METHOD, SYSTEM AND GATEWAY FOR NETWORKING TIME-SENSITIVE FIELDBUSES

Description

Field of the invention

[0001] The invention relates to time-sensitive fieldbus systems, in particular to industrial fieldbus systems for controlling industrial systems. In particular, the invention relates to a method, a system, and a gateway for networking at least two time-sensitive fieldbuses. Background of the invention

[0002] Fieldbuses are used to connect various participant devices (e.g. field devices such as sensors, actuators, measuring probes, final control elements, etc. as well as controllers such as control or automation devices, programmable logic controllers, PLCs, etc.) in a system (e.g. industrial production plant, vehicle, building, etc.) for the purpose of communication. Communication takes place in particular, but not exclusively, between various field devices and a fieldbus controller, which controls and monitors the processes taking place in the system. A participant device can be a field device or a controller and, in particular, has an interface with the fieldbus.

[0003] The messages to be transmitted over a fieldbus (e.g., data blocks, data streams) are at least partially time-sensitive, meaning they have real-time requirements regarding transmission latency. For example, such time-sensitive data requires that a message sent by a subscriber device be reliably received by the fieldbus controller or another field device connected to the fieldbus within a predictable time period.

[0004] The data to be transmitted between fieldbus nodes includes not only value communication, such as measured values, control values, or instructions, but also event communication for the temporal coordination of machines and system components. For example, the coordination and synchronization of machine component movements is increasingly no longer carried out via mechanical devices (e.g., metal presses with rigidly coupled insertion and removal devices in the machine cycle, camshafts, gears, etc.), but via digital messages transmitted with real-time requirements via fieldbuses.

[0005] A fieldbus is assigned to a time domain in which all participant devices each have a timer (e.g. a clock). The timers of the participant devices are synchronized with each other within the time domain and thus have a common understanding of time. This means that all participant devices of a fieldbus can follow a defined fieldbus communication cycle and are coordinated with each other to carry out the appropriate actions at the right time. A participant device of the fieldbus acts as the master for the time domain, with the master's timer providing the time reference for the other participant devices in the time domain. The latter participant devices, which derive their time from the master within the time domain, are also referred to as slaves. The role of the time master in the fieldbus can be assumed by a fieldbus controller, but also by another participant device connected to the fieldbus.The fieldbus time master can synchronize its time base with another time base, for example, with the time master of another fieldbus or with a hierarchically superior time base. By synchronizing the masters of multiple fieldbuses with each other, a time domain can also encompass multiple fieldbuses. While synchronizing the time base aligns the "clocks," this does not necessarily mean that two fieldbuses within a time domain have the same communication cycles.

[0006] The first generation of fieldbuses was developed to replace the previously common parallel wiring of machine components using cable harnesses with digital transmission technology. Several, partly proprietary, fieldbus protocols were developed for this purpose. Later generations of fieldbuses are primarily based on the IEEE 802.3 Ethernet standard, with the Ethernet protocols being modified or extended to implement time-sensitive networks (TSNs).

[0007] Standards for real-time Ethernet protocols are being developed, for example, by the IEEE 802.1Q Task Group for TSN networks. A real-time scheduler (time-aware scheduler) is defined, for example, by the IEEE 802.1QBv standard. The scheduler enables communication within a network to be divided into fixed, periodically repeating communication cycles and, within these cycles, to define, reserve, or negotiate fixed time slots for the transmission of time-sensitive data. This enables clocked end-to-end transmission between two user devices.

[0008] Outside of the time slots designated for real-time transmission, non-time-sensitive data (best-effort data) can be transmitted using the well-known protocols for packet-switched transmission (e.g., Ethernet protocol). The real-time-supporting scheduler can establish guard bands to prevent transmissions of non-time-sensitive data packets from overlapping with the time slots reserved for real-time transmission.

[0009] Document US 2016 / 080533 A1 discloses a gateway that can transmit data between two networks of a vehicle. The first network is a time-sensitive FlexRay network and the second network is a vehicle Ethernet network.

[0010] Furthermore, TSN networks allow the transmission of non-time-sensitive data packets to be interrupted during real-time intervals and then resumed. This enables the coexistence of time-sensitive and non-time-sensitive communication in a TSN-enabled network.

[0011] With the increasing digitalization and networking of systems (e.g., an entire production site), there is a need to enable communication between fieldbuses as well as communication between a fieldbus and devices at a higher control level, process control level, operations control level, and / or corporate level. Networking affects both non-time-sensitive data and time-sensitive data.

[0012] Although most of the real-time protocols for fieldbuses in use today are based on Ethernet, despite this commonality, there are technical differences that make different fieldbus types incompatible or not fully compatible with each other. It may also happen that different generations of fieldbuses are used, for example, when parts of a plant are added, replaced, or modernized; fieldbuses of different generations are not necessarily fully compatible. Efforts are currently underway to specify universally applicable real-time protocols that will replace the many proprietary and mutually incompatible protocols for time-sensitive fieldbuses. However, their use will require the replacement or upgrade of existing fieldbus systems, which is often not economically viable.

[0013] Known solutions for time-sensitive communication between two or more fieldbuses assume that all connected fieldbuses have a uniform understanding of time, while also synchronizing all time offsets, durations, and / or start times of the fieldbus communication cycles. However, fieldbuses are often extensively configured at the beginning of a production process so that the machines and / or system components controlled by the fieldbus are optimally coordinated. However, adapting the cycle times of an existing fieldbus to newly added system components with additional fieldbuses would require reconfiguration of the existing processes controlled by the fieldbus.

[0014] There is therefore a need to network time-sensitive fieldbuses that are not fully compatible with each other. Summary of the invention

[0015] The object is achieved in particular by a method for networking a first time-sensitive fieldbus with a second time-sensitive fieldbus according to claim 1, by a system for networking at least two time-sensitive fieldbuses according to claim 8 and by a gateway for time synchronization and for networking at least two time-sensitive fieldbuses according to claim 12.

[0016] To solve this problem, a gateway is used that mediates communication between time-sensitive fieldbuses. Because the gateway supports the respective time domain of all connected fieldbuses, the fieldbuses can communicate with each other largely without aligning the time domains and, in particular, the communication cycle times defined within the fieldbuses. This applies to both time-sensitive and non-time-sensitive data.

[0017] One aspect of the present invention relates to a method for networking a first time-sensitive fieldbus with a second time-sensitive fieldbus, wherein the first time-sensitive fieldbus comprises a first subscriber device and has a first dedicated time domain. The second time-sensitive fieldbus comprises a second subscriber device and has a second dedicated time domain. The first time domain and the second time domain are frequency-synchronized. The first and second fieldbuses are connected to one another via a gateway. The method comprises storing a first subscriber device identifier in the memory of the gateway, wherein the first subscriber device identifier identifies a virtual image of the assigned first subscriber device of the first fieldbus.The method further comprises storing a second subscriber device identifier in the gateway's memory, wherein the second subscriber device identifier identifies a virtual image of the associated second subscriber device of the second fieldbus. Furthermore, the method comprises determining a first cycle time of the first fieldbus and a second cycle time of the second fieldbus by the gateway at a reference time, and determining a time offset between the first time domain and the second time domain by the gateway at the reference time.

[0018] Frequency synchronization can be achieved by synchronizing the clock frequencies in the time domains of the first and second fieldbuses. This type of frequency synchronization allows the first and second fieldbuses, or the first and second time domains, to have differently defined times, but the time offset is time-invariant, i.e., constant over time. By synchronizing only the frequencies in the first and second time domains, the time regimes (i.e., the valid time of a time domain) in the fieldbuses can remain largely unaffected.

[0019] In particular, this avoids a hard time jump that could otherwise occur in one or both fieldbuses when aligning the first and second fieldbus times. The frequency alignment can take place over a period of time that does not affect the operation of the processes running in the fieldbuses.

