Control device for a conveyor device and method for controlling a conveyor device

Abstract

Control device for a conveyor device (158), comprising one or more image generating devices (106) for generating at least one image representing at least a portion of the conveyor device (158), a workpiece (164) to be conveyed and / or a workpiece carrier (102), and an evaluation device (112) by means of which information about a relative position between at least one first element (146) of the conveying device (158), the workpiece (164) or the workpiece carrier (102) and at least one second element (148) of the conveying device (158), the workpiece (164) or the workpiece carrier (102) and / or about the type of an element of the conveying device (158), the workpiece (164) or the workpiece carrier (102) can be determined from the at least one image, wherein at least one of the elements (146, 148) whose relative position can be determined is a coupling element (138) for establishing a mechanical coupling between the conveying device (158) and the workpiece (164), between the conveying device (158) and the workpiece carrier (102) or between the workpiece carrier (102) and the workpiece (164) and wherein at least one of the elements (146, 148) whose relative position can be determined is a reference element without a coupling function, which is arranged on the conveying device (158), on the workpiece (164) or on the workpiece carrier (102).

Description

The present invention relates to a control device for a conveying device, by means of which in particular the accuracy of fit of components of the conveying device can be controlled.When conveying workpieces, in particular bodies or body modules, through a production plant, in particular through a production plant of an automobile factory, the requirements for surface treatment and coating, in particular for painting, must be taken into account to a particular extent.The workpieces to be conveyed are arranged directly on a workpiece holder of the conveying device, for example on a receiving element of a conveying chain, or are indirectly connected to the conveying device via an interposed workpiece holder. Such workpiece carriers can be, for example, skids or skid frames, skills, cross members or the like.The contact and receiving points between the conveying device and the workpiece, between the conveying device and the workpiece carrier or between the workpiece carrier and the workpiece must be dimensioned with regard to their tolerances such that a proper locating relative to one another and a secure connection and, if appropriate, centering of these points can always be ensured.As contact and receiving points, coupling elements, for example in the form of pins, bolts or pins, are provided on the conveying device, on the workpiece and / or on the workpiece carrier, which coupling elements project, for example, into openings on another element of the conveying system and / or cooperate with other elements of the conveying system in order to fix the workpiece positively to the workpiece carrier or to a workpiece receiver of the conveying device or in order to fix the workpiece carrier to a workpiece carrier receiver of the conveying device.Thus, in particular, a skid frame has receiving pins, so-called "skid pins", by means of which a workpiece to be conveyed, in particular a vehicle body or a body module, can be releasably locked on the skid frame.The skid pins of a skid frame must maintain predetermined distances from one another within a tolerance range in order to be able to interact with the respectively assigned receiving points of the workpiece in an accurately fitting manner.It is known to perform a check of these skid pins by means of a mechanical test gauge. Such a test jig is manually placed on the skid frame by a person to be tested, and subsequently it is checked by the person to be tested, partly via mechanical slides, whether or not the positions of the skid pins are within the tolerance range.It is also known to install a test jig firmly in a test station and to move the skid frame to be tested into the test station. When the skid frame is in the test station, mechanical sliders are manually operated to perform the test of the skid pins.A disadvantage of these known test methods is that a test jig has to be placed manually by a person checking and / or mechanical sliders have to be manually operated by a person checking in order to perform a check of the skid pins.EP 1 361 017 A2 discloses a control device for a conveying device, comprising a plurality of image generating devices and an evaluation device, by means of which information about a relative position between at least one first element of a workpiece carrier and at least one second element of the workpiece carrier can be determined from the signals of the image generating device.U.S. Pat. No. 6,167,607 B1 discloses a control device which comprises a plurality of illumination devices for illuminating an element to be detected by an image forming device.The object of the present invention is to provide a control device for a conveying device which enables rapid and reliable checking of elements of a conveying device, of a workpiece to be conveyed and / or of a workpiece carrier in order to achieve good accuracy of fit when the checked element interacts with other elements of the conveying device, of the workpiece to be conveyed or of the workpiece carrier.This object is achieved according to the invention by a control device for a conveying device according to claim 1.The present invention is based on the concept of recording the elements to be checked for compliance with their relative positions using an image generating device, in particular a camera, and of ascertaining the relative position of the elements to be checked by evaluating the recorded image or a plurality of recorded images.In this case, the generation of the image and its evaluation preferably take place automatically, which enables a particularly rapid measurement.Preferably, with the control device according to the invention, online measurement is carried out in the normal conveying operation of the conveying device in a production plant, in particular a painting plant.In particular, it can be provided that a check of elements to be checked of the conveying device, the workpiece and / or the workpiece carrier takes place during each passage of the relevant elements through the conveying device.By continuously checking the elements of the conveyor system during operation, problems in the accuracy of fit between the conveyor device, the workpiece and, if applicable, the workpiece carrier are reliably avoided.In particular, no problems arise when placing a workpiece to be conveyed onto coupling elements of a workpiece carrier, because it is ensured that these coupling elements are always within the tolerance range.This increases the process safety during the conveying of the workpieces through the production plant, and faults during the placement of