Apparatus and method for mounting a workpiece to an assembly target

Abstract

To mount a workpiece (2) on a mounting target (1), a sensor (30) is moved along the mounting target (1), resulting in a 3D point cloud. The 3D point cloud is used to identify objects on the surface of the mounting target (1) (which, for example, serve as a connection to the workpiece), and the workpiece is finally secured using these detected objects.

Description

The invention relates to an apparatus and a method for mounting a workpiece to a mounting target. This is to be effected in particular using a device in the manner of a robot device or robot arrangement.From US 2017 / 0 124 714 A1, it is known to equip a robot arm with two cameras for the respective acquisition of an image of a component. A 3D point cloud is generated from the images. Geometric properties of the components are in turn identified from the 3D point cloud, wherein, on the basis of the identification of these geometric properties, specific points are illuminated with a laser in order to facilitate the further work.DE 10 2014 001 188 A1 relates to a method for determining height profiles of stacked components in a charge carrier, wherein a three-dimensional point cloud is generated by means of an image recording by two calibrated fixed cameras. Using these, automatic removal of components is carried out by means of gripping devices of a robot.DE 10 2012 015 324 A1 describes that a light section sensor is driven over an object. The light section sensor, which is generally also referred to as a profile section sensor, projects a laser line onto an object and can calculate a height profile on the basis of the time-of-flight ("time-of-flight"). In the method according to DE 10 2012 015 324 A1, a prominent location of the object, along which the light section sensor is traveled, is recognized, which is identified as the edge of the object, so that the position of the object as a whole can be deduced.Further aspects of the prior art relating to the present invention can be found in DE 10 2023 111 251 B4, DE 10 2022 129 066 A1, EP 1 539 562 B1, U.S. Pat. No. 2022 / 0 119 057 A1, U.S. Pat. No. 6,317,953 B1 and JP 2019 / 181 649 A.In particular in motor vehicle construction, a workpiece, such as an underbody element or a wheel arch, must frequently be attached to the vehicle which is already almost finished per se and which may also have wheels and is suspended in the so-called suspension system. In the suspension system, the center of mass of the entire vehicle is displaced slightly, for example with an amplitude of 25 mm, in all spatial directions. It is therefore not easy for a robot to perform the operation of mounting the member (underbody member, wheel arch, and the like). Connecting elements, in particular in the form of screw connection elements, are typically already pre-assembled (welded) on the underbody of the chassis or the wheel arch, which connecting elements are used to attach and fasten the workpiece to be attached (underbody element or wheel arch shell or the like). Such connection objects can be snap nuts, spring nuts, split nuts, split rivets, coarse threaded bolts and / or threaded bolts with metric thread. They are typically galvanized and therefore cannot be easily distinguished from the remaining underbody in camera images if it is formed, for example, from aluminum. Furthermore, snap nuts, spring nuts, split nuts are frequently inserted with a certain tolerance, for example in the case of a bore having a size of 10 mm and a tolerance of a few mm.It is the object of the invention to facilitate the mounting of a workpiece on a mounting target, in particular with regard to the stated application.The object is achieved by a device having the features according to claim 1 and a method having the features according to claim 7.Advantageous refinements according to the invention are found in the dependent claims.The apparatus for mounting a workpiece to a mounting target according to the invention comprises:a first movable unit carrying a sensor for optically detecting object data (it may be a unit movable on a carriage, but preferably it is a movable arm);a first moving unit controller configured to move the sensor in steps along the mounting target by control commands;an evaluation device coupled to the sensor, which is designed to collect the object data from the sensor for each step and to obtain a total of 3D object data by their assignment to the respective control commands and / or a respectively detected position of the sensor;wherein the evaluation device is further configured to recognize objects of at least one predetermined object type on the surface of the mounting target on the basis of the 3D object data and to determine their respective position; wherein the apparatus further comprises:a support device, preferably in the form with at least one (optionally then second) movable arm, wherein the support device has a known location assignment to the first movable unit (calibrated location assignment) and is designed to support the workpiece and to add it to the mounting target depending on the positions of the detected objects;means for attaching the workpiece to the mounting target using the detected objects of the at least one predetermined object type.The device performs data acquisition by driving down with the sensor and subsequent object recognition by the evaluation device and can then subsequently carry out the assembly on the basis of the recognized objects. Here, a 3D point cloud is thus obtained by means of a method sensor. The known spatial assignment between the support device and the first movable arm ensures in a reliable manner that the workpiece can be brought to the mounting target in a precisely fitting and targeted manner and can be fastened there.The object types can be in particular connection objects which are located on the surface of the mounting target, namely the already mentioned snap nuts, spring nuts, split nuts, split rivets, coarse threaded bolts and threaded bolts with metric threads, as can typically be pre-mounted on an underbody or a wheel arch of a chassis.Here, a profile section sensor can be used as a sensor, which acquires distance data in each case