JP2019057239A - Control device - Google Patents

Abstract

To prevent false diagnosis while maintaining good response to failure detection, regarding a fault diagnosis of an input circuit.SOLUTION: PLC1 includes: an input circuit 3 which receives signals from one of normally closed contacts C1 to C4 and outputs contact input signals Si1 to Si4; and a diagnostic signal output unit 5 and a diagnostic unit 6 outputting diagnostic signals Sd1 to Sd4 to the other terminals of the contacts C1 to C4. The diagnostic unit 6 includes: a pulse width measuring unit 7 for detecting pulses included in the contact input signals Si1 to Si4 and measuring a width of the detected pulse; a statistical data creation unit 8 that creates statistical data in which the number of times of detection of the pulse detected in the measurement period and the width of the measured pulse are associated with each other; and a pulse width setting unit 9 for setting a diagnostic pulse width of the diagnostic signals Sd1 to Sd4 based on the statistical data. The diagnostic unit 6 excludes a pulse having a width different from the diagnostic pulse width from the pulses included in the contact input signals Si1 to Si4, to thereby diagnose a failure of the input circuit 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device including an input circuit that outputs a contact input signal having a level corresponding to an open / close state of a normally closed contact to an internal circuit.

  As disclosed in Patent Document 1, a control device such as a programmable logic controller is provided with an input circuit for taking a signal supplied from an external device to be controlled into an internal circuit. Hereinafter, the programmable logic controller is also referred to as PLC.

  For example, in an input circuit used for detecting an operation state of a B contact which is a normally closed contact such as an emergency stop switch, when the B contact is operated and becomes an open state, a level corresponding to the open state, For example, an operation of outputting a low level signal to a microcontroller which is an internal circuit is performed.

  If the input circuit breaks down and such an operation is not performed, a situation may occur in which the operation of the target device is not stopped even though the emergency stop switch is operated. Therefore, a function for periodically diagnosing whether or not the input circuit can operate normally, that is, whether or not a failure has occurred in the input circuit is required.

  For these reasons, some conventional control devices have a function of diagnosing an input circuit failure. In this case, the control device includes a diagnostic signal output unit that outputs a diagnostic signal including a pulse that changes to a low level every predetermined diagnostic cycle. The control device feeds back a diagnostic signal to the input circuit via the B contact, and diagnoses the failure of the input circuit depending on whether or not the pulse is included in the output signal of the input circuit at each diagnostic cycle. ing.

JP 2013-73450 A

  In the above conventional configuration, when noise such as external noise is superimposed on the diagnostic signal transmission path, the output signal of the input circuit may be at a low level due to the influence. As a result, in reality, a low level signal is output due to the influence of noise even though the input circuit has failed and a failure that cannot output a low level signal has occurred. There is a risk of being.

  If the pulse intentionally included in the diagnostic signal can be clearly distinguished from the unintended pulse due to the influence of noise, it is considered that the occurrence of the above-described misdiagnosis can be prevented. However, since the noise generation state described above varies depending on the environment in which the PLC is installed, the presence and type of external devices connected to the PLC, and the like, it is difficult to uniformly determine the rules for the above-described distinction.

  Therefore, in order to prevent such erroneous diagnosis due to noise, a method is adopted in which the above-described diagnosis is performed over a plurality of diagnosis cycles, and the failure of the input circuit is diagnosed based on the results of the diagnosis executed a plurality of times. It is possible to do. However, with this technique, the time required from the occurrence of a failure in the input circuit to the detection of the failure increases, and another problem arises that the responsiveness of failure detection decreases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device capable of preventing the occurrence of misdiagnosis while maintaining good failure detection responsiveness for failure diagnosis of an input circuit. It is to provide.

  The control apparatus according to claim 1 includes an input circuit, a diagnostic signal output unit, and a diagnostic unit. The input circuit inputs a signal of one terminal of a normally closed contact provided outside and outputs a contact input signal having a level corresponding to the open / closed state of the contact to the internal circuit. The diagnostic signal output unit outputs, to the other terminal of the contact, a diagnostic signal including a pulse that changes to a level corresponding to the open state of the contact every predetermined diagnosis cycle. The diagnostic signal output from the diagnostic signal output unit is fed back to the input circuit via the contact. If no failure has occurred in the input circuit, a pulse similar to the pulse included in the diagnostic signal appears in the contact input signal output from the input circuit at each diagnostic cycle.

  Based on this point, the diagnosis unit diagnoses a failure of the input circuit based on the pulse included in the contact input signal. Basically, the diagnosis unit diagnoses that the input circuit is normal if the contact input signal includes a pulse similar to the pulse included in the diagnosis signal. It can be diagnosed that the circuit is faulty. The diagnosis unit further has the following functions to suppress the occurrence of misdiagnosis due to external noise.

  That is, the diagnosis unit includes a pulse width measurement unit, a statistical data creation unit, and a pulse width setting unit. The pulse width measurement unit detects a pulse included in the contact input signal and measures the width of the detected pulse. The statistical data creation unit creates statistical data that associates the number of detected pulses detected by the pulse width measurement unit in a predetermined measurement period with the measured pulse width. The pulse width setting unit sets a diagnostic pulse width that is a width of a pulse included in the diagnostic signal based on the statistical data.

