Monitoring device and method for monitoring an opening

Abstract

The invention relates to a monitoring device and a method for monitoring an opening, in particular to a monitoring device for monitoring an opening, through which objects are conveyed by means of a transport mechanism, the monitoring device having a light curtain, which comprises an emitter array with a plurality of emitters of an emission beam and a receiver array with a plurality of receivers of a reception beam, the receivers recognizing an interruption of the beam and providing a signal, the light curtain being arranged at the opening such that the beam extends orthogonally to a transport plane of the transport mechanism, the monitoring device further having a scanning mechanism, which is designed to scan the signals of the receivers of the light curtain in time- successive scanning steps and to provide the signals as signal sequences, respectively, the monitoring device further having a control unit with a safety program, the control unit being designed to emit a shutdown signal in order to prevent a hazardous situation, an object recognition system being arranged in front of the light curtain against the transport direction and being used to recognize the objects and to derive parameters of the geometric shape of the objects from this recognition.

Description

Technical Field

[0001] This invention relates to a monitoring device for monitoring an opening through which an object is transported by means of a transport mechanism. The monitoring device has a light curtain comprising a transmitter array with multiple transmitters emitting light beams and a receiver array with multiple receivers receiving light beams. The receivers identify interruptions in the light beams and provide signals. The light curtain is arranged at the opening such that the light beams extend orthogonally to the transport plane of the transport mechanism. The monitoring device also has a scanning mechanism designed to scan the signals of the receivers of the light curtain in temporally continuous scanning steps and provide the signals as signal sequences respectively. The monitoring device also has a control unit with a safety program designed to issue a shut-off signal to prevent dangerous situations. Background Technology

[0002] Potentially hazardous machines, such as presses or fast-moving robotic arms, are located in a fixed, enclosed area. This could be due to supplying bags or boxes of any size to the enclosed area through an opening.

[0003] Methods and apparatus are known in industry for ensuring the entry or exit of specific permitted objects through openings into or out of hazardous areas, while preventing the entry or exit of unauthorized objects, especially personnel. Applications for this include, for example, access protection in automated manufacturing systems, protection of entry openings in production lines, protection of edge-rolling machines and palletizing systems, transportation technology, conveying and warehousing technology, the packaging industry, mechanical engineering, and the automotive industry.

[0004] It is known that such channels or openings are protected by gratings, in which rows of transmitting units emit light beams that are received by correspondingly arranged receiving units. An interruption of the light beam indicates the passage of an object. If an unauthorized object crosses the grating, safety functions are triggered, such as alarms, shutting down hazardous production machinery, or slowing down the production machinery. To allow objects to pass through protected channels or openings, a corresponding method and apparatus are proposed in document EP 2 108 879 B1. The disadvantage of the proposed method is that the allowed object must be trained in advance in a learning step, and the method disclosed in the prior art also has the disadvantage that the object must be aligned beforehand. A disadvantage of methods that do not utilize change steps is that the opening must have the exact same width as the allowed object so that personnel do not ignore the light curtain and pass through it alongside the allowed object. Summary of the Invention

[0005] The purpose of this invention is to provide a monitoring device as mentioned in the opening section, in which no object needs to be trained in advance, that is, for example, for a box, a box of any height, width and length can be passed through the opening and the object can be reliably detected.

[0006] Another objective of this invention is to enable boxes to rotate at any angle on a conveyor belt while still being reliably identifiable.

[0007] For the monitoring equipment described in the opening section, this objective is achieved by the following method: an object recognition system is arranged opposite to the transport direction in front of the light curtain, and the object recognition system is designed to identify objects and derive parameters for the geometry of the objects from the identification; the security procedure has a reconstruction algorithm designed to generate a matrix with a desired signal sequence from the parameters, the desired signal sequence being arranged in chronological order during the object's passage through the opening; the security procedure also has a comparator designed to compare the desired signal sequence of the matrix column-by-column with the signal sequence currently generated during the object's passage, where each column corresponds to a scan step; and the security procedure is designed to generate a shut-off signal when a deviation is found between the desired signal sequence and the currently acquired signal sequence.