the workpiece on the conveying device or on the workpiece carrier and faults during the locking of the workpiece carrier on a workpiece carrier receptacle of the conveying device are avoided.This achieves significant efficiency and cost advantages.The control device according to the invention enables regular and comprehensive control of the accuracy of fit of the elements of the conveying technology in order to ensure production safety and to avoid accidents.This regular monitoring can in particular prevent the contact and receiving points between the conveying device and the workpiece or between the workpiece carrier and the workpiece from leading to any damage, in particular to a defective paint system.In particular when the workpieces to be conveyed are provided with a coating, it is advantageous if the contact and receiving points between the conveying device and the workpiece or between the workpiece carrier and the workpiece are as small as possible, so that the areas not coated due to the contact between the conveying device and the workpiece or between the workpiece carrier and the workpiece are as small as possible.Preferably, the contact and receiving points between the conveying device and the workpiece or between the workpiece carrier and the workpiece are designed and arranged such that after disassembly they are covered by other elements, in particular connecting elements, preferably in a corrosion-preventing manner, and are thus no longer visible from the outside.In a preferred embodiment of the invention, it is provided that a first difference between an actual position of a first element of the conveying device, the workpiece or the workpiece carrier and a desired position of the first element can be determined by means of the evaluation device.Furthermore, it is preferably provided that a second difference between an actual position of a second element of the conveying device, of the workpiece or of the workpiece carrier and a desired position of the second element can be determined by means of the evaluation device.It is particularly favorable if an actual distance between the first element and the second element can be determined by means of the evaluation device from the first difference and the second difference.In this way, it is achieved that a common deviation of both checked elements from the respective desired position does not affect the determined actual distance between these two elements.It is therefore not necessary in this case, when checking the conveying device, a workpiece to be conveyed or a workpiece carrier by means of the checking device, to bring the part to be checked exactly into a predetermined measurement position relative to the image forming device and / or to center the part to be checked relative to the checking device.Rather, it is sufficient if the part to be checked is positioned relative to the control device in such a way that the image generating device can detect the section of the conveying device, the workpiece to be conveyed or the workpiece carrier required for the evaluation by means of the evaluation device.Furthermore, it is preferably provided that by means of the evaluation device the actual distance between the first element and the second element is comparable to a desired distance.If this actual distance is within a predetermined tolerance range, the checked part can be used for the further conveying process.If the actual distance lies outside the predetermined tolerance range, the checked part is excluded from further use in the conveying device and separated out.This evaluation of the part to be checked is preferably carried out automatically by the evaluation device. It is particularly favorable if the selection of a excluded part is also automatically initiated by the evaluation device.In the control device according to the invention, it is provided that at least one of the elements whose relative position can be determined is a coupling element for producing a mechanical coupling between the conveying device and the workpiece, between the conveying device and the workpiece carrier or between the workpiece carrier and the workpiece.Such a coupling element can be, in particular, a skidpin of a conveyor skid, in particular a diving skid or painting skid, or a receptacle of a suspended goods carrier (hangers), for example an underbody protection hanger (UBS hangers).If the workpieces to be conveyed are moved only purely translationally or are subjected to slight tilting movements, it is sufficient to place the workpiece to be conveyed on such a coupling element. In this case, the workpiece is preferably held securely on the coupling element by gravity.If during the conveying process of the workpieces to be conveyed larger tilting, pivoting and / or rotational movements of the workpieces are carried out, such a coupling element is preferably designed in such a way that it secures the workpiece to be conveyed against detachment from the workpiece carrier or from the conveying device.Furthermore, it is provided that at least one of the elements whose relative position can be determined by means of the evaluation device is a reference element without a coupling function, which is arranged on the conveying device, on the workpiece or on the workpiece carrier.In contrast to a coupling element, such a reference element does not have a mechanical coupling function, but rather merely a marking function. Such a reference element can be designed in particular as a shape or color marking.Such a reference element can have, for example, the shape of a ring, a cross or another geometric shape, which is preferably easily detectable by the evaluation device.In a preferred embodiment of the invention, it is provided that the control device comprises a plurality of image generating devices for generating images of different sections of the conveying device, of the workpiece or of the workpiece carrier. In this way, it is possible to also determine relative positions between elements of the conveying device, of the workpiece or of the workpiece carrier which are far away from one another. Furthermore, by using a plurality of image forming apparatuses, it is also possible to use image forming apparatuses which have only a comparatively low resolution.In principle, it can be provided that the elements of the conveying device, the workpiece or the workpiece carrier to be detected are illuminated only with the ambient light that is present in any case during the generation of the image.Alternatively or additionally, however, it can also be provided that the control device comprises one or more illumination devices for illuminating an element of the conveying device, the workpiece or the workpiece carrier to be detected by an image generating device. In this way, in particular, the contrast of the contour or partial contour of the element to be detected by the evaluation device can be increased.As illumination device, for example, a light source for ultraviolet light (UV light) and / or