DE10033608A1 - Securing an area around a machine tool to prevent entrance of personnel and possible injury using artificial light target, the image of which can be compared to a reference value and used to switch off the machine - Google Patents

Abstract

Method for shielding a danger zone (20) around a machine tool (22) in which an optical chamber or area (18) is created in front of the danger zone. An artificial target (16) is placed in a fixed position outside the danger zone, with the target having the form of a defined light signal that is produced using a light source (14). The image of the target is compared with a reference value with any deviation from the reference value indicating an approaching object or person. An Independent claim is made for a device for making an area safe around a machine tool.

Description

The present invention relates to a method for securing a danger zone, in particular the danger zone of an automated machine, an optical barrier being generated in front of the danger zone, with the steps:

• - Arranging an artificial target at a defined bottom sition outside the danger zone,  
• - Capture an image of the artificial target with a Image acquisition unit, and
• - Compare the recorded image with characteristics values of a reference image, the reference image corresponds to an undisturbed image of the artificial target.

The invention further relates to a device for Ab secure a danger zone, especially the danger zone of an automated machine, with one Image acquisition unit and with an artificial target that egg a defined position outside the danger zone is arranged, further with an evaluation unit, which recorded a menes image of the artificial target with characteristic who ten compares a reference image, the reference image ei corresponds to an undisturbed image of the artificial target.

Such a method and such an apparatus are known from DE 196 44 278 A1.

To secure hazardous areas, especially hazards areas of the type mentioned are in the indu In practice, light barriers and light grids have so far predominantly been used or laser scanner used, often in combination with me chinese barriers. Essentially, light barriers exist chen from a light source and a receiver, which in one Are spaced from each other. As a result, between the Light source and the receiver set up an optical barrier stressed. In principle, a light grid corresponds to a parallel one Arrangement of several light barriers, creating a two-dimensional le, extensive optical barrier is formed. On  big disadvantage of these arrangements is the required in usually quite complex adjustment, usually more Tools such as B. a laser pointer required. in addition comes that a multitude of active elements wire together must be carried out to ensure synchronization and correct evaluation to enable. To secure a larger and in terms its spatial extent are more complex danger areas complex photoelectric barrier systems are also required represent a significant cost factor. Another disadvantage of light barriers and light grids is their low flexibility action if the danger area to be secured is in terms of changes its size and / or shape. This is then, for example the case when several machines to be protected are common in one entire machine room can also be operated independently of one another can be taken.

In a laser scanner, a laser beam is rotated over a deflected mirror in a predetermined angular range, whereby a circular section-shaped area is monitored can. An object within this area can have a run time measurement methods are detected. With regard to the present The simple manipulability is such application like a strong dependence of the measurement on the reflection egg Properties of the objects to be measured are disadvantageous.

To avoid these disadvantages is mentioned in the introduction DE 196 44 278 A1 a monitoring device with an opti barrier described in which an artificial target in Shape of a pattern field at one end of a surveillance area and an image pickup unit at the other end of the over guard area are arranged. An evaluation device  checks whether the Ab image of the artificial target the expected, undisturbed image corresponds to the sample field.

When securing a more complex danger zone, the Installation effort and device costs with the help of this known arrangement can be reduced noticeably, because on one En de the optical barrier only the passive pattern field without Wiring must be arranged. With a spacious one stretched or complex shaped danger area, like him for example when securing production lines with Indu robot robots, but is still considerable effort required to place the sample field wherever it is needed to attach. In addition, such a Sample field currently in an industrial production area dirt and the risk of damage. Measures to address these issues, such as regular ones Cleaning and visual inspections are again complex.

DE 198 09 210 A1 describes a method and a device known for monitoring a scene. The monitored scene can be, for example, the operating room of a machine. at This procedure creates an image of the entire scene with a Image acquisition unit recorded. The captured image will compared with a stored reference image. The Ver immediately between a point of the reference image and a point the recorded image of the scene is made by an individual Dualization of light rays from a light source. example The individualization is done by staggered off shine individual rays of light that are to be compared Illuminate points or areas in the image of the scene.  

