Monitoring device

Abstract

Monitoring device (100) with sensor means by means of which a protective field monitoring is carried out, wherein a safety function is triggered depending on sensor signals of the sensor means, characterized in that two protective fields (9) are monitored with the sensor means, which are arranged opposite each other at a distance from each other, wherein the maximum distance between the protective fields (9) is less than or equal to the size of a smallest detectable object (O) and that the safety function is only triggered if an object (O) is registered in both protective fields (9) simultaneously.

Description

[0001] The invention relates to a monitoring device.

[0002] Such monitoring devices are used in particular for monitoring hazardous areas at hazardous facilities. A hazardous area at such a facility is monitored with an optical sensor, which is generally designed as a scanning sensor such that the light beams of a transmitter / receiver unit of this optical sensor periodically scan a monitoring area, in particular the hazardous area. Specifically, the optical sensor can be designed as an area distance sensor, i.e., a scanning distance sensor, with which the positions of objects in the monitoring area can be determined.

[0003] In known monitoring devices, a scanning optical sensor is used in such a way that object monitoring does not take place in the entire monitoring area (i.e., the danger zone), but only within a predefined protective field at the access point. The protective field is stored as a parameter in the optical sensor, and its dimensions are optimally adapted to the danger zone being monitored.

[0004] The evaluation of the measurement data generated by the optical sensor takes place within the optical sensor itself. For this purpose, an evaluation unit is integrated into the optical sensor, which analyzes the received signals at the output of a receiver in the transceiver unit. This generates a binary object detection signal, the switching states of which indicate whether an object is located within the protective field.

[0005] This object detection signal is output to a controller, in particular a safety controller, which controls the system. If an object detection signal is output indicating that no object is present in the protective field, the system is enabled to operate. If the optical sensor generates an object detection signal with a switching state corresponding to object detection in the protective field, this signal shuts down the system via the controller to prevent hazardous situations.

[0006] For use in safety technology, particularly in personal protection, the optical sensor, especially the area distance sensor of the monitoring device, has a fail-safe design to meet the relevant safety standards; that is, the optical sensor is a safety sensor. For this purpose, the evaluation unit, in particular, has a multi-channel design, for example, in the form of two computer units that monitor each other cyclically.

[0007] Meeting these safety requirements can unnecessarily restrict the availability of the monitoring device. For example, flying debris such as dust, shavings, or similar particles can cause the optical sensor to briefly register an intrusion into the protected area, triggering the safety function and thus resulting in unnecessary downtime of the system.

[0008] Such unnecessary downtimes can in principle be avoided by specifying higher integration times for the generation of the switching signal, i.e., an average is performed in the optical sensor over a large number of measured values ​​in order to average out short-term disturbances so that they no longer influence the generation of the switching signal.

[0009] However, this increases the reaction time when generating the switching signal, which is unacceptable in many applications.

[0010] The invention is based on the objective of achieving a high level of security for a monitoring device of the type mentioned above, while simultaneously ensuring high availability.

[0011] The features of the independent claims are provided to solve this problem. Advantageous embodiments and expedient further developments of the invention are described in the dependent claims.

[0012] The invention relates to a monitoring device with sensor means for monitoring protective fields, whereby a safety function is triggered depending on sensor signals from the sensor means. The sensor means monitor two protective fields arranged opposite each other at a distance from one another, the maximum distance between the protective fields being less than or equal to the size of the smallest detectable object. The safety function is triggered only if an object is detected simultaneously in both protective fields.

[0013] The monitoring device according to the invention achieves a high level of safety for monitoring a hazardous area at a plant without unnecessarily restricting the availability of the plant.

[0014] According to the invention, this is achieved by simultaneously monitoring two protective fields with the sensor means, wherein the protective fields are arranged opposite each other at a distance from each other. It is particularly advantageous if the protective fields are arranged parallel to each other at a distance from each other. It is further advantageous if the protective fields are identical.

[0015] The closely spaced protective fields monitor a three-dimensional area, thus achieving a comprehensive and secure monitoring function.

[0016] The essential point here is that the maximum distance between the protective fields is less than or equal to the size of the smallest object to be detected, and that the safety function, i.e., in particular the shutdown of the monitored system, is only triggered if an object is registered in both protective fields simultaneously.

[0017] To ensure a safe monitoring function, it is necessary that when a person passes through the protective fields in the direction of the danger zone of the system, a safety function is triggered, which in particular shuts down the system.

