising or lowering the second turning disc 30b relative to the second base 26b. The second mobile robot 14b further comprises a second controller 42b configured to control the second traction arrangement 28b and thereby a position and an orientation of the second base 26b in the global coordinate system 22, control the second rotation motor 36b and thereby a rotational position of the second turning disc 30b in the second local coordinate system 32b, and control the second vertical motor 40b and thereby a vertical position of the second turning disc 30b in the second local coordinate system 32b. The second support structure 38b, the second turning disc 30b, the second rotation motor 36b and the second vertical motor 40b form one example of a second headstock arranged on the second base 26b. The first and second controllers 42a, 42b may constitute, or be comprised by, a control system 42.

[0066] The work object 16a has a length 44a. In Fig. 1, the work object 16a rests on a stationary external support 46 on the surface 24 at a loading location 48. Length data indicative of the length 44a is provided in the control system 42.

[0067] Fig. 2 schematically represents a side view of the positioning system 10a when the first and second turning discs 30a, 30b support the work object 16a. A position and an orientation of the rotation axis 18 in the global coordinate system 22 is provided in the control system 42, for example by visual recognition of the shape of the work object 16a, by manual entry or by default. The rotation axis 18 may for example be a geometric center line parallel with the length 44a and / or a mass center line parallel with the length 44a around which the work object 16a should be rotated. Since also the length 44a is known by the control system 42, the control system 42 can provide a first engagement position 50a in the global coordinate system 22 where the first turning disc 30a should engage the work object 16a, and a second engagement position 50b in the global coordinate system 22 where the second turning disc 30b should engage the work object 16a. The first and second traction arrangements 28a, 28b are then controlled to drive the first and second bases 26a, 26b, respectively, and as shown with arrows 52a, 52b, respectively, such that the first and second turning discs 30a, 30b are brought in engagement with the first and second engagement positions 50a, 50b, respectively, and here such that the first and second turning discs 30a, 30b are concentric with the rotation axis 18. The first and second mobile robots 12a, 14a are thus capable of self-loading the work object 16a. The engagements between the first and second turning discs 30a, 30b and the work object 16a can be realized in many different ways and may for example include one or more of friction, a shape lock, a magnetic force and / or a clamping force. One or more sensors, such as a load sensor or an optical sensor, may also be used to sense the engagements.

[0068] Fig. 3 schematically represents a side view of the positioning system 10a. In Fig. 3, the first and second vertical motors 40a, 40b have been driven to raise the first and second turning discs 30a, 30b vertically relative to the first and second bases 26a, 26b such that the work object 16a is vertically lifted as shown with arrow 54. The first and second mobile robots 12a, 14a thus share the load of the work object 16a. The control system 42 keeps track of the positions of the first and second turning discs 30a, 30b in the first and second local coordinate systems 32a, 32b, respectively.

[0069] The work object 16a can alternatively be horizontally slid off the external support 46, or the external support 46 can be retracted downwards, e.g., in case the positioning system 10a would not comprise the first and second vertical motors 40a, 40b. In any case, the first and second bases 26a, 26b may now be moved in a synchronized manner away from the loading location 48, e.g., by moving the work object 16a in the Y-direction of the global coordinate system 22, or by first rotating the work object 16a 90 degrees around the Z-axis of the global coordinate system 22 and then moving the work object 16a in the X-direction of the global coordinate system 22.

[0070] Fig. 4 schematically represents a side view of the positioning system 10a. In Fig. 4, the first and second mobile robots 12a, 14a have been moved from the loading location 48 to a processing location 56 while supporting the work object 16a, e.g., such that the distance between the first and second turning discs 30a, 30b and a relative orientation between the first and second turning discs 30a, 30b are constant. The control system 42 keeps track of the positions of the first and second bases 26a, 26b in the global coordinate system 22. At the processing location 56, or while travelling towards the processing location 56, the first and second rotation motors 36a, 36b are driven to rotate the work object 16a around the rotation axis 18 as shown with arrow 58. The control system 42 keeps track of the orientations of the first and second turning discs 30a, 30b in the first and second local coordinate systems 32a, 32b, respectively. Due to the ability of the first and second vertical motors 40a, 40b to vertically raise the first and second turning discs 30a, 30b, the relatively wide work object 16a can, when raised, be rotated a plurality of full turns around the rotation axis 18.

