Folding robot with central folding force detection and method for operating and modernizing a folding robot

Description

[0001] The invention relates to a folding robot for performing a folding operation with a robot folding head comprising a connection element, a connecting element, a head element, and at least one folding roller, wherein the connecting element is arranged between the connection element and the head element, and the at least one folding roller is arranged on the head element. The invention further relates to a method for operating such a folding robot and a method for modernizing a folding robot comprising a connection element, a first connecting element, a head element, and at least one folding roller, wherein the first connecting element is arranged between the connection element and the head element, and the at least one folding roller is arranged on the head element.

[0002] Such folding robots are known in the prior art and are used, for example, in the automotive industry to join exterior body parts with interior body parts. Typical components for this type of assembly are hoods, car doors, and fenders. Particularly for quality assurance reasons, an idealized folding force should be applied to the folding flange during the folding process. KR 2086813 B1 discloses a method for monitoring the folding process. Furthermore, DE 10 2010 051 025 A1 discloses a folding robot with a force measuring element, wherein the force measuring element detects a contact force of a folding roller and is arranged between a joint area of ​​a robot arm and the folding roller.Furthermore, DE 10 2004 032 392 A1 discloses a folding device in which a folding force of a folding roller is detected by means of a sensor on the axis of the folding roller. The actual force applied by the folding roller for each increment of the folding path is detected and compared with a target force. In case of a deviation, the applied folding force in the next increment is adjusted to the target force. DE 20 2011 000 315 U1 further describes a robot with a folding tool, in which loads occurring during folding are detected by a sensor and displayed on a screen on the folding tool. A sensor is provided in a connecting element between the attachment element and the head element, and this sensor can be a combination of a displacement sensor and a force sensor. A force sensor can be arranged in the area of ​​the roller carrier in the form of a pressure transducer, a strain gauge strip, or the like.US patent 2018 / 0050377 A1 also describes a roll folding device with sensors for detecting a force exerted during folding, whereby a currently exerted force can be compared with a target force.

[0003] A disadvantage is that in the described configurations, each sensor is assigned to exactly one folding roller. For folding robots with multiple folding rollers designed for different folding operations, a corresponding number of sensors must therefore be provided, especially when folding rollers are replaced. This is because new sensors must be integrated every time a folding roller or the entire head element is changed. This increases the wiring and calibration effort. Furthermore, existing folding robots without such force measurement are difficult to retrofit. Since the adjustment of the actual force to a target force occurs almost in real time, a powerful and therefore expensive processing unit is necessary, or the folding process can only be performed comparatively slowly.

[0004] Furthermore, WO 2013 / 149 894 A1 describes a robot-guided forming tool and a forming process for folding workpieces. Using an adjustable actuator, the folding force exerted by the forming tool during folding is set without changing the path programming in the robot controller. A sensor for the contact force with which the folding roller is pressed against a workpiece provides the values ​​for the actuator's control unit, thus increasing or decreasing the contact force applied by the forming tool.

[0005] Against this background, an object of the present invention is to provide an improved folding robot and an improved method for operating a folding robot. Furthermore, it aims to provide the possibility of retrofitting existing folding robots with a folding force measurement system in a relatively simple manner. In particular, the force measurement should function independently of the roller configuration, especially independent of the type of folding roller and independent of the position of the folding roller, and should advantageously be modularly retrofittable.

[0006] To solve this problem, a folding robot, a method for modernizing a folding robot, and a method for operating a folding robot according to the independent claims are proposed. Further advantageous embodiments of the invention are described in the dependent claims and the description and are illustrated in the figures.

[0007] The proposed solution provides a folding robot designed to perform a folding operation, comprising a robot folding head. The robot folding head includes a connection element, a connecting element, a head element, and at least one folding roller. The connecting element is arranged between the connection element and the head element. The at least one folding roller is arranged on the head element, and at least part of the connecting element is designed as a measuring body. The measuring body is equipped with at least one sensor element for detecting the folding force exerted on a folding flange during a folding operation by means of one of the at least one folding roller.Advantageously, the connecting element, as the central element of the folding robot, in particular an intermediate section of the connecting element or the complete connecting element, becomes the measuring body, which can measure the folding force by means of at least one sensor element, in particular by means of applied strain gauges, thus making the force measurement advantageously independent of the roller configuration. Since, advantageously, a complete section of the connection between the connecting element and the head element is designed as the measuring body, the measuring body with the sensor elements assigned to it is advantageously designed for the precise detection of a folding force exerted by a folding roller on a folding flange, and is also advantageously designed to detect the direction of action of a force.The measuring body and the at least one sensor element advantageously form a sensor unit for detecting a folding force during a folding process. Advantageously, due to the design of the measuring body as an intermediate element between the connecting element and the head element, force vectors for the respective detected folding force can be assigned to a discrete number of predefined measuring points. Thus, advantageously, not only a pure magnitude value for the folding force is determined, but also, and especially, the direction of action of the folding force. In particular, it is provided that the folding robot comprises several folding rollers, which are preferably arranged in a star-shaped pattern on the head element.Advantageously, the folding robot comprises a plurality of differently designed folding rollers arranged on the head element, wherein the folding robot is advantageously designed to perform different folding operations by means of the differently designed folding rollers.

