JP2022083142A - Control device, communication control method, and control program - Google Patents

Abstract

To provide a new mechanism that can achieve both making round-trip time obtained by a ring configuration to be short and stabilizing control when some kind of failure occurs in the ring configuration.SOLUTION: A control device includes a communication unit and an arithmetic processing unit connected to a network being configured such that communication frames go around. The arithmetic processing unit is configured so that a first operation mode and a second operation mode can be selected. In the first operation mode, the arithmetic processing unit updates preliminary input data with input data included in a received communication frame when receiving the communication frame transmitted within first threshold time. In the second operation mode, the arithmetic processing unit updates a preliminary input data with input data included in a received communication frame when receiving the communication frame transmitted within third threshold time longer than second threshold time.SELECTED DRAWING: Figure 12

Description

The present invention relates to a control device that can be connected to a network, a communication control method in the control device, and a control program for realizing the control device.

For example, in a network according to EtherCAT (registered trademark), a communication frame transmitted by a communication master (hereinafter, also simply referred to as “master”) circulates all communication slaves (hereinafter, also simply referred to as “slave”). Then, return to the master.

As a topology for patrolling a communication frame, in addition to the form in which a slave having a port for receiving and transmitting a communication frame exists on the path, the port of the slave existing on the path is used for receiving and transmitting the communication frame. It is possible to adopt a form in which only one is performed. For convenience of explanation, the former is referred to as a "non-ring configuration" and the latter is also referred to as a "ring configuration". In the ring configuration, the communication frame is transmitted in one direction on each of the cables connected to the slave. In addition, there may be an embodiment including both a ring configuration and a non-ring configuration.

Regarding such a ring configuration, Japanese Patent Application Laid-Open No. 2020-167554 (Patent Document 1) discloses a master device capable of easily knowing an illegal route in a network including a ring topology.

Further, in a network according to EtherCAT, it is necessary to consider in design the time required for the communication frame transmitted from the master to make a round and return to the master (hereinafter, also referred to as "round trip time"). More specifically, as the round trip time increases, the update cycle of the data exchanged between the communication master and the communication slave becomes long, and the control performance may deteriorate.

The round trip time increases as the number of communication slaves increases, but by adopting the ring configuration, it is possible to suppress the increase in the round trip time as compared with the case where the non-ring configuration is adopted.

Japanese Unexamined Patent Publication No. 2020-167554

The ring configuration is a kind of redundant network, and if some failure occurs in the network, the non-ring configuration network is automatically reconfigured and the transmission of communication frames is continued. However, as the network configuration changes, the round trip time may change in the direction of becoming longer.

An object of an aspect of the present invention is to provide a new mechanism capable of both shortening the round trip time obtained by the ring configuration and stabilizing control when some kind of failure occurs in the ring configuration.

A control device according to an embodiment of the present invention includes a communication unit connected to a network configured to make a cycle of communication frames, and a control operation based on input data included in the communication frame received via the communication unit. It also includes an arithmetic processing unit that repeatedly executes transmission of a communication frame including output data determined by the control operation every execution cycle. If the arithmetic processing unit does not receive the transmitted communication frame by the first threshold time after transmitting the communication frame, it is a backup data included in the communication frame received before the transmission. The transmitted communication frame must be received by the first operation mode in which the control operation is executed based on the input data and the second threshold time shorter than the first threshold time after the communication frame is transmitted. The second operation mode for executing the control operation based on the preliminary input data which is the input data included in the communication frame received before the transmission can be selected. If the arithmetic processing unit receives the transmitted communication frame by the first threshold time in the first operation mode, the arithmetic processing unit updates the preliminary input data with the input data included in the received communication frame, and the second If the transmitted communication frame is received by the third threshold time longer than the second threshold time in the operation mode of, the preliminary input data is updated with the input data included in the received communication frame.

According to this configuration, in the first operation mode, the input data to be used for the control calculation is determined and the preliminary input data is determined based on whether or not the communication frame transmitted by the first threshold time can be received. Judge the update of. On the other hand, in the second operation mode, the input data used for the control calculation is determined based on whether or not the communication frame transmitted by the second threshold time can be received, but the update of the preliminary input data is performed. , Communication frames received by the third threshold time, which is longer than the second threshold time, can be targeted. Therefore, in the second operation mode, even if the time from the transmission of the communication frame to the start of the execution of the control operation is set shorter than that in the first operation mode, the third threshold is set. If the communication frame can be received by the time, the preliminary input data can be updated appropriately. Therefore, it is possible to stabilize the control.

The network may include a ring configuration configured such that the communication frame is transmitted in only one direction on each of the cables connected to the communication slave. The arithmetic processing unit may be able to enable the second operation mode when the network includes a ring configuration. According to these configurations, it is possible to provide an operation mode suitable for the ring configuration. The network may include a daisy-chained configuration.

In the ring configuration, the second threshold time may be determined based on the time required for the communication frame transmitted from the communication unit to make a round and return to the communication unit. The third threshold time is determined based on the time required for the communication frame transmitted from the communication unit to make a round and return to the communication unit when any of the cables included in the ring configuration cannot transmit the communication frame. You may. According to this configuration, it is possible to predict changes in the network configuration and determine an appropriate threshold time.

The ring configuration may include a communication unit and a relay device connected to a plurality of communication slaves. According to this configuration, a ring configuration having Junction Redundancy can be realized.

The communication unit may have a plurality of ports connected to different communication slaves. According to this configuration, a ring configuration having cable redundancy can be realized.

The execution cycle in the second operation mode may be set shorter than the execution cycle in the first operation mode. According to this configuration, it is possible to shorten the execution cycle of control operations and / or increase the amount of operations that can be executed.

It may be configured so that the operation mode of the arithmetic processing unit can be referred to by an instruction included in the user program executed by the arithmetic processing unit. According to this configuration, the processing can be easily different depending on the operation mode in the arithmetic processing unit.

According to another embodiment of the present invention, there is provided a communication control method executed by a control device including a communication unit connected to a network configured to make a cycle of communication frames. The communication control method is a step of executing input processing according to the operation mode selected from the first operation mode and the second operation mode, and control based on the input data included in the communication frame received via the communication unit. It includes a step of executing an operation and a step of transmitting a communication frame containing output data determined by a control operation. In the step of executing the input process, in the first operation mode, if the transmitted communication frame is not received by the first threshold time after the communication frame is transmitted, the communication frame received before the transmission is received. If the transmitted communication frame is received by the step of using the preliminary input data, which is the input data included in the above, for the control calculation and the first threshold time, the input data included in the received communication frame is used as a backup. Includes steps to update the input data. In the second operation mode, the step of executing the input process is such that if the transmitted communication frame is not received by the second threshold time shorter than the first threshold time after the communication frame is transmitted, the transmitted communication frame is not received. The step of using the preliminary input data, which is the input data included in the communication frame received before the transmission, for the control calculation, and the transmitted communication frame by the third threshold time longer than the second threshold time. If received, it includes a step of updating the preliminary input data with the input data included in the received communication frame.