[0071] Fig. 5 schematically represents a side view of the work object 16a. The work object 16a of this specific and non-limiting example comprises two fixtures 60a and a workpiece 62a to be processed held between the two fixtures 60a. Thus, also the fixture 60a is picked up by the first and second mobile robots 12a, 14a as described in connection with Figs. 2 and 3.

[0072] Fig. 6 schematically represents a side view of a work object 16b according to a further example. The work object 16b of this specific and non-limiting example has a length 44b and comprises one fixture 60b and a plurality of workpieces 62b to be processed held by the fixture 60b.

[0073] Fig. 7 schematically represents a side view of a work object 16c according to a further example. The work object 16c of this specific and non-limiting example has a length 44c and is constituted by a single workpiece 62c without any fixture.

[0074] Fig. 8 schematically represents a top perspective view of an industrial system 64. The industrial system 64 comprises the positioning system 10a and a welding robot 66. The welding robot 66 is one example of an industrial processing device. The welding robot 66 of this example comprises a manipulator 68 and a tool 70 carried by the manipulator 68. Although the industrial system 64 is here exemplified as comprising one welding robot 66, the industrial system 64 may comprise a plurality of welding robots 66. The welding robot 66 is positioned at the processing location 56. In Fig. 8, also the first and second mobile robots 12a, 14a carrying the work object 16a are positioned at the processing location 56.

[0075] The work object 16a is picked up by the first and second mobile robots 12a, 14a at the loading location 48. The first and second traction arrangements 28a, 28b are then controlled to move the first and second bases 26a, 26b in a synchronized manner from the loading location 48 to the processing location 56 for processing while supporting the work object 16a. Such movements of the first and second mobile robots 12a, 14a may for example include defining, in the control system 42, a trajectory of the work object 16a from the loading location 48 to the processing location 56 in the global coordinate system 22, where the trajectory includes a path and an orientation of the work object 16a along the path. Based on this information, each of the first and second mobile robots 12a, 14a becomes kinematically bound to a specific trajectory including positions and orientations of the first and second turning discs 30a, 30b in the global coordinate system 22.

[0076] At the processing location 56, the work object 16a, more specifically the workpiece 62a thereof, is then processed by the welding robot 66 while the first and second mobile robots 12a, 14a rotate the work object 16a around the rotation axis 18. The first and second mobile robots 12a, 14a thereby function as a rotatable workpiece positioner for the welding robot 66. Information regarding the position and orientation of the work object 16a in the global coordinate system 22 is available to the welding robot 66, e.g., via the control system 42. For example, by knowing the position and orientation of the first and second bases 26a, 26b in the global coordinate system 22 and the positions and orientations of the first and second turning discs 30a, 30b in the first and second local coordinate systems 32a, 32b, respectively, the positions and orientations of the first and second turning discs 30a, 30b in the global coordinate system 22, and thereby also the position and orientation of the work object 16a in the global coordinate system 22, can be unequivocally determined. If the work object 16a is long such that the entire length 44a does not fit within a workspace of the welding robot 66, the first and second traction arrangements 28a, 28b maybe controlled to move the first and second bases 26a, 26b in a synchronized manner to reposition the work object 16a, e.g., along the length 44a, rather than arranging the welding robot 66 on a track.

[0077] The work object 16a is then transported out of the processing location 56, such as back to the loading location 48, by the first and second mobile robots 12a, 14a, i.e., by controlling the first and second traction arrangements 28a, 28b to move the first and second bases 26a, 26b in a synchronized manner while the first and second turning discs 30a, 30b support the work object 16a. A next workpiece may now be transported to the processing location 56 by another pair of mobile robots at the same time as the work object 16a is unloaded by the first and second mobile robots 12a, 14a outside of the processing location 56. The positioning system 10a is very flexible and little space-demanding.