[0008] The folding force is primarily influenced by the robot's predetermined movement path, hereinafter also referred to as the folding path. Advantageously, the folding robot does not include an additional actuator acting on a folding roller, which could further vary the folding force. This makes the folding robot more affordable, robust, and therefore less prone to malfunctions.

[0009] The folding force exerted by each folding roller on a folding flange is advantageously detected by means of the measuring body and the at least one sensor element arranged thereon. In particular, an embodiment is provided in which the measuring body comprises exactly one sensor element. Several sensor elements can be provided, particularly to improve the measurement result. However, several sensor elements are not necessary to assign a sensor element to each folding roller. In particular, a sensor unit formed from the measuring body and the at least one sensor element, especially a single sensor element, is provided for a plurality of folding rollers and is advantageously configured to detect the respective folding force for each folding operation.

[0010] According to a particularly advantageous embodiment, the measuring body is designed to be elastically deformable, in particular elastically deformable in all three spatial directions, i.e., in particular in an X-direction, a Y-direction, and a Z-direction. The at least one sensor element, in particular a plurality of sensor elements, is advantageously designed to detect elastic deformation of the measuring body. Due to the deformability in all three spatial directions, a force vector can advantageously be determined for an acting folding force, and thus, in addition to the magnitude of an acting force, also its direction of action can be advantageously determined. Strain gauges are particularly suitable as sensor elements for force measurement, especially strain gauges with a measuring amplifier.In particular, the sensor element is intended to be a sensor element utilizing the piezoelectric effect, a sensor element utilizing the (piezo-)resistive effect, a sensor unit utilizing the thermoresistive effect, a sensor element utilizing the magnetoresistive effect, a sensor element utilizing the magnetostrictive effect, a sensor element utilizing the Hall effect, a sensor element utilizing the inductive effect, and / or a sensor element utilizing the capacitive effect. The sensor element can therefore be implemented not only with strain gauges but also based on other known physical principles, in particular also as a vibrating string sensor.

[0011] Another advantageous embodiment of the folding robot features a column-shaped connecting element, particularly the measuring body. The interchangeability of the column element and the virtually space-constrained implementation of force measurement using the measuring body and at least one sensor element advantageously allow for the retrofitting of older systems. Furthermore, a column-shaped design enables particularly effective detection of deformations acting on the measuring body during a folding process.

[0012] Furthermore, the measuring body is geometrically optimized for measurement. In particular, the measuring body is formed from interconnected struts, which together form a framework structure. With this design, elastic deformations at the nodes of the struts can be detected with greater accuracy. Consequently, a folding force can be measured with significantly improved precision.

[0013] According to a further advantageous embodiment, the connecting element has a first connecting section and a second connecting section, wherein the connecting element is advantageously connected to the attachment element via the first connecting section and to the head element via the second connecting section. The connecting sections thus advantageously represent the connection interfaces to the attachment element, which can be designed in particular as a docking plate, and the head element. The measuring body is advantageously the part of the connecting element between the first connecting section and the second connecting section.

[0014] A further advantageous embodiment provides that a processing unit is assigned to the folding robot. Advantageously, the processing unit is configured to acquire and process sensor signals provided by the at least one sensor element, in particular for determining a folding force profile. Furthermore advantageously, the folding process is controlled by the processing unit, in particular the applied folding force. Advantageously, at least one actuator unit is controlled by the processing unit to execute a folding operation. The processing unit also advantageously includes a measuring amplifier for the sensor signals provided by the at least one sensor element. In particular, it is provided that the folding robot includes the processing unit, which can be arranged, in particular, on the connection element.According to one embodiment, the computing unit associated with the folding robot is located remotely from the folding robot and is connected to it via a communication link for data transmission. This communication link can be wired or wireless, in particular a radio link, and more specifically, a connection using infrared, Bluetooth®, or WLAN (Wireless Local Area Network). In particular, one embodiment provides that the folding robot is connected to the computing unit via the internet.

[0015] A further advantage is that the processing unit can store a force profile for a folding force for each folding operation. In particular, an initial force profile is stored, specifically by saving the parameters for a first initial folding operation. The processing unit is specifically designed to evaluate the initial force profile to ensure compliance with predefined limit values ​​for the folding force. Advantageously, the folding robot, and especially its processing unit, is further designed to adjust the control parameters for the folding operation based on the results of this evaluation, so that the limit values ​​are met or at least exceedances of limit values ​​occur less frequently.

