Control system for a technical plant

Abstract

A control system according to the invention for a technical plant comprises at least one sensor for acquiring information, at least one actuator for issuing control commands, a processing unit, and a state database. During operation of the control system, the at least one sensor sends input signals, which are stored. The processing unit then retrieves the stored input signals, retrieves previously stored state information from the state database, calculates updated state information, stores the updated state information in the state database, calculates output signals, stores the calculated output signals, and sends the stored output signals to the at least one actuator. The state database is spatially separated from the processing unit.

Description

[0001] The invention relates to a control system for a technical plant, comprising at least one sensor for recording information, at least one actuator for issuing control commands, a computing unit and a state database.

[0002] Control systems, also known as programmable logic controllers (PLCs), play a central role in industrial automation. As digital electronic devices, control systems are used to manage machines and processes in industry, monitoring the state of input devices and controlling the state of output devices based on a user-defined program. Common control systems internally store state information. This enables the control system to operate deterministically and reliably, which is crucial in many industrial applications. Storing internal states allows the control system to perform specific tasks within defined timeframes, which is essential in time-critical applications.

[0003] The current trend is toward virtualized units, particularly in the form of soft PLCs or virtual PLC systems. This development is driven by the need for greater flexibility and scalability in modern production environments. Virtualized PLC systems offer advantages in terms of adaptability and easy integration into IT-supported infrastructures. A key challenge in virtualizing PLC systems is the lack of determinism. In a traditional hardware PLC, the specific hardware configuration ensures deterministic execution of control tasks. Virtualized environments, especially those running in containerized or cloud-based environments, struggle to maintain this determinism.Factors such as varying latency, network delays, and resource availability in a shared infrastructure can cause a virtual PLC to no longer operate reliably within a given timeframe.

[0004] The invention is based on the objective of further developing a control system for a technical plant.

[0005] The problem is solved according to the invention by a control system with the features specified in claim 1. Advantageous embodiments and further developments are the subject of the dependent claims.

[0006] A control system according to the invention for a technical plant comprises at least one sensor for acquiring information, at least one actuator for issuing control commands, a processing unit, and a state database. During operation of the control system, the at least one sensor sends input signals, which are stored. The processing unit then retrieves the stored input signals, retrieves previously stored state information from the state database, calculates updated state information, stores the updated state information in the state database, calculates output signals, stores the calculated output signals, and sends the stored output signals to the at least one actuator. The state database is spatially separated from the processing unit.

[0007] The control system according to the invention thus operates in a stateless manner, as the state information is stored externally, i.e., outside the computing unit. By outsourcing state management to external systems, in particular to the state database or distributed storage solutions, the control system can be designed to be more flexible and scalable in a virtualized environment. The control system according to the invention offers particular advantages in containerized environments. In a containerized infrastructure based on technologies such as Docker or Kubernetes, applications can be dynamically scaled, restarted, and moved. A stateless design enables the computing unit to operate independently of its location, since state information is held in a central, persistent state database.This not only increases flexibility but also improves recoverability, since in the event of a failure, a new instance of the computing unit can simply be started, which accesses the centrally stored states. The control system according to the invention exhibits deterministic behavior. The computing unit can be easily exchanged or replaced if necessary. The simultaneous use of two or more redundant computing units is also possible.

[0008] According to an advantageous embodiment of the invention, the updated state information calculated by the computing unit is stored exclusively in the state database.

[0009] In particular, no state information is permanently stored in the processing unit. The processing unit cyclically retrieves the previously stored state information from the state database and does not store the retrieved state information beyond one processing cycle after calculating the updated state information and the output signals.

[0010] According to an advantageous embodiment of the invention, the computing unit retrieves the previously stored state information from the state database using RDMA technology, and the computing unit transfers the calculated updated state information to the state database using RDMA technology.

[0011] Using RDMA technology, or Remote Direct Memory Access, efficient access to remote databases via a network is possible.

[0012] According to an advantageous embodiment of the invention, the computing unit calculates the updated state information based on previously retrieved input signals and based on previously retrieved state information.

[0013] According to an advantageous embodiment of the invention, the computing unit calculates the output signals based on previously retrieved input signals and based on previously retrieved state information.

[0014] According to an advantageous embodiment of the invention, the at least one sensor sends the input signals to the state database, and the input signals are stored in the state database, and the output signals are stored in the state database, and the stored output signals are sent from the state database to the at least one actuator.

