Calibration procedure for robot systems

Abstract

System for calibrating a multi-robot system, comprising: a robot simulation device (30) with a processor (31) configured therein to generate a simulation workstation (34) based on a predefined arrangement of a real robot workstation (10), wherein the robot simulation device (30) communicates with a robot controller (20) that controls robots (11, 12, 13, 14, 15, 16) at the real robot workstation (10); and a software program (33) executed by the robot simulation device (30) and / or the robot controller (20) to calculate a part tracking offset between the simulation workstation (34) and the real robot workstation (10), wherein the robot controller (20) uses the part tracking offset to control the robots (11, 12, 13, 14, 15, 16); and the robot simulation device (30) calculates the part tracking offset in response to a tool of the real robot workstation (10) touching an identifiable point on a workpiece (50) in a first and a second position of the workpiece (50) in the real robot workstation (10) and pivoting the tool into a third position in a direction perpendicular to a direction of movement of the workpiece (50) through the real robot workstation (10).

Description

FIELD OF THE INVENTION

[0001] This invention relates to a method for calibrating a system of multiple robots in a production plant. BACKGROUND OF THE INVENTION

[0002] Currently, graphical, computer-independent programming solutions simplify the development of teach-in procedures for robot trajectories and painting processes. These solutions are specifically designed to generate robot trajectories that can be used by application software for robot controllers. These solutions include calibration features that calculate offset data and provide the user with a method for manually shifting or offsetting the taught trajectories.

[0003] Current designs of robots used for painting processes generally provide tracking frames and user-defined frames for globally adjusting taught points at runtime. However, frames typically need to be calculated and manually adjusted by the user. In non-painting systems, vision is sometimes used to assist the user in this task.

[0004] In addition, computer-independent simulation solutions can include calibration utilities to calculate offset data based on teach-in and paint touch-up points on a simulated CAD model of the part to be painted. However, existing calibration utilities only provide the user with offset data for manual application to the robot's taught trajectories. Furthermore, the offset data provided by existing calibration utilities may not be expressed in the correct data block.

[0005] Finally, calibration utilities are known for calculating stationary frames at robot workstations used in a production setting. However, these calibration utilities are only suitable for calculating frames or fixed workpieces in defined work areas and do not consider a workpiece moving on a conveyor. Current calibration utilities also use special tools or hardware to perform the calibration.

[0006] Such a calibration utility for calibrating multiple robots is known, for example, from US 2010 / 0 262 288 A1.

[0007] The prior art was inadequate in several respects. First, known calibration utilities are highly limited because they require at least some amount of manual calculation on the part by the user. Second, in a paint shop, methods incorporating vision to assist a user with known calibration are not always feasible due to the hazardous paint environment and the limited field of view of a camera. Third, the entire calibration utility can be quite costly because current calibration utilities require specialized hardware. Fourth, existing calibration techniques that truly calculate frames and offsets do not properly represent a workpiece on a moving conveyor. It would be advantageous if systems and methods for calibrating a robot could be improved. SUMMARY OF THE INVENTION

[0008] According to the present disclosure, an improved system and method for calibrating a multiple robot system was surprisingly discovered.

[0009] According to one embodiment of the invention, a system for calibrating a multiple robot system is disclosed. The system comprises a robot simulation device having a processor arranged therein and configured to create a simulation workstation of an operation of a real robot workstation, wherein the robot simulation device is configured to communicate with a real robot controller; and a software program executed by the robot simulation device and / or the real robot controller for calculating a component that is synchronized between the simulation workstation and the real robot workstation.

[0010] According to a further embodiment, a method for calibrating a multiple robot system comprises the steps of: generating a simulation workstation of the operation of a real robot workstation by a robot simulation device, wherein the simulation workstation is based on a predetermined implementation of the real robot workstation; establishing tracking frames at the simulation workstation by the robot simulation device; determining, by a real robot controller, whether a deviation exists between the simulation workstation and the real robot workstation; and executing a frame calibration and / or a calibration trajectory by the real robot controller to calibrate the simulation workstation with the real robot workstation.

