Control Engineering Major 2-Automation Section, …eleceng.dit.ie/jmcgrory/dt021_Y4_ControlEngineeringV1_CONT4601... · module on control engineering. ... Control Engineering Major

Control Engineering Major 2-Automation Section, DT021, First Semester

© Dr J.McGrory & Mr David Berber as exerted in Copyright and Related Rights Acts 2000 and 2004. Page 1 of 48 File Ref: dt021_ControlEngineeringVersion1_CONT4602

Bachelor of Engineering (Honours) Degree in

Electrical/Electronic Engineering

School of Electrical Engineering Systems

Dublin Institute of Technology

Kevin Street

Dublin 8

Control Engineering Major 2 Module

Automation Section

DT021 Year 4, First Semester

Version 1.0

Optimist: "The glass is half full."

Pessimist: "The glass is half empty." Engineer: "That glass is twice as large as it needs to be."

Prepared by: Dr. John McGrory & Mr David Berber School of Control Systems and Electrical Engineering,

Dublin Institute of Technology,

Kevin Street,

Dublin 8.



Notes from the authors.

It is important to emphasise that this module is an integral part of all the others

modules given this year. It should not be viewed in isolation, but in parallel, in the

context of the material covered in other lectures and laboratories. The authors

exonerate themselves from liability in regard to the use of concepts and ideas

discussed in this course. Since the ideas and concepts given are as illustration

examples and include where possible all obvious issues involved, but not all factors.

However, more investigation is needed to ensure any idea is plausible on a case by

case basis.

A semester module is 15 weeks long and includes one week revision and two weeks for

exams. This calculates to 12 weeks for new material to be presented. Assuming this

course disseminated using one lecture and one (averaged) laboratory hours per week,

this means that there are only 24 contact hours (not including your private study

time for this subject). Therefore, onus is on you from the beginning to perform to

the best of your ability. Remember, woulda coulda shoulda are the last words of a

fool.

So keep up to date with all the material and don’t slip behind, and the best of luck in

getting on with it.

John & David.



Table of Contents

NOTES FROM THE AUTHORS. ...............................................................................................................................2

OBJECTIVES OF THIS COURSE:...........................................................................................................................5

MODULE DESCRIPTION: ................................................................................................................................................5

MODULE AIM:.................................................................................................................................................................5

LEARNING OUTCOMES:..................................................................................................................................................5

LEARNING AND TEACHING METHODS:.........................................................................................................................5

MODULE CONTENT: ........................................................................................................................................................6

MODULE ASSESSMENT..................................................................................................................................................6

CHAPTER 1, DESIGN FILE BASICS AND DOCUMENT REQUIREMENTS ...............................................8

INTRODUCTION .............................................................................................................................................................8

CHANGES TO THE FORM-FIT-FUNCTION (FFF)..........................................................................................................9

CHAPTER 2, LABORATORY 1, PROPORTIONAL-CONTROL AND MANUAL RESET...........................11

INTRODUCTION ...........................................................................................................................................................11

AIM:..............................................................................................................................................................................11

OBJECTIVE: ..................................................................................................................................................................11

CONTROL PHILOSOPHY: ...............................................................................................................................................11

CHAPTER 3, LABORATORY 2, PROPORTIONAL-CONTROL, MANUAL RESET & ALARMS .............13

AIM:..............................................................................................................................................................................13

OBJECTIVE: ..................................................................................................................................................................13


CHAPTER 4, WHAT IS THE STANDARD FOR PROGRAMMING PLC’S....................................................14

INTRODUCTION ...........................................................................................................................................................14

WHAT IS IEC 61131? .................................................................................................................................................14

IEC 61131 LADDER DIAGRAM .....................................................................................................................................15

IEC 61131 SEQUENTIAL FUNCTION CHARTS ...........................................................................................................15

IEC 61131 FUNCTION BLOCK DIAGRAM OVERVIEW .................................................................................................18

IEC 61131 STRUCTURED TEXT OVERVIEW................................................................................................................18

IEC 61131 INSTRUCTION LIST OVERVIEW ..............................................................................................................22

SFC PROGRAM EDITING PROCEDURE OUTLINE, FOR FX PLC ...................................................................................23