[0015] The state database thus serves as storage for the input signals and contains a process image of the inputs. The state database also serves as storage for the output signals and contains a process image of the outputs. The processing unit therefore does not communicate directly with the at least one sensor or the at least one actuator. The processing unit communicates only with the state database. This decouples the processing unit from the at least one sensor and the at least one actuator.

[0016] According to an advantageous embodiment of the invention, the computing unit retrieves the stored input signals from the state database using RDMA technology, and the computing unit transmits the calculated output signals to the state database using RDMA technology.

[0017] Using RDMA technology, or Remote Direct Memory Access, efficient access to remote databases via a network is possible.

[0018] According to an advantageous embodiment of the invention, the control system comprises an input database and an output database. The at least one sensor sends the input signals to the input database, and the input signals are stored in the input database, and the output signals are stored in the output database, and the stored output signals are sent from the output database to the at least one actuator.

[0019] The input database thus serves as storage for the input signals and contains a process image of the inputs. The output database serves as storage for the output signals and contains a process image of the outputs. The processing unit therefore does not communicate directly with the at least one sensor or the at least one actuator. The processing unit only communicates with the state database, the input database, and the output database. This decouples the processing unit from the at least one sensor and the at least one actuator. The processing unit only reads from the input database. The processing unit only writes to the output database.

[0020] According to an advantageous embodiment of the invention, the input database is arranged spatially separate from the computing unit, and the output database is arranged spatially separate from the computing unit.

[0021] The input and output signals are thus stored externally, i.e., outside the processing unit. By outsourcing the process image of the inputs and the process image of the outputs to external systems, i.e., to the input database and the output database, the control system can be designed to be more flexible and scalable in a virtualized environment.

[0022] According to an advantageous embodiment of the invention, the computing unit retrieves the stored input signals from the input database using RDMA technology, and the computing unit transmits the calculated output signals to the output database using RDMA technology.

[0023] Using RDMA technology, or Remote Direct Memory Access, efficient access to remote databases via a network is possible.

[0024] According to an advantageous embodiment of the invention, the following operations are performed once each during a calculation cycle in the operation of the control system: • The processing unit retrieves the stored input signals, • The processing unit retrieves the previously stored state information from the state database, • The processing unit calculates the updated status information, • The calculated updated status information is stored in the status database, • The processing unit calculates the output signals, and • The calculated output signals are stored.

[0025] The described calculation cycle is repeated continuously. In each calculation cycle, the process image of the inputs is read, and the process image of the outputs is written. The input signals are sent and stored by the at least one sensor independently of the aforementioned calculation cycle. The output signals are sent to the at least one actuator independently of the aforementioned calculation cycle.

[0026] According to an advantageous embodiment of the invention, in a subsequent computing cycle, the state information retrieved in the previous computing cycle and the state information calculated in the previous computing cycle are overwritten in the computing unit.

[0027] The status information is therefore updated in every calculation cycle.

[0028] According to an advantageous embodiment of the invention, the computing unit has a coordinator which monitors the execution and synchronization of the operations performed by the computing unit during a computing cycle.

[0029] The coordinator ensures that deterministic processes are executed in a predefined order or at fixed times, while non-deterministic tasks can react flexibly to events.

[0030] According to an advantageous embodiment of the invention, the computing unit comprises a processor with a cache. During a computing cycle, before calculating the updated state information and before calculating the output signals, the computing unit loads the retrieved input signals, the retrieved state information, and the program code to be executed into the cache.

[0031] The invention is not limited to the combination of features stated in the claims. For a person skilled in the art, further meaningful combinations of claims and / or individual claim features and / or features of the description and / or the figures will become apparent, in particular from the problem statement and / or the problem arising from a comparison with the prior art.

[0032] The invention will now be explained in more detail with reference to the illustrations. The invention is not limited to the embodiments shown in the illustrations. The illustrations only depict the subject matter of the invention schematically. They show: Fig. 1: a control system for a technical plant according to a first embodiment and Fig. 2: a control system for a technical plant according to a second embodiment.

[0033] In Fig. Figure 1 schematically depicts a control system for a technical plant according to a first embodiment. The control system according to the first embodiment comprises several sensors 16 for acquiring information, of which only one sensor 16 is shown here. Such a sensor 16 generates, for example, binary or analog input signals. The control system also comprises several actuators 18 for issuing control commands, of which only one actuator 18 is shown here.

