Power overlay communication system, controller, field device, and power supply control method

Abstract

To make both of communication and power be redundant without requiring a complex circuit even in the case of ring wiring.SOLUTION: When a field apparatus 20 detects communication abnormality on either one of ring wiring lines L connected to the field apparatus, the field apparatus notifies a controller 10 of a communication abnormality MSG 1 from the other. When notification of the communication abnormality MSG 1 is performed from any of field apparatuses 20 on one of ring wiring lines L connected to the controller, the controller 10 starts supply of backup power from the other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power superimposed communication technique for performing data communication and power supply using a power superimposed signal between devices connected in a daisy chain. [Background technology]

[0002] In recent years, in order to reduce the amount of wiring required for field devices such as sensors and actuators in industrial and building control systems, the unification of communication wiring and power supply wiring has been considered. Typical examples include Power over Ethernet (PoE) technology, which is applied to Ethernet (registered trademark) such as 100BASE-TX using LAN cables, and Power over DataLine (PoDL) technology, which superimposes power onto the recently standardized 10BASE-T1L Ethernet (Single-Pair-Ethernet). The characteristic of PoE and PoDL technologies is that they are P2P connections and are mainly applied to star wiring. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-195763 A Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, field devices such as sensors and actuators generally use daisy chain wiring rather than star wiring. In particular, in cases where the communication distance is 1 km, a large number of field devices, for example 50 devices, may be connected with a single daisy chain wiring. Therefore, if a fault such as a cable break or a field device failure occurs in the middle of the daisy chain wiring, communication with the field devices after the fault point will be cut off.

[0005] Conventionally, in daisy-chain Ethernet without power superposition, this problem was solved by connecting each field device in a ring shape with ring wiring and using "ring redundancy" with a redundancy protocol implemented in the MAC layer such as RSTP (Rapid Spanning Tree Protocol) as shown in Figure 6. Figure 6 is a block diagram showing an example of the configuration of a communication system using a conventional daisy-chain Ethernet. However, when power is superimposed on communication, if a fault such as a cable break occurs, both communication and power supply will be interrupted. In such cases, redundancy protocols such as RSTP do not handle power interruptions and will recover from communication failures on the assumption that the power supply is normal. Therefore, in order to achieve ring redundancy in daisy-chain Ethernet that performs power superimposed communication, a power redundancy function is required in addition to a communication redundancy function.

[0006] Prior art for power superposition communication in ring wiring includes, for example, a power over data line system with redundant power connections (see Patent Document 1, etc.). This technology is based on the PSE / PD method that uses both a power supply circuit (PSE: Power Sourcing Equipment) and a power receiving circuit (PD: Powered Device). The PSE and PD functions are implemented in each of the two communication ports of the communication device, and when a failure occurs, the PSE / PD function of the port switches and reconstructs the peer relationship with the other PD / PSE. A controller is required to control such a series of operations, and the circuitry required to achieve this becomes very complicated, making it difficult to adopt for field devices that are sensitive about product size and cost.Another problem with the PSE / PD method is that it cannot supply high power or AC power.

[0007] The present invention is made to solve these problems, and aims to provide a power supply technology that can provide redundancy for both communication and power, even in a ring wiring system, without requiring complex circuitry. [Means for solving the problem]

[0008] In order to achieve this object, the power superposition communication system of the present invention comprises a controller configured to supply power and communicate via a ring wiring, and a plurality of field devices daisy-chained in a ring shape via the ring wiring, operating on power supplied from the controller via the ring wiring and configured to communicate with the controller and other field devices via the ring wiring, wherein each of the plurality of field devices is configured such that, when it detects a communication abnormality on one side of the ring wiring connected to it, it notifies the controller of the communication abnormality from the other side, and when the controller is notified of the communication abnormality from any of the plurality of field devices, it begins supplying power from the ring wiring connected to it opposite the side that received the communication abnormality.

