Device, communication system, and time synchronization method

Abstract

The input / output device (31) includes a difference value calculation means for calculating a difference between a scheduled signal transmission time received in advance from the communication unit (30) and a reception time of a synchronization signal transmitted from the communication unit (30), a difference value storage means for storing the calculated difference value, and a time update means for updating the time at which information is received from the device (4) or the time at which information is transmitted to the device (4) based on the difference value. This makes it possible to synchronize the time at which information is received from the device (4) or the time at which information is transmitted to the device (4) with the time managed by the communication unit (30) with high precision.

Description

[Technical Field]

[0001] The present disclosure relates to an apparatus, a communication system, and a time synchronization method. [Background technology]

[0002] In factory automation (FA) sites, systems are operated that control multiple devices via industrial networks. Such systems require accurate cooperation between multiple devices. For example, in a configuration in which one or more input / output devices are connected to a communication unit that is connected to a network host such as a programmable logic controller (PLC) via an industrial network, it is necessary to appropriately adjust the time information between the communication unit and the input / output devices.

[0003] Regarding such time information adjustment, for example, Patent Document 1 describes a control device that aims to achieve time synchronization between different protocols. This control device includes a first communication means for transmitting and receiving data according to a first protocol, a second communication means for transmitting and receiving data according to a second protocol different from the first protocol, and a synchronization means for time synchronization between a first timer included in the first communication means and a second timer included in the second communication means.

[0004] Furthermore, Patent Document 2 describes a control system for FA that aims to simplify processing related to time synchronization between units and shorten the time required for processing. This control system includes a first unit and a second unit, each having a timer, a data line for exchanging data including timer values indicated by the timers between the first unit and the second unit, a signal line electrically connecting the first unit and the second unit, and adjustment means connected to the signal line and the data line, and when the adjustment means receives a trigger signal via the signal line, it acquires the timer value via the data line and synchronizes the timer of the second unit with that of the first unit based on the acquired timer value. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-064219 [Patent Document 2] International Publication No. 2021 / 002421 Summary of the Invention [Problem to be solved by the invention]

[0006] To synchronize both timers, it is necessary to update the value of one of the timers, which requires processing time. However, the techniques described in the above patent documents do not take this processing time into consideration, resulting in a problem that the updated timer value will include a deviation equivalent to the processing time from the intended value. For this reason, there is a need for a new technique for achieving high-precision time synchronization.

[0007] The present disclosure has been made in consideration of the above-described circumstances, and aims to provide a device, a communication system, and a time synchronization method that are capable of performing time synchronization with high accuracy. [Means for solving the problem]

[0008] In order to achieve the above object, the device according to the present disclosure comprises: a difference value calculation means for calculating a difference value between a signal transmission scheduled time received in advance from another device and a reception time of a synchronization signal transmitted from the other device; a difference value storage means for storing the calculated difference value; and a time update unit that updates the time when information is received from the target device or the time when information is transmitted to the target device based on the difference value. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to perform time synchronization with high accuracy. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing the overall configuration of a control system according to an embodiment. [Figure 2] FIG. 1 shows a configuration of a remote I / O device according to an embodiment. [Figure 3] FIG. 1 shows a configuration of a communication unit according to an embodiment. [Figure 4] FIG. 1 shows a configuration of an input / output device according to an embodiment. [Figure 5] 1 is a flowchart showing a procedure for calculating a difference value according to an embodiment; [Figure 6] 1 is a flowchart showing a procedure for a measurement value change notification process according to an embodiment. [Figure 7] 1 is a flowchart showing a procedure for a control value transmission process according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0012] (Embodiment) FIG. 1 is a diagram showing the overall configuration of a control system 1 according to an embodiment of the present disclosure. The control system 1 corresponds to a part of an FA system installed in a factory and controls devices 4, which are field devices such as sensors and actuators. This FA system may be, for example, a production system, an inspection system, a processing system, or other systems. The control system 1 includes a network host 2, a plurality of remote I / O (Input / Output) devices 3, and a plurality of devices 4 connected to each remote I / O device 3. The network host 2 and each remote I / O device 3 are connected to each other so as to be able to communicate with each other via a network 5, which is an industrial network conforming to the Fieldbus standard.

[0013] 1 shows a configuration in which the control system 1 includes three remote I / O devices 3, but there is no limit to the number of remote I / O devices 3 in the control system 1 as long as there is one or more. Also, while FIG. 1 shows a configuration in which four devices 4 are connected to each remote I / O device 3, there is no limit to the number of devices 4 connected to each remote I / O device 3 as long as there is one or more.

[0014] The network host 2 is, for example, a PLC, and operates the FA system by controlling each device 4. The network host 2 also collects error information, production status information, etc. of each device 4 from each remote I / O device 3.

