System and method for visualization of process errors

#The present application claims priority of European patent application No. 08101548.9 filed on Feb. 13, 2008, the content of which is incorporated herein by reference.

#The present invention relates to a method and a system for visualizing process errors that occur in connection with processing a workpiece by means of a process tool and an industrial robot moving along a path during the processing.

#This invention is useful in connection with any type of processing using an industrial robot, such as welding, painting, polishing, grinding, and deburring.

#The invention will now be explained more closely by the description of different embodiments of the invention and with reference to the appended figures.

#FIG. 1 shows a robot system according to an embodiment of the invention.

#FIG. 2 shows a visualization of the relation between a workpiece, a robot path, and process errors.

#FIG. 1 shows an example of a system for visualizing process errors according to the invention. The system comprises a process controller 1 configured to control a process, such as a painting process or a welding process. The process controller includes hardware such as a processor, memory for storing process control programs, and communication means for communicating with other units. The process controller provides control signals to process equipment in accordance with instructions in the process control program. The process equipment includes a tool 3, for example a paint gun or welding gun, to be carried by the robot and a drive unit 2 for supplying the tool with what it needs to be able to carry out the process, for example equipment for providing paint of a sufficient pressure to the paint gun and equipment for supplying the welding gun with current. The tool carries out the process on a workpiece 4.

#During processing, the tool 3 is moved by a robot 5 along a pre-programmed path on a workpiece. Alternatively, the tool may be stationary and the workpiece is moved by the robot. A robot controller 6 controls the movements of the robot in accordance with instructions stored in a robot program. The robot program defines a movement path to be followed by the robot during the processing. The process controller includes hardware such as a processor, memory for storing process control programs, and communication means for communicating with other units. The robot controller comprises a database 7. For each type of tool a tool centre point is defined in relation to the robot. Commonly, the tool centre point is defined as the tip of the tool 3. For example, if the tool is an arc-welding gun, the tool centre point is defined at the point where the wire exits from the gun. The position of the tool centre point is known in relation to the base coordinate system of robot, and accordingly the position of tool centre point is known in relation to the robot path.

#The process controller 1 is also configured to supervise the process in order to detect errors in the process. Examples of process errors are a deviation in the paint supply, high voltage error during electrostatic painting, wire-feeder motor overload during arc welding. According to this embodiment of the invention, the process controller is configured, upon detecting an error, to send information on the error to the robot controller. The robot controller is configured, upon receiving the information on the error from the process controller, to store the information on the error together with the present tool centre point position of the robot and information identifying the current path followed by the robot in an error log list. Suitably, the error log list is stored in the database 7. The error log list contains information on the error type as well as the TCP position where the error occurred, or at least a reference to where this information can be retrieved. Optionally, information on the path program as well as process parameters are stored together with the error in the error log list.