DE20220528U1 - Method for applying connecting fittings to workpiece using non calibrated sensors fitted to the operating tools and with the measured positions compared with reference positions - Google Patents

Abstract

A method for applying connecting fittings to a workpiece, e.g. a vehicle body shell, has a sensor system fitted to the operating tools and moved by robotics. The operating tools are brought into close proximity with their operating positions and the shape and position of the workpiece is compared with reference patterns. The final positioning of the tools w.r.t. the workpiece is via a simple shift control with repeated relative measurements until the optimum position is reached. The actual position measurements are via simple triangulation. No calibrated sensors are required. The automated processes include stamping and pressing.

Description

P801588/EN/2

DaimlerChrysler AG Dr.Närger

08.07.2003

Device for producing a connection area

on a workpiece

The invention relates to a device for producing a connection area on a workpiece, in particular a body part, according to the preamble of claim 1.

Connecting elements are inserted into vehicle bodies in the body shell or during assembly in different areas of the body, to which add-on parts are attached during vehicle assembly. In the interest of a high-quality appearance of the body, it is often necessary to align and position these add-on parts with high precision in relation to reference areas on the body series or other modules. In order to ensure such a high-precision alignment of the add-on parts on the body, the connecting elements must be positioned precisely in relation to the reference areas on the body.
25

For example, the rear lights on the body must be aligned with high precision relative to the body surfaces adjacent to the light in order to achieve kink-free mirror lines and uniform gaps and transitions in the rear side area of the body. Each of these rear lights is attached to the body using several (e.g. four) screws. In order to achieve a highly precise positioning of the rear light in its mount on the body, the corresponding connection areas must be introduced into the body in such a way that a highly precise alignment of the rear light relative to these

P801588/EN/2

- reference areas adjacent to the rear light.

In mass production, the connecting areas, typically consisting of a hump embossed into the body part as a stop surface and a hole punched into this hump for the fastening screw to pass through, are generally introduced into the body using a robot-guided embossing and punching tool. The bodies are fed to the tool on a conveyor belt, which is why there are variations in the position of the body compared to the robot-guided tool. Furthermore, due to production-related tolerances, the bodies show deviations from the target shape, which is specified, for example, by an internal computer (CAD) model. In order to be able to ensure a highly precise alignment of the rear light with respect to the reference areas on the body, a method and a device are therefore necessary with the help of which the robot-guided tool can be aligned and positioned with high precision with respect to the relevant reference areas of this body - regardless of the shape and spatial position of the respective body in the robot's working area - and which also allow a process-reliable introduction of the connecting areas in the spatial position defined by these reference areas.

DE 299 18 486 Ul discloses a method and a device for the precise shaping of a connecting area on a body component using a robot-guided stamping and punching tool. First, several measured values of the body component are recorded using a (e.g. optical) sensor system; based on these measured values, the absolute position of the supplied body component in the robot's work area is determined. The measured values are then compared with an "ideal model" of the area to be processed stored in the robot's control system, and the "ideal model" is shifted within the computer until

P801588/EN/2

t
>·
■ < *
ff &bull;
« * &bull; &bull; 4 ·
% * *
&bull; &bull; &bull;r 1 ·
·«

until a maximum overlap of the contours of the "ideal model" with the (actual) contour determined by measurement occurs. The robot-guided embossing and punching tool is then moved along a programmed path in relation to the body, in the course of which the connection points are introduced into the body.

The method known from DE 299 18 486 Ul is based on measuring the absolute position of the body in the robot's workspace. Therefore, several boundary conditions must be met for this method to be used successfully:

- First, the sensor system must be able to determine individual measured values metrically with respect to its internal reference coordinate system ("internal metric calibration of the sensor system").

- Furthermore, the position of the sensor system in the robot's workspace must be known ("external metric calibration of the sensor system").

- Finally, the sensor system must be able to take several individual measurements of the body in such a way

combine and condense so that the exact workpiece position in relation to the robot's workspace can be calculated consistently and reliably.
Experience has shown that the setup and calibration effort required for the sensors and the entire system to meet these conditions is very high and can only be carried out by experts. In addition, the required accuracy and reproducibility of the measured values can only be achieved by high-quality (and therefore expensive) sensors.