along a line (as described above: with time-of-flight ("time-of-flight") measurement), which therefore outputs 2D object data per measurement and which is movable by the arm perpendicular to the line. In the case of a wheel arch, a sensor can be guided stepwise along several successive circle segments.In this case, it is preferably provided that the control device is designed to compare a timing of the guidance of a light source (namely preferably a laser) of the profile section sensor along the line (or of the circle segment) with the timing for moving the profile section sensor (stepwise movement), so that no time is lost and, on the other hand, the next jump to the following line (or to the following circle segment) takes place when the line is in each case completely traversed.Said means for fastening can be part of the supporting device and preferably comprise a further movable arm, wherein the further movable arm contains, for example, a screwing device or other device for closing (actuating the snap nuts, spring nuts, split rivets, split nuts etc., rotating the coarse threaded bolt or the threaded bolt with metric thread and the like).According to a further preferred embodiment, the evaluation device is designed to check whether fastening of the workpiece to the mounting target using the detected objects of the predetermined object types is possible at all and to cause the fastening means to be activated only when the check is positively output. This checking step reliably excludes errors.The method according to the invention for mounting a workpiece on a mounting target is preferably carried out using the mentioned device according to the invention and comprises the following steps:providing the mounting target, in particular a chassis base or a wheel housing, wherein a connection object is provided in each case at a plurality of connection regions;scanning a surface region (of approximately in each dimension between 20 and 40 cm, for example of 30 cm x 30 cm) of the mounting target with the connection objects by means of a sensor, wherein object data are gradually collected by the sensor and combined to form a 3D point cloud;performing an object recognition method for recognizing the connection objects and detecting their positions;checking whether the detected connection objects enable the workpiece to be fastened to the mounting target according to a predetermined criterion;if the test is positive, fastening the workpiece using the connection objects.The method according to the invention has the advantages which have already been mentioned with respect to the device according to the invention. The connection objects mentioned are already arranged or attached to the vehicle underbody or other mounting target within the scope of the method.According to an embodiment which is also preferred here, a profile section sensor is used as the sensor, and a timing of a light source, preferably of a laser, of the profile section sensor is matched to the timing of the travel of the profile section sensor along the surface region of the mounting target.Here, in particular, the assembly object can be a chassis for a motor vehicle, on which a vehicle underbody element is mounted as a workpiece or a wheel arch shell is mounted as a workpiece.For use cases or application situations which can arise in the method and which are not explicitly described here, provision can be made for an error message and / or a request for inputting a user feedback to be output and / or for a default setting and / or a predetermined initial state to be set according to the method.The invention also includes the control device for the device. The control device can have a data processing device or a processor device which is configured to carry out an embodiment of the method according to the invention. For this purpose, the processor device can have at least one microprocessor and / or at least one microcontroller and / or at least one FPGA (field programmable gate array) and / or at least one DSP (digital signal processor). In particular, a CPU (central processing unit), a GPU (graphic processing unit) or an NPU (neural processing unit) can be used as the microprocessor in each case. Furthermore, the processor device can have program code which is configured to carry out the embodiment of the method according to the invention when executed by the processor device. The program code can be stored in a data memory of the processor device. The processor device can be based on at least one circuit board and / or on at least one SoC (system on chip), for example.The invention also includes developments of the method according to the invention, which have features as have already been described in connection with the developments of the device according to the invention. For this reason, the corresponding developments of the method according to the invention are not described again here.The motor vehicle to be constructed preferably with the inclusion of the mounting method is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus or motorcycle.As a further solution, the invention also comprises a computer-readable storage medium comprising program code which, when executed by a computer or a computer cluster, causes the latter to execute an embodiment of the method according to the invention. The storage medium may be provided at least partially as a non-volatile data memory (e.g. as a flash memory and / or as an SSD-solid state drive) and / or at least partially as a volatile data memory (e.g. as a RAM-random access memory). The storage medium can be arranged in the computer or computer network. However, the storage medium can also be operated, for example, as a so-called store server and / or cloud server on the Internet. The computer or computer network can provide a processor circuit with, for example, at least one microprocessor. The program code can be provided as binary code and / or as assembler code and / or as source code of a programming language (e.g. C) and / or as a program script (e.g. Python).The invention also includes the combinations of the features of the described embodiments. The invention therefore also comprises implementations which each have a combination of the features