DE2513655A1 - Machine tool control with TV cameras - has sensor arrangement for controlling programmed auto handling systems - Google Patents

Abstract

The sensor arrangement for controlling auto handling systems by means of T.V. cameras feeds the picture into the programme of the handling system by limiting some of the tool (object) positions to a few T.V. lines at significant points during the determination of the type of tool and its positioning. This simplifies the identification procedure with less apparatus. The procedure involves feeding back of the signal for evaluation of the T.V. line dater. The programming is made in a picture-screen-service-dialogue and the evaluation circuit for each object comprises a fixed number of building blocks programmed to the objects. there are usually more than one T.V. camera which pick up the object with a shine through or illumination light. the correct position of the object is determined by the occurrence of the maximum intensity of the video-signal and the receiving angle.

Description

Sensor system for controlling automatic handheld systems using Television camera The invention relates to a sensor system for determining type, orientation and position of a workpiece or tool with one or more television cameras and a simplified and programmable electronic evaluation process, especially for the control of automatic handling devices (industrial robots).

The handling devices in practical use today do not have their own recognition devices. This requires that in one Variety of cases human help is needed to put work pieces in their To recognize the position (classification), to align in its position, to find its position and to offer them to the handling system in an orderly manner. The technical solution to these tasks removes what is often the only obstacle to automation in assembly and production with handling devices and frees people from monotonous work.

It is common in mass production to carry out the tasks mentioned purely mechanical organizing devices (e.g.

Sponsors). The workpiece-specific order elements used must with a workpiece change with high development or adjustment effort be replaced. This is uneconomical for small and medium series. Farther there are workpieces that cannot be mechanically arranged, so that for this work human involvement is essential.

In the patent application P 24 26 199.3 a method is described, in which the separated workpieces lying on a conveyor belt against a stop be guided.

As a result, there are only a limited number of discrete position classes of the workpieces possible. The classification and position determination is carried out with the help an incoherent optical correlator as a sensor system. The structure of this correlator Conditionally mechanically moving parts such as oscillating mirrors or rotating discs. the Changeover to other workpieces takes place by exchanging the rotating disk, on which the individual location classes are stored photographically. In the for the Electronic programming of the handling system is a necessary learning phase anyway This photographic process can be (teach-in) as opposed to electronic Don't integrate opportunities.

In addition to the mechanical ordering devices and the optical correlators there is the class of "intelligent robots" who work with television systems. The previous developments in this area are not suitable for application industrial handling systems. Above all, it is used in a dangerous environment (marine and space research, disaster relief radioactive contamination etc.) in the foreground. All ~ Intelligent Robots " because of the complex tasks involved in complex and expensive computer systems controlled.

The same goes for those familiar today with television cameras controlled handling systems. These systems are true for use on industrial Handling systems designed, but also require memory-intensive digital computers to carry out the recognition process. A typical example is a programmable one Called assembly machine (Heginbothan, W.B. et al., The Nottingham Sirch Assembly Robot, Paper R 9 lst Conference on Industrial Robot Technology, 1973).

The entire outer structure of the workpiece is displayed here during the detection process processed. This requires a large amount of computation and, accordingly, a complex computer necessary The invention is based on the object of simplifying the recognition process and to reduce the outlay on equipment.

This object is achieved in that the image of the objects to be handled are scanned with one or more television cameras, with only a few lines of the television picture for the recognition and measurement process can be used. Only those lines are selected for which significant Workpiece features are recorded. Examples of such features are: Angles of edges, dimensions of the outer contour, dimensions of special recesses, Differences in recesses or inner contours and outer contours, surfaces and that Presence or non-presence of workpiece-detecting television lines. It can be both workpieces that are lying on a conveyor belt against a stop are performed, so that according to the application P 24 26 199.3 discrete Location classes are formed, which are classified by the method and in their Position are measured so that the gripper of the handling system accordingly can be controlled by an assigned gripping program. The procedure is however not just limited to workpieces that are lying on a conveyor belt against one Stop. Relative positions of workpieces can be used in the same way or tools are determined, at the same time in. the previously described Way a workpiece recognition can be carried out. Such tasks especially with automatic joining processes, which are then followed by a further processing step, e.g. welding the parts together. Here it is possible with two Television cameras to measure three-dimensional coordinates of the day.

