METHOD AND CONTROL SYSTEM FOR THE CALIBRATION OF A HANDLING APPARATUS
20210347055 · 2021-11-11
Inventors
- Christian DANY (Rosenheim, DE)
- Arsalan Mehdi (Rosenheim, DE)
- Erhard BEER (Ebbs, AT)
- Manuel KOLLMUSS (Raubling, DE)
Cpc classification
B25J13/088
PERFORMING OPERATIONS; TRANSPORTING
B25J9/1623
PERFORMING OPERATIONS; TRANSPORTING
G05B2219/40267
PHYSICS
International classification
Abstract
The invention relates to a method to calibrate a handling device (18) including a handling robot or parallel kinematic robot (24), with a tool head (28) suspended from at least two parallel kinematically movable arms (26). Each of the at least two arms comprises an upper arm, which is movable between two end positions about a defined upper-arm swivel axis (38). Each of the at least two arms also comprises a lower arm (40), which is swivelably mounted on the upper arm. The upper arms are brought into approximately corresponding angular positions by detection of load torques and/or of angle positions. First one, than another of the upper arms is brought into one of the two end positions, and the angular position reached is detected and used for the position initialization or angle initialization of the particular upper arm, whereupon the upper arm is returned.
Claims
1. A method to calibrate a handling device (18) comprising a handling robot or parallel kinematic robot (24), with a tool head (28) suspended from at least two parallel kinematically movable arms (26), wherein each of the at least two arms (26) comprises an upper arm (36) the method comprising: finding an approximately central position for the tool head (28) within its movement space by iteratively moving each of the at least two upper arms (36) by motor drives (42) connected to each of the at least two upper arms (36), detecting load torques acting on each of the upper-arm swivel axes (38), and comparing the load torques acting on each of the at least two upper arms (36) until the load torques are approximately equal, and detecting initial angular positions for each of the at least swivel axes (38); moving all of the at least two upper arms (36) to a limit position by simultaneously or approximately synchronously moving the at least two upper arms (36) about their particular swivel axes (38), wherein the limit position is defined by a mechanical stop, detecting limit angular positions for each upper arm and limit load torques for each motor drives (42), and returning the tool head (28) to the approximately central position, moving a first one of the at least two upper arms (36) into one of two end positions by moving the particular upper arms (36) about the particular upper-arm swivel axis (38), detecting a first end angular position reached by the particular one upper arm (36), and returning the particular upper arm (36) to its initial angular position, moving a second one of the at least two upper arms (36) into one of its two end positions that was also selected in the previous step by swiveling about the particular upper-arm swivel axis (38); and detecting a second end angular position reached by the upper arm (36).
2. The method of claim 1, wherein the handling robot or parallel kinematic robot (24) further comprises at least three parallel kinematically movable arms (26), wherein each of the at least three arms (26) comprises an upper arm (36), the method further comprising moving a third one of the at least three upper arms (36) into one of two end positions or into the same end positions of the first and second upper arms (36) that was selected in previous steps by swiveling about the particular upper-arm swivel axis (38); and detecting a third end angular position reached by the upper arm (36) in question.
3. The method of claim 2, wherein the handling robot or parallel kinematic robot (24) further comprises at least four parallel kinematically movable arms (26), wherein each of the at least four arms (26) comprises an upper arm (36), the method further comprising moving a fourth one of the at least four upper arms (36) into one of its two end positions or into the same of the two end positions of the first, second and third upper arms (36) that was selected in in previous steps by swiveling about the particular upper-arm swivel axis (38); and detecting a fourth end angular position reached by the upper arm (36) in question.
4. The method of claim 1, wherein the detecting load torques step is performed in a permanent manner or repeatedly during the movements of the upper arms (36), wherein differences in successive torque values are identified as the limit position or an end position for the particular upper arm (36) in question.
5. The method of claim 4, wherein the detecting load torques step is performed iteratively during moving of at least one of the upper arms (36) into the selected end position.
