SENSOR ARRANGEMENT AND METHOD FOR HAZARD AREA MONITORING

Description

[0001] The invention relates to a sensor arrangement and a method for monitoring hazardous areas on a work tool.

[0002] Such a sensor arrangement comprises at least one sensor with which a protective field can be monitored. With such a sensor arrangement, a hazardous area on a piece of equipment, such as a machine or system, can be monitored.

[0003] An example of this is access control to a machine whose danger zone is secured by a fence. The fence contains an entrance opening through which a conveying unit, in particular a conveyor belt, is routed to supply material to the machine. The entrance opening can be protected by a sensor, such as a light curtain. If the light curtain detects an object entering the machine, a safety signal is generated, causing the machine to shut down. This prevents anyone attempting to enter the danger zone through the entrance opening from being endangered.

[0004] To prevent unnecessary machine shutdowns caused by incoming material entering the protective field, muting sensors are installed upstream of the light curtain in the conveying direction of the conveyor unit. These sensors detect material moving towards the light curtain. When the sensors detect material, they generate a muting signal that mutes the safety function of the light curtain. During muting, the light curtain does not generate a safety signal even if an object is detected entering its protective field. This allows the material to pass unimpeded on the conveyor unit without shutting down the machine, thus preventing unnecessary downtime. This muting is maintained as long as material is being fed into the machine.Afterwards, the muting is stopped and the safety function of the light curtain is reactivated, so that object interference registered in the protective field of the light curtain then leads to the generation of the safety signal and the shutdown of the machine.

[0005] The disadvantage here is that, in order to determine whether an object interference in the sensor leads to the generation of a safety signal or not, additional sensors are required with the muting sensors, which significantly increases the effort of the sensor arrangement.

[0006] EP 2 017 524 A2 relates to a light grid used for detecting objects within a monitored area. The grid comprises several beam axes, each formed by a transmitter emitting light beams and an associated receiver. When the monitored area is clear, the beam axes are uninterrupted; however, if an object enters the monitored area, at least one beam axis is interrupted. The light grid also includes an evaluation unit that generates an object notification when a safety-critical object enters the monitored area.In the evaluation unit, a non-safety-critical object can be identified as it passes through the monitoring area by registering the beam axes interrupted by the non-safety-critical object during at least one approach phase and one transit phase (as distinct muting phases). This data is then used to check whether specific object characteristics of the non-safety-critical object, stored in the evaluation unit, are met during the approach and transit phases. A muting signal is generated in the evaluation unit when a non-safety-critical object is identified.

[0007] 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.

[0008] EP 1 835 310 A2 relates to a light grid for detecting objects in a monitored area with a predetermined number of emitting light beams from transmitters and receivers. Each receiver and at least one associated transmitter form a beam axis with an evaluation unit in which received signals at the receiver outputs are evaluated to generate an object detection signal. At least one control signal can be read into the evaluation unit for parameterizing beam axes during operation of the light grid.

[0009] DE 10 2006 008 805 A1 relates to an optical sensor and a method for monitoring a safety zone on a piece of equipment using an optical sensor with a camera and an evaluation unit. If a safety-critical object is detected in the safety zone, an object alert is generated, which shuts down the equipment. If a non-safety-critical object is detected within the safety zone, at least one section of this zone is bypassed, so that the intrusion of a safety-critical object into this section does not trigger an object alert.

[0010] The invention is based on the objective of providing a sensor arrangement that offers high functionality with minimal design effort.

[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 sensor arrangement for monitoring hazardous areas on a work tool, comprising at least one sensor designed to monitor a protective field. This protective field monitors lateral access to the work tool. A control and evaluation unit is provided, which distinguishes between hazardous and non-hazardous object intrusions by objects within the protective field. This is achieved by performing a spatially and, optionally, temporally resolved analysis of the object intrusions. The control and evaluation unit generates a safety signal only when a hazardous object intrusion occurs, regardless of whether the object is safety-critical or non-safety-critical.

[0013] The invention further relates to a method for monitoring the danger zone on a work tool.

[0014] The basic idea of ​​the invention is therefore to classify interventions on objects according to whether they are hazardous or non-hazardous. For this purpose, a spatially resolved and, if necessary, also temporally resolved analysis of the interventions on the objects is carried out.

