DE102006056051B4 - Robot with control for additional axes - Google Patents

Abstract

Robot comprising a controller (16) for controlling robot axes by means of electric drives and comprising a connecting device (1) for connecting components, wherein the connecting device comprises a first and a second connecting element (4,6), both by means of a first and second electrical Drive (8,10) are electrically movable, wherein the controller (16) comprises a means for controlling and coordinating movements between the electric robot axis drives and the electrical drives (8,10) of the connecting elements (4,6), wherein the coordination The motion sequences include that at least parts of the movements caused by the electrical drives (8, 10) of the connecting elements (4, 6) can already be performed when the connecting device (1) approaches by means of the electric robot axis drives, and the electric drives (8, 10 ) of the connecting elements (4,6) are designed, the Verbind Starting from a parking position (22), the control elements (4, 6) are firstly controlled by torque limitation in an intermediate position (23, 24) and then the connecting elements (4, 6) are successively controlled to a position in which the control (16) a process torque for connecting the components is exercised.

Description

The invention relates to a robot and a method for controlling a connection process, by means of this robot.

In the prior art robots are known which control additional axes except the actual robot axes.

The font US 6,787,729 B2 refers to a robot with welding tongs. The robot is movable over a variety of axes. In addition, the arms of the welding gun by means of a linear actuator are relatively movable. Through a control both the arms of the welding gun and a movement of the robot can be controlled.

The font DE 103 38 176 A1 discloses a method and apparatus for controlling the pressing force of the electrodes of a welding gun driven by an electric motor, in particular an industrial robot. The font EP 1 425 129 B1 discloses a forceps for a robotic device with a device for adjusting and balancing.

The font DE 690 22 407 T2 describes a follow-up control system for an additional robot axis by means of an additional axis control, which is included in a robot controller.

Also known are robots that perform pliers-like devices for connecting materials, wherein the individual pliers of the device are moved by means of a separately controlled Hauptthub- and balancing drive.

The disadvantage of the last-mentioned prior art is that the approach of the device to a workpiece to be machined must be simulated by means of a coordinated movement of the robot axes. As a rule, 6 robot axes are required for the robot to reach all spatial points within its predefined range of motion. This process is very time consuming and inaccurate, since large leverage forces act. The approach of the device to the material to be processed is therefore time-consuming and inaccurate. This can also cause damage to the material to be processed, since the pliers are more or less uncoordinated or very coarse co-ordinated approached to the material and, for example, can impress a thin sheet to be processed.

The invention is therefore based on the object, starting from the last-mentioned prior art to realize a robot, which offers over the prior art increased cycle times and improved processing quality.

To solve this problem, a robot and a method according to the independent claims is proposed.

This solution has over the prior art has the advantage that due to the existing means for controlling and coordinating the movement between the electric robot axis drives and the electrical drives of the connecting elements in real time a coordinated approach of the tong-like connection device to a workpiece by means of interpolation of the robot axis movements and Main lift and compensation drive movement is enabled. The coordination of the movement processes comprises that at least parts of the motion sequences effected by the electrical drives of the connecting elements can be carried out already when the connecting device approaches the means of the electric robot axis drives.

The points to be machined on the workpiece can be approached more precisely and already at the approach of the next point, the connection device can be aligned for the next step. This increases the quality of the connection, shortens the cycle times, avoids damage to the workpiece and thus solves the task.

Further preferred embodiments are the subject of the dependent claims.

Preferably, the coordination of the movement sequences by means of a higher-level arithmetic unit, said superordinate arithmetic unit further computing units for calculating the individual Movements of the axes are assigned and the communication between the processing units by means of a real-time data connections takes place. This distributes the computing load of the CPUs. While the higher-level CPU or the higher-level microcontroller performs coordination tasks for all axes and drives, each individual axis or drive has its own computing capacity, eg in the form of an additional controller or additional CPU for control tasks and / or motion calculations for individual axes or drives assigned. The communication of the arithmetic units by means of a real-time bus enables a fast and effective data exchange, so that the superordinate arithmetic unit can transmit the movement sections to be executed by the drives for realizing the superordinate trajectory to the arithmetic units assigned to the drives.

