JP2000215188A - Network controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out the arithmetic processing of a controller synchronously with the processing operation on a network. SOLUTION: A communication module 19 carries out the input processing, the output processing and the transmission of data for an input device 11 and an output device 12 respectively at each network time which is managed by a network time management part 26. An MPU 15 carries out an operation at an MPU time that is managed by a controller time management part 24. Both parts 26 and 24 operate independently of each other, and a network time converting/monitoring part 25 decides the network time from the MPU time and in consideration of the processing time of the module 19. Then the network time is applied to the reference time of the part 26 so that the processing operation on a network and the arithmetic processing can be carried out at the times which are synchronous with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network control device, and more particularly, to an input device and an output device whose input processing, output processing and data communication are time-controlled so as to operate based on the same time, and collected from the input device. The present invention relates to a network control device in which the operation of the arithmetic processing is synchronized with the operation of the network in a network system in which a higher-level control device that executes the arithmetic processing of the obtained data at regular intervals is distributed on a network.

[0002]

2. Description of the Related Art In a factory automation system and the like, it is common practice to organically connect various types of processing apparatuses, transfer apparatuses, and the like via a network, and to comprehensively manage them by a controller. Here, the configuration of a conventional network system will be described below with an example of an instrumentation / control system.

FIG. 4 is a diagram showing a configuration example of an instrumentation / control system. The instrumentation and control system consists of an input device (AI) 1
1, an output device (AO) 12, a controller 13,
And a network 14 for connecting them. Although a plurality of input devices 11 and output devices 12 are arranged on the network 14, one is representatively shown in the figure. The input device 11 converts an analog measurement value from a sensor, for example, to an input of another device on the network 14 and transmits the converted value. The controller 13 calculates the transmitted input data and sends the calculation result to the network 14 as output data. The output device 12 converts the output data transmitted on the network 14 into, for example, a control signal for a solenoid valve.

[0004] The controller 13 includes a microprocessing unit (hereinafter, referred to as an MPU) 1 for performing arithmetic processing.
5 and a communication board 16 for communicating with the network 14
It is composed of A first shared memory 17 for exchanging input data and output data is arranged between the MPU 15 and the communication board 16. The communication board 16 mainly includes a base board 18 for interfacing with the MPU 15 and a communication module 19 for controlling a communication protocol of the network 14. In the communication board 16, a second shared memory 20 for exchanging input data and exchanging output data between the base board 18 and the communication module 19 also.
Is arranged. The base board 18 includes an internal buffer 21 through which input / output processing is performed.

[0005] The communication module 19 collects input data from the input device 11 on the network 14 by executing communication in accordance with the schedule of the network held by the communication module 19 and stores it in the second shared memory 20. . When the time to output the output data comes, the communication module 19 reads out the output data from the second shared memory 20 and sends it to the network 14.

When the base board 18 receives an input processing request from the MPU 15, the base board 18 outputs the input data held in the internal buffer 21 to the first shared memory 17,
First shared memory 17 based on an output command from PU 15
Is taken into the internal buffer 21. All input / output processing of the base board 18 is M
This is performed according to a command from PU15.

The controller 13 having the above configuration is
Functionally, it can be divided into an MPU 15 that performs its own arithmetic processing, and a communication module 19 that executes a schedule of the network 14, and the operations thereof will be described below.

FIG. 5 is a timing chart showing the operation schedule of the MPU. The MPU 15 repeats a series of processes of issuing an input command, executing an arithmetic process, and issuing an output command in a one-second cycle in the illustrated example. Assuming that the time of 0 millisecond is the start of the operation of the MPU 15, the operation processing phase from the start of the operation to the first input command is set to 200 milliseconds in the illustrated example.

[0009] The schedule of the MPU 15 is executed based on the time management of the controller 13 by the base board 18. In each cycle, first, at the time of the arithmetic processing phase of the MPU 15, the MPU 15 issues an input command.
Then, since the base board 18 transfers the input data from the internal buffer 21 to the first shared memory 17 by the input / output processing, the MPU 15 executes the arithmetic processing using the transferred input data, and the arithmetic processing is performed. The output data is output to the first shared memory 17. Then, MPU1
5 issues an output command, the base board 18 transfers the output data in the first shared memory 17 to the internal buffer 21 by the input / output processing. A series of processes of the input command, the arithmetic process, and the output command is executed at a constant period of one second.

FIG. 6 is a timing chart showing an operation schedule of the network. In the network 14, the input processing of the input device 11, the transmission of the input data obtained by the input process, the transmission of the output data to the output device 12, and the output process of the output device 12 are performed by the communication module 1
9 is performed according to the schedule held. The input device 11 and the output device 12 are
The operation is started on the basis of the reference time on the network which is broadcasted at regular intervals from.