Furthermore, the evaluation method underlying DE 299 18 486 Ul for determining the body position relies on geometric model knowledge about the affected body areas (the "ideal model" mentioned above, for example the CAD model of the body). In order to avoid systematic errors, a clear assignment of measurement characteristics to the model knowledge must be ensured; this is usually

P801588/EN/2

involves a high additional algorithmic effort for the respective application.

A further disadvantage of the method known from DE 299 18 486 Ul is that the feature measurements are only carried out once per processing step. Even slight movements of the body during the positioning or processing process lead to large errors and must therefore be excluded.

The invention is therefore based on the object of proposing a device for the precise production of connection areas on a workpiece, in particular a vehicle body, which is associated with a significantly reduced calibration effort and which enables the use of significantly more cost-effective sensors. In addition, an increase in accuracy compared to conventional methods should be achieved.

0 The object is achieved according to the invention by the features of claim 1.

Then, a sensor system is used to position the machining tool relative to the body, which is permanently connected to the tool and forms a robot-controlled tool/sensor combination. This tool/sensor combination is first brought by the robot into a (fixed programmed, independent of the current position of the body) approximate position relative to the body and then, in the course of a control process, brought into a holding position (precisely aligned with the reference area on the body). In the control process, which moves the tool/sensor combination from the approximate position to the holding position, the sensor system
(Actual) measured values of the reference area on the body are generated; these (actual) measured values are compared with (target) measured values generated in a previous setup phase;

P801588/EN/2

The tool/sensor combination is then moved by a displacement vector (including linear displacements and/or rotations), which is calculated from the difference between the (actual) and (target) measured values using a so-called "Jacobi matrix" (or "sensitivity matrix"). Both the (target) measured values and the Jacobian matrix are determined in a setup phase - preceding the actual positioning and machining process - for the respective tool/sensor combination in combination with the body area to be machined. This setup phase is run through once when setting up a new combination of tool, sensor system, body type and machining problem.

Once the control process has been completed and the tool/sensor combination is in the desired holding position relative to the body, the actual machining of the body takes place. A robot-controlled machining program is run through to create the connection areas, using the holding position found during positioning as the reference position.

The control process, in the course of which the tool is brought from the (robot-controlled) approach position to the holding position (precisely aligned with the workpiece), differs fundamentally from the positioning process known from DE 299 18 486 Ul: While in the process of DE 299 18 486 Ul the absolute position of the workpiece in the robot's workspace is determined during positioning, which forms the basis for the further alignment of the tool, the present process is based on relative measurements, in the course of which information stored during the set-up phase - corresponding to a set of (target) measured values of the sensor system - is to be restored via the control process.

P801588/EN/2

This leads to two significant simplifications compared to the state of the art:

- Firstly, internal metric calibration of the sensors is no longer necessary, as the sensors used no longer "measure" but simply react to a monotonous incremental movement of the robot with a monotonous change in their sensor signal. This means, for example, that when using a CCD camera as a sensor, the camera's internal lens distortions do not need to be compensated, or that when using a triangulation sensor, the exact metric calculation of distance values is no longer necessary.

- Furthermore, external metric calibration of the sensors is no longer necessary: In contrast to the state of the art, the position of the sensors no longer has to be determined metrically in relation to the robot's workspace or the coordinate system of the robot hand in order to be able to calculate suitable corrective movements. The sensors only have to be attached to the tool in such a way that they can actually record suitable measurement data from the reference area of the body in their capture area.

The metric measurement function, which is usually only determined with great effort, can therefore be completely dispensed with when using the present method. This means that metrically uncalibrated sensors can also be used, which are much simpler and therefore cheaper than calibrated sensors. Both the instrument structure and the installation and operation of the entire system can therefore be implemented much more cost-effectively when using the present method. The sensor data evaluation is very simple and robust - especially when using point-measuring triangulation sensors. Furthermore, the initial setup and maintenance of the tool is drastically simplified when using the present method and can also be carried out by semi-skilled personnel.

P801588/EN/2

The result of the tool positioning is still independent of the absolute positioning accuracy of the robot used, since any robot inaccuracies are also corrected when approaching the target position. Due to the resulting short error chains, a very high repeat accuracy in the positioning result can be achieved if required.