  In this case, the statistical data includes both a pulse intentionally included for diagnosis and an unintended pulse due to an influence such as external noise. However, the number of pulses intentionally included for diagnosis is output during the measurement period and the width of the pulse is known. Therefore, it is easy to identify a pulse intentionally included for diagnosis from a pulse included in the contact input signal. Therefore, based on the statistical data, the pulse width setting unit may set, as the diagnostic pulse width, a pulse width that is considered not to overlap with an unintended pulse width due to the influence of external noise or the like, or is less likely to overlap. it can.

  According to the above configuration, the width of the pulse appearing in the contact input signal due to the influence of external noise or the like is different from the diagnostic pulse width with a high probability. Therefore, the diagnosis unit diagnoses a failure of the input circuit by excluding pulses having a width different from the diagnosis pulse width set by the pulse width setting unit from the pulses included in the contact input signal. In this way, even if the number of diagnoses is reduced, the occurrence of misdiagnosis due to the influence of external noise or the like can be kept low. Therefore, according to the above configuration, it is possible to obtain an excellent effect that it is possible to prevent the occurrence of a misdiagnosis while maintaining a good responsiveness of the failure detection for the failure diagnosis of the input circuit.

  The occurrence of noise such as external noise that may be superimposed on the diagnostic signal varies depending on the environment in which the control device is installed, the presence / absence of external devices connected to the control device, the type of these external devices, and the like. Therefore, in the control device according to the second aspect, the creation of the statistical data by the statistical data creation unit and the setting of the diagnostic pulse width by the pulse width setting unit are performed when the device is started. In this way, the diagnostic pulse width is set based on the statistical data created from the pulse detection count and pulse width measurement results in the actual installation environment. Diagnosis that is not easily affected can be realized.

  However, the noise generation state is not maintained as it is at the time of starting the apparatus, and may change depending on, for example, the operation state of the external device. Therefore, in the control device according to the second aspect, the creation of the statistical data and the setting of the diagnostic pulse width are performed at a predetermined update cycle after being performed at the time of starting the device. In this way, since the diagnostic pulse width is changed according to the noise generation status that changes according to the operation status of the external device, it is possible to realize a diagnosis that is less susceptible to external noise and the like. .

  According to a third aspect of the present invention, the pulse width setting unit sets the diagnostic pulse width based on the number of detected pulses in the statistical data. The number of detected pulses in the statistical data is considered to be proportional to the frequency of occurrence of an unintended pulse having the same width as that of the pulse, assuming that there is no change in the occurrence of external noise or the change is small. . Therefore, if the diagnostic pulse width is set as described above, a pulse width that does not overlap with an unintended pulse width due to the influence of external noise or the like, or a pulse width that does not frequently overlap can be set as the diagnostic pulse width. As a result, the occurrence of misdiagnosis due to the influence of external noise and the like can be further suppressed.

  As described above, the noise generation state changes according to the surrounding environment such as the operating state of the external device. For this reason, when the control device is used for an application in which the operating state of the external device changes at a relatively short cycle, there is a possibility that the cycle of change in the noise generation state may be shortened. If the statistical data is created and the diagnostic pulse width is set for each update cycle as in the control device according to claim 2, it is considered that such a change can be dealt with. When it becomes longer than the period of change of the occurrence situation, there is a possibility that the response becomes insufficient. It should be noted that if the update cycle is set sufficiently shorter than the expected change cycle of noise generation, the occurrence of such a problem is considered to be eliminated, but if the update cycle is shortened excessively, statistical data The number of times of creation increases, causing problems such as an increase in processing load related to the creation.

  Therefore, in the control device according to the fourth aspect, the diagnostic signal output unit outputs a diagnostic signal including one pulse having a diagnostic pulse width for each diagnostic period. The diagnostic unit includes a pulse width changing unit that changes the diagnostic pulse width of the diagnostic signal on condition that a plurality of pulses having a diagnostic pulse width are included in the contact input signal within the same diagnostic cycle. That is, in this case, when an unintended pulse having a pulse width similar to the initially set diagnostic pulse width is generated due to a change in the noise generation state, the diagnostic pulse width is changed.

  As described above, in the above configuration, the diagnostic pulse width is dynamically changed according to the change in the noise generation state. In this way, even when the surrounding environment changes from moment to moment, the diagnostic pulse width can be changed to a pulse width that is unlikely to cause erroneous diagnosis due to noise. . Therefore, according to the above configuration, even when the control device is used for an application in which the surrounding environment changes at a relatively short cycle, it is possible to suppress the occurrence of erroneous diagnosis due to the influence of external noise or the like.

  In the control device according to the fifth aspect, the pulse width changing unit changes the diagnostic pulse width based on the number of detected pulses in the statistical data. As described above, the frequency of detection of pulses in statistical data is the frequency of occurrence of unintended pulses having the same width as that of the pulses, assuming that there is no change in the occurrence of external noise or the change is small. It is thought that it is proportional to Therefore, if the diagnostic pulse width is changed as described above, a pulse width that does not overlap with an unintended pulse width due to the influence of external noise or the like, or a pulse width that rarely overlaps, can be set as the diagnostic pulse width. As a result, the occurrence of misdiagnosis due to the influence of external noise and the like can be further suppressed.

