Monitoring device

Abstract

Monitoring device (12) for monitoring an access area (13), comprising at least one optical sensor designed for protective field monitoring, and at least one control unit in which sensor signals from the optical sensor are evaluated, wherein a safety function can be triggered in the control unit when an object is detected in a protective field (21) by means of the optical sensor, characterized in that in an initial state, a total protective field (19) extending over the entire access area (13) is monitored by the optical sensor, that in the event of an object entering the total protective field (19), triggering of the safety function is suppressed in the control unit and a timer is started if the object has a minimum size, and that, depending on the sensor signals of the optical sensor, after starting the timer, a protective field (21) and a warning field (22) are activated instead of the total protective field (19).which are adapted to the detected object, and that after the timer expires the control unit only triggers the safety function if the object is not recognized as permissible in the warning field (22) or if an object intrusion is registered in the protection field (21).

Description

The invention relates to a monitoring device. Such a monitoring device secures access to a facility. The monitoring device includes at least one safety sensor. This safety sensor monitors access to the system. It monitors a protective field that extends across the entire access area. If the safety sensor detects an object, especially a person, within the protected area, a safety function is triggered that puts the system into a safe state, so that it can no longer pose a danger. In particular, the system is shut down. To carry out work processes using the system, goods must be supplied to it. Upon passing through the access point, a safety function triggered by the safety sensor would lead to an unnecessary shutdown of the system if the goods were detected within the protected area. Therefore, known monitoring devices incorporate muting sensors positioned upstream of the safety sensor in the direction of transport of the goods. Typically, these muting sensors are formed by light barrier arrangements. Based on characteristic sequences of beam interruptions from these light barrier arrangements, goods can be distinguished from people or other safety-critical objects. If the transported goods are detected by the muting sensors, the safety sensor is bypassed, i.e., muted, so that during muting operation, the intrusion of an object into the protective field of the safety sensor does not trigger the safety function. This allows the transported goods to pass the safety sensor without triggering the safety function and shutting down the system. Once the transported goods have passed the safety sensor, the muting operation is terminated and the safety sensor resumes its monitoring function. One problem with this type of muting is that the entire safety sensor is bypassed, rendering it completely inoperable. This can lead to dangerous situations, especially if the goods being transported do not extend across the entire width of the access point. A person standing next to the goods could then pass through the access point and enter the danger zone of the system unnoticed, leading to uncontrolled hazardous situations. EP 4 151 899 A1 relates to a monitoring device for securing access to a facility, comprising an arrangement of safety sensors, each designed to detect objects within a protective field, whereby a safety function is triggered when an object is detected in at least one protective field. Furthermore, the monitoring device includes an arrangement of distance sensors by means of which the position and width of a transported item that can be fed into the facility via the access point can be detected, as well as a control and evaluation unit by means of which normal operation is defined by the safety sensors monitoring protective fields that combine to form an overall protective field extending over the entire width of the access point.With the control and evaluation unit, a muting operation can be specified by monitoring protective fields with the safety sensors, depending on the position and width of the transported goods determined by the distance sensors. These protective fields combine to form an overall protective field, in which a recess is present in the access area, which is adapted to the position and width of the transported goods so that they can pass through the access without penetrating the overall protective field. The transition from normal operation to muting operation is achieved through a time control system such that distance sensors detect a transported item and, depending on the signals from the distance sensors, the muting operation is activated shortly before the transported item enters the area of ​​the safety sensors. A disadvantage here is that the distance sensors require considerable design effort. Furthermore, the timing system must be adapted to the speed of the transported goods, which entails additional effort. EP 3 415 804 A1 relates to a safety device with at least one optical safety sensor designed to monitor a two-dimensional or three-dimensional monitoring area. The safety device further comprises a safety output circuit associated with the safety sensor, containing an arrangement of safety outputs controlled by signals from the safety sensor. Switching means are provided by which at least one protective field and / or at least one signaling field can be activated. The safety sensor generates a safety signal by