The number of positional degrees of freedom that can be compensated for in the positioning phase using the present method is freely selectable and depends only on the configuration of the sensor system. The number of sensors used is also freely selectable. The number of (scalar) sensor information provided only has to be equal to or greater than the number of degrees of freedom to be controlled. In particular, a larger number of sensors can be provided and the redundant sensor information can be used, e.g. to better detect shape errors in the body area under consideration or to improve the accuracy of the positioning process. Finally, sensor information from different sources can be used (e.g. a combination of CCD cameras and distance sensors or a combination of distance sensors and force-torque sensors).

The present method can be adapted very easily to new problems, since only the acquisition and processing of sensor data, not the control system core, needs to be adapted. The use of model knowledge about the body areas to be processed, which plays a decisive role in calculating the absolute position in the method of DE 299 18 486 Ul, can be dispensed with.

In comparison to the method known from DE 299 18 486 Ul, the present method allows a much faster compensation of residual uncertainties that arise when positioning the tool in relation to the body -

P801588/EN/2

due to position errors of the body relative to the tool caused by the conveyor technology and/or due to shape errors within the reference area on the body itself (due to component tolerances). Due to the rapid control of the tool position relative to the workpiece, the workpiece does not need to be clamped stationary during the positioning and machining process, but can be moved relative to the robot (for example on an assembly line or other suitable conveyor technology). This enables a high degree of flexibility of the present method, which can therefore be applied to a wide variety of applications for the machining and/or measurement of stationary and moving workpieces.

The controlled approach to the lead position can take place in a single control loop; however, it is advantageous to use an iterative process in which threshold values are specified as termination criteria: The iteration process is terminated if the deviation between the (target) measured value and the (actual) measured value is below a specified threshold value; the iteration process is also terminated if the reduction in the deviation between the (target) measured value and the (actual) measured value to be achieved in successive iteration steps is below a further specified threshold value.

The positioning of the tool/sensor combination and the machining of the body by the tool can be carried out either sequentially one after the other or overlapping one another. This means that when using the present method, position and shape errors of bodies can be easily compensated before or during machining. This means that the method can also be used for machining moving bodies. In this case, however, the sensor system in the tool/sensor combination must be arranged in such a way relative to the tool that the sensor system can also be used during the machining phase in such a way that the sensor system can be used in such a way that the tool can also be used during the machining phase.

P801588/EN/2

compared to the reference area on the body so that usable (actual) measurement values can be recorded.

Further advantageous embodiments of the invention are
The invention is described below with reference to two embodiments shown in the drawings.
explained in more detail; showing:

Fig. 1 a rear section of a vehicle body in
perspective representation;

Fig. 2 is a schematic side view of a tool/

Sensor assembly in a forward position relative to the vehicle body;

Fig. 3 is a schematic representation of a path of a robot hand during the processing of a machining task.

task;

Fig. 4 a schematic representation of selected positions of the tool/sensor combination during passage
of the process flow of Figure 3:
Fig. 4a: Retreat position

Fig. 4b: Approach position
Fig. 4c: Lead position
Fig. 4d: Processing position

Figure 1 shows a rear cutout 2 of a vehicle body shell 1 with a rear light area 3 in which a rear light (not shown in Figure 1) is to be mounted. For precise mounting of the rear light, four connection areas 4 (indicated by dashed lines in Figure 1) are provided in the rear light area 3, to which the rear light is to be attached using screw connections. Each connection area 4 comprises an embossed stop surface 5 against which the rear light rests when installed, and a punched hole 6 for the passage of a fastening screw. The relative position of the four stop surfaces 5 and the four holes 6 is defined by the geometry of the rear light to be installed.

P801588/EN/2

and is therefore constant (for a given body type).

In order to ensure a high-quality visual impression of the body 1, the rear light must be precisely aligned (in terms of position and angle) with respect to a side wall area 7 of the body 1 adjacent to the rear light area 3; this means that the four connecting areas 4 (each consisting of a stop surface 5 and a punch hole 6) must be positioned with high precision with respect to this side wall area 7 and the rear light area 3. The side wall area 7 and the rear light area 3 together thus form a so-called reference area 8 for aligning the tool 9 with respect to the body 1.

