IEC 1131-3 software: One advanced
industry control programming system
Conforms to the IEC 1131-3 software
system is industry control system software which a structure is
perfect, may duplicate uses, may maintain, not only can apply in PLC
(programmable controller), moreover also can apply in the control
industry and in manufacture process all software, is one advanced
industry control programming system.
IEC 1131-3 standard including two parts:
Programming and public element. Programmed partially
described two important models: IEC software model
and communication model. The public element has defined in the
programming system needs the data type. This article through to
the IEC 1131-3 standard these two partial descriptions,
theoretically will analyze, elaborated the IEC 1131-3
programming system will have the merit, and will let us study the
advanced design thought which IEC 1131-3 elaborated.
First, IEC 1131-3 two important
models
The IEC 1131-3 standard has two models:
IEC software model and communication model.
These two models constituted the realization to conform to the
IEC 1131-3 international standard programming system
concept foundation, they not only were the IEC 1131-3
programming system distinguish between the traditional PLC programming
system important symbol, moreover also was the IEC 1131-3
programming system superiorly is at to the traditional PLC programming
system reason. How did the IEC software model
theoretically describe decomposed slightly a complex procedure into
certain is different may manage the part, and in decomposes between
the part to have one by one clear and the standard connection method;
How described PLC to realize many independent procedures
simultaneously the loading, the movement; How described the
system to realize to the procedure execution complete control and so
on. How did the communication model similarly theoretically
describe the different procedure organization unit ( POU ¨C Program Organization Units)
between to exchange the information the method. The procedure
organization unit includes the procedure, the function block and the
function.
In order to describes the IEC software model well,
we first describe IEC 1131-3 software and the actual system relations through an actual application system, then further
explains 1131-3 software model again.
Second, IEC 1131-3 software and actual system
relations
Like chart 1 is as soon as uses PLC the direct digital
control system. Comes to transform from the physical sensor
continuous signal after the digital sampling signal, the PLC control
system may move such as the proportion, the integral, the differential
(PID) and so on the algorithm has the control signal output, finally
realizes to installs the position the control. In chart 1, the
IEC 1131-3 software supposition, comes from the sensor or
changes delivering
The chart as soon as applies the PLC system
the direct digital control system
Exterior value is directly put on section of specific
memories areas, simultaneously, after the procedure movement produces
the result is also put on section of specific memories areas, renews
these memory area values, namely has realized to the execution or the
monitor actuation. Has not certainly defined to the PLC I/O
installment memory mapping in the standard, it can have the very big
difference along with the different PLC merchant.
Third, IEC software model
The IEC 1131-3 software model like chart
two shows. This software model is one kind of stratification
structure, each hid its lower level many characteristic. IEC 1131-3 has this kind of stratification structure,
constituted IEC 1131-3 software superiorly to the
traditional PLC software rationale, is IEC 1131-3
software 先进�manifesting. Under we first describe software
model each part of concept, simultaneously analyzes, summarizes the
merit which the IEC 1131-3 programming system has.
1. dispositions, resources, procedure and duty
In the model uppermost layer is software "the
disposition", it equates to PLC software, uses in concrete application
definition PLC behavior entire software, it and the disposition system
actual process is different. If is complex in the automatic
production line in which is composed by many PLC, in each PLC software
is independent "the disposition". "The disposition" may "the
disposition" carry on the communication with other IEC through the
definition connection.
In each disposition, some or many "the resources", "the
resources" not only has provided a support program for the operating
procedure, moreover it had reflected the PLC physical structure,
channel has provided a connection in the procedure and PLC between the
physical I/O. A IEC procedure only has after loads "the
resources" to be able to carry out. "The resources" usually puts
in PLC, but also may put in other systems.
A IEC procedure may use the different IEC programming language
to compile. The typical IEC procedure by the function block
which many interlocks is composed, between various functions block may
mutually exchange the data. A procedure may the read-write I/O
variable, and can and other procedure communications. In
procedure different partial executions pass "the duty" to control.
After "the duty" disposes, may control a series of procedures
and/either the function block periodically executive routine or by a
specific event triggers starts the executive routine. The IEC
procedure or the function block usual maintenance complete is ready to
be used the condition, only has when is specific the duty which
disposes is come by periodically the execution or changes by a
specific variable condition triggers the execution the situation, the
IEC procedure or the function block talent can carry out.
2. functions blocks and function
The function block concept is a IEC 1131-3
standard programming system important characteristic. Any
function block may use the function block which other smaller is
easier to manage to program, like this may found a stratified
structure reasonable procedure by many functions blocks. IEC 1131-3 also allows the programming personnel to use the
existing function block and other software parts produces the new
function block.