a light source for infrared light (IR light) can be used, each in combination with an image generating device tuned to the respective light.The images generated by the plurality of image generating devices in a checking operation are preferably generated substantially simultaneously or in a measurement period of at most approximately 10 seconds, in particular at most approximately 2 seconds.Alternatively or additionally to an illumination device, the control device can comprise one or more reflectors, by means of which an element of the conveying device, of the workpiece or of the workpiece carrier to be detected by an image generating device can be illuminated with reflected light.The light reflected by such a reflector can be the ambient light that is present in any case and / or the light emitted by an illumination device of the control device.Preferably, the illumination device and / or the reflector of the control device is designed and arranged such that the illumination of the element to be illuminated takes place in the counter-light method. In this case, the image generating device, in particular a camera, the element to be illuminated and to be detected by the image generating device and the illumination device or the reflector lie on a common rectilinear axis, wherein the illumination device or the reflector is oriented such that the light emitted by the illumination device or the light reflected by the reflector are directed towards the element to be illuminated and towards the image generating device.In order to enable reliable detection of the element to be detected in each case even under adverse light and / or contamination conditions, it is advantageous if an element of the conveying device, of the workpiece or of the workpiece carrier to be detected by an image generating device, for example a coupling element, is provided with a position marking.Such a position marking can be, in particular, a shape and / or color marking.Examples of suitable position markings are a bore, a centered ring, a centered cross or other, preferably rotationally symmetrical markings.The present invention further relates to a method for controlling a conveying device, by means of which in particular the accuracy of fit of components of the conveying device can be controlled.The present invention is based on the further object of providing such a method for checking a conveying device which enables rapid and reliable checking of elements of the conveying device, of a workpiece to be conveyed and / or of a workpiece carrier in order to achieve good accuracy of fit when the checked element interacts with other elements of the conveying device, of the workpiece to be conveyed or of the workpiece carrier.This object is achieved according to the invention by a method for controlling a conveying device according to claim 11.In this case, for comprehensive monitoring of the accuracy of fit of the components of the conveying device and timely discarding of components of the conveying device that are no longer suitable, a workpiece carrier that is no longer suitable or an unsuitable workpiece, it is advantageous if the at least one image is generated during the normal conveying operation of the conveying device.During the generation of the at least one image, the component of the conveying device to be checked, the workpiece carrier or the workpiece can be conveyed at a normal conveying speed or at a measurement conveying speed different therefrom, preferably lower.Alternatively, the component of the conveying device to be checked, the workpiece carrier or the workpiece can be stopped for the generation of the at least one image.Furthermore, in a preferred embodiment of the method according to the invention, it is provided that, on the basis of the ascertained information, an assignment is made between a workpiece to be conveyed and a workpiece carrier, between a workpiece to be conveyed and a workpiece holder of the conveying device, and / or between a workpiece carrier and a workpiece carrier holder of the conveying device.In particular, it can be provided, for example, that by means of automatic image recognition by means of the image generation system of the monitoring device according to the invention, automatic monitoring of a coupling element, in particular of a skidpin, on a workpiece carrier, in particular on a skid frame, and automatic monitoring of a coupling element receptacle assigned to the coupling element of the workpiece carrier on the workpiece to be conveyed takes place. After the determination of the relative positions of the coupling element and the coupling element receptacle on different workpiece carriers and workpieces, those workpiece / workpiece carrier pairs can then be determined in which the coupling element and the coupling element receptacle fit particularly well to one another dimensionally.With the control method according to the invention, it is also possible, when a workpiece is placed on a workpiece holder of the conveying device or on a workpiece carrier, to control whether the workpiece has been correctly locked on the workpiece holder or on the workpiece carrier by controlling the position of the workpiece relative to the workpiece holder or relative to the workpiece carrier. This can be controlled, for example, by controlling a gap width or by controlling the relative position of an element of the workpiece with respect to an element of the workpiece holder or with respect to an element of the workpiece carrier.A further application of the control method according to the invention consists in obtaining information about whether the type of the workpiece and the type of the workpiece carrier are compatible with one another by automatic control of a coupling element on a workpiece carrier and automatic control of a coupling element receptacle on a workpiece to be conveyed. On the basis of the information thus obtained, the correct workpiece carrier can then be assigned to the checked workpiece, or an already performed assignment between a workpiece and a workpiece carrier can be checked for its permissibility.Furthermore, it is possible with the control method according to the invention to check the presence of operating means (such as, for example, door rack, engine hood rack or tailgate rack for a vehicle body or for a body module) on the workpiece, on the workpiece carrier or on the conveying device for a correct positioning, alignment and / or setting.In this case, geometric elements of these operating means are preferably checked to see whether or not they lie within a tolerance field relative to a reference element.Furthermore, it is possible to carry out workpiece type recognition using the control method according to the invention. In this case, a significant detail of the workpiece, for example a corner of a fender of a vehicle body, is recorded with an image generating device and detected by means of the evaluation device of the control device, and a workpiece type is assigned to the workpiece