[0015] A particularly advantageous feature is the ability to detect, with at least one sensor, in which areas of the protected field an object intrusion occurs. The control and evaluation unit then classifies the intrusion based on these areas, determining whether it is hazardous or non-hazardous.

[0016] The safety concept according to the invention differs from known safety concepts that distinguish between safety-critical and non-safety-critical objects. In those latter concepts, safety-critical objects, such as people, are distinguished from non-safety-critical objects, such as workpieces, based on characteristic features. If a safety-critical object is then detected by a sensor, a safety signal is necessarily generated, whereas the detection of a non-safety-critical object does not lead to the generation of a safety signal.

[0017] In contrast, with the sensor arrangement according to the invention, a person who would be classified as a safety-critical object according to known safety concepts can cause both a hazardous and a non-hazardous object interference. A non-hazardous object interference could, for example, consist of the person reaching through the protective field with an arm to perform a work process in the area of ​​the work equipment, such as a packaging or assembly operation. A hazardous object interference could, for example, consist of a person attempting to climb into the area of ​​the work equipment and thereby entering the area of ​​the protective field.

[0018] Such hazardous object interventions and non-hazardous object interventions can be distinguished in the sensor arrangement according to the invention, so that only hazardous object interventions lead to the generation of a safety signal, which is designed in particular as a shutdown command for the work equipment, thereby increasing the availability of the work equipment.

[0019] A key advantage of the invention is that the sensor(s) for monitoring the protective field, together with the control and evaluation unit, form a self-contained system that can be used for monitoring the hazardous area of ​​the work equipment without complex programming. In particular, neither additional sensors nor complex learning processes are required to perform the hazardous area monitoring according to the invention, especially the differentiation between hazardous and non-hazardous object interventions.

[0020] Since the sensor arrangement according to the invention forms a self-contained system, complex interfaces to other units are unnecessary, which means that the sensor arrangement according to the invention can be manufactured cost-effectively. The sensor arrangement according to the invention is also characterized by simple commissioning.

[0021] According to an advantageous embodiment of the invention, the control and evaluation unit performs time monitoring of object interventions.

[0022] Depending on the operating state of the equipment, hazardous and non-hazardous object interventions can vary in type, form, and location within the protective field(s). Monitoring these interventions over time allows for adjustments to be made based on such time-dependent factors.

[0023] In particular, object manipulations are only permitted at predetermined times. If an unauthorized object manipulation is detected, the control and evaluation unit generates a security signal.

[0024] According to an advantageous embodiment, at least one sensor is a safety sensor.

[0025] The sensor has a fail-safe design and can therefore be used for applications in the field of safety technology.

[0026] It is advantageous if the control and evaluation unit is integrated into at least one sensor, or if the control and evaluation unit is a safety controller.

[0027] If the control and evaluation unit is integrated into a safety sensor, it has a correspondingly fail-safe design. The safety controller, in which the control and evaluation unit may be integrated, also has a fail-safe design.

[0028] In both cases, it is ensured that the sensor arrangement as a whole has a fail-safe design and can be used in applications in the field of safety technology.

[0029] It is advantageous to have at least one sensor that is an optical sensor or a radar sensor.

[0030] In particular, at least one sensor is an area distance sensor or a light curtain.

[0031] According to a particularly advantageous embodiment of the invention, the working device is a conveying unit which is secured on opposite sides by a sensor, wherein the protective fields protrude upwards over a conveying surface of the conveying unit.

[0032] In this case, the sensors are particularly usefully formed by a light curtain with several beam axes, whereby the control and evaluation unit registers which of the beam axes are interrupted when an object is disturbed. The safety signal is then generated based on this information.

[0033] Area distance sensors can also be used instead of light curtains.

[0034] In this embodiment, the sensor arrangement according to the invention enables persons to reach through the protective fields with their hands to carry out work processes on the conveyor unit without the sensor arrangement generating a safety signal that would lead to the conveyor unit being stopped, since these interventions are recognized as non-hazardous object interventions, in particular because only central beam axes of the light curtain are interrupted.

[0035] The evaluation is carried out in such a way that the interruption of the uppermost beam axis or beam axes of a light curtain is considered a dangerous object interference in the control and evaluation unit.