[0016] Advantageously, the processing unit stores a target force profile for a folding force for a given folding process. This target force profile can, in particular, be a copy of a previously executed actual force profile, especially one that meets specified target values. The processing unit is advantageously further designed to determine an actual folding force profile for a folding process from the acquired sensor signals and, in particular, to adjust the folding force applied by one of the at least one folding roller for a subsequent folding process, specifically by modifying the control of the folding robot and, furthermore, by adjusting the folding path executed by the robot, so that the folding force profile during the folding process corresponds as closely as possible to the target force profile. This advantageously ensures a high quality of the folding process.Furthermore, this time-delayed force control prevents overloading, particularly sustained overloading, of the mechanical components, and advantageously allows for the maintenance of an idealized force profile. In addition, a real-time response of the system during normal operation is advantageously unnecessary. The processing unit is further advantageously configured to store the control parameters as target control parameters for a current actual force profile that corresponds to a target force profile within predefined tolerances, particularly as long as the actual force profile resulting from these target control parameters does not deviate impermissibly from the target force profile. Advantageously, new control parameters that again lead to an acceptable actual force profile are then stored as new target control parameters. The processing unit is advantageously designed to monitor this process and execute it accordingly.Advantageously, by bringing the actual force profile closer to the target force profile, the folding path of the robot is optimized.

[0017] A further advantageous embodiment provides that the processing unit is further designed to detect an overload occurring during a folding process with respect to the folding robot, in particular an overload with respect to at least one component of the folding robot, and furthermore, in particular an overload with respect to the folding roller of the folding robot that performs the folding process, by evaluating the sensor signals. In particular, the processing unit is further designed to adjust a folding force applied by means of one of the at least one folding roller for a subsequent folding process in such a way as to prevent a permanent overload with respect to the folding robot. Advantageously, this reduces wear on components of the folding robot and thus increases the service life of the folding robot.

[0018] According to a further advantageous embodiment, the folding robot includes a communication interface, which is advantageously configured to transmit sensor signals acquired by the at least one sensor element to a remote computing unit via a communication network. The remote computing unit can be the computing unit assigned to the folding robot. However, the remote computing unit can also be, in particular, another computing unit with which remote maintenance functions can be performed, especially with regard to the folding robot, and furthermore, especially with regard to a folding operation carried out by the folding robot. The remote computing unit can, in particular, be implemented as a cloud application.In particular, the remote computing unit is set up for maintenance and configuration tasks relating to the folding robot, whereby in particular a folding process can be adapted by means of the remote computing unit, especially with regard to an improved folding result and / or overload protection of components of the folding robot by preventing a regular repeated occurrence of excessively high forces during the execution of a folding process.

[0019] Furthermore, it is advantageous for the folding robot to be operated according to a method for operating a folding robot designed according to the invention.

[0020] The further proposed method for modernizing a folding robot with a robot folding head, comprising a connection element, a first connecting element, a head element, and at least one folding roller, wherein the first connecting element is arranged between the connection element and the head element, and the at least one folding roller is arranged on the head element, provides that the first connecting element is removed and replaced by a second connecting element, wherein at least part of the second connecting element is designed as a measuring body, the measuring body being equipped with at least one sensor element arranged on the measuring body for detecting the force exerted on a folding flange during a folding process by means of one of the at least one folding roller. In particular, it is provided that the modernization transforms an "old" folding robot into a folding robot designed according to the invention.Therefore, a large proportion of "old" folding robots can advantageously continue to be used with an expanded range of functions. Since even if the "old" folding robot comprises several folding rollers, only the first connecting element (i.e., the "old" connecting element) needs to be replaced with the second connecting element (i.e., the "new" connecting element), the modernization is advantageously relatively simple. In particular, the method for modernizing a folding robot also provides a processing unit configured to acquire and process sensor signals provided by the at least one sensor element, especially as described in connection with the embodiments of a folding robot designed according to the invention. Specifically, it is provided that the processing unit is arranged on the connecting element, in particular by screwing it on.According to one design variant, the computing unit is integrated into the connecting element or the linking element. Advantageously, the computing unit is connected to a control unit for controlling the folding robot for data transmission, and the control unit is adapted accordingly to be able to adjust a folding process based on data from the computing unit, in particular to approximate a target force profile and / or to prevent permanent overloading of components of the folding robot during the execution of folding operations.

[0021] The method proposed for operating a folding robot with a robot folding head, also intended to solve the aforementioned problem, wherein the robot folding head comprises a connection element, a connecting element, a head element, and at least one folding roller, the connecting element being arranged between the connection element and the head element, and the at least one folding roller being arranged on the head element, provides that an elastic deformation of the connecting element is detected during a folding process, the elastic deformation being able to occur in all three spatial directions, and a folding force exerted on a folding flange during the folding process by means of a folding roller of the folding robot is determined from the detected elastic deformation, in particular a force vector representing the folding force. Advantageously, it is not necessary to assign a separate sensor system to each folding roller of the folding robot.Furthermore, the determined folding force allows for improved control of the folding process, thus contributing significantly to quality assurance. Advantageously, a force vector is determined for a folding force applied to a folding flange, so that not only the magnitude of the folding force but also its direction of action is advantageously determined.