[0078] Fig. 9 schematically represents a side view of a positioning system 10b. Mainly differences with respect to the positioning system 10a will be described. The positioning system 10b comprises a first mobile robot 12b and a second mobile robot 14b. The first mobile robot 12b differs from the first mobile robot 12a by not comprising the first vertical motor 40a. The second mobile robot 14b differs from the second mobile robot 14a by not comprising the second rotation motor 36b and by not comprising the second vertical motor 40b. The first support structure 38a, the first turning disc 30a and the first rotation motor 36a form a further example of a first headstock arranged on the first base 26a. The second support structure 38b and the second turning disc 30b form one example of a second tailstock arranged on the second base 26b. Fig. 9 further shows a work object i6d carried by the first and second mobile robots 12b, 14b and having a length 44b. By driving the first rotation motor 36a, the work object i6d can be rotated around the rotation axis 18. Fig. io schematically represents a side view of the positioning system lob and a work object i6e having a length 44c, substantially shorter than the length 44d. As can be gathered from Figs. 9 and 10, the positioning system 10b is very flexible can easily adapt a distance between the first and second turning discs 30a, 30b to the different lengths 44b, 44c of the work objects i6d, i6e.

[0079] Fig. 11 schematically represents a side view of a positioning system 10c comprising a first mobile robot 12c and a second mobile robot 14c. Mainly differences with respect to the positioning system 10a will be described. The positioning system 10c comprises a first mobile robot 12c and a second mobile robot 14c. The first mobile robot 12c differs from the first mobile robot 12a by additionally comprising a first tilting motor 72a configured to rotate the first turning disc 30a relative to the first base 26a around a horizontal first tilting axis 74a. Correspondingly, the second mobile robot 14c differs from the second mobile robot 14a by additionally comprising a second tilting motor 72b configured to rotate the second turning disc 30b relative to the second base 26b around a horizontal second tilting axis 74b.

[0080] The first support structure 38a, the first turning disc 30a, the first rotation motor 36a, the first tilting motor 72a and the first vertical motor 40a form a further example of a first headstock arranged on the first base 26a. Correspondingly, the second support structure 38b, the second turning disc 30b, the second rotation motor 36b, the second tilting motor 72b and the second vertical motor 40b form a further example of a second headstock arranged on the second base 26b.

[0081] Fig. 12 schematically represents a side view of the positioning system 10c. In Fig. 12, the first and second mobile robots 12c, 14c have tilted the work object i6f as shown with arrow 76 from the state in Fig. 11 where the rotation axis 18 is parallel with the horizontal plane 20, to a state where the rotation axis 18 is at an angle 78 to the horizontal plane 20. The angle 78 may for example be at least 15 degrees. The tilting of the work object i6f may for example be used at the processing location 56 to provide a gravity position of the work object i6f for arc welding. To provide this tilting of the work object i6f, at least one of the first and second traction arrangements 28a, 28b, at least one of the first and second vertical motors 40a, 40b, and at least one of the first and second tilting motors 72a, 72b are controlled in a synchronized manner. In the specific and non-limiting example shown in Fig. 12, the first traction arrangement 28a is controlled to move the first base 26a towards the second mobile robot 14c as shown with arrow 80a, the second traction arrangement 28b is controlled to move the second base 26b towards the first mobile robot 12c as shown with arrow 80b, the first vertical motor 40a is controlled to vertically lower the first turning disc 30a relative to the first base 26a as shown with arrow 82a, the second vertical motor 40b is controlled to vertically raise the second turning disc 30b relative to the second base 26b as shown with arrow 82b, the first tilting motor 72a is controlled to rotate the first turning disc 30a around the first tilting axis 74a (counterclockwise in Fig. 12) relative to the first base 26a, and the second tilting motor 72b is controlled to rotate the second turning disc 30b around the second tilting axis 74b (counterclockwise in Fig. 12) relative to the second base 26b. By these simultaneous movements of the first and second turning discs 30a, 30b, the work object i6f can be tilted. During these movements of the first and second turning discs 30a, 30b, the positions and orientations of the first and second turning discs 30a, 30b relative to the first and second bases 26a, 26b, respectively, are monitored by the control system 42 in the first and second local coordinate systems 32a, 32b, respectively.

[0082] Due to the omnidirectional motion of the first and second traction arrangements 28a, 28b, this tilting can also be performed simultaneously with a horizontal movement of the work object i6f by the first and second traction arrangements 28a, 28b and a rotation of the work object i6f around a vertical axis by the first and second traction arrangements 28a, 28b.

[0083] One, several or all of the positioning systems loa-ioc, one, several or all of the first mobile robots I2a-i2c, one, several or all of the second mobile robots 143-140, one, several or all of the lengths 44a-44f, and one, several or all of the work objects i6a-i6f may also be referred to with reference numerals "io", "12", "14", "44" and "16", respectively.