  The control device according to claim 6, wherein the statistical data creation unit divides the pulse widths measured by the pulse width measurement unit into a plurality of groups, and creates the statistical data in which the number of times of detection for each group is recorded. To do. Further, in this case, the statistical data creation unit can change the range of the pulse width for each group. As a feature of external noise, noise having a similar pulse width is swarmed. For this reason, there may be a group having a pulse width with a very low occurrence frequency between the groups having a pulse width with a high occurrence frequency. As described above, by changing the range of the pulse width for each group, there is a possibility that a group of such pulse widths with low occurrence frequency can be found. In this way, the diagnostic pulse width can be set to a pulse width that is less frequently generated as external noise.

  In the control device according to claim 7, the statistical data generation unit divides the pulse widths measured by the pulse width measurement unit into a plurality of groups, and generates the statistical data obtained by recording the number of times of detection for each group. To do. Further, in this case, the statistical data creation unit sets the group so that the number of detection times of at least one of the groups is zero. As described above, as a feature of external noise, there is a possibility that a group having a pulse width with a very low occurrence frequency exists between groups having a pulse width with a high occurrence frequency. According to the above configuration, a group having such a pulse width that is extremely low in frequency is set as one of the above groups, and as a result, a pulse width that is less frequently generated as external noise as a diagnostic pulse width. Can be set to

The figure which shows typically the structure of PLC which concerns on 1st Embodiment, and a contact point The figure which shows a specific example of the statistical data which concerns on 1st Embodiment. The figure which shows a specific example of the candidate data which concerns on 1st Embodiment The figure which shows typically the content of the process by the diagnostic part which concerns on 1st Embodiment. Timing chart for explaining fault detection of input circuit when diagnostic pulse width is not updated Timing chart for explaining update of diagnostic pulse width according to the first embodiment Timing chart for explaining failure detection of an input circuit according to the first embodiment The figure which shows typically the structure of PLC and contact concerning 2nd Embodiment The figure which shows a specific example of the candidate data which concerns on 2nd Embodiment The figure which shows typically the content of the process by the diagnostic part which concerns on 2nd Embodiment.

Hereinafter, a plurality of embodiments will be described with reference to the drawings. In each embodiment, substantially the same components are denoted by the same reference numerals and description thereof is omitted.
(First embodiment)
The first embodiment will be described below with reference to FIGS.

  As shown in FIG. 1, N (where N is a positive integer) contacts provided in the external device 2 are connected to the PLC 1 corresponding to the control device. 1 illustrates the case where four contacts C1 to C4 are connected to the PLC 1, the number of contacts connected to the PLC 1 may be three or less, or may be five or more. FIG. 1 shows only the configuration related to the I / O unit responsible for input / output of signals with the external device 2 among the configurations of the PLC 1.

  The contacts C1 to C4 are normally closed contacts provided on the external device 2 connected to the PLC 1, that is, B contacts. Therefore, the contacts C1 to C4 are in a closed state (Close) when not operated, and are opened (Open) when operated by the user. In this case, the contacts C1 to C4 are used as an emergency stop switch for forcibly stopping the operation of the target device, for example.

  The PLC 1 includes terminals P1 to P4 connected to one of the contacts C1 to C4 and P5 to P8 connected to the other terminals of the contacts C1 to C4. The terminals P1 to P4 are terminals for inputting signals from one of the contacts C1 to C4. Terminals P5 to P8 are terminals for outputting diagnostic signals Sd1 to Sd4 to the other terminals of the contacts C1 to C4. Although details will be described later, the diagnostic signals Sd1 to Sd4 are signals that are at a high level such as +24 V for most of the period.

  The PLC 1 includes an input circuit 3 and a microcontroller 4. Hereinafter, the microcontroller 4 is referred to as a microcomputer 4. The input circuit 3 inputs signals from one of the contacts C1 to C4 and outputs contact input signals Si1 to Si4 having levels corresponding to the open / closed states of the contacts C1 to C4 to the microcomputer 4 that is an internal circuit.

  In this case, the input circuit 3 performs insulation and level conversion in the signal input / output path. For this reason, the contact input signals Si1 to Si4 output from the input circuit 3 are at the same level as the diagnostic signals Sd1 to Sd4, that is, almost at the high level during the period when the contacts C1 to C4 are closed, and the contacts C1 to C4 are For example, the low level such as 0V is applied during the open state. However, when the input circuit 3 performs the above level conversion, the high level of the contact input signals Si1 to Si4 becomes the high input voltage (for example, + 5V) of the microcomputer 4.

  Therefore, in this embodiment, the level corresponding to the closed state of the contacts C1 to C4 is the High level, and the level corresponding to the open state is the Low level. In the following, the high level is referred to as the H level, and the low level is referred to as the L level.

  The microcomputer 4 has a function of detecting the operation state of the contacts C1 to C4 based on the levels of the contact input signals Si1 to Si4. Specifically, when the period during which any one of the contact input signals Si1 to Si4 is at the L level continues for a certain time or more, the microcomputer 4 indicates that the corresponding contact among the contacts C1 to C4 has been operated by the user. Is detected. When the microcomputer 4 detects that any one of the contacts C1 to C4 has been operated by this function, the microcomputer 4 executes a process for forcibly stopping the operation of the target device corresponding thereto.