Since the entire scene, for example the entire operating room of the machine including moving objects, is always observed with this method, the image evaluation is comparatively complex despite the individualization. Accordingly, high demands are placed on the hardware 2 u for real-time processing, as is required to secure a danger zone. This in turn has a partial impact on the cost of a corresponding device.

Another system for optical surveillance of a room area is known from EP 0 902 402 A2. This one too The system becomes a currently recorded image of the room area compared in an evaluation unit with a reference image. On Fixed artificial target is in this known front direction is also not provided.

It is therefore an object of the present invention to provide a ver drive and to turn on a device of the type mentioned give a large fle when building an optical barrier flexibility with low cost and installation effort possible.

This task is achieved in the method mentioned at the outset solved that the artificial target a defined light signal which is generated by means of a light source.

The object is achieved in the device mentioned above solved that the device includes a light source, the a defined light signal to a position outside the Ge projected driving range, with the defined light signal the represents artificial target.  

The defined light signal can be a high-contrast pattern content, for example with an appropriate pattern disc is caused in the beam path of the light source. in the In the simplest case, the defined light signal is generated on a given background, however, a point or line Contour. In any case it is possible to use the defined light gnal and thus the artificial target for the image acquisition unit from one or possibly a few central points several defined positions outside the danger zone project. This eliminates the need for artificial Targets in the form of light strips, reflective foils or Apply paints at these defined positions. The Installation effort for the device according to the invention is therefore considerably reduced again. He also offers arrangement according to the invention a very great flexibility, since the artificial goals from the central point or points very much can be easily activated or deactivated. Also a Be damage or destruction or degradation due to Ver soiling is considerably reduced. This lowers the costs and increases the reliability in the operation of the fiction according device. Furthermore, the effort for the picture Evaluation very low because of the construction of the optical barrier only that which is exactly known and fixed in its structure artificial target must be observed. Accordingly easy and the hardware for the invention is inexpensive Contraption.

The above task is therefore completely solved.

In a preferred embodiment of the invention, the Light source the defined light signal at an angle to the  optical axis of the image recording unit. Preferably, the Angle in a range between 0 ° and 90 °, especially preferably in the range between 15 ° and 45 °.

This measure has the advantage that the so-called light section method can be used to evaluate the image taken. This method is explained in more detail with reference to the present invention with reference to FIGS. 2 and 3. A particular advantage of this method is that, in addition to the simple detection of an object in the area of the optical barrier, it is also possible to measure the distance to this object using triangulation. In addition, an object that breaks the optical barrier in this case often produces two different light effects, namely shading on the one hand and offset of the recorded light spot on the other hand. This results in redundancy which is advantageous with regard to the present application.

The preferred angular ranges are mainly for the light cutting process particularly cheap because it is a sufficient Change in the recorded image of the artificial target generate when the optical barrier through an object will break. They also allow image capture unit and the light source in spatially adjacent to each other Positions can be installed, which in turn takes the effort reduced during installation.

In a further preferred embodiment of the invention pro the light source jets the defined light signal onto you given background.  

This is not inevitable when using the light section method necessary. However, the measure has the advantage that the defined light signal always on the given background what is visible is an internal function check of the inventor device according to the invention. Add to that on this Way the redundancy already mentioned is generated which an Ob ject when breaking the optical barrier.

In a further preferred embodiment of the invention, he the light source generates the defined light signal over a large area expands.

With this measure, a two-dimensional optical cabinet ke created in the form of a light curtain very simply, whereby the risk of bypassing the optical barrier significantly re is induced. The generation of a corresponding light signal can be done, for example, with a laser diode whose light point by means of a cylindrical lens, a prism, a micro lens array or a rotating mirror is changed. Likewise, the light signal with an elongated Lumines zenzrrohr be generated, the light rays with the help of a Slit aperture are bundled. On a given background a linear light contour is created.

In a further preferred embodiment of the invention holds the defined light signal position marks for determination a current position of the artificial target.

