SAMPLE. UEENEED026B Design a computer based control system. Learner Workbook. UEE07 Electrotechnology Training Package. Version 1.

Transcription

1 UEE07 Electrotechnology Training Package UEENEED026B Design a computer based control system Learner Workbook Version 1 TRAINING AND EDUCATION SUPPORT INDUSTRY SKILLS UNIT, MEADOWBANK Product 5495

2 Acknowledgments The TAFE NSW Training and Education Support Industry Skills Unit, Meadowbank would like to acknowledge the support and assistance of the following people in the production of this learner workbook: Writers: Jeffrey Stokes TAFE NSW Reviewers: TAFE NSW Project Manager: Steve Parkinson TAFE NSW Enquiries Enquiries about this and other publications can be made to: Training and Education Support Industry Skills Unit, Meadowbank Meadowbank TAFE Level 3, Building J, See Street, MEADOWBANK NSW 2114 Tel: Fax: The State of New South Wales, Department of Education and Training, TAFE NSW, Training and Education Support Industry Skills Unit, Meadowbank, Copyright of this material is reserved to TAFE NSW Training and Education Support Industry Skills Unit, Meadowbank. Reproduction or transmittal in whole or in part, other than for the purposes of private study or research, and subject to the provisions of the Copyright Act, is prohibited without the written authority of, TAFE NSW. Training and Education Support Industry Skills Unit, Meadowbank. ISBN Developed by Training & Education Support Industry Skills Unit, TAFE NSW 2011

3 Table of contents Introduction General introduction Using this learner workbook Prior knowledge and experience Unit of competency overview Assessment Section 1: Control System Architecture Microprocessor Based Controllers PC Based Control Systems Distributive and Hybrid Systems Safety Considerations in Control System Design Section 2: Measurement, Signals and Connections Industrial Sensors Controller I/O Electrical Specifications Signal Conditioning and Calibration Input Protection Methods Data Signals and Connections Section 3: Control Programming PLC Programming SCADA Programming Data Acquisition Systems Section 4: Developed by Training & Education Support Industry Skills Unit, TAFE NSW 2011

4 Introduction to Labview Labview Installation and Setup Creating a Virtual Instrument (VI) Introduction to HMI Design Section 5: Analogue to Digital Conversion ADC Methods Resolution and Sample Rate Noise Reduction Data Logging Section 6: Introduction to Visual Basic.net VB.net Installation and Setup Navigating the IDE The Default Form Components and Properties Events, Methods and Functions Data Types and Variable Declarations Testing and Debugging a Program Section 7: Programming Structures If... Then... Else Select... Case For... Next Do... While and Do... Until Writing Function, Moving Objects Developed by Training & Education Support Industry Skills Unit, TAFE NSW 2011

5 Section 8: Advanced Maths Techniques Order of Operations Trigonometric Functions Section 9: Graphical Methods and Techniques Drawing in a Picture Box Form and Component Opacity Section 10: Control Programming Techniques Accessing I/O Devices The Basic Control Loop Timing Functions Counting External Events Reading and Scaling Analogue Values Section 11: Software Design Planning Top-Down Methodology Project Planning Modular Programming Documenting Software Design Projects Section 12: Software Design Implementation Project Control Algorithms Data Logging Features Programming Alarms Developed by Training & Education Support Industry Skills Unit, TAFE NSW 2011

6 12.4 Programming Access Control Managing Project Changes Section 13: Beta Testing and System Commissioning Testing Modules of Code Safety Testing and System Commissioning Commissioning Documentation Operating Manuals and Training Section 14: Data Communications Features Networks Network Topologies Network Standards and Protocols Section 15: Computer Based Control System Project System Planning System Implementation System Problem Solving System Completion Reference list Resource Evaluation Form Developed by Training & Education Support Industry Skills Unit, TAFE NSW 2011