[0008] The object is preferably a box, and the transport mechanism is preferably a series of belts or rollers that transport the box and allow it to pass through an opening monitored by a light curtain. The light curtain is configured such that the light beam extends vertically, thereby making the shape of the base of the box or other object recognizable to the light curtain. An image processing unit or object recognition system capable of recognizing, classifying, and analyzing objects moving on the belts is also mounted on the light curtain. The object recognition system or image processing system and the light curtain then send their data in real time to a functionally safe controller. Based on this information, the controller determines whether the object passing through the light curtain is, for example, rectangular. If an invalid target is identified, a safety response is initiated, such as potentially shutting down the actuators of a hazardous machine.

[0009] Security is further enhanced when the light curtain is also designed to transmit individual Boolean signals to the control unit. The security procedure is designed to generate a shutdown signal based on the individual Boolean signal. The security procedure is also designed to suppress the generation of the shutdown signal if the desired signal sequence matches the currently acquired signal sequence.

[0010] Because the light curtain now transmits an additional, security-oriented, separate Boolean signal to the security controller, this signal can already trigger a security response, such as shutting down the driver, once at least one beam is interrupted. However, the triggered security signal is suppressed precisely when the signal sequence from or from the light curtain's receiver matches the expected bits of the expected signal sequence of the generated matrix. This has the decisive advantage that the box is positioned such that its edges pass through the light curtain first without triggering a security response. It also has the decisive advantage that the currently acquired signal sequence does not need to be transmitted security-related; that is, the signal sequence can be transmitted according to standards. This, in turn, reduces the burden of security-oriented data transmission. This is because T-type telegraphs currently only transmit 13 bytes of security data per telegram.

[0011] If the monitoring equipment has an additional light curtain, the security of the monitoring equipment is improved again, wherein the additional light curtain is arranged at the opening so that the light beam extends parallel to the transport plane.

[0012] There is a hazard in the aforementioned monitoring equipment with only one light curtain, especially when the box is large and personnel are seated on one of the boxes. This keeps the base of the object square, and personnel could enter the protected area unnoticed. As a solution, it is proposed to use an additional light curtain in this case, with its beam horizontally oriented. This light curtain then transmits time-dependent sensor signals, time-dependent signal sequences, or time-dependent bit vectors to the fail-safe control unit in a similar manner.

[0013] In a method for monitoring an opening, an object is conveyed through the opening by means of a transport mechanism. A light beam is generated within or immediately adjacent to the opening using a light curtain. Multiple transmitters of an array emit the light beam towards multiple receivers of an array receive the light beam. In the event of a beam interruption, an interruption is identified and a signal is provided to the corresponding receiver. The light curtain operates within or immediately adjacent to the opening such that the light beam extends orthogonally to the transport plane of the transport mechanism. A scanning mechanism scans the signals of the receivers of the light curtain in temporally continuous scan steps and provides these signals as a signal sequence. To prevent dangerous situations, the light curtain is... A control unit with a safety procedure issues a shut-off signal. The object recognition system operates in the opposite direction of transport in front of a light curtain to identify objects and derives parameters for the object's geometry from this identification. A reconstruction algorithm generates a matrix with a desired signal sequence from the parameters, arranged chronologically as the object passes through the opening. A comparator then compares the desired signal sequence column-by-column with the signal sequence currently generated during the object's passage, synchronized with the scan step. A shut-off signal is generated when a deviation is found between the desired and currently acquired signal sequences. Using this method, objects can now be identified in a general manner; that is, in the case of boxes to be transported, the boxes can now have arbitrary height, width, and length. Furthermore, the boxes can be positioned on the conveyor belt at any angle of rotation.

[0014] The task of an object recognition system is, for example, to identify rectangular objects and determine the following parameters:

[0015] Midpoint (cx, cy),

[0016] Width and length (w, l), and

[0017] Orientation on the belt (α, rotation, and z-axis).