To carry out the method according to the invention, the to be recognized Objects viewed either in transmitted light or in incident light.

A major advantage of the sensor system is that it allows for detection of the aforementioned features only counting processes are required, because of the Restriction to a few features, there are also only a few counting results. Counting results are easy to realize with the help of digital electronics the small number of counting results to be processed means a data reduction and thus a decrease the required storage space.

When carrying out the recognition process (classification) according to the invention the stored current counter readings are compared with the specified target values (electronic correlation) and decided on the class with maximum agreement.

Included in the implementation of the position determination according to the invention the time difference between the start of the line or any other start time and the arrival of one or more television lines on the workpiece or tool if the line scanning speed is known, the information about the workpiece or tool position.

An additional advantage that can be achieved with the invention is insensitivity of the sensor system against interference from the television camera. By giving up on the detail recognition and selection, which is unnecessary for the present application Significant features with relatively large geometrical dimensions are linearity and line errors of the television camera as well as the limited resolution are meaningless.

Another essential characteristic of the sensor system according to the invention is the easy programmability. At the same time with the desired flexibility of handling systems for use with different workpieces and handling processes have to the pattern-recognizing sensor systems can also be programmed. With the multitude of possible workpieces and handling processes is with a universal applicability of the sensor system, a slight adaptation to the respective task is desirable. The programming of the sensor system is possible according to the invention in that at a combination of predefined counting circuits, memories and logic Assemblies all unchangeable functions are hard-wired.

The line selection, the choice of the selected by a counting process Characteristic to be recorded measured variable and the logical decision level is known in For example, programmed via crossbar distributors with diode plugs. For this purpose, part of the evaluation circuit necessary for the measuring and recognition process is required the same for all objects and accordingly hard-wired. Part of the circuit However, it is designed to be flexible thanks to variable plug-in connections, so that an object-dependent Programming by means of plug connections is possible.

The programming via microprocessors is in the same way according to the invention or sequence controls (microcontrollers) are possible in which the programming instructions are set in easily exchangeable read-only memories.

According to the invention, the input required for the classification can be Setpoints are done in two ways.

On the one hand, it is possible to take the setpoints from the respective workpiece data to be determined and to be entered permanently in the memory. It is also possible to set the setpoints to be entered through a direct screen operator dialog. This process corresponds to that of the actual programming (teach-in) of the handling systems. Here will be the television camera, depending on the handling task, the various objects one after the other or object were offered. With the help of a monitor image, one of which can be moved arranged line e.g. by blanking this line marked the operator brings the marked line to the desired significant one Place of the object.

At the push of a button, the results are shown as counting results in this line The resulting sections of the black-and-white lines of an image that appears, for example, in transmitted light Object entered into the setpoint memory. This will be for every possible location class repeated.

The sequence control of the recognition process and the logical decisions takes over a microprocessor, which in many cases a pure sequence control (microcontroller) can be. In this case, the entire program information is stored in a known manner stored in a read-only memory. Depending on the task, this memory is filled with the Program information exchanged. Due to the data reduction achieved according to the invention the memory space for commands and data is low.

An embodiment for a workpiece classification and a An exemplary embodiment for the relative positioning of workpieces is shown in the drawing shown and described in more detail below.

1 shows the data reduction carried out using an example by limiting it to a few television lines at significant workpiece locations with the task of workpiece classification and position determination.

Fig. 2: An example of the application of the method for relative positioning of workpieces.

Fig. 3: The plan view of the arrangement for Relativposi tioning of Workpieces Fig. 4: a block diagram of the sensor system.