[0011] According to yet another embodiment, a method for calibrating a multiple robot system comprises the steps of: generating a simulation workstation of an operation of a real robot workstation by a robot simulation device, wherein the simulation workstation is based on a predetermined arrangement of the real robot workstation; establishing tracking frames at the simulation workstation by the robot simulation device; determining, by a real robot controller, whether there is a deviation between the simulation workstation and the real robot workstation; executing a frame calibration and / or a calibration trajectory by the real robot controller to calibrate the simulation workstation with the real robot workstation; moving, by the robot simulation device, the simulation workstation so that it substantially corresponds to the real robot workstation;and calculating a part tracking offset by the robot simulation device based on the displacement of the simulation workstation; DESCRIPTION OF THE DRAWINGS

[0012] The above-mentioned and other advantages of the present invention will be readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in light of the accompanying drawings in which: Fig. 1 is a schematic block diagram of a system for carrying out the method according to an embodiment of the invention; Fig. 2 shows the flowchart of a method for calibrating a multiple robot system according to the invention; Fig. 3 is a schematic plan view of the method for defining tracking frames according to an embodiment of the invention; Fig. 4 is a flowchart of a method for teaching nominal tracking frames according to an embodiment of the invention; Fig. 5 an exemplary, schematic representation in plan view of the teaching of the nominal tracking frame according to the method of Fig. 4; and Fig. 6 is an exemplary perspective view of a simulation workstation used to calculate a part tracking offset according to the embodiment of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENT

[0013] The following detailed description and accompanying drawings describe and illustrate various exemplary embodiments of the invention. The description and drawings are provided to enable one skilled in the art to make and use the invention and are not intended to limit the scope of the invention in any way. With respect to the disclosed methods, the steps depicted are exemplary in nature, and thus, the order of the steps is not required or critical.

[0014] Fig. 1 is a schematic block diagram of a system for performing the method according to one embodiment of the invention. A real robot workstation 10 facilitates the execution of a robotic manufacturing process. Fig. In the embodiment illustrated in Figure 1, the actual robot workstation 10 schematically represents a paint booth workstation. However, the actual robot workstation 10 can be a workstation for any manufacturing process as needed. The actual robot workstation 10 can include a plurality of robots 11, 12, 13, 14, 15, 16, which are controlled and monitored by a robot controller 20. The robots 11, 12, 13, 14, 15, 16 can be painting robots, vehicle door opening robots, hood opening robots, trunk opening robots, or any robot used to perform any other application as needed. While in Fig. 1 six robots 11, 12, 13, 14, 15, 16 are shown, the actual robot workstation 10 may additionally include any number of robots, such as any number of robots less than or more than six robots.

[0015] With continued reference to Fig. 1, two of the robots 11, 12 are connected to a control unit #1 17 of the robot controller 20. Two of the robots 13, 14 are connected to a control unit #2 18 of the robot controller 20. Two of the robots 15, 16 are connected to a control unit #3 19 of the robot controller 20. It will be understood that, as needed, any number of robots can be connected to each of the control units to coordinate the operation of one or more robots. Furthermore, as needed, any number of control units can be used to coordinate the operation of one or more robots. The control units 17, 18, 19 can communicate directly or indirectly through a communication protocol for the coordinated operation of the robots 11, 12, 13, 14, 15, 16 to perform a selected process, such as a painting process. The control units 17, 18, 19 can communicate wired or wirelessly through any network as required.For example, the control units 17, 18, 19, as in . Fig. 1, communicate via an Ethernet network 26.

