OPTICAL SENSOR

Description

[0001] The invention relates to an optical sensor and a method for operating an optical sensor.

[0002] Such optical sensors are generally used to detect objects in a monitored area. For example, such an optical sensor can be designed as a light curtain.

[0003] Such a light curtain is known, for example, from DE 10 2008 050 943 A1. The light curtain serves to monitor objects within a monitored area. In particular, the light curtain is designed as a safety light curtain, which is used in the field of safety technology for monitoring hazardous areas. The light curtain comprises an arrangement of transmitters housed in the casing of a transmitter unit. Furthermore, an arrangement of receivers is provided, housed in the casing of a receiver unit. The transmitter and receiver units are arranged at opposite edges of the monitored area. When the monitored area is unobstructed, the light beams emitted by a transmitter are directed onto an associated receiver. The transmitter and the associated receiver form a beam axis.For object detection, the evaluation unit analyzes the received signals from the receivers and, based on this analysis, generates a binary switching signal as an object detection signal. The switching states of this signal indicate whether an object is within the monitored area or not. An object interference occurs when at least one beam axis is interrupted by an object.

[0004] For use in safety-relevant applications, the optical sensor must meet the applicable normative requirements, i.e., the optical sensor must meet a required level of safety and have a corresponding fail-safe design.

[0005] This is typically achieved by having the optical sensor's evaluation unit have two independent processors that cyclically test and monitor themselves and each other. Such a safety concept is undesirably complex, particularly due to the cyclical testing of the processors. Furthermore, the processors have CPUs and memory units such as RAM and / or flash memory, meaning these components are duplicated in the redundant computer architecture, resulting in an undesirably high hardware cost.

[0006] DE 20 2021 100 816 U1 relates to an optoelectronic safety device comprising a light transmitter for emitting transmitted light beams into a monitored area, a light receiver for generating received signals from received light beams originating from reflections of the transmitted light beams off at least one object in the monitored area, and an evaluation unit for evaluating the received signals and outputting a safety signal based on the received signals. The evaluation unit includes a multi-core processor with at least two CPUs, wherein the multi-core processor is not a dedicated safety component and the evaluation is performed redundantly on both CPUs of the multi-core processor. The evaluation unit includes a watchdog controller that monitors the function of the multi-core processor, and the watchdog controller can independently cause the evaluation unit to output the safety signal.

[0007] German patent application DE 10 2016 210 984 A1 describes a method for operating a motor vehicle control unit. A status query is transmitted via a watchdog unit to a first control unit, which runs on the first processing core of a multi-core processor. A status response is determined by the first control unit based on the status query. An error is detected by the watchdog unit based on the status response.

[0008] DE 10 2008 050 943 A1 relates to an optical sensor for detecting objects within a protective field. The optical sensor comprises a light-emitting transmitter and a light-receiving receiver. The protective field is monitored by means of the light beams. The optical sensor includes an evaluation unit in which the received signals from the at least one receiver are evaluated and an object notification is generated when an object enters the protective field. According to the invention, means for detecting the direction of movement of objects are provided. The parameterization and / or the operating state of the optical sensor can be predefined depending on the direction of movement of objects.

[0009] The invention is based on the objective of providing an optical sensor of the type mentioned above, which can be used in safety-related applications with minimal design effort.

[0010] To solve this problem, the features of independent claims 1 and 15 are provided. Advantageous embodiments and expedient further developments of the invention are described in the dependent claims.

[0011] The invention relates to a method for operating an optical sensor for detecting objects in a monitoring area, comprising at least one light-emitting transmitter and at least one light-receiving receiver. In an evaluation unit, the receiver's received signals are evaluated in a fail-safe manner. Based on this evaluation, a reliable output signal in the form of an object detection signal is generated and output via an interface. The evaluation unit has a multi-core processor with at least two processing cores, wherein the receiver's received signals are fed to the processing cores and evaluated redundantly. The evaluation unit includes a watchdog controller, which monitors the functions of the multi-core processor. A redundant arrangement of safety-related interface modules is provided, through which the object detection signal can be output to an external unit.Two interface modules are available, with each interface module being connected to a computing core.

