MONITORING DEVICE AND A METHOD FOR OPERATING A MONITORING DEVICE

Description

[0001] The invention relates to a monitoring device and a method for operating a monitoring device.

[0002] Known monitoring devices typically comprise a sensor arrangement, which is particularly designed as a safety sensor arrangement and is thus suitable for use in the field of security technology. The sensor arrangement comprises at least one light curtain, which typically has a series arrangement of light beam emitting transmitters in a first housing and a series arrangement of light beam receiving receivers in a second housing.

[0003] The light curtain implements a monitoring function in such a way that the received signals from the receivers are evaluated in an evaluation unit of the light curtain, generating a binary switching signal whose switching states indicate whether or not an object is present in a protective field monitored by the light curtain. If an object is detected in the protective field, the resulting switching signal triggers a safety function, for example, shutting down a dangerous machine or system monitored by the light curtain.

[0004] A typical application for such a sensor arrangement is access protection to a hazardous area of ​​a dangerous machine or system. Access to the hazardous area is via a conveyor unit monitored by the light curtain.

[0005] The monitoring function of the light curtain should then be designed in such a way that the passage of safety-critical objects, in particular persons, is detected by the light curtain so that the safety function is triggered to avoid dangerous situations.

[0006] However, permissible objects, i.e. generally non-safety-critical objects, such as workpieces or loads that must be fed to the machine or system to carry out work processes, should not trigger the safety function in order to avoid unnecessary downtimes of the machine or system.

[0007] To achieve this, a muting function is provided for the sensor arrangement in a known manner.

[0008] For example, muting sensors can be installed upstream of the light curtain in the conveying direction of the conveyor unit to detect permissible objects. If this is the case, the light curtain's monitoring function is muted, i.e., bypassed, for a specified time, allowing permissible objects to pass through the light curtain without generating a switching signal that triggers the safety function.

[0009] The disadvantage here is that the muting sensors, as additional sensors, undesirably increase the installation effort of the monitoring system. Furthermore, synchronization of these muting sensors and the light curtain is required.

[0010] A general disadvantage of known muting procedures is that gaps can occur next to the permitted object in the protective field, meaning, for example, that a person may be positioned next to the permitted object in the protective field. Activating the muting function in this case represents an uncontrolled hazardous situation, since the person or, in general, a safety-critical object is located in the protective field without the light curtain triggering the required safety function.

[0011] WO 2019 / 154862 A1 relates to a monitoring device for monitoring a boundary area of ​​a safety zone. The monitoring device comprises a light curtain for detecting an object at the boundary area. At least one radar sensor is also provided to detect the movement of objects. Finally, an evaluation unit is provided that generates an output signal depending on signals from the light curtain and the radar sensor. In particular, a muting function is implemented depending on signals from the light curtain and the radar sensor.

[0012] The invention is based on the object of increasing the functionality and safety of danger area monitoring by means of a monitoring device of the type mentioned above.

[0013] To achieve this object, the features of the independent claims are provided. Advantageous embodiments and expedient developments of the invention are described in the dependent claims.

[0014] The invention accordingly relates to a monitoring device with a sensor system designed to detect objects in a monitoring area, and with an evaluation unit designed to evaluate sensor signals from the sensor system. The monitoring device forms a safety system for safeguarding a hazardous area of ​​a plant, and a safety function is only triggered in the evaluation unit if a safety-critical object is detected in the monitoring area. As a safety function, the plant is shut down. The sensor system consists exclusively of radar sensors, with a time-resolved evaluation of the sensor signals from the radar sensor(s) used to differentiate between non-safety-critical objects and safety-critical objects.

[0015] The invention further relates to a corresponding method.

[0016] A significant advantage of the invention is that the radar sensor(s) can be used to clearly identify safety-critical objects and, in particular, to reliably distinguish them from non-safety-critical objects.

[0017] This means that a safety function is only generated if a safety-critical object is detected in the monitoring area, but not if a non-safety-critical object is detected there.

[0018] On the one hand, this ensures a high level of security in the monitoring function of the monitoring device, since safety-critical objects such as

[0019] For example, people who lead to hazardous situations are reliably detected and trigger the safety function. On the other hand, unnecessary triggering of the safety function in the presence of a non-safety-critical object is avoided.

