JPH10150458A - Terminal station monitor system by polling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the monitor system of this kind in which the number of times of confirmation of an abnormal station is changed dynamically in response to a state in a loop and polling is progressed without receiving a temporal failure of a transmission line. SOLUTION: The number of times of re-transmission of a polling request frame to one terminal station is selected to be once to twice and when no reply is received, the station is stored as an abnormal candidate station, polling is transferred to a succeeding terminal station and when the polling with respect to all terminal stations is circulated and a turn of the abnormal candidate station comes round, polling is sent again only once and when no reply comes, the similar processing is conducted in a succeeding polling cycle, and when the terminal station is regarded to be a faulty station when no reply comes for prescribed number N and the faulty station is excluded from the polling cycle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of monitoring a plurality of terminal stations by polling from a monitoring station.

[0002]

2. Description of the Related Art As a method of monitoring a change in the state of various control devices, various control terminals (terminal stations) are connected in a loop, and one or two monitoring stations are installed in the loop. A polling frame is sequentially transmitted to the terminal station, and by returning a normal polling response frame from the terminal station,
There is a method of collecting and monitoring the status of the terminal station.

FIG. 2 is a conceptual diagram of a method of monitoring a plurality of terminal stations by polling. Reference numeral 1 denotes a monitoring station, 2 denotes a terminal station, and a plurality of terminal stations 2-1 to 2-2... The terminal stations 2-1 to 2-n and the monitoring station 1 are connected in a loop. Then, the monitoring station 1 transmits a polling request frame to one terminal station, and if an expected polling response frame is returned within a specified time, determines that the terminal station is operating normally, Go to the next terminal station polling.

If the polling response frame is not returned within the specified time, it is determined that the terminal station itself or the transmission path between the terminal station and the monitoring station has some trouble, and the polling request frame of the specified number of times is returned. Attempt resend,
If no response is finally obtained, the terminal station is determined as an abnormal station and is excluded from the polling cycle.

[0005]

In the above-mentioned monitoring system based on polling, whether the terminal station itself has no abnormality and returns a normal polling response frame,
Or, in spite of being able to return, the polling frame may not be able to reach either station due to a temporary failure of the transmission path such as noise or momentary disconnection.

In this case, in order to prevent the instantaneous failure from being mistaken as an abnormality of the terminal station, the monitoring station attempts to retransmit the polling request frame continuously to the terminal station up to a specified number of times. Only when no response can be obtained, the terminal station becomes abnormal.

[0007] However, if the specified number of retransmissions at this time is small, there is a high possibility that a temporary failure in the transmission path cannot be avoided. Conversely, if the number is large, polling of other normal terminal stations is delayed, polling performance is reduced, and real-time state detection is sacrificed. Also,
There is a problem that the influence increases as the number of such abnormal stations increases in the loop.

In view of the above, the present invention is capable of dynamically changing the number of times of confirming an abnormal station in accordance with the state in a loop, and allowing polling to proceed without a temporary failure in a transmission line. It is an object of the present invention to provide such a monitoring method that can be performed.

[0009]

Means for solving the above-mentioned problems in the present invention, means for avoiding a temporary failure of a transmission line and for minimizing a decrease in polling performance are as follows: The retransmission of the polling request frame is performed once or twice. If the expected response is not obtained, the polling request frame is sent to the next terminal station. This first prevents the polling performance from deteriorating. At this time, the previous terminal station is not regarded as abnormal, but is recognized (stored) as an abnormal candidate station.

(2) When the polling for all the terminal stations has completed one cycle (one polling cycle) and the order of the abnormal candidate stations is first, the retransmission to the abnormal candidate station is performed once again. If the expected response is still not obtained, the same processing is performed in the next polling cycle. (Hereinafter, a series of operations for this abnormal candidate station will be referred to as abnormal station confirmation.) Is regarded as abnormal. At this time, by dynamically calculating the number N of abnormal station confirmations according to the following equation, it is possible to prevent a false recognition due to a temporary failure in the transmission path and to minimize the delay of the terminal station abnormality detection.

N = Te / Ts Te: Time sufficient for recovery from a temporary failure in the transmission path (experience value) Ts: Time required for a polling cycle Ts = Sn × Tp Sn: Normal in the current loop Number of stations (changes dynamically) Tp: Polling time required for terminal station (measured value) (4) Terminal stations regarded as abnormal stations are excluded from the polling cycle, and polling continues for abnormal stations. I will not do it. This prevents the presence of the abnormal station from lowering the polling performance for the normal station.

