JP4131134B2 - Control device, input circuit thereof, and signal input method of control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device such as a programmable logic controller (PLC), an input circuit thereof, and a signal input method.
[0002]
[Prior art]
A safety device such as a safety light curtain or a safety area sensor may be connected to the PLC input circuit. Generally, the output signal of the safety device is normally an on signal, and is switched to an off signal when an entry to the detection area is detected. That is, the signal output when the safety device is activated is a step signal for switching from the on state to the off state. Then, the main body of the PLC that has received this step signal performs a predetermined sequence process, for example, an emergency stop of the system.
[0003]
By the way, recent safety devices regularly output pulse signals for self-diagnosis. This pulse signal is an off signal with an extremely short pulse width (for example, 20 μsec), and this pulse signal is fed back to the safety device itself to confirm that there is no abnormality in the output system. Here, in the PLC with low reception sensitivity, the pulse signal for self-diagnosis is ignored, but in the PLC with high reception sensitivity, particularly in the so-called safety PLC in which the safety standard is set to a high level, the pulse signal for self-diagnosis is used. Will also be detected.
[0004]
Therefore, in the conventional example, a PLC input circuit provided with a capacitor or a coil for delaying the response time is known. As another conventional example, when it is detected that the signal received by the PLC input circuit is turned off, the detection operation is further performed three times, and if two or more of them are in the on state, the signal is received. A configuration is known in which the signal is ignored and the received signal is taken into the main body of the PLC when it is not.
[0005]
[Problems to be solved by the invention]
However, in the conventional device described above, if a capacitor or a coil for delaying the response time is provided, the responsiveness deteriorates even with respect to a signal output by the safety device during operation. In addition, since the output specifications of the self-diagnosis pulse differ depending on the manufacturer of the safety device, in the case of performing the detection operation three times, for example, one self-diagnosis pulse having a large pulse width includes three detection operations. There could be a situation where the detection operation overlaps with a plurality of self-diagnosis pulses that are continuously output. For this reason, in the prior art, it was considered that the self-diagnosis pulse was mistakenly taken as an operation signal and was taken into the main body of the PLC.
[0006]
The present invention has been made in view of the above circumstances, and a control device capable of performing stable sequence control even when an external device that outputs a pulse signal for self-diagnosis is connected, its input circuit, and signal input method The purpose is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the signal input method of the control device according to the invention of claim 1 selects the pulse signal for self-diagnosis received from the external device and the step signal for operation output, This is a signal input method for the control device that takes only the step signal for output during operation into the control device body, and the signal received from the external device is inverted when the interval period elapses after the signal is inverted relative to the normal state. In the time zone when the self-diagnosis pulse signal is not generated, the received signal is taken into the main body of the control device only when it remains inverted. It is characterized in that the interval period is set so as to perform detection.
[0008]
An input circuit of a control device according to a second aspect of the invention selects a pulse signal for self-diagnosis received from an external device and a step signal for operation output, and controls only the step signal for operation output. An input circuit of a control device to be taken into the main body, the first detection means for detecting that the received signal from the external device is inverted with respect to the normal state, and the interval period after the first detection means detects the inversion When the time elapses, the second detection means for detecting whether or not the received signal remains inverted and the detection result of the second detecting means are received and the received signal is controlled only when the received signal remains inverted. And a signal selection means to be incorporated into the apparatus main body, and the interval period is set so that the second detection means is detected in a time zone in which a pulse signal for self-diagnosis is not generated, corresponding to the specifications of the external device. Shi Having the features in place.
[0009]
The control device according to the invention of claim 3 selects the pulse signal for self-diagnosis received from the external device and the step signal for operation output, and takes only the step signal for operation output into the control device body. A control device having an input circuit, wherein a first detection means for detecting that a received signal from an external device is inverted relative to a normal state, and an interval period after the first detection means detects the inversion. A second detecting means for detecting whether or not the received signal remains inverted when the time has elapsed; and a control device that receives the detection result of the second detecting means and controls the received signal only when the received signal remains inverted Signal selection means to be incorporated into the main body, and the interval period is set so that the detection of the second detection means is performed in a time zone in which a pulse signal for self-diagnosis is not generated, corresponding to the specifications of the external device When Furnace has a feature.