According to still another embodiment of the present invention, there is provided a control program executed by a computer including a communication unit connected to a network configured to make a cycle of communication frames. The control program is based on a step of executing input processing to the computer according to the operation mode selected from the first operation mode and the second operation mode, and input data included in the communication frame received through the communication unit. The step of executing the control operation and the step of transmitting the communication frame including the output data determined by the control operation are executed. In the step of executing the input process, in the first operation mode, if the transmitted communication frame is not received by the first threshold time after the communication frame is transmitted, the communication frame received before the transmission is received. If the transmitted communication frame is received by the step of using the preliminary input data, which is the input data included in the above, for the control calculation and the first threshold time, the input data included in the received communication frame is used as a backup. Includes steps to update the input data. In the second operation mode, the step of executing the input process is such that if the transmitted communication frame is not received by the second threshold time shorter than the first threshold time after the communication frame is transmitted, the transmitted communication frame is not received. The step of using the preliminary input data, which is the input data included in the communication frame received before the transmission, for the control calculation, and the transmitted communication frame by the third threshold time longer than the second threshold time. If received, it includes a step of updating the preliminary input data with the input data included in the received communication frame.

According to an embodiment of the present invention, it is possible to achieve both a reduction in the round trip time obtained by the ring configuration and a stabilization of control when some kind of failure occurs in the ring configuration.

It is a schematic diagram which shows an example of the control system according to this embodiment. It is a schematic diagram which shows an example of the processing in PLC of the control system according to this embodiment. It is a schematic diagram which shows another example of the processing in PLC of the control system according to this embodiment. It is a schematic diagram which shows still another example of the processing in PLC of the control system according to this embodiment. It is a schematic diagram which shows the hardware configuration example of PLC of the control system according to this embodiment. It is a schematic diagram which shows the hardware configuration example of the device of the control system according to this embodiment. It is a schematic diagram which shows the hardware configuration example of the relay device of the control system according to this embodiment. It is a figure for demonstrating the processing about the communication time in the control system according to this embodiment. It is a figure for demonstrating the example of the input processing in PLC of the control system according to this embodiment. It is a flowchart which shows the processing procedure in the data synchronization priority mode by PLC of the control system according to this embodiment. It is a flowchart which shows the processing procedure in the control performance priority mode by PLC of the control system according to this embodiment. It is a time chart which shows the operation example of the control system according to this embodiment. It is a schematic diagram which shows the hardware configuration example of the support device of the control system according to this embodiment. It is a schematic diagram which shows an example of the user interface screen provided by the support apparatus of the control system according to this embodiment. It is a figure which shows an example of the ring structure which can be adopted in the control system which follows this embodiment.

Embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

<A. Application example>
First, an example of a situation in which the present invention is applied will be described with reference to FIGS. 1 to 3.

FIG. 1 is a schematic diagram showing an example of a control system according to the present embodiment. The control system 1 shown in FIGS. 1A to 1C is an example of a control device that functions as a communication master (master), a PLC100, and a device 200 such as an input / output device that functions as a communication slave (slave). -1 to 200-5 (hereinafter, also collectively referred to as "device 200") and a relay device 300 are included.

As used herein, "ring configuration" means a network configured such that communication frames are transmitted in only one direction on each of the cables connected to the slave. In other words, each of the slaves has a plurality of ports, and one port means a "ring configuration" in which only one of transmission and reception of a communication frame is performed.

On the other hand, the "non-ring configuration" in the present specification means a network configured so that a communication frame is transmitted in both directions in any cable connected to a slave. In other words, a configuration in which one of the ports of the slave performs both transmission and reception of communication frames means a "non-ring configuration".

With respect to the network of the control system 1, the PLC 100 has a port 151 for transmitting and receiving communication frames. Each of the devices 200-1 to 200-5 has a first port 251 and a second port 252 for transmitting and receiving communication frames. Basically, the first port 251 is a port (IN port) to which a communication frame is input, and the second port 252 is a port (OUT port) to which a communication frame is output.

The relay device 300 has a first port 351 and a second port 352 and a third port 353 for transmitting and receiving communication frames. When the relay device 300 receives a communication frame at a certain port, the relay device 300 transmits the received frame from another port determined according to a predetermined rule. In the example shown in FIG. 1, as a predetermined rule, the first port 351 → the second port 352 → the third port 353 → the first port 351 → ... may be determined cyclically.

FIG. 1A shows an example of a ring configuration. The communication frame transmitted from the port 151 of the PLC 100 is the cable 20, the first port 351 of the relay device 300, the second port 352 of the relay device 300, the cable 21, the first port 251 of the device 200-1, and the device 200-1. 2nd port 252, cable 22, 1st port 251 of device 200-2, 2nd port 252 of device 200-2, cable 23, 1st port 251 of device 200-3, 2nd port of device 200-3 252, cable 24, first port 251 of device 200-4, second port 252 of device 200-4, cable 25, first port 251 of device 200-5, second port 252 of device 200-5, cable 26 , The third port 353 of the relay device 300 and the cable 20 make a round in this order, and return to the port 151 of the PLC 100. In this case, the number of passages of the communication frame port transmitted from the port 151 of the PLC 100 is 14.

On the other hand, FIG. 1B shows a case where the cable 24 connecting the device 200-3 and the device 200-4 is disconnected for some reason. In this case, since the communication frame cannot be transmitted from the second port 252 of the device 200-3, the device 200-3 transmits the communication frame from the first port 251. That is, the device 200-3 returns the communication frame by the same route. After that, the communication frame includes the cable 23, the second port 252 of the device 200-2, the first port 251 of the device 200-2, the cable 22, the second port 252 of the device 200-1, and the first port of the device 200-1. 251, the second port 352 of the relay device 300, the third port 353 of the relay device 300, the cable 26, the second port 252 of the device 200-5, the first port 251 of the device 200-5, the cable 25, the device 200-4. 2nd port 252, cable 25, 1st port 251 of device 200-5, 2nd port 252 of device 200-5, cable 26, 3rd port 353 of relay device 300, and port 151 of PLC100 in this order. Return to. In this case, the number of passages of the communication frame port transmitted from the port 151 of the PLC 100 is 22.

FIG. 1C shows an example of a non-ring configuration. The communication frame transmitted from the port 151 of the PLC 100 is the cable 20, the first port 351 of the relay device 300, the second port 352 of the relay device 300, the cable 21, the first port 251 of the device 200-1, and the device 200-1. 2nd port 252, cable 22, 1st port 251 of device 200-2, 2nd port 252 of device 200-2, cable 23, 1st port 251 of device 200-3, 2nd port of device 200-3 252, cable 24, first port 251 of device 200-4, cable 24, second port 252 of device 200-3, first port 251 of device 200-3, cable 23, second port 252 of device 200-2. , The first port 251 of the device 200-2, the cable 22, the second port 252 of the device 200-1, the first port 251 of the device 200-1, the cable 21, the second port 352 of the relay device 300, the relay device 300. It goes around the first port 351 and the cable 20 in this order, and returns to the port 151 of the PLC100. In this case, the number of passages of the communication frame port transmitted from the port 151 of the PLC 100 is 22.

The round trip time is determined by the sum of the port transit time and the cable transit time, but the port transit time is the dominant factor. Therefore, as the number of ports through which the communication frame passes increases, the round trip time increases. The round trip time Tr2 (Tr2> Tr1) in the configuration shown in FIG. 1B is longer than the round trip time Tr1 in the ring configuration shown in FIG. 1 (A). Since the number of passing ports is the same, the round trip time Tr2 in the configuration shown in FIG. 1 (B) is substantially the same as the round trip time Tr3 in the configuration shown in FIG. 1 (C) (Tr2≈Tr3).