[0018] This is achieved by using a person's body part as the smallest object to be detected, for example a leg or a finger.

[0019] Due to the maximum distance between the protective fields being adapted to this smallest object, it is ensured that when a person passes through the protective fields, an object intrusion in both protective fields is simultaneously registered by the monitoring device, thereby triggering the safety function and preventing any hazards to the person. The monitoring device according to the invention thus ensures a high level of safety.

[0020] Furthermore, despite the high level of security, a high availability of the monitored system is achieved.

[0021] This is based on the fact that non-safety-critical objects, such as flying small parts, chips, and the like, are considerably smaller than the distance between the protective fields and also move uncontrollably along random paths. Therefore, the probability of such small parts and the like entering both protective fields simultaneously is vanishingly small. Thus, the inventive arrangement of the protective fields and the inventive evaluation of object intrusions into the protective fields prevent unnecessary triggering of the safety function by such flying small parts and the like, thereby increasing the availability of the monitored system.

[0022] The monitoring device according to the invention comprises at least one safety sensor as a sensor means. Each safety sensor has a fail-safe design that meets the requirements of the relevant standards in the field of safety engineering.

[0023] According to a first variant, the sensor means are formed by two area distance sensors, with each area distance sensor monitoring an area protection field.

[0024] According to a second variant, the sensor means are formed by a camera sensor with which a three-dimensional detection area is monitored, with two sections of the detection area forming the protective fields.

[0025] In a third variant, the sensor means are formed by two area distance sensors, with each area distance sensor monitoring an area protection field and these two area distance sensors being monitored in a housing with a common control and safe evaluation unit.

[0026] The protective fields can form area zones or spatial zones.

[0027] In all three cases, the protective fields are configurable.

[0028] The sizes and geometries of protective fields can be specified in particular by parameters that are stored in the sensor devices or read into them.

[0029] All the aforementioned variants of safety sensors constitute AOPDDR (active opto-electronic profective device responsive to diffuse reflection) in the sense of the relevant safety standards, i.e., tactile sensor systems.

[0030] In general, safety sensors can also be used in the form of AOPDs (active opto-electronic predictive devices), i.e., optical sensors that detect objects by beam interruptions. Light curtains are an example of this.

[0031] According to an advantageous embodiment, the monitoring device has two outputs, each output being assigned to one of the two protective fields. A binary switching signal is output via each output, with the switching signal assuming the state FALSE when an object intrusion is detected in the assigned protective field. The switching signal assumes the state TRUE when no object is detected in the assigned protective field.

[0032] The switching signals are logically linked, and the safety function is triggered depending on the logical linkage.

[0033] The logical connection is such that the safety function is only triggered if both switching signals assume the switching state FALSE, which signals an object intervention.

[0034] According to an advantageous embodiment, the switching signal for a protective field is reset from the switching state FALSE to the switching state TRUE after an object intervention in this protective field if, within a time interval ΔT after this object intervention, the switching signal for the other protective field does not change from the switching state TRUE to the switching state FALSE.

[0035] This can further increase the availability of the system monitored by the monitoring device.

[0036] If an object intrusion occurs in only one protective field and no object intrusion occurs in the other protective field within the following time interval ΔT, it is highly likely that no safety-critical object intrusion occurs in the protective fields, meaning no safety function is triggered. To prevent a second object intrusion, uncorrelated with the first, from triggering the safety function within the same time interval, the switching state of the first protective field is reset to TRUE after the time interval has elapsed. This allows for a new object detection in both protective fields in an object-free state.

[0037] The reliability of the monitoring device and the availability of the monitored system can be advantageously increased by dividing each protective field into segments. The safety function is only triggered if an object intrusion is registered in corresponding, opposing segments of both protective fields.

[0038] Advantageously, the protective fields and their division into protective field segments are identically designed.

[0039] By dividing the two protective fields into individual protective field segments, spatially resolved object detection is enabled in each protective field by evaluating in which protective field segment an object intrusion occurs.

[0040] This allows safety-critical object intrusions into the protective fields, for example by people, to be distinguished even more reliably from non-safety-critical object intrusions, for example by flying small parts.

[0041] A person moves along a defined path through the protective fields, so that object intrusions in corresponding, opposite protective field segments of the protective fields are registered, which leads to the triggering of the safety function.

[0042] Since small parts move stochastically in space, they will, if at all, generate object interference in distant protective field segments in both protective fields, which does not trigger the safety function.

[0043] According to a first embodiment of the monitoring device according to the invention, the sensor means have the outputs. The switching signals are generated in the sensor means.