[0010]
The invention according to claim 4 is characterized in that in the control device according to claim 3, there is provided a storage means for storing the interval period in an updatable manner and an input operation means for updating the interval period by an input operation. .
[0011]
According to a fifth aspect of the present invention, there is provided the control device according to the third aspect, wherein the storage unit stores the interval period in an updatable manner, and the interval period update unit updates the interval period by sampling the signal received by the receiving unit. It has the feature in having.
[0012]
[Action and effect of the invention]
According to the present invention, it is detected whether or not the received signal received by the input circuit of the control device remains inverted when a predetermined interval period has elapsed since the received signal was inverted. Only the received signal is taken into the control device body. Here, in the present invention, since the interval period is set in accordance with the specifications of the external device, when the received signal is a pulse signal for self-diagnosis, the inversion state is surely achieved when the interval period elapses. Has returned to its original state. On the other hand, when the received signal is a step signal for output during operation, the signal remains inverted even when the interval period elapses. Thereby, the pulse signal for self-diagnosis and the step signal for operation time output can be reliably selected, and stable sequence control based on the step signal for operation time output can be performed.
[0013]
Further, the interval period according to the present invention may be updated by an input operation using the input operation means (the invention of claim 4), or the interval period update means samples and updates the signal received by the receiving unit. (Invention of claim 5).
[0014]
DETAILED DESCRIPTION OF THE INVENTION
<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
The PLC 10 of this embodiment (corresponding to the “control device” of the present invention) has a basic configuration shown in FIG. 1, and is formed by connecting an input circuit 12, an output circuit 13, and a keyboard 14 to a main body 11. . The main body 11 includes a CPU 15 as a main part, and runs a sequence program recorded in the memory 16 based on a signal received from the input circuit 12. Then, a predetermined sequence process is performed to drive a device (not shown) connected to the output circuit 13.
[0015]
Further, the PLC 10 of the present embodiment is a so-called safety PLC, and the input circuit 12 is configured to be able to generate a pulse for PLC diagnosis described below. That is, the input circuit 12 is provided with a plurality of receiving circuits 25 according to the number of input points, and one of the receiving circuits 25 is representatively shown in FIG.
[0016]
The receiving circuit 25 includes first and second photocouplers 23 and 24, and the phototransistor 23A of the first photocoupler 23 and the LED 24B of the second photocoupler 24 are connected in series to connect the external connection circuit 29. It is composed. Specifically, the cathode of the LED 24B is connected to the GND, the anode is connected to the emitter of the phototransistor 23A, and the collector of the phototransistor 23A is opened to provide an external connection terminal 26 in the input circuit 12.
[0017]
Further, the LED 23B of the first photocoupler 23 is always driven by the input control circuit 20, whereby the phototransistor 23A is turned on, and the external connection circuit 29 becomes conductive from the external connection terminal 26 toward GND. It is in a state. When the energization state of the external connection circuit 29 changes according to the output signal of the external device connected to the external connection terminal 26, the phototransistor 24A of the second photocoupler 24 opens and closes as the energization state changes. As a result, a signal is taken into the input control circuit 20 to which the phototransistor 24A is connected.
[0018]
The input control circuit 20 turns off the LED 23B of the first photocoupler 23 periodically and over a predetermined period (for example, 20 μsec) when an ON signal is constantly output from an external device connected to the external connection terminal 26, As a result, the PLC diagnostic pulse as an OFF signal is generated in the receiving circuit 25. Then, the input circuit 12 is self-diagnosis based on whether the second photocoupler 24 can detect the pulse signal for PLC diagnosis.
[0019]
Since the PLC 10 of the present embodiment is a safety PLC as described above, a so-called safety device used for ensuring human safety is connected to the input circuit 12 as an external device of the present invention. As an example of the safety device, a case where a safety light curtain 30 (hereinafter simply referred to as “light curtain 30”) is connected will be described below.