CHAPTER 5, LABORATORY 2, CONTROLLING SEQUENCES ©DAVIDBERBER....................................25

AIM:..............................................................................................................................................................................25

OBJECTIVE: ..................................................................................................................................................................25

SYSTEM DESCRIPTION: ...............................................................................................................................................25

INPUT / OUTPUT LIST:................................................................................................................................................25

SYSTEM SCHEMATIC ...................................................................................................................................................26


PROGRAMMING EXERCISE: ..........................................................................................................................................27

CHAPTER 6, LABORATORY 3, SEQUENCE CONTROL OF AN AUTOMATIC PALLETISING

MACHINE ©DAVIDBERBER .....................................................................................................................................29

AIM:..............................................................................................................................................................................29



OBJECTIVE: ..................................................................................................................................................................29




SYSTEM OPERATION:...................................................................................................................................................31


CHAPTER 7, LABORATORY 4, SEQUENCE CONTROL OF A BOTTLE CAPPING AND LABELLING

MACHINE ©DAVIDBERBER .....................................................................................................................................33

AIM:..............................................................................................................................................................................33

OBJECTIVE: ..................................................................................................................................................................33




SYSTEM OPERATION:...................................................................................................................................................36


CHAPTER 8, HUMAN MACHINE INTERFACE (HMI).....................................................................................38

INTRODUCTION ...........................................................................................................................................................38

HOW THE BRAIN PROCESSES IMAGES .......................................................................................................................38

1. Attention Phase.............................................................................................................................................38

2. Filter and Focus Phase.............................................................................................................................39

3. Identification Phase.................................................................................................................................40

HOW THE EYES SCAN AND BRAIN INTERPRETS..........................................................................................................42

CHAPTER 9, HIGH SPEED CONTROL..................................................................................................................47

INTRODUCTION ...........................................................................................................................................................47



Objectives of this course:

Module Description: This module is composed of two portions: Control Engineering and Automation. This

document only focuses on the Automation aspect of the module. The Automation

portion of the module builds on the work done in the Control Engineering Major

module (Year 3, Semester 1). On completion of this module, the learner will implement

control of analogue, high speed and complex sequential processes. On this half module

24 contact hours are devoted to Automation and complements the other half of the

module on control engineering.

Module aim: The aim of the Automation portion of the module is to enable the students to

implement safe control on real and complex industrial processes using automation

computers.

Learning Outcomes: Automation (1) Design and implement a sequence control system of an automated industrial

process with fault finding exercises to demonstrate the ability to problem solve

in a real manufacturing environment. Control complex sequential processes.

(2) Carry out faultfinding techniques of complex sequential processes.

(3) Develop a safety-conscious mindset in all control solutions.

(4) Implement Analogue control algorithms on industrial processes.

(5) Understand the complexity of high speed control and Implement control of a

high speed process.

Learning and Teaching Methods: This course development is based on the cognitivists theory of education, one of the

main exponents of this theory, Bruner sees the teaching role as one of facilitating

the student's own discovery, known as 'enquiry training.' Bruner was insistent that

students must be taught how to analyse problems and how to think for themselves, to

become independent learners. The learning process is the acquiring of new knowledge

and information and transforming that learning with their existing knowledge and

utilising it in a new situation. Knowledge is a process rather than a product. The

cognitivists theory is of the active engagement of the mind in relation to the subject

matter. In order to learn, understanding is necessary; the setting of tasks related to

new material and feedback is an essential element in the process of learning.

The key points to the structure of this course are:



• Utilise the structure of the subject, stressing the relationships in

what material is presented, encourage students to seek solutions of

their own.

• Arrange the structure so the students discover things themselves.

• Utilise and take advantage of students wanting to find answers to

problems that have personal significance to them, this relates the

learning to their own personal situation or task.

• Facilitate discussions by posing specific relevant questions.

• Allow the students to take a significant role and responsibility in

leading the discussions.

In summary the important point to note is that students learn best when they

discover concepts and principles for themselves. The objective of this course is to

facilitate that process.

Module content: • Introduction to IEC 61131-3 Simple Sequence and Step Ladder

programming.

• Sequence control of Series and Parallel and multi loop tasks.

• Mini Project involving Sequence control of a sequential process.

• Analogue to digital and Digital To Analogue control.

• Analogue control On/Off and Proportional Control PID and Self

tuning control.