depending on the detected geometry of the workpiece detail.Furthermore, it is possible to check the receptacles for workpiece carriers, in particular skid frames, cross beams or so-called "crossbars", on a conveying device by means of the checking method according to the invention or the checking device according to the invention.In particular, during the transfer of a workpiece, in particular a vehicle body, from one conveying device to another conveying device or to a workpiece carrier before the transfer, the position of the workpiece, the workpiece receptacle of the conveying device or of the workpiece carrier can be checked, so that an erroneous placement of the workpiece on the other conveying device or on the workpiece carrier can be avoided.In this case, it is favorable if a coupling element of the conveying device and a coupling element receptacle of the workpiece are captured by an image generating device and detected by means of the evaluation device in order to determine their relative position with respect to one another.Further, depending on the result of this control, it is possible to change the position of the coupling member and / or the position of the coupling member receptacle by a readjustment operation to ensure the required accuracy of fit.Furthermore, it is possible to check coupling element receptacles, in particular receiving openings, on a workpiece to be conveyed, in particular on a vehicle body or on a body module, as to whether they are within a tolerance range.In particular, the diameter of a receiving opening or the relative position of receiving openings to one another can be controlled here.If an opening is detected with an image generating device and detected by means of the evaluation device, the evaluation device can assign an area to the opening, which is then calculated and compared with a predefined desired circular area.Alternatively or additionally, the center points of different, preferably substantially circular, openings can be determined and their distance calculated. The calculated distance can then be checked to see whether it is within a predetermined tolerance range.If cross bars or so-called "cross bars" are to be attached to a workpiece to be conveyed, the relative positions of receiving bores for these cross bars or "cross bars" on the workpiece can be determined in order to check whether these relative positions coincide within a tolerance range with the relative positions of fastening means, in particular screws, on the cross bars or "cross bars".Further particular embodiments of the control method according to the invention have already been explained above in connection with the particular embodiments of the control device according to the invention.The control device according to the invention is suitable in particular for carrying out the control method according to the invention.Further features and advantages of the invention are the subject matter of the following description and the graphic representation of exemplary embodiments.In the drawings, there are shown: FIG. 1 shows a schematic perspective illustration of a control device for a conveying device, in which workpieces to be conveyed, in particular vehicle bodies, are locked on a respective workpiece carrier, in particular on a skid frame, wherein the control device comprises a plurality of image generating devices, which each generate an image representing a section of the workpiece carrier with a respective locking device for locking the workpiece on the workpiece carrier, wherein the image generation takes place by means of the ambient light; FIG. 2 shows a schematic perspective illustration of a second embodiment of a control device for a conveying device, in which each image forming device is assigned an illumination device for illuminating an element of the workpiece carrier to be detected by the relevant image forming device; FIG. 3 shows a schematic perspective illustration of a third embodiment of a control device for a conveying device, in which each image forming device is assigned a reflector for illuminating an element of the workpiece carrier to be detected by the respective image forming device with reflected light; FIG. 4 shows a schematic representation of contours of different elements of the workpiece carrier at the actual position (solid lines) detected by the respectively assigned image generating device and at the target position (broken lines) assigned to the respective element; FIG. 5 shows a schematic representation of the composition of a total deviation between an actual position of an element of the workpiece carrier detected by means of an image generating device and a desired position assigned to this element from an average deviation of several elements of the workpiece carrier and an individual deviation of the relevant element of the workpiece carrier; FIG. 6 shows a schematic side view of a workpiece carrier held on a workpiece carrier receptacle of a conveying device; FIG. 7 is an enlarged view of the region I from FIG. 6, which shows elements of the workpiece carrier and of the workpiece carrier receptacle, the relative position of which can be determined by means of a control device; and FIG. 8 is an enlarged view of the area II from FIG. 6, showing elements of the workpiece carrier and a workpiece held thereon, the relative position of which can be determined by means of a control device for the conveying device.Identical or functionally equivalent elements are denoted by the same reference numerals in all figures.A control device, shown in FIG. 1 and designated as a whole as 100, for a conveying device for conveying workpieces, in particular vehicle bodies or body modules, through a production plant, in which the workpieces to be conveyed are each arranged on a workpiece carrier 102, comprises a control region 104, which can record a workpiece carrier 102 to be controlled, and one or more image generating devices 106, in particular cameras 108. By means of the image generating devices 106, an image can be generated in each case which represents a section of the workpiece carrier assigned to the respective image generating device 106.Each image generating device 106 is connected via a data line 110 to an evaluation device 112 of the control device 100.The image forming devices 106 can be positioned in any desired position relative to the control area 104 of the control device 100.In particular, it may be provided that one or more image forming devices 106 are arranged on a holding structure 114.The support structure 114 may include, for example, a plurality of vertical posts 116 interconnected in pairs by side rails 118.The longitudinal carriers 118 are preferably aligned substantially horizontally and substantially parallel to a conveying direction 120, along which the workpiece carrier 102 can be conveyed by means of the conveying device into the control region 104 and, after the control measurement has been carried out, can be conveyed out of the control region 104 again.The