[0020] The first and second fieldbuses can be connected via the gateway by connecting the gateway as a subscriber device to the first or second fieldbus, respectively. For this purpose, a network connection with a corresponding interface to the respective fieldbus can be provided, for example. For communication between a fieldbus and one or more subscriber devices of another fieldbus, the gateway can provide virtual images of subscriber devices. The virtual images of the subscriber devices of the other fieldbus can be set up as subscriber devices of its own fieldbus. For example, the virtual image of the first subscriber device in the first fieldbus can be set up as a subscriber device in the second fieldbus, and the virtual image of the second subscriber device in the second fieldbus can be set up as a subscriber device in the first fieldbus.

[0021] The virtual images can each be identified via subscriber device identifiers. For example, the first subscriber device in the first fieldbus can send a message to the virtual image of the second subscriber device, using the subscriber device identifier of the virtual image of the second subscriber device. In embodiments of the invention, the subscriber device identifier can be embodied as a network address, for example as a Medium Access Control (MAC) address or as an Internet Protocol (IP) address or as an address of another network protocol or as an address or identifier in a network protocol layer. The gateway can also be configured to forward messages received via a virtual image of a subscriber device to the assigned subscriber device. For this purpose, it can use, for example, an identifier of the assigned subscriber device.Furthermore, the gateway can receive response messages from the assigned subscriber device via a virtual image and forward them to the subscriber device in the other fieldbus.

[0022] By determining the first cycle time of the first fieldbus and the second cycle time of the second fieldbus at a reference time and by determining a time offset between the first time domain and the second time domain at the reference time, the gateway can act as an intermediary or "interpreter" between the time regimes of the fieldbuses.

[0023] For example, the gateway can receive a message from a subscriber device in the second fieldbus via the virtual image of the first subscriber device. The message can, for example, be non-time-sensitive data (so-called best-effort data) that is to be sent from the subscriber device in the second fieldbus to the first subscriber device in the first fieldbus. Since the virtual image of the first subscriber device behaves like a subscriber device in the second fieldbus, it can take the cycle time of the second fieldbus into account when receiving the message. Furthermore, time slots can be reserved in the second fieldbus for the transmission of time-sensitive data. These reserved time slots can be taken into account in such a way that the non-time-sensitive data is received outside of these time slots.The gateway can now forward the message taking into account the cycle time of the first fieldbus and the reserved time slots for transmitting time-sensitive data in the first fieldbus. For forwarding outside of the reserved time slots in the first fieldbus, the gateway can also temporarily store the non-time-sensitive data.

[0024] The first subscriber device in the first fieldbus can send a response to the received message in the opposite direction via the assigned virtual image in the gateway to the subscriber device in the second fieldbus. In this case, the cycle times and the reserved time slots in the first and second fieldbus are taken into account, if necessary by temporarily storing the data in the gateway. Such an exchange can be useful if measured values, control commands, but also software updates or other operating data are to be transmitted in a non-time-critical manner between fieldbuses with different time domains. Configuration data, for example, for reserving corresponding cross-fieldbus time slots for transmitting time-sensitive data, can also be transmitted as non-time-sensitive communication.The virtual image of a subscriber device that is assigned to a subscriber device in one fieldbus forms a termination point for communication protocols in the other fieldbus and behaves for the subscriber devices in the other fieldbus like a subscriber device of that other fieldbus.

[0025] Using the virtual images of at least some of the subscriber devices of a fieldbus, the gateway can also support the transmission of time-sensitive data. For this purpose, the gateway can, for example, determine a temporal overlap between a first time slot set by the first fieldbus for communicating time-sensitive data in the first fieldbus and a second time slot set by the second fieldbus for communicating time-sensitive data in the second fieldbus. In some embodiments, the determination can be made by sending corresponding requests to subscriber devices of the first or second fieldbus, or by the gateway mediating the negotiation of such time slots and storing the mediated time slots and other communication parameters.

[0026] In further embodiments, the method further comprises the steps of receiving, by the gateway, a request from the second fieldbus for a time slot for transmitting time-sensitive data from the first subscriber device of the first fieldbus to the second subscriber device of the second fieldbus. Furthermore, the method may comprise forwarding the request to the first fieldbus. Furthermore, the gateway may receive a confirmation message from the first fieldbus and forward this confirmation message to the second fieldbus.

[0027] The request can originate from any participant device of the second fieldbus and be directed to another participant device in the first fieldbus.

[0028] For example, a subscriber device with a scheduler function in the second fieldbus can send a request to the first fieldbus. In the first and second fieldbus, at least one scheduler is responsible for defining the transmission cycles and / or for assigning, negotiating, allocating, setting up and / or managing the time slots for transmitting time-sensitive data. Such subscriber devices can be designed as real-time schedulers (time-aware schedulers) and implement the corresponding protocols and functions for this purpose, e.g. in accordance with the IEEE 802.1Q or 802.1Qbv standard. The request can be directed to a subscriber device of the first fieldbus with the function of a real-time scheduler, which can negotiate and assign time slots for communicating time-sensitive data for the first subscriber device in the first fieldbus.Since the gateway is also a participant device of the first fieldbus, embodiments can be such that the function as a real-time supporting scheduler for the first fieldbus is also assumed by the gateway. In this case, communication with the first fieldbus can take place within the gateway. Similarly, the gateway is also a participant device of the second fieldbus, and embodiments can be configured such that the gateway assumes the function as a real-time supporting scheduler for the second fieldbus. In some embodiments, the described communication of a request and an acknowledgment can thus take place exclusively within the gateway, since the gateway is a participant device of both the first and second fieldbus.In such cases, it is unnecessary, for example, to communicate the request from the second fieldbus to the first fieldbus and to communicate the confirmation message from the first fieldbus to the second fieldbus via the physical layers of the fieldbuses.

[0029] In some embodiments, the gateway may receive the request from the second fieldbus. To identify the subscriber devices that are to exchange the time-sensitive data, the request may contain an identifier of the data source and the data destination. For example, it may contain the first subscriber device identifier or another identifier that can be used in the second fieldbus to identify the first subscriber device. Furthermore, the request may contain the second subscriber device indicator or another identifier that identifies the second subscriber device or its virtual image.

[0030] In the opposite direction, the gateway receives an acknowledgment message from the first fieldbus. In some embodiments, the acknowledgment message can be sent by the real-time scheduler for the first fieldbus. The gateway then forwards the acknowledgment message to the second fieldbus, for example, to a subscriber device with a scheduler function, which sets up a time slot for the second subscriber device to transmit time-sensitive data.

[0031] The communication of the described request and confirmation can be conducted via a virtual image of a subscriber device in the first fieldbus, in particular a virtual image of a real-time supporting scheduler in the first fieldbus. The virtual image in the gateway can initially be identified via a corresponding subscriber device identifier in the second fieldbus. The virtual image then serves as a proxy for the actual real-time supporting scheduler in the first fieldbus.

[0032] In further embodiments, the request received (by the gateway) comprises a time specification of at least one point in time and / or at least one time interval. The time specification is related to the time domain of the second fieldbus. The method further comprises determining, by the gateway, the time specification from the received request related to the time domain of the first fieldbus, taking into account the time offset with respect to the reference point in time. The request forwarded by the gateway to the first fieldbus comprises the time specification related to the time domain of the first fieldbus.

[0033] Such a time specification can make the request more precise. For example, times and intervals can be communicated that are available for time-sensitive communication in the second fieldbus or that should be excluded. The request can have the character of a "command," in which case the second fieldbus must establish a time slot for time-sensitive communication according to the time specification, or it can have the character of a "negotiation basis," in which the second fieldbus can further specify the time specification.