[0009] In addition, one configuration example of the power superposition communication system according to the present invention is configured such that, when each of the plurality of field devices detects communication recovery on one side of the ring wiring to which it is connected, it notifies the controller of the communication recovery, and when the controller is notified of the communication recovery from any of the plurality of field devices, it stops the supply of power from the opposite side.

[0010] In addition, one configuration example of the power superposition communication system according to the present invention is configured such that, when each of the plurality of field devices notifies the return of communication, it notifies the return of communication from both sides of the ring wiring to which it is connected.

[0011] In addition, one configuration example of the power superposition communication system according to the present invention is configured such that, when the controller receives notification of the return of communication from both sides of the ring wiring connected to the controller, it stops supplying power from the opposite side.

[0012] Moreover, a controller according to the present invention is a controller used in any one of the power superposition communication systems described above. A field device according to the present invention is a field device used in any one of the above-mentioned power superposition communication systems.

[0013] In addition, a power supply control method according to the present invention is a power supply control method used in a power superposition communication system including a controller configured to supply power and communicate via a ring wiring, and a plurality of field devices daisy-chained in a ring shape via the ring wiring, operating on power supplied from the controller via the ring wiring, and configured to communicate with the controller and other field devices via the ring wiring, the power supply control method including a first step of, when each of the plurality of field devices detects a communication abnormality on one side of the ring wiring connected to the controller, notifying the controller of the communication abnormality from the other side, and a second step of, when the controller is notified of the communication abnormality from one of the plurality of field devices, starting to supply power from the ring wiring connected to the controller from the side opposite to the side that received the communication abnormality.

[0014] In addition, one configuration example of the power supply control method according to the present invention further includes a third step of notifying the controller of the recovery of communication when each of the plurality of field devices detects the recovery of communication on one side of the ring wiring to which the field device is connected, and a fourth step of the controller stopping the supply of power from the opposite side when the controller is notified of the communication abnormality by any of the plurality of field devices. Effect of the Invention

[0015] According to the present invention, even in the case of ring wiring, it is possible to provide redundancy for both communication and power without requiring complex circuits. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a block diagram showing a configuration of a power superposition communication system. [Diagram 2] FIG. 2 is an explanatory diagram showing an operating state when power supply is stopped due to the occurrence of a failure. [Diagram 3] FIG. 3 is an explanatory diagram showing an operating state when backup power is being supplied. [Figure 4] FIG. 4 is an explanatory diagram showing an operating state when power supply is resumed after recovery from a fault. [Diagram 5] FIG. 5 is an explanatory diagram showing an operating state when the backup power supply is stopped. [Figure 6] FIG. 6 is a block diagram showing an example of the configuration of a conventional communication system using daisy-chain Ethernet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Next, an embodiment of the present invention will be described with reference to the drawings. [Power overlay communication system] First, a power superposition communication system 1 according to the present embodiment will be described with reference to Fig. 1. Fig. 1 is a block diagram showing the configuration of the power superposition communication system. As shown in FIG. 1, the main components of this power superposition communication system 1 include a controller 10, n (n is an integer equal to or greater than 2) field devices 20 (21, 22, ..., 2n), and a two-core ring wiring L that daisy-chains the controller 10 and the field devices 20 in a ring shape, and the controller 10 and the field devices 20 perform power superposition communication via the ring wiring L.

[0018] In this embodiment, an example will be described in which the power superimposed communication system 1 is a control system that remotely controls various equipment installed in large-scale facilities such as an industry, a plant, a building, etc., by data communication. Note that the power superimposed communication system 1 is not limited to this, and can be applied in the same manner as in this embodiment as long as the main parts of the controller 10 and the field devices 20 are regarded as a host device and a terminal device, and a plurality of terminal devices are daisy-chained in a ring shape to the host device via a ring wiring L.

