WO2008064727A1

WO2008064727A1 - Robot with a control for additional axes

Info

Publication number: WO2008064727A1
Application number: PCT/EP2007/006555
Authority: WO
Inventors: Ibrahim Doertoluk; Bernd Schnurr
Original assignee: Robert Bosch Gmbh
Priority date: 2006-11-28
Filing date: 2007-07-24
Publication date: 2008-06-05
Also published as: DE102006056051A1; DE102006056051B4

Abstract

The invention relates to a robot comprising a control for controlling the robot axes by means of electric drives. The invention further comprises a connecting device for connecting components, wherein the connecting device comprises a first and a second connecting element (4) (6), wherein both can be electrically displaced by means of first and second electric drives. The control comprises means for controlling and for coordinating the sequences of motions between the electric robotic axes drives and the electric drives of the connecting elements (4) (6) in real time. The coordinated movement of all robot axes and drives is advantageous.

Description

Robot with control for additional axes

The invention relates to a robot and a method for controlling a connection process by means of this robot as claimed in claims 1 and 7.

In the prior art robots are known which control additional axes except the actual robot axes. For example, document 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 contained in a robot control.

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 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.

Preferably, the coordination of the movement sequences by means of a higher-level arithmetic unit, this higher-level arithmetic unit further computing units for calculating the individual movements of the axes are assigned and the communication between the arithmetic units by means of real-time data connections. 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 individual drive has its own computing capacity, for example. in the form of an additional controller or an additional CPU for control tasks and / or the calculation of motion processes 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 each other, 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 likewise achieved by means of a method for controlling a connection process by means of a robot, which comprises a connection device, wherein the controller also controls the drives for actuating the connection device in addition to controlling the robot axis drives and coordinates the motion sequences of the drives with one another such that their Movement leads to a predeterminable trajectory. There are the same advantages as mentioned above.

For the reasons already mentioned above, the connection process is a resistance welding process, wherein the connecting device is a welding gun and wherein 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 takes over from the trajectory traversed by the drives in order to be able to start time-optimized complex power / current / time profile.

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

Show:

Fig. 1 is a schematic representation of an inventively controlled welding tongs;

Fig. 2 is a block diagram of two directly communicating

Processing units;

3 shows a schematic representation of a welding process with a welding tongs according to the invention; and

4 shows a flow chart for a welding process according to the invention.

5 shows a robot control with 8 axes.

Fig. 6 is a robot controller 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 compensation electrode on. The reference numeral 8 refers to a first drive or the main lift drive, which controls the first electrode 4 and its movement. Via a second drive or the compensation stroke 10, both welding electrodes 4 and 6 are moved. In this case, a joint device 5 is provided for stabilizing the device.

FIG. 2 shows a block diagram with two arithmetic units according to the invention. The two drives 8, 10, ie the main lift drive 8 and the compensation drive 10 or their respective servomotors 7, 9 are controlled by a first computer unit 12 and a second computer unit 14. The Reference numeral 16 refers to a higher-level control device which can also control robot axes (not shown). The subsystem shown in Figure 2 thus consists of a master unit 12 and a slave unit 14 and the servomotors 7, 9. This system communicates via a fieldbus interface (eg Profibus-DP) of the master unit 12 and a communication link 15 with the higher-level control 16. The drive algorithm mentioned in more detail below is implemented in the master unit 12 and is executed there. Between the two units 12 and 14, a communication link 18 is provided, which allows a 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 relief of the higher-level control device 16 with respect to the required computing capacity.

Thus, the unit 12 can access all relevant data of the slave drive or the second unit 14. 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 14 can also access the corresponding data of the first unit 12.

In the embodiment shown here, the arithmetic unit driving the main lifting drive 8 is 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 Antriebssteuerelektronik- cards.

A rough procedure of a welding process according to the invention can be described as follows. The higher-level control device 16 transmits the command "Close pliers" to the first unit 12. In the sequence closes the self-sufficient System the pliers according to the internal drive algorithm described below. After this has been done, the first unit 12 notifies the controller 16 that the clamp is closed. As a result, the control device 16 initiates the welding process and then transmits the "open pliers" command to the first control device 12. The autonomous system then opens the pliers in accordance with a predefined control algorithm between the two drive control devices 12, 14. Finally, the first drive control device 12, the main control device 16 transmits the information "pliers open".

With reference to Figures 3 and 4 and the following tables, the exact welding process will now be explained in detail. At the beginning of the welding process, both the first electrode 4 and the second electrode 6 are 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 controller 16 has transmitted the start command to the first drive controller 12 (see FIG. 4), the first electrode 4 is moved to the main lift intermediate position 24 and the second electrode 6 is moved to the intermediate balancing position 23.

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 indicated by bold type:

Table 1: Movement of compensation (Ag)

Parking position HAUTHUBFAHRMOMENT, drive in position control

Table 2: Movement of the main lift (HH)

As shown in FIG. 4, the first electrode is held in this main lift intermediate position 24 and only the second electrode or compensation electrode 6 is actuated. More specifically, the second electrode 6 is operated here until the component to be welded has been found. The moments, i. H. the movement moments of the compensation electrode limited to a predetermined compensation torque and driving the second electrode 6 takes place here in position control. In order to find the workpiece or sheet to be machined, the moment of the compensation stroke (second drive control device) is limited to the Ausgleichblechfindemoment and the drive 8 proceeds in speed control. As soon as the actual moment, i. H. the torque actual value is greater than or equal to the Ausgleichsblechfindemoment, this is an indication that the component of the second electrode 6 has been 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, in which case a likewise specific process moment of the compensating electrode can be specified. In this position, the second electrode 6 can be held and now the movement of the first electrode 4 can be controlled.