[0034] In this case, the time information can be transmitted to the gateway by a subscriber device of the second fieldbus in relation to the time domain of the second fieldbus, whereby the gateway can convert the time information in relation to the first fieldbus.

[0035] The method can further comprise setting a first time slot for communicating time-sensitive data in the first fieldbus by the first fieldbus, based on the time specification from the request relative to the first time domain of the first fieldbus, and setting a second time slot for communicating time-sensitive data in the second fieldbus by the second fieldbus, based on the time specification relative to the second time domain of the second fieldbus. The first time slot is set by the first fieldbus and the second time slot is set by the second fieldbus in such a way that the first time slot of the first fieldbus and the second time slot of the second fieldbus overlap in time. Since the corresponding time specification in the first and second fieldbus is each present with respect to its own time regime, conversion of the time specification by subscriber devices of the first or second fieldbus is eliminated.Nevertheless, they can define the first and second time slots such that the time slots overlap in time. Setting the time slots in the first or second fieldbus can be performed by corresponding subscriber devices, for example, with the corresponding function as a real-time support scheduler. If this functionality occurs in the gateway, which in some embodiments can also be a subscriber device of the first or second fieldbus, the communication related to setting the time slots can take place at least partially within the gateway.

[0036] In further embodiments, the received confirmation message from the first fieldbus comprises a further time indication of at least one point in time and / or at least one time interval, wherein said further time indication is related to the time domain of the first fieldbus. The method further comprises determining, by the gateway, the further time indication from the received confirmation message related to the time domain of the second fieldbus, taking into account the time offset with respect to the reference point in time. The confirmation message forwarded to the second fieldbus comprises the further time indication related to the time domain of the second fieldbus, wherein the setting of the first time slot by the first fieldbus is based on said further time indication, and wherein the setting of the second time slot by the second fieldbus is based on said further time indication.In this way, not only is it possible for the request message to contain a time specification, but the confirmation message can also contain an additional time specification. For example, the first fieldbus can suggest different time specifications than those in the request or specify a previous time specification. The gateway converts the additional time specification with respect to the time regime of the respective fieldbus, so that no conversions need to be made in the fieldbuses. The described request to the first fieldbus and the described confirmation with exchange of time specifications can also be part of a more comprehensive protocol for establishing time slots for communicating time-sensitive data, with additional messages with time specifications being exchanged between the fieldbuses.

[0037] In further embodiments, the method further comprises receiving, by the gateway, time-sensitive data from the first user device of the first fieldbus, wherein the time-sensitive data includes the second user device indicator, during the overlap of the first time slot and the second time slot. The method further comprises determining, by the gateway, an identifier of the second user device based on the second user device identifier during the overlap of the first time slot and the second time slot. The received time-sensitive data is further forwarded by the gateway to the second user device during the overlap of the first time slot and the second time slot.

[0038] In such embodiments, the second subscriber device indicator serves to identify the second subscriber device for the first fieldbus. The first subscriber device of the first fieldbus can address the time-sensitive data to the virtual image of the second subscriber device, whereby the second subscriber device can be addressed as a subscriber device of the first fieldbus. The gateway then forwards the data to the assigned second subscriber device of the second fieldbus, using its identifier. For example, the identifiers can represent network addresses (MAC addresses or IP addresses), with the gateway exchanging the destination address of a physical data unit (MAC PDU, IP data packet).

[0039] The gateway receives, determines the identifier, and forwards the time-sensitive data during the temporal overlap of the first and second time slots. Such forwarding of the time-sensitive data can be achieved by the gateway providing a termination point for the physical layer on the second fieldbus side. The gateway can then receive the physical signals, demodulate them, and, if necessary, decode them (e.g., with regard to channel coding), so that the time-sensitive data is available as data bits at the top of the physical layer. In one example, the data can be forwarded in the so-called Medium Access (MAC) protocol layer via a so-called MAC bridge (e.g., according to the IEEE 802.1D standard). This allows, for example, the MAC protocol header to be read out for forwarding to the other fieldbus and modified with the identifier of the second subscriber device.Data can also be routed at a higher protocol layer than the MAC layer, with the gateway providing the appropriate protocol stack. Minor delays may result from signal and data processing in the gateway. However, since the first and second time slots are reserved for the transmission of time-sensitive data, and there is an overlap in both time slots, intermediate storage in queues can be largely avoided. The resulting delays can thus be kept predictable and manageable, ensuring that real-time transmission requirements are met.

[0040] In practice, it is possible that, in addition to the time offset between the first and second time domains, further temporal differences exist, e.g., with regard to different durations of the first and second time slots and the temporal position of the first and second time slots for the transmission of time-sensitive data. In an area where the first and second time slots overlap, time-sensitive data can be passed through the gateway between the fieldbuses. Outside the overlap area, time slots can still be reserved in the first or second fieldbus for the transmission of time-sensitive data. These time periods can, for example, be used independently of one another for the transmission of time-sensitive data within the fieldbuses.

[0041] To perform the aforementioned frequency synchronization of the first and second time domains, the gateway can have a first timer and a second timer. To frequency synchronize the two fieldbuses, for example, the first timer of the gateway can be synchronized as a slave with the first time domain of the first fieldbus. Furthermore, the second timer of the gateway can be synchronized as a slave with the second time domain of the second fieldbus. Then, initially, only the frequency of the first timer can be synchronized as a slave with the frequency of the second time domain of the second timer, and then the first timer can be set as the master for the first fieldbus in order to set the frequency (of the first fieldbus) to the frequency of the first timer.

[0042] Since the gateway has its own timers that are synchronized (e.g., exclusively) in frequency, the gateway knows the time defined in the first and second time domains and can, for example, coordinate the transmission of non-time-sensitive data in such a way that the time slots for transmitting time-sensitive data are not affected. Furthermore, after frequency synchronization, it is guaranteed that the time differences between the fieldbuses, while still present, are time-invariant and thus do not "run away." In the scenario described, the first fieldbus derives its time base from the second fieldbus, whereby setting the first timer as the master for the first fieldbus represents only a minor intervention in the time regime of the first fieldbus. For example, setting the frequency of the first timer can be done over a period of time that avoids a hard time jump.The first fieldbus can thus be synchronized during operation "under load".

[0043] A further aspect of the invention relates to a system for networking at least two time-sensitive fieldbuses. The system comprises a first time-sensitive fieldbus comprising a first subscriber device and having a first dedicated time domain. The system further comprises a second time-sensitive fieldbus comprising a second subscriber device and having a second dedicated time domain, wherein the first time domain and the second time domain are frequency-synchronized. Furthermore, the system comprises a gateway that connects the first and second fieldbuses to one another. The gateway comprises means for storing a first subscriber device identifier in the gateway's memory, wherein the first subscriber device identifier identifies a virtual image of the assigned first subscriber device of the first fieldbus.The gateway has means for storing in the gateway's memory a second subscriber device identifier, wherein the second subscriber device identifier identifies a virtual image of the associated second subscriber device of the second fieldbus. Furthermore, the gateway has means for determining a first cycle time of the first fieldbus and a second cycle time of the second fieldbus by the gateway at a reference time, as well as means for determining a time offset between the first time domain and the second time domain by the gateway at the reference time. In further embodiments, the system is configured to carry out the steps (e.g., all steps) of the method described above.

[0044] A further aspect of the invention relates to a gateway for networking a first time-sensitive fieldbus with a second time-sensitive fieldbus, wherein the first time-sensitive fieldbus comprises a first subscriber device and has a first dedicated time domain, and wherein the second time-sensitive fieldbus comprises a second subscriber device and has a second dedicated time domain, wherein the first time domain and the second time domain are frequency-synchronized.The gateway comprises means for connecting each of the first time-sensitive fieldbus and the second time-sensitive fieldbus to the gateway, means for storing a first subscriber device identifier in the gateway's memory, the first subscriber device identifier identifying a virtual image of the associated first subscriber device of the first fieldbus, and means for storing a second subscriber device identifier in the gateway's memory, the second subscriber device identifier identifying a virtual image of the associated second subscriber device of the second fieldbus. Furthermore, the gateway comprises means for determining a first cycle time of the first fieldbus and a second cycle time of the second fieldbus at a reference time, and means for determining a time offset between the first time domain and the second time domain at the reference time.