[0019] [controller] The controller 10 is, for example, an industrial controller, and is configured to supply power to each field device 20 via a ring wiring L and to communicate with each field device 20. As shown in FIG. 1, the controller 10 includes, as its main circuit configuration, two physical layer interfaces PHY1 and PHY2, two power supply switches SW1 and SW2, and a control circuit CNT.

[0020] PHY1 and PH2 are configured to transmit and receive a high-frequency signal HF obtained by modulating communication data DT at a high frequency based on the Ethernet communication method via a high-pass filter and a ring wiring L. Of these, PHY1 transmits and receives the HF via a wiring L1 on one side connected to a terminal T1 of the ring wiring L connected to the controller 10, and PHY2 transmits and receives the HF via a wiring L2 on the other side connected to a terminal T2. The high-pass filter is made of, for example, a capacitive element, and is configured to attenuate the power component of the power superimposed signal flowing through the ring wiring L to pass the high-frequency signal component used for data communication.

[0021] SW1 is, for example, a manual changeover switch, and is connected to the wiring L1 via a low-pass filter, and is configured to switch the supply of power P to the wiring L1. SW2 is an electric switch that switches based on a switching signal SP from the CNT, and is connected to the wiring L2 via a low-pass filter, and is configured to switch the supply of power P to the wiring L2. The low-pass filter is, for example, an inductive element, and is configured to pass the power component of the power superimposed signal flowing through the ring wiring L and attenuate the high-frequency signal component used for data communication.

[0022] The CNT has a CPU and its peripheral circuits, and is configured to remotely control the field devices 20 by performing data communication with each of the field devices 20 via PHY1 and PHY2, and when a communication abnormality is notified from any of the field devices 20, start supplying power from the wiring L2 opposite to the wiring L1 that received the communication abnormality among the ring wirings L connected to the CNT by switching SW2 with a switching signal SP, and when a communication abnormality is notified from any of the field devices 20, stop supplying power from the wiring L2 on the opposite side. At this time, the CNT may stop supplying power from the wiring L2 on the opposite side when a communication recovery is notified from the wirings L1, L2 on both sides of the ring wiring L connected to the CNT.

[0023] [Field devices] The field devices 20 consist of instrumentation devices such as thermometers, pressure gauges, and flow meters, and are daisy-chained in a ring shape to the controller 10 via ring wiring L, and are configured to operate using power supplied from the controller 10 and to communicate with the controller 10 and other field devices 20. As shown in FIG. 1, each field device 20 has a similar configuration, and includes, as main circuit configurations, two physical layer interfaces PHY1 and PHY2, a power supply circuit PS, and a control circuit CNT.

[0024] PHY1 and PH2 are configured to transmit and receive a high frequency signal HF obtained by modulating communication data DT at a high frequency based on the Ethernet communication method, via a high pass filter and a wiring L. Of these, PHY1 transmits and receives the HF signal via a wiring L1 on one side connected to a terminal T1 of the ring wiring L connected to the field device 20, and PHY2 transmits and receives the HF signal via a wiring L2 on the other side connected to a terminal T2. Furthermore, PHY1 and PHY2 are configured to detect communication abnormalities and communication recovery on the lines L1 and L2 connected thereto, respectively, and notify the CNT of the abnormalities and communication recovery by means of detection signals A1 and A2 such as interrupt signals.

[0025] The PS is connected to the wirings L1, L2 via a low-pass filter, and is configured to receive power supplied from the wirings L1, L2, and generate and output an operating power source P used for the operation of the field device 20.

[0026] The CNT has a CPU and its peripheral circuits, and communicates data with the controller 10 and other field devices 20 via PHY1 and PHY2. If a communication abnormality is detected on either side of the ring wiring L connected to the CNT based on detection signals A1 and A2 from PHY1 and PHY2, the CNT notifies the controller 10 of the communication abnormality from the other side, and if communication recovery is detected on either side, the CNT notifies the controller 10 of the communication recovery.