[0016] The robot controller 20 includes a data storage device 22 for receiving and storing data communicated from the control units 17, 18, 19. The data storage device 22 is also capable of being connected to the real robot workstation 10 and a robot simulation device 30 positioned outside the real robot workstation 10. The robot simulation device 30 is a device used to simulate the operation of the robots 11, 12, 13, 14, 15, 16 and to facilitate the achievement of optimal displacement and movement of the robots 11, 12, 13, 14, 15, 16. The robot simulation device 30 has a processor 31 and a memory 32. Although it is Fig. 1, the robot simulation device 30 may further include user input devices for inputting data for editing, correcting, instructing, etc. of the user and a display for simultaneously displaying, as needed, three-dimensional simulations of the robots 11, 12, 13, 14, 15, 16, a workpiece 50 ( Fig. 3) or any other device within the real robot workstation 10.

[0017] The processor 31 is instructed by the software program 33 stored in the robot simulation device 30 to generate a computer-independent design of a simulation workstation as data 34, which is communicated with the control units 17, 18, 19 of the robot controller 20. The software program 33 can be any software program designed to simulate a three-dimensional robot workstation or any other software program that is CAD-compatible and can simulate the operation of a multi-robot workstation. Other data can be transferred between the robot simulation device 30 and the data storage device 22 of the robot controller 20. The data can include frame calibration data 35, trajectory calibration data 36, ​​or any other data as needed to facilitate the generation and calibration of trajectories for multi-robot systems.In addition, the software program 33 can calculate data 37 of a part tracking offset, which can then be downloaded into the data storage device 22 for use by the control units 17, 18, 19.

[0018] According to Fig. 2, a method for calibrating a multiple robot system is provided. In a step 100, the simulation workstation 34 is generated computer-independently, separately from the robot controller 20 of the workstation frame 10 of the real robot workstation, which operates in real time. The simulation workstation 34 is a predetermined, simulated arrangement of any fixtures at the real robot workstation 10 based on drawings and plans of the manufacturing facility imported from CAD models into the robot simulation device 30. This predetermined, simulated arrangement represents an "ideal" assembly or arrangement based on assembly drawings before deviations can occur at any point in the robot manufacturing process during an actual assembly of all fixtures at the real robot workstation 10.Depending on requirements, the simulation workstation 34 can be constructed at any time, such as before, during or after assembly of the real robot workstation 10 at a point in the robot manufacturing process.

[0019] Fig. 3 is a schematic top view of tracking frame calculation, step 110, according to one embodiment of the invention. The diagram is the simulation workstation 34, which represents what the actual robot workstation 10 should look like in real time according to the specified layout. This simulation workstation 34 is an example of what can be displayed on the robot simulation device 30. The example simulation workstation 34 illustrates the workpiece 50 arranged on a conveyor 54 and the robots 11, 12, 13, 14, 15, 16 working within an operating area 52. The workpiece 50 shown is a vehicle body, specifically a car body according to a type or model of vehicle bodies. The workpiece 50 can be exchanged to be any type of vehicle body according to any type or model of vehicle.The robots 11, 12, 13, 14, 15, 16 can be programmed to perform the desired operation on the workpiece 50 as required.

[0020] Once the simulation workstation 34 has been constructed, in step 110, tracking frames such as a nominal tracking frame for each of the robots 11, 12, 13, 14, 15, 16 and a workstation frame are set up by the off-line robot simulation device 30. The off-line simulation device 30 can establish any location on the simulation workstation 34 corresponding to the workstation frame as needed. In a non-limiting example, as in Fig. 3, the work frame on the simulation workstation 34 can be set up to locate the workpiece 50 at a predetermined position 56 as it is moved along the conveyor 54. Position 56 can be set when the workpiece 50 reaches a component detector switch (not shown) before entering the service area 52. The component detector switch signals the position of the workpiece 50 so that the control units 17, 18, 19 begin controlling the robots 11, 12, 13, 14, 15, 16 to perform the process.

[0021] In a step 120, the data of the simulation workstation 34, generated computer-independently in step 110 during the calculation of the tracking frames, is stored in a tracking data file stored in the robot simulation device 30. In a step 130, the tracking data file containing the data 34 of the simulation workstation is transferred or downloaded to the data storage device 22 of the robot controller 20 for communication with the control units 17, 18, 19 of the robots 11, 12, 13, 14, 15, 16. The file can be in any file format designed to be compatible for reading and writing by both the robot simulation device 30 and the control units 17, 18, 19, such as, for example, an XML data file.

