JP6524920B2 - Inter-PLC communication data complementing apparatus, inter-PLC communication data complementing method and inter-PLC communication data complementing program - Google Patents

Description

  The present invention relates to an inter-PLC communication data supplement apparatus, an inter-PLC communication data supplement method, and an inter-PLC communication data supplement program.

  In a production line of a plant, a dedicated network may be used which is updated in a fixed cycle of several ms to 10 ms (milliseconds). It may be required that the variation of the delay time of transmission / reception data of such a dedicated network be 1 ms or less. A programmable logic controller (Programmable Logic Controller, hereinafter referred to as PLC) is an input / output module that inputs measurement signals of environmental parameters such as temperature of each process and outputs drive signals for driving various actuators etc. And a controller or the like that controls an actuator or the like through an input / output module by a ladder program or the like. When facilities, functions, and processes to be controlled by PLC become a huge scale, there is a case where the whole facilities, functions, and processes are controlled by sharing roles or sharing functions among multiple PLCs. is there. At this time, the PLCs sharing the role need to closely communicate with each other, and a dedicated network may be used for the communication. In addition, external input / output signals handled by the aforementioned input / output modules etc., various quality data, etc. are also developed on this dedicated network, and can be used by multiple PLCs, making it possible for large-scale facilities, functions and processes. On the other hand, the division of roles and the division of functions by multiple PLCs are facilitated.

JP, 2013-108895, A

  When this dedicated network is replaced with a general-purpose industrial Ethernet (registered trademark), the variation of the data update cycle may be 10 to 100 ms, and the periodicity is secured for transmission and reception of data communication between PLCs. Will cause distortion in the data waveform.

  For this reason, it is necessary to delay the control execution cycle to a range in which the variation of the data update cycle does not affect the control, which causes problems such as a decrease in control accuracy.

  For a system requiring a plurality of PLCs, a synchronization method has already been proposed for the synchronization of the set time not due to the transmission time variation due to the communication path (see, for example, Patent Document 1). However, the variation of the update cycle related to data communication between PLCs is not taken into consideration, and the correction of non-periodicity of data to a fixed cycle is not considered.

  The present invention has been made to solve the problems as described above, and even when the communication network is replaced with a general purpose network from a dedicated network, periodical data communication between PLCs having a variation in the update cycle. It is an object of the present invention to provide an inter-PLC communication data interpolation device, an inter-PLC communication data interpolation method, and an inter-PLC communication data interpolation program, which can be supplemented to the above data.

An embodiment of the present invention is an inter-PLC communication data complementing apparatus for a second PLC connected to a first PLC via a communication network and operating in the same control sampling cycle as the first PLC, in order to achieve the above object.
A storage unit that receives and stores data associated with a counter value and a data value, which are transmitted from the first PLC for each control sampling cycle, and are updated for each cycle;
A comparator that determines that there is a delay when the counter value of the current cycle data stored in the storage unit is the same as the counter value of the data one cycle before in each control sampling cycle;
The data to be received in the current cycle based on the rate of change between the data value of the data two cycles earlier stored in the storage unit and the data value of the data one cycle before when it is determined that there is the delay And a complementing unit that estimates and complements data values of

  Preferably, in each of the cycles after it is determined that there is the delay, the comparison unit determines that the difference between the counter value of the data of the current cycle stored in the storage unit and the counter value of the data one cycle before is 2 It is characterized by determining that there is a delay until it becomes.

  Preferably, the complementing unit is configured to change the rate of change of the data value between one cycle before and two cycles before and the rate of change of the data value between two cycles before and three cycles before. Estimating and complementing data values of data of the current cycle.

  According to the embodiment of the present invention, since distortion of the data waveform due to the variation of the update cycle can be compensated on the data receiving side, even if communication of data between PLCs is performed via the communication network with the variation of the update cycle, It can be referred to as the same data as when performing data communication via a fixed period dedicated network. In this way, the division of roles and the division of functions by a plurality of PLCs can be realized without considering the increase in load on the PLC and the decrease in control accuracy.