That is, if the system is designed on the premise of the round trip time in the ring configuration, if some failure occurs in the ring configuration and the system changes to the non-ring configuration, the round trip time may be extended and the system may not operate as designed. There is also sex.

Therefore, the control system according to the present embodiment provides a mechanism capable of suppressing the influence on the control performance even when the ring configuration is changed to the non-ring configuration. The communication control method provided by the control system according to the present embodiment is not applied only when the ring configuration is changed to the non-ring configuration, but can be applied to various network configurations.

First, the system design will be described. FIG. 2 is a schematic diagram showing an example of processing in PLC100 of the control system 1 according to the present embodiment.

With reference to FIGS. 2 (A) to 2 (C), the PLC 100 periodically executes a series of processes including a control operation 160, an output process 162, and an input process 164. Hereinafter, the cycle in which a series of processes are executed is also referred to as a “task execution cycle”.

The input process 164 is a process of collecting input data such as measured values from the device 200. The control operation 160 performs an operation for controlling a control target based on the input data collected by the input process 164, and determines output data such as a command value to the device 200. The output process 162 is a process of transmitting the output data determined by the control operation 160 to the target device 200. As described above, the arithmetic processing unit (processor 102 shown in FIG. 5) of the PLC 100 is determined by the control arithmetic 160 and the control arithmetic 160 based on the input data included in the communication frame received via the field network controller 112. The transmission of the communication frame including the output data is repeatedly executed every task execution cycle.

The output process 162 and the input process 164 are realized by using the communication frame. Therefore, the time from the end of the output process 162 to the start of the input process 164 depends on the time from the transmission of the communication frame by the PLC 100 to the return of the communication frame, that is, the round trip time.

In FIGS. 2A to 2C, a non-ring configuration is assumed. FIG. 2A shows a time chart when the number of devices 200 connected to the PLC 100 and the calculation amount of the control calculation 160 are both relatively small. FIG. 2B shows a time chart when the number of devices 200 connected to the PLC 100 increases as compared with FIG. 2A.

Comparing FIG. 2A and FIG. 2B, as the number of connected devices 200 increases, the time from the end of the output process 162 to the start of the input process 164, that is, the communication time Tt1 (FIG. 2). It can be seen that 2 (A)) has increased to the communication time Tt2 (see FIG. 2B). This means a decrease in input / output response performance. However, since the amount of operation of the control operation 160 is relatively small, the task execution cycle Tc1 is maintained in any case.

FIG. 2C shows a time chart when the amount of operation of the control operation 160 is increased as compared with FIG. 2B. In FIG. 2C, since the processing time of the control calculation 160 increases as the amount of calculation increases, a task execution cycle Tc2 longer than the task execution cycle Tc1 is required. That is, as the number of connected devices 200 and the amount of calculation of the control calculation 160 increase, the task execution cycle is extended by ΔTc.

Therefore, it is preferable to shorten the communication time as much as possible. Here, by adopting a ring configuration instead of a non-ring configuration, the number of passages through the ports can be reduced, so that the round trip time, that is, the communication time can be shortened.

FIG. 3 is a schematic diagram showing another example of the processing of the control system 1 according to the present embodiment in the PLC100. FIG. 3A shows a time chart when a non-ring configuration is adopted, and FIG. 3B shows a time chart when a ring configuration is adopted, as in FIG. 2B.

Comparing FIG. 3A and FIG. 3B, the communication time Tt2 is shortened to the communication time Tt3 (<communication time Tt2), and when the task execution cycle Tc1 is set to be the same, the shortened communication is performed. The minute of time becomes the spare time 166, and more operations can be executed as the control operation 160.

As described above, by adopting the ring configuration, the communication time can be shortened, and thereby the control performance such as shortening the task execution cycle and executing more control operations can be improved. However, when a failure such as disconnection occurs in the network, the ring configuration changes to the non-ring configuration, and the communication time becomes long.

FIG. 4 is a schematic diagram showing still another example of the processing of the control system 1 according to the present embodiment in the PLC100. FIG. 4A shows a time chart when the ring configuration is adopted as in FIG. 3B, and FIG. 4B shows a time chart when the ring configuration is changed to the non-ring configuration. Is shown.

As shown in FIG. 4A, by adopting the ring configuration, the communication time Tt3 can be shortened, and even if the calculation amount of the control calculation 160 is relatively large, the control calculation 160, the output process 162, and the input A series of processes including the process 164 can be periodically executed in the task execution cycle Tc1.

On the other hand, when a failure such as disconnection occurs in the ring configuration, the ring configuration changes to a non-ring configuration, and as shown in FIG. 4B, the communication time Tt4 (> communication time Tt3) is extended. As a result, a series of processes including the control operation 160, the output process 162, and the input process 164 cannot be periodically executed in the task execution cycle Tc1 (this state is also referred to as “task execution cycle over” or the like. .).

In consideration of such a situation where the communication time increases, the system may be designed as shown in FIG. 4C on the premise of the communication time in the non-ring configuration. That is, in the time chart shown in FIG. 4C, the task execution cycle Tc3 is set with a certain time margin. However, in the system design shown in FIG. 4C, although it is robust, the merit of shortening the round trip time by adopting the ring configuration cannot be utilized.

In consideration of such background techniques, a new mechanism that can adopt any of the following design methods is provided in the control system according to the present embodiment.

(1) A system design assuming a round trip time in a non-ring configuration as shown in FIGS. 1 (C) and 4 (C).

(2) As shown in FIGS. 1 (B) and 4 (C), while setting the task execution cycle assuming the round trip time in the ring configuration as shown in FIGS. 1 (A) and 4 (B). A system design that enables a mode to suppress the effect on control performance even when the configuration changes to a non-ring configuration.

Hereinafter, the configuration, processing, functions, etc. for realizing such a mechanism will be described in detail.
<B. Hardware configuration example>
Next, a hardware configuration example of each device constituting the control system 1 according to the present embodiment will be described.

(B1: Control device (PLC100))
FIG. 5 is a schematic diagram showing a hardware configuration example of the PLC100 of the control system 1 according to the present embodiment. With reference to FIG. 5, the PLC 100 includes, as main hardware components, a processor 102, a main memory 104, a storage 110, a field network controller 112, and a local bus controller 114. These hardware components are electrically connected via the internal bus 118.

The processor 102 corresponds to an arithmetic processing unit that executes control operations, and is composed of a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), and the like. Specifically, the processor 102 reads out the program stored in the storage 110, expands it in the main memory 104, and executes it to realize control operations according to the control target and various processes as described later. do.

The main memory 104 is composed of a volatile storage device such as a DRAM (Dynamic Random Access Memory) or an SRAM (Static Random Access Memory). The storage 110 is composed of, for example, a non-volatile storage device such as an SSD (Solid State Drive) or an HDD (Hard Disk Drive).

The storage 110 stores a system program 1102 for realizing basic functions, a user program 1104 created according to a control target, a system setting information 1106 for determining a process as described later, and the like. To. The system program 1102 can be regarded as at least a part of the control program in order to realize the basic functions in the PLC 100.

