017 - The Design of Portable Logic Controller (PLC) Training System For Use Outside of Automation Laboratory
017 - The Design of Portable Logic Controller (PLC) Training System For Use Outside of Automation Laboratory
017 - The Design of Portable Logic Controller (PLC) Training System For Use Outside of Automation Laboratory
Michael Barrett
FAS Training Centre, Athlone, Co.Westmeath, Ireland.
Email: michael.barrett@wr.fas.ie
ABSTRACT
Programmable Controllers are predominately laboratory based subjects as they require “hands on”
electrical wiring, interface to industrial electrical components, to Human Machine Interfaces
(HMI) and may be networked. As PLC courses evolve to incorporate the IEC 6-1131 defined
programming languages with the resultant extra software theory learning requirement and an
increasing demand for in-company courses a requirement arises for a PLC system which is
portable and can be accommodated in a training or class room. This paper seeks to address this
issue.
INTRODUCTION
The PLC is a robust industrial computer which accepts input data, both digital and analogue, from
switches and sensors and controls outputs to drive devices such as motors, pneumatic devices and
status indicators. At its most basic the PLC replaces relay logic circuits, at its most advanced it can
implement Proportional Integral and Derivative (PID) control algorithms over networks. While the
Programmable Controller is by far the most common process control mechanism in the
manufacturing spectrum of large to small business it has also found a niche in environment
control, food processing, mining and in automated test equipment [1] [2]. Programmable
controllers were developed in the U.S. for the motor manufacturing industry in the 1960s. By the
late 1970s they appeared in the Irish industrial scene. Today due to their increasing sophistication
and falling costs they are to be found in the smallest production environment. The PLC
programming environment may be dedicated terminal or a Personal Computer (PC). Latterly, with
the event of the range of programming languages defined by IEC 6-1131 the PC is the favoured
programming environment. Ladder Logic (LL) is currently the most popular language [3]. There is
however, anecdotal evidence that the other defined languages are slowly gaining acceptance.
1
International Symposium for Engineering Education, 2008, Dublin City University, Ireland
courses, as for all control engineering courses, must deliver “a balance of practical skills and
theoretical knowledge” and as such are laboratory based [4]. Increasingly, in response to demands
from industry PLC courses are being run in-house, in training rooms, away from the traditional
venue of the automation laboratory using hardwired “kits” and PC based simulators.
• Simulators
Simulators may be sub-divided further in to two categories:
PC based using an actual PLC. Simulators generally have a range of industrial processes (“virtual
2
International Symposium for Engineering Education, 2008, Dublin City University, Ireland
machines”) such as “pick and place” and “tank level control systems” [7]. The programmer selects
a “virtual machine” from a menu, writes the program to control it and downloads it to the PLC.
The PC based simulator communicates serially with the PLC simulating the “virtual machine”.
In the second type the PLC and the machine or process are both “virtual”, that is no physical PLC
exists. Again, as with the previous system the programmer selects a “virtual machine” from a
menu, writes the control program on the PC based “virtual PLC”. The “virtual machine” is then
controlled by the “virtual” PLC [8].
Simulators can be used effectively for engineering training generally [9]. However, for PLC
training, as with the hard wired kits the simulators are best exploited by students who have the
applied skills required to interface the PLC to peripheral devices, have some programming skills
and want to develop those programming skills. The simulators in common with the hardwired kits
do not provide the practical experience of wiring up the PLC, interfacing it to peripheral devices
and generating the electrical drawings and the I/O List to document the system.
3
International Symposium for Engineering Education, 2008, Dublin City University, Ireland
Figure 1 (a) System platform and (b) with PLC and peripherals.
CONCLUSION
The system has been used in a classroom situation three times over the last year. The students were
a combination of technicians, engineers and electricians all with industrial manufacturing
experience. All had encountered PLCs in their work and were aware of their uses but only one had
experience of programming or faultfinding. The training courses were problem based where
students were asked to design a PLC controlled system to control two electrical contactors as
drivers for three phase motors to run two conveyors. This involved analysing a requirements
statement, producing an electrical drawing, producing SDLC documentation and connecting the
PLC to the power supplies and peripheral equipment. For testing purposes test cases to test the
requirements were generated. Black box and white box testing was carried out.
Feedback from participating students was positive, the “hands on” aspect being especially well
received. While the system cannot substitute for the laboratory for advanced courses it has found a
niche for the purpose for which it was intended, delivering introductory courses in situations where
access to the automation laboratory is not feasible.
FUTURE DEVELOPMENTS
While the courses currently being run are confined to Ladder Logic programming and digital I/O it
is proposed to extend the syllabus to include analogue I/O and the Sequential Function Chart
(SFC) programming language. An increasing demand is emerging for training in data capture and
Overall Equipment Effectiveness (OEE) measurement. By the addition of an Ethernet module OEE
data collected by the PLC may be networked and presented on remote PCs as part of a
Management Information System (MIS).
4
International Symposium for Engineering Education, 2008, Dublin City University, Ireland
REFERENCES
1. Hughes, T., A., “Programmable Controllers - 4th Edition”, ISA Press, 2005
2. Barrett, M., “PLC Controlled Automatic Test Equipment”, Electro-Technology, The Institution
of Electronics and Electrical Incorporated Engineers, April/May 1997
3. “IEC 1131 -3 Programmable Controllers - Part 3: Programming
Languages“, International Electrotechnical Commission, 1993
4. Verwer, A., “The impact of IEC (6)1131-3 on the teaching of control engineering” IEE
Colloquium on - The Application of IEC 61131 to Industrial Control: Improve Your Bottom Line
Through High Value Industrial Control Systems (Ref. No. 1999/076), Volume, Issue, 1999
Page(s):10/1 - 10/4
5. http://www.adwin.com/elec/programable/pc_english.pdf (accessed June 2008)
6. Prendergast, J., Barrett, M., “An Investigation into the Relevance of Documentation for Problem
Solving in Equipment Controlled by Programmable Logic Controllers (PLCs)”, Proceedings of the
International Symposium for Engineering Education, ISEE-07, Dublin, 2007
7 .http://shopv2.mrplc.com/product_info.php/products_id/65? (accessed June 2008)
8. http://www.autoware.com/english/pc-sim.htm (accessed June 2008)
9. Christie, A.,M., “simulation: an enabling technology in software engineering”,
http://www.sei.cmu.edu/publications/articles/christie-apr1999/christie-apr1999.html (accessed
June 2008)
10. Dickinson, A., Johnson, D.M. “ A Low-Cost Programmable Logic Control (PLC) Trainer for
Use in a University Agricultural Electricity Course”, Journal of Agriculture Technology,
Management and Education, Vol.21, March 2006
11. Kheiralla, A., F., Siddig, O., Elhaj Mokhtar, A., A., Esameldeen, M., Abdalla, O., “Design and
Development of a Low Cost Programmable Logic Controller Workbench for Education Purposes”,
Proceedings of the International Conference on Engineering Education - ICEE-2007, Coimbra,
Portugal, 2007.