FIG. 1 is a block diagram illustrating a system configuration according to a first embodiment. FIG. 7 is a timing chart schematically illustrating an operation waveform in each part of the system in accordance with Embodiment 1. FIG. 6 is a diagram showing the relationship between each cycle and data values in the system according to Embodiment 1. 5 is a flowchart of a complementing process routine executed by the data complementing apparatus 2; FIG. 16 is a diagram showing the relationship between each cycle and data values in the system according to Embodiment 2. FIG. 16 is a block diagram illustrating a system configuration according to a third embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of sizes between parts, and the like are not necessarily the same as the actual ones. In addition, even in the case of representing the same portion, the dimensions and ratios may be different from one another depending on the drawings.
In the specification of the present application and the drawings, the same elements as those described above with reference to the drawings are denoted by the same reference numerals, and the detailed description will be appropriately omitted.

Embodiment 1
[Basic system configuration]
FIG. 1 is a block diagram illustrating a system configuration according to the first embodiment. The system shown in FIG. 1 includes a PLC 1, a communication network 20, and a PLC 30. The PLC 1 is connected to the PLC 30 via the communication network 20, and receives data transmitted by the PLC 30. PLC1 and PLC30 operate with the same control sampling cycle.

  PLC 1 is a programmable logic controller. The PLC 1 has a data complementing device 2 that compensates for distortion of a data waveform described later. The PLC 1 includes, for example, a controller that controls the system by a sequence program stored in a memory, an input / output module driven by the controller, and the like. The controller, the memory, the input / output module and the like may be connected on the communication network 20, or may be connected on the other dedicated network and connected to the communication network 20 via the controller and the like. The PLC 1 may include the data complementing device 2 in a controller, for example.

  The data complementing device 2 may operate, for example, in accordance with a program sequentially executed inside the PLC 1.

  The PLC 30 is a programmable logic controller. The PLC 30 has a data output unit 31 and a counter unit 32. The PLC 30 includes, for example, a controller that controls the system by a sequence program stored in a memory, an input / output module driven by the controller, and the like. The controller, the memory, the input / output module and the like may be connected on the communication network 20, or may be connected on the other dedicated network and connected to the communication network 20 via the controller and the like. The PLC 30 may include, for example, the data output unit 31 and the counter unit 32 in the controller.

  The data output unit 31 outputs the data value 33. The data value 33 is, for example, a transmission / reception signal between each input / output module or the like, and is a signal used for data communication between PLCs of the PLC 1 and the PLC 30. The data value 33 is output, for example, at a fixed cycle time of 10 ms. The counter unit 32 generates a counter value 34 that counts up in a fixed cycle time of 10 ms, for example. The PLC 30 outputs, on the communication network 20, data in which the counter value 34 and the data value 33 in the same cycle are associated with each other. Needless to say, the output of the counter unit 32 is not limited to the count-up operation, but may be a count-down operation.

  The communication network 20 is, for example, Industrial Ethernet (registered trademark). In the industrial Ethernet (registered trademark), the variation of the data update cycle may be 10 to 100 ms, and the periodicity is not secured for transmission and reception of data communication between PLCs, and thus distortion of the data waveform occurs. A dedicated communication network with less variation in delay time may be used as the communication network 20, and the application of the present invention is not hindered.

Next, distortion of the waveform of data due to the communication network 20 in which the periodicity is not ensured will be described with reference to FIG.
FIG. 2 is a timing chart schematically illustrating an operation waveform in each part of the system according to the first embodiment.

  The operation waveforms of the data value 33a output from the data output unit 31 of the PLC 30 and the operation waveform of the counter value 34a output from the counter unit 32 are conceptually shown along with the PLC 30 sampling time axis in the operation waveforms on the top of FIG. There is. In the operation waveforms in the middle of FIG. 2, the operation waveforms of the data value 33b and the counter value 34b output from the PLC 30 on the communication network 20 are conceptually shown along with the PLC1 sampling time axis. In the lowermost operating waveform of FIG. 2, the data value 33c and the counter value 34c input to the PLC 1 and the data value 33d complemented by the data complementing device 2 are conceptually shown along with the PLC 1 sampling time axis. .