switching off the safety outputs if the safety sensor detects an object within the activated protective field, or if no permissible object is detected within the activated signaling field within a predetermined time interval. The invention is based on the objective of improving the functionality of a monitoring device of the type mentioned at the outset. The features of the independent claims are provided to solve this problem. Advantageous embodiments and expedient further developments are described in the dependent claims. The invention relates to a monitoring device for monitoring an access area, comprising at least one optical sensor designed for monitoring a protective field and at least one control unit in which the sensor signals of the optical sensor are evaluated. When an object is detected within a protective field, a safety function in the control unit is triggered by the optical sensor. Initially, the optical sensor monitors the entire protective field, which extends over the entire access area. If an object enters the protective field, the control unit suppresses the triggering of the safety function and starts a timer, provided the object meets a minimum size requirement. Depending on the sensor signals from the optical sensor, after the timer has started, a protective field and a warning field, adapted to the detected object, are activated instead of the entire protective field.After the timer expires, the control unit only triggers the safety function if the object is not recognized as permissible in the warning field, or if an object intrusion is registered in the protection field. The invention also relates to a corresponding method. The monitoring device according to the invention secures an access area to a system. For this purpose, at least one optical sensor is used to monitor the access area, as well as at least one control unit that controls the optical sensor and evaluates its sensor signals. Especially when the system could pose a danger to people, the monitoring device is designed as a safety device. For this purpose, each optical sensor is designed as a safety sensor. In addition, the control unit, or at least one control unit, is designed as a safe control unit. The safety sensor(s) and the safe control unit each have a fail-safe design, which can be achieved through redundant, multi-channel computer structures. In normal operation of the monitoring device, the optical sensor(s) monitor an overall protective field that extends over the entire access area, specifically over the entire width of the access area. The overall protection zone is defined by the control unit. The optical sensor(s) detect whether or not an object is intruding within the overall protection zone, and this information is then reported to the control unit. If no object intrusion is detected within the overall protection zone, the control unit activates the system. If an object intrusion is detected within the overall protection zone, the control unit triggers a safety function, which advantageously consists of shutting down the system. In order to transport a non-safety-critical object, such as a box containing transport goods or equipment for the plant, through the access area to the plant without triggering the safety function, the monitoring device can be operated in a muting mode. According to the invention, the initiation of the muting operation depends solely on the optical sensor(s) monitoring the access area. Additional sensors monitoring the area in front of the access area are not required. Furthermore, in the monitoring device according to the invention, muting is not initiated by a timer before the non-safety-critical object enters the access area, but rather when the non-safety-critical object has already entered the access area. The muting is initiated based on the sensor signals from the optical sensor, which monitors the access area and detects the non-safety-critical object. The starting point for initiating the muting is normal operation in which the overall protection field extending over the entire access area is monitored by the optical sensor(s). If an object enters the overall protective field, the system first checks, using the sensor signals from the optical sensor(s), whether the object meets a minimum size requirement. The minimum size, i.e., minimum width, is preferably ≥ 500 mm. This allows a non-safety-critical object, such as a box, to be reliably distinguished from a person. If this is not the case, the object is classified as safety-critical, and the control unit immediately triggers the safety function. The triggering of the safety function is therefore virtually instantaneous, thus preventing unsafe situations. If the size of the object is greater than or equal to the minimum size, a timer is started, which then runs for a predetermined time, typically between 0.5 sec and 1 sec. During the timer's runtime, the control unit calculates a protective field and a warning field based on the sensor signals from the optical sensor(s) within the control unit. The protective field and the warning field are sub-areas of the overall protective field. The warning field encompasses the area in which the object was detected. The protective field borders the warning field on one or both sides. The control unit then activates the protective field and the warning field by reading them into the optical sensor(s), so that the optical sensor(s) no longer monitor the entire protective field, but only the protective field and the warning field. The control unit then uses the sensor signals from the optical sensor(s) to check whether an object is recognized as