JPH0152762B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention provides that when a program is created such that a specific output contact is ON for a certain period of time when a controlled object operates normally, the ON time of the output contact is A programmable logic controller (hereinafter referred to as a
It is called PLC. ) regarding an abnormality determination method.

For example, when using a PLC to move a workpiece a certain distance while processing it on an NC machine tool, the contact of the PLC's output relay is turned on to start the motor, and then the workpiece reaches a predetermined position. Normally, a limit switch or the like is used to detect this, and this detection signal is used to turn off the contacts of the output relay to stop or reverse the motor.

In this case, if the above machining process is performed normally, the time that the output relay contact is ON should be almost constant; on the other hand, the ON time of the contact may be extremely long. Alternatively, if it is short, it can be detected that some kind of abnormality has occurred in the processing process.

Therefore, conventional PLCs are equipped with a function that issues an alarm when the ON time of an output relay deviates from a specified range.
However, since this PLC manually sets the maximum or minimum ON time as a reference, when handling a controlled object whose ON time fluctuates even under normal conditions, the maximum or minimum ON time must be set manually. However, it is difficult to set the minimum ON time, and therefore, even if an abnormality detection function based on the ON time of the output contact is provided, it cannot be fully utilized.

This invention was devised in view of the above problem, and its purpose is to simplify as much as possible the setting of the allowable value of ON time (or OFF time) in a PLC equipped with this kind of abnormality detection function. That is.

In other words, the PLC abnormality determination method according to the present invention involves calculating the maximum and minimum ON time (or OFF time) of the output relay while repeatedly operating the controlled object by executing a normal sequence program. While executing the program and actually operating the controlled object, if the ON time (or OFF time) of each output relay exceeds the range of the maximum and minimum ON time (or OFF time) determined above, This is characterized by determining that there is an abnormality in the controlled object.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 1 is a block diagram showing the system configuration of the PLC according to the present invention, Fig. 2 is a wiring diagram schematically showing the output section of the PLC, and Fig. 3 is a time diagram showing the relationship between the operation of the monitor relay and the timer clock. Chart, Figure 4 is a front view showing an example of the layout of the operation panel, Figure 5 is a memory map showing the contents of the RAM working area, Figure 6 is a general flowchart showing PLC operation, and Figure 7 is error handling. Flowchart showing the details of the routine. FIG. 8 is a flowchart showing the details of the search routine.

In Figure 1, 1 is a CPU for overall control of the entire system, 2 is a ROM for storing system programs, 3 is a RAM for storing user programs, and 4 is a reference timer block for calculating ON time, which will be described later. 5 is a timer clock generator that outputs
When there is an error in the ON time, the error output relay
6 is a mode input circuit that generates a predetermined logical output in response to the operation of the mode selector switch MS, 7 is a search switch SS
A search input circuit that emits a predetermined logical output in response to the operation of , 8 is the ON of the contact of either output relay.
An error indicator 9 displays the number of the output relay when an error occurs in the time, and 9 is an interface circuit for inputting the ON/OFF status of the monitor relay to the CPU 1, which will be described later. are connected to each other through.

This PLC is provided with N output relays consisting of X ₁ to X _N , and each output relay X ₁ to X _N
are each equipped with a monitor relay as shown in Figure 2.
X ₁ a to X _N a are connected in parallel. Therefore,
When the output relays X ₁ to X _N are turned on, the monitor relays X _{1 a} to X _N a are also turned on in response to this. And relay for each monitor x _1a
The ON/OFF state of the a contact of ~X _N a is sent onto the data bus line 12 via the monitor circuit 11 as shown in FIG. 1, and is taken into the latch circuit 13 in response to a timing signal from the CPU 1. It is configured as follows.

In addition, in this example, the operation panel 14 is provided with the above-mentioned abnormality indicator 8, mode changeover switch MS, search switch SS, and external output terminals 15 of the abnormality output relay X, as shown in FIG. The device 8 is configured to display one corresponding number of the output relay related to the abnormality.

On the other hand, in addition to the user program writing area necessary for normal operation of the PLC, RAM3 contains a
As shown in the figure, 3 consists of the current value, minimum value, and maximum value.
Types of registers R ₁ c ~ R _N c, R _1M ~ R _NM , R ₁ x ~
R _N x is provided by the number of output relays, and
In the working area, as shown in Figure 5, there are error flags that memorize malfunctions of each output relay _X1 to _XN .
EF, search start flag S for storing whether or not it is the first operation of the search button during the search operation described later, error stack ES for sequentially storing the numbers of output relays related to abnormal operation, error stack ES
An error pointer EP or the like is provided to store each address of the error stack when successively proceeding from each storage area.

On the other hand, the ROM 2 stores system programs as shown in the flowcharts of FIGS. 6, 7, and 8 for carrying out the present invention.

