Programmable controller

Details Programmable controller Programmable controller

1998-06-19

2001-08-07

Etienne, Ario (Department: 2155)

Electrical computers and digital data processing systems: input/

Intrasystem connection

Bus access regulation

C710S200000, 36, 36

Reexamination Certificate

active

06272578

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a programmable controller.
BACKGROUND ART
A user program for controlling a controlled system is contained in a programmable controller. The user program is generally described by a ladder language, an SFC (a sequential function chart), and so forth.
The user program is constituted by a plurality of modules in many cases. The modules are respectively allocated parts of the control of the controlled system. Division of the user program into the plurality of modules is particularly effective in a case where the control of the controlled system is complicated. It is also effective in order to facilitate the creation of the user program or share the creation of the user program among a plurality of persons even if a control system is not necessarily complicated. The control system is divided depending on control equipments constituting the controlled system, the types of driving devices, the control functions and so forth, and the control of each of parts formed by the division is allocated to each of the modules.
FIG. 7
illustrates one example of a control system using a programmable controller. There is a conveyer for carrying an article from a point x
1
to a point x
2
. A motor M
2
is provided for driving the conveyer in the forward direction (rightward in FIG.
7
). A conveyer for carrying the article from the point x
2
to a point x
3
is driven in the forward direction by a motor M
3
. It is necessary to return the article from the point x
3
(or x
2
) to the point x
2
(or x
1
) in an emergency, or in order to cope with the other situation. A motor M
1
is provided in order to drive the above-mentioned two conveyers in the reverse direction (leftward in FIG.
7
). A plurality of user program modules share the control of the control system depending on the share of driving devices (control equipments), the control ranges, the driving directions and so forth.
Consider a case where the control range is divided into right and left control ranges with the point x
2
used as the boundary, and user program modules sharing each of the control ranges are created. In the left range, a switch SW
2
for moving the conveyer in the forward direction and a switch SW
1
for moving the conveyer in the reverse direction are provided in a control panel
51
. In the right range, a switch SW
4
for moving the conveyer in the forward direction and a switch SW
3
for moving the conveyer in the reverse direction are provided in a control panel
52
. Switch inputs from the switches SW
1
to SW
4
are fed to an I/O unit
41
connected to a programmable controller
40
. The motors M
1
to M
3
are driven by output signals from the I/O unit
41
. A user program for controlling the motors M
1
to M
3
in response to the inputs from the switches SW
1
to SW
4
is stored in a user program memory in the programmable controller
40
.
A user program module A for controlling the left half range and a user program module B for controlling the right half range are illustrated by a ladder diagram in FIG.
8
.
In the ladder diagram, reference signs m
1
, m
2
and m
3
denote relays for respectively representing outputs for driving the motors M
1
, M
2
and M
3
. Reference signs s
1
, s
2
, s
3
and s
4
denote input contacts (normally open contacts) respectively representing signals fed from the switches SW
1
, SW
2
, SW
3
and SW
4
. Reference signs c
1
, c
2
and c
3
denote internal contacts (normally closed contacts) respectively opened or closed by the relays m
1
, m
2
and m
3
.
In the module A, when the switch SW
2
is turned on, the input contact s
2
is closed, whereby the relay m
2
operates so that the motor M
2
is driven, provided that the internal contact c
1
is on (provided that the motor M
1
is not driven) (an address 00093). When the switch SW
1
is turned on, the input contact s
1
is closed, whereby the relay m
1
operates so that the motor M
1
is driven, provided that the internal contacts c
2
and c
3
are on (provided that both the motors M
2
and M
3
are not driven) (an address 00088).
In the module B, when the switch SW
4
is turned on, the input contact s
4
is closed, whereby the relay m
3
operates so that the motor M
3
is driven, provided that the internal contact c is on (provided that the motor M
1
is not driven) (an address 00157). When the switch SW
3
is turned on, the input contact s
3
is closed, whereby the relay m
1
operates so that the motor M
1
is driven, provided that the internal contacts c
2
and c
3
are on (provided that both the motors M
2
and M
3
are not driven) (an address 00152).
To prevent an equipment or a device from starting its operations or prevent the operations from being continued unless conditions set in advance are satisfied is referred to as interlock. In the above-mentioned examples of the modules A and B, the internal contacts c
1
, c
2
and c
3
realize the interlock. A program for realizing the interlock (including its part) is referred to as an interlock program.
In the module A, inputs are si and s
2
, and outputs are m
1
and m
2
. The internal contacts c
1
and c
2
are respectively related to the outputs m
1
and m
2
. However, the internal contact c
3
is related to the output m
3
of the module B. Similarly, in the module B, the internal contact c
2
is related to the output m
2
of the module A.
As described in the foregoing, in a case where the control of the controlled system is divided into a plurality of parts from the points of view of the control equipment or device or the driving device constituting the controlled system, the control range, the control function and so forth, and the parts of the control are respectively allocated to the user program modules, the interlock program in each of the user program modules include an element related to the module and an element related to the other module in many cases. When one of the user program modules is created, the description of the element related to the other user program module particularly involves difficulties in many cases. The reason for this is that when the one module is created, the input and output states, the order in which programs are executed and so forth in the other module must be sufficiently grasped. When a plurality of persons share the creation of the modules, it involves further difficulties.
DISCLOSURE OF INVENTION
An object of the present invention is to provide the structure of a user program, including a part related to interlock, which is relatively easy to create.
Another object of the present invention is to provide a programmable controller storing a user program which is relatively easy to create and a method of operating the same.
A user program for a programmable controller according to the present invention includes a control program from which a description defining interlock conditions is excluded and an interlock program defining interlock conditions for the result of processing conforming to the control program and described separately from the control program, and has a structure ensuring that the interlock program is executed after the control program is executed.
The user program is stored in a memory device of a programming device (a semiconductor memory, a hard disk, a floppy disk, etc.), a portable recording medium (a CD-ROM, a floppy disk, etc.), a user program memory of the programmable controller, or the like.
Such ensuring that the interlock program is executed after the control program is executed can be realized by various methods. When the user program is executed in the order of addresses, for example, an address having a small value may be assigned to the control program, and an address having a large value may be assigned to the interlock program. An identification code for discriminating between the control program and the interlock program may be assigned.
To what part the user program should be described as the interlock program can be determined depending on the intention of a programmer. The interlock conditions generally mean interlock conditions of an output.
The

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