[0084] Fig. 13 schematically represents a block diagram of exemplifying components of the industrial system 64. The industrial system 64 comprises the first mobile robot 12, the second mobile robot 14 and the welding robot 66. The industrial system 64 of this example further comprises an optional external controller 42c. The welding robot 66 comprises a welding controller 42d for controlling operations of the welding robot 66. Since the welding robot 66 is one example of an industrial processing device, the welding controller 42d is one example of an industrial processing device controller. As one of many possible implementations, the control system 42 of this example comprises the first controller 42a, the second controller 42b, the external controller 42c and the welding controller 42d. In any case, the control system 42 comprises at least one data processing device 84, here one in each of the first controller 42a, the second controller 42b, the external controller 42c and the welding controller 42d, and at least one memory 86, here one in each of the first controller 42a, the second controller 42b, the external controller 42c and the welding controller 42d. The memories 86 have at least one computer program stored therein.

[0085] The at least one computer program comprises program code which, when executed by the at least one data processing device 84, causes the at least one data processing device 84 to perform, or command performance of, various operations as described herein. In this manner, the control system 42 is configured to control the first and second traction arrangements 28a, 28b, the first and second vertical motors 40a, 40b, the first and second tilting motors 72a, 72b and the first and second rotation motors 36a, 36b. In particular, the control system 42 is configured to control the first turning disc 30a and / or the second turning disc 30b to collectively drive the work object 16 to rotate around the rotation axis 18 relative to the first and second bases 26a, 26b, and to control the first and second traction arrangements 28a, 28b to move the first and second bases 26a, 26b in a synchronized manner over the surface 24 while the first and second turning discs 30a, 30b support the work object 16.

[0086] The first and second mobile robots 12, 14 further comprise first and second positioning devices 88a, 88b, respectively, for determining a position 90a and an orientation 90b of the first and second bases 26a, 26b, respectively, in the global coordinate system 22. Such positioning devices for mobile robots are previously known as such and may for example be based on one or more of odometry, LIDAR (light detection and ranging), the Global Positioning System (GPS).

[0087] Based on the position 90a and the orientation 90b of the first and second bases 26a, 26b over time, the control system 42 is configured to determine a velocity 90c and an acceleration 9od of each of the first and second bases 26a, 26b in the global coordinate system 22.

[0088] Fig. 13 further shows that the first and second mobile robots 12, 14 comprise first and second load sensors 92a, 92b configured to sense a load on the first and second turning discs 30a, 30b, respectively. The load may for example be a force 9oe and / or a torque 9of that are communicated to the control system 42. The position 90a, the orientation 90b, the velocity 90c, the acceleration 9od, the force 9oe and the torque 9of are examples of parameters, and one, several or all of these may also be referred to with reference numeral "90".

[0089] The first and second mobile robots 12, 14 further comprise first and second energy storages 94a, 94b, respectively, for electrically powering the first and second vertical motors 40a, 40b, the first and second tilting motors 72a, 72b, the first and second rotation motors 36a, 36b, the first and second traction arrangements 28a, 28b, the first and second positioning devices 88a, 88b and the control system 42.

[0090] Length data 96 indicative of the length 44 is provided in the control system 42. The length data 96 maybe provided in the control system 42 in various ways, such as by being input by a human user, by being determined based on load data from the first and second load sensors 92a, 92b and the positions of the first and second bases 26a, 26b when the work object 16 is clamped between the first and second turning discs 30a, 30b, by extracting the information from a QR code (quick-response code) on the work object 16 by a camera (not shown) that may or may not be carried by one of the first and second mobile robots 12, 14, or by Radio-frequency identification (RFID). The control system 42 is configured to control the first and second traction arrangements 28a, 28b based on the length data 96, e.g., such that the distance between the first and second turning discs 30a, 30b corresponds to the length 44.

[0091] As an alternative or an addition to controlling the first and second traction arrangements 28a, 28b based on the length data 96, the first and / or the second traction arrangement 28a, 28b maybe controlled based on the forces 9oe and / or the torques 9of, i.e., based on load feedback from an interface between the work object 16 and any of the first and second mobile robots 12, 14. In this manner, one of the first and second mobile robots 12, 14 may sense when the other one of the first and second mobile robots 12, 14 is forcing the work object 16.