  As shown in the operation waveform in the middle of FIG. 2, the data value 33 a of the PLC 30 does not maintain periodicity when the communication network 20 is developed on a general-purpose industrial Ethernet (registered trademark). In the general-purpose industrial Ethernet (registered trademark), the simultaneousness of transmission and reception is not guaranteed, and the propagation delay time of the signal developed on the network by communication traffic etc. may vary widely, for example, to about 10 ms to about 100 ms. It is. Therefore, the timing of signal reception may be dominated by the variation of the propagation delay time. For example, as in the data value 33b, the delay is partially increased and distortion occurs in the waveform.

  As shown in the lowermost stage operation waveform of FIG. 2, when the data value 33b whose periodicity is not maintained is read in the control sampling period of PLC1, it becomes a delay accompanied by a data update omission like the data value 33c. The distortion is larger than the original data value 33b.

[Characteristic Configuration in Embodiment 1]
The data complementing apparatus 2 of the present embodiment for complementing such distortion of the data waveform will be described with reference to FIGS. 1 to 4.

  In the present embodiment, since the PLC 1 and the PLC 30 operate in the same control sampling cycle, the counter value 34 c read by the PLC 1 is one for each cycle if there is no variation in the data update cycle caused by the communication network 20. It is expected to count up. On the other hand, when the counter value 34c does not count up, it can be determined that a delay accompanied by a data update omission due to the communication network 20 has occurred, and data to be received in the current cycle can not be received. Even in such a case, the PLC 1 is required to be able to control the control target by complementing the data to be received in the current cycle.

  Therefore, in the data complementing device 2 of the present embodiment, it is determined that there is a delay when the counter value of the current cycle data received in the current cycle and the counter value of the data received one cycle before are the same. When it is determined that there is a delay, data of data to be received in the current cycle based on a change rate between the data value of data received two cycles earlier and the data value of data received one cycle earlier The values were estimated and complemented (data value 33d).

  The data complementing device 2 of the present embodiment for realizing such processing will be specifically described. The data complementing device 2 shown in FIG. 1 includes a complementing unit 3, a storage unit 4, and a comparing unit 5. The data complementing device 2 receives the data transmitted by the PLC 30 from the communication network 20. The received data includes the data value 33 for communication between PLCs of the PLC 30 and the counter value 34. The counter value 34 counts up one by one in the control sampling cycle of the PLC 30, so if there is no variation in the data update cycle caused by the communication network 20, the counter value of the data received by the PLC 1 is also one in each control sampling cycle. Count up.

  The storage unit 4 stores the latest reception data (current cycle data) in which the counter value 34 and the data value 33 are associated with each other in each control sampling cycle. The storage unit 4 also stores past received data (data one cycle before, data two cycles before,...) For several cycles.

  The comparison unit 5 compares the counter value 34 of the current period data read from the storage unit 4 with the counter value 34 of data one cycle before for each control sampling period. If the difference between the counter values is 1, it is determined that there is no delay. On the other hand, when the difference between the counter values is 0, it is determined that there is a delay. Further, the comparing unit 5 determines that there is delay until the difference between the counter value of the current period data and the counter value of the data one cycle before becomes 2 in each cycle after it is determined that there is a delay. On the other hand, when the difference between the counter values is 2, it is determined that there is no delay because the delay state is canceled.

  The complementing unit 3 executes a complementing process of estimating and complementing the data value of the data to be received in the current cycle according to the result of the delay determination by the comparing unit 5. Thereby, the data value in which the distortion of the data waveform caused by the communication network 20 is complemented is output from the data complementing device 2 and can be used inside the PLC 1.

The process of the complementing unit 3 according to the result of the delay determination of the comparing unit 5 will be described.
If the comparison unit 5 determines that there is no delay, the complementation unit 3 reads the data value 33c stored in the storage unit 4 as it is, assuming that there is no influence of the variation of the data update cycle caused by the communication network 20. , And the output of the data complementing device 2.

