JPH07280971A - Monitor control system with the synchronizing function - Google Patents

Abstract

PURPOSE:To avoid the occurrence of the overlapping of data and the failure in measurement by avoiding such inconveniences as the overlapping of the same time and the missing of a certain time in synchronizing the time indicated by a clock with a standard time. CONSTITUTION:When a terminal station receives time-setting commands sent from the central station (S1), it compare a standard time of them with the present time indicated by a clock in the terminal station to judge whether the deviation between both times is within a correctable range or not (S2). If the deviation is within a correctable range, the terminal station conducts a time-correcting process (S3). In the time-correcting process, the time indicated by the clock is corrected by compressing or extending the time base of the real time in each specified hour and converting it on the time base of the clock. On the other hand, if the deviation between both times is outside a correctable range, the terminal station conducts a compulsory time-setting process to synchronize the time indicated by the clock with the standard time forcibly (S4).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supervisory control system for monitoring and controlling equipment installed in a building or various plants, and more particularly to a time capable of time synchronization within the system. The present invention relates to a supervisory control system with a synchronization function.

[0002]

2. Description of the Related Art Modernized facilities such as buildings, plants, and highway networks have many equipments, and it is necessary to operate these equipments in cooperation with each other. It is necessary for the operation. Therefore,
It is desirable to be able to monitor the operating status of all equipment at a specific location and control all equipment from this particular location. Normally, a supervisory control system is used for such monitoring and control. .

As shown in FIG. 5, a supervisory control system system usually has a host machine 11 as a central station provided at a specific place, and operation and measuring instruments of equipment not shown at various places on the site. Programmable logic controller as a terminal station that collects data of
, Which is referred to as PLC), and the host machine 11 and each PLC 12 are connected by a network 13. Each PLC 12 ... Manages the operation of various equipments, and records data such as the state change of the equipments together with the occurrence time. Then, the recorded data is transmitted to the host machine 11 at any time in response to a request from the host machine 11.

However, when the data recorded in different PLCs 12 ... Is compared by the host machine 11, the data cannot be accurately compared unless the times of the PLCs 12 ... Therefore, each PL
By correcting the time of the clock (not shown) provided in C12 ... so as to be synchronized with the reference time of the host machine 11, it is possible to eliminate the time difference of the data to be compared.

This process is performed according to the procedure of the flowchart shown in FIG. First, the host machine 11
Issues a time setting command. This time setting command includes the above-mentioned reference time. Each PLC1
When 2 ... Receives the time setting command (S11), PL
Time setting processing is executed in C12 (S12). This time setting process is performed by forcibly synchronizing the time of the clock on the PLC 12 side with the reference time.

[0006]

However, when correcting the time on the PLC 12 side as described above, if the difference between the reference time and the time of each PLC 12 is large, the following inconvenience occurs.

For example, when the time of the PLC 12 is much later than the reference time, the time between the delays is lost, and data is missing during that time.
On the other hand, when the time of the PLC 12 is ahead of the reference time, the times between the delays appear redundantly, and there is a possibility that a plurality of different data exist at the same time.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to perform time synchronization without causing missing data or existence of different data at the same time.

[0009]

In order to solve the above-mentioned problems, a supervisory control system with a time synchronization function of the present invention is provided.
A central station that has a reference clock that generates a reference time, generates and transmits a time setting command based on the reference time, a first clock that measures real time, and a second clock that can correct the time,
The data of the equipment is updated and recorded at regular intervals by the first clock, the recording time is added to the data at predetermined intervals based on the second clock, and the recorded data is transmitted to the central station together with the recording time. When a time setting command is received from the central station, each of the terminal stations operates between the time of the second clock and the reference time generated at the central station. The determining means for determining whether the deviation is within a predetermined range or outside the predetermined range, and the real time of the first clock when the deviation between the two times is within the predetermined range by the determination by the determining means. Time correction means for correcting the time of the second clock by converting the time obtained by adding or subtracting a fixed time for each data update cycle in 1) into the time of one data update cycle in the second clock, and the determining means. To That when the deviation between the two times is outside the predetermined range in the determination, is characterized by the time setting means for setting in synchronization with the reference time of the time of the second clock is provided.

[0010]

In the above structure, each terminal station records the state change of the equipment as data. This record is
The data is recorded and updated at regular intervals based on the first clock, and the recording time of the second clock is added to the recorded data.

When the terminal station receives the time setting command transmitted from the central station, the discriminating means determines whether the deviation between the reference time of the time setting command and the time of the second clock is within a predetermined range or out of the predetermined range. It is determined whether there is any. When the difference between the two times is within the predetermined range in this determination, the time obtained by adding or subtracting a fixed time for each cycle of data update in real time by the correction means is one cycle of data update in the second clock. Is converted to time. By this conversion, the time axis of real time is compressed or expanded to become the time in the second clock.

For example, when the time of the second clock is ahead of the reference time, a fixed time is added for each data update cycle, and a time longer than the regular one cycle is set to 1 of the data update in the second clock. Convert to cycle time. As a result, the time axis of the first clock is compressed on the time axis of the second clock.
Therefore, the time of the second clock is delayed by the compressed time.