[0045] In further embodiments, the gateway further comprises means for receiving a request from the second fieldbus for a time slot for transmitting time-sensitive data from the first subscriber device of the first fieldbus to the second subscriber device of the second fieldbus. The gateway further comprises means for forwarding the request to the first fieldbus, as well as means for receiving an acknowledgment message from the first fieldbus and means for forwarding the acknowledgment message to the second fieldbus.

[0046] In further embodiments, the received request comprises a time specification of at least one point in time and / or at least one time interval, wherein the time specification is related to the time domain of the second fieldbus. The gateway has means for determining the time specification from the received request relative to the time domain of the first fieldbus, taking into account the time offset with respect to the reference point in time. The request forwarded to the first fieldbus comprises the time specification relative to the time domain of the first fieldbus.

[0047] In further embodiments, the gateway comprises means for determining a temporal overlap of a first time slot set by the first fieldbus for communicating time-sensitive data in the first fieldbus and a second time slot set by the second fieldbus for communicating time-sensitive data in the second fieldbus.The gateway further comprises means for receiving time-sensitive data from the first subscriber device of the first fieldbus, the time-sensitive data containing the second subscriber device indicator during the overlap of the first time slot and the second time slot, means for determining an identifier of the second subscriber device based on the second subscriber device identifier during the overlap of the first time slot and the second time slot, and means for forwarding the received time-sensitive data to the second subscriber device during the overlap of the first time slot and the second time slot.

[0048] The embodiments of the gateway thus comprise means for executing the method steps in the method described above, which are executed by the gateway mentioned therein. Short description of the drawings

[0049] In the following detailed description, aspects of the invention are described with reference to the drawings, wherein Fig. 1 shows a block diagram of a system with a first time-sensitive fieldbus and with a second time-sensitive fieldbus; Fig. 2 schematically shows a timing diagram of a first and second fieldbus and the transmission of non-time-sensitive data by the gateway; Fig. 3 schematically shows a detailed timing diagram of the cycle times defined for a first and second fieldbus; Fig. 4 schematically shows an example of a request protocol for time slots for the transmission of time-sensitive data between the first and second fieldbus and a protocol for the transmission of time-sensitive data between the first and second fieldbus; and Fig. 5 schematically shows a timing diagram of a first and second fieldbus and the transmission of time-sensitive data by the gateway. Detailed description

[0050] The following detailed description explains exemplary embodiments of the invention with reference to the above-mentioned figures. In this case, identical reference symbols in different figures describe the same device, the same method step, the same time unit, etc.

[0051] Fig. 1shows a block diagram of an exemplary system 1 with a first time-sensitive fieldbus 10 and a second time-sensitive fieldbus 20. The first fieldbus 10 and the second fieldbus 20 comprise, by way of example, the participant devices 12, 14a-c, and 22, 24a-c, respectively, wherein the participant devices 12, 22 are each controllers of the fieldbus, for example an automation device, a programmable logic controller, PLC, a node or another industrial controller, and the participant devices 14a-c, and 24a-c are field devices, for example I / O modules for sensors and / or actuators, which can measure or influence variables of a process automated by the fieldbus. The subscriber devices 12, 14a-c, or 22, 24a-c are communicatively connected to each other in the respective fieldbus 10, 20 via an interface, whereby the definition of the interface includes an interface protocol.

[0052] The subscriber devices 12, 14a-c of the first fieldbus 10 belong to a first time domain 16, whereby all subscriber devices 12, 14a-c have the same understanding of absolute time. For this purpose, each subscriber device 12, 14a-c has a timer which is Fig. 1 schematically symbolized by the face of a clock. Correspondingly, the subscriber devices 22, 24a-c of the second fieldbus 20 belong to a second time domain 26. In the fieldbuses 10 and 20, the fieldbus lines are connected to the field devices in a star configuration, starting from the controller 12, 22. In general, fieldbuses can also be formed by other topologies, e.g., tree topology, bus topology, ring topology, etc. It is also possible for the subscriber devices 12, 24a-c, or 22, 24a-c of a fieldbus 10, 20 to be at least partially interconnected by a wireless network.

[0053] Each participant device 12, 24a-c, or 22, 24a-c sets the time for the respective fieldbus 10 or 20 and is therefore referred to as the master. For the first fieldbus 10, for example, the controller 12 is initially the master, which in Fig. 1 is shown as a clock face with solid lines. In the second fieldbus 20, for example, the subscriber device 24a is the fieldbus master. The clock of a master 12 or 24a specifies the time in the fieldbus, with the other subscriber devices of a fieldbus, i.e. subscriber devices 14a-c in the first fieldbus or subscriber devices 22, 24b-c, each deriving their time from the master. This occurs, for example, when the subscribers within a fieldbus exchange messages at regular or irregular intervals using the Precision Time Protocol in accordance with the IEEE 1588 standard, and in this way achieve and maintain a common understanding of time.

[0054] Within the first fieldbus 10 and the second fieldbus 20, both non-time-sensitive and time-sensitive data can be transmitted, as will be described in more detail below. For example, data transmission in both fieldbuses can be divided into transmission cycles according to the IEEE 802.1Q standards. Different cycle times can be defined for the first fieldbus 10 and the second fieldbus 20. Since different time domains 16 and 26 are assigned to the first fieldbus 10 and the second fieldbus 20, respectively, the cycle times in this case can also be considered as assigned to the time domain.

[0055] Furthermore, 10 first time slots can be defined in the first fieldbus and 20 second time slots in the second fieldbus, in which a transmission of real-time data between two participant devices of the same fieldbus is possible. The transmission of real-time data can be a clocked end-to-end transmission between two participant devices or a transmission with low delays that are known, deterministic, and / or causally controllable to the extent that they meet real-time requirements.

[0056] To define the transmission cycles and time slots for the transmission of time-sensitive data, one or more participant devices of the respective fieldbus can each have a scheduler function. The scheduler is responsible for defining the cycle times in the first or second fieldbus and communicating these to the other participant devices of the respective fieldbus. Furthermore, a scheduler can be configured to receive requests for the transmission of time-sensitive data in the first or second fieldbus, manage assigned time slots, communicate with a requesting participant device to negotiate time slots for time-sensitive transmission, and confirm or reject the request accordingly. The scheduler can also be configured to communicate assigned time slots for the transmission of time-sensitive data to the other participant devices.In the following, it is assumed that in the first fieldbus 10, at least one of the subscriber devices 12, 24a-c is configured as a scheduler and implements the corresponding protocols (e.g., according to the IEEE 802.1Q standard or a standard derived therefrom). Likewise, it is assumed that in the second fieldbus 20, at least one of the subscriber devices 22, 24a-c performs a scheduler function.

[0057] System 1 further comprises a gateway 30, via which both fieldbuses 10, 20 are communicatively connected to each other. Fig. 1that the fieldbuses 10, 20 are connected to one another via their controllers 12 and 22. However, this is not mandatory. Rather, the gateway 30 has an interface to each of the fieldbuses 10 and 20, so that it represents a subscriber device with regard to the respective fieldbus 10, 20. The gateway 30 supports at least two time domains 32 and 34, which, when connected, are synchronized with the time domains of the fieldbuses 16 and 26 as part of the respective time domain. Additional time domains can be supported depending on the number of fieldbuses to be connected. In particular, the gateway comprises timers 36 and 38, which can be configured for the first 16 and the second time domain 26, respectively.

