JPS6388608A - Input unit for sequence controller - Google Patents

Abstract

PURPOSE:To always supply a correct input signal to a CPU unit without being accompanied by a system-down even at the time of the abnormality of an input circuit by providing at least >=3 input circuits and selecting and outputting the data outputted from respective input circuits to an interface based on the principle of a majority determination. CONSTITUTION:Outputs A-C of respective input circuits 8A-8C are inputted through a switch circuit 11 to a majority circuit 12, selected based on the principle of a majority and outputted through an OR gate 13 to an interface 9. Consequently, for example, when the input circuit 8A breaks down and a normal signal is outputted from input circuits 8B and 8C, the majority circuit 12 compares the inputted data A-C, selects the most common data B and C and outputs them to a CPU unit 3. Thus, the signal from an external switch 6 can be correctly inputted to the CPU unit 3, and respective types of the sequence can be correctly satisfactorily controlled without being accompanied by the system-down.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in input units for programmable controllers.

[Prior Art] Sequence controllers are used in a wide range of industrial fields to accurately control and monitor production stages that combine various types of automatic processing lines, assembly lines, and other machines. The complex sequence control of various loads is performed automatically and with high precision.

In particular, the loads that have been controlled in recent years have been computers, NCs,
Many devices or robots are organically connected, and therefore sequence control of these loads requires highly accurate monitoring of the entire line, abnormality detection, tracking positioning, and measurement. There is.

FIG. 3 shows a suitable example of such a sequence controller.As shown in the figure, recent sequence controllers have versatility for a wide range of different control targets, and In order to be able to quickly respond to changes and expansions, the sequence controller itself is being unitized, and various circuit devices are formed into units that can be detached from the sequence controller base (1). There is.

In the figure, each unit includes a power supply unit (2), a sequence CPU unit (3), an input unit (4), and an output unit (5), and if necessary, multiple input/output units may be added or special units may be added. The unit is configured to be attachable to a sequence controller base (1).

In such a programmable controller, external signals are input to the C through the input unit (4).
The signal is input to the PU unit (3) and is configured to be capable of executing various controls.

FIG. 4 shows an example of an input unit (4) that has been widely used in the past.
Signals from the outside, such as on/off signals from the switch (6), on/off signals from the limit switch, on/off signals from the digital switch, etc., are input to the input circuit (8) via the input terminal (7). After being converted into a digital signal for data processing, the interface (9)
The output signal is output to the CPU unit (3) via the CPU unit (3).

By the way, in such an input unit (4), the input circuit (8) receives an AC switch signal of 100V to 200V, for example, as a human input signal of the external switch (6).
Alternatively, a 24V to 12V DC switch signal is often input, so this input circuit (8) includes a step-down section that steps down the input signal to, for example, a 5V signal for digital processing, and a signal input side and output side. A further insulating section, such as a photocoupler, is provided to insulate the two sides from each other and prevent noise from entering.

Since each of these circuit parts constituting the input circuit (8) is configured as a discrete circuit, failures due to poor contact due to mechanical shock or other factors are likely to occur. Since a high surge voltage is input to each part of the circuit as an external switch is turned on and off, the input circuit (8) often causes a failure due to the surge voltage.

[Problems to be solved by the invention] However, in the conventional input unit (4), the input circuit (8)
Every time a failure occurs, the problems detailed below occur, so an effective countermeasure was desired.

(a) First, in such a conventional device, the input circuit (8)
When the other parts, such as the interface (
9) and input terminal (7) are working properly,
Including these, the input unit (4) itself has to be replaced, and there is a problem in that the cost for failure recovery becomes extremely high.

(b) Furthermore, when a programmable controller is used to perform sequence control of an important system, it is necessary to perform control operations for the system without bringing the system down during the operation.

Despite this, such conventional devices have the problem that if the input circuit (8) fails, the system itself must be stopped and the input unit (4) must be replaced.

(c) In addition, in such an input unit (4), even if there is no failure in the input circuit (8) itself, due to various causes such as external noise, leakage current, deterioration of component constants, etc. There are cases where the on signal of the switch (6) cannot be taken as an "on signal", and in such cases,
There is a problem in that an erroneous signal is supplied from the input unit (4) to the CPU unit (3) as input data.

The present invention has been made to solve this problem, and even if the input circuit fails, a normal input signal can be continuously supplied to the CPU unit without bringing down the system. Furthermore, an input unit for a sheep/sunon trawler that can always supply accurate input signals to a CPU unit is obtained. Ding, and 4 purposes.