[0020]
The light curtain 30 includes a light projecting unit 31 and a light receiving unit 32. When a plurality of parallel optical axes connecting the light projecting and receiving units 31 and 32 are blocked, a detection signal ("operation signal of the present invention" Is output).
[0021]
The output circuit of the light curtain 30 is, for example, an open collector circuit of a transistor (hereinafter referred to as “output transistor”). For example, a 24V power source is connected to the collector and the external connection terminal 26 of the PLC 10 is connected to the emitter. The Further, the output transistor is always turned on, so that the voltage of the signal input to the external connection terminal 26 when the light curtain 30 is not operating is kept at 24V. When the light curtain 30 is activated, the output transistor is turned off, and the voltage of the signal input to the external connection terminal 26 becomes 0V. That is, as shown in FIG. 2A, the signal output when the light curtain 30 is activated is a step signal for switching from the ON state of the potential 24V to the OFF state of the potential 0V.
[0022]
Incidentally, the light curtain 30 periodically outputs a pulse signal for self-diagnosis, and performs self-diagnosis by feeding back the pulse signal to the light curtain 30 itself. The pulse signal for self-diagnosis is generated by periodically turning off the output transistor of the light curtain 30 for a predetermined period (for example, about 25 μsec). That is, the signal output by the light curtain 30 during the self-diagnosis is an off-pulse signal having a pulse width of about 25 μsec as shown in FIG.
[0023]
The input control circuit 20 includes a CPU 21, a ROM 22, an EEPROM 27, and a RAM (not shown). The signal selection program stored in the ROM 22 is run, and the above-described pulse signal for self-diagnosis and the step signal for output during operation are provided. Can be sorted out. Specifically, for example, execution of the signal selection program PR1 shown in FIG. 3 is assigned as an interrupt process when the reception signal by the reception circuit 25 is inverted from the on state (normal state) to the off state.
[0024]
When the inversion of the received signal is detected and the signal selection program PR1 is executed, as shown in FIG. 3, after the counter K is reset to 0 (S1), a loop for incrementing the counter K by 1 is entered. (S2, S3) The increment is repeated until the counter K reaches a predetermined upper limit value K1.
Then, when the counter K reaches the upper limit value K1 (Yes in S3) and exits the loop, it is re-detected whether or not the received signal is in an off state, that is, whether or not it remains inverted (S4). If the received signal is inverted (off state) (Yes in S5), the received signal is converted into a signal having a level suitable for the main body 11 and output to the main body 11 (S6). . On the other hand, when the reception signal is turned back on (No in S5), the reception signal is ignored and no signal is output to the main body unit 11.
[0025]
In summary, the signal selection program PR1 detects that the reception signal of the reception circuit 25 is inverted from the on state to the off state, and when the predetermined time counted by the counter K has elapsed, It is re-detected whether or not it remains inverted (still off) (S4), and only when it remains inverted (Yes in S5), the received signal is taken into the main body 11 (S6).
[0026]
That is, in the present embodiment, the step (not shown) of detecting the inversion of the received signal before the execution of the above-described signal selection program PR1 corresponds to the “first detection means” according to the present invention, and the re-detection Step S4 of performing is equivalent to the “second detection means” according to the present invention. Further, the predetermined time according to the count of the counter K corresponds to the “interval period” according to the present invention, and the received signal is received according to whether the received signal remains inverted after receiving the result of redetection. The step (S5) for determining whether or not to capture the signal corresponds to the “signal selection means” according to the present invention.
[0027]
In the case of the present embodiment, the interval period according to the present invention is specified by the above-described upper limit value K1, and the data of the upper limit value K1 corresponds to the EEPROM 27 provided in the input control circuit 20 (the “storage means” of the present invention). To remember). Then, by operating a keyboard 14 (corresponding to “input operation means” of the present invention) connected to the main body 11, an update command is transmitted from the CPU 15 of the main body 11 to the CPU 21 of the input circuit 12 and stored in the EEPROM 27. The upper limit value K1 is updated.
