An evaluation and comparison of PLC programming techniques : innovation report
Hajarnavis, Vivek (2006) An evaluation and comparison of PLC programming techniques : innovation report. EngD thesis, University of Warwick.
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Few significant changes in Programmable Logic Controller (PLC) software design
techniques have taken place since PLC's were first introduced in the 1960's. Programs
written in the traditional language used in PLC's, ladder logic, are generally thought to
be difficult to maintain and modify, and thus ill suited to the support of modem flexible
This work demonstrates that the choice of PLC software structure used in a project has
an impact on process flexibility with an appropriate choice providing significant cost
savings in development time.
An overview of work on formalised programming tools conducted in academia is
provided together with a report on the PLC software structures used in industry. The
factors influencing the choice of PLC and software structure are identified. Familiarity
was found to be a major factor influencing selection. A method for comparing code
structures, which allows the results to be expressed as a time saving (and consequently a
cost) has been created. Implementation of this approach was used to show that the
formalised programming tool under test provides a 33% increase in "right first time"
rate together with an 80% time saving over traditional contact based ladder logic.
Among experienced practitioners, performance with step-based ladder logic was found
to be a close match to the formalised tool, demonstrating that the commonly perceived
limitations are the result of the structure in which the language is used rather than a
function of the programming tool itself.
Further investigation of participant preferences among skilled PLC users showed a
mismatch between their performance with a tool and their preference, with at least 25%
selecting a tool based on their prior knowledge rather than performance. This highlights
the need for the use of objective measures when conducting evaluations between
products and technologies.
With the information provided in this work, automation end users are provided with a
mechanism for ensuring the selection of automation tools best suited to their business
needs, whilst at the same time providing automation vendors with the ability to best
demonstrate the strengths of the products.
|Item Type:||Thesis or Dissertation (EngD)|
|Subjects:||T Technology > TS Manufactures|
|Library of Congress Subject Headings (LCSH):||Programmable controllers, Manufacturing processes -- Automation|
|Official Date:||August 2006|
|Institution:||University of Warwick|
|Theses Department:||School of Engineering|
|Supervisor(s)/Advisor:||Young, Ken ; Daniels, Ray|
|Extent:||x, 82 leaves|
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