6. The method of claim 1, wherein the detecting angular positions steps is performed in a permanent manner or repeatedly during the movements of the upper arms (36), wherein differences in successively detected angular positions are identified as the limit position or an end position for the particular upper arm (36) in question.
7. The method of claim 6, wherein the detecting angular positions steps is performed iteratively during moving of at least one of the upper arms (36) into the selected end position.
8. The method claim 1, wherein, after moving all of the at least two the upper arms (36) to the limit position, moving at least one of the at least two upper arms (36) into one of the two end positions by moving about the particular upper-arm swivel axis (38).
9. The method claim 1, further comprising calibrating a rotational position of the tool head (38) by bringing the tool head (28) into a defined rotational position with the position and/or orientation of the at least two movable arms (26) being known; and by moving the tool head (28) being moved to a defined distance from an object or from a stationary contact point (48), and by contacting the tool head (28) with said the object or contact point (48) by rotating of the tool head (28), and by detecting a new rotational position reached thereby.
10. A handling device (18) comprising: a handling robot or parallel kinematic robot (24), with a tool head (28) suspended from at least two parallel kinematically movable arms (26), wherein each of the at least two arms (26) comprises an upper arm (36), which is motor-movable between two end positions about a defined upper-arm swivel axis (38), and each of the at least two arms (26) also comprises a lower arm (40), which is mounted swivelably movable on the upper arm (36), and wherein the arms (26) hold a tool head (28), which is movably suspended from at least two lower arms (40), and which tool head (28) has a movable drive connection, which is movable about at least one rotational axis, and which tool head (28) is movable within a defined movement range by swivel movements of the upper arms (36) and by the thereby guided lower arms (40), with the swivel movements being program-controlled and coordinated to each other, wherein control programs for the control of all movements of the at least two movable arms (26) are stored in a central control unit and comprise one or more calibration programs.
11. handling device (18) claim 10, which forms a part of a conveying apparatus, stacking apparatus, or palletizing apparatus for conveying, handling, stacking, or palletizing of piece goods or bundles.
12. The handling device (18) of claim 10, which forms a part of a production apparatus or workpiece-treatment apparatus for production, treatment, or modification of workpieces in a production environment.
13. The handling device (18), wherein the movable drive connection comprises a length-variably movable or articulately movable cardan shaft (30) between a stationary drive motor (44) and the tool head (28).
Description
BRIEF DESCRIPTION OF THE FIGURES
[0045] In the following passages, the attached figures further illustrate typical embodiments of the invention and their advantages. The size ratios of the individual elements in the figures do not necessarily reflect the real size ratios. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged in relation to other elements to facilitate an understanding of the invention.
[0046]
[0047]
[0048]
[0049] The same or equivalent elements of the invention are each designated by the same reference characters in the
DETAILED DESCRIPTION OF THE INVENTION
[0050] The schematic perspective view of
[0051] This layer pattern formed in a desired manner by the handling device 18 can subsequently be conveyed further in transport direction 12 and be delivered from the surface for support and transport 16 to a downstream conveying surface 20, where potentially remaining spaces between the packaging goods, piece goods, or bundles, which have been brought into the layer pattern, are closed by pushing together the packaging goods, piece goods, or bundles by contact bars 22, which are shiftable transversely to the transport direction 12 and horizontally toward the side edges of the layer pattern, and/or by at least one contact bar 22, which is liftable and lowerable and thus positionable transversely to the transport direction 12.
[0052] The layer arrangements formed from packaging goods, piece goods, or bundles, which were manipulated and arranged in such a way by the handling device 18 in the handling station 14, can be stacked on top of each other, preferably in each instance layer-wise, in a palletizing station, which is, however, not shown here and which is disposed downstream from the conveying surface 20, and the layer arrangements can be deposited on a pallet for further packaging, handling, and/or for a transport, and be made available for dispatch.