[0058] The participant devices of the fieldbuses can be addressed via identifiers. Fig. 1This illustrates, by way of example, the identifier ID14a of a first subscriber device 14a in the first fieldbus and the identifier ID22 of a second subscriber device 22 in the second fieldbus. It is merely an example that the second subscriber device 22 is also the controller in the second fieldbus. The identifiers can, as mentioned above, be, for example, MAC addresses, IP addresses, or other identifiers.

[0059] Furthermore, the gateway can maintain virtual images of some fieldbus participant devices in its memory. Fig. 1illustrates by way of example the virtual images 12', 14'a, 14'b and 22', 24'c, which can each be addressed via their subscriber device identifiers ID12', ID14'a, ID14'b and ID22', ID24'c. The virtual images of the subscriber devices are mutually assigned to the respective subscriber devices, i.e. subscriber device 14a in the first fieldbus 10 is assigned to its virtual image 14'a and vice versa, subscriber device 14b is assigned to its virtual image 14'b and vice versa, subscriber device 12 is assigned to its virtual image 12' and vice versa, and subscriber device 22 in the second fieldbus 20 is assigned to its virtual image 22' and vice versa. In this way, one or more subscriber devices in the first or second fieldbus can each be assigned a virtual image.

[0060] The virtual images can appear as participant devices in the other fieldbus. For example, the virtual images 12', 14'a and 14'b can appear as participant devices of the second fieldbus 20, although their assigned real devices are participant devices of the first fieldbus 10. Likewise, in the example of the Fig. 1The virtual image 22' appears as a subscriber device in the first fieldbus 10, even though the associated subscriber device 22 is connected to the second fieldbus 20. The virtual images are addressable via their associated subscriber device identifiers. For example, the virtual images 12', 14'a, 14'b are each identifiable and addressable for other subscriber devices in the second fieldbus 20 via their associated subscriber device identifiers ID12', ID14'a, ID14'b. Likewise, the virtual images 22', 24'c are identifiable and addressable for the other subscriber devices of the first fieldbus 10 via the associated subscriber device identifiers ID22', ID24'c.

[0061] In this way, it is possible to integrate participant devices from another fieldbus into a fieldbus. The corresponding virtual images have a corresponding interface with respect to the fieldbus communication protocols (e.g., based on Ethernet). For example, the virtual images 12', 14'a, 14'b can participate in the communication protocol of the second fieldbus 20. With respect to the second fieldbus 20, they form termination points of the fieldbus communication protocols in the same way as the "real" participant devices of the second fieldbus 20. Likewise, the virtual images 22', 24'c represent a termination point of the fieldbus communication protocols as an interface to the first fieldbus 10.

[0062] Fig. 2shows an exemplary time diagram of the first fieldbus 10 and the second fieldbus 20. Here, the first fieldbus 10 has communication or transmission cycles with periodically recurring cycle intervals TC1, which are determined in terms of position and duration according to the Fig. 2 upper timeline. Accordingly, the second fieldbus has 20 communication cycles with periodically recurring cycle intervals TC2, which are defined in terms of position and duration according to the Fig. 2 lower timeline. In Fig. 2 The inverse of the clock frequencies 1 / f1 and 1 / f2, namely the clock cycle duration, is represented by a black bar. Even if both clock frequencies f1 and f2 nominally (i.e., according to a specification) have the same frequencies, it is possible that the clocks of time domains 16 and 26 of the two fieldbuses run at different speeds if the actual values ​​of the clock frequencies f1 and f2 differ slightly.

[0063] In the fieldbuses 10, 20, first time slots 50 and second time slots 52 for transmitting time-sensitive data within the respective fieldbus 10, 20 can be defined, negotiated, or determined. For this purpose, for example, one of the subscriber devices 12, 14a-c in the first fieldbus 10 and one of the subscriber devices 22, 24a-c in the second fieldbus 20 can be configured as a real-time scheduler (time-aware scheduler) in accordance with the IEEE 802.1QBv standard. For example, the first time slots 50 and the second time slots 52 coincide with the beginning of the corresponding communication cycles. In general, the time slots 50, 52 for time-sensitive transmission can be located at any position within a transmission cycle. It is also possible to define several separate time slots 50, 52 for time-sensitive communication per transmission cycle.

[0064] Fig. 2also shows time periods 54 and 56, which belong to the respective transmission cycles that lie outside the time slots 50 and 52 reserved for the transmission of time-sensitive data. In these intervals 54 and 56, non-time-sensitive data can be transmitted within the fieldbuses 10 and 20, for example, according to the Ethernet protocol, for which the CSMA / CD (Carrier Sense Multiple Access with Collision Detection) access procedure applies.

[0065] To connect the gateway 30, in one embodiment, the timers 36 and 38 of the gateway 30 are first synchronized as a slave with respect to the time domains 16, 26 of the fieldbuses 10 and 20. This gives the gateway a synchronized interface as a subscriber device to both the first fieldbus 10 and the second fieldbus 20. Thus, the gateway 30 can, for example, observe the time offset between the time domain 16 of the first fieldbus 10 and the time domain 26 of the second fieldbus 20. Furthermore, the gateway 30 also knows the corresponding cycle times TC1 and TC2, the timing of the communication cycles, and the time slots 50 and 52 in which time-sensitive communication is processed in the respective fieldbuses 10, 20.

[0066] This makes it possible to initially exchange non-time-sensitive data between the fieldbuses. Such a transmission can be achieved, for example, by transmitting non-time-sensitive data 60 from the first fieldbus 10 to the gateway 30 during a first non-time-sensitive interval 54, as shown in Fig. 2 symbolized by the arrow 60. This data 60 can be temporarily stored in a buffer 35 of the gateway 30 (see also Fig. 1 ), as indicated by step 62 (in Fig. 2). Finally, the buffered data can be transmitted from the gateway 30 to the second fieldbus 20 during intervals 56 outside the second time slots 52, as symbolized by the arrow 64. For example, in order to transmit the data 64 to the second fieldbus using the CSMA / CD method or another contention method, the gateway 30 must ensure that the second fieldbus 20 is free for transmission during the time slots 56.

[0067] An exchange of non-time-sensitive data 60, 64 between the fieldbuses can be used, for example, to support frequency synchronization of the first time domain 16 and the second time domain 26. Through such synchronization of the timer clock frequencies, the time offset between the times of both time domains 16, 26 remains stable, thereby simplifying the determination of times in the gateway 30 or in the subscriber devices 12, 14a-c or 22, 24a-c of the first and second fieldbus with respect to the respective other time domain 16, 26. For this purpose, the following method for synchronizing the clock frequencies f1 and f2 of the timers 36 and 38 will be described as an example. In one embodiment, the clocks 36, 38 of the gateway 30 are initially synchronized as slaves of the first 16 or second 26 time domains and have the same nominal frequency.Frequency synchronization can now be achieved by designating the first timer 36 of the gateway 30 as the master for the first fieldbus 10, so that the gateway 30 can determine the timing in the first fieldbus. Furthermore, the frequency f1 of the first timer 36 of the gateway 30 can be synchronized to the frequency f2 of the second time domain 26. Synchronizing exclusively the frequencies f1 and f2 in the time domains 16, 26 can prevent time jumps in the subscriber devices in the first fieldbus 10. The frequencies can be synchronized during ongoing operation of the first fieldbus 10 using an adjustment period that is selected to be long enough so that the processes of the first fieldbus 10 can run smoothly.

[0068] Fig. 3schematically shows a detailed timing diagram of the cycle times defined for the first and second fieldbuses 10, 20 according to some aspects of the invention. In one example, the clock generators in the subscriber devices of the fieldbuses 10 and 20 may have the same clock frequencies f1 = f2, for example, according to the method described above. Fig. 3 is the inverse of the clock frequencies 1 / f1 or 1 / f2, namely the clock cycle duration, each illustrated by a black bar.