[0022] According to an advantageous embodiment of the method, a folding roller of the folding robot is moved along a component according to predefined path points during a folding operation. The folding force determined during the folding operation is advantageously assigned to the respective path points to determine a folding force profile. Advantageously, the values ​​determined for the folding force are stored, particularly as pairs of values ​​corresponding to the respective path points. Specifically, a force vector is assigned to each path point as the folding force. Advantageously, errors and / or overloads can be detected early by evaluating the folding force profile thus determined.

[0023] An advantageous further development of the method involves comparing the determined actual folding force profile with a target folding force profile specified for the folding process. Furthermore, deviations between the determined actual folding force profile and the target folding force profile are advantageously determined for the respective path points. This allows for the advantageous detection of non-compliance with the folding process specifications. Based on the identified deviations, the folding process can then be optimized to minimize these deviations, thereby preventing overloads, particularly persistent overloads. For this optimization of the folding process, the robot's folding path is advantageously adjusted, and specifically controlled, using the recorded actual folding force profile.

[0024] It is particularly advantageous that, for a subsequent folding operation, the folding force exerted by the folding roller on the folding flange is adjusted, in particular by an adapted control of the folding robot, such that the deviations determined with respect to the previously performed folding operation are reduced. An adapted control of the folding robot also includes, in particular, a change in parameters of the robot control, especially a change in parameters that result in a change in the folding path, such as, in particular, an adjustment of the offset. Advantageously, by adjusting the folding force exerted on the folding flange, a time-delayed force control is achieved, which is advantageously implemented by a correspondingly adapted control of the robot.In particular, a folding path specified for controlling the folding robot is optimized to adapt the actual force profile to a target force profile, especially through a corresponding control system that influences the folding path and exchanges control data with the robot's processing unit. Furthermore, according to one embodiment, influencing the folding path involves changing at least one parameter, especially the offset, and copying this change to the robot's control system. Thus, in this embodiment, there is no direct exchange of data between the robot and the force measurement taken by the measuring device. By adapting the force profile, specifically by bringing the actual force profile closer to the target force profile, permanent overloads of the folding robot's mechanical components can be prevented.Furthermore, high and consistent quality of folded joints can be achieved. Another advantage is that a folding force profile adapted to a predefined, idealized target folding force profile can be realized without having to provide a real-time control system.

[0025] Advantageously, the proposed method implements force control by first storing the folding force measured during a folding operation along with its corresponding path points. After the folding operation, the resulting force profile is advantageously compared with an idealized force curve specified for this folding operation, according to a user requirement. In the subsequent step, the next folding operation, and thus the folding force exerted by the folding roller, is advantageously adjusted based on the determined deviations from the idealized force curve, such that the deviations are minimized in the next step. The adjustment of the folding operation therefore advantageously only takes place in the subsequent cycle. The adjustment of the folding force exerted by the folding roller during folding is achieved, in particular, by adjusting the control parameters used to control the actuators of the folding robot during folding.

[0026] According to a further advantageous embodiment of the method, it is provided that, for a completed folding operation, the occurrence of an overload with respect to the folding robot is checked based on the determined folding force, in particular by the processing unit assigned to the folding robot. If an overload is detected, a subsequent folding operation is advantageously adapted to avoid the overload, in particular by adjusting the control parameters with which the actuators of the folding robot are controlled during folding. Advantageously, this reduces the wear of the folding robot and increases the service life of the robot.

[0027] Further advantageous details, features and embodiments of the invention are explained in more detail in connection with the exemplary embodiments shown in the figures (Fig.: Figure). These show: Fig. 1 shows a schematic representation of an embodiment of a folding robot designed according to the invention; Fig. 2 shows a perspective view of an embodiment of a robot folding head of a folding robot designed according to the invention; Fig. 3 shows a perspective view of a section of a further embodiment of a robot folding head of a folding robot designed according to the invention; Figs. 4a to 4c each show a diagrammatic representation of an embodiment of a folding force 5 detected according to the invention over a path s; Fig. 5 shows a block diagram of an embodiment of a method designed according to the invention for operating a folding robot; and Fig. 6 shows a perspective view of an embodiment of a connecting element of a robot folding head of a folding robot designed according to the invention.

[0028] In the various figures, identical parts are usually marked with the same reference symbols and are therefore sometimes only explained in connection with one of the figures.