Such position marks are preferably additional light points that are optically separated from the rest of the light signal be fathered. With the help of such position marks it is very  easily possible, an exact calibration of the invention Device. Such positions also serve ons brands to prevent tampering with the whole Arrangement, for example with the aim of bypassing the optical barrier. Finally, with the help of such position marks, a very simple vibration compensation possible, especially then It is advantageous if the device according to the invention for Ab secure a heavy machine, such as a hy draulic press, is used. Such a heavy ma Schine creates vibrations that are in the recorded Make the image of the artificial target noticeable as vibrations. The compensation of these vibrations enables avoidance of unnecessary false alarms.

In a further embodiment of the invention, the defi niert light signal pulsed.

This measure has the advantage that the average power of the defined light signal is considerably reduced where is possible by saving energy. In addition, you can with a suitable synchronization, extraneous light interference very much simply suppressed or at least reduced. Especially It is advantageous if this measure with a light source is combined in the infrared range, since in this case a ge suitable blocking filter extraneous light interference from the visible Be rich additionally suppressed.

In a further preferred embodiment, the image is on acquisition unit and the light source in a common device arranged house.  

This measure makes installation particularly easy of the device possible because only a compact device is mounted in this way and must be aligned. In addition, the Cabling effort considerably reduced again. The far ren the measure has the advantage that the image recording unit and the light source in a predetermined orientation are mounted to each other. This simplifies the installation ons effort again. In addition, the risk of unintentional Shifts or deliberate manipulations to the invention according device again considerably reduced.

In a further preferred embodiment of the invention at least the image acquisition unit with a downward incline arranged in the field of view.

In such an arrangement, the lens is the image unit is exposed to less pollution, which Reliability of the entire device is increased and at the same time tig reduced the maintenance effort.

In a further preferred embodiment, the image acquisition unit a line-shaped image sensor and an Ab probe unit.

As an alternative to this, the image sensor is in other configurations the invention extended areal. A line-shaped image sensor has the advantage of lower material costs because correspondingly fewer light-sensitive pixels are required are. In addition, there is a risk of errors and malfunction failures due to signal coupling between neighboring Pixels are reduced as there are significantly fewer neighboring ones overall  Pixels there. A is preferred as the scanning unit rotating mirror that uses the recorded image of the projected line by line onto the image sensor. It is particularly advantageous if this is the same mirror, which is also used to generate a light signal that extends over a large area serves, because in this case the material and construction effort is less.

In a further particularly preferred embodiment of the Er the evaluation unit is at least two-channel redundant built up.

This measure enables a particularly large fail-safe what with regard to the intended scope is of particular advantage.

In a further preferred embodiment of the aforementioned As a measure, the evaluation unit is diversified.

In a diversified structure, the two respective channels the evaluation unit with various components and / or built up according to different concepts, whereby the danger an undetected error is reduced again.

In a further preferred embodiment of the invention the two-channel image acquisition unit is also redundant.

It is particularly preferred, even if this two-channel opening construction is diverse. The measure has the advantage that Feh ler and functional failures in the image acquisition unit very can be recognized. In addition, this way too  short-term impairments, for example as a result of walking around flying insects, can be reliably detected, so that unnecessary false alarms are avoided.

It is understood that the above and the following standing features to be explained not only in each specified combination, but also in other combinations or can be used alone, without the scope of to leave the present invention.

Embodiments of the invention are in the drawing are shown and are described in more detail in the following description explained. Show it:

Fig. 1 is a schematic representation of a fiction, modern apparatus in a plan view,

Fig. 2 is an optical barrier according to the invention, which is pierced by two different objects,

FIGS. 3a-d show various images of the artificial target in the arrangement of Fig. 2,

Fig. 4 shows a preferred embodiment of a device OF INVENTION to the invention,

Fig. 5 is a block diagram of the device according to Fig. 4,

Fig. 6 shows a preferred application of the device according to the invention, and

Fig. 7 shows a defined light signal with position marks.

In Fig. 1, a device according to the invention is designated in its entirety with the reference number 10 .

The device 10 includes an image recording unit 12 and a light source 14 . The light source 14 generates a defined light signal 16 and, in conjunction with the image recording unit 12, forms an optical barrier 18 for securing a driving area 20 of an automated machine 22 . In the present exemplary embodiment, the machine 22 is an industrial robot that can move independently in the direction of the arrow 24 .