  On the other hand, when the comparison unit 5 determines that there is a delay, the complementation unit 3 is received in the current cycle based on the rate of change between the data value of the data two cycles before and the data value of the data one cycle before. Estimate and complement data values of power data.

The estimation of the data value of the current cycle will be described with reference to FIG. FIG. 3 is a diagram showing the relationship between each cycle and the data value. In FIG. 3, X _{N + 1} is the time of the current cycle, X _N is the time of one cycle earlier, X _N-1 is the time of two cycles earlier, Y _{N + 1} is the data value of the current cycle, and Y _N is the data value of one cycle earlier , Y _N-1 indicate data values two cycles before. X _N , X _N-1 , Y _N and Y _N-1 are known in the current cycle. Since the control sampling period is constant,
X _{N + 1} −X _N = X _N −X _N−1 = Δt (const)
Therefore, X _{N + 1} is expressed by the following equation.
X _{N + 1} = X _N + Δt

The rate of change a is expressed by the following equation from X _N , X _{N -1} , Y _N , Y _{N -1} .
_{a = (Y N -Y N-} 1) / (X N -X N-1) = (Y N -Y N-1) / Δt

The data value Y _{N + 1} of the current period to be estimated is expressed as a differential expression Y _{N + 1} −Y _N = a × (X _{N + 1} −X _N ) = a · Δt
Since it is represented by, transform this,
Y _{N + 1} = (Y _N -Y _N-1 ) / Δt × Δt + Y _N = Y _N × 2-Y _N-1
That is,
(Data value of the current cycle) = (data value of one cycle before) × 2
− (Data value two cycles before) ... (1)
It is expressed as

  Therefore, when it is determined that there is a delay, the complementing unit 3 predicts and calculates the data value of the current cycle using the complementing process represented by the equation (1), and calculates the data value of the current cycle that has been predicted and calculated. The output of the complementing device 2 The complementing process continues until the difference between the counters reaches two. The data value 33c of FIG. 2 stored in the storage unit 4 is complemented as the data value 33d of FIG. 2 by the complementing process.

(flowchart)
FIG. 4 is a flowchart of a complementing process routine executed by the data complementing apparatus 2 in order to realize the above-described operation. This routine is repeatedly executed each time it ends. Note that the data complementing device 2 sequentially stores data received from the communication network 20 in the storage unit 4 by another routine.

  In the routine shown in FIG. 4, first, the comparison unit 5 calculates the difference between the counter value of the current cycle data stored in the storage unit 4 and the counter value of the data one cycle before (step S100).

  Next, the comparison unit 5 determines whether the difference between the counter values is 0 or not (step S110). If it is determined that the difference between the counter values is 1, the latest data to be received in the current cycle can be received, and the complementing process is unnecessary. Therefore, the process proceeds to step S160. In step S160, the complementing unit 3 reads the data value of the current cycle data from the storage unit 4 as it is, and uses it as the output of the data complementing device 2.

  On the other hand, when the difference between the counter values is determined to be 0 in step S110, the complementing unit 3 executes a complementing process of estimating and complementing the data value of the data to be received in the current cycle (step S120). Specifically, the data value of the current cycle is predicted and calculated using the above-mentioned equation (1), and the data value of the current cycle subjected to the prediction calculation is used as the output of the data complementing device 2.

  Thereafter, the process proceeds to the next control sampling cycle (step S130), and the comparison unit 5 calculates the difference between the counter value of the current cycle data stored in the storage unit 4 and the counter value of the data one cycle before (step S140). .

  Next, the comparison unit 5 determines whether the difference between the counter values is 2 or not (step S150). The process returns to step S120 and continues the complementing process until it is determined that the difference between the counter values is two. On the other hand, when the difference between the counter values is determined to be 2, the delay state is eliminated, and the latest data to be received in the current cycle can be received, and the complementing process is unnecessary. Therefore, the process proceeds to step S160. In step S160, the complementing unit 3 reads the data value of the current cycle data from the storage unit 4 as it is, and uses it as the output of the data complementing device 2. Thereafter, the routine is ended, and the routine is started again at the next control sampling period.