[0018] Another advantage is that the object recognition system does not necessarily need to be implemented with security technologies, as errors during parameter extraction or unidentified objects would subsequently trigger security responses. This is because the parameters are sent to a security-oriented application, such as the Siemens F-CPU device. The F-CPU device uses a corresponding program to reconstruct the expected behavior of the light curtain from the parameters. Specifically, a desired bit matrix is ​​generated, which presents the temporal order of the interruptions of the individual beams. As an object passes through the light curtain, this bit matrix is ​​compared column-by-column with the actually generated sensor data (e.g., fields of variables and Boolean types indicating which beams were interrupted). The sensor data also does not need to be detected or transmitted in a security-oriented manner; it is sufficient to detect and transmit it in a non-security-oriented way.

[0019] Even if the camera, image recognition, parameter transmission, and individual bits of the light curtain are implemented in a non-security-oriented manner, there will be no potentially dangerous failure of the entire system. This will be briefly illustrated with two examples.

[0020] Example 1: The object recognition system or image recognition fails completely and cannot recognize any objects. The object recognition system then also stops providing parameters to the F-CPU device and generates an empty bit matrix. Once an object enters the light curtain, subsequent comparisons fail. The Boolean signal of the light curtain is then not ignored, and a security response is initiated.

[0021] Example 2: The object recognition system or image recognition fails because it incorrectly identifies a non-box-shaped object (e.g., a person) as a box. In this case, the object recognition system or image recognition provides incorrect parameters to the F-CPU device. In the F-CPU device, a rectangular object is generated in a bit matrix. However, this bit matrix is ​​inconsistent with the actual object because it is assumed that the actual object is not rectangular. The comparison failure for at least one column results in the Boolean signal of the light curtain not being ignored. This triggers a security response.

[0022] Therefore, it is advantageous that while the light curtain continues to operate, individual Boolean signals are transmitted to the control unit, and a shutdown signal is generated based on these individual Boolean signals. Where the desired signal sequence matches the currently acquired signal sequence, the generation of the shutdown signal is suppressed. This advantageously eliminates the need for security-oriented transmission of the signal sequence. Attached Figure Description

[0023] The accompanying drawings illustrate embodiments of the present invention.

[0024] Figure 1 Showing the protected area according to existing technology,

[0025] Figure 2 The monitoring device according to the present invention is shown.

[0026] Figure 3 The matrix shown represents the generation of the desired signal sequence.

[0027] Figure 4 , Figure 5 and Figure 6 Exemplary signal sequences are shown respectively in the matrix, and

[0028] Figure 7 and Figure 8 This illustrates the principle when using a second light curtain. Detailed Implementation

[0029] according to Figure 1Robot RO is positioned within protected area SZ. Objects O1 and O2 can be transported into protected area SZ via opening 2 using transport mechanism TM along transport direction TR.

[0030] Because the robot RO is a potentially dangerous machine, it is essential to ensure that only objects O1 are allowed to pass through opening 2, and that personnel are absolutely prohibited from passing through. Therefore, a monitoring device with a light curtain is described below.

[0031] Figure 2 A monitoring device 100 is shown for monitoring opening 2, through which a first object O1 and a second object O2 are introduced by means of a transport mechanism TM. According to... Figure 1 The opening 2 is now fixed using a light curtain 1. The light curtain 1 is configured such that the light beam extends orthogonally to the transport plane TE of the transport mechanism TM. The light curtain 1 has for this purpose a transmitter array S consisting of multiple transmitters S1, ..., S11 emitting the light beam and a receiver array E consisting of multiple receivers E1, ..., E11 receiving the light beam. The receivers E1, ..., E11 detect interruptions in the light beam and generate a signal U.

[0032] The scanning mechanism 2 is connected to the light curtain 1 and is designed to scan the signals U of the receivers E1, ..., E11 of the light curtain 1 in time-continuous scanning steps Ti and provide these signals as signal sequences Si respectively.

[0033] Control unit 3, equipped with safety procedure AW, is designed to issue a shut-off signal AS to prevent dangerous situations, such as stopping the conveyor belt motor M. An object recognition system 4 is positioned in front of light curtain 1, designed to identify objects O1 and O2 and derive parameters P for the geometry of the objects from this identification. Safety procedure AW of control unit 3 has a reconstruction algorithm RA, designed to generate a matrix M with a desired signal sequence ESi from parameters P, the desired signal sequence being arranged in temporal order during the passage of objects O1 and O2 through opening 2. Safety procedure AW also has a comparator VM, designed to operate from column n to column n+1 (see...). Figures 5 to 7 The expected signal sequence ESi of matrix M is compared with the currently generated signal sequence Si during the passage of object O1, where each column n corresponds to... In a scan step Ti.