[0015] The remote I / O device 3 is an example of a communication system according to the present disclosure. As shown in Fig. 2, the remote I / O device 3 includes a communication unit 30 and a plurality of input / output devices 31. The communication unit 30 and each input / output device 31 are connected via a bus 32 and a signal line 33. Although Fig. 2 shows a configuration in which the remote I / O device 3 includes two input / output devices 31, the number of input / output devices 31 in the remote I / O device 3 is not limited as long as it is one or more.

[0016] The communication unit 30 is an example of another device according to the present disclosure, and an example of a first device according to the present disclosure. The communication unit 30 relays information between the network host 2 and each input / output device 31. As shown in Fig. 3, the communication unit 30 includes a bus host circuit 300 and an MPU (Micro Processing Unit) 301. The bus host circuit 300 is a circuit for transmitting and receiving information to and from each input / output device 31 via a bus 32, and is configured with a dedicated circuit such as an ASIC (Application-Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

[0017] For example, the bus host circuit 300 transmits time information to each input / output device 31 via the bus 32, and transmits control instruction information to any of the input / output devices 31 via the bus 32. The bus host circuit 300 also receives, via the bus 32, measurement value change information transmitted from any of the input / output devices 31.

[0018] The MPU 301 includes a network I / F (interface) 302 and a timer 303, and performs central processing of the communication unit 30. The network I / F 302 is a communication I / F for communication via the network 5. The timer 303 is a counter for managing time in the communication unit 30, and increments its counter value at regular intervals. The counter value represents precise time in nanosecond units, based on a specific date and time. The timer 303 may be implemented using a dedicated circuit such as an ASIC or FPGA, or may be implemented using a general-purpose hardware timer. The timer 303 is synchronized with a timer (not shown) in the network host 2. This time synchronization, i.e., time synchronization between the networks 5, is achieved according to a known protocol such as the Precision Time Protocol (PTP) defined in IEEE 1588-2019.

[0019] The input / output device 31 is an example of a device according to the present disclosure and an example of a second device according to the present disclosure. The input / output device 31 is communicatively connected to a device 4 such as a sensor or an actuator, receives measurement values from the device 4, and transmits control values to the device 4. The device 4 is an example of a target device according to the present disclosure. As shown in FIG. 4 , the input / output device 31 includes a bus target circuit 310, an LSI (Large Scale Integration) 311, and a terminal block 312. The bus target circuit 310 is a circuit for transmitting and receiving information to and from the communication unit 30 via the bus 32, and is configured with a dedicated circuit such as an ASIC or FPGA. The LSI 311 includes an MCU (Micro Controller Unit) 313, an input / output processing circuit 314, a timer 315, and a difference value storage unit 316, and performs central processing of the input / output device 31.

[0020] The MCU 313 is an example of a differential value calculation means according to the present disclosure and an example of a time update means according to the present disclosure. The MCU 313 calculates differential values, calculates measurement value change times and transmission times, and exchanges information with the communication unit 30 via the bus target circuit 310, as described below. The input / output processing circuit 314 is configured, for example, by an ASIC, and receives information from the device 4 and transmits information to the device 4. The timer 315 is a counter for managing time in the input / output device 31 and has a configuration similar to the timer 303 included in the communication unit 30. The differential value storage unit 316 is an example of differential value storage means according to the present disclosure and is a memory that stores differential values, as described below. The terminal block 312 is hardware for wired communication with each device 4. In this embodiment, the terminal block 312 has eight ports and can be connected to a maximum of eight devices 4 for communication.

[0021] <Difference value calculation process> 5 is a flowchart showing the procedure of the difference value calculation process executed by the remote I / O device 3. The remote I / O device 3 periodically executes the difference value calculation process.

[0022] (Step S101) The communication unit 30 notifies each input / output device 31 of the scheduled signal transmission time, which is the time to transmit the synchronization signal. Specifically, the MPU 301 of the communication unit 30 instructs the bus host circuit 300 to transmit time information indicating the scheduled signal transmission time. Upon receiving this instruction, the bus host circuit 300 transmits the time information to each input / output device 31 via the bus 32. Thereafter, the processing of the remote I / O device 3 proceeds to step S102.

[0023] (Step S102) The bus target circuit 310 of each input / output device 31 receives the time information from the communication unit 30 via the bus 32 and notifies the MCU 313 of the received time information. The MCU 313 stores the time information notified from the bus target circuit 310 in its own memory. Thereafter, the process of the remote I / O device 3 proceeds to step S103.

[0024] (Step S103) The MPU 301 of the communication unit 30 determines whether the scheduled signal transmission time notified in S101 has arrived. If the scheduled signal transmission time has arrived (step S103; YES), the processing of the remote I / O device 3 proceeds to step S104. On the other hand, if the scheduled signal transmission time has not arrived (step S103; NO), the MPU 301 continues to make the determination in step S103.