To produce the connecting areas 4, a robot-guided embossing/punching tool 9 (shown schematically in Figure 2) with an embossing/punching pliers 9' is used, with the aid of which the connecting area 4 (i.e. stop surface 0 5 and hole 6) can be produced in a single process step; details regarding the structure and mode of operation of such an embossing/punching tool 9 are described, for example, in DE 299 18 486 Ul. This embossing/punching tool 9 is attached to the hand 10 of an industrial robot 11, which is provided with a control device 12 for controlling the position of the robot hand 10 and for controlling the movement of the embossing/punching tool 9. To measure the position and alignment of the rear light area 3 and the adjacent side wall areas 7, the robot hand 10 also carries a sensor system 13 with several (two in the schematic representation of Figure 2) sensors 14, which are rigidly connected to the embossing-punching tool 9 via a rod 15 and thus form a structural unit with the tool 9, the so-called tool/sensor combination 16. With the help of this sensor system 13 - as described below - the embossing/punching tool 9 is controlled in an iterative control process.

P801588/EN/2

aligned with the side wall area 7 and the rear light area 3 as reference areas 8.

If the embossing/punching tool 9 is to be set up for a new processing task - for example, the processing of a new vehicle type or a new area on the body 1 - then a so-called setup phase must first be run through, in which a suitable sensor system 13 is selected and configured with the tool 9 to form a tool/sensor combination 16. Following this, (target) measured values of this sensor system 13 are recorded in the reference areas 8. After the setup phase has ended, the tool/sensor combination 16 configured and calibrated in this way is now ready for series use, in which a so-called work phase is run through for each body 1 fed into the work area 23 of the robot 11. These two different phases are shown below:

Setup phase:

To solve a newly set processing task, a sensor system 13 adapted to the processing task is selected in a first step. This sensor system 13 is attached to the robot hand 10 in a (freely selected) holding position 18 of the tool/sensor combination and is aligned in such a way with respect to a ("master") body 1' in the work space 23 of the robot 11 that the sensors 14 are directed at suitable reference areas 8' of the body 1' adapted to the respective processing task.

In Figure 2, the tool/sensor combination 16 is shown in the holding position 18 opposite the body 1'. The two sensors 14 are directed at sections 17 of the reference area 8' on the body 1', which are selected

P801588/EN/2

are such that they are of particularly high importance for the position and alignment of the areas to be machined with the tool 9. In the specific embodiment of the machining of the rear light area 3 (Figure 1), an assembly of eight optical (triangulation) sensors 14' is used as the sensor system 13, which are directed at different sections 17' of the rear side wall 7 and the rear light area 3. The sensors 14,14' provide measured values which correspond to distance values between the respective individual sensor 14,14' and the environment 17,17' of the reference area 8 opposite the sensor 14,14'. The number of individual sensors 14,14' and the environments 17,17' to which they are directed are selected in such a way that they allow the best possible characterization of the reference surfaces 8' relevant for the respective application (in this case the rear side wall 7 and the rear light area 3).

The sensor system 13 rigidly connected to the tool 9 is now "taught" in this holding position 18 with the help of the robot 11 to the reference area 8' of the body 1'. In this process, the (target) sensor measurement values are first recorded in the holding position 18. Then - starting from the holding position 18 - with the help of the robot 11, the position of the tool/sensor combination 16 relative to the body 1 is systematically changed along known travel paths - as indicated in Figure 2 by arrows 2 6; as a rule, these are incremental movements of the robot 11 in its degrees of freedom. The changes in the measurement values of the sensors 14 that occur are recorded (completely or in part). From this sensor information - in a known manner - a so-called Jacobian matrix (sensitivity matrix) is calculated, which shows the relationship between the incremental movements of the robot 11 and the resulting 5 changes in the sensor measurements. The method for determining the Jacobian matrix is described, for example, in "A tutorial on visual servo control" by S. Hutchinson, G.

P801588/EN/2

Hager and P. Corke, IEEE Transactions on Robotics and Automation 12(5), October 1996, pages 651-670. This article also describes the requirements for the travel paths and the measurement environments (continuity, monotonicity, ...) that must be met in order to obtain a valid Jacobian matrix. - The tool 9 is attached to the robot hand 10 in such a way that no collisions between the tool 9 and the body 1 can occur during this setup process.

The target values and the Jacobian matrix generated in the setup phase are stored in an evaluation unit 2 0 of the sensor system 13 and form the basis for the subsequent control process in the positioning phase.

Furthermore, in the setup phase, a travel path 21 of the robot hand 10 (and thus of the tool/sensor combination 16) is generated, which is controlled during the later work phase. This travel path 21 is shown schematically in Figure 3. The starting point of the travel path 21 is a so-called "retraction position" 22, which is selected so that a new body 1 can be introduced into the work space 23 of the robot 11 without collisions between the body 1 and the tool 9 or the sensor system 13 occurring.