[0022] In step 140, assembly data is confirmed in the robot controller 20. In step 150, the current assembly of the robot workstation 10 is compared with the simulation workstation 34, which was set up based on the "ideal" assembly, to determine whether there is a deviation between the robot workstation 10 and the simulation workstation 34. If the configuration of the simulation workstation 34 is not close enough to the configuration of the actual robot workstation 10, the frame calibration procedure 35 is performed in steps 160 and 170. If the current assembly of the robot workstation 10 is close enough to the "ideal" assembly, the calibration trajectory 36 can be taught, as shown in step 180.

[0023] In step 160, nominal tracking frames for each robot 11, 12, 13, 14, 15, 16 are taught in real time at the real robot workstation 10 by the robot controller 20. The nominal tracking frames for each robot 11, 12, 13, 14, 15, 16 are taught by a user via a robot teach-in program. The teach-in program includes calculating an offset. The robot controller 20 executes a method for setting a workstation frame of the real robot workstation 10. The workstation frame is any position on the real robot workstation 10 where the same nominal tracking frame is set up for each robot 11, 12, 13, 14, 15, 16. This same location becomes the location of the workstation frame in the robot controller 20 for the purpose of establishing a common workstation frame across all robot controllers 17, 18, 19.To achieve a result in which the nominal tracking frame is the same position for each robot 11, 12, 13, 14, 15, 16, any method can be used as needed. The actual position where the work frame is set up is not critical and can be chosen as needed. In a non-limiting example, as shown in . Fig. 3, the work frame can be selected to be located at a usual location 58 where a longitudinal center line c of the conveyor 54 intersects an axis a of the world coordinate origin of the first upstream robot 11 with respect to a direction of movement 60 of the workpiece 50 on the conveyor 54. Therefore, the nominal tracking frame for each robot 11, 12, 13, 14, 15, 16 can be taught as if it were located at the usual location 58 of the work frame. It will be understood that any position can be selected as the work frame as needed.

[0024] As in Fig. 4 and Fig. 5, a nominal tracking frame teach-in procedure of step 160 is illustrated according to one embodiment of the invention. As shown, the actual robot workstation 10 has deviated from the "ideal" robot arrangement. This procedure is performed for each robot 11, 12, 13, 14, 15, 16 at the actual robot workstation 10. In a first step 161, the workpiece 50 is moved past the component detector switch into the service area 52 for teach-in. Step 161 is performed such that the distance along the conveyor from each taught point for the nominal tracking frame to the location of the component detector switch will be known. Fig. 5 illustrates a schematic exemplary top view of the method for teaching nominal tracking when the usual location 58 is selected as the work frame. As shown, the workpiece 50 is moved from the fixed position 56 at the part detector switch to a fixed position 57 reachable by the first upstream robot 11, as shown in step 162. A tool of the first upstream robot 11 contacts an identifiable point 62 on the workpiece 50 in a step 163. In one non-limiting example, the identifiable point 62 is shown as a point on the workpiece 50 located along a longitudinal centerline w of the workpiece 50. However, the identifiable point 62 may be located anywhere on the workpiece 50 as desired.

[0025] With continued reference to Fig. 4 and Fig. 5, in step 164, a first position of the identifiable point 62 is recorded as the origin point in the robot controller 20. In the Fig. In the non-limiting example shown in Figure 4, the recording of the identifiable point 62 at the first position may occur when the identifiable point 62 is aligned with the conventional location defined as the workstation framework. The offset, or distance, of the workpiece 50 from the component detector switch is also recorded in step 164. The identifiable point 62 may be recorded at any position on the workstation 10 as needed. In a step 165, the workpiece 50 is then moved further downstream on the conveyor 54 with respect to the conveyor's direction of travel 60. In step 165, the identifiable point 62 is touched again at the second position. The second position is then recorded as the conveyor point in step 166.In a step 167, the tool of robot 11 is pivoted to a third position, which is in a direction perpendicular or normal to the direction of movement 60 of the conveyor 54. The workpiece 50 does not need to be moved along the conveyor during step 167. The third position is recorded as a normal point in step 166. In step 168, the resulting nominal tracking frame is calculated. This procedure can be repeated for each of the robots 11, 12, 13, 14, 15, and 16.