The image acquisition unit 12 is arranged with its optical axis 26 at an angle θ to the defined light signal 16 . In addition, the image recording unit 12 and the light source 14 are at a defined distance D from each other, whereby an approximately rectangular triangle is formed. This makes it possible, using triangulation methods known per se, to determine the distance of the image recording unit 12 from an object which breaks through the optical barrier 18 .

With the reference numeral 28 , a given background is designated, in the present case, for example, a wall onto which the defined light signal 16 is projected. The light signal 16 is extended perpendicularly to the view plane and thus forms a linear contour (not shown here) on the background 28 .

Reference number 30 denotes an evaluation and control unit which is connected on the one hand to the image recording unit 12 and on the other hand to the machine 22 . If an object (not shown here) breaks through the optical barrier 18 , this is recorded by the image recording unit 12 , the field of vision of which is designated here by the reference number 32 . By comparison with a reference image, which corresponds to an undisturbed image of the defined light signal (artificial target), the evaluation and control unit 30 can recognize this process and switch off the machine 22 or otherwise put it in a safe state.

In the following description of the further figures, the same reference numerals designate the same elements as in FIG. 1.

In FIG. 2, two different situations are shown, in which an object breaks the optical barrier. In the undisturbed state, the defined light signal 16 from the light source 14 reaches the given background 28 and generates a light contour 34 thereon. If an object 36 now breaks through one or more light beams from the light source 14 , a second light contour 40 is created on the surface 38 of the object 36 . At the same time, depending on the size of the object 36, all or at least part of the original light contour 34 disappears on the background 28 . From the point of view of the image recording unit 12 , shadowing therefore arises on the one hand and on the other hand part of the light contour 34 is moved to another location in the room.

This is illustrated again by means of the representations in FIG. 3. Fig. 3a shows the image of the unperturbed light contour 34, which has in this case a linear expansion. FIG. 3d, on the other hand, shows the image that is recorded by the image recording unit 12 when the object 36 interrupts the defined light signal 16 . As can be seen, the light contour 34 is partially shaded on the background 28 . At the same time, the new light contour 40 becomes visible at another point in the room. By comparison with the undisturbed image of the light contour 34 , which in this respect represents a reference image, the evaluation and control unit 30 can recognize the intrusion of the object 36 into the danger zone and react accordingly.

With the aid of the triangulation methods already mentioned, the evaluation and control unit 30 can further determine the position of the light contour 40 and thus the spatial position of the object 36 .

FIG. 3b shows the image of the defined light signal 16 in the case that the light is completely covered contour 34 on the fundus 28. This is the case when the light signal 16 is completely covered. A breakthrough of the light barrier or a security gap arising as a result of shading can thus also be reliably detected.

In Fig. 3c, the light contour 34 is shaded Darge without another light contour 40 is recognizable. Such a situation arises when an object 42 ( FIG. 2) breaks through the light signal 16 without the image recording unit 12 being able to take up the newly formed light contour 40 . In this case, too, the breaking of the optical barrier can be recognized by the shading in the light contour 34 .

In Fig. 4, another embodiment of the device according to the Invention is designated in its entirety with the reference number 50 . In this embodiment, the image recording unit 12 and the light source 14 are arranged in a common Ge device housing 52 . The image recording unit 12 and the light source 14 are accordingly mounted at a fixed distance D and at a fixed angle θ from one another. The image recording unit 12 detects the light contour (not visible here), which generates the defined light signal 16 on the background 28 given . The defined light signal 16 thus represents the artificial target, through the observation of which the optical barrier 18 is spanned.

The penetration of an object into the field of view 32 of the image recording unit 12 is harmless as long as the defi ned light signal 16 and the corresponding light contour on the background 28 are not disturbed. As a result, the evaluation of the recorded images can be limited to the spatially fixed artificial target, as a result of which the image processing expenditure is kept very low.