Again, the moment of Haupthubs or first drive 8 is initially limited to a predetermined Haupthubfahrmoment and driven the first electrode 4 in position control. In this position, it is waited until the compensating electrode 4 has found the plate 20 (see Fig. 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 waited until it is greater than or equal to a predeterminable main tread finding moment. As soon as this is achieved, this is an indication that the component to be welded has also been found by the main electrode 4. In a further method step (see FIG. 4), the information is then transmitted to the main control device that the metal sheet has been found and a force can now be built up. More specifically, a speed control of the first drive 8 now takes place with the process torque of the main lift and with the force buildup speed of the main lift. The main control device is provided with a signal for indicating the state "holding force." The force is maintained via a speed control with the process torque of the main lift and with the main shaft holding force speed In this process step, the main control device initiates the welding command Following this command the force is reduced again to the components to be welded, whereby here is a speed control with the Hauptstubraftabbaugeschwindigkeit.

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.

Thus, in FIG. 3, the reference numeral 25 refer to the opening threshold of the main lift and the reference numeral 20 to a sheet, which in a

Tolerance window is located. Therefore, in comparison 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 as a spring whose

Stiffness can be adjusted. As a result, an adaptation to the required balancing torque is possible, wherein the pliers space position the necessary

Compensation torque determined. 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 FIG. 5, the controller 26 according to the invention for controlling the robot axes by means of electric drives is shown. The robot includes welding tongs, e.g. as shown in Figure 1, for connecting

Components, wherein the pliers a first and a second connecting element 4,

6, both of which by means of a first and second electric drive 8,

10 are electrically movable, wherein the control means for controlling and coordinating the movement between the usually six electrical

Robot axis drives and the two electric drives for the

Including 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 field bus 27 and the communication link 15, the robot controller 26 communicates with the welding controller 30.

Fig. 6 shows a robot controller, in which the function of a welding control is integrated * All other components are identical to the arrangement shown in Figure ^ ".

New qualifier list

1 welding tongs

4 first electrode (main lift electrode) 5 hinge device

6 second electrode (equalizing electrode)

7, 9 servomotors (masts r / slave)

8 first drive (main drive)

10 second drive (compensation drive) 12 first calculation unit for compensation (master)

14 second main-hub computing unit (slave)

15 communication connection

16 Higher level control

18 real - time communication connection 20 sheet metal

21 parking position of the second electrode 6 (compensation)

22 parking position of the first electrode 4 (main stroke)

23 compensation intermediate position (compensation)

24 Main lift - intermediate position (main lift) 25 Opening threshold of the main lift (first drive)

26 robots with control

27 Fieldbus HH / 28 Main stroke Ag / 29 Compensation 30 Welding control

401 start

402 compensation in parking position

403 Main lift in parking position

404 Drive Balance to Equalization Position 405 Drive Main Stroke to Main Stroke Position

406 Balancing Find sheet metal

407 waiting for compensation sheet found

408 compensation sheet found

Replacement Blade (RULE 26) 409 Main Hub Find sheet metal

410 main stroke sheet metal found

411 Send to transfer Control: Strength

412 power buildup

413 Send to over. Control: holding power

414 power hold

415 power reduction

416 Main lift back to parking position

417 Waiting for main lift Opening threshold reached

418 Balancing back to parking position

419 compensation in parking position

420 main lift in parking position

421 break

422 Ready for next cycle

423 Send to over. Control Ready for next cycle

424 Waiting for takeoff

425 Start of überg. control

426 In position

427 In position

428 Open command Forceps

Replacement Blade (RULE 26)

Claims

claims

A robot comprising a controller (26) for controlling the 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, characterized in that the controller (26) comprises means for controlling and coordinating the movement sequences between the electric robot axis drives and the electrical drives (8,10) of the connecting elements (4,6) includes.

2. Robot according to claim 1, wherein the coordination of the motion 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 computing units is done by means of a real-time capable data connections.

3. Robot according to claim 2, wherein each drive (8,10) is associated with its own arithmetic unit (12,14) and wherein said arithmetic units (12, 14) in direct communication (18) with each other, ^' in particular by means of a real-time communication connection (18 ).

4. 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 of a welding tongs (1) are included.

5. Robot according to claim 4, wherein at least one drive (8) causes a relative movement of both welding electrodes (4,6) of the welding gun (1) to each other and at least one drive (10) causes movement of the entire welding gun (1).

6. Robot according to claim 4 or 5, wherein the controller comprises means for controlling the welding operation and means for coordinating the welding process with the movement sequences.

A robot according to claim 4 or 5, wherein the controller is connected to a welding controller by means of a data link.

8. A method for controlling a connection process by means of a robot, which comprises a connection device (1), wherein the controller also controls the drives (8, 10) to actuate the connection device in addition to controlling the robot axis drives and controls the motion sequences of the drives (8, 10) coordinated with each other such that their movement leads to a predeterminable trajectory.

9. The method of claim 8, wherein the bonding process is a resistance welding process and the connecting device is a welding gun

(1), wherein one drive represents the main drive (8) and another drive the compensating drive (10) of the welding gun.

10. The method according to any one of claims 8 to 9, wherein the controller additionally assumes the control of the welding current in dependence on the trajectory driven by the drives.

11. The method according to any one of claims 8 to 10, wherein the controller deploys a force and / or current and / or time profile.