DE202010005042U1 - Optoelectronic device - Google Patents

Abstract

Optoelectronic device for monitoring a passage (46), which has at least one distance-measuring sensor (10a-b) with which presence and contour information of objects (48) can be generated in the passage (46), wherein an evaluation unit (30, 38) designed for outputting a safe switch-off signal in the passage (46) when an object (48) is present and exceptionally permitting the presence of permissible objects (48) with expected contour properties without outputting the switch-off signal, characterized in that the evaluation unit (30, 38 ) is adapted to detect permissible objects (48) on the basis of their symmetry to a central axis (50).

Description

The invention relates to an optoelectronic device for monitoring a passage according to the preamble of claim 1.

In industrial production processes, it is often necessary to automatically convey the objects to be processed, for example a vehicle body, from a danger-free area into a dangerous area. During the further processing steps in the dangerous area then the access of persons must be reliably prevented. For this purpose, optoelectronic sensors such as safety light barriers or safety light grids can be used. The further processing is interrupted immediately to prevent accidents when a person enters the entrance or exit area. Also known is the protection by mechanical means, such as Schneillauftore or pendulum flaps

In addition to the aforementioned simple sensors and security laser scanner, such as in the DE 43 40 756 A1 described. In this case, a light beam generated by a laser periodically sweeps over a monitoring area with the aid of a deflection unit. The light is remitted to objects in the surveillance area and evaluated in the scanner. From the angular position of the deflection unit is additionally closed on the angular position of the object from the light transit time using the speed of light on the distance of the object from the laser scanner. The angle and distance information can be used to determine the location of an object in the surveillance area as well as the contour of the object. There are two basic principles known to determine the light transit time. In phase-based methods, the transmitted light is modulated and the phase shift of the received light compared to the transmitted light is evaluated. With pulse-based methods, as they are preferably used in safety technology, the laser scanner measures the transit time until an emitted light pulse is received again.

Sensors used in safety technology must work particularly reliably and therefore meet high safety requirements, such as the standard EN13849 for machine safety and the device standard EN61496 for non-contact protective devices (ESPE). To meet these safety standards, a number of measures must be taken, such as safe electronic evaluation by redundant, diverse electronics, function monitoring or specially monitoring the contamination of optical components, in particular a windscreen, and / or providing individual test objectives with defined degrees of reflection, among the corresponding scan angles must be detected.

In the case of the above-mentioned protection of a passage into a hazardous area with optoelectronic sensors, it must be ensured that the objects to be machined can reach and leave the working area without triggering a safety-related emergency stop. For this purpose, it is known to temporarily deactivate the sensors (muting). However, this requires additional sensors to detect when the safety sensor must be mute or a signal from the transport system. This entails a correspondingly high outlay for the configuration, wiring and commissioning of the muting station. In addition, it is often relatively easy to enter the dangerous area with the object undetected.

From the EP 44 11 448 B4 For example, a laser scanner for controlling a predetermined monitoring area is known, which determines a distance contour of objects located in the monitoring area. This distance contour is compared with a stored reference contour corresponding to an expected object within the monitoring area. A warning or a shutdown signal is output only if the distance contour deviates from the reference contour.

The DE 10 2004 044 973 A1 discloses a control of a surveillance area on a conveyor. In object points generated by a laser scanner, a contour search is performed to determine if a given model line of an object allowed in the surveillance area can be detected. If this does not succeed, then this is evaluated as a security-relevant object intervention and issued a shutdown signal.

A disadvantage of the conventional laser scanners is that in advance contours of permissible objects must be taught and thus creates a configuration effort. In addition, the comparison between taught-in and measured object contour is relatively complex even during operation and requires appropriate computing power. In addition, it is very difficult to perform the contour comparison robust enough so that unnecessary shutdowns are avoided and yet the safety is guaranteed.

It is therefore an object of the invention to provide a hedge that allows a simple and robust distinction between an allowable object and a dangerous intervention.

This object is achieved by an optoelectronic sensor for monitoring a passage according to claim 1. The invention goes from the idea of recognizing allowable objects from previously known simple properties that distinguish them from a person. For this, the symmetry to a central axis is used.