The functional structure of the device 50 can be seen in the block diagram according to FIG. 5. The image recording unit 12 includes a lens 54 which projects a recorded image onto an image sensor 56 . In a preferred embodiment of the invention, the image sensor 56 is line-shaped, so that each light-sensitive pixel has a maximum of two adjacent pixels. In this case, the risk of errors and malfunctions due to crosstalk (signal coupling) is significantly reduced. In other preferred exemplary embodiments, the image sensor, in contrast, is a two-dimensionally extended, flat image sensor, which enables larger images to be taken. The image sensor 56 is preferably a CMOS sensor, but it can also be constructed using CCD technology. In this preferred embodiment, the image of the artificial target is projected line by line onto the image sensor 56 with the aid of a rotating mirror (not shown here).

Reference numeral 58 denotes a sensor control that reads the image data from the image sensor 56 and also transmits suitable control signals to the latter. The sensor control 58 stores the read image data in two image memories 60 a, 60 b. A reference image 62 , which corresponds to an undisturbed image of the artificial target, is also stored in each of the two image memories 60 a, 60 b. Instead of a complete reference image, only characteristic values of the reference image are preferably stored.

The reference numerals 64 a, 64 b denote two processors which transmit control commands to the sensor control 58 . Furthermore, the processors 64 a, 64 b carry out the comparison of the recorded images of the artificial target with the stored reference images 62 . Overall, this results in a two-channel structure of the evaluation unit integrated here, one of the first channels being designated by the reference number 66 and the second channel being designated by the reference number 68 .

In the present, preferred exemplary embodiment, the two channels 66 , 68 are constructed with components from different manufacturers, that is to say diversely. The processors 64 a, 64 b of the channels 66 , 68 can communicate via a communication channel 70 , for example in the form of a so-called dual-ported RAM. Mutual monitoring and functional control is possible here.

The reference numeral 72 denotes a data interface via which the device 50 can be connected to a commercially available PC for configuration and diagnosis purposes. The reference numeral 74 designates fail-safe outputs via which an alarm signal and / or switching signals are generated when an object breaks the optical barrier. The same applies in the event that an internal device error is recognized on the basis of an internal self-test or the mutual function check of the two channels 66 , 68 . The fault safety of the outputs is preferably achieved by a redundant design.

Reference number 76 denotes a bus interface via which the device 50 can be connected to a safe bus system, for example the so-called "SafetyBus p" from the applicant of the present invention. Such a fail-safe bus interface can be used to transmit configuration and / or diagnostic data as well as switching and alarm signals.

A lighting control for the light source 14 is designated by the reference number 78 . The light source 14 is thus pulsed here, the lighting control 78 being synchronized with the image recording unit 12 via the processor 64 b.

In the embodiment shown in Fig. 6 is a fiction, modern device is blocking in combination with a mechanical From 90 shown. The mechanical barrier 90 is, for example, a protective fence, which is arranged around an industrial robot. In the barrier 90 , an access 92 is left open, through which the danger area to be secured can be entered in the direction of the arrow 94 . With the aid of the light source 14 , a linear light contour 96 is projected onto the floor and the lateral boundary of the access 92 and is optically monitored with the image recording unit 12 . If someone steps through the access 92 , the light contour 96 is interrupted in the manner described in FIGS. 2 and 3, which can be determined by the associated evaluation unit.

A special feature of this exemplary embodiment is that the field of view 98 of the image recording unit 12 is directed essentially downward, as a result of which deposits and dirt on the lens 54 of the image recording unit 12 are reduced. In addition, this exemplary embodiment shows that even large-area optical barriers can be monitored seamlessly from a central location with a device according to the invention.

Fig. 7 shows a linear light contour 34 , which is supplemented by additional light spots 102 . The light spots 102 can be recognized as individual in the recorded image of the contour 34 and can thus be used as position marks for the exact determination of the position of the artificial target. In addition, these position marks make it possible to compensate for vibrations due to machine movements.

In further exemplary embodiments of the invention, not shown here, there are further additional light spots 102 , the sequence of which forms an individual identification code. This allows the individual optical barriers and their respective current position to be identified exactly, which prevents manipulation, such as the displacement or removal of existing protective grids.

In the previously described embodiments of the invention, the light-cutting method was used to monitor the optical barrier. Deviating or supplementing this, however, an arrangement according to FIG. 1 can also depict a high-contrast pattern field on the given background 28 . The image can then be evaluated, for example, using the method of DE 196 44 278 A1.