longitudinal beams 118 of the holding structure 114 can be connected to one another by cross beams 122, which are preferably aligned substantially horizontally and substantially perpendicular to the conveying direction 120.Arranged on the cross members 122 can be in each case one or more holders 124, on each of which an image forming apparatus 106 is held.In the exemplary embodiment shown, the workpiece carrier 102 is designed as a skid or skid frame 126, which comprises two skid skids 130 aligned parallel to a longitudinal direction 128 of the workpiece carrier 102.The skid runners 130 are connected to one another by cross members 132, which are preferably oriented parallel to a transverse direction 134 of the workpiece carrier 102 running perpendicular to the longitudinal direction 128 of the workpiece carrier 102.Each of the cross members 132 carries two respective locking devices 136 for releasably locking a workpiece to the workpiece carrier 102.Each of the locking devices 136 comprises a coupling element 138 for establishing a mechanical coupling between the workpiece carrier 102 and the workpiece, for example in the form of a skidpin 140.In the exemplary embodiment illustrated in the drawing, each coupling element 138 is assigned an image generating device 106, which generates an image of the respective coupling element 138 when the workpiece carrier 102 is in a measurement position in the control region 104 of the control device 100.Preferably, the image generating device 106 is arranged substantially vertically above the respectively associated coupling element 138 of the workpiece carrier 102 when the workpiece carrier 102 is in the measurement position. It is particularly favorable if the optical axis of the image forming apparatus 106 runs through the coupling element 138 to be detected in each case.The relative positions of the image forming devices 106 with respect to one another therefore preferably substantially correspond to the relative positions of the coupling elements 138 of the workpiece carrier 102 with respect to one another.The evaluation device 112 comprises a programmable processor and a memory and software which is suitable for detecting predefined contours of the coupling elements 138 to be detected in the image data generated by the image generating devices 106 and transmitted to the evaluation device 112 and for comparing the actual positions of these contours with stored desired positions of these contours.The desired positions of the contours can be established, for example, by introducing a master workpiece carrier into the measurement position in the control region 104 of the control device 100, by means of the image generating devices 106 images of the coupling elements 138 of the master workpiece carrier are generated, specific contours of the coupling elements 138 of the master workpiece carrier are selected and the positions of these reference contours of the coupling elements 138 of the master workpiece carrier are established and stored as the desired positions of these contours.Alternatively, the contours of the coupling elements 138 to be determined by the evaluation device 112 and their desired positions can also be defined without the use of a master workpiece carrier and stored in the evaluation device 112.The above-described control device 100 functions as follows:During the running operation of the conveying device, by means of which workpieces are conveyed through a painting facility, for example, a workpiece carrier 102 to be checked is conveyed by the conveying device, for example by means of a roller conveyor, into the control region 104 of the control device 100 and is stopped there in a measurement position.In this case, it can be provided in particular that the control region 104 is integrated into the normal conveying path of the workpiece carrier 102, so that the workpiece carrier 102 is preferably controlled by the conveying device during each revolution.The measurement position of the workpiece carrier 102 does not have to be exactly defined, since during the monitoring of the workpiece carrier 102 only relative positions of the coupling elements 138 of the workpiece carrier 102 with respect to one another are determined, but not the positions of the coupling elements 138 with respect to a stationary reference system of the monitoring device 100 or with respect to an exactly positioned master workpiece carrier.It is therefore sufficient if the positioning of the workpiece carrier 102 in the control region 104 is effected, for example, by means of a limit switch.Fixing or centering of the workpiece carrier 102 in the measurement position is not necessary.The workpiece carrier 102 to be checked is stopped in the measurement position for a short measurement time of, for example, at most approximately 10 seconds, in particular at most approximately 2 seconds, and is then conveyed back out of the control region 104 by the conveying device.During this measurement time, an image of the respectively assigned coupling element 138 of the workpiece carrier 102 is generated by means of each image generating device 106.If the time required for image generation is sufficiently short and the times of image generation by the various image generating apparatuses 106 are synchronized with each other, it is also possible to perform measurement with the workpiece carrier 102 continuously passing through the inspection area 104 without the workpiece carrier 102 being stopped at the measurement position.If the measurement takes place while the workpiece carrier 102 is passing through, the passing speed can be a normal conveying speed or a preferably lower measuring conveying speed different from the normal conveying speed.In order to make the contours of the coupling elements 138 to be detected particularly clearly recognizable, the wavelength of the light with which the coupling elements 138 are illuminated and / or the wavelength at which the image generating device 106 captures the image of the coupling element 138 can be selected such that the contour to be detected is represented with the highest possible contrast.For this purpose, the gray values of the recorded image can be adapted and / or filters can be used, in order to take into account in particular the color and the surface structure of the coupling elements 138 to be detected.Furthermore, it is possible to generate a plurality of images of the respectively assigned coupling element 138 at different settings and / or at different wavelengths of the light used for the image generation by means of each image generation device 106, in order to obtain the contour particularly clearly and to generate measurement values that are as accurate as possible.For example, it can be provided that infrared cameras are used as image generating devices 106, in particular when the coupling elements 138 to be detected on the workpiece carrier 102 are colder or warmer than adjacent regions of the workpiece carrier 102 during operation of the conveying