[0020] These advantages are particularly evident when the monitoring device is used to protect a hazardous area of ​​a system, with the system being shut down as a safety function.

[0021] The danger area can be a material transfer area.

[0022] In general, the system can also be designed as a machine or robot, although the system can generally pose hazards, particularly to people. The material transfer area can, for example, be formed by a conveyor unit, through which transported goods are fed into the system as non-safety-critical objects.

[0023] The monitoring device according to the invention achieves a high level of safety in the monitoring of hazardous areas on the system, since dangerous interventions by safety-critical objects are reliably detected and lead to the shutdown of the system, so that no further dangers can arise from the system.

[0024] At the same time, the availability of the system is increased because non-safety-critical objects are detected as such by the radar sensors and thus do not lead to an unnecessary shutdown of the system.

[0025] This results in a significant advantage of the monitoring device according to the invention in that it can implement muting functions without the need for separate muting sensors. The radar sensors of the monitoring device can fulfill more than just the safety function of detecting safety-critical objects.

[0026] Rather, they can easily implement a muting function by detecting non-safety-critical objects as such and preventing the safety function from being triggered. For example, in hazardous area monitoring on a system, non-safety-critical objects can be detected in the material transfer area, particularly on a conveyor unit, and can be fed into the system unhindered by suppressing the safety function.

[0027] According to an advantageous embodiment of the invention, the radar sensors determine the movement profiles of objects. Depending on the movement profiles, the objects are classified in the evaluation unit.

[0028] Depending on the movement profile of an object, it is classified as a non-safety-critical object or as a safety-critical object, whereby the safety function is only triggered when a safety-critical object is detected in the evaluation unit.

[0029] The monitoring device according to the invention thus exploits the property of radar sensors that allows them to detect precise movements of objects, particularly their direction and speed. By analyzing the type of movement, different objects can be classified. For example, if a pallet or any other transported goods move on a conveyor, they move uniformly. Such uniform movement can be reliably distinguished from non-uniform movements, such as those performed by a person.

[0030] According to the invention, different moving objects, such as transport goods and persons or generally non-safety-critical objects and safety-critical objects, are reliably distinguished by a time-resolved evaluation of the sensor signals of the radar sensor(s).

[0031] In general, the detection of object movements using a radar sensor is based on the Doppler effect. The frequency of a transmitted radar signal is continuously varied across a frequency band and compared with the frequency of the radar signal reflected back from the object. The determined frequency difference can be used to determine the travel time of the radar signal to an object and back to the radar sensor, thereby determining the object's distance.

[0032] It is particularly advantageous if the radar sensor or sensors operate according to the FMCW (frequency modulated continuous wave) method.

[0033] The radar sensor or sensors preferably emit radar waves in the frequency range from 9 GHz to 148.5 GHz. The frequency band of the radar sensor may be smaller than the specified frequency range.

[0034] In general, other comparable measuring methods can of course also be used.

[0035] According to a first variant, the evaluation unit is integrated in the radar sensor or in a radar sensor.

[0036] According to a second variant, the evaluation units and the radar sensor(s) each form separate units.

[0037] This variant is advantageous if the monitoring device has several radar sensors that are connected to a common evaluation unit.

[0038] According to an advantageous embodiment, a binary switching signal is generated in the evaluation unit depending on the sensor signals of the radar sensor(s), the switching states of which indicate whether a safety-critical object is present in the monitoring area or not, and that the safety function is triggered depending on the switching signal.

[0039] For example, the switching signal from the evaluation unit can be output to a control unit that controls a hazardous system to be monitored. The control unit can then generate a safety function that shuts down the system.

[0040] According to an advantageous development of the invention, the evaluation unit has a control input via which control signals from a controller can be read in.

[0041] The control signals can be used to specify a time interval within which a non-safety-critical object passes the monitoring area.

[0042] In particular, the control signals are muting signals.