[0012] The optical sensor according to the invention can be designed as a light curtain. The light curtain comprises an arrangement of transmitters, which are advantageously integrated in a transmitter unit. Furthermore, the light curtain advantageously comprises a receiver unit in which an arrangement of receivers is arranged. The transmitter unit and the receiver unit are arranged at opposite edges of the monitoring area. Each transmitter is advantageously assigned a receiver to form a beam axis such that, with a clear monitoring area, the light beams of a transmitter are guided unhindered to the assigned receiver of the respective beam axis. Objects in the monitoring area are detected by the fact that at least the light beams of one beam axis are interrupted.

[0013] In principle, the optical sensor can also be designed as a reflective light curtain. In this case, the transmitters and receivers are housed in a single transmitter / receiver unit located at one edge of the monitored area. At the opposite edge of the monitored area is a reflector, which forms another component of the light curtain. With the monitored area clear, the light beams from each transmitter are directed to the reflector and from there reflected back to their corresponding receiver.

[0014] Furthermore, the optical sensor can be designed as a light barrier or a reflective light barrier. These optical sensors only have a transmitter and a receiver.

[0015] The optical sensor acts as a safety sensor, which is used, for example, to monitor a hazardous area within a system. The system is only authorized to operate if the optical sensor generates an object detection signal indicating that the hazardous area is clear.

[0016] The optical sensor according to the invention provides a structurally simple safety structure that meets the normative requirements for use in the field of safety technology.

[0017] The evaluation unit's multi-core processor has several processing cores into which the received signals from the receiver unit are read directly, i.e., without the use of additional processors. These processing cores then evaluate the received signals to generate the object detection signal as an output signal. Due to the evaluation unit's fail-safe design, it generates reliable, i.e., error-free, output signals.

[0018] The key point here is that the multi-core processor is not, and does not need to be, a safety component; that is, the multi-core processor with its processing cores does not inherently possess a fail-safe design. The processing cores of the multi-core processor can therefore have a simple architecture. Furthermore, cyclical mutual verification of the processing cores is not necessary.

[0019] The required level of security for use in security technology is achieved with the help of the watchdog controller, which monitors the processing cores of the multi-core processor.

[0020] Advantageously, the watchdog controller performs tests to check the processing cores of the multi-core processor.

[0021] In particular, the tests include a clock comparison, an activity test, the generation of tasks for computing cores and the verification of corresponding task results, as well as the monitoring of voltages.

[0022] Furthermore, the watchdog controller initiates self-tests of the processing cores of the multi-core processor.

[0023] This ensures a comprehensive test of the processing cores of the multi-core processor, whereby errors in the processing cores can be detected.

[0024] Generally, a fault message can be generated when errors are detected in the multi-core processor. Advantageously, in the event of a fault, the optical sensor is also deactivated or put into a safe state in which it outputs a corresponding safety signal.

[0025] According to a constructively advantageous variant, the multi-core processor is designed as part of a SoC (System on a Chip), and the watchdog controller is not part of the SoC (System on a Chip).

[0026] The watchdog controller and the multi-core processor thus form separate hardware units.

[0027] The multi-core processor and the watchdog controller are conveniently integrated into different housings.

[0028] This achieves a spatial separation of the watchdog controller and the multi-core processor.

[0029] According to an alternative design variant, the watchdog controller is formed by a processing core of the multi-core processor.

[0030] In this case, the watchdog controller is part of the multi-core processor, resulting in a particularly compact design for the evaluation unit of the optical sensor.

[0031] Generally, the processing cores can be in the form of CPUs or DSPs.

[0032] The watchdog controller advantageously communicates with the processing cores of the multi-core processor via serial interfaces or parallel interfaces.

[0033] The serial interface can be, for example, a bus. The parallel interface can also be a bus system. Triggering the watchdog controller is generally possible via the bus system, particularly to initiate tests of the processing cores.

[0034] According to a particularly advantageous embodiment, the output of the output signals, i.e. the object detection signals, is controlled by means of the watchdog controller.

[0035] The watchdog controller can use this as a criterion for the error-free functioning of the computing cores to check whether they generate the same output signals and only then output them to an external unit.

[0036] The watchdog controller advantageously controls the output of the object detection signal.