The invention has the advantage that the configuration, assembly and wiring of the device is very simple and therefore requires only minimal effort. Additional sensors, such as muting sensors, can be dispensed with, thus saving on industrial space. The method is much safer than conventional solutions and recognizes in a simple but robust way the intrusion of a person when it is together with the object in the passage or moves into the arranged behind the passage secured area.

There are no special requirements to be placed on the object, for example, on its geometry or surface texture. A robust evaluation is also possible on less measurable surfaces, for example black and / or shiny surfaces. The object may at any time and indefinitely stay in the passage and move at any speed. The only requirement for the object is that in the tolerance limits to be explained, a symmetry to a central axis exists.

The device preferably has two distance-measuring sensors with which contour information of a right or left portion of an object with respect to the central axis can be generated in the passage. Thus, the two contour areas to be compared with respect to their symmetry are recorded from a favorable viewing angle. As a result, shadowing is avoided and measured data from partially reflecting or poorly measurable surfaces are recorded particularly well. Alternatively, it is also conceivable to use only one sensor, especially if it has a corresponding field of view. For example, a momentary light grid is suitable for this purpose, that is to say a light grid which is constructed of light sensors instead of light barriers and in particular of distance-measuring light sensors.

The device preferably has a safety control, which is connected to the sensors, wherein in particular the safety control comprises the evaluation unit. It is thus possible to accommodate the computing capacity for the evaluation centrally in the safety control instead of in the individual sensors. After the registration, ie agreement on a common coordinate system, the sensors become practically a single sensor with an extended field of vision or improved viewing angle via the safety control.

The sensors are preferably mounted vertically on the passage in such a way that a passage plane perpendicular to a passage direction can be monitored and thus contour information of an object moved through the passage can be generated in vertical sections. In such a access protection with two vertically mounted sensors, especially laser scanners, a good view is ensured, and at the same time the sensors interfere with the flow in any way, as they are mounted above.

The contour information is preferably outputable to allow three-dimensional visualization of the objects in the passage on a display. In the passage, the entire three-dimensional outer contour is determined piecemeal with progressive movement of the object. In a sensor with level monitoring, such as a laser scanner, successive vertical sections of the object, which can be assembled to form a 3D image of the sensor data. This can be diagnosed, for example, in the case of a safety-related shutdown, which intervention has led to the emergency stop and whether, for example, a person or a faulty circuit was the cause.

The evaluation unit is preferably designed to detect the symmetry of a permissible object on the basis of its maximum extent to the right and left with respect to the central axis. This does not mean that the entire right and left partial contour has to be compared and that no suitable comparison measure can be found. The maximum extent is a very easy to evaluate and at the same time robust symmetry measure.

The evaluation unit is preferably designed to recognize an object as symmetrical only if the symmetry from the contour is recognized by the passage except for a tolerance in each movement stage. Thus, during the entire movement through the passage, a symmetry monitoring takes place in order to completely recognize persons or other impermissible interventions.

In this case, the evaluation unit is particularly preferably designed to accept a tolerance as a temporary deviation from the symmetry, provided that the deviation in a shortly following movement stage on the opposite side with respect to the central axis retraced and so the symmetry is restored. This would be the case, for example, with a slightly inclined object. But if the deviation from the symmetry is not reconstructed on the opposite side, then it is a genuine break in symmetry and thus an impermissible intervention.

The evaluation unit is preferably designed to accept an object as permissible even with slight deviations from the symmetry, wherein the minor deviations are in particular smaller than a human body or a body part and to allow an object in particular if it has a small vertical extent. The symmetry requirement need not be stricter than the smallest interference to be detected. Of course, a deviation is measured from the perspective of the sensors, often in the projection from above. Exemplary dimensions for a still admissible symmetry deviation are 70 mm for the detection of a leg or 150 mm for the detection of a body, whereby a safety reserve is already provided in these dimensions. On the other hand, if the sensors are mounted at an angle, the vertical extent of a detected asymmetry can also be measured. This vertical extent is a good distinguishing criterion between non-critical object components and a human body.