[0025] (Step S104) The MPU 301 transmits the synchronization signal to each input / output device 31 via the signal line 33. Thereafter, the process of the remote I / O device 3 proceeds to step S105.

[0026] (Step S105) When the LSI 311 of each input / output device 31 receives the synchronization signal from the communication unit 30 via the signal line 33, it acquires the local time of the device at the time of reception, that is, the time managed by the timer 315. Thereafter, the process of the remote I / O device 3 proceeds to step S106.

[0027] (Step S106) The MCU 313 of each input / output device 31 calculates the difference between the time indicated by the time information received in step S102 (i.e., the scheduled signal transmission time) and the local time acquired in step S105. Thereafter, the process of the remote I / O device 3 proceeds to step S107.

[0028] (Step S107) The MCU 313 of each input / output device 31 stores the difference value calculated in step S106 in the difference value storage unit 316. Thereafter, the remote I / O device 3 ends the difference value calculation process for this cycle.

[0029] <Measurement value change notification processing> 6 is a flowchart showing the procedure of the measurement value change notification process executed by the input / output device 31. When the device 4 connected to the input / output device 31 is a sensor, the input / output device 31 periodically receives and acquires the measurement value of the device 4 from the device 4. The input / output device 31 executes the measurement value change notification process every time it acquires a measurement value from the device 4 that is a sensor.

[0030] (Step S201) The input / output processing circuit 314 of the input / output device 31 determines whether the measurement value acquired from the device 4 has changed from the previous measurement value, i.e., whether the acquired measurement value is different from the previous measurement value. If the acquired measurement value has changed from the previous measurement value (step S201; YES), the processing of the input / output device 31 proceeds to step S202. On the other hand, if the acquired measurement value has not changed from the previous measurement value (step S201; NO), the input / output device 31 ends the measurement value change notification processing.

[0031] (Step S202) The input / output processing circuit 314 of the input / output device 31 acquires the current local time, that is, the current time managed by the timer 315. Thereafter, the processing of the input / output device 31 proceeds to step S203.

[0032] (Step S203) The MCU 313 of the input / output device 31 calculates the time synchronized with the communication unit 30 (hereinafter referred to as the measurement value change time) based on the local time acquired in step S202 and the difference value stored in the difference value storage unit 316. Thereafter, the processing of the input / output device 31 proceeds to step S204.

[0033] (Step S204) The input / output device 31 notifies the communication unit 30 of the measurement value and the measurement value change time calculated in step S203. Specifically, the MCU 313 of the input / output device 31 instructs the bus target circuit 310 to transmit measurement value change information including the measurement value and the measurement value change time. Upon receiving this instruction, the bus target circuit 310 transmits the measurement value change information to the communication unit 30 via the bus 32. Thereafter, the input / output device 31 ends the measurement value change notification process.

[0034] The bus host circuit 300 of the communication unit 30 receives measurement value change information from the input / output device 31 via the bus 32 and notifies the MPU 301 of the received measurement value change information. The MPU 301 transmits the measurement value information notified from the bus host circuit 300 to the network host 2 via the network 5. As described above, the network host 2 and the communication unit 30 are time-synchronized, and the measurement value change time included in the measurement value change information is synchronized with the time of the communication unit 30. Therefore, the network host 2 can accurately grasp the time when the measurement value of the device 4 changed.

[0035] <Control value transmission process> 7 is a flowchart showing the procedure of the control value transmission process executed by the input / output device 31. In order to systematically control the device 4, which is an actuator, the network host 2 transmits control instruction information including a control value for the device 4 and a designated time for the control to the remote I / O device 3 to which the device 4 is connected via the network 5. The communication unit 30 of the remote I / O device 3 that receives the control instruction information transfers the control instruction information to the input / output device 31 to which the device 4 is connected via the bus 32. The input / output device 31 executes the control value transmission process every time it receives control instruction information from the communication unit 30.

[0036] (Step S301) The bus target circuit 310 of the input / output device 31 notifies the MCU 313 of the control instruction information received from the communication unit 30 via the bus 32. The MCU 313 extracts the designated time from the control instruction information notified from the bus target circuit 310. Thereafter, the processing of the input / output device 31 proceeds to step S302.

[0037] (Step S302) The MCU 313 calculates the transmission time based on the designated time extracted in step S301 and the difference value stored in the difference value storage unit 316. In other words, the MCU 313 calculates the transmission time synchronized with the communication unit 30. Thereafter, the processing of the input / output device 31 proceeds to step S303.

[0038] (Step S303) The MCU 313 extracts the control value from the control instruction information notified by the bus target circuit 310. After that, the processing of the input / output device 31 proceeds to step S304.

[0039] (Step S304) The MCU 313 sets the transmission time calculated in step S302 and the control value extracted in step S303 in the register of the input / output processing circuit 314. Thereafter, the processing of the input / output device 31 proceeds to step S305.