The field network controller 112 corresponds to a communication unit and is connected to a network configured so that communication frames make a round. More specifically, the field network controller 112 has a port 151 and is in charge of transmission / reception processing of communication frames. The field network controller 112 of the PLC 100 functions as a communication master (master). The field network controller 112 may have a synchronization counter for periodically transmitting and receiving communication frames.

The local bus controller 114 is electrically connected to one or more functional units 116 via the internal bus 118. The functional unit 116 includes a function of exchanging various signals with a controlled object. The functional unit 116 has, for example, a DI (Digital Input) function for receiving a digital signal from a controlled object, a DO (Digital Output) function for outputting a digital signal to a controlled object, and an AI (Analog) function for receiving an analog signal from the controlled object. It has one or more of the Input) function and the AO (Analog Output) function that outputs an analog signal to the controlled object. Further, the functional unit 116 may include a controller equipped with special functions such as PID (Proportional Integral Derivative) control and motion control.

FIG. 5 shows a configuration example in which the necessary functions are provided by the processor 102 executing a program, and some or all of these provided functions are provided by a dedicated hardware circuit (for example, ASIC). (Application Specific Integrated Circuit) or FPGA (Field-Programmable Gate Array), etc.) may be used for implementation. Alternatively, the main part of the PLC 100 may be realized by using hardware that follows a general-purpose architecture (for example, an industrial personal computer based on a general-purpose personal computer). In this case, a virtualization technique may be used to execute a plurality of OSs (Operating Systems) having different uses in parallel, and to execute necessary applications on each OS.

Further, a configuration in which functions such as a display device and a support device are integrated into the PLC 100 may be adopted.

(B2: Device 200)
FIG. 6 is a schematic diagram showing a hardware configuration example of the device 200 of the control system 1 according to the present embodiment. With reference to FIG. 6, the device 200 includes, as main hardware components, a control circuit 206, a field network controller 212, and a functional module 220.

The control circuit 206 is an arithmetic processing unit that proactively executes processing in the device 200. The control circuit 206 typically includes a processor 202, a main memory 204, and a storage 210. The processor 202 is composed of a CPU, a GPU, and the like. The main memory 204 is composed of a volatile storage device such as DRAM or SRAM. The storage 210 is composed of, for example, a non-volatile storage device such as an SSD. A ROM (Read Only Memory) may be adopted as the storage 210.

The control circuit 206 may be mounted by using a dedicated hardware circuit (for example, ASIC or FPGA).

The field network controller 212 has a first port 251 and a second port 252, and is in charge of transmission / reception processing of communication frames. The field network controller 212 of the device 200 functions as a communication slave (slave). The field network controller 212 may have a synchronization counter for periodically transmitting and receiving communication frames.

Similar to the functional unit 116 shown in FIG. 5, the functional module 220 is in charge of processing for exchanging various signals with the controlled object.

(B3: Relay device 300)
FIG. 7 is a schematic diagram showing a hardware configuration example of the relay device 300 of the control system 1 according to the present embodiment. With reference to FIG. 7, the relay device 300 includes a control circuit 306 and a field network interface 312 as main hardware components.

The control circuit 306 is an arithmetic processing unit that independently executes the transfer processing of the communication frame in the relay device 300. The control circuit 306 typically includes a processor 302, a main memory 304, and a storage 310. The processor 302 is composed of a CPU, a GPU, and the like. The main memory 304 is composed of a volatile storage device such as DRAM or SRAM. The storage 310 is composed of, for example, a non-volatile storage device such as an SSD. A ROM may be adopted as the storage 310.

The control circuit 306 may be mounted using a dedicated hardware circuit (for example, ASIC or FPGA).

The field network interface 312 has a first port 351 and a second port 352 and a third port 353, and includes a receiving circuit and a transmitting circuit (not shown) of the communication frame.

<C. Communication frame transmission / reception processing>
As described above, when the ring configuration is adopted, the non-ring configuration may be changed due to an obstacle such as disconnection, and as a result, the round trip time may be extended. In addition, the communication frame that transmits the network may be damaged or disappear. Therefore, the PLC100, which is the master, does not return the communication frame within a predetermined time after transmitting a certain communication frame, the communication frame is damaged or disappears in the middle (hereinafter, also referred to as "frame lost"). Judge.

Therefore, when the non-ring configuration is adopted, the behavior of the communication frame transmitted from the master is as follows: (1) the communication frame returns to the master within a predetermined time, and (2) the communication frame is lost and the master. Two types are assumed, one that does not return to.

On the other hand, when the ring configuration is adopted, the behavior of the communication frame transmitted from the master is as follows: (1) the communication frame returns to the master within a predetermined time, and (2) the communication frame changes to a non-ring configuration. Three types are assumed: the communication frame returns to the master after a predetermined time, and (3) the communication frame is lost and does not return to the master.

FIG. 8 is a diagram for explaining a process related to communication time in the control system 1 according to the present embodiment. FIG. 8A shows an example of a non-ring configuration, and FIG. 8B shows an example of a ring configuration.

When a system design premised on a non-ring configuration is adopted with reference to FIG. 8A, the input process 164 starts from the end of the output process 162 regardless of whether the ring configuration is normal or not. The time until is set relatively long.

With reference to FIG. 8B, in a normal ring configuration, the communication frame transmitted from the PLC100 immediately after the end of the output process 162 returns to the PLC100 by the start of the input process 164 (FIG. 8B). "normal"). On the other hand, if some failure occurs in the ring configuration and the configuration changes to the non-ring configuration, the round trip time increases and the communication frame cannot return to the PLC 100 by the start of the input process 164 (FIG. 8 (B) "" delay").

Further, if the communication frame is damaged or disappears in the middle, the communication frame does not return to the PLC 100 (“frame lost” in FIG. 8 (B)). Even if the communication frame returns later than the "delay" in FIG. 8B, it may be handled in the same manner as the frame lost.

As described above, in the example shown in FIG. 8 (A), the concept of "delay" in FIG. 8 (B) does not exist, and the communication frame transmitted from the PLC 100 immediately after the end of the output process 162 starts the input process 164. There are cases where the PLC 100 is returned to (“normal” in FIG. 8 (A)) and cases in other cases (“frame lost” in FIG. 8 (A)).

Therefore, in the non-ring configuration of FIG. 8A, the threshold time Th1 is set with reference to the end timing T0 of the output process 162. On the other hand, in the ring configuration of FIG. 8B, the threshold time Th2 and the threshold time Th3 are set with reference to the end timing T0 of the output process 162. The threshold time Th1 and the threshold time Th3 correspond to the communication timeout time, and the threshold time Th2 corresponds to the threshold time for determining that some kind of failure has occurred in the ring configuration.

Here, the threshold time Th1 and the threshold time Th3 are determined based on the round trip time of the non-ring structure, and the threshold time Th2 is determined based on the round trip time of the ring configuration. The threshold time Th1 and the threshold time Th3 may have the same value or different values.

In the control system 1 according to the present embodiment, the processing is different for each of the three types of normal, delayed, and frame lost.

FIG. 9 is a diagram for explaining an example of the input process 164 in the PLC 100 of the control system 1 according to the present embodiment. With reference to FIG. 9, the data (hereinafter referred to as input data) from the device 200 or the like included in the communication frame returned to the PLC 100 is the current cycle input data 170 and the preliminary input data 172, which are independent of each other. It is held in the main memory 104.