[0036] This makes it possible to detect if a person is attempting to climb over the protective field into the area of ​​the conveying unit without authorization.

[0037] Furthermore, the interruption of the lowest beam axis or beam axes of a light curtain in the control and evaluation unit is considered a dangerous intervention in the object.

[0038] This records when a person attempts to crawl onto the conveyor unit under the protective field of the light curtain without authorization.

[0039] Since climbing over or crawling under the protective fields of the light curtains requires a certain amount of time, it is advantageous if a safety signal is only generated when the uppermost and / or lowermost beam axes are interrupted for a specified minimum time.

[0040] This allows short-term, non-critical intrusions into the protective fields to be ignored as non-hazardous object intrusions.

[0041] The invention will be explained below with reference to the drawings. The drawings show: Figure 1: Schematic representation of a sensor arrangement according to the invention a) in a top view b) in a side view c) in a longitudinal section Figure 2: Sensor in the form of an area distance sensor for the sensor arrangement according to Figure 1 Figure 3: Sensor in the form of a light curtain for the sensor arrangement according to Figure 1Figure 4: Perspective view of an embodiment of the sensor arrangement according to the invention. Figure 5: Longitudinal section view of the sensor arrangement according to the invention. Figure 1 .

[0042] The Figures 1a to 1c show schematically the structure of the sensor arrangement according to the invention 1.

[0043] Sensor arrangement 1 is used for monitoring the hazardous area of ​​a piece of equipment. In this case, the equipment consists of a conveyor belt 2, which is located, for example, between two processing stations 3 and on which objects 4 can be transported. The equipment could also be a conveyor belt, a robot cell, or the like. One long side of the conveyor belt 2 is enclosed by a wall 5 and thus protected against access. The other long side is open. This open long side is protected by a sensor 6.

[0044] Sensor 6 includes sensor components 6a, which generate a protective field 7. Sensor 6 includes an evaluation unit 6b, which evaluates the sensor signals generated in the sensor components 6a.

[0045] As from the Figures 1a to 1c As can be seen, the protective field 7 detected by the sensor 6 extends over the entire length of the conveyor belt 2 and protrudes perpendicularly from the top of the conveyor belt 2, which lies in a horizontal plane and forms a conveying surface 2a, so that the protective field 7 provides complete lateral protection of the conveyor belt 2.

[0046] According to the invention, object detection takes place in the evaluation unit 6b of the sensor 6, which in the present case forms a control and evaluation unit of the sensor arrangement, in such a way that hazardous object interferences are distinguished from non-hazardous object interferences.

[0047] For this purpose, a spatially resolved evaluation is performed in evaluation unit 6b to determine in which areas of the protective field 7 object intrusions occur. These areas are then classified according to whether they pose a danger or not. A non-hazardous object intrusion occurs, for example, when a person P reaches through the protective field 7 to handle objects 4 on the conveyor belt 2. In this case, the intrusion is locally confined within the protective field 7. A hazardous object intrusion occurs, for example, when the person P climbs onto the conveyor belt 2, thereby causing a large-scale breach of the protective field 7.

[0048] Additionally, time monitoring of object interventions in the protection field 7 can also be carried out, whereby in particular certain object interventions in the protection field 7 are only permitted at certain times.

[0049] Accordingly, evaluation unit 6b generates a binary switching signal whose switching states indicate whether or not a hazardous object interference has occurred. The switching signal is output to a controller for conveyor belt 2.

[0050] For use in safety engineering applications, sensor 6 is designed as a safety sensor. The evaluation unit 6b has a fail-safe design, specifically in the form of two mutually monitoring computer units. The controller is also designed as a safety controller 8, which likewise can have two mutually monitoring computer units.

[0051] If a hazardous object intrusion within the protective field 7 is detected by sensor 6, the sensor generates a switching signal with a corresponding switching state. This constitutes a safety signal that leads to the shutdown of the conveyor belt 2 by the safety controller 8.

[0052] Sensor 6 can be configured as a radar sensor or the like. In this case, sensor 6 is configured as an optical sensor. Figures 2 and 3 Figure 1 shows exemplary embodiments of the optical sensor in the form of an area distance sensor 9 or a light curtain 10.