of a plurality of the described embodiments, provided that the embodiments have not been described as mutually exclusive.Exemplary embodiments of the invention are described below. Illustrated in this connection: FIG. 1 aschematically illustrates a running gear in the suspension and a device arranged therefor, with a workpiece to be attached to the running gear before the workpiece is attached, FIG. 1 bshows the arrangement from FIG. 1 ain the state in which the workpiece is guided to the chassis underbody, and FIG. 1 cshows the arrangement from FIG. 1 bin the situation in which the workpiece is fastened to the vehicle underbody; FIG. 2 shows a first example of an element to be attached to the chassis underbody; FIG. 3 ashows a second example of an element to be attached to the chassis underbody, and FIG. 3 bshows a supplementary view to FIG. 3 a; FIG. 4 ashows an example of a wheel arch shell to be attached to a wheel arch in a perspective overall view; FIG. 4 bshows the view according to the arrow IVb in FIG. 4 a; FIG. 4 cshows the view according to the arrow IVc in FIG. 4 a; and FIG. 5 shows the steps of an embodiment of the method according to the invention.The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that are to be considered independently of one another and that also develop the invention independently of one another. Therefore, the disclosure is intended to include combinations of the features of the embodiments other than those illustrated. Furthermore, the described embodiments can also be supplemented by further features of the invention that have already been described.In the figures, identical reference numerals designate functionally identical elements.A chassis denoted overall by 1 (almost finished vehicle, on which tires are also already attached, for example) is suspended, shown here only symbolically, and a workpiece 2 is to be attached to the underbody of the chassis. The device illustrated by the elements 10, 22, 24, 26 and 30, 32 serves this purpose.The apparatus comprises a data processing device 10 with a receiving device 12 and a control device 14 as well as the actual processor 16 for the data processing. The data processing device 10 is intended to communicate with the further components via a communication connection, which can be provided by means of cables or wirelessly. A movable (robot) arm 22, which may have a plurality of joints not shown in FIG. 1 a, carries a profile cut sensor 30. a second robot arm 24, which may likewise have a plurality of joints not shown in FIG. 1 a, carries the actual workpiece. Here, a plurality of robot arms can also carry the workpiece in a coordinated manner together. Finally, a further robot arm 26 is provided which carries a tool 32, which can also be a multifunction tool, wherein the tool can be selectively adjusted in order to bring about a connection of the workpiece 2 to the chassis base of the chassis 1.The profile section sensor 30 is now moved stepwise along the underbody of the chassis 1 with the aid of the first arm 22, and a height profile is recorded for a line in each step, received via the unit 12 and combined by the processor 16 to form a 3D point cloud. The sensor 30 travels on the vehicle underbody on the basis of control commands of the control device 14.Once the 3D point cloud has been created, the unit 16 of the functionality of an evaluation device also detects objects which have already been inserted or otherwise fastened to the chassis underbody of the chassis 1. If it is detected that these connecting elements are suitable for fastening the workpiece 2, the workpiece 2 is moved to the underbody by means of the support device 24 according to FIG. 1 band fastened in the next step according to FIG. 1 c by means of the robot arm 26 using the tool 32. In the exemplary case of FIG. 2, the chassis 1 is shown in perspective from below and a vehicle underbody 2 ais shown on the chassis as a workpiece to be mounted. Here, plastic nuts 3a and coarse threaded bolts 3b serve as connecting elements, wherein the coarse threaded bolts have been welded on beforehand.In the case of FIG. 3 a, another workpiece is attached to the underbody of the chassis 1, for example a lateral floor cladding. Here, (coarse thread) screws 3 c, which are screwed into snap nuts or spring nuts, which have been fastened beforehand to the vehicle floor, or plastic nuts 3 a, which are screwed onto (coarse thread) screw bolts, are used for fastening purposes, the latter having been welded beforehand to the floor floor.The side view of FIG. 3 billustrates that screw elements 3 dare also additionally introduced laterally, coarse threaded screws in particular being screwed into snap nuts which have been inserted onto the wheel arch shell.FIG. 4 ashows the wheel arch of the chassis 1, to which a wheel arch is to be attached as the workpiece 4. The situation illustrated here for only one side of the chassis can be found in mirror image form on the other side.FIG. 4 bshows the view according to the viewing direction shown by the arrow IVb FIG. 4 a. FIG. 4 cshows the view according to the viewing direction shown by the arrow IVc FIG. 4 a. These figures illustrate the connecting elements 3e and 3f. During the mounting on the wheel arch case, in contrast to that described above with reference to FIGS. 1 aand 1 b, the profile section sensor is guided on a circular path, in particular rotates about its axis.According to FIG. 5, the method according to the invention comprises, in step S 10, the provision of the chassis 1 in the suspension, in step S 12 the placement of the workpiece 2 in the device, comprises the step S 14 of moving the profile section sensor 30 along the underbody / wheel arch of the chassis, in step S 16 the acquisition of a 3D point cloud, in step S 18 the recognition of the pre-assembled connection objects, and in step S 20 the checking of whether the position and type of the connection objects are suitable for actually reliably fastening the workpiece placed in the device in step S 12, and in step S 22 the fastening of the workpiece to the vehicle underbody.Overall, the examples show how automated assembly of underbody elements can be provided by means of robot-assisted 3D point cloud creation.