[0069] In the present example, only the clock frequencies between the first and second fieldbuses 10, 20 are synchronized. Therefore, a time offset 58 can occur between the start times of the communication cycles. Such a time offset 58 results, on the one hand, from the different definitions of time in the two fieldbuses 10, 20, and, on the other hand, from the difference between the start times of the communication cycles of the first fieldbus 10 and the second fieldbus 20, even if both fieldbuses had the same understanding of time. Furthermore, the communication cycles can have different durations TC1 and TC2. Therefore, the time offset 58 can generally only be defined with reference to an (absolute) reference time TRef. The absolute reference time TRef can be expressed accordingly both in the time of the first fieldbus 10 and in the time of the second fieldbus 20.If the time periods TC1 and TC2 are in a rational relationship to one another, a certain time offset 58 returns after a predictable number of cycles of the first or second fieldbus. In this case, the reference time TRef can be chosen arbitrarily within a return interval. For example, if the cycle time TC1 in the first fieldbus is 50 ms and the cycle time TC2 in the second fieldbus is 25 ms, the time offset 58 can be zero after a first cycle in the second fieldbus, 25 ms compared to the first fieldbus after a second cycle in the second fieldbus, and then zero again, and so on. However, if the time offset 58 is known at a time TRef, it is possible to determine the time offset 58 in advance for all communication cycles of the first and second fieldbus, even if the cycle time periods TC1 and TC2 are not in a rational relationship to one another.

[0070] Furthermore, different durations TS1 and TS2 of the first and second time slots 50 and 52 for time-sensitive communication can occur on fieldbuses 10 and 20, respectively, since these can be agreed upon independently for both fieldbuses 10 and 20. Furthermore, the first and second time slots 50 and 52 can exhibit temporal differences TD in their start times. These can generally only be predictably determined with reference to an absolute reference time TRef, since the start times of time slots 50 and 52 for time-sensitive communication can vary with the cycle times in the individual fieldbuses.

[0071] After frequency synchronization has been achieved, the gateway 30 can determine the cycle time durations TC1 and TC2 in the first and second fieldbuses 10, 20 at a reference time TRef. Furthermore, the gateway 30 can determine the time offset 58 between the first and second time domains 16, 26 at the reference time TRef. The gateway 30 can further communicate the cycle time duration TC1 of the first fieldbus 10 to the second fieldbus 20 and the cycle time duration TC2 of the second fieldbus 20 to the first fieldbus 10. This can be done with reference to the reference time TRef. In this way, for example, participant devices of the first or second fieldbus 10, 20 can predictably determine the communication cycles of the respective other fieldbus 20, 10.

[0072] Furthermore, virtual images of subscriber devices of one fieldbus can be instantiated as part of the other fieldbus in the memory of the gateway 30. This initializes the virtual images, for example, with their corresponding subscriber device identifiers as well as the assignments to their real fieldbus subscriber devices. In the example of the Fig. 1 The virtual images 12', 14'a, 14'b are instantiated for the subscriber devices 12, 14a, 14b of the first fieldbus 10, wherein, for example, the corresponding subscriber device identifiers ID12', ID14'a, ID14'b are assigned to the corresponding subscriber devices 12, 14a, 14b. This can be done, for example, using corresponding assignment tables stored in the gateway 30 and / or the assigned subscriber devices. Virtual images 22', 24'c are instantiated correspondingly for the subscriber devices 22 and 24c, respectively, of the second fieldbus 20.

[0073] To enable the virtual replicas to act as participant devices of the other fieldbus, the gateway 30 knows the corresponding times of the time domains. In particular, the gateway 30 knows the time offset 58 between the first and second time domains 16, 26 and the reference time TRef. Furthermore, the gateway 30 knows the cycle time TC1 of the first fieldbus 10 as well as the cycle time TC2 of the second fieldbus 20, as well as the times of the first and second time slots 50 and 52 defined in the first and second fieldbus for time-sensitive communication. For example, the virtual replicas can have read access to the memory of the gateway 30 for this purpose.

[0074] In this way, the gateway 30 can convert time information, i.e. information from at least one point in time and / or at least one time interval, which is present with respect to the time domain of one fieldbus, into time information from the other fieldbus. This can be used by the individual virtual images in such a way that, for example, the virtual image 14'a can receive a message from the second fieldbus 20 with a time information related to the second fieldbus 20 and, when forwarded to the assigned subscriber device 14a in the first fieldbus 10, converts it into a corresponding time information related to the first fieldbus 10. Conversely, the virtual image 14'a can receive a message from the assigned subscriber device 14a with a time information related to the first fieldbus 10, convert it into a time information related to the second fieldbus 20, and output it in converted form as a (virtual) subscriber device of the second fieldbus 20.

[0075] This functionality can be particularly useful when, for example, a subscriber device of the second fieldbus 20 wishes to request time slots for transmitting time-sensitive data to the first fieldbus 10. An example of such a request protocol is described below.

[0076] Fig. 4 shows an example of a request protocol for time slots for the transmission of time-sensitive data between the first fieldbus 10 and the second fieldbus 20. In the present case, a transmission of time-sensitive data from the subscriber device 14a in the first fieldbus 10 to the subscriber device 22 in the second fieldbus 20 is to be set up.

[0077] The request itself can originate from a subscriber device in the second fieldbus. For example, the request can originate from subscriber device 24c in the second fieldbus, whereby subscriber device 24c can have a scheduler functionality in the second fieldbus, allowing it to set up time slots 52 for transmitting time-sensitive data in the second fieldbus 20. The gateway 30 has integrated the virtual images 12', 14'a, 14'b as subscriber devices in the second fieldbus 20. The request can thus be directed to a virtual image of a subscriber device of the first fieldbus. In the present case, the virtual image 12' should be addressed because the assigned subscriber device 12, for example, has a scheduler functionality in the first fieldbus 10, allowing it to set up time slots 50 for transmitting time-sensitive data in the first fieldbus 10.

[0078] To request a time slot for transmitting time-sensitive data, the subscriber device 24c sends a request 42 to the virtual image 12' of the subscriber device 12 in the gateway 30. The request 42 contains, for example, the subscriber device identifier ID14'a. This subscriber device is known as the virtual image of the source for the time-sensitive data in the second fieldbus. Furthermore, the request 42 can contain an identifier of the data destination for the time-sensitive data, for example, the second subscriber device identifier ID22' or the identifier of the real subscriber device ID22. Furthermore, the request 42 can contain a time specification, TA20, i.e., the specification of at least one point in time and / or at least one time interval. This time specification can, for example, define several possible time slots that can be set up in the second fieldbus 20 for transmitting time-sensitive data.The time specification can be related to the time regime in the second fieldbus 20, ie related to the second time domain 26.

[0079] The gateway 30 can receive the request 42 directed to the virtual image 12', whereupon the gateway 30 forwards the request 43 to the subscriber device 12, i.e., to the scheduler in the first fieldbus 10. Optionally, the gateway 30 can use the identifier ID14a of the real subscriber device instead of the subscriber device identifier ID14'a. Furthermore, the gateway 30 can use the subscriber device identifier ID22', since the assigned virtual image in the first fieldbus 10 can be viewed as an identifier for the data destination of the time-sensitive data. If the received request 42 contains a time specification TA20, the gateway 30 converts this into a time specification TA10 and uses this for the forwarded request 43, which is related to the first fieldbus 10, taking into account the time offset 58 from the reference time TRef.

