Industrial controllers such as the Programmable Controller, PLC or the Programma
ID: 3575703 • Letter: I
Question
Industrial controllers such as the Programmable Controller, PLC or the Programmable Automation Controller, PAC are at the heart of most control applications, and programming these control systems is a time consuming task. Quality, efficiency, and the need to achieve higher levels of automation are the driving forces behind the adoption of software standards in all areas of computing. Discuss the role of the IEC6J131-3 standard in programming industrial controllers. In your answer make reference to the following; Software architecture and execution control Standardization Programming User derived elementsExplanation / Answer
The IEC 61131-3 standard defines a model that follows modern software engineering concepts. If fully implemented, the model is reasonably complicated. This model incorporates such features as top-down design, structured programming, hierarchical organization, formal software interfaces, and program encapsulation.
Main elements: configuration,resource,program, function blocks
configuration: A body of program that corrospond to the IEC 61131-3. In large complex systems that require multiple cooperating PLCs, each PLC has a separate configuration. A configuration communicates with other IEC configurations within the control system through defined interfaces, called access paths.
resource: It provide support to the system.A resource exists within a PLC, but it may exist within a personal computer to support program testing. It provide interface between a program and the physical I/O of the PLC.
function blocks: function block is a unit of a program in which behaviour of program described.
Program: Program is formed by function blocks intended to perform a task.
Standrisation of IEC 61131-3:
The PLCopen Technical Committee 1, TC1, deals with Standards.IEC 61131-3 standardS are developed by the International Electrotechnical Committee.
The third part defines, as a minimum set, the basic programming elements, syntactic and semantic rules for the most commonly used programming languages. This includes the graphical languages Ladder Diagram and Functional Block Diagram, and the textual languages Instruction List and Structured Text, as well as means by which manufacturers may expand or adapt those basic sets to their own programmable controller implementations.
Factors of standrisation:
->Genral information
-> equipmemnt requirment and test
->programming languages
->User guidence
->Messanging service specification
Programming: While designing code for IEC 61131-3, we can use five languages
->Ladder Diagram (LD)
->Function Block Diagram (FBD)
->Sequential Function Chart (SFC)
->Instruction List (IL)
->Structured Text (ST)
point to remember while programming:
->Ease of maintenance by the final user: SFC;
->peed of execution by the PLC: IL or ST;
->Applications mainly using digital I/O and basic processing: LD or FBD;
->Ease of implementing complex mathematical operations: ST; and
Not all PLCs are capable of running the various IEC languages due to lack of memory or processor speed.
User derived elements:
Data Typing:
It is used to define the type of any parameter used. This avoids for instance dividing a Date by a Integer. Common datatypes are Boolean, Integer, Real and Byte and Word, but also Date, Time_of_Day String. Based on these, one can define own personal data types, known as derived data types.
Variables: Variables is something in which values are assigned. The scopes of the variables are normally limited to the organization unit in which they are declared example local,global.