  As described above, according to the routine shown in FIG. 4, even when a delay accompanied by a data update omission occurs using the communication network 20 in which the periodicity is not ensured for data communication between PLCs, Data values of data to be received in the current cycle can be estimated and supplemented. Therefore, PLC1 can give a control signal to a control object using a complemented data value.

Second Embodiment
A second embodiment of the present invention will now be described with reference to FIG. The system of the present embodiment can be realized by causing the complementing unit 3 to perform prediction calculation described later in the configuration shown in FIG.

  In the first embodiment described above, attention is paid to the rate of change (slope) between the data value of the data two cycles earlier and the data value of the data one cycle ago, and reception is performed in the current cycle using the above equation (1). The data value of the data to be calculated is predicted. However, as shown in FIG. 5, when the change in the change rate (slope) is steep, the accuracy of the prediction calculation is degraded. Therefore, in the present embodiment, the current value is calculated based on the rate of change of the data value between one cycle before and two cycles before and the change rate of the data value between two cycles before and three cycles before. Predictive operation is performed on data values of periodic data.

The estimation of the data value of the current cycle will be described with reference to FIG. FIG. 5 is a diagram showing the relationship between each period and the data value. In FIG. 5, X _{N + 1} is the time of the current cycle, X _N is the time of one cycle earlier, X _N-1 is the time of 2 cycles earlier, X _N-2 is the time of 3 cycles earlier, Y _{N + 1} is the data of the current cycle value, _{Y N} data values one cycle _{before, Y N-1} are two periods before the data _{values, Y N-2} represents the data value of the previous three cycles. _{X N, X N-1,} X N-2, Y N, Y N-1, Y N-2 in the current cycle is known. Since the control sampling period is constant,
X _{N + 1} -X _N = X _N -X _N-1 = X _N-1 -X _N-2 = Δt (const)
Therefore, X _{N + 1} is expressed by the following equation.
X _{N + 1} = X _N + Δt

The rate of change a _N is represented by the following equation from X _N , X _{N -1} , Y _N , Y _{N -1} .
_{a N = (Y N -Y N} -1) / (X N -X N-1) = (Y N -Y N-1) / Δt
The rate of change a _N-1 is represented by the following equation using X _N-1 , X _N-2 , Y _N-1 , and Y _N-2 .
_aN-1 = (YN _-1- YN _-2 ) / (XN _-1- XN _-2 ) = (YN _-1- YN _-2 ) /? t
The change rate a _{N + 1} is expressed by the following equation.
a _{N + 1} = a × Δt + a _N
Here, a = (a _N -a _{N -1} ) / Δt
_{Therefore, a N + 1 = 2a N} -a N-1 = (2Y N -3Y N-1 + Y N-2) / Δt

The data value Y _{N + 1} of the current cycle to be estimated is
Y _{N + 1} = a _{N + 1} · Δt + Y _N = 3 Y _N -3 Y _{N -1} + Y _N -2
That is,
(Data value of the current cycle) = (data value of one cycle before) × 3
− (Data value 2 cycles before) × 3
+ (Data value three cycles earlier) ... (2)
It is expressed as

  Therefore, when it is determined that there is a delay, the complementing unit 3 predicts and calculates the data value of the current cycle using the complementation processing represented by the equation (2), and calculates the data value of the current cycle that has been predicted and calculated. The output of the complementing device 2 The complementing process continues until the difference between the counters reaches two. The data value 33c of FIG. 2 stored in the storage unit 4 is complemented as the data value 33d of FIG. 2 by the complementing process.

  As described above, according to the second embodiment of the present invention, when equation (2) is used for the prediction calculation in the complement unit 3, the change rate (slope) changes sharply as shown in FIG. Also, as in the first embodiment, data values of data to be received in the current cycle can be estimated and complemented. Therefore, PLC1 can give a control signal to a control object using a complemented data value.

Third Embodiment
A third embodiment of the present invention will now be described with reference to FIG. The configuration shown in FIG. 6 is the same as the configuration of FIG. 1 except for the counter unit 6 and the comparison unit 5a.