The evaluation unit is preferably designed to calculate from the contour properties an area of an object present in the passage, in particular by estimation by means of a circumscribed rectangle. The surface is a simple additional geometric measure for evaluating an object in the passage. Instead of a rewritten rectangle (Bounding box) other simple geometric shapes are considered equivalent, such as a perimeter, a triangle or the like.

The evaluation unit is particularly preferably configured to accept an object as permissible only if the area of the object monotonously increases on entry into the passage and / or monotonically decreases on exit from the passage. This distinguishes whether a person tries to penetrate in front of or behind the object and is fused to the object from the perspective of the sensors.

The passage is preferably arranged on a spar-guided transport system, wherein in particular the switch-off signal can be output to a holding device of the transport system. A spar-led transport system ensures that no transverse movements or rotations disturb the symmetry to the central axis. In addition to stopping the transport system, additional safeguards may be required, such as stopping a robot movement in the hazardous area behind the passageway.

The sensors are preferably designed as laser scanners and each have a light emitter for emitting a light beam in the passage, a light receiver for generating a received signal from the remitted by objects in the passage of light beam and a movable deflection unit for periodic sampling of the passage. Laser scanners are particularly suitable for securing a plane, as it forms the passage, and at the same time provide the necessary measuring points for assessing the symmetry. In principle, other distance-measuring sensors are conceivable, for example, a light-time camera or a stereo camera, but these sensors are usually much more complex and then have so much computing power that they could also perform much more complex contour recognition as a symmetry detection.

The permissible objects are preferably vehicles. Vehicles are industrially processed in large numbers, so that an important field of application exists here. In most cases, spared transport systems are used anyway. In addition, a vehicle has the required symmetry in almost every production step.

The invention will be explained in more detail below with regard to further features and advantages by way of example with reference to embodiments and with reference to the accompanying drawings. The illustrations of the drawing show in:

1 a schematic sectional view through a laser scanner according to the invention;

2 a block diagram of the connections of two sensors with a safety controller and a transport system;

3 a schematic three-dimensional representation of the vertical mounting of two laser scanner at a passage in the vehicle assembly;

4 an exemplary reconstruction of the three-dimensional vehicle contour and an inadmissibly engaging in the passage person;

5 a front view of the reconstruction according to 4 ; and

6 an exemplary measuring point cloud, as they are recorded by the sensors in a measuring cycle.

1 shows a schematic sectional view through a security scanner according to the invention 10 , One from a light transmitter 12 , For example, a laser, generated light beam 14 , of the has individual light pulses is via light deflecting units 16a -B in a surveillance area 18 steered and there remitted from any existing object. The remitted light 20 returns to the security scanner 10 back and will be there via the deflection unit 16b and by means of a receiving optics 22 from a light receiver 24 detected, for example, a photodiode.

The light deflection unit 16b is usually designed as a rotating mirror, by driving a motor 26 continuously rotated. The respective angular position of the light deflection unit 16b is via an encoder 28 detected. The one from the light transmitter 12 generated light beam 14 thus sweeps over the monitoring area generated by the rotational movement 18 , Becomes one of the light receiver 24 received reflected light signal 20 from the surveillance area 18 received, so can from the angular position of the deflection 16b by means of the encoder 28 on the angular position of the object in the surveillance area 18 getting closed

In addition, the transit time of the individual laser light pulses from their emission to the reception after reflection on the object in the surveillance area 18 determined. From the light transit time, using the speed of light, the distance to the object from the security scanner 10 closed. This evaluation takes place in an evaluation unit 30 for that with the light transmitter 12 , the light receiver 24 , the engine 26 and the encoder 28 connected is. Thus, two-dimensional polar coordinates of all objects in the surveillance area are available over the angle and the distance 18 as well as theirs to the security scanner 10 directed contours available. This information about presence and contour of objects is via an interface 32 dispensable.

All mentioned functional components are in one housing 34 arranged, the front side, so in the area of Lichtaus- and light entry, a windscreen 36 having. The windscreen 36 is to avoid direct reflections in the light receiver 24 tilted so that light beam 14 and windscreen 36 enclose an angle other than ninety degrees.

