JP2019022106A - Communication system - Google Patents

Abstract

To make it easy to appropriately set an initial value of a time-out time for a master apparatus.SOLUTION: A master apparatus comprises: a communication control unit 22 that performs retransmission processing on a request command when no response messages have not been received within a time-out time after transmission of the request command to a slave apparatus; a communication parameter database 260 that stores a communication history of data requests; an information acquisition unit 27 that when no initial value for the time-out time is set at the time of start-up of the master apparatus, acquires, from another master apparatus whose time-out time has already set, information on the time-out time; a time-out time calculation unit 28 that, on the basis of the acquired time-out time and the number of other master apparatuses, calculates an initial value for the time-out time; and a time-out time setting unit 29 that sets the initial value for the time-out time to the communication parameter database 260.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a master-slave communication system that performs communication between a master device and a slave device.

  The control network communication performed by the communication gateway is a command-response system in which a master device (communication gateway) transmits a request and a slave device (PLC (Programmable Logic Controller) or the like) returns a response. In this communication, a response reception timeout time after request transmission is set on the master device side to perform timeout monitoring. If the master device fails to receive a response within the time-out period, it performs request retransmission, and if there is no response from the slave device even after performing a predetermined number of request retransmissions, it determines a communication error.

  In order to set the optimum timeout time for the master device, adjustment is required while actually communicating with the slave device. However, when there are multiple master devices and slave devices on the network as in a process control system, the response time of the slave devices varies depending on the number of master devices communicating with the slave devices. It was difficult to set the timeout time, and the timeout time was often determined sensuously and empirically.

  As a known technique for setting the timeout time when there is one master device, there are techniques disclosed in Patent Document 1 and Patent Document 2. The techniques disclosed in Patent Document 1 and Patent Document 2 actually communicate with a slave device and determine a timeout time based on a response time from when a request is transmitted until a response to the request is received. As described above, in the techniques disclosed in Patent Document 1 and Patent Document 2, in order to determine the timeout time while actually communicating with the slave device, at the same time as adding the master device to the control network, There is a problem that it is difficult to set an appropriate timeout time considering the number of master devices.

Japanese Patent Laid-Open No. 9-18545 JP-A-6-121002

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a communication system that can easily set an appropriate initial value of the timeout time of a master device without communicating with a slave device. To do.

  The communication system of the present invention includes a plurality of master devices configured to transmit a request command, and a response message connected to the master device via a network and including data requested by the request command. At least one slave device configured to return to the master device, wherein the master device transmits the request command to the requested slave device, and within a timeout period after transmitting the request command A communication control unit configured to perform retransmission processing of the request command when the response message cannot be received, a communication parameter database configured to store a communication history of a data request, and activation of a master device If the initial value of the timeout period is not set at Based on the information acquisition unit configured to acquire the timeout time information from other set master devices, the timeout time acquired by the information acquisition unit and the number of the other master devices, A first time-out time calculating unit configured to calculate an initial value of the time-out time; and a time-out time setting unit configured to set the initial value of the time-out time in the communication parameter database. It is a feature.

Further, in one configuration example of the communication system of the present invention, the master device is configured to calculate a new timeout time based on a response time from when the request command is transmitted until the response message is received. The latest time-out value is set by recording the second time-out time calculating unit and the communication history including the time-out time calculated by the second time-out time calculating unit in the communication parameter database. A communication history recording unit configured as described above, wherein the information acquisition unit acquires the time-out time information by acquiring a communication history recorded in a communication parameter database of the other master device. It is a feature.
In the configuration example of the communication system of the present invention, the communication history recording unit includes the number of data requested by the request command, the timeout time calculated by the second timeout time calculation unit, and the requested slave device. The communication history including at least the information of the communication history is recorded in the communication parameter database, and the first timeout time calculation unit includes a maximum value and a minimum of the timeout time included in the communication history acquired by the information acquisition unit. Based on the value, the maximum and minimum values of the number of data included in the communication history, the number of the other master devices, and the number of data requested by the request command to be issued. The initial value of the corresponding timeout time is calculated.
Further, in one configuration example of the communication system of the present invention, the first timeout time calculation unit has an operation period of the longest operation duration of the other master device among the communication histories acquired by the information acquisition unit. The communication history recorded sometimes is used for calculating the initial value of the timeout time.