Starting from this retraction position 22, the travel path 21 comprises four separate sections:

I. The tool/sensor combination 16 is moved on a controlled path I from the retraction position 22 to a so-called "approach position" 24, which is selected such that all individual sensors 14 of the sensor system 13 can record valid measured values in the sections 17 of the reference area 8.

II. The tool/sensor combination 16 is moved on a controlled path II from the approach position 24 to the (as described above "learned") lead position 18, in which the tool/sensor combination

P801588/EN/2

16 is precisely aligned in position and angle with respect to the reference area 8 of the body 1.

III. The tool/sensor combination 16 is guided on a controlled path III from the holding position 18 to those processing areas (e.g. points 4 of the rear light area 3) where the connection points 4 are created. The embossing/punching pliers 9' are activated at each connection point 4 in order to emboss a stop surface 5 and punch a hole 6 in this position. This part III of the travel path can be taught in on a master part, for example, using a teach-in process.

IV. The tool/sensor assembly 16 is moved back to the retraction position 22 on a path IV.

The travel path 21 generated during the set-up phase thus consists of three sections I, III and IV which are to be traversed in a controlled manner, as well as one section II which is to be traversed in a regulated manner.

Working phase

In the working phase, the robot's workspace 23 is assigned 11

sequentially fed to bodies 1, and for each body

1, the travel path 21 generated in the setup phase is traversed.

P801588/EN/2

Track section I:

While the new body 1 is being fed in, the tool/sensor combination 16 is in the retraction position 22 (see Figure 4a). As soon as the new body 1 has been moved into the work area 23, the tool/sensor combination 16 is moved to the approach position 24 under the control of the robot hand 10 (see Figure 4b).

Trajectory section II (positioning phase):

Starting from the approach position 24, a positioning phase (path section II in Figure 3) is run through, during which the tool/sensor combination 16 is brought into the lead position 18 (taught during the teach-in phase) relative to the body 1 and is precisely aligned relative to the reference area 8 of the body 1. For this purpose, the sensors 14 of the sensor system 13 record measured values of the reference area 8. With the help of these measured values and 0 of the Jacobian matrix known from the setup phase, a movement increment (displacement vector) is calculated which reduces the difference between the current (actual) sensor measured values and the (target) sensor measured values. The tool/sensor combination 16 is then moved and/or swiveled by this movement increment with the help of the robot 11, and new (actual) sensor measured values are recorded during the ongoing movement.

This iterative measuring and shifting process is repeated in a control loop until the difference between the current (actual) and the desired (target) sensor measurement values falls below a specified error level, or until this difference no longer changes beyond a threshold value set in advance. The tool/sensor combination 16 is now (within the accuracy specified by the error level or threshold value) in the (in Figure

·

P801588/EN/2 .. ....

4c) relative to the reference area 8 on the body 1.

The iterative minimization carried out in the positioning phase simultaneously compensates for inaccuracies in the body 1 with regard to its position and alignment in the work area 23 of the robot 11 as well as any shape errors in the body 1 (or in the reference area 8). For the separate detection and evaluation of shape errors, additional sensors 14 can be provided, the measured values of which are used exclusively or partially to detect the shape errors. Furthermore, the measured values of the individual sensors 14 can be provided with different weighting factors in order to bring about a weighted position optimization of the tool/sensor combination 16 with respect to the reference area 8 of the body 1.

The position and angle shift of the tool/sensor combination 16 (corresponding to the shift between the approach position 24 and the lead position 18) that occurs during the control process of the positioning phase can be passed on to the control system 12 of the robot 11 in the form of a so-called zero point correction. The control system 12 of the robot 11 thus knows the initial position (corresponding to the lead position 18) from which the processing phase should begin. An important property of this positioning phase is its independence from the robot accuracy: Since the positioning process is based on an iterative comparison of the (actual) measured values with (target) measured values, any positioning inaccuracy of the robot 11 is immediately compensated by the iterative control process.