[0053] As
[0054] In addition, the arms 26 hold the tool head 28, which is movably suspended from each of the total of three lower arms, and which is movable within a defined movement range in the area of the surface for support and transport 16 by swivel movements of the upper arms as well as by the thereby guided lower arms, with the swivel movements being program-controlled and coordinated to each other. Likewise not discernible in the
[0055] These rotational movements can be induced and controlled, in particular, by a cardanically movable drive shaft 30, which leads in vertical or diagonal direction from an upper suspension 32 of the parallel kinematic robot 24 downward to the tool head 28. The upper suspension 32, to which the upper arms of the movable arms 26 as well as the drive motors thereof are mounted, and also the at least one drive motor for the cardan shaft or drive shaft 30, forms an upper part of a frame 34 of the handling station 14. The entire handling device 18 or the parallel kinematic robot 24 is held at this upper suspension 32 and movably mounted in the manner described.
[0056] A construction that is customary for such parallel kinematic robots 24 provides swivel bearings at the upper suspension 32 for each of the total of three movable arms 26, in which context the upper arms 36 can in each instance be moved about horizontal swivel axes 38, which are arranged below the upper suspension 32. Both the upper arms 38, which are movable about the horizontal swivel axes 38 and at which the lower arms 40 holding the tool head 28 are swivelably arranged, and the drive shaft 30 responsible for the rotational movements of the tool head 28 and the gripper jaws arranged thereto (not illustrated) are typically operated electromotively, with the particular drive motors 42 for the upper arms 36 and the drive motor 44 for the drive shaft 30, which drive motors 42 and 44 are anchored in the upper suspension 32, are clearly discernible from the
[0057] A particular advantage of the electric drive motors 42 and 44 used for the handling device 18 on the one hand consists in the therewith attainable high positioning precision, as is desirable for the precise guiding of the tool head 28 within the movement range above the surface for support and transport 16 of the handling station 14 (cf.
[0058] It should be pointed out here that the parallel kinematic robot or handling robot 24, which is the object of the calibration method according to the invention, in the exemplary embodiment shown here has three upper arms 36 that are equally dimensioned and in each instance arranged at an angular offset of 120° to each other with in each instance identical lower arms 40 and with a tool head 28 suspended movably and/or rotatably therebetween. Such so-called tripods are often used in practice and are excellently suited for precise movement control, such as for the manipulation of articles, objects, piece goods, bundles, or for the manipulation of groups of a plurality of such articles, objects, piece goods, bundles, as has already been explained above with reference to the
[0059] In the calibration method according to the invention as illustrated below in the consecutive method steps by the
[0060] In order to enable an as precise as possible calibration of the movable components, approximately corresponding angular positions of all three upper arms 36 are in each instance adjusted in a first method step (cf.
[0061] It does not need to be explicitly mentioned at this point that in order to perform this first method step, a central control unit (not illustrated), which is responsible for the control of the motor drives 42 of the upper arms 36, has been switched on and the control program implemented therein has been started, which, for example after a shutdown phase, requires a certain period of time for the program start. Normally, all motor drives 42 are also initialized and referenced during this starting phase in order to be able to carry out each control command for the driving of the positioning motors 42 in drive movements that are as precise as possible.
[0062] In this first method step described here, in which approximately corresponding angular positions of the three upper arms 36 are in each instance adjusted by the motor drives 42 by a detection of the load torques acting on the upper-arm swivel axes 38 and by comparison of the particular load torques acting on the three upper arms 36, the primary objective, which is also characteristic for the calibration method according to the invention, is to find an approximately central position for the tool head 28 within its movement space and/or manipulation space, which for lack of optical or other types of position control can most expediently be performed by the detection of the load torques acting on the upper arms 36 with the tool head 28 unloaded. For this purpose and as and when required, the upper arms 36 can be successively adjusted or moved up and down by relatively small adjustment angles for as long as until they have a corresponding load torque within an expedient hysteresis range of their load torques of less than one Newton-meter, for example.