[0043] The controller can, for example, control a conveyor unit, where goods or similar non-safety-critical objects are transported on the conveyor unit to be fed to a hazardous facility. The controller knows the conveyor speed of the conveyor unit. Furthermore, the controller knows the times at which the individual non-safety-critical objects are fed into the facility. This also means that the controller knows when the non-safety-critical objects pass through the monitoring area detected by the radar sensor(s).

[0044] This allows the controller to specify muting time intervals during which non-safety-critical objects pass through the monitoring area. During these muting time intervals, the triggering of the safety function is then suppressed.

[0045] In this case, the radar sensors can perform an additional muting monitoring function by monitoring whether, in addition to a non-safety-critical object, a safety-critical object is present in the monitoring area during a muting time interval. If this is the case, the muting function is immediately canceled and the safety function is triggered.

[0046] The invention is explained below with reference to the drawings. They show: Fig. 1: Schematic representation of an embodiment of the monitoring device according to the invention. Fig. 2: Schematic representation of a radar sensor for the monitoring device according to Figure 1 .

[0047] Figure 1 shows a highly schematic embodiment of the monitoring device 1 according to the invention. In the present case, the monitoring device 1 serves to safeguard a danger zone on a system 2 from which dangers to persons can arise. A conveyor unit 3 forms a material transfer area in which transport goods such as pallets 4 are fed to the system 2 so that the system 2 can carry out work processes. The pallets 4, one of which is Figure 1 are conveyed at a conveying speed F on the conveying unit 3. The conveying unit 3 can be designed in the form of a conveyor belt or a roller conveyor.

[0048] The monitoring device 1 comprises a number of radar sensors 5 connected to an evaluation unit 6. The monitoring device 1 forms a safety system designed for use in the field of safety technology. For this purpose, the monitoring device 1 has a fail-safe design, which is achieved in particular by a redundant design of the evaluation unit 6, for example, in the form of two cyclically monitoring computer units.

[0049] In Figure 1 four radar sensors 5 are shown, which monitor an area of ​​the conveyor unit 3 as a monitoring area.

[0050] Figure 2 shows schematically the structure of a radar sensor 5. The radar sensor 5 has a transmitter 8 emitting radar signals 7 and a receiver 9 which receives radar signals 7 reflected back from a target object 10.

[0051] The radar sensor 5 can generally detect the movements of objects.

[0052] In general, the detection of object movements using a radar sensor 5 is based on the Doppler effect. The frequency of a transmitted radar signal 7 is continuously varied across a frequency band and compared with the frequency of the radar signal 7 reflected back from the object. The determined frequency difference allows the travel time of the radar signal 7 to an object and back to the radar sensor 5 to be determined, thereby determining the object distance.

[0053] It is particularly advantageous if the or each radar sensor 5 operates according to the FMCW (frequency modulated continuous wave) method.

[0054] The or each radar sensor 5 preferably emits radar waves in the frequency range from 9 GHz to 148.5 GHz. The frequency band of the radar sensor may be smaller than the specified frequency range.

[0055] The sensor signals from radar sensors 5 are evaluated in the evaluation unit 6. Based on the sensor signals, object movement profiles are determined, and based on these, object classifications are performed to determine whether an object is a safety-critical object or a non-safety-critical object. A load transported on the conveyor unit 3 moves uniformly and is therefore classified as a non-safety-critical object. A person, on the other hand, does not move uniformly and is therefore classified as a safety-critical object.

[0056] Based on this evaluation, a binary switching signal is generated in the evaluation unit 6, which is output via a switching output 11. The switching states of the switching signal indicate whether a safety-critical object is present in the monitoring area or not. If a safety-critical object is detected, a safety function is triggered with the corresponding switching signal. For example, the switching signal is output to a control unit controlling system 2, with the control unit shutting down system 2 as a safety function.

[0057] However, if non-safety-critical objects are detected, no safety function is triggered. This provides a simple way to implement a muting function so that non-safety-critical objects can pass through the monitoring area without shutting down system 2.

[0058] How Figure 1As shown, the evaluation unit 6 has a control input 12. Control signals from a controller 13 are read in via the control input 12.