Further, when the difference between the two times is outside the predetermined range as judged by the judging means, the time setting means sets the time of the second clock in synchronization with the reference time. At this time, the time difference is too large to be corrected by the correction means, and the time of the second clock is forcibly synchronized with the reference time.

As described above, according to the above configuration, when the difference between the two times is within the predetermined range, the time axis is compressed or expanded to correct the time of the second clock, so that the time of the second clock is corrected. Is set to be synchronized with the reference time while maintaining continuity. Therefore, when synchronizing the time of the second clock with the reference time, it is possible to avoid the inconvenience of overlapping the same time or missing a certain time.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

The monitoring control system according to this embodiment is shown in FIG.
As shown in FIG. 3, the host machine 1 as a central station and a plurality of programmable logic controllers (hereinafter referred to as PLC) 2 as terminal stations are provided. The host machine 1 and each PLC 2 ... Are connected by a network 3 so that they can communicate with each other.

The host machine 1 gives a command to the PLCs 2, ...
Data such as a state change (hereinafter referred to as a state change) of each equipment transmitted from C2 ... Is collected, and the data is analyzed and the screen is displayed. Also,
The host machine 1 has a master clock 1a as a reference clock, and issues a time setting command including the reference time by the master clock 1a.

The time setting command as the time setting command, together with the reference time, gives a control output from PLC 2 to each equipment, transmits an input from each equipment to PLC 2 to host machine 1, each equipment. It includes various commands given to the PLCs 2 ...

The PLC 2 is connected with various equipments such as relay contacts, motors, measuring instruments, etc., and controls the operation of these equipments, changes the conditions from the equipments, inputs measured values, and inputs them. It has a data recording function that records values as data. The recorded data includes data that is deleted from the recording when it is transmitted to the host machine 1 and other stations (PLC2 ...), and data that is held for a fixed amount or for a fixed time.

The above-mentioned PLC2 is the first for measuring real time.
It has a timepiece 2a as a timepiece and a timepiece 2b as a second timepiece capable of time correction.
b is composed of software. Also, PL
The C2 updates the recording of data at regular intervals based on the clock 2a, and adds a time stamp as a recording time to the recorded data based on the clock 2b. Further, when the PLC 2 receives the time setting command from the host machine 1, the PLC 2 performs the forced time setting process or the time correction process according to the difference between the time of the clock 2b and the reference time of the time setting command.

The forced time setting process is the same process as the time setting in the conventional supervisory control system and directly synchronizes the time of the clock 2b with the reference time. PLC2
By performing this process, the device has a function as time setting means. On the other hand, the time correction processing compresses or expands the time axis of the timepiece 2a in the unit of the update cycle of data recording so as to eliminate the time difference of the timepiece 2b from the reference time, and converts it into the time axis of the timepiece 2b. , The time of the clock 2b is corrected.
The PLC 2 has a function as a time correction means by performing this process.

Here, a concrete example of the time correction processing will be described. Below, the update cycle of data recording is set to 10 ms,
A case where time stamps occur at 1 ms intervals will be described.

When the current time of the clock 2b is advanced by 5 ms from the reference time included in the time setting command, as shown in FIG. 3, the real time of the clock 2a is 11 ms (10 ms).
Is added to 1 ms for correction) as one cycle, and this one cycle is converted into a logical time of 10 ms by the clock 2b. Specifically, the time axis is compressed by multiplying the time stamp of the state change and the measured value that occurred during one cycle of 11 ms in real time by 10/11. As a result, 55 ms in real time is compressed to 50 ms which is a logical time, the time of the clock 2b is delayed by 5 ms and set in synchronization with the reference time.

By compressing the time axis in this way, the time stamp of the recorded data is rewritten. Therefore, for example, the state change that occurred immediately before the end of one cycle (11 ms) in real time is considered to have occurred immediately before the end of one cycle (10 ms) in the logical time.

On the contrary, when the current time of the clock 2b is delayed by 5 ms from the reference time included in the time setting command,
As shown in, 9ms (1
The time obtained by subtracting 1 ms for correction from 0 ms) is set as one cycle, and this one cycle is converted into a logical time of 10 ms by the clock 2b. Specifically, the time axis is expanded by multiplying the time stamp of the state change and the measured value that occurred during one cycle of 9 ms in real time by 10/9. This allows
45ms in real time is expanded to 50ms in logic time,
The time of the clock 2b is advanced by 5 ms and set in synchronization with the reference time.

By extending the time axis in this way, the time stamp of the recorded data is rewritten. Therefore, for example, the state change that occurred immediately before the end of one cycle (9 ms) in real time is considered to have occurred immediately before the end of one cycle (10 ms) in logical time.

In the above example, the data update cycle 1
Although the time is corrected by 1 ms, which is 10% of 0 ms, it is possible to shorten the time required for the time correction. In this case, for example, the time is corrected every 2 ms or 3 ms with respect to the data update cycle of 10 ms. These settings are made in advance and appropriately differ depending on the system. Also, the logical time after the end of the time correction process is
Return to the normal time axis, that is, the same time axis as the real time axis.