• Application of HMI’s to Automated systems.

• Mini Project utilising analogue modules to interface to and control

industrial process, monitoring using a high level human machine

interface.

• Fault finding of computer controlled processes.

Module Assessment This half module is designed to have a clear alignment between the learning outcomes

and the assessment method chosen. The course implements a student centred

teaching approach and to give the student confidence to apply the knowledge they

have gained by their own endeavours, working as individuals and as part of a group.

The students will be presented with carefully designed mini projects, which they will

undertake to come up with solutions to solve automation and control problems to

achieve the goals and objectives of the project.

The projects will be related to the real industrial problems that they can relate to,

and in the process of solving the problems, they will gain confidence and enjoyment

from applying their new knowledge through practical means and see the results.



The assessment will be on the project based learning exercises with formative /

continuous assessment being carried out at regular review and design meetings, as

well as using a creative Design File approach (also known as reflective diary or web

based Blog) to allow course participants to document and reflect upon their learning

process. The appropriate assessment method with the correct choice of projects will

lead to good alignment between the learning outcomes and the assessment method

where the ‘assessment will drive the learning’.

The project based learning exercises will also incorporate a task of self learning that

the students may choose from a choice of several relevant topics, which should be of

interest to their future chosen career. (This subject is their chosen Major option)

The designed attached marking scheme reflects the effort and abilities of the

students. The overall break down of the marks is: 70% for Continuous/Formative

assessment and 30% for the reflective writing, portfolio and self assessment. This is

a fourth-year course at NQAI level 8, the formative/continuous assessment is

required to drive the learning. The major concern is that without regularly

assessment and provided feedback the weaker students may not be driven to

complete the prescribed projects. The regular continuous/formative assessments will

provide the learners a plan of work with clear milestone objectives. This will enable

and make it easier to check the learner’s progress at their regular design and

continuous/formative assessment meetings. The reflective diary / Blog will be used as

a diary of the learners’ progress and should map the learners learning achievements

throughout the course of the project task.

The learner will document the following:

• Self Assessment of produced work and role within an informal group

(if any)

• How far did I get with respect to solving the problems

• How much did I interact with my peers to give assistance and

contribute to development ideas?

• To document new knowledge, ideas and concepts

• What have I learnt?

• What I am unclear or unsure about

• What I do not understand

• What I will do next to achieve my stated goals

• What questions I asked my peers or lecture

• What questions I answered my peers and tutor

• Self Assessment and role within an informal group (if any)



Chapter 1, Design File basics and document requirements Introduction

Each laboratory will require a Design File (also known as the reflective diary/blog) to

be produced, which will be used guide and act as an indicator of the learners’ progress

during the laboratory and should map the learners learning achievements throughout

the course of the project task. The learner will document the following:

• Self Assessment of produced work and role within an informal group

(if any).

• How far did I get with respect to solving the problems.

• How much did I interact with my peers to give assistance and

contribute to development ideas?

• To document new knowledge, ideas and concepts.

• What have I learnt?

• What I am unclear or unsure about.

• What I do not understand.

• What I will do next to achieve my stated goals.

• What questions I asked my peers or lecturer.

• What questions I answered for my peers and tutor.

• Self Assessment and role within an informal group (if any).

At the end of the laboratory session the learner must save and submit their files for

marking and be made available to the external examiners. Please save your PLC

program (make sure to zip the resource folder and all its contents) in a folder

DT021_4_YR201?_Lab??_Surname_FirstName. Place within the root of that

directory your design file as an MSWord document (or PDF) using the following title

DT021_4_YR201?_Lab??_DF_Surname_FirstName.doc. Then zip the entire folder

and contents into a single zipped file titled

DT021_4_YR201?_Lab??_Surname_FirstName.zip submit it using web courses on or

before the specific date and time.

Every student must have an electronic copy of the following Mitsubishi documents:

FX PLC Programming Manual, this contains all the available commands and a lot of

other information.

• FX PLC 4AD Manual, Analogue to Digital converter with all the wiring and

buffer location details.

• FX PLC 4DA Manual, Analogue to Digital converter with all the wiring and

buffer location details.

• FX PLC SFC Programming Manual, a specialist document to illustrate the

Mitsubishi SFC



As we as a group progress through the course this design file structure will be

revisited and techniques on how to share information through documentation, make it

easier to scan and identify key issues will be shown.