  Although in the above-described first embodiment, the PLC 1 and the PLC 30 operate on the same control sampling cycle, the operation cycle of the PLC 1 itself may be different from the control sampling cycle of the PLC 30. Therefore, in the present embodiment, the independent counter unit 6 is mounted inside the PLC 1 and the temporal relationship with the counter unit 32 of the PLC 30 is defined to match the operation cycle of the PLC 1 to the control sampling cycle of the PLC 30. . At this time, the comparison unit 5a determines the result of the delay determination in the complement unit 3 at a timing taking into consideration the temporal relationship between the counter value from the counter unit 6 and the counter value of the counter unit 32 of the PLC 30 read from the storage unit 4. Output The contents of the delay determination in the comparing unit 5a are the same as those in the comparing unit 5 of FIG. Further, the other processes are the same as in the first embodiment, and therefore the description thereof is omitted.

  As described above, according to the third embodiment of the present invention, even when the operation cycle of PLC 1 itself is different from the control sampling cycle of PLC 30, the complementary processing described in the first and second embodiments is applied. The same effect can be obtained.

1 PLC
Reference Signs List 2 data complementing device 3 complementing unit 4 storage unit 5, 5 a comparing unit 6 counter unit 20 communication network 30 PLC
31 data output unit 32 counter unit 33 data value 34 counter value

Claims (5)

An inter-PLC communication data supplementing apparatus for a second PLC connected to the first PLC via a communication network that does not ensure periodicity with respect to transmission and reception, and operating in the same control sampling cycle as the first PLC,
A storage unit configured to receive and store data in which the counter value updated every cycle and the data value related to the control signal to be controlled , which are transmitted from the first PLC for each control sampling cycle, are associated;
A comparator that determines that there is a delay when the counter value of the current cycle data stored in the storage unit is the same as the counter value of the data one cycle before in each control sampling cycle;
The data to be received in the current cycle based on the rate of change between the data value of the data two cycles earlier stored in the storage unit and the data value of the data one cycle before when it is determined that there is the delay A complementing unit that estimates and complements data values of
An inter-PLC communication data complementing device comprising: The comparison unit is configured such that the difference between the counter value of the data of the current period stored in the storage unit and the counter value of the data one cycle before becomes 2 in each cycle after the delay is determined to be present. To determine that there is a delay,
The inter-PLC communication data complementing device according to claim 1, characterized in that The complementing unit is configured to calculate the change rate of the data value between one cycle before and two cycles before and the change rate of the data value between two cycles before and three cycles before. Estimating and complementing the data values of the data,
The inter-PLC communication data complementing device according to claim 1 or 2, characterized in that A method for supplementing communication data between PLCs of a second PLC which is connected to the first PLC via a communication network where constant periodicity is not secured for transmission and reception and which operates in the same control sampling cycle as the first PLC,
Receiving and storing data associating the counter value updated from each cycle with the data value related to the control signal to the control target, which data is transmitted from the first PLC every control sampling cycle;
Determining that there is a delay when the counter value of the stored data of the current cycle is the same as the counter value of the data one cycle before in each control sampling cycle;
If it is determined that there is the delay, the data value of the data to be received in the current cycle is estimated and complemented based on the rate of change between the data value of the data two cycles earlier and the data value of the data one cycle earlier. Step to
An inter-PLC communication data supplement method comprising: An inter-PLC communication data supplement program for a second PLC connected to the first PLC via a communication network that does not ensure periodicity with respect to transmission and reception, and operating in the same control sampling cycle as the first PLC,
Second PLC,
Storage means for receiving and storing data associating the counter value updated every cycle and the data value related to the control signal to the control target transmitted from the first PLC for every control sampling cycle;
Comparing means for determining that there is a delay when the counter value of the current cycle data stored in the storage means is the same as the counter value of data one cycle before in each control sampling cycle;
The data to be received in the current cycle based on the rate of change between the data value of the data two cycles earlier and the data value of the data one cycle earlier stored in the storage means when it is determined that there is the delay Complementary means for estimating and complementing the data values of
Inter-PLC communication data supplement program to make it function.

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