[0026] According to one embodiment of the invention, the nominal tracking frame can be expressed as follows: Tletze=Ferste*P where T letzte is the resulting nominal tracking frame calculated in step 168. T erste is the nominal tracking frame calculated according to existing teach-in programs, which is represented by a 4x4 transformation matrix. The x-direction of Terste can be represented by the vector (P c - P0), where P0 is the origin point and P c is the point of the conveyor device. The z-direction is determined by the cross product of the vector [(P c - P0) × (P N - P C )], where P Nis the normal point. Given the x-direction and z-direction, the y-direction can be automatically defined as orthogonal to the x-direction vector and the z-direction vector according to the right-hand rule. P is the offset recorded in step 164. The offset is represented by a 4x4 transformation matrix with a value only in the x-coordinate, such that P = [xyzwpr] = [(offset value) 0 0 0 0 0], where the offset value is the distance of the workpiece 50 from the part detector switch. By determining the offset from the part detector switch and using the offset in the calculation of the nominal tracking frame, a nominal tracking frame common to all robots 11, 12, 13, 14, 15, 16 at the real robot workstation 10 is guaranteed. This common nominal tracking frame becomes the workstation frame.

[0027] According to Fig. 2, in step 170, the frame calibration 35 is saved to the tracking data file. In certain multi-robot systems, it may be the case that not all robots in the multi-robot system will be able to contact the identifiable point 62 on the workpiece 50. In this plan, the work frame may be determined by a robot-to-robot calibration method, so that the work frame can be copied from a robot that has already established the work frame to other robots in the multi-robot system. Additionally, it will be understood that, as needed, other methods for teaching nominal tracking frames may be used, such as using vision to teach the nominal tracking frames to establish the work frame.

[0028] With continued reference to Fig. 2, the calibration trajectory 36 is taught on the workpiece 50 according to one embodiment of the invention in step 180. When the simulation workstation 34 comes close enough to the "ideal" robot arrangement, the calibration trajectory 36 can be taught, or the calibration trajectory 36 can be taught after the frame calibration 35 is determined. The calibration trajectory 36 is taught for each type of workpiece 50. The calibration trajectory 36 is taught to one of the robots 11, 12, 13, 14, 15, 16 through a teach-in program. The calibration trajectory 36 can be taught to one of the robots 11, 12, 13, 14, 15, 16 at the real robot workstation 10 by teaching at least three nonlinear points on the workpiece 50.The three nonlinear points may be points on the workpiece 50 that correspond to identifiable features on the workpiece 50 itself, which are visible visually on the workpiece and on CAD displayed on the robot simulation device 30. The calibration trajectory 36 only needs to be taught to one robot 11, 12, 13, 14, 15, 16. In one non-limiting example, the calibration trajectory 36 may be taught to the first upstream robot 11 with respect to the direction of travel 60 of the conveyor device 54. In step 190, the calibration trajectory 36 and the frame calibration tracking data file 35 may be reloaded to the robot simulation device 30.

[0029] In step 200, the robots 11, 12, 13, 14, 15, 16 are moved or realigned by the simulation workstation 34 of the robot simulation device 30 based on the frame calibration 35. After the robots 11, 12, 13, 14, 15, 16 are moved, the workpiece 50, as displayed on the simulation workstation 34 by CAD on the robot simulation device 30, is then moved in step 210 based on the calibration trajectory 36. Fig.6 illustrates an example of the CAD display of the simulation workstation 34 on the robot simulation device 30 after the calibration trajectory 36 has been loaded into the robot simulation device 30. The display shows the workpiece 50 corresponding to the ideal arrangement and a display of the workpiece 50 at the real robot workstation 10 corresponding to the calibration trajectory 36. A node map 64 is displayed, representing the calibration trajectory 36 taught to the workpiece 50' at the real robot workstation 10. The node map 64 thus displayed to a user by the robot simulation device 30 can physically align the workpiece 50' corresponding to the "ideal" arrangement with the workpiece 50' at the real robot workstation 10. For alignment, the workpiece 50' of the "ideal" arrangement is positioned with the node map 64 displayed on the robot simulation device 30.This step 210 is performed for each type of workpiece 50.