[0029] Fig. 1 Figure 4 shows a schematic representation of a folding robot 4 designed to perform a folding operation. The robot 4 comprises an articulated robot arm 41, at the end of which a robot folding head 1 is arranged. An advantageous embodiment of the robot folding head 1 is shown in Fig. 2 The robot folding head 1 comprises a connecting element 16, a connecting element 11, a head element 13, and a first folding roller 151, a second folding roller 152, and a third folding roller 153, each arranged on the head element 13. The connecting element 11 is arranged between the connecting element 16 and the head element 13. The connecting element 11 is designed as a measuring body, wherein the measuring body is equipped with at least one sensor element arranged on the measuring body (in Fig. 1 (not explicitly shown) is designed to detect the folding force exerted on a folding flange during a folding process using one of the folding rollers 151, 152, 153. The measuring body, together with the at least one sensor element, forms a sensor unit for detecting the folding force. A component arrangement 2, positioned on a folding bed 3, can be folded according to a predefined folding process using the folding rollers 151, 152, 153. The component arrangement 2 comprises a first component 21 and a second component 22. By folding over a component edge 23 of the first component 21 using one of the folding rollers 151, 152, 153, the first component 21 and the second component 22 are joined together. Further details of an advantageous embodiment of the robot folding head 1 are described with reference to Fig. 2 explained.

[0030] As in Fig. 2 As illustrated by way of example, the robot folding head 1 comprises a connecting element 16, a connecting element 11, a head element 13, and several folding rollers 151, 152, 153, wherein the connecting element 11 is arranged between the connecting element 16 and the head element 13, and the folding rollers 151, 152, 153 are arranged on the head element 13. The folding rollers 151, 152, 153 are of different designs and are arranged in a star shape on the head element 13, wherein the folding robot 4 is configured to perform different folding operations by means of the differently designed folding rollers 151, 152, 153, in particular folding operations adapted to different component arrangements 2 and different component geometries.A portion of the connecting element 11 of the robot folding head 1, which forms a complete intermediate section of the connecting element 11, is designed as a measuring body 111, wherein several sensor elements 17, in particular several strain gauges with preferably different orientations, are arranged on the measuring body 111. The measuring body 111, together with the sensor elements 17, forms a sensor unit designed to detect folding forces exerted on a folding flange during a folding process by means of one of the folding rollers 151, 152, 153. As in . Fig. 2 As shown, in this embodiment the measuring body 111 is designed in a columnar shape. Furthermore, the measuring body 111 is elastically deformable, with the sensor elements (17) attached to the measuring body 111 being designed to detect elastic deformation of the measuring body 111. In this embodiment, the measuring body 111 has a truss-like structure with recesses 1112 and struts 1111 and exhibits a defined elastic deformation behavior, so that any deformations that occur can advantageously be clearly assigned to specific folding forces.

[0031] In this embodiment, the connecting element 16 of the robot folding head 1 is designed as a docking plate, with which the robot folding head 1 is attached to the robot arm 41, as in the embodiment shown in Fig. 1 As shown, it can be arranged. A processing unit 12 is arranged on the connecting element 16, which is configured to acquire and process sensor signals provided by the sensor elements 17. In this embodiment, the processing unit 12 comprises a microprocessor unit and a measuring amplifier (microprocessor unit and measuring amplifier in Fig. 2 (not explicitly shown) for processing the (strain) signals recorded on the measuring body 111. The processing unit 12 also contains a target force profile for a folding force for predefined folding operations, stored in a corresponding memory unit of the microprocessor unit. Furthermore, a lower tolerance limit TH1 and an upper tolerance limit TH2 with respect to the target force profile are stored. Additionally, an overload threshold TH3 is stored, the sustained exceedance of which would lead to an overload of the folding robot 4. The processing unit 12 is designed to determine an actual force profile of the folding force during a folding operation from the acquired sensor signals.The system provides that during a folding operation, where one of the folding rollers 151, 152, 153 of the robot folding head 1 is moved along a component arrangement 2 according to predefined path points, the folding force is determined for each path point, and the path points with the recorded values ​​for the folding force are stored as value pairs. The actual force profile is then derived from these stored value pairs.

[0032] The processing unit 12 is further configured to compare the recorded actual force profile with the target force profile stored in the processing unit 12 and to detect deviations, in particular deviations where the lower tolerance limit TH1 is undershot or the upper tolerance limit TH2 is exceeded. Taking these detected deviations into account, a subsequent folding process is adjusted using the processing unit 12 such that the subsequently recorded actual force profile is more closely aligned with the target force profile, in particular so that the lower tolerance limit TH1 is not undershot and the upper tolerance limit TH2 is not exceeded. Specifically, the processing unit 12 is designed to control the corresponding actuators of the folding robot 4.In particular, it can also be provided that a control unit is assigned to the robot 4, with which the actuators of the robot 4 and thus the folding process are controlled, whereby the results of the computing unit 12 are then forwarded to this control unit, in particular the detected deviations, so that the control unit can control the robot 4 according to the result of the evaluation of the computing unit 12.