The current cycle input data 170 is input data included in the communication frame received in the current task execution cycle. The preliminary input data 172 is input data included in the newest and appropriately received communication frame other than the current task execution cycle.

In the "normal" shown in FIGS. 8A and 8B, the current cycle input data 170 is used as input data in the control operation 160. On the other hand, in the "delay" shown in FIG. 8 (B) and the "frame lost" shown in FIGS. 8 (A) and 8 (B), the preliminary input data 172 is used as input data in the control operation 160. That is, in "delay" and "frame lost", the communication frame of the current task execution cycle cannot be used, so the control operation 160 is executed by using the communication frame received before that.

If it is "normal", the input data included in the communication frame received in the current task execution cycle is held as the current cycle input data 170 and also as the preliminary input data 172. That is, if it is "normal", the current cycle input data 170 and the preliminary input data 172 are the same input data.

On the other hand, in the case of "frame lost", since the communication frame cannot be received in the current task execution cycle, neither the current cycle input data 170 nor the preliminary input data 172 is updated and remains as it is.

On the other hand, in the case of "delay", since the communication frame cannot be received in the current task execution cycle, the current cycle input data 170 is not updated, but since the communication frame itself is received, it is used as the preliminary input data 172. Can be retained. Therefore, in the case of "delay", the input data included in the received communication frame is held as the preliminary input data 172 after the execution of the control operation 160.

As described above, in a control system that can adopt a ring configuration, as one of the system designs, it is possible to design assuming that the ring configuration changes to a non-ring configuration and the round trip time is extended (worst value). (See FIGS. 1 (C) and 4 (C), etc.). In this case, "normal" and "frame lost" may be considered without considering the "delay" shown in FIG. 8 (B). In such a system design, the input process 164 can be executed using the input data included in the communication frame received in each task execution cycle as long as the frame lost does not occur. Therefore, there is no time lag between the timing at which the input data is acquired and the execution timing of the input process 164. Focusing on such an advantage, the operation mode of the PLC100 in this case is referred to as a "data synchronization priority mode".

In the data synchronization priority mode, if the PLC 100 does not receive the transmitted communication frame by the threshold time Th1 (first threshold time) after the communication frame is transmitted, the PLC 100 receives the communication frame before the transmission. The control operation 160 is executed based on the preliminary input data 172 which is the input data included in the communication frame. With respect to the preliminary input data 172, if the PLC 100 receives the communication frame transmitted by the threshold time Th1, the PLC 100 updates the preliminary input data 172 with the input data included in the received communication frame.

On the other hand, the system can be designed on the premise of the round trip time obtained by the ring configuration. In this case, it is necessary to consider the "delay" shown in FIG. 8 (B). When the ring configuration is changed to the non-ring configuration, the input data used in the input process 164 is included in the communication frame received in the previous task execution cycle. That is, even if the ring configuration is changed to the non-ring configuration, the time lag between the timing at which the input data is acquired and the execution timing of the input process 164 can be suppressed to only one cycle of the task execution cycle. At this time, since the task execution cycle itself can be shortened, the control performance can be improved from the viewpoint of the input / output response performance and the calculation amount of the control calculation 160. Focusing on such an advantage, the operation mode of the PLC100 in this case is referred to as a "control performance priority mode".

In the control performance priority mode, if the PLC 100 does not receive the transmitted communication frame by the threshold time Th2 (second threshold time) after the communication frame is transmitted, the communication received before the transmission. The control operation 160 is executed based on the preliminary input data 172 which is the input data included in the frame. With respect to the preliminary input data 172, if the PLC100 receives a communication frame transmitted by a threshold time Th3 (third threshold time) longer than the threshold time Th2, the PLC100 reserves the input data included in the received communication frame. The input data 172 is updated.

As described above, the execution cycle in the control performance priority mode can be set shorter than the execution cycle in the data synchronization priority mode. In PLC100, the control performance priority mode may be enabled when the network includes a ring configuration.

<D. Processing procedure>
Next, the processing procedure in the PLC 100 for each of the above-mentioned data synchronization priority mode and control performance priority mode will be described. The PLC 100 periodically executes a process including an input process as described later according to an operation mode selected from the data synchronization priority mode and the control performance priority mode.

(D1: Data synchronization priority mode)
FIG. 10 is a flowchart showing a processing procedure in the data synchronization priority mode by the PLC 100 of the control system 1 according to the present embodiment. Each step shown in FIG. 10 is typically realized by the processor 102 of the PLC 100 executing the system program 1102 and the user program 1104 (see FIG. 5).

With reference to FIG. 10, the PLC 100 determines whether or not the task execution cycle has arrived (step S100). When the task execution cycle arrives (YES in step S100), the PLC 100 generates and transmits a communication frame including the output data calculated by the previous control operation (step S102). That is, the PLC 100 transmits a communication frame including output data determined by a control operation.

After that, the PLC 100 determines whether or not a communication frame that has circled the network has been received (step S104).

If the communication frame that has circled the network is received (YES in step S104), the PLC 100 stores the input data included in the received communication frame as the current cycle input data 170 (step S106), and uses the current cycle input data 170. And execute the control operation (step S108). At the same time, the PLC 100 updates the preliminary input data 172 with the current cycle input data 170 (step S110). As described above, if the PLC 100 receives the communication frame transmitted by the threshold time Th1 (first threshold time), the PLC 100 updates the preliminary input data 172 with the input data included in the received communication frame. Then, the processing of step S100 or less is repeated.

On the other hand, if the communication frame that has circled the network has not been received (NO in step S104), the PLC 100 determines whether or not the threshold time Th1 has elapsed since the communication frame was transmitted (step S112). If the threshold time Th1 has not elapsed (NO in step S112), the processing of step S104 or less is repeated.

If the threshold time Th1 has elapsed (YES in step S112), the PLC 100 selects the preliminary input data 172 as input data to be used for the control operation (step S114), and executes the control operation using the preliminary input data 172. (Step S116). As described above, if the PLC 100 does not receive the transmitted communication frame by the threshold time Th1 (first threshold time) after the communication frame is transmitted, it is included in the communication frame received before the transmission. The preliminary input data, which is the input data that has been stored, is used for the control calculation. At this time, the preliminary input data 172 is not updated. Then, the processing of step S100 or less is repeated.

(D2: Control performance priority mode)
FIG. 11 is a flowchart showing a processing procedure in the control performance priority mode by the PLC 100 of the control system 1 according to the present embodiment. Each step shown in FIG. 11 is typically realized by the processor 102 of the PLC 100 executing the system program 1102 and the user program 1104 (see FIG. 5).

With reference to FIG. 11, the PLC 100 determines whether or not the task execution cycle has arrived (step S200). When the task execution cycle arrives (YES in step S200), the PLC 100 generates and transmits a communication frame including the output data calculated by the previous control operation (step S202). That is, the PLC 100 transmits a communication frame including output data determined by a control operation.

After that, the PLC 100 determines whether or not a communication frame that has circled the network has been received (step S204).