[0080] Upon receipt of the request 43 or later, the subscriber device 12 in the first fieldbus 10 can determine a suitable time slot 50 and send an acknowledgment message 45 to the gateway 30 for forwarding to the second fieldbus 10. The acknowledgment message 45 can contain a time specification TB10 related to the first fieldbus 10. For example, the time specification TB10 can define the time slot 52. Upon receipt, the gateway 30 converts the time specification TB10 into a time specification TB20 related to the second fieldbus 20 and forwards it in the acknowledgment message 46 to the subscriber device 24c in the second fieldbus 20. The gateway 30 can use the virtual image 12' for this purpose, which is configured for this purpose as a subscriber device in the second fieldbus 20.

[0081] Based on the described request protocol, the subscriber device 12 in the first fieldbus 10 can set up 49 the time slot 50, and the subscriber device 24c in the second fieldbus 20 can set up 48 the time slot 52, whereby the time slots 50 and 52 overlap.

[0082] Fig. 5 shows a schematic timing diagram of a first fieldbus 10 and a second fieldbus 20 during a transmission of time-sensitive data. In the present case, for example, according to the request protocol described above or a comparable protocol, time slots 50 were agreed in the first fieldbus 10 and time slots 52 in the second fieldbus 20 for the transmission of time-sensitive data from the subscriber device 14c to the subscriber device 24b, which at least partially overlap.

[0083] In particular, corresponding subscriber devices of the first and second fieldbus have agreed on common overlap areas OL1 and OL2 in the time slots 50 and 52, respectively, and exchanged this information via the gateway 30, so that this information is also known to the gateway 30.

[0084] In one embodiment, it is not necessary to create an overlap area OL1, OL2 for time-sensitive communication in each cycle TC1 or TC2 of the first or second fieldbus 10, 20. For example, it may be sufficient to define an overlap area during every second, third, etc. cycle of the first or second fieldbus 10, 20.

[0085] If the first and second time slots 50 and 52, respectively, reserved for time-sensitive communication within the fieldbuses are known during the communication cycles of the first and second fieldbuses 10, 20, the overlap areas OL1 and OL2 for time-sensitive communication between the fieldbuses can be determined or calculated based on rules. It is then sufficient to determine a single pair of overlapping time slots 50 and 52 at a reference time TRef. The reservation of the time slots 50 and 52 can be made in the first and second fieldbuses, respectively, using the request protocol as described above. In one embodiment, the gateway 30 can provide the time information of the first and second time slots 50 and 52, respectively, with respect to the fieldbus's own time domain. The determination of the overlap areas OL1 and OL2 can thus also be made with respect to the fieldbus's own time domain.

[0086] If the cycle times TC1 and TC2 are in a rational relationship to each other, regularly recurring overlap areas OL1 and OL2 result. In this case, the negotiation and / or determination of time slots 50 and 52 is simplified, so that in these cases an overlap area OL1, OL2 recurs regularly and therefore does not need to be negotiated or determined individually. The reference time TRef can also be chosen arbitrarily within the regularly recurring period. If the cycle times TC1 and TC2 are equal, the time offset applies regardless of an arbitrarily selectable reference time TRef.

[0087] In one embodiment, the gateway 30 is further configured to transmit time-critical data 70, 72 during the temporally overlapping time slots, e.g., OL1 or OL2. In one embodiment, this is achieved by the gateway 30 determining the time slots for time-sensitive transmission 50 and 52 determined between the first and second fieldbuses 10, 20, and in particular the respective overlap intervals OL1, OL2, and passing the signals between the first and second fieldbuses during these intervals.

[0088] Fig. 4further shows a protocol for transmitting time-sensitive data between the first and second fieldbuses. For this purpose, it is assumed that, for example, the previously described procedure for setting temporally overlapping time slots 50, 52 was carried out in the first and second fieldbuses. In order to send time-sensitive data from the subscriber device 14a in the first fieldbus to the subscriber device 22, the subscriber device 14a first sends this data 70a to the gateway 30 during the overlap interval OL1, wherein the data 70a contains the subscriber device indicator ID22' for identifying the virtual image 22'. The gateway 30 receives the time-sensitive data 70a during the overlap interval OL1.For forwarding, the gateway determines the assigned identifier ID22 of the subscriber device 22 in the second fieldbus during the overlap interval OL1 and forwards the data 70b to the subscriber device 22 in the second fieldbus 20 during the overlap interval OL1.

[0089] Using the described method, System 1, and Gateway 30, it is possible to network time-sensitive fieldbuses 10, 20 without having to align the fieldbus times and communication cycles of the fieldbuses. This allows existing and partially incompatible fieldbuses to be configured for the exchange of both non-time-sensitive and time-sensitive data.

Claims

1. Method for networking a first time-sensitive field bus (10) with a second time-sensitive field bus (20), wherein the first time-sensitive field bus (10) comprises a first subscriber device (14a) and has a first dedicated time domain (16), and wherein the second time-sensitive field bus (20) comprises a second subscriber device (22) and has a second dedicated time domain (26), wherein the first time domain (16) and the second time domain (26) are frequency-synchronized, wherein the first and the second field bus (10, 20) are connected to one another by means of a gateway (30), wherein the method has the following steps: - storing in the memory of the gateway (30) a first subscriber device identifier (ID14'a), wherein the first subscriber device identifier (ID14'a) identifies a virtual image (14'a) of the associated first subscriber device (14a) of the first field bus (10); - storing in the memory of the gateway (30) a second subscriber device identifier (ID22'), wherein the second subscriber device identifier (ID22') identifies a virtual image (22') of the associated second subscriber device (22) of the second field bus (20); - determining a first cycle time duration (TC1) of the first field bus (10) and a second cycle time duration (TC2) of the second field bus (20) by the gateway (30) at a reference time (TRef); and - determining a time offset (58) between the first time domain (16) and the second time domain (26) by the gateway (30) at the reference time (TRef).

2. Method according to Claim 1, furthermore having the following steps: - receiving, by the gateway (30), a request (42) from the second field bus (20) for a time slot (50) for transmitting time-sensitive data from the first subscriber device (14a) of the first field bus (10) to the second subscriber device (22) of the second field bus (20); - forwarding, by the gateway (30), the request (43) to the first field bus (10); - receiving, by the gateway (30), an acknowledgement message (45) from the first field bus (10); - forwarding, by the gateway (30), the acknowledgement message (46) to the second field bus (20).

3. Method according to Claim 2, - wherein the received request (42) comprises a time indication (TA10) of at least one point in time and / or at least one time interval, the time indication being related to the time domain (26) of the second field bus (20); - wherein the method further comprises determining, by the gateway (30), the time indication (TA10) from the received request (42) related to the time domain (16) of the first field bus (10), taking into account the time offset (58) with respect to the reference time (TRef); - wherein the request (43) forwarded to the first field bus (10) comprises the time indication (TA10) related to the time domain (16) of the first field bus (10); wherein the method furthermore has the following steps: - setting a first time slot (50) for communicating time-sensitive data in the first field bus (10), by the first field bus (10), based on the time indication (TA10) from the request (43) related to the first time domain (16) of the first field bus (10); and - setting a second time slot (52) for communicating time-sensitive data in the second field bus (20), by the second field bus (20), based on the time indication (TA20) related to the second time domain (26) of the second field bus (20); - wherein the first time slot (50) is set by the first field bus (10) and the second time slot (52) is set by the second field bus (52) in each case in such a way that the first time slot (50) of the first field bus (10) and the second time slot (52) of the second field bus (20) overlap in time (OL1, OL2).

4. Method according to Claim 3, wherein: - the received acknowledgement message (45) from the first field bus (10) comprises a further time indication (TB10) of at least one point in time and / or at least one time interval, the further time indication (TB10) being related to the time domain (16) of the first field bus (10); - wherein the method furthermore comprises determining, by the gateway (30), the further time indication (TB20) from the received acknowledgement message (45) related to the time domain (26) of the second field bus (20), taking into account the time offset (58) with respect to the reference time (TRef); - wherein the acknowledgement message (46) forwarded to the second field bus (20) comprises the further time indication (TB20) related to the time domain (16) of the second field bus (20); - wherein the first time slot (50) is set by the first field bus (10) on the basis of said further time indication (TB10); and - wherein the second time slot (52) is set by the second field bus (20) on the basis of said further time indication (TB20).