According to the invention, a security scanner 10 used as an example of a distance-measuring sensor on a passage to protect against entering or leaving persons. In a simple embodiment, this is a single security scanner 10 mounted centrally above the passage. In many cases, however, due to shadowing and unfavorable measuring angles, an object is not detected reliably enough, depending on the contour and surface condition.

2 shows an embodiment in which two security scanners 10a -B by means of a safety control 38 be combined with each other. Here, and in the following, the same reference numerals are used for identical or corresponding features. The security scanner 10a -B are, as usual in safety technology, two-channel to the safety control 38 connected. In the illustrated preferred embodiment, the safety controller consists of a control head module 40 and one or more connection modules 42a -C, which respectively. Has inputs for sensors and / or outputs for actuators. A connected actuator shown here by way of example is a transport system 44 ,

The security scanner 10a For example, -b are mounted to the left and right of the passage with a vertical monitoring plane. Based on the scanner data, it is determined if an object is in the passage. If so, the contour of the object is evaluated to determine if the object should be allowed in the passage. Otherwise, a safety-related shutdown signal is sent to the transport system 44 and optionally issued further system components. The decision as to whether an object is admissible is made on the basis of symmetry properties and related below 6 explained in more detail. This evaluation can be done in the evaluation units 30 the security scanner 10a -B, in the control head module 40 , in a connection module 40c the safety control 38 or in distributed or parallel evaluation between these components.

3 shows in a three-dimensional view a passage 46 by two security scanners 10a -B with their monitoring levels 18a -B is secured. In this case, as permitted objects vehicle bodies 48a -B on a track-guided transport system 44 promoted. The monitoring levels 10a -B are orthogonal to the conveying direction of the transport system 44 , Based on the measurement data of the security scanner 10a -B becomes, as to the block diagram of 2 Explained, made a decision, if only a vehicle body 48a in the passage 46 located. This is a permissible interference with the monitoring levels 18a b. Any other intervention is considered inadmissible and leads to a safety-related shutdown.

In every stage of movement, so with progressive promotion of vehicle bodies 48a -B through the transport system 44 , take the security scanner 10a -B is a vertical section of the outer contour of the passage in the 46 located vehicle body 48a -B on. The measurement data of these vertical sections can be online or after caching, be passed offline to a diagnostic system, such as an external computer, and assembled there into a three-dimensional view,

An example of this three-dimensional view shows the 4 , One person is recognizable in the left picture area. If this image is viewed after an emergency stop, it is immediately clear that the safety-related shutdown was justified and not based on a misconfiguration. 5 shows for comparison a corresponding front view, ie a change in the perspective of the three-dimensional view.

For symmetry detection is a central axis 50 certainly. Either all have in the passage 46 conceivable vehicles 48 a common symmetry center, which usually applies even partially assembled. Then it is sufficient, in advance, the central axis 50 pretend to be about the middle of the transport system 44 , Alternatively, a central axis 50 be taught automatically by initially presenting a vehicle.

The evaluation sets in the monitoring level 18 an upper limit 52 as well as a left and right border 54a -B the vehicle body 48 firmly. 6 shows for clarity the vertical section in the monitoring plane 18 of the 4 as an example cloud of measurements, like the security scanner 10a -B in one measurement cycle, including the symmetry axis 50 and the limits 52 . 54a b. Here are the measurement data of the two security scanners 10a -B are combined in a common coordinate system. This requires an initial registration, but limited to a few parameters, when mounted together in a plane with vertical alignment already satisfies a single distance parameter. Also this distance can be the security scanner 10a -B learn automatically in free field of view.

Determination of the left boundary 54a is preferably done with the measurement data of the left security scanner 10a , and accordingly the determination of the right border 54b with the measured data of the right safety laser scanner 10b , In this way, problems with partially reflective or poorly measurable surfaces are avoided. The upper limit 52 is taken from the data of any security scanner 10a -B or the combined data of both security scanners 10a -B determined.