[0030] At step 220, the robot simulation device 30 calculates the part tracking offset 37. The part tracking offset 37 is a variable 4x4 transformation that corresponds to the change in position of the workpiece 50 of the ideal assembly from the position of the workpiece 50 at the actual robot workstation 10. The 4x4 transformation is expressed as a nominal tracking frame for each robot 11, 12, 13, 14, 15, 16. Because the nominal tracking frame for each robot is located at the same location or workstation frame, the part tracking offset 37 only needs to be calculated for one robot 11, 12, 13, 14, 15, 16. The resulting data from the calculation of the part tracking offset 37 can then be valid for all robots on the same side of the conveyor device.For example, the part tracking offset 37 can be calculated for the first upstream robot, which calculation will be valid for the robots 13, 15 on the same side of the conveyor device 54. This part tracking offset 37 can then be used for the robots 12, 14, 16 located on the other side of the conveyor device, for example, by simply changing the direction and rotation components of the nominal tracking frames of the robots 12, 14, 16 as needed.

[0031] Once the part tracking offset 37 is calculated, the part tracking offset 37 is stored in the tracking data file, as shown in step 230. The tracking data file with the part tracking offset 37 is then uploaded to the robot controller 20 in step 240 to be used by the robot controllers 17, 18, 19 through the data storage device 22. In the robot controller 20, the part tracking offset 37 is used for each type of workpiece 50 during production and teaching of the actual multi-robot system. The part tracking offset 37 can be used to shift production position data when the workpiece 50 is machined or manufactured.