  According to the present invention, a new master device in which an initial value of the timeout time is not set acquires time-out time information from an existing master device in which the timeout time is already set, and the acquired information and the existing Since the initial value of the timeout time is calculated based on the number of master devices, the timeout time of the new master device is considered appropriate considering the number of existing master devices without communicating with the slave devices. A simple initial value can be set easily.

FIG. 1 is a block diagram showing a configuration of a communication system according to an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of the master device of the communication system according to the embodiment of the present invention. FIG. 3 is a flowchart for explaining the operation of the existing master device of the communication system according to the embodiment of the present invention. FIG. 4 is a diagram illustrating an example of a communication history recorded in the communication parameter database. FIG. 5 is a flowchart for explaining the operation of the master device newly added to the network in the embodiment of the present invention. FIG. 6 is a diagram illustrating an example of the contents of the communication parameter database of the master device when the initial value of the timeout time is set.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a communication system according to an embodiment of the present invention. The communication system according to the present embodiment includes at least one slave device 1-1 and 1-2 including, for example, a PLC, and a plurality of master devices 2-1, 2-2, 2-3 including, for example, a communication gateway. The network includes a slave device 1-1 and 1-2 and a network 3 that connects the master devices 2-1 to 2-3 with each other.

  FIG. 2 is a block diagram showing the configuration of the master device 2-1. The master device 2-1 includes a transmission unit 20 that transmits a request command to the slave devices 1-1 and 1-2, and a reception unit 21 that receives a response message from the slave devices 1-1 and 1-2 with respect to the request command. The request command is transmitted to the requesting slave devices 1-1 and 1-2 via the transmission unit 20, and the request command is retransmitted when the response message is not received within the timeout period after the request command is transmitted. A communication control unit 22 that performs processing, an elapsed time measurement unit 23 that measures an elapsed time from when the request command is transmitted, and a new response time based on the response time from when the request command is transmitted until the response message is received. A timeout time calculation unit 24 for calculating a timeout time, and a communication history including the timeout time calculated by the timeout time calculation unit 24 A communication history recording unit 25 that sets the latest value of the timeout time by recording in the communication parameter database (hereinafter referred to as communication parameter DB) 260, and a storage unit that stores information on the request command to be issued and the communication parameter DB 260 26, an information acquisition unit 27 for acquiring a communication history from another master device for which a timeout time has already been set when an initial value of the timeout time is not set when the master device 2-1 is started, and information acquisition Based on the timeout time acquired by the unit 27 and the number of other master devices, a timeout time calculation unit 28 that calculates an initial value of the timeout time, and a timeout time setting that sets the initial value of the timeout time in the communication parameter DB 260 When the operation is continued after the unit 29 and the master device 2-1 are activated And a continuous operation time measurement unit 30 for measuring the. The configuration of the master devices 2-2 and 2-3 is the same as that of the master device 2-1.

  Hereinafter, the operation of the communication system of the present embodiment will be described. In the present embodiment, a case will be described in which the master devices 2-1 and 2-2 are existing devices for which a timeout time has already been set, and the master device 2-3 is a device newly added to the network 3.

  FIG. 3 is a flowchart for explaining the operation of the master device 2-1. In the storage unit 26 of the master device 2-1, data request information to be issued (requested data type, number of data, request destination slave device information) is registered in advance. The communication control unit 22 of the master device 2-1 generates a request command for requesting data from the slave device 1-1 or 1-2 according to the information of the data request to be issued, and sends the request command to the transmission unit. 20 to the requested slave device 1-1 or 1-2 (step S100 in FIG. 3).

After transmitting the request command, the communication control unit 22 waits for a response from the requested slave device 1-1 or 1-2. The elapsed time measuring unit 23 of the master device 2-1 measures the elapsed time from when the request command is transmitted (step S101 in FIG. 3).
The slave device 1-1 or 1-2 that has received the request command returns a response message including data requested by the request command to the requesting master device 2-1.