[0037] A particularly advantageous feature of the watchdog controller is that it uses one or both of its processing cores to form a logic channel for outputting signals. If an error occurs, the output of these signals is either blocked or an output signal is generated to bring an external unit, such as a controller for a system monitored by an optical sensor, into a safe state.

[0038] In the simplest case, the watchdog controller only monitors one processing core and simultaneously serves as a logical output channel for outputting the output signals.

[0039] Particularly advantageous is the watchdog controller with both or at least two processing cores forming a logical channel through which output signals are sent, thus realizing a multi-channel output structure.

[0040] According to the invention, a redundant arrangement of safety-related interface modules is provided, via which output signals can be sent to an external unit.

[0041] There are two interface modules, each of which is connected to a computing core.

[0042] The redundant interface modules are thus adapted to the redundant structure of the multi-core processor, whereby one processing core always advantageously controls one interface module.

[0043] A safety-oriented interface module is a fail-safe or error-tested interface module. For example, data read via such an interface module can be read back into the associated processing core to verify that the interface module is functioning correctly.

[0044] Furthermore, data transmitted via such interface modules can be secured with checksums or similar methods.

[0045] According to an advantageous embodiment of the invention, the multi-core processor has more than two processing cores. The output signals, i.e., object detection signals, are generated in two processing cores. The additional processing core(s) control and / or manage the communication with an external unit.

[0046] The multi-core processor with its processing cores then has a division of labor structure such that a portion of the processing cores, preferably two, are exclusively responsible for evaluating the received signals. These processing cores then operate independently of other processing cores that manage and control communication with external units.

[0047] This results in increased cybersecurity, as the processing cores responsible for external communication can detect and prevent external manipulation. The processing cores responsible for evaluating the received signals are thus protected from external manipulation.

[0048] The registration process is explained below using the drawings. They show: Figure 1: Schematic representation of an embodiment of the optical sensor according to the invention in the form of a light curtain. Figure 2: Schematic representation of an embodiment of the optical sensor according to the invention in the form of a reflective light curtain. Figure 3: Exemplary embodiment of the evaluation unit of the optical sensor according to the invention.

[0049] Figure 1Figure 1 shows the basic structure of the optical sensor according to the invention in the form of a light curtain 1. The light curtain 1 comprises a transmitter unit 2, in whose housing 11 a series of light-beam-emitting transmitters 4 in the form of transmitting diodes is arranged. The transmitting diodes are formed by light-emitting diodes or the like. The light curtain 1 further comprises a receiver unit 5, in whose housing 11 a series of receiving receivers 6 in the form of receiving diodes is provided. The receiving diodes are formed by photo-PIN diodes or photodiodes. Alternatively, phototransistors can also be used.

[0050] The transmitter unit 2 and the receiver unit 5 are arranged at opposite edges of a monitoring area. When the monitoring area is clear, the light beams 3 emitted by each transmitter 4 strike an associated, opposite receiver 6. Each transmitter 4 and its associated receiver 6 form a beam axis. Transmitter operation is controlled and evaluated by a control unit 7 in the transmitter unit 2. Receiver operation is controlled by an evaluation unit 8 in the receiver unit 5. The transmitters 4 and receivers 6 of the individual beam axes are cyclically activated individually or sequentially by optical synchronization of the light curtain 1. The parallel light beams 3 of the beam axes monitor a protective field extending in a plane.

[0051] In the evaluation unit 8, the received signals from the receivers 6 are evaluated to generate a binary switching signal as an object detection signal. The first switching state corresponds to an object notification, the second switching state to a clear protective field.

[0052] The optical sensor in general, or more specifically the light curtain 1, forms a safety sensor for use in safety technology. For this purpose, the light curtain 1 has a fail-safe design. In particular, the evaluation unit 8 has a multi-channel, redundant design, for example, in the form of two computer units that cyclically monitor each other.

[0053] The optical sensor, i.e., the light curtain 1, can then be used in safety-related applications. In particular, the optical sensor is used for monitoring hazardous areas on a system. The object detection signal generated in the optical sensor, i.e., the light curtain 1, is output as a signal to the system's control unit via an output structure 9. The system is only enabled to operate if the object detection signal indicates a clear hazardous area.