Claims

Method for mounting a workpiece (2) on a mounting target (1), the device comprising: - a first movable unit, in particular designed as an arm (22), which carries a sensor for optically detecting object data; - a control device (14) for the first movable unit, which is designed to move the sensor) in steps along the mounting target (1) by control commands; - an evaluation device (16), which is coupled to the sensor and is designed to collect the object data from the sensor at each step and to obtain a total of 3D object data by associating it with the control commands and / or a detected position of the sensor; - wherein the evaluation device (16) is further configured to detect objects of at least one predetermined object type on the surface of the mounting target (1) on the basis of the 3D object data and to determine their respective position; wherein the device further comprises: - a support device (24, 26), preferably in the form with at least one second movable arm (24), wherein the support device (24, 26) has a known location assignment to the first movable unit and is configured to support the workpiece (2) and to add it to the mounting target (1) depending on the positions of the detected objects; - means (26; 32) for fastening the workpiece (2) to the mounting target (1) using the detected objects of the at least one predetermined object type.Device according to claim 1, wherein the evaluation device is designed to identify at least one of the following connection objects located on the surface of the mounting target: - snap nuts; - spring nuts; - split rivets; - split nuts; - coarse threaded bolts; and - stud bolts with metric threads.The apparatus of claim 1 or 2, wherein the sensor is a profile cut sensor (30) that acquires distance data along a line, respectively, thus outputting 2D object data, and that is movable by the arm perpendicular to the line.The device according to claim 3, wherein the control device (14) is designed to compare a timing of the guidance of a light source, preferably a laser, of the profile section sensor (30) along the line with the timing for moving the profile section sensor (30).Device according to any one of the preceding claims, in which the fixing means are part of the support device and preferably comprise a further movable arm (26).Apparatus according to one of the preceding claims, in which the evaluation device (16) is designed to check whether it is possible to fasten the workpiece (2) to the mounting target (1) using the detected objects of the predetermined object types and to cause the fastening means (26) to be activated only when the check is positively output.Method for mounting a workpiece on a mounting target, comprising the following steps: - providing the mounting target (1), in particular a chassis base or a wheel well, wherein a respective connection object (3a, 3b, 3c, 3d, 3e, 3f) is provided on a plurality of connection regions; - traversing a surface region of the mounting target (1) with the connection objects (3a, 3b, 3c, 3d, 3e, 3f) by means of a sensor, wherein object data are gradually collected by the sensor and combined to form a 3D point cloud; - carrying out an object recognition method for recognizing the connection objects (3a, 3b, 3c, 3d, 3e, 3f) and for detecting their positions; checking whether the detected connection objects (3a, 3b, 3c, 3d, 3e, 3f) enable the attachment of the workpiece (2) to the mounting target (1) according to a predetermined criterion; if the check assumes positive, attaching the workpiece using the connection objects (3a, 3b, 3c, 3d, 3e, 3f).Method according to claim 7, in which at least one of: - snap nut; - spring nut; - split riveting; - split nut; - coarse threaded bolt; and - stud bolt with metric thread is provided as connection objects.Method according to Claim 7 or 8, in which a profile section sensor (30) is used as a sensor, and in which a timing of a light source, preferably of a laser, of the profile section sensor (30) is matched to the timing of the travel of the profile section sensor (30) along the surface region of the mounting target (1).Method for mounting according to one of Claims 7 to 9, in which the mounting object (1) is a chassis for a motor vehicle, on which a subfloor element (2a) or a lateral floor cladding (2b) is mounted on a wheel arch shell (4) as a workpiece.Mounting method according to one of Claims 7 to 10, in which the device according to one of Claims 1 to 6 is used.

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