[0033] Fig. 3 Figure 1 shows a further embodiment, in which only a part of the robot folding head 1 is depicted. It is provided that the folding force profile determined by the processing unit 12 from the detected strain or elastic deformation 6 of the central measuring body 111 is also transmitted to a display device 7 in order to represent an actual force profile for the force 5 acting on a folding roller 153 during a folding operation. The force 5 acting during a folding operation is thus in Fig. 3 represented as a vector. This clarifies that the measuring body 111, which in this embodiment forms a complete intermediate piece between the connecting element 16 and the head element 13, is equipped with the associated sensor elements 17 to determine both the magnitude of the acting force 5 and its direction. An actual force profile 9 can thus be advantageously adapted to a predetermined target force profile. In particular, this improves the quality of the folding result. Examples of a recorded actual force profile 9 are shown in Fig. 4a, Fig. 4b und Fig. 4c depicted.

[0034] The in Fig. 4a bis Fig. 4c The actual force curves shown (9) follow chronologically from Fig. 4a after Fig. 4c on top of each other. The diagram shows the actual force curve 9 for each folding operation as force 5 over the path S for the same folding roller. Furthermore, in Fig. 4a bis Fig. 4c The target force curve 8 stored in the calculation unit 12, a lower tolerance limit TH1 for the target force curve 8, an upper tolerance limit TH2 for the target force curve 8 and, by the beginning of the hatching, an overload threshold TH3 are shown.

[0035] The processing unit 12 is designed to detect when the actual force curve 9 should exceed the overload threshold TH3 (in Fig. 4a bis Fig. 4c (not shown). In the event of such a detected exceedance of the overload threshold TH3, it is specifically provided that, in order to prevent damage to components of the folding robot 4, the actuators of the folding robot 4 are directly controlled in such a way that the force is reduced. In particular, a warning message can also be issued, especially by means of a display device 7.

[0036] Furthermore, the computing unit 12 is designed to influence the control parameters for the folding robot so that the actual force profile 9 is approximated as closely as possible to the target force profile 8. The computing unit 12 monitors whether, during a folding operation, the lower tolerance limit TH1 is undershot, the upper tolerance limit TH2 is exceeded, or the overload threshold TH3 is exceeded, and adjusts the control parameters and thus the actual force profile 9 accordingly for the subsequent folding operation. A sustained exceedance of the overload threshold TH3 can lead to mechanical overload of the folding robot components 4 and increased energy consumption, while a sustained undershooting of the lower tolerance limit TH1 or a sustained exceedance of the upper tolerance limit TH2 can result in defective manufacturing of the folding flange. An example is shown in Fig. 4a A violation of the lower tolerance limit TH1 between waypoint S1 and waypoint S2 is shown. Furthermore, in Fig. 4a At the beginning of the folding process, several exceedances of the upper tolerance limit TH2 are displayed. Through appropriate control, the following steps are prevented. Fig. 4b und Fig. 4c The actual force curves 9 shown in the folding processes were adjusted such that in Fig. 4b The actual force curve 9 exceeds the upper tolerance limit TH2 only twice and the lower tolerance limit TH1 is not undercut. Through further adjustments in the following and in Fig. 4c In the depicted folding process, the actual force curve 9 is so closely approximated to the target force curve 8 that the actual force curve 9 lies within the tolerance limits TH1, TH2.

[0037] Fig. 5 demonstrates, using a flowchart as an example, how a folding robot, in particular a folding robot 4, as described in reference to Fig. 1 and Fig. 2 The folding robot is described and operated according to a proposed method. The folding robot comprises a robot folding head, which includes a connection element, a head element, a connecting element arranged between the connection element and the head element, and a folding roller arranged on the head element. The folding robot is assigned a computing unit and a control unit, which may form a single unit. Together with the computing unit and the control unit, the folding robot forms a robot system. In a first step A, an initial folding path is defined for a folding operation, which the folding robot is to follow with the folding roller to join a component assembly. The folding path defines the distance traveled by the folding roller of the folding robot along the fold flange to be produced, as well as the applied folding force.In this embodiment, the initial folding path yields a first actual folding force profile. In step C, the folding process then begins with the folding robot. During the folding process, in process step D, an elastic deformation of the connecting element of the robot's folding head is detected. From the detected elastic deformation, the folding force exerted on the folding flange by the folding roller of the folding robot during the folding process is determined and recorded. For this purpose, it is specifically provided that the folding roller is moved along the component assembly according to predefined path points that define the folding path, whereby the determined folding force is assigned to the respective path points to determine an actual folding force profile. In step E, a folding process ends. In step F, the recorded folding force is evaluated.In this process, the determined actual folding force profile is compared with the target folding force profile specified for this folding operation. Deviations between the determined actual folding force profile and the target folding force profile for the respective path points are identified during the evaluation. Threshold value comparisons are used to check whether the deviations are within defined permissible tolerances. Taking these deviations into account, the control parameters, and thus the defined folding path, are adjusted in step G to reduce the identified deviations for subsequent folding operations and, in particular, to prevent permanent overloads on components of the folding robot. In step G, the robot path corrections are defined. In step H, the adjusted folding path is then defined as the new specification for the folding path.This new folding path thus replaces the initial folding path defined in step A. In the subsequent process step C, a new folding operation is performed according to the newly defined folding path. The further steps D to H follow accordingly. It can, of course, be provided that the detected deviations are so small or lie within a defined tolerance range that no adjustment of the folding path is necessary, but only when the deviations fall outside the tolerance range. In an additional optional process step, the occurrence of an overload with respect to the folding robot is checked for a completed folding operation based on the determined folding force. If an overload is detected, where there is also a deviation outside the tolerance range, the folding path is adjusted to prevent the overload, and preferably a warning message is issued.