Advantageously, each drive is assigned its own arithmetic unit, wherein these arithmetic units are in direct communication with one another, in particular by means of a real-time communication connection. This relieves the higher-level arithmetic unit.

The first connecting element preferably represents a first welding electrode and the second connecting element preferably represents a second welding electrode, wherein both electrodes are covered by welding tongs. Precisely in welding processes, an exact approach of the electrodes to the workpiece is decisive for the quality of the welded connection achieved. The invention therefore achieves its advantageous effect, especially in connection with welding operations. Other joining operations could be riveting, gluing, pressing, or clinching.

If at least one drive causes a relative movement of both welding electrodes of the welding tongs (main stroke) to each other and at least one drive causes a movement of the entire welding tongs (compensation), then the welding tongs as a whole can already be exactly aligned with them during the approach to the workpiece to be machined , To carry out the welding operation, the welding process can then be started quickly by activating the Hauthub drive, which brings together the pliers, depending on the position of all other drives.

Preferably, the controller comprises means for controlling the welding operation and means for coordinating the welding operation with the movements required for the approach of the pincers to the workpiece. Complex current / time / force profiles can be driven by the robot by optimizing the welding current, depending on the current position of the welding gun and the contact pressure, and thereby positively influencing the welding quality. The controller could additionally take over the quality inspection of the welded connection by means of ultrasound.

Alternatively, the robot controller could be connected by means of a data bus to a welding controller in order to relieve the robot controller of the computing capacity.

The object is also achieved by means of a method for controlling a connection process by means of a robot according to claim 8. There are the same advantages as mentioned above.

The connection process may be a resistance welding operation, wherein the connection device is a welding gun and one drive is the main drive and another drive is the balancing drive of the welding gun, the control preferably additionally controlling the welding current in dependence on the drive of the drives Trajectory takes over, in order to be able to run complex power / current / time profiles in a time-optimized manner.

Further advantages and embodiments will become apparent from the accompanying drawings.

• 1 eine schematische Darstellung einer erfindungsgemäß angesteuerten Schweißzange;
• 2 ein Blockdiagramm zweier direkt kommunizierender Recheneinheiten;
• 3 eine schematische Darstellung eines Schweißvorgangs mit einer erfindungsgemäßen Schweißzange; und
• 4 ein Ablaufdiagramm für einen erfindungsgemäßen Schweißprozess.
• 5 eine Robotersteuerung mit 8 Achsen.
• 6 eine Robotersteuerung mit 8 Achsen und integrierter Schweißsteuerung.

Show:

• 1 a schematic representation of an inventively controlled welding gun;
• 2 a block diagram of two directly communicating computing units;
• 3 a schematic representation of a welding operation with a welding gun according to the invention; and
• 4 a flow chart for a welding process according to the invention.
• 5 a robot control with 8 axes.
• 6 a robot control with 8 axes and integrated welding control.

1 shows a schematic representation of a welding gun 1 , This welding gun 1 has a first electrode 4 , which is also referred to below as the main lift electrode and a second electrode 6 , which is also referred to below as a compensating electrode, on. The reference number 8th refers to a first drive or main lift drive, which is the first electrode 4 or whose movement controls. Via a second drive or the compensation stroke 10 Both are welding electrodes 4 and 6 emotional. In this case, a joint device 5 is provided for stabilizing the device.

2 shows a block diagram with two computing units according to the invention. Here are the two drives 8th . 10 ie the main lift drive 8th and the compensation drive 10 and their respective servomotors 7 . 9 from a first arithmetic unit 12 and a second arithmetic unit 14 controlled. The reference numeral 16 refers to a higher-level control device which can also control robot axes (not shown). This in 2 Subsystem shown therefore consists of a master unit 12 and a slave unit 14 as well as from the servomotors 7 . 9 , This system communicates with the master unit via a fieldbus interface (eg Profibus-DP) 12 and a communication link 15 with the higher-level controller 16 , The drive algorithm mentioned in more detail below is in the master unit 12 implements and runs there. Between the two units 12 and 14 a communication link 18 is provided which allows real-time communication between the two units. In this case, for example, SERCOS III, TCP / IP and Ethernet can take place in this real-time communication. However, other platforms are also conceivable. The direct communication connection causes a discharge of the higher-level control device 16 regarding the required computing capacity.