[Means for Solving the Problems] The human controller for sequence second and CI controllers according to the present invention has input circuits for inputting external signals and input circuits for each of these input circuits. The output data is selected based on the principle of majority decision.1. A majority decision circuit outputs the output data to the interface.

[Operation] With the above configuration, even if an erroneous signal is output from any one of the input circuits, the majority circuit determines that the data output from the remaining input circuits is correct, Since the output is directed to the interface, it is possible to always output accurate input signals to the CPU unit.

Furthermore, even if one input circuit fails for some reason, the majority circuit selects and outputs the output of the remaining two input circuits, so accurate input signals can be continuously sent to the CPU unit without system failure. We can supply to you.

In particular, by forming each input circuit to be detachable from the input unit, even if a failure occurs in one of the input circuits, it is possible to recover from the failure by replacing only that input circuit. The cost required for this can be significantly reduced compared to conventional devices, and the restoration can be performed without system down.

[Example] Next, a preferred example of the present invention will be described based on the drawings. Note that parts corresponding to those shown in FIGS. 3 and 4 are designated by the same reference numerals, and their explanations will be omitted.

FIG. 1 shows a preferred example of an input unit (4) for a sequence controller according to the present invention, and the characteristic feature of the present invention is that at least three or more input circuits (8) are provided, and each input The purpose is to select the output of the circuit (8) based on the principle of majority voting and output it to the interface (9).

In this embodiment, the input circuit (8) is (8A), (8
A total of three input circuits (8A), (8B), and (8c) are provided, and the outputs (A) and (8C) are
B) and (C) are output to the data determining circuit (10).

FIG. 2 shows a specific circuit configuration of the data determining circuit (10) in the present invention, and in the present invention, the output (A) of each input circuit (8A), (8B), (8C), (
B) and (C) are input to the majority circuit (12) via the switch circuit (11), where each of these input data (A
), (B), and (C) are selected based on the principle of majority voting and outputted to the interface (9) via the orgame-1-(13).

Therefore, for example, if the input circuit (8A) fails, the input circuit (8A)
Assuming that a normal signal is output from 8B) and (8c), the majority circuit (12) will output the input data (
A), (B), and (C) are compared, and based on the principle of majority decision, the most common data (B) and (C) are selected and outputted to the CPU unit (3).

In this way, according to the invention, if the input circuit (8)
Even if any of the input circuits (8) malfunctions, or if an incorrect signal is temporarily output from any of the input circuits (8) for any reason, the majority circuit Due to the function of (12), accurate human input signals can always be output to the interface (9).

Therefore, it is possible to accurately input signals from the external switch (6) to the CPU unit (3) from the input unit (4), allowing various sequence controls to be performed accurately and without system down. It becomes possible to do so.

Further, in the present invention, the data determining circuit (10) is provided with an abnormality detection circuit (14), and the abnormality detection circuit detects the output data (A) of each input circuit (8A), (8B), (8C). , (B), and (C) to detect whether an abnormality has occurred in any of the input circuits (8).

If any abnormality is detected, an abnormality detection signal is output to the display circuit (15), and the operator is informed that an abnormality has occurred in one of the input circuits (8). The input circuit (8) in which the occurrence occurred is displayed.

Therefore, each input circuit (8A), (8B), (8C)
By making the input circuit removable from the input unit, the operator only has to replace the input circuit in which an error has occurred with a new input circuit, making it possible to quickly perform recovery operations in response to the occurrence of an error without system downtime. becomes.

In particular, in this embodiment, when some abnormality occurs in the input circuit (8), instead of replacing the input unit (4) itself as in conventional devices, the input circuit (8) that has occurred in the abnormality is simply replaced. Since only one part needs to be replaced, recovery from the occurrence of an abnormality can be performed at an extremely low cost.

Further, in this embodiment, the switch circuit (11) is provided with two sets of switches (16) and (17), and the switch circuit (11) is configured to operate when the abnormality detection circuit does not detect any abnormality. is formed so that all the switches (16) are turned on, the switch (17) is connected to the open terminal (d), and the output of the majority circuit (12) is directly outputted to the interface (9).