[0027] [Operation of this embodiment] Next, the operation of the power supply control method of the power superposition communication system 1 according to the present embodiment will be described with reference to Figs. 2 to 5. Fig. 2 is an explanatory diagram showing an operation state when power supply is stopped due to the occurrence of a fault. Fig. 3 is an explanatory diagram showing an operation state when backup power is supplied. Fig. 4 is an explanatory diagram showing an operation state when power supply is resumed due to recovery from a fault. Fig. 5 is an explanatory diagram showing an operation state when backup power supply is stopped. In the following, the forward direction in which power is supplied during normal operation is the order of the field devices 21, 22, ..., 2n, and power is supplied to each field device 20 via the power supply switch SW1 of the controller 10.

[0028] As shown in FIG. 2, for example, when a fault such as a cable break occurs in the ring wiring L connecting the field devices 21 and 22, the power supply to the field devices 22, . . . , 2n stops. In the field device 21, the PHY2 detects a communication abnormality in the wiring L2 on the side of the field device 22 where a failure has occurred, and outputs a detection signal A2 to the CNT. Based on the detection signal A2 from the PHY2, the CNT notifies the controller 10 of a communication abnormality MSG1 from the PHY1 connected to the wiring L1 on the opposite side to the wiring L2 (first step).

[0029] In the controller 10, when the CNT receives MSG1 from the field device 21 via PHY1, it shorts the power supply switch SW2 by the switching signal SP as shown in Fig. 3. This starts the supply of backup power in the reverse direction from the controller 10 to the field devices 2n, ..., 22 in this order via the ring wiring L, and the operation of the field devices 2n, ..., 22 is resumed (second step).

[0030] Thereafter, as shown in FIG. 4, when the fault in the ring wiring L connecting the field devices 21, 22 is restored, the supply of power is resumed in the forward direction from the controller 10 via the ring wiring L to the field devices 21, 22, ..., 2n in that order, and the operation of the field devices 22, ..., 2n is maintained. In addition, in the field device 21, the PHY2 detects the communication recovery of the wiring L2 on the side of the field device 22 where the failure occurred, and outputs a detection signal A2 to the CNT. Based on the detection signal A2 from the PHY2, the CNT notifies the controller 10 of the communication recovery MSG2 from both the PHY1 and PHY2 connected to the wirings L1 and L2 (third step).

[0031] In the controller 10, when the CNT receives both MSG2 from the field device 21 via PHY1 and PHY2, the power supply switch SW2 is opened by the switching signal SP as shown in Fig. 5. This stops the supply of backup power from the controller 10, and the operation state returns to that during normal operation (fourth step).

[0032] The communication restoration MSG2 is transmitted from the field device 21 through both the wirings L1 and L2, i.e., the ring wiring L in both the forward and reverse directions, and is then notified to the controller 10. Therefore, the controller 10 can confirm the normality of the ring wiring L and each field device 20 by receiving and confirming both of these MSG2. Note that in an application in which such confirmation is not required, the MSG2 may be transmitted to only one of the wirings L1 and L2. In this case, if the MSG2 is transmitted so as to pass through the location where the failure occurred, the normality of the ring wiring L and each field device 20 in at least the section where the power supply interruption occurred can be confirmed.

[0033] [Advantages of this embodiment] In this manner, in this embodiment, when a field device 20 detects a communication abnormality on one side of the ring wiring L connected to the field device 20, the field device 20 notifies the controller 10 of the communication abnormality MSG1 from the other side, and when the controller 10 is notified of the communication abnormality MSG1 from one of the field devices 20, the controller 10 starts supplying backup power from the ring wiring L connected to the field device 20 opposite to the side that received the communication abnormality.

[0034] As a result, when the power supply in the forward direction through the ring wiring L during normal operation is stopped due to the occurrence of a fault, backup power is supplied in the reverse direction to the field device 20 to which the power supply has been stopped through the ring wiring L. Therefore, even with the ring wiring L, it is possible to achieve redundancy for both communication and power without requiring complex circuits.