[0028]
By the way, the CPU 21 of the input control circuit 20 periodically executes the PLC diagnosis program PR2 shown in FIG. When this program PR2 is executed, as shown in FIG. 4, the assignment of the interrupt process to the signal selection program PR1 is canceled (S10), and then a PLC diagnosis pulse is generated (S11). Then, it is checked whether or not the generated PLC diagnostic pulse has been received by the second photocoupler 24 (S12). If it has been received (Yes in S12), an interrupt process for the signal selection program PR1 is performed. After returning the allocation, the PLC diagnostic program PR2 is exited. On the other hand, when the second photocoupler 24 does not receive the PLC diagnostic pulse (No in S12), the program PR2 is exited after notifying that there is an abnormality. In addition, what is necessary is just to perform the replacement | exchange operation | work of the photocoupler 23 etc. when abnormality notification is performed.
[0029]
Next, the operation of the present embodiment configured as described above will be described.
When the external device connected to the input circuit 12 of the PLC 10 outputs a pulse signal for self-diagnosis, the generation interval and the pulse width of the pulse signal for self-diagnosis described in the specifications of the external device Set the interval period with reference to. Specifically, as shown in FIG. 5A, when a light curtain 30 that outputs a pulse signal for self-diagnosis having a period of 1 msec and a pulse width of 20 μsec is connected to the input circuit 12, an interval period is set. A value larger than 20 μsec and smaller than 1020 μsec (= 1 msec + 20 μsec) can be set.
[0030]
Here, when it is desired to increase the processing speed, it is preferable that the interval period is short. When the certainty of the processing is determined, the variation is taken into consideration and the pulse signal for self-diagnosis is generated. It is preferable to set so that the end point of the interval period comes in a distant time zone. Therefore, for example, a case where 40 μsec is set as the interval period will be described below.
[0031]
In the present embodiment, the interval period is set by operating the keyboard 14. When data “interval period = 40 μsec” is input using the keyboard 14, for example, the data is transferred to the CPU 21 of the input circuit 12 through the CPU 15 of the main body 11, and 40 μsec is converted into the upper limit value K1 by a predetermined formula. The Then, the value of the upper limit value K1 stored in the EEPROM 27 is updated to a value corresponding to 40 μsec of the interval period.
[0032]
As a result, the loop count for incrementing the counter K when the signal selection program PR1 is executed is set to the number that matches the specification of the pulse signal for self-diagnosis output from the light curtain 30. Then, when the reception signal of the input circuit 12 in the PLC 10 is inverted from the on state to the off state (time S in FIG. 5), when 40 μsec has elapsed from the start point (time E in FIG. 5), It is detected whether or not the received signal remains inverted (off state).
[0033]
Here, if the signal received by the input circuit 12 is a pulse signal for self-diagnosis, as shown in FIG. 5 (A), the signal must be turned on when the interval period elapses (time E in FIG. 5). It is restored to the state. On the other hand, when the signal received by the input circuit 12 is a step signal for output during operation, it is always turned off when the interval period elapses (time E in FIG. 5), as shown in FIG. Held in a state. Thereby, the pulse signal for self-diagnosis and the step signal for operation output can be reliably selected.
[0034]
Thus, according to the present embodiment, the signal received by the input circuit 12 is detected twice, and the interval period between the two detections is set in accordance with the specifications of the external device connected to the PLC 10. Thus, it is possible to reliably select the pulse signal for self-diagnosis or the step signal for operation output depending on whether the received signal is on or off at the time of the second detection. As a result, even if an external device that outputs a pulse signal for self-diagnosis is connected to the PLC 10, it is possible to perform stable sequence control based on the step signal for operation output without being affected by the pulse signal. .
[0035]
Also, when setting the interval period, the generation interval and pulse width of the pulse signal for self-diagnosis are also input, and control is performed so that the generation of the PLC diagnosis pulse and the pulse signal for self-diagnosis are not synchronized. Also good. Thereby, the self-diagnosis of PLC10 itself can be performed smoothly.