  In such a configuration, when a failure occurs in the input circuit 3 in which the circuit for setting the signal to a low level does not function, the contact input signals Si1 to Si4 are used even though any of the contacts C1 to C4 is operated by the user. Among these, the corresponding signal does not become L level. In such a case, there is a possibility that the operation of the target device may not be stopped even though the emergency stop switch is operated.

  Therefore, the microcomputer 4 has a function of periodically diagnosing whether or not a failure has occurred in the input circuit 3. Specifically, the microcomputer 4 includes a diagnostic signal output unit 5 and a diagnostic unit 6. The diagnostic signal output unit 5 outputs diagnostic signals Sd1 to Sd4 to the other terminals of the contacts C1 to C4 via the terminals P5 to P8. As described above, the diagnostic signals Sd1 to Sd4 are at the H level for most of the period, but change to the L level for a predetermined period every predetermined diagnostic cycle. That is, the diagnostic signals Sd1 to Sd4 include one pulse that changes from the H level to the L level for each diagnostic period.

  The diagnostic unit 6 sets the predetermined period during which the diagnostic signals Sd1 to Sd4 are at the L level, that is, the width of the pulse included in the diagnostic signals Sd1 to Sd4. Hereinafter, this pulse width is referred to as a diagnostic pulse width. Note that the above-described diagnostic pulse width and diagnostic cycle do not affect the function of detecting the operation state of the contacts C1 to C4, so that the time is sufficiently shorter than the operation time of the contacts C1 to C4 by the user. Is set.

  According to the above configuration, the diagnosis signals Sd1 to Sd4 are fed back to the input circuit 3 through the contacts C1 to C4 at the normal time, that is, when the contacts C1 to C4 are not operated. Here, if no failure has occurred in the input circuit 3 and it is normal, the contact input signals Si1 to Si4 appear with pulses having the same width as the pulses included in the diagnostic signals Sd1 to Sd4 for each diagnostic cycle. become.

  Based on such points, the diagnosis unit 6 diagnoses a failure of the input circuit 3 based on the pulses included in the contact input signals Si1 to Si4. Basically, the diagnosis unit 6 diagnoses that the input circuit 3 is normal if the contact input signals Si1 to Si4 include pulses having the same width as the pulses included in the diagnosis signals Sd1 to Sd4. If the pulse is not included, it can be diagnosed that the input circuit 3 has failed. The diagnosis unit 6 further has the following functions to suppress the occurrence of misdiagnosis due to external noise.

  That is, the diagnosis unit 6 includes a pulse width measurement unit 7, a statistical data creation unit 8, and a pulse width setting unit 9. The pulse width measuring unit 7 detects a pulse included in the contact input signals Si1 to Si4 and measures the width of the detected pulse. The pulse width can be measured using, for example, a counter that operates by detecting an edge of a signal. In this case, the counter starts counting when a falling edge is detected, and stops counting when a rising edge is detected. The pulse width can be obtained from the count value of the counter operating in this way.

  In this case, the pulse width measuring unit 7 generates pulses generated at the same timing as the pulses included in the diagnostic signals Sd1 to Sd4 from the detection and measurement targets described above, that is, pulses intentionally included for diagnosis. Is supposed to be excluded. Therefore, the pulse width measuring unit 7 detects an unintended pulse due to the influence of external noise or the like among pulses included in the contact input signals Si1 to Si4, and measures the width of the detected pulse.

  In the above configuration, the pulse width measurement unit 7 can easily identify the pulse intentionally included. This is because the pulse width measuring unit 7 is provided in the same microcomputer 4 as the diagnostic signal output unit 5 that outputs the diagnostic signals Sd1 to Sd4. Therefore, it is possible to transmit the timing at which the pulses included in the diagnostic signals Sd1 to Sd4 are generated from the diagnostic signal output unit 5 to the pulse width measurement unit 7. In this way, the pulse width measurement unit 7 determines that the pulse generated at the timing transmitted from the diagnostic signal output unit 5 is a pulse intentionally included for diagnosis, and detects and measures the target. Can be excluded. Therefore, in this case, an unintended pulse due to the influence of external noise or the like can be detected, and the width of the detected pulse can be measured.

  In the present embodiment, the pulse width measurement unit 7 is realized by a CPU included in the microcomputer 4 executing a program stored in a ROM or the like, that is, realized by software. The pulse width measurement unit 7 can also be realized by a dedicated circuit, that is, dedicated hardware.

  The statistical data creating unit 8 creates statistical data in which the number of detected pulses detected by the pulse width measuring unit 7 in a predetermined measurement period is associated with the measured pulse width. In the present embodiment, the measurement period is set to 1 hour, for example. Specifically, as shown in FIG. 2, the statistical data groups the measured pulse widths, and records the number of detections per measurement period for each group, that is, the occurrence frequency [times / 1 hour]. .

  In this case, the measured pulse width is divided into 10 groups G1 to G10. The group G1 is a group whose pulse width is in the range of 500 μs or more and less than 550 μs, and the occurrence frequency is “101”. The group G2 is a group whose pulse width is in the range of 550 μs or more and less than 600 μs, and the frequency of occurrence is “1059”.