device.It is also possible to selectively cool or heat the coupling elements 138 of the workpiece carrier 102 to be detected before the measurement in the control device 100 in order to achieve an infrared contrast with respect to adjacent regions of the workpiece carrier 102.The images generated by the image generating devices 106 are transmitted via the data lines 110 to the evaluation device 112 and evaluated there.For this purpose, the evaluation device 112 determines a contour 142, for example the edge of a circular surface, and the center point 144 of this contour in each image of a coupling element 138.The respectively determined contour 142 and its center point 144 is shown schematically in solid lines in FIG. 4 a) to d) for the four detected coupling elements 138, for example (FIG. 4 a) shows, by way of example, the contour 142 of the coupling element 138 aon the workpiece carrier 102 at the front right, FIG. 4 b) the contour 142 of the coupling element 138 bat the rear right, FIG. 4 c) the contour 142 of the coupling element 138 cin front left and FIG. 4 d) the contour of the coupling element 138 din rear left).The determined center point 144 of the contour 142 represents the respective actual position of the coupling element 138 and is compared by the evaluation device 112 with the center point 144' of the contour 142' of the respective corresponding coupling element 138 of the previously received master workpiece carrier (shown in broken lines in FIGS. 4 a) to d) which represents the desired position of the respective coupling element 138.By this comparison, a vectorial total deviation Δ g between the actual position and the desired position is determined for each coupling element 138.As shown in FIG. 5, this total deviation Δ g is composed of an average vectorial deviation Δ m which is the same for all coupling elements 138, and an individual vectorial deviation Δ i which is different in each case for the different coupling elements 138.The mean deviation Δ m corresponds to a displacement between the measurement position of the measured workpiece carrier 102 and the measurement position of the master workpiece carrier during the installation of the control device 100 and thus contains no information about the relative positions between the coupling elements 138 on the workpiece carrier 102 to be checked.From the individual deviations Δ i the deviations of the relative positions of the coupling elements 138 of the measured workpiece carrier 102 from the relative positions of the coupling elements 138 on the master workpiece carrier are calculated by the evaluation device 112 by means of a calculation program.As a result, the distances of the coupling elements 138 on the measured workpiece carrier 102 from one another in the longitudinal direction 128, in the transverse direction 134 and in the diagonal directions of the workpiece carrier 102 can be calculated, and these distances can be compared with respectively predetermined tolerance ranges in order to assess whether the measured workpiece carrier 102 can be used further in the conveying device or else has to be exchanged and repaired again.In the control device 100 described above, one of the coupling elements 138 of the workpiece carrier 102, for example the front right coupling element 138 a, thus represents a first element 146 of the workpiece carrier 102 and a further coupling element 138, for example the rear right coupling element 138 b, represents a second element 148 of the workpiece carrier 102, wherein information about the relative position between the first element 146 and the second element 148 is determined by means of the evaluation device 112 from the images of sections of the workpiece carrier 102 generated by the image generating devices 106.Alternatively or additionally thereto, it is also possible to determine a relative position between a coupling element 138 and a reference element without a coupling function by means of the above-described control device 100, in that such a reference element, for example a reference point or another reference marking, is arranged on the workpiece carrier 102 and the reference element is likewise recorded by means of an image generating device 106, in order then, analogously to the above-described procedure, to determine the distance of a coupling element 138 from the reference element and compare it with a tolerance range.In order to still enable reliable detection of the coupling element 138 or reference element to be detected in each case by the evaluation device 112 even under adverse light and contamination conditions, it is advantageous to arrange one or more geometric markings, for example in the form of a bore, a centered ring, a centered cross or in the form of another, preferably rotationally symmetrical, marking on the relevant coupling element 138 or reference element.It is furthermore advantageous if the evaluation device 112 and in particular its software is designed such that for the determination of the reference contour and thus the actual position of the coupling element 138 or of the reference element, it is not necessary to recognize the complete geometric shape of the element in question, but rather the evaluation device 112 can already determine its actual position from a partial contour of the element in question. This ensures that a correct measurement of the workpiece carrier 102 is also carried out by means of the control device 100 if, for example, one of the coupling elements 138 or a reference element is at least partially covered with a paint or with impurities.In a variant of the embodiment of the control device 100 illustrated in FIG. 1, it can be provided that the control device 100 comprises only a single image generating device 106, in particular in the form of a single camera 108, which generates an image of all coupling elements 138 to be captured (and optionally of all reference elements to be captured).In this case, the evaluation device 112 determines the contours 142 of a plurality of elements to be detected from the same image.In this case, in order to obtain sufficient accuracy, it is favorable that an image forming apparatus 106 having high resolution is used.In principle, it is also possible to carry out the measurement of a workpiece carrier 102 via the most accurate possible positioning and fixing of the workpiece carrier 102 in the measurement position and the subsequent generation of an image of at least one section of the workpiece carrier 102.In this case, the measurement contains, as imprecision, the manufacturing tolerance between the device for fixing the workpiece carrier 102 in the measurement position, on the one hand, and the elements to be detected, in particular the coupling elements 138 to be detected, on the other hand.A second embodiment of a control device 100 illustrated in FIG. 2 differs from the first embodiment illustrated in FIG. 1 in that the elements to be detected by the image generating devices 106, in particular the coupling elements 