[0036]
Further, as shown in FIG. 5C, when a plurality of consecutive self-diagnostic pulses are generated and a pattern in which a plurality of consecutive pulses are generated again is repeated for a while, an interval period is repeated after a group of continuously generated pulses. It may be set so that the end point of.
[0037]
Second Embodiment
In the first embodiment, the interval period is set by operating the keyboard 14, but the PLC of the present embodiment samples the received signal of the input circuit only by connecting an external device to the input circuit. The interval period is automatically set. Hereinafter, description will be made with reference to the flowcharts of FIGS.
[0038]
In order to obtain the specifications of the pulse signal for self-diagnosis output from the external device, the maximum value of the pulse width of the self-diagnosis pulse and the minimum time of the pulse interval are obtained. For this purpose, in the processing shown in FIG. 6, the number of samplings is counted while sampling the input signal to the input circuit in the PLC at a constant period, and the count value of the number of samplings from when the input signal is switched to when it is switched to the next. Is an array variable t with a natural number n as an argument _(N) To remember.
[0039]
Specifically, when the processing of FIG. 6 is executed, first, the array counter n is initialized to 0 (S100), and the process waits until the input signal changes from the off state to the on state (S102). By this processing, sampling can be started immediately after the on state is entered, and the first input signal on time can be accurately measured.
[0040]
When the input signal changes from the off state to the on state, the standby processing (S102) is exited, the time measurement counter is cleared (S104), and the input signal is sampled (S106). Then, the time counting counter is counted up (S108), and it is checked whether the ON / OFF of the sampled input signal and the previous sampled input signal is inverted (S110). Yes in S110), the counter value at that time is t _(N) (S118), the array counter n is incremented (S120). If the array counter n is smaller than 100 (No in S122), the process returns to the above-described S104, and the same operation as described above is repeated until the array counter n is reached.
[0041]
On the other hand, when ON / OFF of the sampled input signal and the previous sampled input signal is not reversed (No in S110), a time waiting process (S112) is executed. This time waiting process is a process for performing sampling (S106) in the same cycle regardless of whether the input signal has changed or not. That is, this waiting time is a time obtained by subtracting the time required for the processing of S114 from the time required for the processing of each step of S118, S120, S122, and S104. In practice, processing such as repeating a NOP (No operation) command a predetermined number of times is performed.
[0042]
After the time waiting process (S112), it is determined whether or not the counter value exceeds a constant C1 (S114). This process is a process for preventing an infinite loop when the input signal is not switched for some reason. That is, when the input signal is not switched, the processing from S106 to S114 is repeated infinitely. If this is left unattended, the system stops and the user cannot know the cause of the stop. As a result, it takes a long time to investigate and recover the cause. In order to prevent this, the counter value is monitored (S114), and if it exceeds the predetermined number of times (C1) (Yes in S114), it is considered that an abnormality has occurred and the "abnormal end flag" is turned on (S116). Terminate the process. Thereby, the occurrence of the abnormality can be notified to the user together with the content thereof, and the user can perform an appropriate recovery work.
[0043]
By the processing of the flowchart of FIG. 6 described above, the array variable t _(N) A count value corresponding to the time interval when the input signal changes is stored in (array counter n = 0 to 99), and an abnormality is notified when the input signal does not change for a predetermined time due to some abnormality.
[0044]
When the process shown in FIG. 6 is completed, the process shown in FIG. 7 is performed. In this process, the maximum value and the second largest value of the ON time of the input signal, and the minimum value and the second smallest value are obtained. Hereinafter, the maximum value of the on time of the input signal is expressed as t. _{on_max1} , The next largest value after t _{on_max2} , The minimum value is t _{on_min1} , The next smallest value after t _{on_min2} It shall be expressed as
[0045]
First, the array counter n is set to 0 (S202), t _{on_min1} And t _{on_min2} Is temporarily set to a predetermined value (S204), and t _{on_max1} And t _{on_max2} Is set to 0 (S206).
[0046]
And t _(N) Is t _{on_min1} It is determined whether or not (S208) and t _(N) Is t _{on_min1} If it is the following (Yes in S208), t _{on_min2} To t _{on_min1} Is substituted (S210), t _{on_min1} To t _(N) Is substituted (S212).