permissible within the warning field. This recognition of a permissible object can be based on predefined characteristics that must be detected on the object within the warning field. Alternatively, an object is considered to be valid if its contour matches a reference contour specified in the control unit. In extreme cases, a reference contour can even form the warning field itself. Advantageously, the control unit stops the timer as soon as the object in the warning field is recognized as permissible. The muting process then begins. Alternatively, the muting process can also start when the timer expires. In this muting mode, the safety shutdown is suppressed if the object is recognized as permissible at least once in the warning field, and if no object is registered in the protection field. This results in a high level of security combined with high availability of the system. The permissible object, as a recognized non-safety-critical object, moves within the warning field and can thus pass through the access area without the control unit triggering the safety function. To prevent the safety function from being triggered, it may be required that the permitted object be continuously recognized within the warning field. For more complex permitted objects with holes and / or recesses, this requirement can be relaxed so that the permitted object is only identified as such once within the warning field. Simultaneously, the protective field is activated following the warning field. Within the protective field, the monitoring function of the monitoring device is maintained by immediately triggering the safety function if an object intrusion is detected by the optical sensor(s) within the protective field. The protective field preferably borders directly on the warning field on both sides. This prevents a person from passing through the access area unnoticed with the permitted object, as the person would have to enter the protective field, which would immediately trigger the safety function. The muting mode ends when the permitted object has left the warning zone. Then the overall protection zone is reactivated and normal operation resumes. In principle, the monitoring device can only have one optical sensor. The monitoring device is particularly advantageous due to the two optical sensors arranged on opposite lateral edges of the access area. A permitted object passing through the access area is detected by optical sensors on opposite sides, whereupon the warning zone is defined within the area of ​​this permitted object. A sub-area of ​​the protective field then adjoins both sides of the warning zone, each monitored by an optical sensor. An advantage of any optical sensor is an area distance sensor, i.e., a scanning distance sensor with which a flat monitoring area is detected. Alternatively, the optical sensor can be a TOF (time-of-flight) camera, i.e., a camera in which distance measurements are carried out using a pulse-time method. In the simplest case, the monitoring device has only one control unit, which is designed as a safe control unit. Alternatively, the monitoring device has two control units, one of which is a safe control unit and the other is a non-safe control unit. In this case, the non-safety-related control unit calculates the protective field and the warning field based on sensor signals from the optical sensor. The safety sensors generate the safety function. The non-safety control unit can send the coordination of the protective field and the warning field to the safe control unit, which then activates the protective field and the warning field for the optical sensors. Alternatively, the non-safety control unit can directly control the optical sensor and transmit the protective field and the warning field to the optical sensor. The invention is explained below with reference to the drawings. They show: Fig. 1: First embodiment of a security sensor for the monitoring device according to the invention. Fig. 2: Second embodiment of a security sensor for the monitoring device according to the invention. Fig. 3: Schematic representation of the monitoring device according to the invention for securing an access area in a top view. Fig. 4: Side view of the access area of ​​the arrangement according to Fig. 1. Fig. 5: Different phases of monitoring the access area. Figures 1 and 2 show exemplary embodiments of safety sensors 1 in the form of distance-measuring optical sensors, wherein the distance measurements are advantageously carried out according to a pulse transit time method or a phase measurement method. Fig. 1 shows an embodiment of an optical sensor in the form of an area distance sensor, that is, a scanning distance sensor 12. For distance measurements, the optical sensor has a light beam 2 emitting transmitter 3 and a light beam 2 receiving receiver 4. The transmitter 3 emits light beams 2 in the form of light pulses. As shown in Fig. 1, the light beams 2 are reflected by a target object 5 to be detected, and the corresponding travel time of the light pulses to the target object 5 and back to the optical sensor is evaluated for distance determination. As shown in Fig. 1, the sensor components of the optical sensors are integrated in a housing 6, with the transmitter 3 and the receiver 4, each with a transmitting optic and a receiving optic 7 respectively, being stationary within the housing 6. The optical sensor detects objects within a planar detection area by periodically deflecting the light rays 2 using a deflection unit 8. The deflection unit 8 is motor-driven and comprises an angled mirror 9 rotatable about a rotational axis D, by which