Here, when the time of time 0 is defined as the start of the reference time of the network, a series of processing of input processing, transmission of input data, transmission of output data, and output processing is repeatedly executed at a predetermined cycle from that time. Is done. According to the schedule of this network, first, input processing of the input device 11, for example, processing of taking in input data from a sensor is performed, and then the input data is transmitted to the communication module 19 and stored in the second shared memory 20. . Next, the base board 18 performs input / output processing. In this input / output processing, first, the base board 18 fetches the input data of the second shared memory 20 into the internal buffer 21, and thereafter,
This includes the processing until the output data obtained by the arithmetic processing of the PU 15 is transferred to the second shared memory 20 via the internal buffer 21. After that, the output data is transmitted to the output device 12, and the output process is performed by the output device 12.

As described above, the communication module 19 operates the input device 11, the output device 12, and the output device 12 on the network 14 in synchronization with the input processing, the data communication, and the output processing in order based on the reference time of the network. According to this schedule, the input data transmitted from the input device 11 is stored in the second shared memory 20, and the output device 12 is operated with the output data stored in the second shared memory 20. ing. On the other hand, MPU
Reference numeral 15 denotes a schedule for executing an input command, an arithmetic processing, and an output command at an original fixed period, which is managed independently of the reference time. Arithmetic processing is executed based on the input data contained therein, and output data of the operation result is stored in the internal buffer 21.

[0013]

However, the arithmetic processing of the controller and the processing operation on the network are:
Since the operations are performed asynchronously under independent time management, a series of control operations, that is, a control loop including input processing, input data transmission, operation, output data transmission, and output processing can be operated in order. It was difficult. In other words, the input device always has the latest input data, and that input data is transmitted and used for arithmetic processing. However, in the actual arithmetic processing, the input data immediately after transmission is not necessarily used. Not necessarily used. this is,
For independent time management, even if the operation cycle of the controller and the operation cycle of the network are the same, the input data captured at the start time of the operation is different due to the different start times and the difference in time accuracy. This is because the data may have been transmitted one cycle before. Therefore, if the input data used for the calculation is not the latest data, there is a problem that the control accuracy cannot be maintained.

SUMMARY OF THE INVENTION The present invention has been made in view of such a point, and it is an object of the present invention to provide a network control device capable of synchronizing arithmetic processing of a controller and processing operation on a network.

[0015]

According to the present invention, in order to solve the above-mentioned problem, a communication means for communicating with a device on a network and a calculation means for performing a calculation for controlling the device have independent time management. A first time management means for managing the time of said arithmetic means, and a network time serving as a reference for operation in a network based on the time managed by said first time management means. Network time conversion means for determining the network time, and second time management means for managing the network time based on the time determined by the network time conversion means. Is done.

According to such a network control device, in a control device in which calculations and network operation schedules are executed under mutually independent time management, the time managed by the first time management means is controlled. The network time conversion means determines the network time based on the network time, and applies the network time to the second time management means. Thereby, the operation on the network and the arithmetic processing by the arithmetic means can be executed at a synchronized time.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, taking an example in which the present invention is applied to an instrumentation / control system.

FIG. 1 is a block diagram showing an instrumentation / control system provided with a network control device according to the present invention.
Note that the same or equivalent components as those of the conventional system shown in FIG. 4 are denoted by the same reference numerals. instrumentation·
The control system includes an input device (AI) 11, an output device (AO) 12, a controller 13, and a network 14 connecting these. Input device 1
1 converts, for example, an analog measurement value from a sensor for input to another device on the network 14 and transmits the converted value to the controller 13 as input data. Controller 1
3 calculates the transmitted input data and sends the calculation result to the network 14 as output data. The output device 12 converts the output data transmitted on the network 14 into, for example, a control signal for a solenoid valve.

The controller 13 includes a microprocessing unit (MP) for performing arithmetic processing in the arithmetic processing unit 22.
U) 15 and a communication board 16 for communicating with the network 14. MPU15 and communication board 1
6, a first shared memory 17 having a dual configuration for exchanging input data and output data is arranged. The communication board 16 mainly includes a base board 18 for interfacing with the MPU 15 and a communication module 19 for controlling a communication protocol of the network 14. Between the base board 18 of the communication board 16 and the communication module 19, a dual shared second memory 20 for exchanging input data and exchanging output data is arranged. The base board 18 includes an input / output processing unit 23 for performing input / output processing, an internal buffer 21, a controller time management unit 24 for managing the time of the controller 13, and a network time conversion / monitoring unit 25. Communication module 19
Has a network time management unit 26 that manages the reference time of the network 14.

The communication module 19, based on the network time managed by the network time management unit 26,
According to your own network schedule,
The input data is collected from the input device 11 on the network 14 and stored in the second shared memory 20, or the output data of the operation result is read out from the second shared memory 20 and transmitted to the network 14.