Next, the operation of this PLC will be explained according to the flowcharts shown in FIGS. 6, 7, and 8.

First, the specific execution contents of each routine shown in FIGS. 6 to 8 will be explained.

"Routine R ₁ ": The output of the search input circuit 7 is taken into the CPU 1, and it is determined whether the content is "1" (measurement mode).

"Routine R ₂ "; The Q ₁ output of the latch circuit 13 indicating the ON/OFF state of the monitor relay X ₁ a is taken into the CPU 1,
The content is “1” (monitor relay X ₁ a is ON)
Determine whether or not.

"Routine R ₃ ": The output of the timer clock generator 4 is taken into the CPU 1, and it is determined whether the content is "1" and the previous content is "0" (timer clock rising).

"Routine _R4 " Adds 1 to the contents of the current value register _R1c corresponding to the relay _X1a in RAM3.

"Routine R ₅ "; The Q ₁ output of the latch circuit 13 is taken into the CPU 1, and its content is "0" and the previous content is "1" (relay X ₁ a is turned OFF).
Determine whether or not.

“Routine R ₆ ”: Determine whether the contents of the current value register R ₁ c corresponding to the relay X ₁ a in the RAM 3 are larger than the contents of the maximum value register R ₁ x.

"Routine R ₇ "; Maximum value register with the contents of current value register R ₁ c
Replace the contents of R ₁ x.

“Routine R ₈ ”; Stores 0 in the current value register R ₁ c.

"Routine R ₉ ": Determine whether the contents of the current value register R ₁ c are smaller than the contents of the minimum value register R _1M .

"Routine ₁₀ "; The contents of the current value register _R1c are used as the minimum value register.
Replace the contents of R _1M .

"Routine R ₁₁ "; Stores 0 in the current value register R ₁ c.

"Routine R ₁₂ ": The output of the search input circuit 7 is taken into the CPU 1, and it is determined whether the content is "0" (RUN mode).

“Routine R ₁₃ ”: Determine whether the content of the error flag EF corresponding to the relay X ₁ a in the RAM 3 is “1” (indicating an abnormality).

"Routine R ₁₄ "; The Q ₁ output of the latch circuit 13 is taken into the CPU 1, and its content is "1" (the monitor relay X ₁ a is
ON).

"Routine R ₁₅ "; The output of the timer clock generator 4 is taken into the CPU 1, and it is determined whether its content is "1" and the previous content is "0" (timer clock rising).

"Routine R ₁₆ "; Adds 1 to the contents of the current value register R ₁ c.

"Routine R ₁₇ "; The Q ₁ output of the latch circuit 13 is taken into the CPU 1, and its content is "0" and the previous content is "1" (relay X ₁ a is turned OFF).
Determine whether or not.

"Routine R ₁₈ ": Determine whether the contents of the current value register R ₁ c are smaller than the contents of the maximum value register R ₁ x.

"Routine R ₁₉ ": Determine whether the contents of the current value register R ₁ c are greater than the contents of the minimum value register R _1M .

"Routine R ₂₀ ": As shown in FIG. 7, it is composed of "routine R ₂₀₁ " to "routine R ₂₀₇ ".

"Routine R ₂₀₁ "; Reads the relay number (1 to N) related to the abnormality.

"Routine R ₂₀₂ "; The relay number read in the routine R ₂₀₁ is stored in the error stack ES.

"Routine R ₂₀₃ "; Error flag corresponding to the relay related to the error
Set the contents of EF to “1”.

"Routine R ₂₀₄ "; The state of the abnormal output relay X is taken into the CPU 1, and it is determined whether the content is "0" (OFF state).

"Routine R ₂₀₅ "; error stack specified by error pointer EP
The number of the abnormality relay is read from the storage area in the ES and displayed on the abnormality display 8.

"Routine R ₂₀₆ "; Drives the abnormal output circuit 5 and outputs the abnormal output relay
Turn on.

"Routine R ₂₀₇ "; Updates the contents of the error pointer EP by one.

"Routine R ₂₁ ": The output of the search input circuit 7 is taken into the CPU 1, and it is determined whether the content is "1" and the previous content was "0" (search switch SS was turned on).

"Routine R ₂₂ "; As shown in FIG. 8, it is composed of "Routine R ₂₂₁ " and "Routine R _226. "

"Routine R ₂₂₁ ": Determine whether the content of the search flag S is "1" (first search switch ON).

"Routine R ₂₂₂ ": Updates the contents of the search counter SC by one.

"Routine R ₂₂₃ ": Reads the number of the abnormal relay from the error stack ES at the address specified by the contents of the search counter SC.

"Routine R ₂₂₄ "; The number of the abnormality relay that has been read out is displayed on the abnormality display 8.