  The group G3 is a group whose pulse width is in the range of 600 μs or more and less than 650 μs, and the frequency of occurrence is “32”. The group G4 is a group whose pulse width is in the range of 650 μs or more and less than 700 μs, and the occurrence frequency thereof is “2045”. The group G5 is a group whose pulse width is in the range of 700 μs or more and less than 750 μs, and its occurrence frequency is “14”. Group G6 is a group whose pulse width is in the range of 750 μs or more and less than 800 μs, and the frequency of occurrence thereof is “4981”.

  The group G7 is a group whose pulse width is in the range of 800 μs or more and less than 850 μs, and the frequency of occurrence is “302”. The group G8 is a group whose pulse width is in the range of 850 μs or more and less than 900 μs, and the occurrence frequency thereof is “2040”. The group G9 is a group whose pulse width is in the range of 900 μs or more and less than 950 μs, and the frequency of occurrence is “10394”. The group G10 is a group whose pulse width is in the range of 950 μs or more and less than 1000 μs, and the frequency of occurrence thereof is “0”.

  The statistical data described above is created for each of the contact input signals Si1 to Si4. The pulse width setting unit 9 sets diagnostic pulse widths, which are the widths of pulses included in the corresponding diagnostic signals Sd1 to Sd4, based on the statistical data created by the statistical data creation unit 8. Specifically, the pulse width setting unit 9 sets the diagnostic pulse width based on the number of detected pulses in the statistical data as follows.

  That is, the pulse width setting unit 9 selects the diagnostic pulse width candidates to be set in order from the least frequently generated group G1 to G10 of the measured pulse widths. Candidate data representing such candidates is, for example, as shown in FIG. In this case, the first candidate is a value within the range of the pulse width of the group G10 with the lowest occurrence frequency. In this case, in consideration of an error due to clock drift or the like, the center value of the pulse width range of the corresponding group is set as a diagnostic pulse width candidate. Therefore, the first candidate is “975 μs” which is the center value of the pulse width range of the group G10.

  The second candidate is a value within the range of the pulse width of the group G5 having the second lowest occurrence frequency, specifically, “725 μs”, which is the center value of the range of the pulse width of the group G5. The third candidate is a value within the range of the pulse width of the group G3 with the third lowest occurrence frequency, specifically, “625 μs” that is the center value of the range of the pulse width of the group G3.

  When there are a plurality of groups having the same occurrence frequency in the statistical data created by the statistical data creation unit 8, the pulse width setting unit 9 preferentially selects a group having a short pulse width as a candidate for the diagnostic pulse width. It has become. In this way, when the pulse width measurement unit 7 is configured to use the counter described above, the time for measuring the pulse width can be kept short.

  According to the above configuration, the width of the pulse appearing in the contact input signals Si1 to Si4 due to the influence of external noise or the like is different from the diagnostic pulse width with a very high probability. Therefore, the diagnosis unit 6 excludes pulses having a width different from the diagnosis pulse width set by the pulse width setting unit 9 from pulses included in the contact input signals Si1 to Si4, and diagnoses a failure of the input circuit 3. It is supposed to be.

Next, the operation of this embodiment will be described.
When the PLC 1 is installed at a site where the PLC 1 is actually used and started up in a state where an external device to be connected is connected, the diagnosis unit 6 (pulse width measurement unit 7, statistical data creation unit 8 and The processing shown in FIG. 4 is executed by the pulse width setting unit 9).

  First, in step S100, an unintended pulse included in the contact input signals Si1 to Si4 is detected, and the width of the detected pulse is measured. Subsequently, in step S200, the number of detected pulses is correlated with the measured pulse width, and statistical data is created based on the correlation. Thereafter, in step S300, it is determined whether the creation of statistical data has been completed.

  If the creation of statistical data has not been completed, “NO” is determined in the step S300, the process returns to the step S100, and the detection of the unintended pulse and the measurement of the width of the detected pulse are performed again. On the other hand, if the creation of statistical data has been completed, “YES” is determined in the step S300, and the process proceeds to the step S400. In step S400, the diagnostic pulse width is set or updated based on the statistical data. In the present embodiment, the diagnostic pulse width is set to a predetermined initial value until the first time step S400 is executed.

  After execution of step S400, the process proceeds to step S500, where it is determined whether or not the update timing has come. The update timing is set at a time when a predetermined update cycle has elapsed from the time when the previous statistical data was created. In the present embodiment, the update cycle is set to 1 hour, for example. When the update timing comes, “YES” is determined in the step S500, and the process returns to the step S100. As described above, in the present embodiment, the creation of statistical data and the setting of the diagnostic pulse width are performed at the update cycle after the PLC 1 is started.

As described above, according to the present embodiment, the following effects can be obtained.
The PLC 1 of the present embodiment includes a diagnosis unit 6 that diagnoses a failure of the input circuit 3, and the diagnosis unit 6 has the following functions to suppress the occurrence of misdiagnosis due to external noise. Yes. That is, the diagnostic unit 6 detects a pulse due to the influence of external noise included in the contact input signals Si1 to Si4 and measures the width of the detected pulse, and the pulse detected in the measurement period. A statistical data creation unit 8 that creates statistical data that associates the number of detections with the measured pulse width, and a pulse that sets a diagnostic pulse width that is the width of a pulse included in the diagnostic signals Sd1 to Sd4 based on the statistical data A width setting unit 9.