This switch circuit (11) is connected to the abnormality detection circuit 1.
4 is any input circuit (8A), (8B), (8C)
If an abnormality is detected, all switches (16) are turned off and the input data (A) and (B) are directed to the majority circuit (12).
), (C) are not supplied, and at the same time, based on the output of the abnormality detection circuit (14), the normal input circuit (8
) is configured to select the data being outputted using the switch (17) and output the selected data to the interface (9) via the OR gate (13).

In this embodiment, when an abnormality is detected in the input circuit (8A), the output (B) of the input circuit (8B) is selected and sent to the interface (9) via the switch (17) and the OR gate (13). It is configured to output to

In addition, if an abnormality is found in the input circuit (8B),
Similarly, the output C of the input circuit (8C) is configured to be output to the interface (9).

Furthermore, if an abnormality is found in the input circuit (8C),
The output (A) of the input circuit (8A) is selected and similarly outputted to the interface (9).

In this way, according to the input unit (5) of the present embodiment, the abnormality detection circuit (14), the switch circuit (11), and the majority decision circuit (12) work together to always interface normal input data. (9) Supply to. Therefore, if a failure occurs in any of the input circuits (8) from the input unit (4), even if an incorrect signal is output, accurate input data will always be sent to the CPU unit (
3), making it possible to perform accurate and stable sequence control.

Although the above embodiment has been described with reference to the case where three input circuits (8) are provided, the present invention is not limited to this, and it is also possible to provide four or more of these input circuits as necessary. Preferably, an odd number rather than an even number of these input circuits (8) are provided, so that the principle of majority decision is more effectively exerted, and it becomes possible to select an input signal accurately.

[Effects of the Invention] As explained above, according to the present invention, at least three input circuits are provided and data output from each input circuit is selectively outputted to an interface based on the principle of majority decision. Even if an error occurs in one of the input circuits, it is possible to always supply accurate input signals to the CPU unit without system down, and as a result, various sequence controllers can be operated stably. Moreover, it becomes possible to perform the process with high precision.

Furthermore, according to the present invention, each input circuit is made removable, so even if a failure occurs in one of the input circuits, there is no need to replace the input unit itself as in conventional devices; Since it is sufficient to replace only the damaged input circuit, it is possible to reduce the time and cost required for recovery from a failure by a large [11].

Further, according to the present invention, by providing an abnormality detection circuit that collates the data of each input circuit and detects an input circuit in which an abnormality has occurred, the operator can quickly know the occurrence of an abnormality, and It is now possible to quickly replace circuits, making the operation of the entire sequence controller more stable7.
It is also possible to do this with high precision.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a preferred example of an input unit for a sequence controller according to the present invention, and FIG. 2 shows a specific circuit configuration of a data determining circuit used as a part of the circuit shown in FIG. 1. FIG. 3 is an explanatory view of the external appearance of a unitized sequence controller, and FIG. 4 is a block diagram showing an example of a conventional input unit for a sequence controller. In the figure, (3) is the CPU unit, (4) is the input unit, (6) is the switch, (8A), (8B), (8C
) is an input circuit, (9) is an interface, (10) is a data decision circuit, (12) is a majority decision circuit, (14) is an abnormality detection circuit, and (15) is a display circuit. Identical symbols in the figures indicate the same - or A considerable portion is shown.

Claims (4)

[Claims] (1) In an input unit for a programmable controller that inputs an external signal via an input circuit and outputs the output of the input signal to a CPU unit via an interface, at least three or more of the input circuits are provided, and An input unit for a programmable controller, comprising a majority circuit that selects output data from each input circuit based on the majority principle and outputs the selected data to an interface. (2) An input unit for a programmable controller in the apparatus according to claim (1), wherein the plurality of input circuits are formed to be detachably attached to the input unit. (3) In an input unit for a programmable controller that inputs an external signal via an input circuit and outputs the output of the input circuit to a CPU unit via an interface, at least three input circuits are provided, and each The output data of the input circuit is formed to be outputted to the interface via a data decision circuit, and the data decision circuit is a majority decision circuit that selects the output data of each input circuit based on the principle of majority decision and outputs it to the interface. , an abnormality detection circuit that compares output data of each of the input circuits and detects an abnormality in the input circuit; and a display circuit that displays an input circuit in which an abnormality has occurred based on the detection data of the abnormality detection circuit. Input unit for programmable controller. (4) An input unit for a programmable controller in the apparatus according to claim (3), wherein each of the input circuits is formed to be detachably attached to the input unit.