7 Section 1: Control System Architecture 1.1 Microprocessor Based Controllers Control System History Figure 1 Manual Valve Early in the history of what we would call modern industrial development, control systems were manually operated. They relied on human measurement and decision making. This means that they were flawed. Over a period of time many manual systems, especially simple ON/OFF control systems, were replaced with relay control systems that were capable of a level of automation. These were more reliable and saved money because of the lower labour cost. Relay operation is still relatively slow to respond to process changes when compared with electronics and systems still broke down often, due to the electromechanical nature of the devices used. We still use relays today but only to isolate and control loads. They are not as part of the control. If a relay operation takes 15 milliseconds and there are 10 stages in the control circuit where one relay drives another, the propagation of the signal might be greater than 150 milliseconds. This is inadequate for many applications today. Figure 3 Early transistor circuits in computers With the invention and introduction of electronic devices, some relay control systems were replaced by dedicated digital systems. These systems were able to respond more quickly and required less maintenance as the devices were solid state, an old fashioned term meaning that they had no moving parts. They were essentially still hard-wired though, and process modifications and fixes meant that part of the system had to be re-designed and re-wired. It was not until the arrival of the microprocessor, that programmable control was made possible. Figure Type relays used for control Page 17 of 188

8 Eventually the PLC was invented. It came about because of the needs of the automotive manufacturers who needed to make changes to designs and build new models. PLCs became popular for control and are still currently the most common solution used by control engineers and electricians. They grew in size and power until their complexity made them too slow for some applications. It is now more common to use several small PLCs that communicate with each other than one very large PLC with a lot of processing power. Activity box A In what year was the very first PLC designed? 2. Why is it that PLC programs have a ladder like layout rather than being written in a normal programming language? Using the Internet links below, complete the following activities and respond in the space provided Figure 4 A shoebox PLC 3. List four well known PLC manufacturers. Page 18 of 188

9 Microprocessor Control There are a number of choices in regard to a control system solution. The decision to utilise a specific type of controller and control system architecture is often based on the number of inputs and outputs required and the complexity of the control algorithms and therefore the processing power required to do the calculations. Other considerations might be the development time available, the lifecycle of the project, the likelihood of process changes and limits on the cost of system implementation. Some of the choices are; Figure 5 Embedded System An embedded system (a dedicated system) such as is used for TV remote controls, simple alarm systems and pool chlorination systems. In such systems, a microprocessor or microcontroller executes a program that is stored as firmware in EPROM memory. Costs for these systems are very low because of mass production. If large production numbers are not required, this sort of system is often not viable. A single PLC, or a number of PLCs, (a programmable system) where changes are easily made and the costs of both equipment and development time are relatively low. These systems are capable of some analogue measurement but only in a limited way. If a large number of analogue channels are required or very high sample rates, then other solutions might be more effective. A third option is to use what is popularly called a single board computer. This is something that has a PC operating system but is a limited configuration in terms of computing power, memory and communications capabilities. The benefits of a single board computer are that its power consumption is low and physically, it can be incorporated in pieces of equipment. Flash memory is used instead of a hard drive. Graphics processors are limited compared with a normal PC and the processor is a low power (slower) version of standard CPU. Even today, it is often a Pentium 4, not dual core PC architecture. Software can be developed easily as it is still essentially a PC platform. Figure 6 PLCs with SCADA control Figure 7 Single Board Computer with onboard graphics, Ethernet, expansion bus and USB ports Page 19 of 188

10 Ever since the advent of the personal computer, a PC based control system has been an option. The processing power available in such a system makes it perfect for complex measurement, analysis and advanced control systems. The use of a PC along with data acquisition hardware, is common in scientific circles. It is less commonly used in industry because of the relatively high cost. As industrial process control becomes more sophisticated and the price of PC technology continues to fall, this is becoming less of a constraint. This type of control is the focus of this unit of competency. Activity box A1.2 Figure 8 Two computers from different generations Try to guess what year each of the two computers above is from. The first is a relatively early PC. You will notice the two floppy drives. There was no hard drive. Each time you booted the PC you had to load the operating system from a floppy disk. The second PC is fairly recent. The flat LCD monitor places it within the last five years. Write your responses to the right. PC 1 PC 2 Technology Change 1. Why answer questions about historically irrelevant technology? Simply to bring into focus the fact that technology will not stop changing. The control solutions that are common today may not meet the needs of tomorrow s industry. Page 20 of 188