  In this case, the statistical data is data in which the width of an unintended pulse due to the influence of external noise and the frequency of occurrence of pulses of that width are stored. Therefore, based on the statistical data, the pulse width setting unit 9 sets, as the diagnostic pulse width, a pulse width that is considered not to overlap with an unintended pulse width due to the influence of external noise or is less likely to overlap. Can do.

  According to the above configuration, the width of the pulse appearing in the contact input signals Si1 to Si4 due to the influence of external noise or the like is different from the diagnostic pulse width with high probability. Therefore, the diagnosis unit 6 diagnoses a failure of the input circuit 3 by excluding pulses having a width different from the diagnosis pulse width set by the pulse width setting unit 9 from the pulses included in the contact input signals Si1 to Si4. . In this way, even if the number of diagnoses is reduced, the occurrence of misdiagnosis due to the influence of external noise or the like can be kept low. Therefore, according to the present embodiment, it is possible to obtain an excellent effect that the fault diagnosis of the input circuit 3 can be prevented from occurring while the response of the fault detection is well maintained.

  The occurrence of noise such as external noise that may be superimposed on the diagnostic signals Sd1 to Sd4 varies depending on the environment in which the PLC 1 is installed, the presence / absence of an external device connected to the PLC 1, the type of these external devices, and the like. Therefore, in the PLC 1 of the present embodiment, the creation of statistical data by the statistical data creation unit 8 and the setting of the diagnostic pulse width by the pulse width setting unit 9 are performed at startup after the PLC 1 is installed. In this way, the diagnostic pulse width is set based on the statistical data created from the pulse detection count and pulse width measurement results in the actual installation environment. Diagnosis that is not easily affected can be realized.

  However, the noise generation state is not maintained as it is when the PLC 1 is started, and may change depending on, for example, the operation state of the external device. Therefore, when the diagnostic pulse width is set to a fixed value, the following problem occurs. For example, the pulse width W1 that is initially set to the diagnostic pulse width of the diagnostic signal Sd1 as a pulse width that hardly overlaps with the width of an unintended pulse due to the influence of noise is changed according to the subsequent change in the noise generation state. It is easy to overlap with an unintended pulse width due to the influence of.

  Then, as shown in FIG. 5, even when a failure occurs in the input circuit 3 at the time t1 and the contact input signal Si1 cannot be set to the L level, the pulse is affected by the external noise in the subsequent diagnosis cycle. There is a high possibility that a pulse with a width W1 will appear, and as a result, the time until the input circuit 3 is diagnosed as having a failure is increased.

  Therefore, in the PLC 1 of the present embodiment, the creation of statistical data and the setting of the diagnostic pulse width are performed at a predetermined update cycle after being performed when the PLC 1 is started. In this way, the diagnostic pulse width is updated to the optimum pulse width in accordance with the noise generation status at that time for each update period. For example, as shown in FIG. 6, even if the pulse width W1 set at the time of start-up becomes more likely to overlap with the width of an unintended pulse due to the influence of noise, At the update timing ta, the pulse width is changed to a pulse width W10 that is difficult to overlap.

  As a result, as shown in FIG. 7, when a failure occurs in the input circuit 3 at the time t1 and the contact input signal Si1 cannot be set to the L level, the influence of external noise in the next diagnostic cycle. Even if a pulse with a pulse width W1 appears, a pulse with a diagnostic pulse width W10 does not appear, so that it is possible to immediately diagnose that the input circuit 3 has failed. That is, in this case, the time required for the failure diagnosis of the input circuit 3 can be shortened as compared with the case where the diagnosis pulse width is not updated.

  In this way, if the creation of statistical data and the setting of the diagnostic pulse width are performed every predetermined update cycle, according to the occurrence status of noise such as external noise that changes according to the operating status of the external device, Since the diagnostic pulse width is updated to an optimum value, it is possible to realize a diagnosis that is less affected by external noise and the like.

  The pulse width setting unit 9 sets a diagnostic pulse width based on the number of detected pulses in the statistical data. The number of detected pulses in the statistical data is considered to be proportional to the frequency of occurrence of an unintended pulse having the same width as that of the pulse, assuming that there is no change in the occurrence of external noise or the change is small. . Therefore, if the diagnostic pulse width is set as described above, a pulse width that does not overlap with an unintended pulse width due to the influence of external noise or the like, or a pulse width that does not frequently overlap can be set as the diagnostic pulse width. As a result, the occurrence of misdiagnosis due to the influence of external noise and the like can be further suppressed.

(Second Embodiment)
The second embodiment will be described below with reference to FIGS.
As shown in FIG. 8, the microcomputer 22 included in the PLC 21 of the present embodiment is different from the microcomputer 4 of the first embodiment in that a diagnosis unit 23 is provided instead of the diagnosis unit 6. In addition to the components included in the diagnosis unit 6, the diagnosis unit 23 includes a pulse width changing unit 24 that changes the diagnosis pulse width when a pulse caused by noise having the same pulse width as the set diagnosis pulse width is detected. ing.