the light rays 2 are deflected. Fig. 2 shows a variant of the area distance sensor according to Fig. 1. In this case, the periodic deflection of the light beams 2 is achieved by arranging the transmitter 3 and the receiver 4 in a measuring head 10 rotatable about a rotational axis D, wherein the measuring head 10 is rotatably mounted on a base 11. In general, each safety sensor 1 has an evaluation unit (not shown) in which the received signals from the receiver 4 can be evaluated. For use in the field of safety technology, the safety sensors 1 according to Fig. 1 and Fig. 2 have a fail-safe design, which can be implemented, for example, by a redundant evaluation unit in the form of two processors that cyclically monitor each other. Fig. 3 schematically shows an embodiment of the monitoring device 12 according to the invention for securing the access area 13 to a system 14 in a top view. Access to the system 14 is protected on three sides by a fence 15. The open front forms the access area 13 to the system 14. A security sensor 1 in the form of an optical sensor, designed according to Fig. 1 or Fig. 2, is located at opposite edges of the access area 13. Fig. 4 shows the monitoring areas 16, which are formed by a part of the detection areas and are monitored by the optical sensors. The monitoring areas 16 run in a vertical plane, so that the protective field monitoring carried out with the optical sensors also takes place in a vertical plane. For controlling the monitoring device 12, a non-safety control unit 17 and a safety control unit 18 are provided. The safety control unit 18 has a fail-safe design due to its redundant, specifically dual-channel, computer architecture. The non-safety control unit 17 is not fail-safe and has a single-channel computer architecture. The safe control unit 18 controls the system 14. The non-safe control unit 17 is used to evaluate sensor signals from the optical sensors, for which purpose the optical sensors are connected to the non-safe control unit 17. The non-safe control unit 17 is connected to the safe control unit 18. The optical sensors are also directly connected to the safe control unit 18, so that sensor signals from the optical sensors can also be evaluated there, in particular to generate a safety-relevant output signal for controlling the system 14. The functioning of the monitoring device 12 according to the invention is explained below with reference to Figs. 5, 6, 7, 8 to 9. Fig. 5 shows the normal operation of the monitoring device 12. In normal operation, the optical sensors monitor a total protection field 19 that extends over the entire width of the access area 13. If there is no object interference in the overall protection field 19, an output signal is generated in the safe control unit depending on the sensor signals of the optical sensor, with which the operation of the system 14 is enabled. If the optical sensor detects an object intrusion within the overall protection field 19, an output signal is generated in the safe control unit, depending on the sensor signals of the optical sensors, which triggers a safety function, in particular shutting down the system 14 so that no dangers can emanate from it. Fig. 5 shows a box 20 as an example of a non-safety-critical object moving towards the access area 13 in the direction of the arrow. This box 20 should be able to pass through access area 13 without triggering the safety function. For this purpose, a muting area is initiated, as illustrated in Fig. 6 and Fig. 7. Fig. 6 shows the entry of the box 20 into the overall protective field 19, so that it is detected by the optical sensors. As a first step, the non-safety control unit checks whether the box 20 has a predefined minimum size. If this is not the case, a corresponding message is sent to the safe control unit 18, which then triggers the safety function. If the size of the box 20 is greater than or equal to the minimum size, a timer is started in the safety control unit 18, which runs for a predetermined time, typically in the range of 0.5 to 1 second. Furthermore, a protective field 21 and a warning field 22 are calculated based on the sensor signals from the optical sensors. These are adapted to the position and size of the box 20, such that the warning field 22 extends over the area of ​​the box 20 and the protective field 21, in the form of two partial protective fields, adjoins the warning field 22 on both sides, as shown in Fig. 7. The protective field 21 and the warning field 22 are calculated in the non-safety control unit 17 and transmitted to the safe control unit 18, which then transmits the protective field 21 and the warning field 22 to the optical sensors and activates them. Alternatively, this can also be done directly by the non-safety control unit 17. In one of the control units, it is checked whether the object in warning field 22 is recognized as a permissible object, which can be done based on predefined characteristics of the object. Alternatively, an object is considered to be valid if its contour matches a reference contour specified in the control unit. If this is the case and is present in protection field 21 at the object, the timer is stopped and the muting operation is started. If, however, one of the aforementioned conditions is not met during the timer's expiry, the safety function is triggered. In muting mode, as shown in Fig. 7, it is monitored whether the permissible object is present in warning field 22. If this is the case, at least temporarily, and there is no object intrusion in the protective field 21, the box 20 can pass through the access area 13 without triggering the safety function. As soon as the box 20 leaves the access area 13 ( Fig. 8 ), the muting operation is changed and a transition to normal operation takes place, in which the total protection field 19 is monitored again. Reference symbol list 1 Safety sensor 2 Light beam 3 Transmitter 4 Receiver 5 Target object 6 Housing 7 Receiving optics 8 Deflection unit 9 Angle mirror 10 Measuring head 11 Base 12 Monitoring device 13 Access area 14 System 15 Fencing 16 Monitoring area 17 Non-safe control unit 18 Safe control unit 19 Overall protection field 20 Box 21 Protection field 22 Warning field D Rotation axis