(Note: If the reference area 8 of the body 1 now located in the workspace 23 of the robot 11 corresponds in terms of position and shape to the reference area 8' of the ("master") body 1', based on which the system was taught in the setup phase, the approximate position

P801588/DE/2 « ·* ·&diams;·»·;,'%**·;

tion 24 corresponds to the lead position 18, so that no zero point correction of the tool/sensor combination 16 is necessary. )

Track section III (processing phase):

In the actual processing phase that follows, the tool/sensor combination 16 - starting from the holding position 18 - is moved in a controlled manner along the pre-programmed processing path (path section III in Figure 3). In the present exemplary embodiment, the tool/sensor combination 16 is first brought into a position such that the embossing/punching pliers 9' come to rest in a first processing point 25 of the rear light area 3 (see Figure 4d). The embossing/punching pliers 9' are then activated in a controlled manner so that the stop surface 5 is formed and the hole 6 is punched out. The three further processing points 25' of the rear light area 3 are then approached one after the other and provided with stop surfaces 5 and punch holes 6.

Track section IV:

After completion of the processing phase III, the tool/sensor assembly 16 is moved back into the retraction position 22 in a controlled manner. The processed body 1 can now be removed from the work area 23 of the robot 11 and a new body 1 can be fed in for processing.

For communication between the evaluation unit 20 of the sensor system 13 and the control unit 12 of the robot 11, a TCP/IP interface is advantageously used in the present embodiment, which enables a high data rate. Such a high data rate is necessary in order to be able to control the entire system (sensor system/robot) in six degrees of freedom with eight individual sensors 14' in the interpolation cycle of the robot 11 (typically 12 milliseconds). For control problems of lower complexity,

P801588/EN/2

xity - i.e. with lower requirements for accuracy and longer control times - the control can also be implemented via a conventional serial interface.

The embodiment of Figure 1, in which eight optical distance sensors (triangulation sensors) 14' directed at different areas 8 of the body 1 are used to position the tool/sensor combination 16, is designed so that the permissible maximum values for the position correction (and thus the maximum permissible spatial difference between the controlled approach position and the controlled advance position) are 5 mm in translation in X, Y and Z and 1° in each of the three solid angles. This means that the body 1 must be fed into the work area 23 of the robot 11 with a higher accuracy than these maximum deviations. Threshold values of 0.1 mm to 0.2 mm for the translational (X, Y, Z) deviation and 0.03° for the rotational deviation have proven to be a suitable termination criterion for the control process in the positioning phase.

In the previous description, the special case of machining the rear light cutout 2 on a body 1 was described, whereby the robot-guided tool/sensor combination 16 is aligned with high precision relative to the adjacent side wall area 7 and the rear light area 3 as reference areas 8. Of course, other body areas (e.g. adjacent trunk cutout, bumper mount, etc.) can also be used as reference areas for aligning the tool/sensor combination 16 on the rear cutout 2. Furthermore, the method can be transferred to the machining of any other body areas (fastening area for bumper, front module, ...) which must be machined in a precise position relative to a reference area 8. Finally, the method is not limited to the machining of bodies 1, but can basically be applied to any manufacturing problems in which a robot-guided tool/sensor combination 16 is used.

P801588/EN/2 .. . ..

guided machining tool 9 is to be positioned correctly relative to a reference area 8 of a workpiece.

Furthermore, it is possible to use one and the same robot-guided processing tool 9 to process the rear light areas 3 of different body types, which can be very different in terms of their geometric design (shape and position of the reference areas 8, number and position of the connecting areas 4, etc.). In this case, the sensor system 13 comprises, in addition to the sensors 14 (which are used for positioning the tool/sensor combination 16 relative to the first body type 1), further sensors 14" with the aid of which the tool/sensor combination 16 is positioned relative to the reference areas of the second body type; this second set of sensors 14" is indicated by dashed lines in the schematic representation of Figures 4a to 4d. The sensors 14" used for positioning the tool/sensor combination 16 relative to the second body type 0 can differ greatly from the sensors 14 in terms of their number, spatial orientation, measuring principle, etc. If a body 1 of the first type is fed into the work area 23, the tool/sensor combination 16 is moved from the retraction position 22 into the approach position 24 described above, in which (as shown in Figure 4b) the sensors 14 are directed towards the reference areas 8; the subsequent positioning process uses the measured values of the sensors 14 to bring the tool/sensor combination 16 into the holding position 18 (see Figure 4c), whereupon the processing phase corresponding to the first body type is carried out. If, on the other hand, a body of the second type is fed into the work area 23, the tool/sensor combination 16 is moved from the retraction position 22 into a position (not shown in Figure 4b). shown) approach position in which the sensors 14" are directed to the relevant reference areas of the second body type; in the subsequent positioning process, the measured values of the

P801588/EN/2

Sensors 14" are used to bring the tool/sensor combination 16 into the holding position corresponding to this body type, and then the processing phase corresponding to the second body type is carried out. The sensor groups 14 and 14" do not have to be disjoint, but it is quite possible to use some of the sensors 14, 14" for positioning both in relation to the first body type and in relation to the second body type.