138, are not only illuminated with the ambient light which is present in any case, but separate illumination is used for this purpose.This embodiment of the control device 100 therefore comprises one or more illumination devices 150 for illuminating in each case one element of the workpiece carrier 102 to be detected by an image generating device 106, in particular in each case one coupling element 138.The illumination devices 150 are preferably designed and arranged such that the respective element to be illuminated is illuminated in the counter-light method. Here, the image generating device 106, in particular the camera 108, the element to be detected, in particular the coupling element 138 or a reference element, and the illumination device 150, in particular a light source, lie in this order on a straight axis 152, which preferably substantially corresponds to the optical axis of the image generating device 106, wherein the illumination device 150 is oriented such that it emits light towards the element to be detected and towards the image generating device 106.By separately illuminating the elements to be detected by means of the illumination devices 150, the contrast of the contours of the elements to be detected with respect to the environment is increased.In this case, the separate illumination is preferably adapted to the respective colors and contours of the elements to be detected.For example, an ultraviolet (UV) light source or an infrared (IR) light source may be used as the illumination device 150, each in combination with an image forming apparatus 106 responsive to the light in question.Otherwise, the second embodiment of a control device 100 illustrated in FIG. 2 corresponds in terms of construction and functionality to the first embodiment illustrated in FIG. 1, to the above description of which reference is made in this respect.A third embodiment of a control device 100 illustrated in FIG. 3 differs from the second embodiment illustrated in FIG. 2 in that the elements to be detected by the image generating devices 106, in particular the coupling elements 138 or reference elements, are not illuminated, or at least not exclusively, directly by the illumination devices 150, but indirectly by means of a reflector 154, respectively.The reflector 154 can, for example, reflect ambient light towards the element to be detected in each case.Alternatively or additionally, it can be provided that the reflector 154 is used together with an illumination device 150, wherein the reflector 154 reflects light emitted by the illumination device 150 towards the element to be detected.In particular, it can be provided that the illumination device 150 illuminates the reflector 154 in a targeted manner.Preferably, the illumination of the element to be detected is carried out in the counter-light method, wherein the image generating device 106, in particular the camera 108, the element to be detected, for example the coupling element 138, and the reflector 154 lie in this order on a common axis 152, wherein the reflector 154 is oriented such that it reflects light towards the element to be detected and towards the image generating device 106.The reflector 154 can in particular comprise a reflective film.Such a reflective film is preferably designed such that it reflects as much light as possible.In particular, the reflector 154 can have a surface which is white or mirrored and / or is designed in another form such that the highest possible contrast arises with respect to the expected colors of the element to be detected, in particular of the coupling element 138 or of a reference element.Otherwise, the third embodiment of a control device 100 illustrated in FIG. 3 corresponds in terms of construction and functionality to the embodiments of the control device 100 illustrated in FIGS. 1 and 2, to the above description of which reference is made in this respect.A control device 100 with an image generating device 106 and an evaluation device 102 of the type described above can also be used, for example, to check whether a workpiece carrier 102, for example a skid frame 126, is correctly locked to a workpiece carrier receptacle 156 of a conveying device 158, as is schematically illustrated in FIGS. 6 and 7.In this exemplary embodiment, the conveying device 158 comprises a rotary holder 160 which can be moved translationally along a conveying path and in the process can be rotated about an, in particular horizontal, axis of rotation.The rotary holder 160 comprises a plurality of workpiece carrier receptacles 156, in each of which a retaining bolt 162 of the workpiece carrier 102 is received and secured by means of a locking hook.In this case, an image of the region of the workpiece carrier 102 and the conveying device 158 shown in FIG. 7 is recorded by means of an image generating device 106, and two or more contours of the workpiece carrier 102 and the conveying device 158, in particular of the workpiece carrier receptacle 156 and / or of the locking hook, are detected by means of the evaluation device 112. Furthermore, the relative positions of these contours are determined and it is checked whether the distances of these contours are within a predefined tolerance field.In this way, in particular, the position of the locking hook can be checked and checked whether the retaining bolt 162 of the workpiece carrier 102 is present in the workpiece carrier receptacle 156.Thus, in this exemplary embodiment, the retaining bolt 162 is a first element 146 of the workpiece carrier 102, the relative position of which is determined with respect to a second element 148 of the conveying device 158, namely the workpiece carrier receptacle 156.Alternatively or additionally, it is also possible to check a workpiece 164 placed on the workpiece carrier 102 as to whether the workpiece 164 is properly locked on the workpiece carrier 102 by checking the position of the workpiece 164, in particular of a vehicle body or of a body module, relative to a locking device 136 of the workpiece carrier 102, as is schematically illustrated in FIG. 8.In this case, an image of the section of the workpiece 164 shown in FIG. 8 and of the arresting device 136 of the workpiece carrier 102 can be generated in particular by means of an image generating device 106. From this image, the evaluation device 112 of the control device 100 determines contours of the workpiece 164 and of the arresting device 136 and the relative position of these contours with respect to one another. From this relative position, for example, the width of a gap s between an edge 166 of the workpiece 164 and a surface 168 of the locking device 136 can then be determined and it can then be checked whether the width of the gap lies in a predefined tolerance range.Thus, in this embodiment, the locking device 136 is a first element 146 of the workpiece carrier 102, the relative position of which is determined with respect to a second element 148 of the workpiece, namely the lower edge 166 of the workpiece.