The base board 18 operates based on the controller time managed by the controller time management unit 24. When an input processing request is received from the MPU 15, the base board 18 transmits the input data held in the internal buffer 21 to the first. And outputs the output data stored in the first shared memory 17 to the internal buffer 21 based on an output command from the MPU 15. Input / output processing of the base board 18 is performed according to instructions from the communication module 19 and the MPU 15.

The network time management unit 26 of the communication module 19 manages a reference time on the network 14, and broadcasts the generated reference time to the input device 11 and the output device 12 via the network 14 at a fixed period. Notify by doing. Here, the feature of this configuration is that the time of the controller 13 is referred to when generating the reference time. That is, the controller time in the controller time management unit 24 is determined by the network time conversion / monitoring unit 25 in consideration of the time until input data collected from the input device 11 is stored in the second shared memory 20 and the like. The time is converted to the network time, and the converted time is
Is applied as a reference time.

Thus, the controller time and the reference time are synchronized, and the network 1 that operates based on the reference time
M based on the operation on controller 4 and the controller time
The arithmetic processing of the PU 15 is executed according to a control loop in which continuity and constant periodicity are maintained. That is, a control loop including input processing by the input device 11, transmission of input data, calculation by the MPU 15, transmission of output data, and output processing by the output device 12 can be operated in order. Next, this operation will be described using a timing chart.

FIG. 2 is a timing chart showing the operation schedule of the time-synchronized MPU and the operation schedule of the network. In the example shown, MP
In U15, the calculation of phase 0 is started at MPU time 0, the MPU calculation processing phase Tp for issuing an input command is 200 milliseconds, and the cycle is 1 second. On the other hand, regarding the input / output processing according to the network schedule, “cycle ×
n + input / output processing execution offset To ”(n is an arbitrary integer).

First, the input device 11 performs input processing according to a network schedule in the communication module 19, and transmits the input data to the communication module 19. Thereafter, the communication module 19 stores the transmitted input data in the second shared memory 20, and instructs the base board 18 to execute an input / output process at time ta. The base board 18 receives the input / output processing execution instruction and transfers the input data from the second shared memory 20 to the internal buffer 21. The transfer time is Ts.

Next, when the base board 18 receives an input command from the MPU 15 at time tb, the internal buffer 2
1 is transferred to the first shared memory 17. The data transfer time at that time is Ts. MPU1
5 performs an arithmetic operation on the input data fetched into the first shared memory 17 and stores the operation result in the first shared memory 17 as output data. When an output command is issued from the MPU 15, the base board 18 outputs the output data stored in the first shared memory 17 to the second shared memory 17 via the internal buffer 21.
In the shared memory 20. Thereafter, when the transmission timing of the output data comes according to the schedule of the communication module 19, the output data in the second shared memory 20 is transmitted to the output device 12, and the output device 12 performs an output process using the output data. .

As a result, the data to be processed by the MPU 15 is always the latest input data transmitted from the input device 11 and the control accuracy of the controller 13 can be maintained.

Next, the network time conversion / monitoring unit 25 that applies the controller time to the network time will be described. The network time conversion / monitoring unit 25 determines the network time according to the following equation.

[0029]

## EQU00001 ## Network time = MPU time + (To + Ts + Tj-Tp) (1) Here, the MPU time is the time of phase 0 when the MPU 15 starts processing, and the time periodically notified from the MPU 15, To Is the input / output processing execution offset from the network time at which the input / output processing unit 23 starts processing, and Ts is the time for transferring input data from the second shared memory 20 to the internal buffer 21 when receiving the input / output processing execution command. , Tj
Denotes an allowable jitter indicating an allowable range of a start deviation in which an input command received from the MPU 15 is allowed, and Tp denotes an MPU calculation processing phase.

That is, the network time is determined with reference to the MPU time, the input / output processing offset To, the input data transfer time Ts, the allowable jitter Tj, and the MPU operation processing phase Tp.

The network time determined in this manner is notified from the network time conversion / monitoring unit 25 to the network time management unit 26 of the communication module 19. The network time management unit 26 uses the notified network time as a reference time, and the communication module 19 performs broadcast notification to devices on the network 14. Since the communication module 19 executes the schedule of the network based on the reference time, input processing at the input device 11, transmission of input data, input processing at the input / output processing unit 23, arithmetic processing by the MPU 15, input / output processing The output processing in the section 23, the transmission of output data, and the output processing by the output device 12 operate synchronously in this order.

Next, the network time conversion / monitoring unit 25
To the network time management unit 26 of the communication module 19
After the notification, the network time notified by the controller time management unit 24 and the network time management unit 26
May change due to the difference in accuracy between the two.
In anticipation of such a case, the allowable jitter Tj is included in the calculation item in the calculation formula of the network time. However, if the network time is shifted so much that it cannot be absorbed by the allowable jitter Tj, the network operation is performed. And M
Synchronization with the PU operation cannot be achieved. Therefore,
The network time conversion / monitoring unit 25 monitors the network time, corrects if necessary, and notifies the network time management unit 26.