[0047]
On the other hand, t _(N) Is t _{on_min1} If not, t _(N) Is t _{on_min2} It is determined whether it is less than (S214), where t _(N) Is t _{on_min2} If it is less than (Yes in S214), t _{on_min2} To t _(N) Is substituted (S216).
On the other hand, t _(N) Is t _{on_min2} If not (No in S214), t _{on_min2} The process proceeds to the next process without rewriting.
That is, t _(N) Is the current t _{on_min1} T is smaller than _{on_min1} To t _(N) Is substituted and t _{on_min1} ≦ t _(N) <T _{on_min2} Then t _{on_min2} To t _(N) Is substituted.
[0048]
Subsequent S218 to S226 are executed in the same manner as S208 to S216 described above. _{on_max1} And t _{on_max2} Therefore, detailed description is omitted.
[0049]
Next, 2 is added to the array counter n (S228). t _(N) Since the ON time and OFF time of the input signal are alternately stored, the ON time of the input signal can be extracted by adding the array counter n by two. If the array counter n is less than 100 (No in S230), the process returns to S208, and the same process is repeated until the array counter n reaches 100. Thus, by repeatedly performing the processing of S208 to S226 for the on time of each input signal, the maximum value and the second largest value, and the minimum value and the second smallest value of the input signal on time are obtained.
[0050]
The process shown in FIG. 8 executed after the process shown in FIG. 7 is a process for obtaining the maximum value and the second largest value and the minimum value and the second smallest value of the input signal off time. In this flowchart, the maximum value of the input signal off time is expressed as t. _{off_max1} , The next largest value of the maximum value of the input signal off time t _{off_max2} , The minimum value of the input signal off time t _{off_min1} , The next smallest value of the minimum value of the input signal off time t _{off_min2} It expresses.
[0051]
The process in FIG. 8 is the same as the process in FIG. 7 except that the “on time” and the “off time” are different, and the other processes are the same. Note that the array counter n is initialized to 1 in S302 because t _(N) This is because only the odd number, i.e., the off time of the input signal is extracted.
[0052]
9 checks each value obtained by the processing of FIGS. 7 and 8, that is, the maximum / minimum value of the on time / off time, the second largest value, and the second smallest value. 7 is a flowchart showing a process for determining whether or not there is any abnormality and obtaining the maximum value of the self-diagnosis pulse width and the minimum time interval between the self-diagnosis pulses when there is no abnormality.
[0053]
In the process of FIG. 9, first, t _p Is initialized to 0 (S402). t _p Is a variable into which the maximum value of the pulse width for self-diagnosis is substituted in a later process.
[0054]
Next, in S404 to S410, the maximum value of the on time / off time is compared with the second largest value, and the minimum value is compared with the second smallest value. Since the input signal repeatedly shows a predetermined data pattern, the values to be compared must be almost the same value. If a large difference appears as a result of the comparison, it is considered that there is a high probability that noise is mixed in the circuit or wiring or the operation is unstable. _p The process ends with 0 remaining unchanged. Note that C2 in S404 to S410 is a predetermined constant corresponding to an allowable value.
[0055]
If no abnormality is recognized in S404 to S410, the processing after S412 is performed. That is, by comparing the maximum value of the on time and the maximum value of the off time (S412), it is determined whether the self-diagnosis pulse of the external device is an off pulse or an on pulse. The maximum on-time (t _{on_max1} ) Is the maximum off time (t _{off_max1} ) (Yes in S412), it is determined that the self-diagnosis pulse is an off-pulse, and otherwise (No in S412), it is determined that the self-diagnosis pulse is an on-pulse.