  In this case, the diagnostic signal output unit 5 is configured to output diagnostic signals Sd1 to Sd4 including one pulse having a diagnostic pulse width for each diagnostic period. Therefore, when a plurality of pulses having a diagnostic pulse width are included in the contact input signals Si1 to Si4 within the diagnostic cycle, pulses caused by noise having the same pulse width as the set diagnostic pulse width are superimposed. Conceivable. Therefore, the pulse width changing unit 24 changes the diagnostic pulse width of the diagnostic signals Sd1 to Sd4 on condition that the contact input signals Si1 to Si4 within the same diagnostic cycle include a plurality of pulses having the diagnostic pulse width. It is like that.

  The pulse width changing unit 24 changes the diagnostic pulse widths of the corresponding diagnostic signals Sd1 to Sd4 based on the statistical data created by the statistical data creating unit 8, respectively. Specifically, the pulse width changing unit 24 changes the diagnostic pulse width based on the number of detected pulses in the statistical data as follows.

  That is, for example, the pulse width changing unit 24 selects candidates of diagnostic pulse widths to be changed in order from the least frequently occurring among the pulse width groups G1 to G10 in the statistical data shown in FIG. However, the pulse width changing unit 24 excludes the group corresponding to the currently set diagnostic pulse width from this candidate. The candidate data in this case is, for example, as shown in FIG.

  In this case, the first candidate is “725 μs”, which is the center value of the range of the pulse width of the group G5 having the second lowest occurrence frequency. The second candidate is “625 μs”, which is the center value of the pulse width range of the group G3, which is the third least frequently generated. The third candidate is “525 μs”, which is the center value of the pulse width range of the group G1 having the fourth lowest occurrence frequency.

Next, the operation of this embodiment will be described.
As shown in FIG. 10, steps S600 and S700 are added to the process executed by the diagnosis unit 23 of the present embodiment, compared to the process executed by the diagnosis unit 6 of the first embodiment. Step S600 is executed when the update timing has not yet arrived after the diagnostic pulse width is set (updated), that is, when “NO” in step S500.

  In step S600, whether or not the diagnostic pulse width needs to be changed is determined based on whether or not the contact input signals Si1 to Si4 within the same diagnostic cycle include a plurality of pulses having the diagnostic pulse width. If the contact input signals Si1 to Si4 within the same diagnostic cycle include a plurality of pulses having a diagnostic pulse width, it is necessary to change the diagnostic pulse width. Therefore, “YES” is determined in the step S600, and the process returns to the step S700. move on.

  In step S700, the diagnostic pulse width is changed based on the statistical data. And after execution of step S700, it returns to step S500. On the other hand, if the contact input signals Si1 to Si4 within the same diagnostic cycle do not include a plurality of pulses having a diagnostic pulse width, it is not necessary to change the diagnostic pulse width. Return to S500.

  As described above, the noise generation state changes according to the surrounding environment such as the operating state of the external device. Therefore, when the PLC 21 is used for an application in which the operating state of the external device changes at a relatively short cycle, there is a possibility that the cycle of change in the noise generation state may be shortened. If statistical data is created and the diagnostic pulse width is set for each update cycle, it is considered that such changes can be accommodated, but when the update cycle is longer than the cycle of the change in the noise generation status. May become inadequate. It should be noted that if the update cycle is set sufficiently shorter than the expected change cycle of noise generation, the occurrence of such a problem is considered to be eliminated, but if the update cycle is shortened excessively, statistical data The number of times of creation increases, causing problems such as an increase in processing load on the microcomputer 22 related to the creation.

  Therefore, in the PLC 21 of the present embodiment, the diagnosis unit 23 diagnoses the diagnosis signals Sd1 to Sd4 on condition that the contact input signals Si1 to Si4 within the same diagnosis cycle include a plurality of pulses having a diagnosis pulse width. A pulse width changing unit 24 for changing the pulse width is provided. In other words, in the present embodiment, when an unintended pulse having a pulse width similar to the initially set diagnostic pulse width is generated due to a change in the noise generation state, the diagnostic pulse width is changed. Yes.

  As described above, in the above configuration, the diagnostic pulse width is dynamically changed according to the change in the noise generation state. In this way, even when the surrounding environment changes from moment to moment, the diagnostic pulse width can be changed to a pulse width that is unlikely to cause erroneous diagnosis due to noise. . Therefore, according to the said structure, generation | occurrence | production of the misdiagnosis by the influence of an external noise etc. can be suppressed even when PLC21 is used for the use whose surrounding environment changes with a comparatively short period. That is, according to this embodiment, the effect that the noise tolerance with respect to an environmental change improves is acquired.

  The pulse width changing unit 24 changes the diagnostic pulse width based on the number of detected pulses in the statistical data. As described above, the frequency of detection of pulses in statistical data is the frequency of occurrence of unintended pulses having the same width as that of the pulses, assuming that there is no change in the occurrence of external noise or the change is small. It is thought that it is proportional to Therefore, if the diagnostic pulse width is changed as described above, a pulse width that does not overlap with an unintended pulse width due to the influence of external noise or the like, or a pulse width that rarely overlaps, can be set as the diagnostic pulse width. As a result, the occurrence of misdiagnosis due to the influence of external noise and the like can be further suppressed.