"Routine R ₂₂₅ ": Set the start address of the error stack ES in the search counter SC.

"Routine R ₂₂₆ " Set the search start flag S to "1" (indicating the second or subsequent search switch operation).

In FIG. 6, the portions surrounded by dotted lines indicate programs that are completely similar to routines R ₁ to R ₂₂ for monitoring relays X ₂ a to X _Na , respectively.

Next, the operation of this PLC will be explained starting from the measurement mode. Mode changeover switch shown in Figure 4
Set the MS to the measurement side, run the normal sequence program of this PLC, and repeatedly test drive the controlled object. At this time, for example, if the monitor relay X ₁ a is OFF. routine
RR ₁ (YES) → Routine R ₂ (NO) → Routine R ₅
(NO) and no measurement operation is performed. When monitor relay X ₁ a turns ON from this state, routine R ₁ (YES) → Routine R ₂ (YES) → Routine
R ₃ (YES) → Routine R ₄ or Routine R ₃ (NO)
Therefore, each time the timer clock shown in Fig. 3 arrives, 1 is added to the current value register R ₁ c, and the ON value of the monitor relay X ₁ a, which is represented by the count value of the timer clock, is added to the current value register R ₁ c. Time data is formed.

Next, when monitor relay X ₁ a turns OFF, routine R ₁ (YES) → Routine R ₂ (NO) → Routine R ₅ (YES) → Routine R ₆ (YES) → Routine R ₇
→ Routine R ₈ or R ₆ (NO) → Routine R ₉
(YES) → Routine R ₁₀ → Routine R ₁₁
Minimum value register corresponding to monitoring relay X ₁ a
R _1M and maximum value register R ₁ x are monitor relays.
The maximum X ₁ a has been turned ON up to that point
The ON time data and the minimum ON time data are stored respectively, and the contents of the current value register R ₁ c are cleared to 0.

In this way, _the measurement program for monitor relay X ₁ a is executed, but at the same time, a similar program is executed sequentially for monitor relays X ₂ a, relay for
When the execution of the program for X _Na is completed, the process returns to the first monitoring relay X ₁ a and the maximum ON time and minimum ON time data are repeatedly formed.

Next, the operation in RUN mode will be explained. First, a controlled object (for example, an NC machine tool, etc.) is actually operated according to a PLC sequence program. In this state, if the mode changeover switch MS shown in Fig _{. 4 is set to the RUN side, the ON time of the monitor relay X 1 a} will change if there has been no abnormality in the past and if the monitor relay ,
Routine R ₁ (NO) → Routine R ₁₂ (YES) → Routine R ₁₃ (YES) → Routine R ₁₄ (NO) → Routine
R ₁₇ (NO) → Routine R ₂₃ and the contents of the current value register R ₁ c are cleared to 0. If monitor relay X ₁ a turns on in this state, the routine
R ₁ (NO) → Routine R ₁₂ (YES) → Routine R ₁₃
(YES) → Routine R ₁₄ (YES) → Routine R ₁₅
(YES) or (NO), and each time the timer clock arrives, routine _R16 is executed and 1 is added to the current value register _R1c , thereby forming ON time data at that time.

Next, when monitor relay X ₁ a turns OFF, routine R ₁ (NO) → Routine R ₁₂ (YES) → Routine R ₁₃ (YES) → Routine R ₁₄ (NO) → Routine
R ₁₇ (YES), and if there is no abnormality in the ON time of monitor relay R ₁ a in this state, the routine R ₁₈ (NO) → Routine R ₁₉ (NO) continues.
Therefore, no abnormal output is generated. On the other hand, if the current ON time data formed in the current value register R ₁ c is smaller than the minimum ON time data stored in the minimum value register R _1M , the routine R ₁₈ (YES) →routine
R ₂₀ and the current ON time data formed in the current value register R ₁ c is greater than the maximum ON time data stored in the maximum value register R ₁ x, then the routine R ₁₈ (NO )→
Routine R ₁₉ (YES)→routine R ₂₀ , and in either case, abnormality handling routine R ₂₀ is executed.

Then, in the abnormality processing routine R ₂₀ , routine R ₂₀₁ → routine R ₂₀₂ → routine R ₂₀₃ are executed in sequence, and the number "1" of the monitor relay X ₁ a is stored at the first address of the error stack ES. Error flag corresponding to monitor relay X _1a
EF is set to "1". Next, if abnormal output relay X is OFF in this state, routine R ₂₀₄ (YES) → routine R ₂₀₅ → routine
R ₂₀₆ → Routine R ₂₀₇ , and the error indicator 8 shows the number "1" of the monitor relay X ₁ a related to the error.
is displayed and abnormal output relay X is turned ON.
The contents of the error pointer EP are updated by one. On the other hand, abnormal output relay
If it is ON, the routine goes from routine R ₂₀₄ (NO) to routine R ₂₀₇ , and only the error pointer EP is updated, and then the process returns to the main routine.