[0056]
If it is determined that the self-diagnosis pulse is an off-pulse, the processing of S414 to S418 is performed. That is, the maximum value of the pulse width of the self-diagnosis pulse (t _{off_max1} ) And minimum value (t _{off_min1} ) Is within a predetermined range (constant C3 or less) (S414). Here, since the self-diagnosis pulse has a constant pulse width, the maximum value and the minimum value of the pulse width should be substantially equal. If this difference is large (No in S414), it is presumed that the external device is activated during sampling and the input signal is actually switched (not due to the self-diagnosis pulse). In such a case, the time interval for reading the input signal twice cannot be obtained with high accuracy. _p The process ends without setting a value to.
[0057]
Maximum value of pulse width of self-diagnosis pulse (t _{off_max1} ) And minimum value (t _{off_min1} ) Is within a predetermined range (constant C3 or less) (Yes in S414), t _{off_max1} Multiplied by a constant C4 and t _p (S416). t _{off_max1} The value stored in is not the twice reading time interval itself of the input signal itself, but is the counter value of the counter for the time coefficient used in the processing of FIG. _{off_max1} Is converted into a value representing time by the product of the value and the constant C4. As a result, t _p Is set to a time interval of twice reading of the input signal, for example, in units of μs. Similarly, t _{on_min1} Multiplied by a constant C4 and t _q (S418).
[0058]
S420 to S424 show processing when the self-diagnosis pulse is an on-pulse. Since these processes have the same contents as S414 to S428, detailed description is omitted.
[0059]
S426 is t _p A value obtained by adding a constant α to t and t _q This is a process of comparing the size of and. (T _p + Α) is the time interval when the input signal is actually read twice, and the constant α is for giving a margin to this time interval. That is, the maximum value (t _p If the input signal is read twice at a time interval of), the signal will be misread when the pulse width for self-diagnosis changes due to temperature changes, etc., so the time interval when reading the input signal twice is increased. It is. (T _p + Α) <t _q In this case, as will be described in detail later, it is necessary to know the number of consecutive occurrences (N) when the self-diagnosis pulses are continuously generated.
[0060]
FIG. 10 shows a process for obtaining the number of consecutive occurrences (N) when the self-diagnosis pulses are continuously generated. S502 to S506 are t _{on_max1} And t _{off_max1} Whichever is greater is multiplied by 0.9 and the variable t _r Is a process of substituting for. As a result, t _r Is substituted with a value obtained by multiplying the count of the longest pulse width by 0.9. The number of consecutive self-diagnosis pulses (N) is between the long pulse width (P1 in FIG. 11C) and the next long pulse width (P2 in FIG. 11C). Since it is the number of self-diagnosis pulses that have occurred, t _r T after the above pulse occurs _r The number of pulses generated until the above pulses are generated is counted.
[0061]
In S508 and S510, variables m and n are initialized, respectively. S512 is t _(N) Is t _r Determine if greater than. t _(N) Is t _r If it is not larger, n is incremented in S514 and the process returns to S512. T in S512 _(N) Is t _r If larger, m is incremented in S516. Next, n is incremented in S518, and t is incremented in S520. _(N) And t _r And t _(N) > T _r Otherwise, the processing from S516 to S520 is repeated.
By this repeated process, the number of pulses generated between the pulses P1 and P2 is counted. This count number includes both on-pulse and off-pulse.
[0062]
T at S520 _(N) > T _r If so, a value in which m is halved is substituted for the number N of consecutive self-diagnosis pulses generated in S522. As described above, since m is a count value including both the on-pulse and the off-pulse, the number N of continuous occurrences of self-diagnosis pulses can be obtained by halving this value. After this processing, return.
[0063]
Through the above processing, the maximum value of the pulse width for self-diagnosis (t _p ) And the minimum time interval (t _q ) And the number of consecutive self-diagnostic pulses (N). In addition, if there is an abnormality in the maximum / minimum values of on-time / off-time, t _p Since the process shown in FIG. 9 ends with 0 remaining, in this case, the user can be notified of the abnormality. In order to show the cause of the abnormality to the user in more detail, if it is determined that there is an abnormality in the processes of S404 to S410 and S414 and S420, a different abnormality code may be set for each.
[0064]
<Other embodiments>
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following are within the scope not departing from the gist. It can be changed and implemented.