Claims

Monitoring device (12) for monitoring an access area (13), comprising at least one optical sensor designed for protective field monitoring, and at least one control unit in which sensor signals from the optical sensor are evaluated, wherein a safety function can be triggered in the control unit when an object is detected in a protective field (21) by means of the optical sensor, characterized in that in an initial state, a total protective field (19) extending over the entire access area (13) is monitored by the optical sensor, that in the event of an object entering the total protective field (19), triggering of the safety function is suppressed in the control unit and a timer is started if the object has a minimum size, and that, depending on the sensor signals of the optical sensor, after starting the timer, a protective field (21) and a warning field (22) are activated instead of the total protective field (19).welche an das erfasste Objekt angepasst sind, und dass nach Ablauf des Timers die Steuereinheit die Sicherheitsfunktion nur dann auslöst, wenn im Warnfeld (22) das Objekt nicht als zulässig erkannt wird oder wenn im Schutzfeld (21) ein Objekteingriff registriert wird., Monitoring device (12) according to claim 1 characterized in that the safety function is suppressed when the object is recognized as permissible at least once in the warning field (22), and when no object is registered in the protective field (21). Überwachungseinrichtung (12) nach einem der Ansprüche 1 oder 2,dadurch gekennzeichnet, dass die Steuereinheit den Timer stoppt, sobald das Objekt im Warnfeld (22) als zulässig erkannt wird. Monitoring device (12) according to one of claims 1 to 3, characterized in that the control unit triggers the safety function when the size of the object detected in the overall protective field (19) is smaller than the minimum size. Monitoring device (12) according to one of claims 1 to 4, characterized in that an object is deemed to be permissible if its contour matches a reference contour specified in the control unit. Monitoring device (12) according to one of claims 1 to 5, characterized in that the overall protective field (19) is reactivated as soon as the permissible object has left the warning field (22). Überwachungseinrichtung (12) nach einem der Ansprüche 1 bis 6,dadurch gekennzeichnet, dass das Schutzfeld (21) und das Warnfeld (22) Teilbereiche des Gesamtschutzfelds (19) sind. Überwachungseinrichtung (12) nach einem der Ansprüche 1 bis 7,dadurch gekennzeichnet, dass sich das Gesamtschutzfeld (19) über die gesamte Breite des Zugangsbereichs (13) erstreckt. Monitoring device (12) according to one of claims 1 to 8, characterized in that it has two optical sensors arranged on opposite lateral edges of the access area (13). Überwachungseinrichtung (12) nach einem der Ansprüche 1 bis 9,dadurch gekennzeichnet, dass der oder jeder optische Sensor ein Flächendistanzsensor ist. Überwachungseinrichtung (12) nach einem der Ansprüche 1 bis 10,dadurch gekennzeichnet, dass der oder jeder optische Sensor ein Sicherheitssensor (1) ist. Überwachungseinrichtung (12) nach einem der Ansprüche 1 bis 11,dadurch gekennzeichnet, dass diese nur eine Steuereinheit, die als sichere Steuereinheit (18) ausgebildet ist, aufweist. Monitoring device (12) according to one of claims 1 to 11, characterized in that it has two control units, wherein one control unit is a safe control unit (18) and the other control unit is a non-safe control unit (17). Monitoring device (12) according to claim 13, characterized in that the non-safety control unit (17) calculates the protective field (21) and the warning field (22) on the basis of sensor signals from the optical sensor, and that the safety sensors (1) generate the safety function. Method for operating a monitoring device (12) for monitoring an access area (13), comprising at least one optical sensor designed for protective field monitoring, and at least one control unit in which sensor signals from the optical sensor are evaluated, wherein a safety function can be triggered in the control unit when an object is detected in a protective field (21) by means of the optical sensor, characterized in that in an initial state, a total protective field (19) extending over the entire access area (13) is monitored by the optical sensor, that in the event of an object entering the total protective field (19), triggering of the safety function is suppressed in the control unit and a timer is started if the object has a minimum size, and that, depending on the sensor signals of the optical sensor, after starting the timer, a protective field (21) and a warning field (22) are activated instead of the total protective field (19).which are adapted to the detected object, and that after the timer expires the control unit only triggers the safety function if the warning field (22) of the object is not recognized as permissible, or if an object intrusion is registered in the protection field (21).

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