[0053] Figure 2 Figure 1 shows an embodiment of an area distance sensor. The area distance sensor shown there has a transmitting light beam 11a and a receiving light beam 11b receiver, which together form a distance sensor operating according to a pulse-time method. To determine the distance to an object 13, an evaluation unit 14 (corresponding to the evaluation unit 6b of the sensor 6 according to the Figures 1a to 1cThe transit time of the transmitted light beams 11a from transmitter 11 to object 13 and back to receiver 12 is determined and converted into a distance value. The transmitter 11 and receiver 12 are arranged in a rotating measuring head 15. This sits on a stationary base 16, in which the evaluation unit 14 is housed. The motor-driven measuring head 15 rotates about a vertical axis of rotation (referring to the illustration according to...). Figure 2 These sensor components 6a are arranged in a housing 17 mounted on the base 16. The transmitting light beams 11a and receiving light beams 11b are guided through a window 18 in the housing 17. A switching output 19 for signal output is connected to the evaluation unit 14.

[0054] The rotational movement of the measuring head 15 causes the transmitted light beams 11a to be periodically deflected in a scanning area lying in a horizontal plane.

[0055] The angular range of the scanning area is determined by the extent of the window 18 in the circumferential direction of the housing 17.

[0056] By continuously measuring distances and determining the current angular positions of the transmitted light beams 11a, a position determination of objects 13 in the scanning area can be carried out.

[0057] For use in the field of security technology, the evaluation unit 14 has a redundant design in the form of two computer units that monitor each other cyclically.

[0058] Figure 3 Figure 1 shows an optical sensor in the form of a light curtain 10, by means of which a planar monitoring area is monitored. The light curtain 10 has a transmitter unit 20 and a receiver unit 21, the components of which are each integrated in a housing and which are arranged at opposite edges of the monitoring area.

[0059] Transmitter unit 20 contains a series of light beams 22 emitting transmitters 11', while receiver unit 21 contains a corresponding number of receivers 12'. Each transmitter 11' and its opposite receiver 12' form a beam axis. The beam axes are cyclically activated individually and sequentially by a transmitter control unit (not shown) and optical synchronization. Object detection is based on the principle of light barriers. For this purpose, the evaluation unit 14 calculates the threshold values ​​of the received signals from the receivers 12' to generate a binary switching signal. The evaluation unit 14 generates the switching signal. The evaluation unit 14 has a redundant design. The switching signal is output via a switching output 19.

[0060] The Figures 4 and 5Figure 1 shows an embodiment of a sensor arrangement 1, which has two light curtains 10 by means of which opposite longitudinal sides of a conveyor belt 2 are protected. The light curtains 10 are oriented such that their beam axes, which span the protective field 7, lie in a vertical plane perpendicular to the conveying surface 2a of the conveyor belt 2.

[0061] In each light curtain 10, a binary switching signal is generated depending on which of the beam axes are interrupted by object interference. The switching states of this signal indicate whether or not a hazardous object interference has occurred. These switching signals are output to the safety controller 8. The safety controller 8 generates the safety signal by means of an OR gate; that is, a safety signal that stops the conveyor belt 2 is generated if a hazardous object interference is detected in at least one light curtain 10.

[0062] In the present case, a switching signal with the switching state "dangerous object interference" is generated in a light curtain 10 when one or the lowest beam axes are interrupted, since this detects the case when a person P wants to crawl under the protective field 7 of the light curtain 10 onto the conveying surface 2a of the conveyor belt 2.

[0063] Furthermore, a switching signal with the switching state "dangerous object interference" is generated in a light curtain 10 when one of the uppermost beam axes or axes is interrupted, as this detects the case when a person P wants to climb over the light curtain 10 onto the conveyor surface 2a.

[0064] In both cases, the switching signal only assumes the switching state "dangerous object interference" when the corresponding beam axes are interrupted for a certain minimum time. This takes into account that a person P always needs a certain amount of time to reach the conveying surface 2a of the conveyor belt 2.

[0065] However, it works, as in Figure 5 If a person P is shown in the area of ​​the middle beam axes through the light curtain 10, this is considered in the light curtain 10 as a non-hazardous object intervention, since the person P reaches through the protective field 7 to pick up or process objects 4.