[0092] Angle data 98 indicative of the angle 78 is provided in the control system 42. To this end, the first mobile robot 12 of this example comprises an angle sensor 100 configured to provide and send the angle data 98 to the control system 42. The control system 42 maybe configured to control the first and second traction arrangements 28a, 28b, the first and second vertical motors 40a, 40b and the first and second tilting motors 72a, 72b based on the angle data 98, e.g., as described in connection with Fig. 12.

[0093] In some examples, the first mobile robot 12 is controlled as a master and the second mobile robot 14 is controlled as a slave. For example, the first traction arrangement 28a may be controlled based on a first trajectory in the global coordinate system 22 and the second traction arrangement 28b maybe controlled based on forces 9oe and / or the torques 9of acting on the second turning disc 30b by the first mobile robot 12 via the work object 16, and optionally also based on a second trajectory corresponding (via the length 44) to the first trajectory. In these cases, the first mobile robot 12 may control the first turning disc 30a with a first mechanical compliance and the second mobile robot 14 may control the second turning disc 30b with a second mechanical compliance, higher than the first mechanical compliance. The mechanical compliance of the first and second turning discs 30a, 30b can for example be changed by changing a control of one or more of the first and second traction arrangements 28a, 28b, the first and second vertical motors 40a, 40b and the first and second tilting motors 72a, 72b, respectively.

[0094] Fig. 14 is a flowchart outlining general steps of a method. The method comprises providing S10 a first mobile robot 12 including a first base 26a, a first traction arrangement 28a and a first work object support 30a. The method further comprises providing S12 a second mobile robot 14 including a second base 26b, a second traction arrangement 28b and a second work object support 30b.

[0095] The method may further comprise providing S14 an industrial processing device 66. The method may further comprise providing S16, in a control system 42, length data 96 indicative of a length 44 of the work object 16.

[0096] The method further comprises supporting S18 the work object 16 by the first and second work object supports 30a, 30b. The method further comprises controlling S20, by a control system 42, the first and second traction arrangements 28a, 28b to move the first and second bases 26a, 26b in a synchronized manner over a surface 24 while the first and second work object supports 30a, 30b support the work object 16. The controlling S20 may further comprise controlling S22, by the control system 42, the first and / or the second traction arrangement 28a, 28b based on the length data 96.

[0097] The method may further comprise controlling S24, by the control system 42, the first and second work object supports 30a, 30b to orient the rotation axis 18 at an angle 78 to a horizontal plane 20. The method may further comprise providing S26, in the control system 42, angle data 98 indicative of the angle 78. The method may further comprise controlling S28, by the control system 42, the first and second traction arrangements 28a, 28b based on the angle data 98.

[0098] The method further comprises controlling S30, by the control system 42, the first and / or the second work object support 30a, 30b to rotate the work object 16 around a rotation axis 18 relative to the first and second bases 26a, 26b.

[0099] The method may further comprise controlling S32, by the control system 42, the industrial processing device 66 to perform an operation on the work object 16 while the work object 16 is supported S18 by the first and second work object supports 30a, 30b. The method may further comprise controlling S34 the first and / or the second work object support 30a, 30b to rotate the work object 16 around the rotation axis 18 simultaneously with controlling S32 the industrial processing device 66 to perform the operation. The method may further comprise controlling S36 the first and second traction arrangements 28a, 28b to move the first and second bases 26a, 26b simultaneously with controlling S32 the industrial processing device 66 to perform the operation.

[0100] While the present disclosure has been described with reference to exemplary embodiments, it will be appreciated that the present invention is not limited to what has been described above. For example, it will be appreciated that the dimensions of the parts maybe varied as needed. Accordingly, it is intended that the present invention may be limited only by the scope of the claims appended hereto.

Claims

25CLAIMS1. A positioning system (io) for positioning a work object (16), the positioning system (io) comprising:- a first mobile robot (12) including a first base (26a), a first traction arrangement (28a) for moving the first base (26a) over a surface (24), and a first work object support (30a); and- a second mobile robot (14) including a second base (26b), a second traction arrangement (28b) for moving the second base (26b) over the surface (24), and a second work object support (30b); wherein the first and second work object supports (30a, 30b) are configured to support the work object (16) and collectively drive the work object (16) to rotate around a rotation axis (18) relative to the first and second bases (26a, 26b); and wherein the first and second traction arrangements (28a, 28b) are configured to move the first and second bases (26a, 26b) in a synchronized manner over the surface (24) while the first and second work object supports (30a, 30b) support the work object (16).