[0034] The control system according to the first embodiment further comprises a computing unit 10 and a state database 15. During operation of the control system, the computing unit 10 executes a control program that performs logical and arithmetic operations. For this purpose, the computing unit 10 has a processor with a cache. The computing unit 10 accesses the state database 15. The state database 15 stores state information about the technical system.

[0035] During operation of the control system, the sensors send 16 input signals to the state database 15. The input signals are stored in the state database 15. The processing unit 10 retrieves the stored input signals from the state database 15 using RDMA technology. The processing unit 10 also retrieves previously stored state information from the state database 15 using RDMA technology.

[0036] The processing unit 10 calculates updated status information based on previously retrieved input signals and previously retrieved status information. The processing unit 10 transmits the calculated updated status information to the status database 15 using RDMA technology. The calculated updated status information is stored in the status database 15.

[0037] The processing unit 10 calculates output signals based on previously retrieved input signals and state information. The processing unit 10 transmits the calculated output signals to the state database 15 using RDMA technology. The calculated output signals are stored in the state database 15. The stored output signals are then sent from the state database 15 to the actuators 18.

[0038] The state database 15 is located physically separate from the computing unit 10. Computing unit 10 accesses the state database 15 via a network, for example Ethernet.

[0039] The processing unit 10 operates cyclically. During a processing cycle in the operation of the control system, the following operations are each performed once: • The computing unit 10 retrieves the stored input signals from the state database 15. • The computing unit 10 retrieves the previously stored state information from the state database 15. • The computing unit 10 calculates the updated status information. • The computing unit 10 transfers the calculated updated status information to the status database 15. • The calculated updated status information is stored in the status database 15. • The processing unit 10 calculates the output signals. • The computing unit 10 transmits the calculated output signals to the state database 15 using RDMA technology. • The calculated output signals are stored in the state database 15.

[0040] In a subsequent calculation cycle, the state information retrieved in the previous calculation cycle is overwritten in processing unit 10. In a subsequent calculation cycle, the state information calculated in the previous calculation cycle is also overwritten in processing unit 10.

[0041] The input signals are sent from the sensors 16 to the state database 15 and stored there, independently of the aforementioned calculation cycle. The output signals are sent from the state database 15 to the actuators 18, also independently of the aforementioned calculation cycle.

[0042] In Fig.Figure 2 schematically depicts a control system for a technical plant according to a second embodiment. The control system according to the second embodiment comprises several sensors 16 for acquiring information, of which only one sensor 16 is shown here. Such a sensor 16 generates, for example, binary or analog input signals. The control system also comprises several actuators 18 for issuing control commands, of which only one actuator 18 is shown here.

[0043] The control system according to the second embodiment further comprises a computing unit 10 and a state database 15. During operation of the control system, the computing unit 10 executes a control program that performs logical and arithmetic operations. For this purpose, the computing unit 10 has a processor with a cache. The computing unit 10 accesses the state database 15. The state database 15 stores state information about the technical system.

[0044] The control system according to the second embodiment also includes an input database 12 and an output database 14. The input database 12 and the output database 14 are configured separately from each other and separately from the state database 15.

[0045] During operation of the control system, the sensors send 16 input signals to the input database 12. The input signals are stored in the input database 12. The processing unit 10 retrieves the stored input signals from the input database 12 using RDMA technology. The processing unit 10 also retrieves previously stored status information from the status database 15 using RDMA technology.

[0046] The processing unit 10 calculates updated status information based on previously retrieved input signals and previously retrieved status information. The processing unit 10 transmits the calculated updated status information to the status database 15 using RDMA technology. The calculated updated status information is stored in the status database 15.

[0047] The processing unit 10 calculates output signals based on previously retrieved input signals and status information. The processing unit 10 transmits the calculated output signals to the output database 14 using RDMA technology. The calculated output signals are stored in the output database 14. The stored output signals are then sent from the output database 14 to the actuators 18.

[0048] The state database 15 is located physically separate from the computing unit 10. Computing unit 10 accesses the state database 15 via a network, for example Ethernet.

[0049] The input database 12 and the output database 14 are also located physically separate from the computing unit 10. Computing unit 10 accesses the input database 12 and the output database 14 via a network, for example Ethernet.