(1) Although the light curtain 30 illustrated in the first embodiment outputs an off pulse as a self-diagnosis pulse, the present invention is applied to a PLC to which an external device that outputs an on-pulse as a self-diagnosis pulse is connected. May be applied.
[0065]
(2) Although the PLC 10 of the first embodiment is configured to generate a PLC diagnostic pulse, the present invention may be applied to a PLC that does not generate a PLC diagnostic pulse.
[0066]
(3) In the said embodiment, although PLC was illustrated as a control apparatus which concerns on this invention, the control apparatus which concerns on this invention is not limited to PLC, if an external apparatus is connected, for example, It may be a CNC (numerical control) controller, a robot controller, a personal computer or the like.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a PLC according to a first embodiment of the present invention.
FIG. 2A is a waveform diagram showing a step signal for output during operation.
(B) Waveform diagram showing pulse signal for self-diagnosis
(C) Waveform diagram showing a modified example of a self-diagnosis pulse signal
FIG. 3 is a flowchart of a signal selection program.
FIG. 4 is a flowchart of a PLC diagnostic program.
FIG. 5A is a time chart showing the relationship between the step signal for output during operation and the interval period;
(B) Time chart showing the relationship between the self-diagnosis pulse signal and the interval period
FIG. 6 is a flowchart of processing for setting an interval period according to the second embodiment.
FIG. 7 is a flowchart of processing for setting the interval period;
FIG. 8 is a flowchart of processing for setting the same interval period.
FIG. 9 is a flowchart of processing for setting the interval period.
FIG. 10 is a flowchart of processing for setting an interval period.
FIG. 11 is a waveform diagram of pulses for self-diagnosis.
[Explanation of symbols]
10 ... PLC (control device)
11 ... Main body (control device main body)
12 ... Input circuit
14 ... Keyboard (input operation means)
27 ... EEPROM (storage means)
30 ... Light curtain (external equipment)

Claims (5)

A signal input method for a control device that selects a pulse signal for self-diagnosis received from an external device and a step signal for output during operation, and takes only the step signal for output during operation into the control device body,
It is detected whether or not the received signal from the external device remains inverted when the interval period elapses after being inverted with respect to the normal state, and the control is performed only when the received signal remains inverted. Incorporate into the device body,
A signal input method for a control apparatus, wherein the interval period is set so as to perform the detection in a time zone in which the pulse signal for self-diagnosis is not generated in accordance with the specification of the external device. A control device input circuit that selects a pulse signal for self-diagnosis received from an external device and a step signal for output during operation, and takes only the step signal for output during operation into the control device body,
First detection means for detecting that a received signal from the external device is inverted with respect to a normal state;
Second detection means for detecting whether or not the received signal remains inverted when the interval period has elapsed since the first detection means detected the inversion;
Receiving the detection result of the second detection means, comprising a signal selection means for capturing the reception signal into the control device main body only when the reception signal remains inverted,
The control is characterized in that the interval period is set so that the detection by the second detection means is performed in a time zone in which the pulse signal for self-diagnosis is not generated, corresponding to the specification of the external device. The input circuit of the device. A control device comprising an input circuit that selects a pulse signal for self-diagnosis received from an external device and a step signal for operation output, and takes only the step signal for operation output into the control device body. ,
First detection means for detecting that a received signal from the external device is inverted with respect to a normal state;
Second detection means for detecting whether or not the received signal remains inverted when the interval period has elapsed since the first detection means detected the inversion;
Receiving the detection result of the second detection means, comprising a signal selection means for capturing the reception signal into the control device main body only when the reception signal remains inverted,
The control is characterized in that the interval period is set so that the detection by the second detection means is performed in a time zone in which the pulse signal for self-diagnosis is not generated, corresponding to the specification of the external device. apparatus. Storage means for storing the interval period in an updatable manner;
The control device according to claim 3, further comprising an input operation means for updating the interval period by an input operation. Storage means for storing the interval period in an updatable manner;
The control apparatus according to claim 3, further comprising: an interval period updating unit that samples the signal received by the receiving unit and updates the interval period.

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