[0044] In this case, the evaluation of whether there are object intrusions in the protective fields takes place in the sensor devices themselves.

[0045] Advantageously, the logical linking of the switching signals takes place in the sensor devices or in a safety controller.

[0046] This is advantageous because the safety controller can control the system to be monitored, so that, depending on the result of the logical connection, the safety controller can either allow the system to operate or trigger a safety function that shuts down the system.

[0047] According to a second embodiment of the monitoring device according to the invention, measured values ​​generated in the sensor means are read into a safety controller, in which the switching signals are generated. The measured values ​​are advantageously distance values.

[0048] In particular, the logical linking of the switching signals takes place in the safety control system.

[0049] In this case, the evaluation of object intrusions into the protective fields takes place in the safety control system, and thus also the logical linking of the switching signals generated as a result.

[0050] In this variant, the protective fields are advantageously stored in the coordinate systems of the sensor means in the safety control, whereby object intrusions are detected in these.

[0051] In order to be able to directly relate the results of both protective field evaluations, especially when the protective fields are divided into protective field segments, the protective fields are converted into a global coordinate system by means of a coordinate transformation.

[0052] Then, in the global coordinate system, it is determined whether object intrusions occur in corresponding protective field segments of the protective fields.

[0053] The invention will be explained below with reference to the drawings. The drawings show: Fig. 1: Exemplary embodiment of the monitoring device according to the invention. Fig. 2a: First example of protective field monitoring using sensor means of the monitoring device according to Fig. 1. Fig. 2b: Second example of protective field monitoring using sensor means of the monitoring device according to Fig. 1. Fig. 3: First example of a safety sensor for the monitoring device according to Fig. 1. Fig. 4: Second example of a safety sensor for the monitoring device according to Fig. 1.

[0054] Fig. Figure 1 shows an embodiment of the monitoring device 100 according to the invention. The monitoring device 100 monitors access to a danger zone 1 of a plant 2. The plant 2 is controlled by a safety controller 3. The safety controller 3 has a fail-safe design, for example in the form of a multi-channel computer architecture.

[0055] In the access area is a conveyor unit 4 for transporting items 5, which are to be fed into the system 2 in a conveying direction 6. The conveyor unit 4 is protected laterally by a fence 7, which also surrounds the system 2.

[0056] To monitor access, the monitoring device has 100 sensor means, which in this case are formed by two identical area distance sensors 8.

[0057] Each area distance sensor 8 monitors a protective field 9, with different embodiments in the Fig. 2a, Fig. 2b are shown.

[0058] In this case, the protective fields 9 run in vertical planes and extend over the entire access area. Generally, the protective fields 9 can also be oriented in horizontal or inclined planes, depending on the specific application.

[0059] The protective fields 9 are arranged opposite each other such that the maximum distance between the protective fields 9 is less than or equal to the size of the smallest detectable object O.

[0060] The smallest detectable object 0 is in particular formed by a part of a person's body, e.g. a leg or a finger.

[0061] In the present case, the identically designed protective fields 9 run parallel to each other at a distance from one another.

[0062] In the embodiment of the Fig. 2b Each protective field 9 is subdivided into protective field segments 9a. The subdivision is identical for both protective fields 9.

[0063] Fig. Figure 3 shows a first embodiment of the area distance sensor 8 in the form of an optical sensor.

[0064] The area distance sensor 8 has a transmitter / receiver unit 10 with a light beam 11 emitting transmitter 12 and a light beam 11 receiving receiver 13. The transmitter 12 is, for example, formed by a laser diode, and the receiver 13 is, for example, formed by a photodiode. A receiving optic 14 is associated with the receiver 13. The transmitter / receiver unit 10 is integrated in a stationary housing 15.

[0065] Also included in the housing 15 is a deflection unit 16, which has a motor-driven deflecting mirror 17 rotatable about a rotational axis D. The light beams 11 emitted by the transmitter 12 and the light beams 11 reflected back by an object O to be detected are guided via the deflecting mirror 17. The rotation of the deflecting mirror 17 periodically guides the light beams 11 within the monitoring area. An angle encoder detects the current rotational position of the deflecting mirror 17 and thus the current direction of the light beams 11.

[0066] In this case, the transmitter / receiver unit 10 forms a distance sensor operating according to a pulse-time-of-flight method. The transmitter 12 therefore emits sequences of light pulses. To determine the distance, the time of flight of each light pulse from the transmitter 12 to an object O and back to the receiver 13 is measured. Alternatively, distance measurements can be carried out using a phase measurement method.