In the PLC 2, which of the forced time setting process and the time correction process should be executed is whether the difference between the two times is within a predetermined range determined by a threshold value or outside the predetermined range. Is determined by. The threshold value sets a range of deviation in which time correction processing is possible, and varies depending on the processing speed of the system.
In this embodiment, it is set to 100 ms, for example. The PLC 2 has a function as a determination means by making this determination.

The above-mentioned time correction means, time setting means, and determination means are functions realized by software, and the respective processing is performed by the processing unit (CPU) in the PLC 2.
Etc.) according to a predetermined program.

The procedure for setting the time in the above configuration will be described with reference to the flowchart of FIG.

First, a time setting command is issued from the host machine 1, and this time setting command is sent to the network 3
Through PLC2 ... When the PLC 2 receives the time setting command (S1), the reference time is compared with the current time of the timepiece 2b to determine whether the deviation between the two times is within the correction range (S2).

If the difference between the two times is within the correction range,
The time correction process is performed as described above (S3).
At this time, whether to delay or advance the time of the clock 2b
It is determined by whether it is ahead or behind the reference time. When the time of the clock 2b is advanced, the process of delaying the time is performed, and conversely, when the time of the clock 2b is delayed, the process of advancing the time is performed.

On the other hand, if the difference between the two times is out of the correction range, the forced time setting process is performed (S4). At this time, the current time of the clock 2b is adjusted to the reference time regardless of whether it is ahead or behind the reference time.

As described above, in the supervisory control system of this embodiment, the time is corrected by performing the time correction process.
The time of b is set in synchronization with the reference time in a state where continuity is maintained. Therefore, when synchronizing the time of the clock 2b with the reference time, it is possible to avoid the inconvenience that the same time is duplicated or a certain time is missing.

[0035]

As described above, the supervisory control system with the time synchronization function of the present invention has the reference clock for generating the reference time, and the central station for generating and transmitting the time setting command based on the reference time, It has a first clock that counts real time and a second clock that can correct the time, and updates the data of facility equipment at regular intervals by the first clock and records the data, and a predetermined time based on the second clock in the data. Recording time is added for each interval,
A plurality of terminal stations for transmitting the recorded data together with the recording time to the central office are provided. When each terminal station receives the time setting command from the central office, the time of the second clock is recorded. Judgment means for judging whether the deviation from the reference time generated at the central office is within a predetermined range or outside the predetermined range, and the deviation between both times is within a predetermined range by the judgment by the judgment means. The above first when
Time correction means for correcting the time of the second clock by converting the time obtained by adding or subtracting a fixed time for each data update cycle in real time of the clock into the time of one data update cycle in the second clock. And a time setting means for setting the time of the second clock in synchronization with the reference time when the difference between the two times is outside the predetermined range as judged by the judging means.

As a result, if the difference between both times is within the predetermined range, the time axis of the real time of the first clock is compressed or expanded and converted into the time of the second clock. By performing such a correction, the time of the second clock is set in synchronization with the reference time while maintaining continuity. therefore,
When synchronizing the time of the second clock with the reference time, it is possible to avoid the inconvenience of overlapping the same time or missing a certain time. As a result, it is possible to avoid the duplication of data and the occurrence of missing data.

[Brief description of drawings]

FIG. 1 is a flowchart showing a procedure of a time setting process of a supervisory control system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of the monitoring control system.

FIG. 3 is an explanatory diagram showing a time correction process by the supervisory control system of FIG. 2 when the current time of the time stamp adding clock in the programmable logic controller is ahead of the reference time.

FIG. 4 is an explanatory diagram showing a time correction process by the supervisory control system of FIG. 2 when the current time of the time stamp adding clock in the programmable logic controller is behind the reference time.

FIG. 5 is a block diagram showing a schematic configuration of a conventional supervisory control system.

6 is a flowchart showing a procedure of time setting processing by the monitoring control system of FIG.

[Explanation of symbols]

1 host machine (central station) 1a master clock (reference clock) 2 programmable logic controller (terminal station,
Determination means, time correction means, time setting means) 2a clock (first clock) 2b clock (second clock)

Claims (1)

[Claims] 1. A central station having a reference clock for generating a reference time, generating and transmitting a time setting command based on the reference time, a first clock for measuring real time, and a second clock for correcting the time. The data of the equipment is updated and recorded at regular intervals by the first clock, the recording time is added to the data at predetermined intervals based on the second clock, and the recorded data is recorded together with the recording time. It is provided with a plurality of terminal stations for transmitting to the central station, and each of the terminal stations receives the time setting command from the central station,
Judgment means for judging whether the deviation between the time of the clock and the reference time generated at the central office is within a predetermined range or outside the predetermined range, and the deviation between both times by the judgment by the judgment means. Is within a predetermined range, the time obtained by adding or subtracting a constant time for each cycle of data update in the real time of the first clock is converted into a time of one cycle of data update in the second clock. A time correction unit that corrects the time of the second clock and a time that is set by synchronizing the time of the second clock with the reference time when the difference between the two times is outside the predetermined range as determined by the determination unit. A monitoring control system with a time synchronization function, characterized in that setting means is provided.