If the communication frame that has circled the network is received (YES in step S204), the PLC 100 stores the input data included in the received communication frame as the current cycle input data 170 (step S206), and uses the current cycle input data 170. And execute the control operation (step S208). At the same time, the PLC 100 updates the preliminary input data 172 with the current cycle input data 170 (step S210). Then, the process of step S200 or less is repeated.

On the other hand, if the communication frame that has circled the network has not been received (NO in step S204), the PLC 100 determines whether or not the threshold time Th2 has elapsed since the communication frame was transmitted (step S212). If the threshold time Th2 has not elapsed (NO in step S212), the processing of step S204 or less is repeated.

If the threshold time Th2 has elapsed (YES in step S212), the PLC 100 selects the preliminary input data 172 as input data to be used for the control operation (step S214), and executes the control operation using the preliminary input data 172. (Step S216). As described above, if the PLC 100 does not receive the transmitted communication frame by the threshold time Th2 (second threshold time) after the communication frame is transmitted, it is included in the communication frame received before the transmission. The preliminary input data, which is the input data that has been stored, is used for the control calculation.

Further, the PLC 100 determines whether or not a communication frame that has circled the network has been received by the time the threshold time Th3 elapses (step S218). If the communication frame that has circled the network has been received by the time when the threshold time Th3 elapses (YES in step S218), the PLC 100 updates the preliminary input data 172 with the input data included in the received communication frame (YES in step S218). Step S220). As described above, if the PLC 100 receives the communication frame transmitted by the threshold time Th3 (third threshold time), the PLC 100 updates the preliminary input data 172 with the input data included in the received communication frame. Then, the process of step S200 or less is repeated.

On the other hand, if the communication frame that has circled the network has not been received by the time when the threshold time Th3 elapses (NO in step S218), the preliminary input data 172 is not updated, and the processing of step S100 or less is repeated.

<E. Operation example>
Next, an operation example in the control system 1 according to the present embodiment will be described.

FIG. 12 is a time chart showing an operation example of the control system 1 according to the present embodiment. FIG. 12A shows an operation example in the ring configuration. In the operation example shown in FIG. 12A, since the communication frame 30 makes a cycle from the end of the output process 162 to the start of the input process 164, the input data included in the communication frame 30 is the current cycle input data 170. Is stored as, and is used in the control operation 160 of the same task execution cycle.

On the other hand, FIG. 12B shows an operation example when the ring configuration is changed to the non-ring configuration. In the operation example shown in FIG. 12B, since the communication frame 30 cannot make a round between the end of the output process 162 and the start of the input process 164, the preliminary input data updated in the previous task execution cycle 172 is used in control operation 160. The input data included in the communication frame 30 received in the same task execution cycle is stored as preliminary input data 172 and is used in the control calculation 160 of the next task execution cycle.

FIG. 12C shows an operation example when the non-ring configuration is restored to the ring configuration. When the non-ring configuration is restored to the ring configuration, the communication frame 30 can make a round between the end of the output process 162 and the start of the input process 164. Along with this, instead of the preliminary input data 172 updated in the previous task execution cycle, the input data (current cycle input data 170) received in the communication frame 30 received in the same task execution cycle is in the control operation 160. Will be used.

As described above, in the control system 1 according to the present embodiment, even if the ring configuration is changed to the non-ring configuration or the non-ring configuration is changed to the ring configuration during the execution of the control operation, the control performance is improved. You can continue to execute control operations with the effect of.

<F. System design and user support>
Next, the configuration and processing for designing the system in the control system 1 according to the present embodiment will be described.

(F1: Support device)
The user program 1104 and system setting information 1106 stored in the PLC 100 can be created and set by using the support device 400 that can be connected to the PLC 100.

FIG. 13 is a schematic diagram showing a hardware configuration example of the support device 400 of the control system 1 according to the present embodiment. With reference to FIG. 13, the support device 400 is realized, for example, by using hardware (for example, a general-purpose personal computer) that follows a general-purpose architecture.

The support device 400 provides an integrated development environment in which the control system 1 can be set for the PLC 100 and the device 200, and the user program 1104 executed by the PLC 100 can be created in an integrated manner. In the integrated development environment, debugging and simulation may be possible.

With reference to FIG. 13, the support device 400 has, as main hardware components, a processor 402, a main memory 404, an input unit 406, a display unit 408, a storage 410, a communication controller 412, and an optical drive 416. , USB controller 424 and so on. These hardware components are electrically connected via the internal bus 228.

The processor 402 is composed of a CPU, a GPU, or the like, and realizes a function as a support device 400 by reading a program stored in the storage 410, expanding the program in the main memory 404, and executing the program.

The main memory 404 is composed of a volatile storage device such as DRAM or SRAM. The storage 410 is composed of, for example, a non-volatile storage device such as an HDD or SSD.

The storage 410 stores an OS 4102 for realizing basic functions, a development program 4104 for realizing an integrated development environment, and the like. The development program 4104 is executed by the processor 402 to provide an integrated development environment.

The input unit 406 is composed of a keyboard, a mouse, and the like, and receives user operations.
The display unit 408 is composed of a display, various indicators, and the like, and outputs a processing result from the processor 402 and the like.

The communication controller 412 exchanges data with an arbitrary information processing device via an arbitrary host network.

The optical drive 416 reads arbitrary data from a storage medium 418 (for example, an optical storage medium such as a DVD) that non-transiently stores a computer-readable program, and writes arbitrary data to the storage medium 418. Can be done.

The USB controller 424 exchanges data with an arbitrary information processing device via a USB connection.

The program stored in the storage medium 418 that temporarily stores the computer-readable program may be read and installed in the storage 410 or the like. Alternatively, various programs executed by the support device 400 may be installed by downloading from a server device or the like on the network. Further, the function provided by the support device 400 according to the present embodiment may be realized by using a part of the module provided by the OS 4102.

The support device 400 may be removed from the PLC 100 while the control system 1 is in operation.

(F2: threshold time)
The support device 400 may have a function of determining the above-mentioned threshold times Th1, Th2, Th3, respectively.

The threshold time Th1 (first threshold time) is a time for determining frame lost, and is determined based on the round trip time in the target network.

The threshold time Th2 (second threshold time) is determined based on the round trip time in a state where no obstacle has occurred in the ring configuration. That is, the threshold time Th1 is determined based on the time required for the communication frame transmitted from the field network controller 112 (communication unit) of the PLC 100 to make a round and return to the field network controller 112 (communication unit) in the ring configuration. To.

The threshold time Th3 (third threshold time) is determined based on the round trip time in a state where no obstacle is generated in the ring configuration. That is, in the threshold time Th3, the communication frame transmitted from the field network controller 112 (communication unit) goes around in a state where any of the cables included in the ring configuration cannot transmit the communication frame, and the field network controller 112 (communication). It is decided based on the time to return to the part).

For example, the support device 400 may measure the time required for the communication frame in the network of the control system 1 to make a round, and determine the threshold time Th2 and / or the threshold time Th3 based on the measured time. good.

Alternatively, the support device 400 may determine the threshold time Th2 and / or the threshold time Th3 by simulation. For example, the support device 400 has a threshold time Th1 and / or a threshold according to a predetermined calculation formula based on the number of devices 200 connected to the network and the information of the network connection form (network topology). The time Th2 may be determined.