This allows the unit 12 to all relevant data of the slave drive or the second unit 14 access. Examples of such relevant data are e.g. The actual torque value, the actual velocity value and the actual position value. The access takes place in real time or within a predeterminable deterministic time span. Conversely, the second unit can do the same 14 to the corresponding data of the first unit 12 access.

In the embodiment shown here, this is the main lift drive 8th controlling computing unit configured as a master. However, it is also possible to configure the compensation drive 10 driving unit as a master and to configure the first unit or the main drive as a slave. Communication takes place via a real-time bus (eg SERCOS III) or through the implementation of drive electronics on a common platform. Considered, for example, a Doppelachsmodul with integrated drive control electronics cards.

A rough procedure of a welding process according to the invention can be described as follows. The higher-level control device 16 sends the command "Close Forceps" to the first unit 12 , As a result, the self-contained system closes the clamp according to the internal drive algorithm described below. After this is done, the first unit reports 12 to the control device 16 in that the pliers are closed. As a result, the control device initiates 16 the welding process and then transmits the command "open pliers" to the first control device 12 , Subsequently, the self-sufficient system opens between the two drive control devices 12 . 14 the pliers according to a predetermined driving algorithm. Finally, from the first drive control means 12 to the main control means 16 the information "pliers open" transmitted.

Under. Reference to the 3 and 4 and the following tables will now explain the exact welding process in detail. At the beginning of the welding process are both the first electrode 4 as well as the second electrode 6 in their respective parking positions. The parking position of the first electrode 4 is indicated by the reference numeral 22 and the parking position of the second electrode 6 by the reference numeral 21 ,

After the control device 16 has transmitted the start command to the first drive control device 12 (cf. 4 ), the first electrode 4 becomes the main lift intermediate position 24 and the second electrode 6 in the compensation intermediate position 23 hazards.

In the following explanation, Table 1 illustrates the movement of the compensation stroke 10 and the second drive and Table 2 the movement of the main lift 8 and the first drive. The invention makes it possible for at least parts of these movement sequences to be carried out as soon as the welding tongs approach the workpiece by means of the robot. The respective adjustable parameters are marked in bold type: Table 1: Movement of the compensation (Ag) Move compensation to compensation intermediate position AG torque limitation to the BALANCING MOTION, drive in position control Balancing Find sheet metal AG torque limitation to BALANCING FINDING TORQUE, drive is running in speed regulation Balancing sheet found (input condition) AG torque actual value greater than or equal to BALANCE FINDING TORQUE Balancing sheet metal found Compensation in position control to the current position with AG PROCESS MOMENT Waiting for main lift Opening threshold reached (initial condition) HH actual position value less than or equal to OPENING SWIVEL_ main stroke Balance back to parking position Balancing AG torque limitation to the BALANCING OPERATING TORQUE, drive in position control Table 2: Movement of the main lift (HH) Drive main lift to intermediate compensation position HH torque limit to the HAUTHUBFAHRMOMENT, drive in position control Waiting for compensation sheet found AG torque actual value greater than or equal to BALANCE FINDING TORQUE Main lift find metal HH torque limit on MAIN HUB BINDING DETERMINENT, drive in cruise control Main stroke sheet metal found HH torque actual value greater than or equal to HOB momentary torque strength building Speed control with HH-PROCESS-TORQUE and HH-POWER ATTACHMENT SPEED holding force Speed control with HH-PROCESS-TORQUE and HH-POWER-SPEED SPEED force reduction Cruise control with HH-POWER REDUCTION SPEED Main lift back to HH torque limit on the parking position HAUTHUBFAHRMOMENT, drive in position control