In addition to machining different body types with a common tool/sensor assembly 16 with sensor groups 14 and 14", it is also possible to machine different areas (e.g. rear light area 3 and bumper attachment area) of one and the same body type with a common tool/sensor assembly 16. The group of sensors 14 is then used to position the tool/sensor assembly 16 relative to the reference area 8 of the rear light area 3, while the group of sensors 14" is used to position the tool/sensor assembly 16 0 relative to the reference area of the bumper, and in the respective machining phases the machining phases associated with the different areas are carried out.

So far, an application has been considered in which the body 1 is fed to the work area 23 of the robot 11 with the aid of a suitable conveyor system (for example on a transport carriage on a roller conveyor), but is then decoupled from the conveyor system and is therefore in a stationary position relative to the work area 23 during tool positioning and processing. Such a stationary mounting of the body 1 relative to the work area 23 is not necessary, however: The rapid control of the tool position described above can be modified in such a way that the sensors 14 compensate for changes in the position of the body 1 online, so that the tool/sensor combination follows the body 1. In this

P801588/DE/2 « _# ».· ·» ·--;

In this case, the embossing/punching pliers 9' of the embossing/punching tool 9 are mounted so that they can be moved and/or pivoted relative to the robot hand 10, so that the embossing/punching pliers 9' can be moved and/or pivoted relative to the sensor system 13 in a controlled manner. Such a movable mounting of the embossing/punching pliers 9' allows the machining phase (section III) to be carried out in such a position of the tool/sensor combination 16 that the sensor system 13 - regardless of the progress of the machining process - is aligned with the reference area 8 of the body 1. Since the sensor system 13 is aligned with the reference area 8 of the body 1 during the entire machining phase, changes in the position and alignment of the body 1 can be detected during the process; The position and alignment of the tool/sensor combination can then be held in a holding position 18 relative to the (moving) body 1 by applying the above-mentioned control method, so that the tool/sensor combination follows the movements of the body 1. The body 1 therefore does not need to be clamped in a stationary position during the positioning and processing process, but can move relative to the (possibly moving) robot 11 (for example by further transport on the assembly line). This only requires that changes in the relative position between the body 1 and the robot 11 5 take place more slowly than the measurement and position control of the tool/sensor combination relative to the body 1.

In addition to the (laser) triangulation sensors 14' specifically described above, other optical sensors can also be used as sensors 14 for detecting the actual position of the tool 9 in relation to the reference area 8. For example, area-measuring CCD cameras can be used as sensors, with the help of which (in combination with suitable image evaluation algorithms) the spatial positions of edges, holes 5, etc. can be generated as measurement variables. In principle, any tactile and/or non-contact measuring systems can be used.

P801588/EN/2

The selection of suitable sensors depends heavily on the specific application.

In addition to the robot-guided embossing/punching tool described in the application examples, the invention can be applied to a wide range of robot-guided processing tools. In the context of the present application, "robot-guided" tools are generally understood to mean tools that are mounted on a multi-axis manipulator, in particular a six-axis industrial robot 11.

Claims (3)

1. Device for producing a connection area ( 4 ) on a workpiece ( 1 ), in particular a body part, - with a machining tool ( 9 ) guided by a robot ( 11 ), - with a sensor system ( 13 ) which is firmly connected to the processing tool ( 9 ) and comprises at least one sensor ( 14 , 14 ', 14 "), - with a control device for controlling the robot ( 11 ) and the processing tool ( 9 ), - and with an evaluation unit ( 20 ) for evaluating the measured values of the sensor system ( 13 ) characterized ,
that at least one of the sensors ( 14 , 14 ', 14 ") is a metrically uncalibrated sensor. 2. Device according to claim 1, characterized in that an embossing/punching tool is used as the processing tool ( 9 ). 3. Device according to claim 1 or 2, characterized in that the at least one sensor ( 14 , 14 ', 14 ") is a point-measuring triangulation sensor.