[0034] The safety procedure AW is designed to generate a shutdown signal AS when a deviation is found between the desired signal sequence Esi and the currently acquired signal sequence Si.

[0035] Figure 3The process of monitoring device 100 identifying and reconstructing, or subsequently comparing, is shown in chronological order. Object recognition system 4 identifies a first object O1 and sends parameters P, such as midpoint coordinates cx, cy, width w, length l, and rotation α about the Z-axis, which indicates, for example, how a box aligns with transport mechanism TM. The first object O1 now continues along transport direction TR to light curtain 1 or to opening 2. During the continued travel of the first object O1, in reconstruction step RS, control unit 3 first reconstructs the corners of object O1 from the generated parameters P in matrix M. Using the reconstructed corners, a range can be determined, and this range is filled in filling step FS using a desired signal sequence ESi, which, for example, is presented in chronological order during the passage of object O1 through opening 2. In the subsequent comparison step VS, the desired signal sequence ESi of matrix M is compared (or equal to) with the signal sequence Si currently generated during the passage of object O1, from column n to column n+1. For enhanced security, control unit 3 also issues a separate Boolean signal SS.

[0036] This offers the advantage that the signal sequence does not necessarily need to be transmitted using a security protocol. Thus, in one variant, a monitoring device 100 is provided, in which the signal sequence Si is transmitted from the light curtain to the security controller using a non-secure communication protocol, but a separate Boolean signal SS is also transmitted to the control unit 3, wherein the security program AW is designed to generate a shutdown signal AS based on the separate Boolean signal SS. Alternatively, a monitoring device 100 is provided, in which the signal sequence Si is transmitted from the light curtain to the security controller using a secure communication protocol.

[0037] Figure 4 The matrix M is shown, as it is generated by the reconstruction algorithm RA. The object recognition system 4 has transmitted parameters P for the square, and more precisely, this corresponds to a box standing on the conveyor belt rotated 45 degrees. Individual sensors or receivers E1, ..., E11 generate signals based on the generated matrix M as the box passes through the light curtain 1. Therefore, matrix M consists of the desired signal sequence ES1, ..., ES10.

[0038] Figure 5 The diagram illustrates the filling achieved by using the desired signal sequence ES1, ..., ES10 through the filling step FS.

[0039] Figure 6 The processing of the signal sequences ES1, ..., ES10 in time is shown for comparison of the desired signal sequence ESi with the actually generated signal sequence ESi.

[0040] Figure 7The special case of an exceptionally large box is described, because in this example, a third object O3 is sitting on the large box, a second object O2 is on top of it, and the third object O3 is a person, which could lead to a dangerous situation. To prevent this situation, the device F-CPU evaluates (√ or ×) an additional light curtain 10, which operates on the same principle as the first light curtain 1. Because light curtain 1 can only reliably identify the base of the large box, and because a person can be hidden on the large box, a second light curtain can be used to identify a person on the large box.

[0041] This also utilizes Figure 8 Presented symbolically.