Chart two: IEC software model
The function also is in a IEC 1131-3
standard important concept, but has not displayed in the software
model, it frequently causes the people and the function block
confusion. The function is some in the procedure implementation
software part, these software parts can have the corresponding output
result to a series of specific input values, like arithmetic function
COS (), SIN () and so on. In the IEC 1131-3
standard has massively uses in the processing different data type
function.
3. variables and access path
In the disposition, the system resources, the procedure,
the function or in the function block, may state and use the partial
variable, the overall situation variable, the direct variable.
The partial variable is merely can in the disposition, the
resources, the procedure, the function or in the function block the
statement and the deposit and withdrawal variable; The overall
situation variable (or disposition) in stated in a procedure, it can
by the procedure (disposition) in all software part deposit and
withdrawal; Direct variable
Is the PLC procedure memory area straight takes over the
use of the variable which the address variable expressed.
The access path provided has exchanged the data and the
information equipment between the different disposition. In each
disposition variable may the quilt
Other long-distance disposition deposits and
withdrawals. Between the disposition deposits and withdraws the
data and the information may use based on the ethernet network, the
field bus or through the ledger wall main line exchange data.
Fourth, software model to actual system mapping
The IEC software model to the actual system
mapping, has the following different mapping relations in view of the
different system:
1. has a main processor the small system: The
small system model typically degeneration is a disposition, a
resources and a procedure.
2. has the multi-processor a more complex system:
Entire PLC is regarded as a disposition, each processor with a
resources description, a resources supports or the multi- strip
procedure.
3. regarding disperses the PLC system: Will disperse the PLC system
to contain many dispositions, a disposition will correspond many
processors, each processor with a resources description, a resources
will support or the multi- strip procedure.
The IEC software model may fully adapt in from
simply to the more complex PLC system, even is the extremely complex
PLC system, this greatly expanded the traditional PLC application
scope and the domain.
Fifth, IEC software model merit
The IEC software model has the following
merit:
1. simultaneously loads, starts and carries out many
independent procedures in PLC: The IEC 1131-3
standard allows "the disposition" in to have many "the resources",
each "the resources" can support many procedures, this causes in PLC
to be allowed simultaneously to load, to start and carries out many
independent procedures, but the traditional PLC procedure only can
simultaneously move a procedure.
2. realizations to procedure execution complete control:
IEC1131-3 standard this kind "the duty" the mechanism, has
guaranteed the PLC system to the procedure execution complete control.
The traditional PLC procedure only can the progressive scanning,
the executive routine, not be able fixed time to carry out to some
section of procedures according to user's actual request, but the IEC 1131-3 procedure permission procedure is
different partially in the different time, by the different ratio
concurrent execution, this greatly expanded the PLC application scope.
3. IEC software model can adapt the very broad scope different
PLC structure: The IEC software model is a international
standard software model, it aims at the concrete PLC system, but has
the very strong serviceability.
4. IEC software model already can suit the
small PLC system, also may suit the bigger dispersion system.
5. IEC software support procedure organization
unit entrusts with heavy responsibility the characteristic:
Software entrusts with heavy responsibility the nature is the
IEC software important merit.
6. IEC software support lamination design:
Complex IEC software usually may through a layer upon layer
decomposition, finally decompose into the program element which may
manage.
Sixth, communication model
According to different communication request, IEC 1,131 standing operating procedures following four kind
of communications model:
1. intercoms: In the procedure, the function
block and between the function interior may the interconnection form a
network, the data message may carry on the communication through this
internal network.
2. game of variables communications: The
overall situation variable may use for to exchange in the function
block with other procedure organization units between the data
message.
3. exterior variables communications: The
IEC 1,131 fifth part defined a communication function
block family to come through a network to exchange the data.
4. uses access path communication: The
deposit and withdrawal variable provided one method to use in from the
long-distance equipment deposit and withdrawal specific variable.
Ding one in the IEC 1,131 fifth part of
communication function block also can in the read-write long-distance
disposition ACCESS variable.
The IEC 1,131 standing operating procedures these
four kind of communications model, nimbly causes not only in the IEC
programming system interior communication, to be convenient, moreover
also effectively supported the IEC programming system function to
expand the request which proposed to the communication, will cause the
new generation of programming system to be allowed effectively to
adapt future to the network, the field bus, the long-distance
communication and so on the new technological development request.
Seventh, public element
The public element described the IEC 1131-3 five kind of programming languages, in the IEC software model and the communication model must
use completely the public programming element variable and the data
type, how produced has named these software elements, statement
variable, variable and data type rule and so on initialization,
realizes the IEC 1131-3 programming system essential
organic constituent.
Eighth, conclusion
IEC 1131-3 software is a function
formidable, the design thought and technological advance and can adapt
the programming system well which the future will develop. |