[0038] Fig. 6Figure 1 shows an embodiment of a connecting element 11 of a robot folding head 1 of a folding robot 4, wherein part of the connecting element 11 is designed as a measuring body 111 in a frame structure with struts 1111. A first connecting section 112 and a second connecting section 113 are attached to the measuring body 111, and the connecting element 11 can be connected to a mounting element 16 of a robot folding head 1 via the first connecting element 112 and to a head element 13 of a robot folding head 1 via the second connecting element 113. If a conventional connecting element is replaced with this connecting element 11 in a folding robot, the folding robot is advantageously modernized to enable corresponding folding force measurement. A corresponding processing unit is also installed and connected as part of the modernization.In particular, a signal processing unit with a communication interface can also be provided, wherein the sensor signals detected by the at least one sensor element 17 arranged on the measuring body 111 can then be sent to a remote computing unit, for example via a mobile communication module, wherein the sensor signals can be evaluated for example for a remote maintenance function.

[0039] The embodiments shown in the figures and explained in connection with them serve to illustrate the invention and are not limiting to it. Reference symbol list

[0040] 1 Robot folding head 11 Connecting element 111 Measuring body 1111 Strut of the measuring body (111) 1112 Recess of the measuring body (111) 112 First connecting section 113 Second connecting section 12 Computing unit 13 Head element 151 Folding roller 152 Folding roller 153 Folding roller 16 Connecting element 17 Sensor element 2 Component arrangement 21 First component 22 Second component 23 Component edge 3 Folding bed 4 Folding robot 41 Robot arm 5 Folding force 6 Elastic deformation 7 Playback device, in particular image playback device 8 Target force curve 9 Actual force curve TH1 Lower tolerance limit TH2 Upper tolerance limit TH3 Overload threshold S1 First waypoint in a folding operation S2 Second waypoint in a folding operation A Initial folding path C Start of the folding process D Recording of the folding force E Completion of the folding process F Evaluation of the folding force G Adjustment of the folding path, in particular by defining robot path corrections H Setting the adjusted folding path as the new specified folding path

Claims

1. A hemming robot (4) which is configured to carry out a hemming operation, with a robot hemming head (1) comprising an attaching element (16), a connecting element (11), a head element (13) and a plurality of hemming rollers (151, 152, 153), wherein the connecting element (11) is arranged between the attaching element (16) and the head element (13), and the at least one hemming roller (151, 152, 153) is arranged on the head element (13), characterized in that an intermediate piece of the connecting element (11) or the complete connecting element (11) is configured as a measuring element (111) from struts (1111) which are connected to one another and form a framework structure, wherein the measuring element (111) forms, with at least one sensor element (17) arranged on the measuring element (111), a sensor unit which is configured for the detection of a hemming force (5) exerted on a hem flange by means of one of the plurality of hemming rollers (151, 152, 153) during a hemming operation, wherein the measuring element (111) is of elastically deformable configuration in all three spatial directions, wherein a force vector can be determined for an active hemming force (5) by a deformation capability in all three spatial directions, and wherein the at least one sensor element (17) is configured for the detection of the elastic deformation of the measuring element (111).

2. The hemming robot (4) as claimed in claim 1, characterized in that the measuring element (111) is of column-shaped configuration.

3. The hemming robot (4) as claimed in claim 1 or claim 2, characterized in that the connecting element (11) has a first connecting portion (112) and a second connecting portion (113), wherein the connecting element (11) is connected via the first connecting portion (112) to the attaching element (16) and is connected via the second connecting portion (113) to the head element (13).

4. The hemming robot (4) as claimed in one of the preceding claims, characterized in that the hemming robot (4) is assigned a computing unit (12), wherein the computing unit (12) is configured to detect and to process sensor signals provided by the at least one sensor element (17).