Claims

1. A system having a monitoring device (100) and a transport mechanism (TM), wherein, The monitoring device (100) is designed to monitor the opening (2) through which objects (O1, O2, O3) are transported by means of the transport mechanism (TM). The monitoring device also has... Light curtain (1), the light curtain includes: A transmitter array (S) with multiple transmitters emitting beams, and A receiver array (E) having multiple receivers that receive a light beam, the receivers identifying interruptions in the light beam and providing a signal (U). A scanning mechanism designed to scan the signal (U) of the receiver of the light curtain (1) in temporally continuous scanning steps (Ti) and to provide the signal as a signal sequence (Si). A control unit (3) with a safety procedure (AW) is designed to issue a shutdown signal (AS) to prevent dangerous situations. An object recognition system (4) is arranged in front of the light curtain (1) opposite to the transport direction (TR), and the object recognition system is designed to identify the objects (O1, O2, O3) and derive parameters (P) for the geometry of the objects from the identification. The safety procedure (AW) includes a reconstruction algorithm (RA) designed to generate a matrix (M) from the parameters (P) having a desired signal sequence (ESi), the desired signal sequence being arranged in temporal order during the passage of the object (O1, O2, O3) through the opening (2). Its features are, The light curtain (1) is arranged at the opening (2) such that the light beam extends orthogonally to the transport plane (TE) of the transport mechanism (TM), thereby arranging the light curtain (1) so that the light beam extends vertically, enabling the shape of the object's base surface to be identified by the vertical extension of the light beam. The security procedure (AW) has a comparator (VM) designed to compare the desired signal sequence (ESi) of the matrix (M) column by column (n+1) with the currently generated signal sequence (Si) during the passage of the object (O1, O2, O3), where each column (n) corresponds to a scan step (Ti). The safety procedure (AW) is designed to generate the shutdown signal (AS) when the deviation between the desired signal sequence (ESi) and the currently acquired signal sequence (Si) is obtained.

2. The system according to claim 1, wherein, The light curtain (1) is also designed to transmit a single Boolean signal (SS) to the control unit (3), wherein the security program (AW) is designed to generate the shutdown signal (AS) based on the single Boolean signal (SS), wherein the security program (AW) is also designed to suppress the generation of the shutdown signal (AS) if the desired signal sequence (ESi) is consistent with the currently acquired signal sequence (Si).

3. The system according to claim 1 or 2, having Another light screen (10). in, The additional light curtain (10) is arranged at the opening (2) so that the light beam extends parallel to the transport plane (TE).

4. A method for monitoring an opening (2), wherein objects (O1, O2, O3) are conveyed through the opening by means of a transport mechanism (TM), wherein, A light beam is generated in or immediately in front of the opening (2) using a light curtain (1), wherein a plurality of transmitters of the transmitter array (S) emit the light beam toward a plurality of receivers of the receiver array (E) receive the light beam, wherein the interruption of the light beam is identified in the event of a light beam interruption, and wherein a signal (U) is provided to the corresponding receiver. The light curtain (1) operates within or immediately before the opening (2) such that the light beam extends orthogonally to the transport plane (TE) of the transport mechanism (TM). The signal (U) of the receiver of the light curtain (1) is scanned in time-continuous scan steps (Ti) by a scanning mechanism and the signal is provided as a signal sequence (Si). To prevent dangerous situations, a shutdown signal (AS) is issued via a control unit (3) with a safety procedure (AW). The object recognition system (4) operates in the opposite direction of transport (TR) in front of the light curtain (1) to recognize the objects (O1, O2, O3) and derive parameters (P) for the geometry of the objects from the recognition. In this process, a matrix (M) with a desired signal sequence (ESi) is generated from the parameters (P) using a reconstruction algorithm (RA). The desired signal sequence is arranged in temporal order as the object (O1, O2, O3) passes through the opening (2). Its features are, The light curtain (1) operates at the opening (2) such that the light beam extends orthogonally to the transport plane (TE) of the transport mechanism (TM), thereby arranging the light curtain (1) so that the light beam extends vertically, enabling the shape of the object's base surface to be identified by the vertical extension of the light beam. Then, a comparator (VM) is used to compare the desired signal sequence (ESi) with the currently generated signal sequence (Si) during the passage of the object (O1, O2, O3) from column (n) to column (n+1) of the matrix (M), wherein the column-by-column comparison is synchronized with the scan step (Ti), and the shut-off signal is generated when a deviation between the desired signal sequence (ESi) and the currently acquired signal sequence (Si) is obtained.

5. The method according to claim 4, wherein, The light curtain (1) also operates to transmit a single Boolean signal (SS) to the control unit (3) and generate the shutdown signal (AS) based on the single Boolean signal (SS), wherein the generation of the shutdown signal (AS) is suppressed if the desired signal sequence (ESi) is consistent with the currently acquired signal sequence (Si).

Images