[0066] The distinction as to whether a beam axis of a light curtain 10 forms a top, middle or bottom beam axis in the sense of the aforementioned evaluation can be determined by a parameterization process. Reference symbol list

[0067] (1) Sensor assembly (2) Conveyor belt (2a) Conveyor surface (3) Processing station (4) Object (5) Wall (6) Sensor (6a) Sensor component (6b) Evaluation unit (7) Protective field (8) Safety controller (9) Area distance sensor (10) Light curtain (11) Transmitter (11') Transmitter (11a) Transmitting light beam (11b) Receiving light beam (12) Receiver (12') Receiver (13) Object (14) Evaluation unit (15) Measuring head (16) Base (17) Housing (18) Window (19) Switching output (20) Transmitter unit (21) Receiver unit (22) Light beam PPerson

Claims

1. Sensor arrangement (1) for monitoring a danger zone on a work equipment with at least one sensor (6), which is designed to monitor a protective field (7), whereby the protective field (7) monitors lateral access to the work equipment, characterised in that a control and evaluation unit is provided, by means of which a distinction is made between dangerous and non-dangerous object intrusions by objects in the protective field (7) is carried out by means of a spatially resolved and, if necessary, also temporally resolved analysis of the object intrusions, and that the control and evaluation unit only generates a safety signal if there is a hazardous object intrusion, regardless of whether the object is a safety-critical object or a non-safety-critical object.

2. Sensor arrangement (1) according to claim 1, characterised in that said at least one sensor (6) can be used to determine in which areas of the protective field (7) an object intrusion occurs, and that the control and evaluation unit classifies whether a dangerous or non-dangerous object intrusion occurs depending on the areas.

3. Sensor arrangement (1) according to one of claims 1 or 2, characterised in that the control and evaluation unit monitors the time of object interference.

4. Sensor arrangement (1) according to claim 3, characterised in that object interference is only permitted at specified times and that, if inadmissible object interference is detected, the control and evaluation unit generates the safety signal.

5. Sensor arrangement (1) according to one of claims 1 to 4, characterised in that said at least one sensor (6) is a safety sensor.

6. Sensor arrangement (1) according to claim 5, characterised in that the control and evaluation unit is integrated in said at least one sensor (6), or that the control and evaluation unit is a safety control (8).

7. Sensor arrangement (1) according to one of claims 1-6, characterised in that said at least one sensor (6) is an optical sensor or a radar sensor.

8. Sensor arrangement (1) according to claim 7, characterised in that said at least one sensor (6) is an area distance sensor (9) or a light curtain (10).

9. Sensor arrangement (1) according to one of claims 1 to 8, characterised in that the safety signal is a switch-off command for the work equipment.

10. Sensor arrangement (1) according to one of claims 1 to 9, characterised in that the work equipment is a conveyor unit which is secured on opposite sides by a sensor (6) in each case, wherein the protective fields (7) protrude upwards above a conveyor surface (2a) of the conveyor unit.

11. Sensor arrangement (1) according to claim 10, characterised in that the sensors (6) are each formed by a light curtain (10) forming a number of beam axes, wherein the control and evaluation unit registers which of the beam axes are interrupted when an object interferes with them and generates the safety signal depending on this.

12. Sensor arrangement (1) according to claim 11, characterised in that the interruption of the lowest beam axis or beam axes of a light curtain (10) is evaluated in the control and evaluation unit as a dangerous object intrusion.

13. Sensor arrangement (1) according to one of claims 11 or 12, characterised in that the interruption of the uppermost beam axis or beam axes of a light curtain (10) is evaluated in the control and evaluation unit as a dangerous object intrusion.

14. Sensor arrangement (1) according to one of claims 12 or 13, characterised in that a safety signal is only generated if the uppermost and / or lowermost beam axes are interrupted for a specified minimum time.

15. Method for monitoring a danger zone on a work equipment by means of a sensor arrangement (1) with at least one sensor (6), which is designed to monitor a protective field (7), wherein the protective field (7) is used to monitor lateral access to the work equipment, characterised in that a control and evaluation unit is provided, by means of which a distinction is made between hazardous and non-hazardous object intrusions of objects in the protective field (7) is carried out by means of a spatially resolved and, if necessary, also time-resolved analysis of the object intrusions, and that the control and evaluation unit only generates a safety signal if a hazardous object intrusion is present, regardless of whether the object is a safety-critical object or a non-safety-critical object.