[0054] Figure 2 Figure 1 shows an embodiment of an optical sensor in the form of a reflective light curtain 10. The reflective light curtain 10 differs from the light curtain 1 according to Figure 1. Figure 1This is achieved by integrating the transmitters 4 and receivers 6 in a common housing 11 and controlling them with a control and evaluation unit 12, which performs the functions of the evaluation unit 8 and the control unit 7 of the light curtain 1. In a clear monitoring area, the light beams 3 from the transmitters 4 strike a reflector 13 and are reflected to the assigned receiver 6.

[0055] In general, the optical sensor can also be designed as a light barrier. Then the arrangement according to Figure 1 only one transmitter 4 and one receiver 6.

[0056] Furthermore, the optical sensor can also be designed as a reflective light barrier 10. Then the arrangement according to Figure 2 only one transmitter 4 and one receiver 6.

[0057] Figure 3 shows an embodiment of the evaluation unit 8 of the optical sensor 1 according to the invention.

[0058] The evaluation unit 8 forms a safety function, which allows the optical sensor 1 to be used in safety-related applications.

[0059] Received signals generated in the receiver(s) 6 are fed to the evaluation unit 8 via lines 14 and 15. For the sake of simplicity, in Figure 3 Only one receiver 6 is shown.

[0060] The evaluation unit 8 has a multi-core processor 16 with several processing cores 17a, 17b. In this case, there are two processing cores 17a, 17b, each being a CPU. Alternatively, the processing cores 17a, 17b can be configured as DSPs.

[0061] The multi-core processor 16 is advantageously part of a SoC (System On a Chip).

[0062] The received signals from receiver 6 are fed to both processing cores 17a, 17b of the multi-core processor 16 via lines 14, 15.

[0063] The multi-core processor 16 is not a safety component, i.e. the computing cores 17a, 17b do not have a fault-safe design.

[0064] The required level of safety for use in the field of safety technology, i.e. the required fault tolerance of the evaluation unit 8, is achieved by a watchdog controller 18 assigned to the multi-core processor 16, which monitors the two computing cores 17a, 17b.

[0065] In the present case, the watchdog controller 18 is not part of the multi-core processor 16.

[0066] In particular, the multi-core processor 16 and the watchdog controller 18 can be integrated into different housings 11.

[0067] Alternatively, the watchdog controller 18 can be formed by a processing core of the multi-core processor 16.

[0068] The watchdog controller 18 is connected to the processing cores 17a and 17b via an interface 19, which can be a serial or parallel interface. The watchdog controller 18 communicates with the processing cores 17a and 17b via interface 19.

[0069] Each of the computing cores 17a, 17b is connected to an interface module 20a, 20b, which form the output structure 9 of the optical sensor.

[0070] Interface modules 20a and 20b are designed as safety-related interface modules. Interface modules 20a and 20b are connected to the watchdog controller 18 via control lines 21.

[0071] In accordance with the order Figure 3 The watchdog controller performs 18 tests to check the computing cores 17a, 17b of the multi-core processor 16.

[0072] The tests include a clock comparison, an activity test, the generation of tasks for computing cores 17a, 17b and the checking of corresponding task results, as well as the monitoring of voltages.

[0073] Furthermore, the watchdog controller initiates 18 self-tests of the computing cores 17a, 17b of the multi-core processor 16.

[0074] Furthermore, the watchdog controller 18 is used to influence the output of object detection signals or data derived therefrom.

[0075] In the present case, the watchdog controller 18 forms a logical channel for the output of the object detection signals with each of the processing cores 17a, 17b by alternating its connection to them.