As in 4 shown, the first electrode is in this main lift intermediate position 24 held and only the second electrode or compensating electrode 6 actuated. More specifically, the second electrode 6 pressed here until the component to be welded was found. In this case, the moments, ie the moments of motion of the compensation electrode are limited to a predeterminable compensation torque and the drive of the second electrode 6 takes place here in position control. In order to find the workpiece or sheet to be machined, the moment of Ausgleichshubs (second drive control device) is limited to the Ausgleichblechfindemoment and the drive 8th drives in cruise control. As soon as the actual moment, ie the torque actual value, is greater than or equal to the compensating plate-finding torque, this is an indication that the component is moving away from the second electrode 6 was found. The corresponding moments and position values are transmitted to the first drive control device. Optionally, there is still a compensation in position control of the compensating electrode or the second electrode 6 instead, here is one also certain process torque of the compensating electrode can be specified. In this position, the second electrode 6 held and now the movement of the first electrode 4 be controlled or regulated.

Again, first the moment of the main lift or first drive 8th limited to a given Haupthubfahrmoment and the first electrode 4 driven in position control. In this position, it is waited until the compensation electrode 4, the sheet 20 (see. 3 ), as described above. In this process step both movements can take place simultaneously. In a further step, the actual torque of the main lift is checked and maintained until it is greater than or equal to a predeterminable main tread finding moment. Once this is achieved, this is an indication that even from the main electrode 4 the component to be welded was found.

In a further process step (cf. 4 ) is then transmitted to the main control device the information that the sheet has been found and now a force can be built. More precisely, a speed control of the first drive now takes place 8th with the process torque of the main lift and with the main tower power build-up speed. To the main control device, a signal for indicating the state "holding force" is transmitted. The force retention takes place via a speed control with the process moment of the main lift and with the force holding speed of the main lift. In this process step, the main controller initiates the welding command. Following this command, the force on the components to be welded is reduced again, whereby a speed control with the Haupthubungskraftabbaugeschwindigkeit takes place here.

Finally, the main lift moves back to the parking position, with a torque limitation to the above-mentioned Haupthubfahrmoment and a drive in position control here. Also, the compensation stroke moves, as soon as the information was determined to him that the main lift has reached its opening threshold, back to the parking position. After a break, the system is ready for the next cycle. This break is optional and may need to be respected to protect the motors from thermal overload. After the pause, the information "ready for next cycle" is transmitted to the main controller 16, and vice versa, the main controller may give the start command for another welding operation.

This refers to in 3 the reference number 25 on the opening threshold of the main lift and the reference numeral 20 on a sheet, which is located in a tolerance window. Therefore, as compared with the above-mentioned prior art, the "rigidity" of the process can be adjusted. In other words, the torque limit of one or the servo drives acts like a spring whose stiffness can be adjusted. As a result, an adaptation to the required compensation torque is possible, wherein the pliers space position determines the necessary compensation torque.

All disclosed in the application documents features are claimed as essential to the invention, provided they are new individually or in combination over the prior art.

In 5 is the control according to the invention encompassed by the robot 26 for controlling the robot axes by means of electrical drives shown. The robot includes welding tongs, eg like out 1 can be seen, for connecting components, wherein the pliers a first and a second connecting element 4 . 6 comprising, both by means of a first and second electric drive 8th . 10 are electrically movable, wherein the control means for controlling and coordinating the movement between the usually six electric Roboterachsantrieben and the two electrical drives for the connecting elements of the welding gun 4 . 6 in real time, so that in total can be spoken by a robot controller with eight axes. Six of these eight axes are used to control the robot and two to control the welding gun. By means of a fieldbus 27 and the communication line 15 communicates the robot control 26 with the welding control 30 ,

6 shows a robot controller, in which the function of a welding control is integrated. All other components are identical to those in 4 illustrated arrangement.