[0067] Fig. Figure 4 shows a second embodiment of the area distance sensor 8. In this case, a transmitter / receiver unit 10 with a light beam emitting transmitter 12 and a light beam receiving receiver 13 is arranged in a rotating measuring head 18. The measuring head 18, which is rotatable about a rotational axis D and mounted on a fixed base 19, causes the periodic deflection of the light beams 11 in the monitored area. Otherwise, the optical sensor corresponds to the Fig. 4 of the embodiment according to Fig. 3.

[0068] The area distance sensor 8 detects a two-dimensional detection area. For this purpose, the detection area is periodically scanned in individual scans with the light beams 11. Accordingly, the safety sensor 4 performs protective field monitoring in two-dimensional protective fields 9.

[0069] Each area distance sensor 8 of the monitoring device 100 forms a safety sensor.

[0070] The area distance sensor 8, designed as a safety sensor, generally has an evaluation unit in which received signals from the receiver 13 are evaluated. This generally involves monitoring the protective field by checking whether an object O is present in the protective field 9. Depending on this, the evaluation unit generates a binary switching signal as an object detection signal. The switching states of this signal indicate whether an object O is located in the protective field 9 or not. If no object O is detected in the protective field 9, the switching signal assumes the switching state TRUE. If an object O is detected in the protective field 9, the switching signal assumes the switching state FALSE. The switching signal is regenerated at the end of each scan.

[0071] To meet the requirements for using the safety sensor in safety-related applications, the evaluation unit has a fail-safe design. This is achieved, for example, by the evaluation unit consisting of two mutually monitoring computer units.

[0072] According to the invention, a safety function is only triggered in the monitoring device 100 if an object O is detected in the protective field 9 simultaneously in both area distance sensors 8.

[0073] For this purpose, the switching signals of the area distance sensors 8 are generally fed to an evaluation circuit, in this case the safety controller 3. There, an OR operation is performed on the switching signals, so that the safety function is only generated if the switching signals of both area distance sensors 8 simultaneously assume the switching state FALSE.

[0074] In the present case, the safety function consists of shutting down plant 2.

[0075] Since two area distance sensors 8 simultaneously monitor two protective fields 9, a high level of safety is maintained in the protective field monitoring.

[0076] Since the protective fields 9 are arranged at a distance from each other less than or equal to the maximum object size to be detected, determined by body parts of a person, it is ensured that a person is reliably detected by the monitoring device 100 when passing through the protective fields 9, so that the safety function is triggered and hazards to the person are avoided.

[0077] Furthermore, high availability is maintained because sporadic interference effects, such as detections of small, fast-moving particles like flying chips, are highly likely to cause a change in the switching signal from TRUE to FALSE in only one of the area distance sensors 8, as the particles are highly likely to penetrate only one of the protective fields 9. Since the switching signals are ORed in the safety controller 3, this does not lead to an unnecessary triggering of the safety function and therefore also not to an unnecessary shutdown of the system 2.

[0078] Availability can be further increased by using protective fields 9, as in Fig. 2b is shown, into which the protective field segments 9a are subdivided.

[0079] In this case, the protective field evaluation is carried out in such a way that the safety function is only triggered if an object intrusion is simultaneously registered in corresponding, opposing protective field segments 9a, which is the case when the person passes through the protective fields 9.

[0080] In contrast, random object interference by flying chips in both protective fields 9 does not trigger the safety function, since these object interferences are uncorrelated and therefore highly unlikely to occur in corresponding protective field segments 9a.

[0081] Finally, availability can be further increased by resetting the switching signal for a protective field from the switching state FALSE to the switching state TRUE after an object intervention in this protective field, if the switching signal for the other protective field does not change from the switching state TRUE to the switching state FALSE within a time interval ΔT after this object intervention.

[0082] In general, the protective field evaluation can also be transferred to the safety controller 3. In this case, the area distance sensors 8 only transmit the distance measurements to the safety controller 3.

[0083] Advantageously, the measured values ​​are calculated from distance or position values.

[0084] Furthermore, the protective fields 9 are advantageously stored in the coordinate systems of the sensor means in the safety control 3, whereby object intrusions are detected in these.