[0040] (Step S305) The input / output processing circuit 314 determines whether the transmission time has arrived. If the transmission time has arrived (step S305; YES), the processing of the input / output device 31 proceeds to step S306. On the other hand, if the transmission time has not arrived (step S305; NO), the input / output processing circuit 314 continues to perform the determination in step S305.

[0041] (Step S306) The input / output processing circuit 314 transmits the control value to the device 4. The device 4 operates in accordance with the received control value. After that, the input / output device 31 ends the control value transmission process.

[0042] As described above, the network host 2 and the communication unit 30 are time-synchronized, and the time at which the input / output processing circuit 314 of the input / output device 31 transmits a control value to the device 4 to be controlled is synchronized with the time of the communication unit 30. This allows the network host 2 to control the device 4, which is an actuator, at accurate time.

[0043] As described above, in the control system 1 of this embodiment, the input / output device 31 calculates a difference between the scheduled signal transmission time received in advance from the communication unit 30 and the reception time of the synchronization signal transmitted from the communication unit 30, and stores the difference in the difference value storage unit 316. Then, the input / output device 31 updates the time at which information is received from the device 4 or the time at which information is transmitted to the device 4, based on the difference stored in the difference value storage unit 316.

[0044] In this way, the input / output device 31 updates the time at which it receives information from the device 4 or the time at which it transmits information to the device 4 without performing processing to update the value of the timer 315, thereby enabling highly accurate time synchronization. As a result, high-speed I / O control becomes possible, and the takt time in the control system 1 can be shortened.

[0045] Furthermore, since the process of updating the value of the timer 315 is not performed, the processing load on the MCU 313 can be reduced.

[0046] (Variation 1) Even if the input / output device 31 is connected to a control unit such as a CPU unit instead of the communication unit 30, the method described in the above embodiment can be used to synchronize the time between the control unit and the input / output device 31. In such a configuration, the control unit is an example of each of the other device and the first device according to the present disclosure.

[0047] (Variation 2) The input / output device 31 may be configured so that the difference value is calculated by dedicated hardware instead of the MCU 313 .

[0048] (Variation 3) The input / output device 31 may be configured so that the measurement value change time is calculated by dedicated hardware instead of the MCU 313 .

[0049] (Variation 4) The input / output device 31 may be configured so that the transmission time is calculated by dedicated hardware instead of the MCU 313 .

[0050] The technical ideas according to the above-described modifications may be realized independently or in appropriate combination.

[0051] The present disclosure allows various embodiments and modifications without departing from the broad spirit and scope. Furthermore, the above-described embodiments are intended to explain the present disclosure and do not limit the scope of the present disclosure. In other words, the scope of the present disclosure is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and within the meaning of the disclosure equivalent thereto are considered to be within the scope of the present disclosure. [Industrial Applicability]

[0052] The present disclosure can be suitably adopted in an FA system. [Explanation of symbols]

[0053] 1 control system, 2 network host, 3 remote I / O device, 4 equipment, 5 network, 30 communication unit, 31 input / output equipment, 32 bus, 33 signal line, 300 bus host circuit, 301 MPU, 302 network I / F, 303 timer, 310 bus target circuit, 311 LSI, 312 terminal block, 313 MCU, 314 input / output processing circuit, 315 timer, 316 differential value storage unit

Claims

1. a difference value calculation means for calculating a difference value between a signal transmission scheduled time received in advance from another device and a reception time of a synchronization signal transmitted from the other device; a difference value storage means for storing the calculated difference value; a time update unit that updates the time when information is received from the target device or the time when information is transmitted to the target device based on the difference value. device.

2. The reception time is the local time of the device at the time of receiving the synchronization signal.

10. The device of claim 1.

3. the time update means updates the time at which the information was received based on the difference value when the value indicated by the information received from the target device is different from a previous value.

3. The device according to claim 1 or 2.

4. the time update means updates a designated time for transmitting information to the target device, the designated time being included in the control instruction information received from the other device, based on the difference value.

3. The device according to claim 1 or 2.

5. A first device and a second device, the first device transmits a signal transmission scheduled time to the second device, and transmits a synchronization signal to the second device at the subsequent signal transmission scheduled time; The second device is a difference value calculation means for calculating a difference value between the signal transmission scheduled time received from the first device and the reception time of the synchronization signal from the first device; a difference value storage means for storing the calculated difference value; a time update unit that updates the time when information is received from the target device or the time when information is transmitted to the target device based on the difference value. Communication system.

6. The equipment, calculating a difference between a signal transmission scheduled time received in advance from another device and a reception time of a synchronization signal transmitted from the other device; storing the calculated difference value in a difference value storage means; updating the time when the information is received from the target device or the time when the information is transmitted to the target device based on the difference value; Time synchronization method.

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