A very simple criterion for the limits 52 . 54a -B is an extremal view, ie the point furthest in the direction considered determines the boundary 52 . 54a -B according to functions such as min (x), min (y), max (x) or max (y). Alternatively, more complicated dimensions are conceivable, such as an averaging over some or all measuring points on the edge in question. It is also possible not just a single scalar to describe the location of the border 52 . 54a -B to use, but to incorporate the contour as such.

The request for allowed objects 48 is that the symmetry between the left boundary 54a and the right border 54b during the movement of the object 48 through the passage 46 must be respected. Due to tolerances, for example in the orientation of the object 48 , in some situations, an asymmetry may temporarily occur and, for example, the object 48 in the vertical section initially only at the left border 54a expand. The temporary asymmetry is accepted and the object 48 remains permissible, provided that the object continues to move 48 through the passage 48 the symmetry on the opposite border 54b is restored within a tolerance.

For example, the situation is different when a person is at the left side of the object 48 passes. Then the left border falls 54a after passing back to the object line, without being on the right border 54b a corresponding widening was registered. This situation is inadmissible and leads to a safety-related shutdown signal. The requirement for a temporary asymmetry is therefore that the respective opposite limit 54a -B the corresponding widening or constriction within a tolerance must symmetrically understand (monotone chaining). The tolerance is chosen so that dangerous situations such as the passage of a person are still reliably prevented.

Such apparent asymmetries, such as those caused by tolerances in the orientation or measurement, are real asymmetries of the object 48 to distinguish. Basically, the object must be for the recognition according to the invention 48 be symmetrical. But smaller asymmetries are allowed, as long as they still remain distinguishable from impermissible interference by persons. One such special case of allowable asymmetry is a one-sided extent, such as an exterior mirror of a vehicle. On the one hand tolerances in the symmetry are allowed, which can not be caused by a human body.

Even more preferred are the security scanners 10a -B arranged so that they measure the height extent. This is for example in the representations of 3 and 4 with surveillance levels spanned from the upper right and upper left corners, respectively. A one-sided asymmetry with only small height expansion is considered uncritical because it can not be caused by any human body. However, if the height extent exceeds a tolerance, then either the asymmetry per se must be negligibly small, or, as described above, a restoration of the symmetry will follow in a subsequent stage of movement. Otherwise, the safety-related shutdown signal is output.

A person can pass not only laterally but also before or after the object 48 try to cross. As long as there is a minimal gap between the object 48 and the person exists, for example at least one pair of free measured data, two different objects are detected. Objects are not allowed to follow each other so densely, furthermore the person is too small and not symmetrical. These are some geometric and temporal example criteria according to which the isolable person leads to a shutdown.

But the person should put a hand on the object 48 place or the like, so are person and object 48 metrologically connected. To handle this situation, the area of the object becomes 48 within the vertical cut in the passage 46 certainly. The area can be easily estimated by upper limit 52 , left border 54a and right border 54b with the lower protective field boundary, for example at or above the height of the transport system 44 , to be understood as a circumscribed rectangle. More complicated surface calculations by other circumscribing shapes or an area estimation at the level of the measuring points by cutting the scan lines are conceivable, but generally not necessary.

The area thus determined must be during the movement of the object 48 in the passage 46 grow monotonously. Fluctuations above a selected tolerance lead to the switch-off signal. Such a critical fluctuation occurs, for example, when the detected boundaries between person and object 48 close at short notice. The same thing happens when the object exits 48 demanded that the area decrease monotonically, especially after the distance between the left boundary 54a and right border 54b once it has fallen below a certain width.

A person on the object 48 or a person, for example, in a vehicle is only recognizable if the object surface very good optical properties for the recording of measurement data with the security scanners 10a -B shows. In this case, further contour properties must be evaluated as the left and right boundaries unchanged in this situation 54a b.

Safety Laser Scanner 10a In addition, b enable two-dimensional muting, in the case of small two-dimensional regions, for example, by the transport unit (skid) of the transport system 44 are passed through, the rest of the protective field remains free. Among other things, this enables an automatic initiation of a check with fixed protective fields for special cases, for example if only one door instead of one vehicle is used as object 48 on the transport system 44 is encouraged.