(Other embodiments)
In addition, this invention is not limited to each embodiment described above and described in drawing, In the range which does not deviate from the summary, it can change, combine or expand arbitrarily.
The numerical values and the like shown in the above embodiments are examples and are not limited thereto.

The timing of creating the statistical data and setting the diagnostic pulse width is not limited to the timing shown in the above embodiments, and may be executed at an arbitrary timing.
In each of the above embodiments, the configuration in which the function as the statistical data creation unit 8 is realized by the microcomputers 4 and 22 provided in the PLCs 1 and 21 is illustrated, but the configuration is not limited thereto. For example, the function as the statistical data creation unit 8 may be realized by an external device that can communicate with the PLCs 1 and 21.

  The pulse width measurement unit 7 may detect all the pulses included in the contact input signals Si1 to Si4 and measure the width of the detected pulse. In this case, the statistical data includes both a pulse intentionally included for diagnosis and an unintended pulse due to an influence such as external noise. However, the number of pulses intentionally included for diagnosis is output during the measurement period and the width of the pulse is known. Therefore, it is easy to identify a pulse intentionally included for diagnosis from pulses included in the contact input signals Si1 to Si4. Therefore, in this case, data relating to pulses intentionally included for diagnosis may be excluded from the generated statistical data. Alternatively, statistical data may be created by excluding data related to pulses intentionally included for diagnosis.

  The statistical data creation unit 8 may change the pulse width range for each group. As a feature of external noise, noise having a similar pulse width is swarmed. For this reason, there may be a group having a pulse width with a very low occurrence frequency between the groups having a pulse width with a high occurrence frequency. As described above, by changing the range of the pulse width for each group, there is a possibility that a group of such pulse widths with low occurrence frequency can be found. In this way, the diagnostic pulse width can be set to a pulse width that is less frequently generated as external noise.

  The above-described pulse width range for each group may be shifted, for example, by a predetermined value from the pulse width range for each group. For example, in each of the above embodiments, the group G1 was in the range of 500 μs to 550 μs, but this is shifted by “+25 μs” and changed to the range of 525 μs to 575 μs.

  Further, the statistical data creation unit 8 may set the group so that at least one detection number of the group becomes zero. As described above, as a feature of external noise, there is a possibility that a group having a pulse width with a very low occurrence frequency exists between groups having a pulse width with a high occurrence frequency. According to the above configuration, a group having such a pulse width that is extremely low in frequency is set as one of the above groups, and as a result, a pulse width that is less frequently generated as external noise as a diagnostic pulse width. Can be set to

  DESCRIPTION OF SYMBOLS 1,21 ... PLC, 3 ... Input circuit, 5 ... Diagnostic signal output part, 6, 23 ... Diagnostic part, 7 ... Pulse width measurement part, 8 ... Statistic data creation part, 9 ... Pulse width setting part, 24 ... Pulse width Change part, C1-C4 ... contact.

Claims (7)

An input circuit that inputs a signal of one terminal of a normally closed contact provided outside and outputs a contact input signal having a level corresponding to the open / closed state of the contact to an internal circuit;
A diagnostic signal output unit that outputs a diagnostic signal including a pulse that changes to a level corresponding to an open state of the contact with respect to the other terminal of the contact at every predetermined diagnosis cycle;
A diagnostic unit for diagnosing a failure of the input circuit based on the pulse included in the contact input signal;
With
The diagnostic unit
A pulse width measuring unit for detecting the pulse included in the contact input signal and measuring a width of the detected pulse;
A statistical data creating unit that creates statistical data that associates the number of detected pulses detected by the pulse width measuring unit with a measured pulse width in a predetermined measurement period;
A pulse width setting unit that sets a diagnostic pulse width that is a width of the pulse included in the diagnostic signal based on the statistical data;
With
A control device for diagnosing a failure of the input circuit by excluding the pulse having a width different from the diagnostic pulse width from the pulses included in the contact input signal.   The creation of the statistical data by the statistical data creation unit and the setting of the diagnostic pulse width by the pulse width setting unit are performed when the apparatus is started up, and thereafter, performed every predetermined update cycle. Control device.   The control device according to claim 1, wherein the pulse width setting unit sets the diagnostic pulse width based on the number of detections of the pulse in the statistical data. The diagnostic signal output unit outputs the diagnostic signal including one pulse having the diagnostic pulse width for each diagnostic cycle,
The diagnostic unit
A pulse width changing unit that changes the diagnostic pulse width of the diagnostic signal on condition that the contact input signal within the same diagnostic cycle includes a plurality of pulses having the diagnostic pulse width. Item 4. The control device according to any one of Items 1 to 3.   The control device according to claim 4, wherein the pulse width changing unit changes the diagnostic pulse width based on the number of detection times of the pulse in the statistical data. The statistical data creation unit
The pulse width measured by the pulse width measurement unit is divided into a plurality of groups, and the number of detection times for each group is recorded as the statistical data.
The control device according to claim 1, wherein a range of a pulse width for each group can be changed. The statistical data creation unit
The pulse width measured by the pulse width measurement unit is divided into a plurality of groups, and the number of detection times for each group is recorded as the statistical data.
The control device according to any one of claims 1 to 5, wherein the group is set so that the number of detection times of at least one of the group is zero.

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