LIST OF REFERENCE NUMBERS

1

welding gun

4

first electrode (main lift electrode)

5

joint device

6

second electrode (equalizing electrode)

7, 9

Servo motors (master / slave)

8th

first drive (main drive)

10

second drive (compensation drive)

12

first arithmetic unit for compensation (master)

14

second arithmetic unit for main lift (slave)

15

communication link

16

Higher level control

18

Real-time communication connection

20

sheet

21

Parking position of the second electrode 6 (Compensation)

22

Parking position of the first electrode 4 (Main lift)

23

Balancing intermediate position (compensation)

24

Main lift - intermediate position (main lift)

25

Opening threshold of the main lift (first drive)

26

Robot with control

27

fieldbus

HH / 28

Main lift

Ag / 29

compensation

30

welding control

Claims (10)

Robot comprising a controller (16) for controlling robot axes by means of electric drives and comprising a connecting device (1) for connecting components, wherein the connecting device comprises a first and a second connecting element (4,6), both by means of a first and second electrical Drive (8,10) are electrically movable, wherein the controller (16) comprises a means for controlling and coordinating movements between the electric robot axis drives and the electric drives (8, 10) of the connecting elements (4, 6), wherein the coordination of the movement sequences comprises that at least parts of the movements effected by the electric drives (8, 10) of the connecting elements (4, 6) can already be carried out when the connecting device (1) approaches by means of the electric robot axis drives, and wherein the electric drives (8, 10) of the connecting elements (4, 6) are designed to control the connecting elements (4, 6) initially from a parked position (22) by limiting the moment to an intermediate position (23, 24) and then the connecting elements (4,6) one after the other into a position in which a control torque (16) is to be exerted by the control (16) for connecting the components. Robot after Claim 1 , wherein the coordination of the movement sequences by means of a higher-order arithmetic unit (16), said superordinate arithmetic unit (16) further computing units for calculating the individual movements of the robot axes and the drives of the connecting elements (4,6) are assigned and wherein the communication between the arithmetic units by means of a real-time capable data connections. Robot after Claim 2 , wherein each drive (8, 10) is assigned its own arithmetic unit (12, 14) and wherein these arithmetic units (12, 14) are in direct communication (18) with one another, in particular by means of a real-time communication connection (18). Robot according to one of the preceding claims, wherein the first connecting element (4) is a first welding electrode and the second connecting element (6) is a second welding electrode and both electrodes are covered by welding tongs (1). Robot after Claim 4 , wherein at least one drive (8, 10) causes a relative movement of both welding electrodes (4, 6) of the welding gun (1) to one another and at least one drive causes a movement of the entire welding gun (1). Robot after Claim 4 or 5 wherein the control comprises means for controlling the welding operation and means for coordinating the welding operation with the movement sequences. Robot after Claim 4 or 5 wherein the controller is connected by a data link to a welding controller. Method for controlling a connection process by means of a robot, which comprises a connection device (1), wherein the control, in addition to the control of robot axis drives, also controls the drives (8, 10) for actuating the connection device and controls the motion sequences of the drives (8, 10) coordinated with each other such that their movement leads to a predeterminable trajectory, wherein the coordination of the motion sequences takes place in such a way that at least parts of the movements effected by the electric drives (8, 10) of the connecting elements (4, 6) are already carried out as the connecting device (1) approaches the components by means of the electric robot axis drives, and wherein the electric drives (8, 10) of the connecting elements (4, 6) control the electric drives (8, 10) of the connecting elements (4, 6) in such a way that the connecting elements (4, 6) initially start from a parking position (22) Move by torque limiting in an intermediate position (23, 24) and then move the connecting elements (4,6) successively in a position in which of the control (16) a process torque for connecting the components is applied. Method according to Claim 8 , wherein the connection process is a resistance welding process and the connection device is a welding tongs (1), one drive representing the main drive (8) and another drive the balancing drive (10) of the welding tongs. Method according to one of Claims 8 to 9 wherein the controller additionally takes over the control of the welding current as a function of the trajectory driven by the drives, and / or wherein the controller derives a force and / or current and / or time profile.

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