Claims

[1] System for calibrating a multiple robot system, comprising: a robot simulation device (30) having a processor (31) configured therein to generate a simulation workstation (34) based on a predetermined arrangement of a real robot workstation (10), wherein the robot simulation device (30) communicates with a robot controller (20) that controls robots (11, 12, 13, 14, 15, 16) at the real robot workstation (10); and a software program (33) executed by the robot simulation device (30) and / or the robot controller (20) for calculating a part tracking offset between the simulation workstation (34) and the real robot workstation (10), wherein the robot controller (20) uses the part tracking offset to control the robots (11, 12, 13, 14, 15, 16); and the robot simulation device (30) calculates the part tracking offset in response to a tool of the real robot workstation (10) contacting an identifiable point on a workpiece (50) in a first and a second position of the workpiece (50) in the real robot workstation (10) and pivoting the tool to a third position in a direction perpendicular to a direction of movement of the workpiece (50) through the real robot workstation (10). [2] System according to claim 1, wherein the robot simulation device (30) operates computer-independently of the robot controller (20). [3] The system of claim 1, wherein the robot simulation device (30) comprises a display that provides a three-dimensional model of the multiple robot system and a workpiece (50) at the actual robot workstation (10). [4] The system of claim 1, wherein the predetermined arrangement is based on a manufacturing drawing of the multiple robot system. [5] The system of claim 1, wherein the software program (33) creates tracking frames in the simulation workstation (34) by the robot simulation device (30). [6] The system of claim 1, wherein the part tracking offset is calculated based on a frame calibration performed by the robot controller (20) and / or a calibration trajectory (36) performed by the robot controller (20). [7] The system of claim 6, wherein the frame calibration is the calculation of a workstation frame, and the calibration trajectory (36) is the calculation of a taught trajectory on a workpiece (50). [8] The system of claim 1, wherein the part tracking offset takes into account a workpiece (50) moving on a conveyor device at the actual robot workstation (10). [9] Method for calibrating a multiple robot system with the steps: Creating a simulation workstation (34) of an operation of a real robot workstation (10) by a robot simulation device (30), wherein the simulation workstation (34) is based on a predetermined arrangement of the real robot workstation (10); Producing tracking frames at the simulation workstation (34) by the robot simulation device (30); Determining by a robot controller (20) for robots (11, 12, 13, 14, 15, 16) at the real robot workstation (10) whether there is a deviation between the simulation workstation (34) and the real robot workstation (10); Carrying out a frame calibration by the robot controller (20) to calibrate the simulation workstation (34) with the real robot workstation (10) for controlling the robots (11, 12, 13, 14, 15, 16); and Teaching a nominal tracking frame for each of the plurality of robots of the multiple robot system, comprising touching, by a tool of at least one robot of the plurality of robots, an identifiable point on a workpiece (50) at a first and second position of the workpiece (50) in the actual robot workstation (10). [10] Method according to claim 9, wherein the robot simulation device is computer-independent of the robot controller (20). [11] A method according to claim 9, wherein the predetermined arrangement is based on a manufacturing drawing of the multiple robot system. [12] A method according to claim 9, wherein the frame calibration is carried out when the deviation exists between the simulation workstation (34) and the real robot workstation (10), and comprising the steps of: Producing a workstation frame at the actual robot workstation (10); and Teaching the nominal tracking frame for each of the plurality of robots of the multiple robot system by the robot controller (20) so that the nominal tracking frame for each of the plurality of robots is located in the workstation frame. [13] The method of claim 12, wherein teaching the nominal tracking frame comprises pivoting the tool, perpendicular to a direction of movement of the workpiece (50) through the actual robot workstation (10), to a third position. [14] The method of claim 12, wherein an offset is recorded by the robot controller (20) during teaching of the nominal tracking frame for each robot (11, 12, 13, 14, 15, 16) of the plurality of robots. [15] Method according to claim 9, wherein the calibration trajectory (36) comprises teaching at least three non-linear points on the workpiece (50). [16] A method according to claim 9, comprising the steps of: Moving the simulation workstation (34) by the robot simulation device (30) so that it substantially corresponds to the real robot workstation (10); and Calculating a part tracking offset by the robot simulation device (30) based on the displacement of the simulation workstation (34). [17] The method of claim 16, wherein a node map is displayed on the robot simulation device (30) to assist a user in moving the simulation workstation (34). [18] Method for calibrating a multiple robot system with the steps: Creating a simulation workstation (34) of an operation of a real robot workstation (10) by a robot simulation device (30), wherein the simulation workstation (34) is based on a predetermined arrangement of the real robot workstation (10); Producing tracking frames at the simulation workstation (34) by the robot simulation device (30); Defining a workstation frame on the simulation workstation (34) as being located at a specific position of the workpiece (50) while the workpiece (50) is moving on a conveyor device, the specific position being determined when the workpiece (50) is initially detected before entering a work zone, the specific position being communicated to a controller to initiate control of the robots (11, 12, 13, 14, 15, 16), Determining by a robot controller (20) for robots (11, 12, 13, 14, 15, 16) at the real robot workstation (10) whether there is a deviation between the simulation workstation (34) and the real robot workstation (10); Executing a frame calibration and / or a calibration trajectory (36) by the robot controller (20) to calibrate the simulation workstation (34) with the real robot workstation (10); Moving the simulation workstation (34) by the robot simulation device (30) so that it substantially corresponds to the real robot workstation (10); and Calculating a part tracking offset by the robot simulation device (30) based on the displacement of the simulation workstation (34) and using the part tracking offset to control the robots. [19] Method according to claim 18, wherein the frame calibration is carried out when the deviation exists between the simulation workstation (34) and the real robot workstation (10), and which comprises the step: Teaching a nominal tracking frame for each of a plurality of robots of the multiple robot system by the real robot controller (20) such that the nominal tracking frame for each of the plurality of robots is located in the workstation frame.

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