(F3: User interface screen)
The user creates the user program 1104 by using the integrated development environment provided by the support device 400, and also makes various settings related to the control system 1. At this time, the support device 400 can estimate the execution time of the user program 1104 by simulation according to the user operation. Then, the support device 400 can also give advice to the user, such as changing the operation mode, based on the simulation result.

FIG. 14 is a schematic diagram showing an example of a user interface screen 450 provided by the support device 400 of the control system 1 according to the present embodiment. With reference to FIG. 14, the user interface screen 450 shows a graph 452 showing the execution time of the user program 1104 calculated in the current setting, and a user in the case where the control performance priority mode is adopted after changing the network configuration. Includes graph 454 showing execution time of program 1104. As the execution time shown in the graph 452, the measured value measured by the PLC 100 may be adopted.

By comparing the graph 452 and the graph 454, the user can grasp in advance how much the execution time (task execution cycle) of the user program 1104 can be shortened.

In the example of the user interface screen 450 shown in FIG. 14, a message such as "By changing to the ring configuration and selecting the control performance priority mode, the task execution cycle can be shortened from 2 ms to 1 ms" based on the simulation result. 460 is displayed.

The user refers to the message 460, changes the network configuration of the control system 1 from the non-ring configuration to the ring configuration, and then checks the check box 458 to enable the control performance priority mode. When the control performance priority mode is enabled, the user may be notified that data synchronization may be lost if any failure occurs in the network.

In the example shown in FIG. 14, the check box 456 is checked, and it can be seen that the data synchronization priority mode is selected.

(F4: Confirmation / acquisition of operation mode)
The operation mode of the PLC 100, the execution time of the user program 1104, and the like may be confirmed and acquired by any method.

Typically, the support device 400 is connected to the PLC 100, and the operation mode of the PLC 100 (whether the data synchronization priority mode or the control performance priority mode is k) and the execution of the user program 1104 are performed on the support device 400. It may be possible to monitor the time and the like.

Further, an HMI (Human Machine Interface) may be provided in the control system 1 so that the operation mode of the PLC 100 and the execution time of the user program 1104 may be displayed on the HMI.

Further, by using the system variables or special events held by the PLC 100, the operation mode of the PLC 100 and the execution time of the user program 1104 can be acquired by the dedicated instruction included in the user program 1104. good. In this way, the current operation mode may be referred to by the instruction included in the user program 1104 executed by the PLC 100. For example, it is possible to create a user program 1104 that makes the input processing different depending on the operation mode of the PLC 100.

<G. Variations of ring configuration>
In the above description, an example of a ring configuration using the relay device 300 has been described, but the present invention is not limited to this, and other configurations may be adopted.

FIG. 15 is a diagram showing an example of a ring configuration that can be adopted in the control system 1 according to the present embodiment.

FIG. 15A shows an example of a ring configuration using a relay device 300 having three or more ports. The relay device 300 has three or more ports to provide Junction Redundancy. The ring configuration shown in FIG. 15A includes a field network controller 112 (communication unit) of the PLC 100 and a relay device 300 connected to a plurality of devices 200 (slave).

FIG. 15B shows an example of a ring configuration using a PLC100 having two or more ports 151 and 152. The PLC 100 has two or more ports to provide cable redundancy. In the ring configuration shown in FIG. 15B, the field network controller 112 (communication unit) of the PLC 100 has a plurality of ports connected to different devices 200 (slave).

Further, the relay device 300 shown in FIG. 15A and the PLC100 shown in FIG. 15B may be arbitrarily combined to form a ring configuration.

The communication control method according to the present embodiment is applicable to any ring configuration, not limited to the configuration example described above. Further, the communication protocol is not limited to EtherCAT, and can be applied to various communication protocols for industrial networks having punctuality.

<H. Addendum>
The present embodiment as described above includes the following technical ideas.
[Structure 1]
A communication unit (112) connected to a network configured so that the communication frame (30) makes a round, and
The control operation (160) based on the input data included in the communication frame received via the communication unit and the transmission (164) of the communication frame including the output data determined by the control operation are repeated for each execution cycle. It is equipped with an arithmetic processing unit (102) to be executed.
The arithmetic processing unit is
If the transmitted communication frame is not received by the first threshold time (Th1) after the communication frame is transmitted, the preliminary input data which is the input data included in the communication frame received before the transmission. The first operation mode for executing the control operation based on (172) and
If the transmitted communication frame is not received by the second threshold time (Th2) shorter than the first threshold time after the communication frame is transmitted, it is included in the communication frame received before the transmission. It is configured so that it can be selected from the second operation mode in which the control operation is executed based on the preliminary input data (172) which is the input data.
The arithmetic processing unit is
If the transmitted communication frame is received by the first threshold time in the first operation mode, the preliminary input data is updated with the input data included in the received communication frame.
In the second operation mode, if the transmitted communication frame is received by the third threshold time (Th3) longer than the second threshold time, the input data included in the received communication frame is used as the input data. A control device (100) that updates the preliminary input data.
[Structure 2]
The control device according to configuration 1, wherein the network includes a ring configuration configured such that a communication frame is transmitted in only one direction in each of the cables (21 to 26) connected to the communication slave.
[Structure 3]
The control device according to configuration 2, wherein the arithmetic processing unit can enable the second operation mode when the network includes the ring configuration.
[Structure 4]
The second threshold time is determined based on the time required for the communication frame transmitted from the communication unit to make a round and return to the communication unit in the ring configuration.
The third threshold time is the time until the communication frame transmitted from the communication unit makes a round and returns to the communication unit in a state where any of the cables included in the ring configuration cannot transmit the communication frame. The control device according to configuration 2 or 3, which is determined based on the above.
[Structure 5]
The control device according to any one of configurations 2 to 4, wherein the ring configuration includes a relay device (300) connected to the communication unit and a plurality of communication slaves (200).
[Structure 6]
The control device according to any one of configurations 2 to 4, wherein the communication unit has a plurality of ports (151, 152) connected to different communication slaves.
[Structure 7]
The control device according to configuration 1, wherein the execution cycle (Tc1) in the second operation mode is set shorter than the execution cycle (Tc2) in the first operation mode.
[Structure 8]
The control device according to any one of configurations 1 to 7, which is configured so that the operation mode of the arithmetic processing unit can be referred to by an instruction included in the user program (1104) executed by the arithmetic processing unit.
[Structure 9]
It is a communication control method executed by a control device (100) including a communication unit (112) connected to a network configured to make a cycle of communication frames.
With steps (S104, S106, S110, S114; S204, S206, S210, S212, S214, S218, S220) for executing input processing according to the operation mode selected from the first operation mode and the second operation mode. ,
A step (S108, S116; S208, S216) of executing a control operation based on the input data included in the communication frame received via the communication unit, and
The step (S102, S202) for transmitting a communication frame including the output data determined by the control calculation is provided.
The step of executing the input process is
In the first operation mode,
If the transmitted communication frame is not received by the first threshold time after the communication frame is transmitted, the preliminary input data which is the input data included in the communication frame received before the transmission is controlled. Step (S114) used for calculation and
If the transmitted communication frame is received by the first threshold time, the step (S110) of updating the preliminary input data with the input data included in the received communication frame is included.
In the second operation mode,
If the transmitted communication frame is not received by the second threshold time shorter than the first threshold time after the communication frame is transmitted, the input included in the communication frame received before the transmission is received. A step (S214) in which the preliminary input data, which is data, is used for the control calculation,
If the transmitted communication frame is received by the third threshold time, which is longer than the second threshold time, the step (S220) of updating the preliminary input data with the input data included in the received communication frame. Communication control methods, including.
[Structure 10]
A control program (1102) executed by a computer (100) including a communication unit (112) connected to a network configured to make a cycle of communication frames, wherein the control program is applied to the computer.
With steps (S104, S106, S110, S114; S204, S206, S210, S212, S214, S218, S220) for executing input processing according to the operation mode selected from the first operation mode and the second operation mode. ,
A step (S108, S116; S208, S216) of executing a control operation based on the input data included in the communication frame received via the communication unit, and
The step (S102, S202) of transmitting a communication frame including the output data determined by the control calculation is executed.
The step of executing the input process is
In the first operation mode,
If the transmitted communication frame is not received by the first threshold time after the communication frame is transmitted, the preliminary input data which is the input data included in the communication frame received before the transmission is controlled. Step (S114) used for calculation and
If the transmitted communication frame is received by the first threshold time, the step (S110) of updating the preliminary input data with the input data included in the received communication frame is included.
In the second operation mode,
If the transmitted communication frame is not received by the second threshold time shorter than the first threshold time after the communication frame is transmitted, the input included in the communication frame received before the transmission is received. A step (S214) in which the preliminary input data, which is data, is used for the control calculation,
If the transmitted communication frame is received by the third threshold time, which is longer than the second threshold time, the step (S220) of updating the preliminary input data with the input data included in the received communication frame. A control program, including.