To carry out the method according to the invention for classifying workpieces and position determination is that shown in FIG. 1, for example, as an angle The workpiece is guided against a stop 1 in a known manner. This results in the six stable contact positions L1 - L6 shown. When capturing this Image with the help of a television camera perpendicular to the image plane is one Image resolution of 625 lines per image section possible. Of these 625 possible According to FIG. 1, the four non-equidistant lines Z1-Z4 are picked out. As will be shown in the following, these four lines are sufficient for a complete one Description of the possible location classes L1 - L6. This means an essential Effort and data reduction and accordingly leads to a simplification of the sensor system.

It can be seen from Fig. 1 that only the lines Z1 and Z2 the work piece record layers L1 and L2. In the video signal of the television camera causes the presence of an object in the relevant scanning line shows a significant change in level. I) the presence of such a level change in a line is stored.

The decision as to which of the two possible layers L1 or L2 is present, is hit at the second TV line Z2. When everyone starts running together Television lines from a starting mark 2 (Fig. 1) hits based on this starting point in position 1.1 the line Z2 on the workpiece earlier than the line Zl in the This is reversed in position L2. By recording the times of impact of lines Z1 and Z2 on the workpiece by means of counters triggered by the video signal Location L1 or L2 can be decided. In the same way it is possible to choose from the different To determine the remaining position classes L3 - L6.

In the present example, the previously mentioned features only the angles of workpiece edges and the presence or the absence of workpiece detecting television lines is exploited.

In the same way it is possible by using other features perform the recognition process.

In this way, the positions L3 and L4 can be distinguished from the positions L5 and L6 that by counting the different widths of the outer contours or the presence of a recess in the workpiece at positions L5 and IJ6 can be determined in line Z3.

For the recognition process (classification) the saved current meter readings compared with specified target values (electronic correlation) and decided on the class with maximum agreement.

The position of the workpiece is measured from the time period (Counting process), for example the line Zf, which shows all workpiece positions L1 - L6 recorded, required from starting point 2 to the workpiece.

Now the workpiece position and workpiece position are known, so do so with them Data of the gripper of the handling system according to the preprogrammed for each position class Gripping movement can be controlled.

The programming of the control system to be carried out for each workpiece can on the one hand with a previously defined line selection from the geometric Dimensions are made. in the present example these are, for example, the path differences of the individual lines or the width of the outer contours. It is also possible by means of a monitor image in a screen operator dialog for each workpiece position by means of a movable monitor line marked by blanking to scan the significant parts of the workpiece and directly those from the video signal to save triggered black-and-white areas of the respective line as target values.

As a further example of the applicability of the procedure to not The discrete position classes present in FIG. 2 show the relative positioning of workpieces detailed.

The workpiece 3 is for example on a conveyor belt 4 on a Holding device 5, for example a magnetic or vacuum device, put on. The workpiece can be placed in any position. In or on the Workpiece is a significant feature.

In the example, this is a rectangular workpiece recess 6.

If the workpiece is viewed in transmitted light, this recess appears as a light spot on the dark workpiece. It does not have to be cutouts act, which is translucent at this point. In the same way it can too be an opaque indentation or elevation. Located in the workpiece an opening 7, which is not visible in the side view, is to be placed in this opening a very specific workpiece 8 can be inserted by a feeder 9. This object is achieved in that the workpiece 3 of a Line Z1 of a television camera is scanned. This television line is positioned like this that it covers the significant recess 6. By turning the bracket 5 through the handling system up to the maximum detected and known from the television line Dimension of the inner contour 6, the position is vertical except for a parallel shift captured to the plane of the drawing.

For example, if the significant feature is a opaque recess or an elevation is used as a setpoint for the rotation of the workpiece the maximum intensity of the video signal at the glancing angle the end.

In Fig. 3, the top view of the arrangement is for clarity the workpiece 3 and the television camera 10 shown. The camera 10 detects in the described Way against a screen illuminated from the back by a lamp 11 12 recess 6, brightly lifted from workpiece 3.