[0059] In this case, the controller 13 controls the conveyor unit 3. The conveyor speed F of the conveyor unit 3 is known to the controller 13. Furthermore, the times at which the individual non-safety-critical objects are fed to the system 2 are known to the controller 13. Thus, the controller 13 also knows when the non-safety-critical objects pass the monitoring area detected by the radar sensor(s) 5.

[0060] This allows the controller to specify 13 muting time intervals during which non-safety-critical objects pass through the monitoring area. During these muting time intervals, the triggering of the safety function is then suppressed.

[0061] In this case, the radar sensors 5 can assume an additional muting monitoring function by monitoring whether, in addition to a non-safety-critical object, a safety-critical object is also present in the monitoring area during a muting time interval. If this is the case, the muting function is immediately canceled and the safety function is triggered. List of reference symbols

[0062] (1)Monitoring device (2)System (3)Conveyor unit (4)Pallet (5)Radar sensor (6)Evaluation unit (7)Radar signal (8)Transmitter (9)Receiver (10)Target object (11)Switching output (12)Control input (13)Control FConveyor speed

Claims

1. A monitoring device (1) with a sensor system which is designed to detect objects in a monitoring area, and with an evaluation unit (6) which is designed to evaluate sensor signals from the sensor system, wherein the monitoring device (1) forms a safety system for safeguarding a danger area of an installation (2), and a safety function is only triggered in the evaluation unit (6) if a safety-critical object is detected in the monitoring area, wherein the installation (2) goes into standby mode as a safety function, if a safety-critical object is detected in the monitoring area, characterised in that the sensor system consists exclusively of radar sensors (5), whereby non-safety-critical objects and safety-critical objects are distinguished by a time-resolved evaluation of the sensor signals of the radar sensor or sensors (5).

2. A monitoring device (1) according to claim 1, characterised in that the evaluation unit (6) is integrated in said or in a radar sensor (5).

3. A monitoring device (1) according to claim 1, characterised in that the evaluation unit (6) and the radar sensor or sensors (5) each form separate units.

4. A monitoring device (1) according to one of claims 1-3, characterised in that said or each radar sensor (5) operates according to the FMCW (frequency modulated continuous wave) method.

5. A monitoring device (1) according to one of claims 1 - 4, characterised in that said or each radar sensor (5) emits radar waves in the frequency range from 9 GHz to 148.5 GHz.

6. A monitoring device (1) according to one of claims 1-5, characterised in that a binary switching signal is generated in the evaluation unit (6) as a function of the sensor signals of the radar sensor or sensors (5), the switching states of which indicate whether or not a safety-critical object is present in the monitoring area, and in that the safety function is triggered as a function of the switching signal.

7. A monitoring device (1) according to one of claims 1 to 6, characterised in that the danger zone is a material transfer zone.

8. A monitoring device (1) according to one of claims 1 to 7, characterised in that the radar sensors (5) are used to determine movement profiles of objects, and in that a classification of the objects is carried out in the evaluation unit (6) as a function of the movement profiles.

9. A monitoring device (1) according to claim 8, characterised in that, depending on a movement profile of an object, this is classified as a non-safety-critical object or as a safety-critical object, whereby the safety function is only triggered when a safety-critical object is detected in the evaluation unit (6).

10. A monitoring device (1) according to one of claims 1 to 9, characterised in that the evaluation unit (6) has a control input (12) via which control signals from a control unit (13) can be read in.

11. A monitoring device (1) according to claim 10, characterised in that the control signals can be used to preset a time interval within which a non-safety-critical object passes the monitoring area.

12. A monitoring device (1) according to claim 11, characterised in that the control signals are muting signals.

13. A method for operating a monitoring device (1) with a sensor system which is designed to detect objects in a monitoring area, and with an evaluation unit (6) which is designed to evaluate sensor signals from the sensor system, wherein the monitoring device (1) forms a safety system for safeguarding a danger area of an installation (2), and wherein a safety function is triggered in the evaluation unit (6) when a safety-critical object is detected in the monitoring area, wherein the system (2) goes into standby mode as a safety function, characterised in that the sensor system consists exclusively of radar sensors (5), wherein non-safety-critical objects and safety-critical objects are distinguished by a time-resolved evaluation of the sensor signals of the radar sensor or sensors (5).