[0063] This hysteresis range that is expedient or advantageously useable in practice can optionally also be less than 0.5 N-m, in particular, less than approximately 0.3 N-m, such that the upper arms 36 can have a corresponding load torque within these limits, which can be identified or assumed as adjustment of same positioning angles. In this way it is possible to ensure that the angular positions adjusted at the upper arms 36 by their drive motors 42 both in each instance have minimum difference angles to the upper and lower end positions and define a location of the tool head 28, which is within a defined distance to an approximately central position within the movement range of the tool head. It can therefore be assumed that after this adjustment procedure of the first method step, the tool head 28 stands or hangs nearly central within the movement range and between the three movable arms 26 of the parallel kinematic robot 24.
[0064] After this central position of the tool head 28 with approximately horizontally aligned upper arms 36 has been reached, the upper arms 36 are simultaneously and synchronously swiveled upward in a slow adjustment movement, as is illustrated in
[0065] The shortest possible length adjustment for such a telescopic drive shaft 30 represents a mechanical limitation that cannot be overcome, so it is absolutely necessary to take into account the limits of the telescopic capability of the drive shaft 30, especially as this stop also has effects on the upward extension of the movement range of the tool head 28.
[0066] However, not all parallel kinematic robots 24 are necessarily equipped with rotatable tool heads 28 and thus with such drive shafts 30, but rather also function without such a drive shaft 30 in simpler embodiment variants, so that the following calibration process explained based on the following figures is referred to as second method step, that is to say without taking into account the detection of the mechanical stop of the drive shaft 30, which is telescopic in its longitudinal direction.
[0067] After the upper stop for the telescopic drive shaft 30 has been reached according to
[0068] The swivel movements, lifting movements, and lowering movements performed in this connection are indicated by arrows, in which context only the upper arm 36 on the left in
[0069] The particular upper arm 36 can be subsequently returned from its previously adjusted upper end position approximately back into the previously assumed initial angular position, which corresponds to the alignment of the arms 26 according to
[0070] Since not only one of the upper arms 36, but also the other two upper arms 36 are to be referenced in the same manner, another upper arm 36 of the handling device 18 or of the handling robot 24 can in a third method step be brought by motorized swiveling about its upper-arm swivel axis 38 into the same of the two end positions that was also selected in the second method step (
[0071] It should furthermore be mentioned that it is expedient in the context of the method steps of the method according to the invention as explained above to perform a detection of the particular drive torques in a permanent manner and/or repeated at defined intervals during the performance of the second and/or third and/or fourth and/or fifth method steps and during the corresponding motorized movements of the upper arms, as such a permanent detection and monitoring can be used in an advantageous manner in order to be able to identify a mechanical stop and/or end stop for the particular upper arm in question when an exceeding is determined for a specified and/or variably definable difference value for torque values gathered in successive measurements.
[0072] Such a torque limitation allows to reliably detect an existing mechanical stop for each of the performed swivel movements of the motor-driven upper arms only based on a detection of the electric currents to be applied and without using any optical or other motion sensory detection device, with the mechanical stop normally being characterized by a torque limit. By no means is it necessary for such a torque limit to be fixedly specified; by the possibility of permanent, dynamic change, the torque limit can rather be advantageously deployed and used in a movement process for different angular positions and different torque values connected thereto. From this also follows the universal usability and functional capability of the described referencing, even with different grippers or tripod robots, which can be equipped, for example, with differently dimensioned arms and/or differently dimensioned and thus differently heavy tool heads.
[0073] When starting the centering in the context of a calibration procedure, it can be advantageous to identify the particular upper arm that supplies the highest torque value with an adjustment. This identified torque can be used, for example, to set an appropriate torque limit for the subsequent calibration procedure based on this value, with the addition of an expedient margin, for example, of 0.5 to approximately 1.5 N-m. The identified torque can suffice during the procedure of centering the tool head to move the tool head to the center of its movement range without exceeding this torque limit.