5. The hemming robot (4) as claimed in claim 4, characterized in that a setpoint force profile (8) of a hemming force (5) for a predefined hemming operation is stored in the computing unit (12), the computing unit (12) is configured, furthermore, to detect an actual force profile (9) of the hemming force (5) for a hemming operation from the detected sensor signals, and to adapt a hemming force (5), applied by means of one of the at least one hemming roller (151, 152, 153), for a following hemming operation by way of a changed actuation of the hemming robot (4) in such a way that the force profile of the following hemming operation during the hemming operation corresponds as far as possible to the setpoint force profile (8).

6. The hemming robot (4) as claimed in claim 4 or claim 5, characterized in that the computing unit (12) is configured, furthermore, to detect an overload, which occurred during a hemming operation, in relation to the hemming robot (4) by evaluation of the sensor signals, and to adapt a hemming force (5), applied by means of one of the at least one hemming roller (151, 152, 153), for a following hemming operation in such a way that a sustained overload in relation to the hemming robot (4) is prevented.

7. The hemming robot (4) as claimed in one of the preceding claims, characterized by a communications interface which is configured to transmit sensor signals detected by the at least one sensor element (17) via a communications network to a remote computing unit.

8. The hemming robot (4) as claimed in one of the preceding claims, characterized by a plurality of hemming rollers (151, 152, 153) of different configuration which are arranged on the head element (13), wherein the hemming robot (4) is configured to carry out different hemming operations by means of the hemming rollers (151, 152, 153) of different configuration.

9. The hemming robot (4) as claimed in one of the preceding claims, characterized in that the hemming robot (4) is configured to be operated according to a method as claimed in one of claims 11 to 16.

10. A method for modernizing a hemming robot (4) with a robot hemming head (1) comprising an attaching element (16), a first connecting element, a head element (13) and at least one hemming roller (151, 152, 153), wherein the first connecting element is arranged between the attaching element (16) and the head element (13), and the at least one hemming roller (151, 152, 153) is arranged on the head element (13), characterized in that the first connecting element is removed and is replaced by a second connecting element (11), wherein at least one part of the second connecting element (11) is configured as a measuring element (111) from struts (1111) which are connected to one another and form a framework structure, wherein the measuring element (111) is configured with at least one sensor element (17), arranged on the measuring element (111), for the detection of a hemming force (5) exerted on a hem flange by means of one of the at least one hemming roller (151, 152, 153) during a hemming operation, and wherein a hemming robot (4) as claimed in one of claims 1 to 9 is produced by way of the modernizing.

11. A method for operating a hemming robot (4) with a robot hemming head (1), in particular a hemming robot as claimed in one of claims 1 to 8, wherein the robot hemming head (1) comprises an attaching element (16), a connecting element (11), a head element (13) and a plurality of hemming rollers (151, 152, 153), wherein the connecting element (11) is arranged between the attaching element (16) and the head element (13), and the hemming rollers (151, 152, 153) are arranged on the head element (13), characterized in that an elastic deformation of the connecting element (11) is detected during a hemming operation, wherein an intermediate piece of the connecting element (11) or the complete connecting element (11) is configured as a measuring element (111) from struts (1111) which are connected to one another and form a framework structure, wherein the measuring element (111) is of elastically deformable configuration in all three spatial directions, and a hemming force (5), exerted on a hem flange by means of a hemming roller (151, 152, 153) of the hemming robot (4) during the hemming operation and a force vector for the hemming force (5) in all three spatial directions are determined from the detected elastic deformation.

12. The method as claimed in claim 11, characterized in that, during a hemming operation, a hemming roller (151, 152, 153) of the hemming robot (4) is moved along a component (2) according to predefined waypoints, wherein the determined hemming force (5) is assigned to the respective waypoints for the determination of an actual hemming force profile (9).

13. The method as claimed in claim 12, characterized in that the determined actual hemming force profile (9) is compared with a setpoint hemming force profile (8) which is predefined for this hemming operation, and deviations between the determined actual hemming force profile (9) and the setpoint hemming force profile (8) for the respective waypoints are determined.

14. The method as claimed in claim 13, characterized in that the hemming force (5) exerted on the hem flange by the hemming roller (151, 152, 153) is adapted for a following hemming operation in such a way that the deviations which are determined in relation to the hemming operation which was previously carried out are reduced.

15. The method as claimed in claim 14, characterized in that a movement path, predefined for the hemming robot (4), of the robot is changed for the adaptation of the exerted hemming force (5).

16. The method as claimed in one of claims 11 to 15, characterized in that, for a hemming operation which is carried out, an occurrence of an overload in relation to the hemming robot (4) is checked using the determined hemming force (5), and, if an overload is detected, a following hemming operation is adapted in order to avoid the overload.