(5) For an abnormal station, polling is performed only once for each abnormal station per polling cycle, and the restoration of the state of the abnormal station is monitored. Thus, if the status of the terminal station once regarded as an abnormal station recovers, the terminal station can return to the normal station polling cycle.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a flowchart according to an embodiment of the present invention. In step S1, the monitoring station sends a polling request frame to one terminal station. Next, step S
In step 2, it is determined whether or not the polling request frame has been retransmitted to the terminal station.
At 3, the polling is transferred to the next terminal station. If there is no response even after one or more frame retransmissions, the terminal station is stored as an abnormal candidate station in step S4, and polling is transferred to the next terminal station.

Next, the terminal station that has received the polling determines whether or not the terminal station is an abnormal candidate terminal station. If the terminal station is an abnormal candidate terminal station, it retransmits only once. If not, return to step S1 and repeat (S5, S6).

When retransmission of polling to the abnormal candidate station is performed in step S6, it is determined in step S7 whether an expected response is obtained. If no response is received, no response is returned in step S8 (abnormal station). It is determined whether the number of times (confirmation) is a predetermined number of times N. If an expected response is not obtained even after performing the number N times, the terminal station is regarded as abnormal and is excluded from the polling cycle (step S9).

When resending in step S6, step S6
If a response is received in step 7, the abnormal candidate station is restored to the normal station in the next cycle in step S10, and
At 11, the polling is transferred to the next terminal station. Also, if there is no response within N times in step S8, the polling is moved to the next terminal station in step S11.

[0018]

As described above, according to the present invention, retransmission of a polling request frame to one terminal station is performed once or twice, and if an expected response is not obtained even after that, the polling request frame is stored as an abnormal candidate station, and polling is performed next. When the polling for all the terminal stations has been completed and the order of the abnormal candidate station has been reached, the polling is re-transmitted once again to the abnormal candidate to confirm the abnormal station, and the expected response is still obtained. If the response is not obtained, the same processing is further performed in the next polling cycle. Even if this abnormality check is performed a predetermined (calculated) N times, the expected response is still not obtained from the terminal station. Since the terminal station is regarded as abnormal for the first time and excluded from the polling cycle, (1) the polling cycle proceeds without being affected by a temporary failure of the transmission line. Can be run.

(2) It is possible to prevent a decrease in polling performance due to an increase in abnormal stations.

The above effect is obtained.

[Brief description of the drawings]

FIG. 1 is a flowchart of an embodiment of the present invention.

FIG. 2 is a conceptual diagram of a station monitoring method using polling.

[Explanation of symbols]

 1: Monitoring station 2: Terminal station

Claims (3)

[Claims] 1. A plurality of terminal stations are connected in a loop, one or two monitoring stations are installed in the loop, polling is sequentially performed from the monitoring stations to each terminal station, and a response from the terminal station is performed. In a terminal station monitoring method based on polling, which collects and monitors the state of terminal stations by frames, a polling request frame is sent from a monitoring station to one terminal station, and if there is no expected response, the polling request frame is retransmitted once or twice. Further, if no response is obtained, the terminal station is stored as an abnormal candidate station, polling is moved to the next terminal station, polling for all terminal stations is completed, and the order of the abnormal candidate stations is reached. Sometimes, once again
The polling is retransmitted to the abnormal candidate station only once, and the abnormal station is confirmed. If the expected response is not obtained, the same processing is performed in the next polling cycle, and the abnormal station is confirmed N times. If the expected response is not obtained, the terminal station is regarded as abnormal and is excluded from the polling cycle. 2. A terminal station excluded as an abnormal station is polled only once per abnormal station per polling cycle, and the state of the abnormal station is monitored. 2. The terminal station monitoring system by polling according to claim 1, wherein the terminal station is returned to a polling cycle of a normal station. 3. The terminal station monitoring method by polling according to claim 1, wherein the number of times N at which an abnormal station is confirmed is dynamically calculated by the following equation. N = Te / Ts Ts = Sn × Tp Here, Te is a time (experience value) sufficient to recover from a temporary failure of the transmission line, and Ts is a time required for one polling cycle. Sn is the number of normal stations in the current loop (dynamically changed) Tp is the polling time (measured value) required for one terminal station