[0074] The method can moreover provide that an iterative torque detection during the swiveling (raising) of at least one of the upper arms toward the selected end position to the particular upper-arm end stop is provided. Hereby it is possible during the performance of the method to constantly identify if an end position and thus a mechanical stop has already been reached. If, specifically, the previously identified torque limit is exceeded during a movement of one of the upper arms, it is checked whether the axis in question has moved about a defined small swivel angle by, for example, more than 0.3 degrees since the setting of the torque limit or since the last torque increase. If this is the case, this is not identified as collision or as having reached the mechanical stop, but rather merely as statement that the torque produced by the drive is not sufficient for moving the corresponding axis. If the torque limit is subsequently increased by an expedient value of, for example, approximately 0.5 N-m, the swivel movement can be continued on this basis. If, however, the axis movement of the measured torque increase was less than the defined, small difference angle of, for example, 0.3 degrees, it can be assumed in the method according to the invention that a collision has taken place or that the mechanical end stop has been reached.
[0075] This described method can be used for the handling robot in the reaching of any conceivable mechanical stops, thus also, for example, with the tool head contacting a platform located below the tool-head movement range or contacting a horizontal conveying device located there, which horizontal conveying device can be formed, for example, by a modular conveyor belt or the like conveyor device. Since it is not expedient to move the tool head against this horizontal conveying device, in particular, to push this lower support surface downward, this reached position can also be identified and defined as lower end position in the calibration method. If such an expedient test has been performed with the gripper contacting its lower end stop, the gripper can be subsequently lifted and the centering can be performed again in order to move the gripper toward the upper end stops for calibration.
[0076] The schematic depiction of
[0077] For reasons of simplification, a gripping arm arranged at and suspended from a tool head 28 is not illustrated, but serves as the part to be contacted, which is brought into contact with the object and/or with the stationary contact point 48 in order to calibrate the rotary movements of the drive shaft 30 and the drive movements of the drive motor 44 responsible therefor.
[0078] The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following figures and description, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.
[0079] If illustrations and aspects are generally referred to as being “schematic” in the context of the figures, this is by no means intended to imply that the illustration of the figures and their description are of inferior significance with regard to the disclosure of the invention. The person skilled in the art is fully capable of gathering sufficient information from the schematically and abstractly drawn illustrations for facilitating the understanding of the invention without the understanding being in any way impaired by, for example, the size ratios of the movable parts of the handling device 18 or of other of the drawn elements not being drawn and potentially not being precisely true to scale. On the basis of the more concretely explained realizations of the method according to the invention in the figures, the person skilled in the art as a reader is thus enabled to derive a better understanding of the inventive idea, which is formulated in a more general and/or more abstract manner in the claims and in the general part of the description.
[0080] The invention has been described with reference to a preferred embodiment. Those skilled in the art will appreciate that numerous changes and modifications can be made to the preferred embodiments of the invention and that such changes and modifications can be made without departing from the spirit of the invention. It is therefore intended that the appended claims cover all such equivalent variations as fall within the true spirit and scope of the invention.
LIST OF REFERENCE CHARACTERS
[0081] 8 Machine environment
[0082] 10 Horizontal conveying device
[0083] 12 Transport direction, conveying direction
[0084] 14 Handling station
[0085] 16 Surface for support and transport
[0086] 18 Handling device
[0087] 20 Conveying surface
[0088] 22 Contact bar
[0089] 24 Parallel kinematic robot, handling robot
[0090] 26 Arm, movable arm
[0091] 28 Tool head
[0092] 30 Drive shaft, cardan shaft, drive connection
[0093] 32 Upper suspension
[0094] 34 Frame
[0095] 36 Upper arm
[0096] 38 Horizontal swivel axis
[0097] 40 Lower arm
[0098] 42 Drive motor (for upper arm)
[0099] 44 Drive motor (for drive shaft)
[0100] 46 Rotational axis (tool head, rotatable tool head)
[0101] 48 Contact point, solid object