5. Method according to either of Claims 3 or 4, wherein the method furthermore has the following steps: - receiving, by the gateway (30), time-sensitive data (70a) from the first subscriber device (14a) of the first field bus (10), wherein the time-sensitive data (70a) contain the second subscriber device indicator (ID22') during the overlap (OL1, OL2) of the first time slot (50) and the second time slot (52); - determining, by the gateway (30), an identifier (ID22) of the second subscriber device (22) based on the second subscriber device identifier (ID22') during the overlap (OL1, OL2) of the first time slot (50) and the second time slot (52); - forwarding (70b), by the gateway (30), the received time-sensitive data to the second subscriber device (22) during the overlap (OL1, OL2) of the first time slot (50) and the second time slot (52).

6. Method according to one of Claims 1 to 5, wherein there are, between the first field bus (10) and the second field bus (20): - different durations (TS1, TS2) of the first and second time slots (50, 52) for time-sensitive data; and / or - time differences (TD) of the first and second time slots (50, 52) for time-sensitive data.

7. Method according to one of Claims 1 to 6, wherein the gateway (30) has a first timer (36) and a second timer (38), wherein the method furthermore has the following steps: - synchronizing the first timer (36) as a slave with the first time domain (16) of the first field bus (10); - synchronizing the second timer (38) as a slave with the second time domain (26) of the second field bus (20); - initially synchronizing exclusively the frequency of the first timer (36) as a slave with frequency (f2) of the second time domain (26) of the second timer (38); and then - setting the first timer (36) as a master for the first field bus (10) in order to set the frequency (f1) of the first field bus (10) to the frequency of the first timer (38).

8. Gateway (30) for networking a first time-sensitive field bus (10) with a second time-sensitive field bus (20), wherein the first time-sensitive field bus (10) comprises a first subscriber device (14a) and has a first dedicated time domain (16), and wherein the second time-sensitive field bus (20) comprises a second subscriber device (22) and has a second dedicated time domain (26), wherein the first time domain (16) and the second time domain (26) are frequency-synchronized, wherein the gateway (30) comprises: - means for connecting in each case the first time-sensitive field bus (10) and the second time-sensitive field bus (20) to the gateway (30); - means for storing in the memory of the gateway (30) a first subscriber device identifier (ID14'a), wherein the first subscriber device identifier (ID14'a) identifies a virtual image (14'a) of the associated first subscriber device (14a) of the first field bus (10); - means for storing in the memory of the gateway (30) a second subscriber device identifier (ID22'), wherein the second subscriber device identifier (ID22') identifies a virtual image (22') of the associated second subscriber device (22) of the second field bus (20); - means for determining a first cycle time duration (TC1) of the first field bus (10) and a second cycle time duration (TC2) of the second field bus (20) at a reference time (TRef); and - means for determining a time offset (58) between the first time domain (16) and the second time domain (26) at the reference time (TRef).

9. Gateway according to Claim 8, furthermore having: - means for receiving a request (42) from the second field bus for a time slot (50) for transmitting time-sensitive data from the first subscriber device (14a) of the first field bus (10) to the second subscriber device (22) of the second field bus (20); - means for forwarding the request to the first field bus (30); - means for receiving an acknowledgement message from the first field bus (10); - means for forwarding the acknowledgement message to the second field bus (20).

10. Gateway according to Claim 9, - wherein the received request (42) comprises a time indication (TA20) of at least one point in time and / or at least one time interval, the time indication being related to the time domain (26) of the second field bus (20); - wherein the gateway (30) has means for determining the time indication (TA10) from the received request (42) related to the time domain (16) of the first field bus (10), taking into account the time offset (58) with respect to the reference time (TRef); - wherein the request (43) forwarded to the first field bus (10) comprises the time indication (TA10) related to the time domain (16) of the first field bus (10).

11. Gateway according to one of Claims 8 to 10, furthermore comprising: - means for determining a time overlap (OL1, OL2) of a first time slot (50) set by the first field bus for communicating time-sensitive data in the first field bus (10) and a second time slot (52) set by the second field bus (20) for communicating time-sensitive data in the second field bus (20); - means for receiving time-sensitive data (70a) from the first subscriber device (14a) of the first field bus (10), wherein the time-sensitive data (70a) contain the second subscriber device indicator (ID22') during the overlap (OL1, OL2) of the first time slot (50) and the second time slot (52); - means for determining an identifier (ID22) of the second subscriber device (22) based on the second subscriber device identifier (ID22') during the overlap (OL1, OL2) of the first time slot (50) and the second time slot (52); and - means for forwarding (70b) the received time-sensitive data (70a) to the second subscriber device (22) during the overlap (OL1, OL2) of the first time slot (50) and the second time slot (52).

12. System for networking at least two time-sensitive field buses, having: - a first time-sensitive field bus (10), which comprises a first subscriber device (14a) and has a first dedicated time domain (16); - a second time-sensitive field bus (20), which comprises a second subscriber device (22) and has a second dedicated time domain (26), wherein the first time domain (16) and the second time domain (26) are frequency-synchronized, - a gateway (30) according to one of Claims 8 to 11, which connects the first and the second field bus (10, 20) to one another.

13. System according to Claim 12, wherein - the gateway (30) has means for receiving a request (42) from the second field bus for a time slot (50) for transmitting time-sensitive data from the first subscriber device (14a) of the first field bus (10) to the second subscriber device (22) of the second field bus (20); - the gateway (30) has means for forwarding the request (42) to the first field bus (30); - the gateway (30) has means for receiving an acknowledgement message (45) from the first field bus (10); - the gateway (30) has means for forwarding the acknowledgement message (46) to the second field bus (20).

14. System according to Claim 13, - wherein the received request (42) comprises a time indication (TA20) of at least one point in time and / or at least one time interval, the time indication being related to the time domain (26) of the second field bus (20); - wherein the gateway (30) has means for determining the time indication (TA10) from the received request (42) related to the time domain (16) of the first field bus (10), taking into account the time offset (58) with respect to the reference time (TRef); - wherein the request (43) forwarded to the first field bus (10) comprises the time indication (TA10) related to the time domain (16) of the first field bus (10); - wherein the first field bus (10) has means for setting a first time slot (50) for communicating time-sensitive data in the first field bus (10), based on the time indication (TA10) from the request (43) related to the first time domain (16) of the first field bus (10); - wherein the first field bus (10) has means for setting a second time slot (52) for communicating time-sensitive data in the second field bus (20), based on the time indication (TA20) related to the second time domain (26) of the second field bus (20); and - wherein the first time slot (50) is set by the first field bus (10) and the second time slot (52) is set by the second field bus (52) in each case in such a way that the first time slot (50) of the first field bus (10) and the second time slot (52) of the second field bus (20) overlap in time (OL1, OL2).

15. System according to Claim 14, - wherein the acknowledgement message (45) received by the gateway (30) from the first field bus (10) comprises a further time indication (TB10) of at least one point in time and / or at least one time interval, the further time indication (TB10) being related to the time domain (16) of the first field bus (10); - wherein the gateway (30) has means for determining the further time indication (TB20) from the received acknowledgement message (45) related to the time domain (26) of the second field bus (20), taking into account the time offset (58) with respect to the reference time (TRef); - wherein the acknowledgement message (46) forwarded to the second field bus (20) comprises the further time indication (TB20) related to the time domain (16) of the second field bus (20); - wherein the first time slot (50) is set by the first field bus (10) on the basis of said further time indication (TB10); and - wherein the second time slot (52) is set by the second field bus (20) on the basis of said further time indication (TB20).