  When the elapsed time measured by the elapsed time measuring unit 23 is within the timeout time T, the communication control unit 22 of the master device 2-1 receives a response from the requesting slave device 1-1 or 1-2. If a message is received (YES in steps S102 and S103 in FIG. 3), it is determined that the current data request has been completed. Note that the timeout time T is set for each requesting slave device and each type of data request. Therefore, the communication control unit 22 refers to a communication parameter DB 260 of the storage unit 26 to be described later, acquires a value of the timeout time T corresponding to the slave device of the current request destination and the type of data request of the current time, The determinations in S102 and S103 are made.

  After the data request is completed, the timeout time calculation unit 24 of the master device 2-1 transmits the request command and receives the response message Tr (measured by the elapsed time measurement unit 23 until the response message is received). The new timeout time T is calculated based on the elapsed time) (step S104 in FIG. 3). As disclosed in Patent Document 1, the timeout time calculation unit 24 calculates an average value and a variance value of the response time Tr from the response time Tr of a plurality of past data requests and the response time Tr of the current data request. The new timeout time T may be obtained by adding the value obtained by multiplying the average value by a predetermined multiple of the variance value.

  Further, as disclosed in Patent Document 2, the timeout time calculation unit 24 may use a value obtained by adding a predetermined margin to the response time Tr of the current data request as a new timeout time T, or a plurality of past multiple times. The average value of the response time Tr may be obtained from the response time Tr of the data request for the first time and the response time Tr of the current data request, and a value obtained by adding a predetermined margin to the average value may be used as the new timeout time T. Needless to say, the calculation method of the timeout time T is not limited to the above method.

  As described above, the timeout time T is set for each requesting slave device and each type of data request. Therefore, as described above, when the response time Tr of a plurality of past data requests is used for calculating the timeout time T together with the response time Tr of the current data request, the slave device of the current data request and the request destination The response times Tr of data requests that are the same and request the same type of data (number of data) are used.

  The communication history recording unit 25 of the master device 2-1 records the communication history of the current data request in the communication parameter DB 260 stored in the storage unit 26 of the master device 2-1 (step S105 in FIG. 3). The communication history identifies the number of data requested in the data request, the response time Tr measured by the elapsed time measurement unit 23, the timeout time T calculated by the timeout time calculation unit 24, and the requested slave device. Information to be included.

  FIG. 4 is a diagram illustrating an example of a communication history recorded in the communication parameter DB 260. The communication history is recorded for each requested slave device and each type of data request. In the example of FIG. 4, only one communication history is described for one type of data request. However, when the response time Tr of a plurality of data requests is used for calculating the timeout time T, the data request for each time is described. May be recorded in the communication parameter DB 260. However, the timeout time T used by the communication control unit 22 in the determinations in steps S102 and S103 is the latest value of the timeout times T corresponding to the current slave device and the type of data request.

  In the example of FIG. 4, the operation continuation time, which is the elapsed time since the master device 2-1 is activated, is recorded in the communication parameter DB 260. The operation duration measuring unit 30 measures the operation duration after the master device 2-1 is activated. The communication history recording unit 25 may appropriately update the value of the operation duration recorded in the communication parameter DB 260 according to the measurement result of the operation duration measurement unit 30.

  The storage unit 26 is a non-volatile memory that can retain information even when the power of the master device 2-1 is turned off. For this reason, the content of the created communication parameter DB 260 does not disappear, and a new communication history is added to the communication parameter DB 260 every time the master device 2-1 is activated.

  Next, when the elapsed time measured by the elapsed time measuring unit 23 is within the timeout time T, the timeout time calculating unit 24 of the master device 2-1 receives the request from the slave device 1-1 or 1. -2 cannot be received (NO in step S102 in FIG. 3), and the number of retransmissions of the request command is less than the predetermined number (YES in step S106 in FIG. 3), a predetermined coefficient α ( The value multiplied by α> 1) is updated as a new timeout time T (step S107 in FIG. 3). As described above, when the response message cannot be received within the timeout time T, the update is performed so that the timeout time T becomes longer.

Then, the communication control unit 22 of the master device 2-1 retransmits the same request command as that in step S100 to the request-destination slave device 1-1 or 1-2 (step S108 in FIG. 3).
The elapsed time measuring unit 23 of the master device 2-1 resets the elapsed time from when the request command is transmitted to 0, and starts measuring the elapsed time again (step S101).

