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|ladder language vs forte [message #1834364]
||Mon, 09 November 2020 03:39
| joy woo
Registered: May 2019
I used forte to convert two PLC applications,|
i found when the project is a little bit complex,
the way to implent the functionality is more complex,
i think it's the reason why the ladder language has not been elimated
the codesys used ladder+FB way seems to be the most efficent way,
plc only have to consider the value ,
forte not only to consider the event, but also the values, the values
are not shared like ladder, so have to conenct the values many times.
the ECC functionality is also very complex and slow to construct
the functionality comaring to PLC
even using c to implement the loop and logic could be much more efficent,
i think that's the problem why IEC61499 made a little progress till now(not widly used),
i am still confused to try to find out a proper architect/mode to solve this problem.
values driven(ladder language) vs event+values+status machine driven(ECC)
which drive me crazy
[Updated on: Mon, 09 November 2020 03:57]
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|Re: ladder language vs forte [message #1834399 is a reply to message #1834364]
||Mon, 09 November 2020 17:55
| Milan Vathoopan
Registered: August 2016
I think this thread requires a detailed discussion. From my understanding, the conventional industrial systems with fixed production lines or production lines with limited variation points mostly use IEC 61131 based centralized control solutions. Today companies require frequent reconfiguration to meet the market requirements. For implementing frequently re-configurable manufacturing systems, the widely accepted solution so far is employing intelligent modular entities having cognitive capabilities that are controlled in a distributed manner. From my humble opinion, 4diac is best suited (ideally suited) for such a system, though not limited. Here the advantage with 4diac is that, IEC 61499 by definition provides configurability, interoperability and distribution of multi-vendor systems in an event based architecture. If you imagine an IEC 61131 based solution here, you will have to depend on control tools from different manufactures which requires additional effort for configuration and interoperability. (Hopefully this is the theoretical explanation, where 4daic helps you). However, what my understanding is that in many practical cases, considering the current systems we will need both the world working in harmony.
Now coming to the practical solution, when we require a translation of IEC 61131 based program to a IEC 61499 program the following ideas helped us. In 4daic hierarchical control architecture fits the best. It was observed that ladder diagram programs are organized based on areas or sections. The effort to translate the programs reduced, when we could identify part of ladder logic which can be translated as library elements within 4diac, that can be hierarchically organized.
We used the following sequence.
In ladder logic
1) Identify sections or areas in programs, Eg. A reactor in a process plant, a pick and place unit in an assembly line
2) Take a list of actual hardware input, output contacts, analog input, outputs which can be directly modelled using standard function blocks in 4diac (Eg: IX, QX, IW, QW)
3) Retrieve the corresponding algorithm/ sequence of each section or area.
1) Instantiate required no of IX, QX, IW, QW function blocks required to represent the corresponding hardware input/ output in ladder diagram.
2) Analyze if the IX, QX, IW, QW, etc., can be tied to a component. If yes, then tie them to make components, for example an ON/OFF Valve with feedback proximity sensor. becomes a component. When it requires logic to bind them together, use basic function block. The overall logic of the component can be saved in the library as a SubApplication type for example. These components can be reused in several applications (sequences within a factory).
3) Make a hierarchical structure with the components and model their orchestration logic with a basic function block.
4) Continue the steps, until you reach the top. For better organization, you may use further sub applications in between.
However, when systems become larger and larger, the graphical organization becomes a bit difficult with this approach. So I agree with you here that, in a really large factory, a top level sequential logic might help in better organizing the control programs. Experts may add more comments here.
Hope it helps you a bit!
[Updated on: Mon, 09 November 2020 18:01]
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