Started from 1992, PLCopen began to impel and the support
programming standard, this association declared this standard only had
less training, the logical organization, modular as well as the use
modern software technology, and pointed out: "Each procedure all
is the structure, strengthens its repetition use, the reduction makes
a mistake as well as the enhancement programming and user's
efficiency."
"Simultaneously, this standard permits two kind of developments
procedures the way: From the top downward and from bottow to
top. You may assign the entire application and divide into it
several parts, explained you use variable and so on. You also
may start from the base to apply carry on the programming, for example
through the function and the function block which derives carries on.
Which way no matter you do choose, the development environment
will help you to complete the entire process, "PLCopen said.
In the IEC61131-3 5 basic languages are:
- The smooth functional diagram (SFC) - it not merely is one
language, is one organization control procedure graph way.
- Trapezoidal chart (LD) - multipurpose to North America, by
graphic mode expression electronic contact and coil as well as special
instruction block stave. Its source from relay
trapezoidal chart logic.
- Instruction list (IL) - one kind of similar assembly program
based on text language. If corresponds in is LD which Europe.
- Structure text (ST) - one kind of similar Pascal based on text
language.
- The function block chart (FBD) - one kind corresponds to the
circuit diagram graphical language. FBD widely uses in the
process industry.
Some IEC standard provides much about the function block
information: If IEC61499 and IEC61804, they stress on the
process industry. In the function block has loaded the
algorithm, like this is not skilled in software the person is easier
to understand and to apply them.
Must understand the more related functions block the
information, sees also www.controleng.com/issues, September, 2002
"part automation realization modelling and control."
On www.iec.org, IEC has published "the programmable controller -
third part: Programming language." IEC61131-3 was the
programmable controller which defined in the IEC61131 first part has
stipulated the programming language grammar and the semantics.
Its price approximately is 205 US dollars. Also some about
the IEC publication is "the programmable controller - 8th part:
The programming language application and the realization leads
then."
PLCopen (www.PLCopen.org) emphatically to programs and
participates in the development programming standard to the control
system technical committee's introduction.
IEC61131-3 merit and shortcoming
Wolfgang Langer, Manager Shi Naide
electrical company's software product, has induced the IEC61131-3
merit and the shortcoming as follows:
Merit:
?less repetitions training expense - because in the different
producer's between, its IEC programming language looked like is
similar;
?emphatically to question solution and software repetition
use;
?works as the cut language, very little has in the
programming misunderstanding and the mistake; All IEC language
working condition is same;
?a stronger uniformity - may use the many kinds of tools
which provides by the different supplier. PLCopen and the
manufacturer impel the IEC standard together the development, causes
it to conform to mutually the operational standard.
Shortcoming:
?too are many the characteristic which may elect;
?when defines a procedure, not to its page of face values
size realization limit formulation;
?the definition has not needed to realize smallest subset;
?has not defined the realization 最?the system, like
must support how many stave in a procedure;
?has not defined between the language the transformation. |