  The operation of the communication control unit 22 in steps S102 and S103 is the same as described above. However, the timeout time T used for determination by the communication control unit 22 at this time is the value updated in step S107. Thus, until the response message can be received within the timeout time T, the request command is retransmitted while extending the timeout time T. When the response message is received within the timeout time T, the response time Tr at that time is used as a reference. The timeout time T is recalculated (step S104), and the communication history is recorded in the communication parameter DB 260 (step S105).

If the number of retransmissions of the request command reaches a predetermined number (NO in step S106), communication control unit 22 determines that the communication is abnormal (step S109 in FIG. 3), and ends the data request process.
The master device 2-1 performs the data request processing as described above for each data request to be issued. In the description here, the operation of the master device 2-1 is described, but the operation of the master device 2-2 is the same as that of the master device 2-1.

  In addition, when the master devices 2-1 and 2-2 are connected to the network 3 in a state where no other master device exists, the initial value of the timeout time T is set using the information of the other master devices as described later. Can't do it. Therefore, in such a case, a relatively large value may be manually set as the initial value of the timeout time T, or the initial value of the timeout time T may be set using the function of the timeout time calculation unit 24. When the initial value of the timeout time T is set using the function of the timeout time calculation unit 24, the determination in step S102 is skipped in the process described with reference to FIG. The initial value of the timeout time T may be calculated based on the above.

  Next, the operation of the master device 2-3 newly added to the network 3 will be described with reference to FIG. A timeout time T is not set for the newly added master device 2-3. Therefore, in this embodiment, the master device 2-3 automatically sets an optimal initial value of the timeout time T in cooperation with the existing master devices 2-1 and 2-2.

  When the master device 2-3 is activated, the information acquisition unit 27 of the master device 2-3 determines that the initial value of the timeout time T is not set in the communication parameter DB 260 of the master device 2-3. The contents of the communication parameters DB 2-1 and 2-2 are acquired (step S200 in FIG. 5). As described above, a new communication history is added to the communication parameter DB 260 every time the master devices 2-1 and 2-2 are activated, so the communication parameters DB 260 of the master devices 2-1 and 2-2 Different communication histories are recorded.

The timeout time calculation unit 28 of the master device 2-3 extracts the communication history having the longest operation continuation time from the contents of the communication parameter DB 260 acquired by the information acquisition unit 27. The timeout time calculation unit 28 then includes the maximum value Tmax of the timeout time T, the minimum value Tmin of the timeout time T, the maximum value Dmax of the number of data, the minimum value Dmin of the number of data, and the existing master included in the extracted communication history. Based on the number C of the devices 2-1 and 2-2 and the number D of data requested to the slave devices 1-1 and 1-2 in the data request to be issued, the timeout time T corresponding to the data request is determined. An initial value is calculated for each requested slave device (step S201 in FIG. 5).
T = {(Tmax−Tmin) / (Dmax−Dmin) × (D−Dmin)
× (C + 1) / C} + Tmin (1)

The number C is the number of master devices 2-1 and 2-2 with which the information acquisition unit 27 of the master device 2-3 communicates.
In the example of FIG. 4, regarding the slave device 1-1, Tmax = 240 ms, Tmin = 200 ms, Dmax = 56, Dmin = 45, and the number of existing master devices 2-1 and 2-2 is C = 2. . Therefore, if the number of data D requested to the slave device 1-1 in the data request to be issued is 50, for example, the time-out time T for this data request is 227 ms from the equation (1). Information on the data request to be issued is registered in the storage unit 26 in advance. Accordingly, the timeout time calculation unit 28 can calculate the initial value of the timeout time T for each type of data request scheduled to be issued and for each slave device requested.

  The reason for adopting the communication history with the longest operation duration among the contents of the communication parameter DB 260 acquired by the information acquisition unit 27 is to set the initial value of the timeout time T to an appropriate value. When there are a plurality of communication histories having the same operation duration time for the same slave device, any one of the plurality of communication histories may be used.