Claims

Control device for a conveying device (158), comprising one or more image generating devices (106) for generating at least one image, which represents at least a portion of the conveying device (158), a workpiece (164) to be conveyed and / or a workpiece carrier (102), and an evaluation device (112), by means of which information about a relative position between at least one first element (146) of the conveying device (158), the workpiece (164) or the workpiece carrier (102) and at least one second element (148) of the conveying device (158), the workpiece (164) or the workpiece carrier (102) and / or about the type of an element of the conveying device (158), the workpiece (164) or the workpiece carrier (102) can be determined from the at least one image, wherein at least one of the elements (146, 148) whose relative position can be determined, a coupling element (138) for establishing a mechanical coupling between the conveying device (158) and the workpiece (164), between the conveying device (158) and the workpiece carrier (102) or between the workpiece carrier (102) and the workpiece (164), and wherein at least one of the elements (146, 148), the relative position of which can be determined, is a reference element without a coupling function, which is arranged on the conveying device (158), on the workpiece (164) or on the workpiece carrier (102).Control device according to Claim 1, characterized in that a first difference between an actual position of a first element (146) of the conveying device (158), of the workpiece (164) or of the workpiece carrier (102) and a desired position of the first element (164) can be determined by means of the evaluation device (112).Control device according to Claim 2, characterized in that a second difference between the actual position of a second element (148) of the conveying device (158), of the workpiece (164) or of the workpiece carrier (102) and a setpoint position of the second element (148) can be determined by means of the evaluation device (112).Control device according to claim 3, characterised in that an actual distance between the first element (146) and the second element (148) can be determined by means of the evaluation device from the first difference and the second difference.Control device according to claim 4, characterised in that by means of the evaluation device (112) the actual distance between the first element (146) and the second element (148) is comparable to a desired distance.Control device according to one of Claims 1 to 5, characterized in that the control device (100) comprises a plurality of image generating devices (106) for generating images of different sections of the conveying device (158), of the workpiece (164) or of the workpiece carrier (102).Control device according to one of Claims 1 to 6, characterized in that the control device (100) comprises one or more illumination devices (150) for illuminating an element (138) of the conveying device (158), of the workpiece (164) or of the workpiece carrier (102) which element is to be detected by an image generating device (106).Control device according to one of Claims 1 to 7, characterized in that the control device (100) comprises one or more reflectors (154), by means of which an element (138) of the conveying device (158), of the workpiece (164) or of the workpiece carrier (102), which element is to be detected by an image generating device (106), can be illuminated with reflected light.Control device according to either of Claims 7 and 8, characterized in that the illumination device (150) and / or the reflector (154) is designed and arranged in such a way that the illumination of the element (138) to be illuminated takes place in the counter-light method.Control device according to one of Claims 1 to 9, characterized in that an element (138) of the conveying device (158), of the workpiece (164) or of the workpiece carrier (102) which is to be detected by an image generating device (106) is provided with a position marking.Method for controlling a conveying device (158), comprising: - generating at least one image representing at least a portion of the conveying device (158), a workpiece (164) to be conveyed or a workpiece carrier (102); and - determining information about a relative position between at least one first element (146) of the conveying device (158), the workpiece (164) or the workpiece carrier (102) and at least one second element (148) of the conveying device (158), the workpiece (164) or the workpiece carrier (102) and / or about the type of an element of the conveying device (158), the workpiece (164) or the workpiece carrier (102) from the at least one image; wherein at least one of the elements (146, 148) whose relative position can be determined is a coupling element (138) for establishing a mechanical coupling between the conveying device (158) and the workpiece (164), between the conveying device (158) and the workpiece carrier (102) or between the workpiece carrier (102) and the workpiece (164), and wherein at least one of the elements (146, 148) whose relative position can be determined is a reference element without a coupling function, which is arranged on the conveying device (158), on the workpiece (164) or on the workpiece carrier (102).The method of claim 11, characterized in that the at least one image is generated during normal conveying operation of the conveying device (158).Method according to either of Claims 11 and 12, characterized in that, on the basis of the ascertained information, an assignment is carried out between a workpiece (164) to be conveyed and a workpiece carrier (102), between a workpiece (164) to be conveyed and a workpiece receptacle of the conveying device (158) and / or between a workpiece carrier (102) and a workpiece carrier receptacle (156) of the conveying device (158).

Images