Furthermore, measures can be taken in all exemplary embodiments be provided to compensate for contamination. In one In the simplest case, this means that the respective reference image Newly recorded at predetermined intervals which implicitly compensates for creeping pollution is settled.

Claims (20)

1. A method for securing a danger zone ( 20 ), in particular the danger zone of an automatically working machine ( 22 ), an optical barrier ( 18 ) being generated in front of the danger zone ( 20 ), with the steps:

• - Placing an artificial target ( 16 ) at a defined position outside the danger zone ( 20 ),
• Recording an image of the artificial target ( 16 ) with an image recording unit ( 12 ),
• Comparing the recorded image with characteristic values of a reference image ( 62 ), the reference image ( 62 ) corresponding to an undisturbed image of the artificial target ( 16 ),

characterized in that the artificial target ( 16 ) is a defined light signal which is generated by means of a light source ( 14 ). 2. The method according to claim 1, characterized in that the defined light signal ( 16 ) at an angle ( 8 ) to the op table axis ( 26 ) of the image recording unit ( 12 ) is generated. 3. The method according to claim 1, characterized in that the Angle (θ) in a range between 0 ° and 90 °, preferred is selected in the range between 15 ° and 45 °. 4. The method according to any one of claims 1 to 3, characterized in that the defined light signal ( 16 ) is projected onto a given background ( 28 ). 5. The method according to any one of claims 1 to 4, characterized in that the defined light signal ( 16 ) is generated extensively. 6. The method according to any one of claims 1 to 5, characterized in that the defined light signal ( 16 ) includes position marks ( 102 ) for determining a current position of the artificial target. 7. The method according to any one of claims 1 to 6, characterized in that the defined light signal ( 16 ) is pulsed. 8. Device for securing a danger zone ( 20 ), in particular the danger zone of an automated ar machine ( 22 ), with an image recording unit ( 12 ) and with an artificial target ( 16 ), which is in a defined position outside the danger zone ( 20 ) is also arranged with an evaluation unit ( 30 ) which compares a recorded image of the artificial target ( 16 ) with characteristic values of a reference image ( 62 ), the reference image ( 62 ) corresponding to an undisturbed image of the artificial target ( 16 ) , characterized in that the device ( 10 ) includes a light source ( 14 ) which projects a defined light signal to a position outside the danger zone ( 20 ), the defined light signal representing the artificial target ( 16 ). 9. The device according to claim 8, characterized in that the light source ( 14 ) emits the defined light signal ( 16 ) at an angle (A) to the optical axis ( 26 ) of the image recording unit ( 12 ). 10. The device according to claim 9, characterized in that the angle (θ) in a range between 0 ° and 90 °, be preferably in the range between 15 ° and 45 °. 11. Device according to one of claims 8 to 10, characterized in that the light source ( 14 ) projects the defined light signal ( 16 ) on a given background ( 28 ) pro. 12. Device according to one of claims 8 to 11, characterized in that the light source ( 14 ) generates the defined light signal ( 16 ) extended over a large area. 13. Device according to one of claims 8 to 12, characterized in that the defined light signal ( 16 ) includes position marks ( 102 ) for determining a current position of the artificial target. 14. Device according to one of claims 8 to 13, characterized in that the defined light signal ( 16 ) is pulsed. 15. Device according to one of claims 8 to 14, characterized in that the image recording unit ( 12 ) and the light source ( 14 ) are arranged in a common device housing ( 52 ). 16. Device according to one of claims 8 to 15, characterized in that at least the image recording unit ( 12 ) is arranged with a downwardly inclined field of view ( 98 ). 17. The device according to one of claims 8 to 16, characterized in that the image recording unit ( 12 ) has a zei len shaped image sensor ( 56 ) and a scanning unit. 18. Device according to one of claims 8 to 17, characterized in that the evaluation unit ( 30 ) is constructed redundantly at least two channels ( 66 , 68 ). 19. The apparatus according to claim 18, characterized in that the evaluation unit ( 30 ) is diversified. 20. Device according to one of claims 8 to 19, characterized ge indicates that the image recording unit right two channels is built redundantly.