2. The positioning system (10) according to claim 1, wherein the first and second work object supports (30a, 30b) are configured to orient the rotation axis (18) at least in a horizontal plane (20).

3. The positioning system (10) according to any of the preceding claims, further comprising a control system (42) comprising at least one data processing device (84) and at least one memory (86) having at least one computer program stored therein, the at least one computer program comprising program code which, when executed by the at least one data processing device (84), causes the at least one data processing device (84) to:- control the first and second traction arrangements (28a, 28b) and at least one of the first and second work object supports (30a, 30b).4- The positioning system (io) according to claim 3, wherein the at least one computer program comprises program code which, when executed by the at least one data processing device (84), causes the at least one data processing device (84) to:- provide length data (96) indicative of a length (44) of the work object (16); and- control the first and second traction arrangements (28a, 28b) based on the length data (96).

5. The positioning system (10) according to any of the preceding claims, wherein the first and second work object supports (30a, 30b) are configured to orient the rotation axis (18) at an angle (78) to a horizontal plane (20).

6. The positioning system (10) according to claims 4 and 5, wherein the at least one computer program comprises program code which, when executed by the at least one data processing device (84), causes the at least one data processing device (84) to:- provide angle data (98) indicative of the angle (78); and- control the first and second traction arrangements (28a, 28b) based on the angle data (98).

7. An industrial system (64) comprising the positioning system (10) according to claim 3 and an industrial processing device (66), wherein the at least one computer program comprises program code which, when executed by the at least one data processing device (84), causes the at least one data processing device (84) to:- control the industrial processing device (66) to perform an operation on the work object (16); and- control the first and / or the second work object support (30a, 30b) to rotate the work object (16) around the rotation axis (18) simultaneously with controlling the industrial processing device (66) to perform the operation.

8. A method of controlling a positioning system (10) for positioning a work object (16), the method comprising:- providing (Sio) a first mobile robot (12) including a first base (26a), a first traction arrangement (28a) and a first work object support (30a); and- providing (S12) a second mobile robot (14) including a second base (26b), a second traction arrangement (28b) and a second work object support (30b);- supporting (S18) the work object (16) by the first and second work object supports (30a, 30b);- controlling (S20), by a control system (42), the first and second traction arrangements (28a, 28b) to move the first and second bases (26a, 26b) in a synchronized manner over a surface (24) while the first and second work object supports (30a, 30b) support the work object (16); and- controlling (S30), by the control system (42), the first and / or the second work object support (30a, 30b) to rotate the work object (16) around a rotation axis (18) relative to the first and second bases (26a, 26b).

9. The method according to claim 8, wherein the first and second work object supports (30a, 30b) are configured to orient the rotation axis (18) at least in a horizontal plane (20).

10. The method according to claim 8 or 9, further comprising:- providing (S16), in the control system (42), length data (96) indicative of a length (44) of the work object (16); and- controlling (S22), by the control system (42), the first and / or the second traction arrangement (28a, 28b) based on the length data (96).

11. The method according to any of claims 8 to 10, further comprising:- controlling (S24), by the control system (42), the first and second work object supports (30a, 30b) to orient the rotation axis (18) at an angle (78) to a horizontal plane (20).2812. The method according to claim 11, further comprising:- providing (S26), in the control system (42), angle data (98) indicative of the angle (78); and- controlling (S28), by the control system (42), the first and second traction arrangements (28a, 28b) based on the angle data (98).

13. The method according to any of claims 8 to 12, further comprising:- providing (S14) an industrial processing device (66); and- controlling (S32), by the control system (42), the industrial processing device (66) to perform an operation on the work object (16) while the work object (16) is supported (S18) by the first and second work object supports (30a, 30b).

14. The method according to claim 13, further comprising:- controlling (S34) the first and / or the second work object support (30a, 30b) to rotate the work object (16) around the rotation axis (18) simultaneously with controlling (S32) the industrial processing device (66) to perform the operation.

15. The method according to claim 13 or 14, further comprising:- controlling (S36) the first and second traction arrangements (28a, 28b) to move the first and second bases (26a, 26b) simultaneously with controlling (S32) the industrial processing device (66) to perform the operation.

Images