In this way, _the abnormality determination program for monitor relay X ₁ a is executed, but at the same time, similar programs are executed sequentially for monitor relays X ₂ a, When the execution of the program for the monitor relay X _Na is completed, routine _R21 is executed. At this time, when the search switch SS is turned on, routine R ₂₁
(YES) → Routine R ₂₂ and the search program shown in FIG. 8 is executed. The search program turns on multiple monitor relays X ₁ a to X _N a at the same time.
When an abnormality occurs in time, the numbers of these relays are displayed one by one on the abnormality display 8.

That is, when the search switch SS is turned ON for the first time, the sequence is routine R ₂₂₁ (NO) → routine R ₂₂₅ → routine R ₂₂₆ → routine R ₂₂₃ → routine R ₂₂₄ , and the search counter SC is set to the start address of the error stack ES. At the same time, the search start flag S is set to "1", and the relay number stored at the start address of the error stack ES specified by the search counter SC is read out, and this relay number is displayed on the error indicator 8. be done.

Next, when the search switch SS is turned on for the second time, routine R ₂₂₁ (YES) → routine R ₂₂₂ →
Routine R ₂₂₃ → Routine R ₂₂₄ , the content of the search counter SC is updated by 1, the relay number stored in the error stack ES at the address specified by this updated content is read out, and an error is displayed in the same way. displayed on the display 8.

In this way, each time the search switch SS is turned ON, the numbers of the abnormality relays stored in the elastic stack ES are read out in sequence, and the abnormality display 8 is read out.
is displayed.

Thus, in the PLC shown in this example,
If you repeatedly test run the controlled object after setting the mode changeover switch MS to the measurement side, the maximum and minimum ON times of all output relays X ₁ to Xa can be changed through the operation of monitor relays X ₁ to X _N a. It can be automatically calculated and set, and even when the controlled object has a fluctuation range in ON time even under normal operating conditions, the appropriate maximum and minimum ON values can be set.
You can set the time.

In addition, to detect each maximum and minimum ON time, connect monitor relays X _{1 a} to X _N a in parallel to each output relay X ₁ to X _N , and detect the ON and OFF states of their contacts. As a result, the hardware configuration becomes extremely simple.

Furthermore, when determining that the operation of each output relay X ₁ to X _N is abnormal, it is determined that the actual ON time is not within a certain upper and lower limit range. Compared to the conventional example where only one of the lower limits is used as a criterion,
Abnormalities in the controlled object can be detected even more accurately.

Incidentally, in this embodiment, the abnormality of the controlled object was determined based on the ON time of each relay, but the same effect can be obtained by using the OFF time.

As is clear from the above explanation, this invention relates to
The PLC abnormality determination method is to run a normal sequence program and repeatedly operate the controlled object, while the output relay's maximum and minimum ON times (or
The ON time (or OFF time) of each output relay is determined by calculating the maximum and minimum ON time (or OFF time) while executing a normal sequence program and actually operating the controlled object. Since the structure is configured so that it is determined that there is an abnormality in the controlled object when the time exceeds the range of (time), the following effects can be achieved.

(a) In a PLC equipped with this type of abnormality detection function, it is easier to set the allowable value for ON time (or OFF time), improving operability.

(b) Also, according to the present invention, the ON time (or OFF time) of each output relay during actual operation is the maximum and minimum ON time (or
When the OFF time is exceeded, it is determined that there is an abnormality in the controlled device and a notification to that effect is output. This prevents the controlled device from running out of control or being damaged.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the system configuration of the PLC according to the present invention, Fig. 2 is a wiring diagram schematically showing the output section of the PLC, and Fig. 3 is a time diagram showing the relationship between the operation of the monitor relay and the timer clock. Chart, Figure 4 is a front view showing an example of the layout of the operation panel, Figure 5 is a memory map showing the contents of the RAM working area, Figure 6 is a general flowchart showing PLC operation, and Figure 7 is error handling. Flowchart showing the details of the routine. FIG. 8 is a flowchart showing the details of the search routine. X ₁ to X _N ... Output relay, MS... Mode changeover switch, R _{1 c} to R _N c... Current value register, R ₁ x
~R _N x... Maximum value register, R _1M ~ R _NM ... Minimum value register.

Claims (1)

[Claims] 1 Execute the normal sequence program and repeatedly operate the controlled object, calculate the maximum and minimum ON time (or OFF time) of the output relay, and then execute the normal sequence program and actually operate the controlled object. while each output relay is
An abnormality in a programmable logic controller characterized in that when the ON time (or OFF time) exceeds the range of the determined maximum and minimum ON time (or OFF time), it is determined that there is an abnormality in the controlled object. Judgment method.