The timeout time setting unit 29 of the master device 2-3 masters the data request information (the number of data requested by the data request, the requested slave device) and the initial value of the timeout time T of the data request. It records in communication parameter DB260 of the memory | storage part 26 of the apparatus 2-3. In this way, the initial value of the timeout time T is set for each type of data request scheduled to be issued and for each requested slave device (step S202 in FIG. 5). FIG. 6 is a diagram showing an example of the contents of the communication parameter DB 260 of the master device 2-3 when the initial value of the timeout time T is set.
This completes the timeout time setting operation when the master device 2-3 newly added to the network 3 is first activated, and thereafter, the processing described with reference to FIG. 3 is performed.

  As described above, in this embodiment, the information on the timeout time T is acquired from the existing master devices 2-1 and 2-2 in which the timeout time T is already set, and the acquired information and the existing master device 2 are acquired. Since the initial value of the timeout time T set in the master device 2-3 is calculated based on the numbers of -1 and 2-2, communication with the slave devices 1-1 and 1-2 is not performed. Therefore, it is possible to easily set an appropriate initial value of the timeout time T of the master device 2-3 in consideration of the number of existing master devices 2-1, 2-2.

  In this embodiment, the present invention is applied to a control network to which process devices such as PLCs (slave devices 1-1 and 1-2) and communication gateways (master devices 2-1 to 2-3) are connected. However, the present invention is also applicable to other network communications.

  Each of the slave devices 1-1 and 1-2 and the master devices 2-1 to 2-3 of the present embodiment includes a CPU (Central Processing Unit), a storage device, a computer having an interface with the outside, and hardware of these devices. It can be realized by a program that controls hardware resources. The CPU of each device executes the processing described in the present embodiment in accordance with a program stored in the storage device.

  The present invention can be applied to a master-slave communication system.

  1-1, 1-2 ... slave device, 2-1 to 2-3 ... master device, 3 ... network, 20 ... transmission unit, 21 ... reception unit, 22 ... communication control unit, 23 ... elapsed time measurement unit, 24 , 28 ... timeout time calculation unit, 25 ... communication history recording unit, 26 ... storage unit, 27 ... information acquisition unit, 29 ... timeout time setting unit, 30 ... operation duration measurement unit, 260 ... communication parameter database.

Claims (4)

A plurality of master devices configured to send request commands;
At least one slave device connected to the master device via a network and configured to return a response message including data requested by the request command to the requesting master device;
The master device is
A communication configured to transmit the request command to the slave device that is the request destination, and to perform retransmission processing of the request command when the response message is not received within a timeout period after the request command is transmitted A control unit;
A communication parameter database configured to store a communication history of data requests;
An information acquisition unit configured to acquire information on timeout time from another master device in which the timeout time is already set when the initial value of the timeout time is not set when the master device is started;
A first timeout time calculating unit configured to calculate an initial value of the timeout time based on the timeout time acquired by the information acquisition unit and the number of the other master devices;
A communication system, comprising: a timeout time setting unit configured to set an initial value of the timeout time in the communication parameter database. The communication system according to claim 1, wherein
The master device is
A second timeout time calculating unit configured to calculate a new timeout time based on a response time from when the request command is transmitted until the response message is received;
A communication history recording unit configured to set the latest value of the timeout time by recording a communication history including the timeout time calculated by the second timeout time calculating unit in the communication parameter database; In addition,
The information acquisition unit acquires the time-out time information by acquiring a communication history recorded in a communication parameter database of the other master device. The communication system according to claim 2, wherein
The communication history recording unit includes the communication history including at least the number of data requested by the request command, the time-out time calculated by the second time-out time calculating unit, and information of a requested slave device. Recorded in the parameter database,
The first timeout time calculation unit includes a maximum value and a minimum value of the timeout time included in the communication history acquired by the information acquisition unit, and a maximum value and a minimum value of the number of data included in the communication history. And an initial value of the timeout time corresponding to the request command based on the number of the other master devices and the number of data requested by the request command to be issued. The communication system according to claim 2 or 3,
The first timeout time calculation unit is configured to display a communication history recorded during an operation period of the longest operation duration of the other master device among the communication histories acquired by the information acquisition unit as an initial value of the timeout time. A communication system characterized by being used for calculation of a value.

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