FIG. 3 is a flowchart showing the flow of the network time correction process. The network time conversion / monitoring unit 25 firstly outputs a time ta of the input / output processing execution command notified from the communication module 19 to the input / output processing unit 23 of the baseboard 18, a time tb of the input command notified from the MPU 15, The transfer time Ts of the input data transferred from the second shared memory 20 to the internal buffer 21 and the current network time are obtained (step S1).
Calculate the time difference (tb−ta−Ts) (Step S
2). Next, it is determined whether the calculated time difference is larger than twice the allowable jitter Tj (step S3). If the time difference is within twice the allowable jitter Tj,
It is determined that the MPU time and the network time are synchronized, and this processing ends without correction.

If the time difference is greater than twice the allowable jitter Tj, the time tb of the input command is set within the allowable range ±
It is determined that it is outside the range of Tj. Here, it is determined whether the time difference has a negative value (step S4). If the time difference has a negative value, it is determined that the timing for issuing the input command is too early. In this case, since the input command is issued before the input data is completely transferred from the second shared memory 20 to the internal buffer 21, the time is advanced by (time difference + allowable jitter Tj) from the current network time. The value is set as the network time, and is notified to the network time management unit 26 of the communication module 19 (step S5). If the time difference has a positive value,
It is determined that the timing of issuing the input command is too late. In this case, there is no problem as long as the arithmetic processing unit 22 performs the arithmetic processing on the input data, but this time, the timing at which the communication module transmits the output data to the output device 12 becomes too early, and the output data one cycle earlier is output. Therefore, a value delayed from the current network time by (time difference-allowable jitter Tj) is set as the network time, and is notified to the network time management unit 26 of the communication module 19 (step S6).

Thus, in the controller time management unit 24 and the network time management unit 26 operating independently of each other, the network time management unit 26 absorbs the time notification from the controller time management unit 24 that is the reference time management source. Even if a time lag that cannot be obtained occurs, the lag can be corrected.

When the input command is near the boundary of the permissible range ± Tj, correction may frequently occur.
In this case, since the operation of the network becomes unstable, the network time conversion / monitoring unit 25 determines whether or not the time difference is within the allowable range of ± Tj according to the change direction of the time difference. Change the threshold,
It is preferable to have a so-called hysteresis function.

[0037]

As described above, in the present invention, the network time is determined based on the time of the controller. Thereby, it is possible to synchronize with the operation of the controller and the network that are operating on independent schedules from each other, and it is possible to realize a control loop in which periodicity is maintained.

Further, the present invention is configured to monitor a synchronization deviation between the network time and the controller time, and to correct the network time when the deviation becomes large.
As a result, it is possible to eliminate a deviation that cannot be absorbed by the time notification from the reference time management source.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an instrumentation / control system including a network control device according to the present invention.

FIG. 2 is a timing chart showing a calculation schedule of a time-synchronized MPU and an operation schedule of a network.

FIG. 3 is a flowchart illustrating a flow of a network time correction process.

FIG. 4 is a diagram illustrating a configuration example of an instrumentation / control system.

FIG. 5 is a timing chart showing a calculation schedule of the MPU.

FIG. 6 is a timing chart showing an operation schedule of the network.

[Explanation of symbols]

 11 Input Device (AI) 12 Output Device (AO) 13 Controller 14 Network 15 Micro Processing Unit (MPU) 16 Communication Board 17 First Shared Memory 18 Base Board 19 Communication Module 20 Second Shared Memory 21 Internal Buffer 22 Arithmetic Processing Unit 23 input / output processing unit 24 controller time management unit 25 network time conversion / monitoring unit 26 network time management unit

Claims (4)

[Claims] 1. A network control device wherein communication means for communicating with a device on a network and calculation means for performing a calculation for controlling the device operate under time management independent of each other. A first time management unit that manages time; a network time conversion unit that determines a network time that is a reference of an operation in a network from the time managed by the first time management unit; A second time management means for managing the network time based on the time determined by the network control apparatus. 2. The network time conversion means according to claim 1, wherein said input / output processing means issues an input / output processing execution instruction from a start of an operation cycle of the network, rather than a time of an input instruction at which said arithmetic means inputs data for operation. 2. The network control device according to claim 1, wherein a time earlier by the time until the reception is set as the network time. 3. The network control device according to claim 1, further comprising a monitoring unit that monitors a phase between a time managed by the first time management unit and a network time. 4. The network control device according to claim 3, wherein said monitoring means corrects a network time and notifies said second control means when said phase exceeds a predetermined allowable range. .