[0050] The processing unit 10 operates cyclically. During a processing cycle in the operation of the control system, the following operations are each performed once: • The computing unit 10 retrieves the stored input signals from the input database 12. • The computing unit 10 retrieves the previously stored state information from the state database 15. • The computing unit 10 calculates the updated status information. • The computing unit 10 transfers the calculated updated status information to the status database 15. • The calculated updated status information is stored in the status database 15. • The processing unit 10 calculates the output signals. • The computing unit 10 transmits the calculated output signals to the output database 14 using RDMA technology. • The calculated output signals are stored in the output database 14.

[0051] In a subsequent calculation cycle, the state information retrieved in the previous calculation cycle is overwritten in processing unit 10. In a subsequent calculation cycle, the state information calculated in the previous calculation cycle is also overwritten in processing unit 10.

[0052] The input signals are sent from the sensors 16 to the input database 12 and stored there, independently of the aforementioned calculation cycle. The output signals are sent from the output database 14 to the actuators 18, also independently of the aforementioned calculation cycle. Reference symbol list 10 computing unit 12 Input database 14 Source database 15 Condition database 16 Sensor 18 Actuator

Claims

Control system for a technical plant, comprising at least one sensor (16) for acquiring information, at least one actuator (18) for issuing control commands, a computing unit (10) and a state database (15), characterized in that, during operation of the control system, the at least one sensor (16) sends input signals, and the input signals are stored, and the computing unit (10) retrieves the stored input signals, and the computing unit (10) retrieves previously stored state information from the state database (15), and the computing unit (10) calculates updated state information, and the calculated updated state information is stored in the state database (15), and the computing unit (10) calculates output signals, and the calculated output signals are stored, and the stored output signals are sent to the at least one actuator (18).and that the state database (15) is spatially separated from the computing unit (10). Control system according to claim 1, characterized in that the updated state information calculated by the computing unit (10) is stored exclusively in the state database (15). Control system according to one of the preceding claims, characterized in that the computing unit (10) retrieves the previously stored state information from the state database (15) using RDMA technology, and that the computing unit (10) transfers the calculated updated state information to the state database (15) using RDMA technology. Control system according to one of the preceding claims, characterized in that the computing unit (10) calculates the updated state information based on previously retrieved input signals and based on previously retrieved state information. Control system according to one of the preceding claims, characterized in that the computing unit (10) calculates the output signals based on previously retrieved input signals and based on previously retrieved state information. Control system according to one of the preceding claims, characterized in that the at least one sensor (16) sends the input signals to the state database (15), and that the input signals are stored in the state database (15), and that the output signals are stored in the state database (15), and that the stored output signals are sent from the state database (15) to the at least one actuator (18). Control system according to claim 6, characterized in that the computing unit (10) retrieves the stored input signals from the state database (15) using RDMA technology, and that the computing unit (10) transmits the calculated output signals to the state database (15) using RDMA technology. Control system according to one of claims 1 to 5, characterized in that the control system comprises an input database (12) and an output database (14), and that the at least one sensor (16) sends the input signals to the input database (12), and that the input signals are stored in the input database (12), and that the output signals are stored in the output database (14), and that the stored output signals are sent from the output database (14) to the at least one actuator (18). Control system according to claim 8, characterized in that the input database (12) is arranged spatially separate from the computing unit (10), and that the output database (14) is arranged spatially separate from the computing unit (10). Control system according to one of claims 8 to 9, characterized in that the computing unit (10) retrieves the stored input signals from the input database (12) using RDMA technology, and that the computing unit (10) transmits the calculated output signals to the output database (14) using RDMA technology. Control system according to one of the preceding claims, characterized in that during a computing cycle in the operation of the control system the following operations are performed once each: the computing unit (10) retrieves the stored input signals, the computing unit (10) retrieves the previously stored state information from the state database (15), the computing unit (10) calculates the updated state information, the calculated updated state information is stored in the state database (15), the computing unit (10) calculates the output signals, and the calculated output signals are stored. Control system according to claim 11, characterized in that in the computing unit (10) in a subsequent computing cycle the state information retrieved in the previous computing cycle and the state information calculated in the previous computing cycle are overwritten. Control system according to one of claims 11 to 12, characterized in that the computing unit (10) has a coordinator which monitors the execution and synchronization of the operations performed by the computing unit (10) during a computing cycle. Control system according to one of claims 11 to 13, characterized in that the computing unit (10) has a processor with a cache, and that the computing unit (10) loads the retrieved input signals, the retrieved state information and the program code to be executed into the cache during a computing cycle before calculating the updated state information and before calculating the output signals.

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