[0035] In addition, in this embodiment, when the field device 20 detects communication restoration on either side of the ring wiring L connected to the field device 20, it may be configured to notify the controller 10 of communication restoration MSG2, and when the controller 10 receives the communication restoration MSG2 from one of the field devices 20, it may be configured to stop the supply of backup power from the opposite side. As a result, when communication is restored, the supply of backup power from the controller 10 is automatically stopped, and the normal operating state can be restored.

[0036] In this embodiment, when the field device 20 notifies the communication recovery MSG2, the field device 20 may be configured to notify the communication recovery MSG2 from both sides of the ring wiring L connected to the field device 20. When the field device 20 notifies the communication recovery MSG2 from both sides of the ring wiring L connected to the field device 20, the controller 10 may be configured to stop the supply of backup power from the opposite side. As a result, the controller 10 can confirm the normality of the ring wiring L and each field device 20 by receiving and confirming both of these MSG2 messages.

[0037] [Extended embodiment] Although the present invention has been described above with reference to the embodiment, the present invention is not limited to the above embodiment. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. [Explanation of symbols]

[0038] 1... power superposition communication system, 10... controller, 20, 21, 22, 2n... field devices, PHY1, PHY2... physical layer interface, PS... power supply circuit, CNT... control circuit, SW1, SW2... power supply switch, L... ring wiring, L1, L2... wiring, T1, T2... terminal, SP... switching signal, A1, A2... detection signal.

Claims

1. A controller configured to supply power and communicate via a ring wiring; a plurality of field devices that are daisy-chained in a ring shape via the ring wiring, operate on power supplied from the controller via the ring wiring, and communicate with the controller and other field devices via the ring wiring; When each of the plurality of field devices detects a communication abnormality on one side of the ring wiring connected thereto, the field device notifies the controller of the communication abnormality from the other side; In a power superposition communication system, when the controller is notified of the communication abnormality from any one of the plurality of field devices, the controller starts supplying power from an opposite side of the ring wiring connected to the controller to a side that has received the communication abnormality, When each of the plurality of field devices detects communication recovery on one side of the ring wiring connected to the field device, the field device notifies the controller of communication recovery; when the controller receives a notification of communication recovery from any one of the plurality of field devices, the controller stops supplying power from the opposite side; When each of the plurality of field devices notifies the communication recovery, the field devices notify the communication recovery from both sides of the ring wiring to which the field device is connected; When the controller is notified of the communication recovery from both sides of the ring wiring connected to the controller, the controller stops the supply of power from the opposite side. A power superposition communication system comprising:

2. A controller for use in the power superposition communication system according to claim 1.

3. A field device used in the power superposition communication system according to claim 1.

4. A power supply control method for use in a power superimposed communication system including a controller configured to supply power and perform communication via a ring wiring, and a plurality of field devices daisy-chained in a ring shape via the ring wiring, each field device operating on power supplied from the controller via the ring wiring and configured to communicate with the controller and other field devices via the ring wiring, comprising: a first step of notifying the controller of a communication abnormality from one side of the ring wiring to which each of the plurality of field devices is connected when the field devices detect the communication abnormality on the other side of the ring wiring; a second step of, when the controller is notified of the communication abnormality from any one of the plurality of field devices, starting to supply power from the ring wiring connected to the controller, the ring wiring being opposite to the side that has received the communication abnormality; a third step of notifying the controller of communication recovery when each of the plurality of field devices detects communication recovery on one side of the ring wiring connected to the field device; a fourth step of the controller stopping the supply of power from the opposite side when the communication abnormality is notified from any one of the plurality of field devices; Equipped with When each of the plurality of field devices notifies the communication recovery, the field devices notify the communication recovery from both sides of the ring wiring connected to the field device; When the controller is notified of the communication recovery from both sides of the ring wiring connected to the controller, the controller stops the supply of power from the opposite side. A power supply control method comprising:

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