<I. Advantages>
The control system according to the present embodiment can achieve both shortening of the round trip time obtained by the ring configuration and stabilization of control when some kind of failure occurs in the ring configuration.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims, not the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Control system, 20,21,22,23,24,25,26 cable, 30 communication frames, 100 PLC, 102,202,302,402 processor, 104,204,304,404 main memory, 110,210,310 , 410 storage, 112,212 field network controller, 114 local bus controller, 116 functional unit, 118,228 internal bus, 151,152 ports, 160 control operations, 162 output processing, 164 input processing, 166 margin time, 170 current cycle Input data, 172 spare input data, 200 devices, 206,306 control circuit, 220 functional module, 251 and 351 first port, 252, 352 second port, 300 repeater, 312 field network interface, 353 third port, 400 Support device, 406 input section, 408 display section, 412 communication controller, 416 optical drive, 418 storage medium, 424 USB controller, 450 user interface screen, 452,454 graphs, 456,458 check boxes, 460 messages, 1102 system programs, 1104 User program, 1106 System setting information, 4102 OS, 4104 Development program, T0 end timing, Tc1, Tc2, Tc3 task execution cycle, Th1, Th2, Th3 threshold time, Tr1, Tr2, Tr3 round trip time, Tt1, Tt2 , Tt3, Tt4 communication time.

Claims (10)

A communication unit connected to a network configured to make a round of communication frames,
An arithmetic processing unit that repeatedly executes a control calculation based on input data included in a communication frame received via the communication unit and a communication frame including output data determined by the control calculation at each execution cycle. Equipped with
The arithmetic processing unit is
If the transmitted communication frame is not received by the first threshold time after the communication frame is transmitted, it is based on the preliminary input data which is the input data included in the communication frame received before the transmission. The first operation mode to execute the control operation and
If the transmitted communication frame is not received by the second threshold time shorter than the first threshold time after the communication frame is transmitted, the input included in the communication frame received before the transmission is received. It is configured to be able to select a second operation mode that executes control operations based on the preliminary input data that is the data.
The arithmetic processing unit is
If the transmitted communication frame is received by the first threshold time in the first operation mode, the preliminary input data is updated with the input data included in the received communication frame.
In the second operation mode, if the transmitted communication frame is received by the third threshold time longer than the second threshold time, the input data included in the received communication frame is the preliminary input data. Update the control device. The control device according to claim 1, wherein the network includes a ring configuration configured such that a communication frame is transmitted in only one direction in each of the cables connected to the communication slave. The control device according to claim 2, wherein the arithmetic processing unit can enable the second operation mode when the network includes the ring configuration. The second threshold time is determined based on the time required for the communication frame transmitted from the communication unit to make a round and return to the communication unit in the ring configuration.
The third threshold time is the time until the communication frame transmitted from the communication unit makes a round and returns to the communication unit in a state where any of the cables included in the ring configuration cannot transmit the communication frame. The control device according to claim 2 or 3, which is determined based on the above. The control device according to any one of claims 2 to 4, wherein the ring configuration includes a relay device connected to the communication unit and a plurality of communication slaves. The control device according to any one of claims 2 to 4, wherein the communication unit has a plurality of ports connected to different communication slaves. The control device according to claim 1, wherein the execution cycle in the second operation mode is set shorter than the execution cycle in the first operation mode. The control device according to any one of claims 1 to 7, wherein the operation mode of the arithmetic processing unit can be referred to by an instruction included in a user program executed by the arithmetic processing unit. It is a communication control method executed by a control device including a communication unit connected to a network configured to make a cycle of communication frames.
A step of executing input processing according to the operation mode selected from the first operation mode and the second operation mode, and
A step of executing a control operation based on the input data included in the communication frame received via the communication unit, and
A step of transmitting a communication frame including output data determined by the control operation is provided.
The step of executing the input process is
In the first operation mode,
If the transmitted communication frame is not received by the first threshold time after the communication frame is transmitted, the preliminary input data which is the input data included in the communication frame received before the transmission is controlled. The steps used for the calculation and
If the transmitted communication frame is received by the first threshold time, the step of updating the preliminary input data with the input data included in the received communication frame is included.
In the second operation mode,
If the transmitted communication frame is not received by the second threshold time shorter than the first threshold time after the communication frame is transmitted, the input included in the communication frame received before the transmission is received. A step of using the preliminary input data, which is data, for the control calculation, and
If the transmitted communication frame is received by the third threshold time, which is longer than the second threshold time, the step of updating the preliminary input data with the input data included in the received communication frame is included. Communication control method. A control program executed by a computer including a communication unit connected to a network configured to make a cycle of communication frames, wherein the control program is applied to the computer.
A step of executing input processing according to the operation mode selected from the first operation mode and the second operation mode, and
A step of executing a control operation based on the input data included in the communication frame received via the communication unit, and
The step of transmitting a communication frame including the output data determined by the control operation is executed.
The step of executing the input process is
In the first operation mode,
If the transmitted communication frame is not received by the first threshold time after the communication frame is transmitted, the preliminary input data which is the input data included in the communication frame received before the transmission is controlled. The steps used for the calculation and
If the transmitted communication frame is received by the first threshold time, the step of updating the preliminary input data with the input data included in the received communication frame is included.
In the second operation mode,
If the transmitted communication frame is not received by the second threshold time shorter than the first threshold time after the communication frame is transmitted, the input included in the communication frame received before the transmission is received. A step of using the preliminary input data, which is data, for the control calculation, and
If the transmitted communication frame is received by the third threshold time longer than the second threshold time, the step of updating the preliminary input data with the input data included in the received communication frame is included. Control program.

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