Occurs after aligning the workpiece through the described Rotation one more degree of freedom through a possible parallel shift in the y direction on so can this with a perpendicular to the first television camera 10 arranged second camera 13 capture by a single line that the outer contours of the workpiece.

Because of the rigid and known relative position between the mark 6 and the workpiece opening 7 (Fig.2) it is now possible to use the feeder 9 to be controlled so that the workpiece 8 can be inserted into the opening. Here it is possible, through a second line Z2 of the first television camera 10, the brought Classify and align workpiece in the same way. So is it is also possible, for example, to manipulate 8 differently depending on the type of workpiece undertake, for example, to use in different openings of the workpiece 3.

The position in the x-direction results in the manner described from the Time interval between the television lines Z1 and Z2 from the starting mark 14 (FIG. 2).

4 shows a block diagram of the sensor system. That Image captured by a television camera 15 is converted into the Video signal and the line pulses. The video signal is used for control a trigger stage 17 for black and white transitions of the image and for controlling a Trigger level 18 for white-black transitions of the scanned image. These stages control the counting pulses generated by an HF oscillator via a start-stop circuit 19 20 can be entered into a counter 21. The count results are for each row entered into the actual value memory 23 when the switch 22 is in the specified position. The desired television lines are after the pulse separation stage 16 via a line counter 24 and a line decoder 25, which is used to select the desired lines, stored in a line memory 26. Via a coincidence circuit 27 that from the control unit 28, the programmable read-only memory 29 and the input / output logic (Decision stage) 30 existing microprocessor control commands fed. This microprocessor in turn controls according to the flexible and programmable Read-only memory 29 the measuring process and hits in the input-output logic by comparison the content of the actual value and setpoint memory makes the decision on the position class. The position of the workpiece is for a specific line in the actual value memory 23 recorded, from which in a circuit 53, for example, the position of the center of gravity can be determined. The image from the television camera is used to program the sensor system 15 observed on the monitor 31, the desired line set with the line counter 24, and the setpoint values of the workpiece dimensions after switching the switch 22 to Setpoint memory 32 entered.

Claims (9)

Claims 1. Sensor system for controlling automatic handling systems by means of a television camera, characterized in that the type, orientation and position of a workpiece or tool - referred to below as an object - with known By evaluating a few, the significant features of the property were located capturing lines of the television picture takes place and then this measurement result corresponding program of the handling device is initiated. 2. Sensor system according to claim 1, characterized in that the measuring and the recognition process traced back to a recording and evaluation of counting results is, the counting results of the television lines detected distances of the object of a reference mark, angles of object edges, dimensions of object outside or -interior contours, differences between exterior and interior contours and surfaces of the object mean, 3. Sensor system according to claim 1 and 2, characterized in that it is e n n z e i c hn e t that the programming for the various objects in a screen operator dialog takes place, the objects in a learning phase of the television camera in the target positions are offered by the operator by means of a movable controllable and marked Monitor line, the significant object locations are selected on the monitor image and causing the counting results to be stored for the selected lines. 4. Sensor system according to claim 1 and 2, characterized in that the evaluation circuit necessary for the measurement and detection process for each object consists of a fixed number of assemblies in which a part for all objects are hard-wired together, another part through plug-in connections can be programmed depending on the object according to the geometrical dimensions of the object can. 5. Sensor system according to claim 1 to #, characterized in that the sequence of the measuring and recognition process carried out by electronic assemblies programmed using exchangeable read-only memories. 6. 'sensor system according to claim 1 to 5, characterized in that more than one television camera can be used in a spatially offset arrangement. 7. Sensor system according to claim 1 to 6, characterized in that the television camera records the objects in transmitted light. 8. Sensor system according to claim 1 to 6, characterized in that the objects are detected in incident light by the television camera. 9. Sensor system according to claim 8 t d a d u r c h g e k e n n z e i c h n e t that the object position depends on the occurrence of the maximum intensity of the video signal is determined at the glancing angle.