With two-dimensional muting, the actual protective field evaluation can be set to the technically smallest possible response times, as long as no vehicle passes through 46 shall pass through. This is much safer than the conventional light grid solutions, with which such a two-dimensional muting is not feasible.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4340756 A1 [0003]
• EP 4411448 B4 [0006]
• DE 102004044973 A1 [0007]

Cited non-patent literature

• EN13849 [0004]
• EN61496 [0004]

Claims (14)

Opto-electronic device for monitoring a passage ( 46 ) comprising at least one distance-measuring sensor ( 10a -B), with the presence and contour information of objects ( 48 ) in the passage ( 46 ) can be generated, wherein an evaluation unit ( 30 . 38 ) is designed to, in the presence of an object ( 48 ) in the passage ( 46 ) output a safe switch-off signal and, exceptionally, the presence of permissible objects ( 48 ) with expected contour properties without outputting the switch-off signal, characterized in that the evaluation unit ( 30 . 38 ) is designed for permissible objects ( 48 ) on the basis of their symmetry to a central axis ( 50 ) to recognize. Device according to claim 1, comprising two distance-measuring sensors ( 10a -B), with each of which contour information of one with respect to the central axis ( 50 ) right or left portion of an object ( 48 ) in the passage ( 46 ) are producible. Device according to claim 1 or 2, comprising a safety control ( 38 ) connected to the sensors ( 10a -B), in particular the safety controller ( 38 ) comprises the evaluation unit. Device according to one of the preceding claims, wherein the sensors ( 10a B) so vertically at the passage ( 46 ) are mounted, that a passage plane perpendicular to a passage direction can be monitored and thus contour information of a through the passage ( 46 ) moving object ( 48 ) can be generated in vertical sections. Device according to one of the preceding claims, wherein the contour information can be output to a three-dimensional visualization of the objects ( 48 ) in the passage ( 46 ) on a display. Device according to one of the preceding claims, wherein the evaluation unit ( 30 . 38 ) is adapted to the symmetry of a permissible object ( 48 ) based on its maximum extent to the right and left with respect to the central axis ( 50 ) to recognize. Device according to one of the preceding claims, wherein the evaluation unit ( 30 . 38 ) is designed to be an object ( 48 ) to be seen symmetrically only if the symmetry from the contour to the tolerance at each stage of movement through the passage ( 46 ) is recognized. Apparatus according to claim 7, wherein the evaluation unit ( 30 . 38 ) is designed to accept as tolerance a transient deviation from the symmetry, provided that the deviation in a shortly following movement stage on the opposite side with respect to the central axis ( 50 ) and so the symmetry is restored. Device according to one of the preceding claims, wherein the evaluation unit ( 30 . 38 ) is designed to be an object ( 48 ) to accept as permissible even with slight deviations from the symmetry, the minor deviations being in particular smaller than a human body or a body part, and an object ( 48 ), in particular if it has a small vertical extent. Device according to one of the preceding claims, wherein the evaluation unit ( 30 . 38 ) is designed to transform the contour properties into an area of a passage ( 46 ) present object ( 48 ), in particular by estimation by means of a circumscribed rectangle. Apparatus according to claim 10, wherein the evaluation unit ( 30 . 38 ) is designed to be an object ( 48 ) only accept as permissible if the area of the objects ( 48 ) when entering the passage ( 46 ) increases monotonically and / or on exit from the passage ( 46 ) decreases monotonically. Device according to one of the preceding claims, wherein the passage ( 46 ) on a track-guided transport system ( 44 ) and wherein in particular the switch-off signal to a holding device of the transport system ( 44 ) is dispensable. Device according to one of the preceding claims, wherein the sensors are used as laser scanners ( 10 ) are formed and each have a light transmitter ( 12 ) for emitting a light beam ( 14 ) in the passage ( 18 . 46 ), a light receiver ( 24 ) for generating a received signal from that of objects ( 48 ) in the passage ( 18 . 46 ) remitted light beam ( 20 ) and a movable deflection unit ( 16b ) for the periodic sampling of the passage ( 18 . 46 ) exhibit. Device according to one of the preceding claims, wherein the permissible objects ( 48 ) Are vehicles.

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