[0076] The watchdog controller 18 controls and monitors the two-channel output of the output signals, i.e. object detection signals, via the interface modules 20a, 20b. Reference symbol list

[0077] (1) Light curtain (2) Transmitter unit (3) Light beam (4) Transmitter (5) Receiver unit (6) Receiver (7) Control unit (8) Evaluation unit (9) Output structure (10) Reflection light curtain (11) Housing (12) Control and evaluation unit (13) Reflector (14) Cable (15) Cable (16) Multi-core processor (17a) Processing core (17b) Processing core (18) Watchdog controller (19) Interface (20a) Interface module (20b) Interface module (21) Control cable

Claims

1. An optical sensor for detecting objects within a monitoring area, comprising at least one transmitter (4) emitting light beams (3), at least one receiver (6) receiving light beams (3), and comprising an evaluation unit (8) which is designed to evaluate the receiver's (6) received signals in a fault-tolerant manner and, depending on this evaluation, to generate a reliable output signal in the form of an object detection signal and to output it via an interface, wherein the evaluation unit (8) comprises a multi-core processor (16) with at least two processing cores (17a, 17b), wherein the received signals from the receiver (6) are fed to the processing cores (17a, 17b) and evaluated redundantly there, and wherein the evaluation unit (8) comprises a watchdog controller (18) by means of which the functions of the multi-core processor (16) are monitored, characterised in that a redundant arrangement of safety-related interface modules (20a, 20b) is provided, via which the object detection signal can be output to an external unit, wherein two interface modules (20a, 20b) are provided, and wherein one interface module (20a, 20b) is connected to a processing core (17a, 17b).

2. An optical sensor according to claim 1, characterised in that the watchdog controller (18) performs tests to monitor the processing cores (17a, 17b) of the multi-core processor (16).

3. An optical sensor according to claim 2, characterised in that the tests comprise a clock comparison, an activity test, the generation of tasks for the processing cores (17a, 17b) and the verification of corresponding task results, as well as the monitoring of voltages.

4. An optical sensor according to any one of claims 1 to 3, characterised in that the watchdog controller (18) initiates self-tests of the processing cores (17a, 17b) of the multi-core processor (16).

5. An optical sensor according to any one of claims 1 to 4, characterised in that the multi-core processor (16) is configured as part of an SoC (System on a Chip), and in that the watchdog controller (18) is not part of the SoC.

6. An optical sensor according to claim 5, characterised in that the multi-core processor (16) and the watchdog controller (18) are integrated in different housings (11).

7. An optical sensor according to any one of claims 1 to 4, characterised in that the watchdog controller (18) is formed by a processing core (17a, 17b) of the multi-core processor (16).

8. An optical sensor according to any one of claims 1 to 7, characterised in that the watchdog controller (18) communicates with the processing cores (17a, 17b) of the multi-core processor (16) via a serial interface (19) or a parallel interface (19).

9. An optical sensor according to any one of claims 1 to 8, characterised in that the watchdog controller (18) controls the output of the object detection signal.

10. An optical sensor according to claim 9, characterised in that the watchdog controller (18) forms a logical channel with one or both processing cores (17a, 17b) for outputting the object detection signal.

11. An optical sensor according to any one of claims 1 to 10, characterised in that the multi-core processor (16) comprises more than two processing cores (17a, 17b), wherein the object detection signal is generated in two processing cores (17a, 17b), and wherein the one or more further processing cores control and / or monitor communication with an external unit.

12. An optical sensor according to any one of claims 1 to 11, characterised in that the processing cores (17a, 17b) are in the form of CPUs or DSPs.

13. An optical sensor according to any one of claims 1 to 12, characterised in that it is a through-beam sensor or a reflective sensor.

14. An optical sensor according to any one of claims 1 to 13, characterised in that it is a light curtain (1) or a reflective light curtain (10).

15. A method for operating an optical sensor for detecting objects in a monitoring area, comprising at least one transmitter (4) emitting light beams (3), at least one receiver (6) receiving light beams (3), and comprising an evaluation unit (8) which is designed to evaluate the receiver's (6) received signals in a fault-tolerant manner and, depending on this evaluation, to generate a reliable output signal in the form of an object detection signal and to output it via an interface, wherein the evaluation unit (8) comprises a multi-core processor (16) with at least two processing cores (17a, 17b), wherein the received signals from the receiver (6) are fed to the processing cores (17a, 17b) and evaluated redundantly there, and wherein the evaluation unit (8) comprises a watchdog controller (18) by means of which the functions of the multi-core processor (16) are monitored, characterised in that a redundant arrangement of safety-related interface modules (20a, 20b) is provided, via which the object detection signal can be output to an external unit, wherein two interface modules (20a, 20b) are provided, and wherein one interface module (20a, 20b) is connected to a processing core (17a, 17b).