[0085] Then the protective fields 9 are converted into a global coordinate system by means of a coordinate transformation. Reference symbol list 1 Danger area 2 Annex 3 Safety control 4 conveying units 5 Item 6 Direction of conveyance 7 Fencing 8 Area distance sensor 9 Protective field 9a Protective field segment 10 Transmit / Receive Unit 11 Light beam 12 channels 13 recipients 14 Receiving optics 15 cases 16 Deflection unit 17 deflecting mirrors 18 Measuring head 19 sockets 100 monitoring device D axis of rotation O object

Claims

[1] Monitoring device (100) with sensor means by means of which a protective field monitoring is carried out, wherein a safety function is triggered depending on sensor signals from the sensor means, characterized by , that the sensor means monitor two protective fields (9) which are arranged opposite each other at a distance from each other, wherein the maximum distance between the protective fields (9) is less than or equal to the size of a smallest detectable object (O) and that the safety function is only triggered if an object (O) is registered simultaneously in both protective fields (9). [2] Monitoring device (100) according to claim 1, characterized by , that the sensor means are used to monitor two parallel protective fields (9) oriented at a distance from each other. [3] Monitoring device (100) according to one of claims 1 or 2, characterized by, that the sensor means are formed by two area distance sensors (8), wherein each area distance sensor (8) monitors an area protection field (9). [4] Monitoring device (100) according to one of claims 1 or 2, characterized by , that the sensor means are formed by a camera sensor with which a three-dimensional detection area is monitored, wherein two sections of the detection area form the protective fields (9). [5] Monitoring device (100) according to claim 4, characterized by , that the protective fields (9) form area areas or spatial areas. [6] Monitoring device (100) according to any one of claims 1 to 5, characterized by , that the protective fields (9) are configurable. [7] Monitoring device (100) according to any one of claims 1 to 6, characterized by that the sensor means are formed by safety sensors. [8] Monitoring device (100) according to any one of claims 1 to 7, characterized by, that it has two outputs, each output being assigned to one of the two protective fields (9), and a binary switching signal is output via each output, the switching signal assuming the switching state FALSE when an object intrusion is registered in the assigned protective field (9), and the switching signal assuming the switching state TRUE when no object (O) is registered in the assigned protective field (9). [9] Monitoring device (100) according to claim 8, characterized by , that the switching signals are logically linked and that the safety function is triggered depending on the logical linkage. [10] Monitoring device (100) according to claim 9, characterized by , that the safety function is only triggered if both switching signals assume the switching state FALSE, which signals an object intervention. [11] Monitoring device (100) according to one of claims 8 to 10, characterized by, that the switching signal for a protective field (9) is reset from the switching state FALSE to the switching state TRUE after an object intervention in this protective field (9), if within a time interval ΔT after this object intervention the switching signal for the other protective field (9) does not change from the switching state TRUE to the switching state FALSE. [12] Monitoring device (100) according to any one of claims 1 to 11, characterized by , that each protective field (9) is subdivided into protective field segments (9a), and that the safety function is only triggered when an object intrusion is registered in corresponding, opposite protective field segments (9a) of both protective fields (9). [13] Monitoring device (100) according to claim 12, characterized by , that the protective fields (9) and their division into protective field segments (9a) are identically designed. [14] Monitoring device (100) according to any one of claims 8 to 13, characterized bythat the sensor means have the outputs, and that the generation of the switching signals takes place in the sensor means. [15] Monitoring device (100) according to one of claims 9 and 14, characterized by , that the logical combination of the switching signals takes place in the sensor means or in a safety controller (3). [16] Monitoring device (100) according to any one of claims 8 to 13, characterized by , that measured values ​​generated in the sensor means are read into a safety controller (3) in which the switching signals are generated. [17] Monitoring device (100) according to one of claims 9 and 16, characterized by , that the logical linking of the switching signals takes place in the safety control (3). [18] Monitoring device (100) according to claim 16, characterized by that the measured values ​​are based on distance or position values. [19] Monitoring device (100) according to one of claims 16 to 18, characterized by , that the protective fields (9) are stored in the coordinate systems of the sensor means in the safety control (3), whereby object intrusions are detected in these. [20] Monitoring device (100) according to claim 19, characterized by , that the protective fields (9) are converted into a global coordinate system by means of a coordinate transformation. [21] Monitoring device (100) according to claim 20, characterized by , that in the global coordinate system it is determined whether object intrusions are present in corresponding protective field segments (9a) of the protective fields (9). [22] Monitoring device (100) according to any one of claims 1 to 21, characterized by , that the sensor means are integrated in a common housing (15) and are connected to a control and evaluation unit.

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