Changes to the Form-Fit-Function (FFF). These are the generic terms where:

• “Form” relates to the structure which is a perceptual structure. It could be an

animal body, music composition, house, apartments or instruments, recognisable

entity etc.

• “Fit” relates to be the right size or shape; fit correctly or as desired, but

could also suitability where it would be agreeable or acceptable, or provide

something usually for a specific purpose etc.

• “Function” relates to a mathematical relationship of one thing is dependent on

another, what something is used for, routine set of sequences, the actions and

activities assigned to or required or expected etc.

By nesting and grouping the entries it is possible to see how the end product was

developed, how long each part took to complete, understand the students

interpretation of Form Fit and Function and who was responsible for the task.

Table of contents 1 Mechanical Aspects

2 Control Aspects

3 Power Aspects

3.1 Power, Battery life Elongation.

3.2 Power, Power distribution to wheel drives unbalanced.

4 Management Aspects

Issue Title 1.3.1, Power, Battery, Elongation

FFF Change Form Fit X Function

Date/Time 17th

November 2010 / 15.30, 4 hours

People responsible JMG

Description of Issue Battery for robot is discharging too quickly, resulting in premature motor

power failure.

Resolution JMG developed a regulating circuit with help from DB which uses Capacitor and

inductor to restrict the flow of current……the student can amend to the end of

the document more information about the resolution, keeping the design file

quick and easy to search.



Table of contents 1 Mechanical Aspects 2 Control Aspects

3 Power Aspects

3.1 Power, Battery life Elongation.

3.2 Power, Power distribution to wheel drives unbalanced.

4 Management Aspects

When I was the manager of a project I would keep an eye on the entries and see which group was doing the majority of the work and who is not.

Issue Title 3.1, Power, Battery, Elongation


Date/Time 17th

November 2010 / 15.30, 4 hours

People responsible JMG

Description of Issue Battery for robot is discharging too quickly, resulting in premature motor

power failure.

Resolution JMG developed a regulating circuit with help from DB which uses Capacitor and

inductor to restrict the flow of current……the student can amend to the end of

the document more information about the resolution, keeping the core design

file information quick and easy to search.

Issue Title 3.2, Power, Power distribution to wheel drives unbalanced


Date/Time 19th

November 2010 / 15.30, 0.45 hours

People responsible TB

Description of Issue The left drive motor is rotating 1.2 times the speed of the right drive motor and

so the robot is travelling to the right.

Resolution TB checked the voltage and taco speed and identified a weakness in the cable

connection of the drive. The connections were remade and the problem was

resolved



Chapter 2, Laboratory 1, Proportional-Control and Manual Reset Introduction The purpose of this laboratory is to identify weaknesses in the students

understanding and competency of industrial computers and slowly ease them back into

the mode of self directed learning.

Aim: This laboratory focuses on the use of P-control (proportional control) in PLC

ladder logic and the inclusion of the manual reset component.

Objective: (1) A PLC is an industrial computer and so is not identical to the academic

software used elsewhere to show proofs of academic concepts. The pupil

must demonstrate how to clamp signals, to ensure the process remains safe

at all times if the control variable wanders in an industrial application.

(2) The pupil should correlate the process of the PLC to a control diagram.

Ensure to use SUB for a comparator and MUL when passing through

Transfer Functions.

(3) The student must use the double compare (DCMP) function.

(4) The pupil should be able to ask questions to clarify the requirements where

ambiguity exists in the control philosophy text.

Control Philosophy: Using the analogue to digital rig’s in Room KEG012. Configure the A/D card so channel

1 is set to 0-10vDC. Setup a selectable access to the averaged and actual A/D buffer

location for channel 1 using the input X1. Deposit the channel 1 value (either averaged

or actual) into D200 in the PLC’s memory. The averaged sample amount should be set

at 50.

The output of channel 1 of the D/A card should be configured. When the input drops

below 0 volts or 0, the output should be clamped to 0. When the input goes above 5

volts or 1000 the output should be clamped to 1000.

When the input is between 0 and 1000 the output should be proportional to the input.

Only when the above is complete continue to add in the manual reset aspect. If there

is an error signal that is large or exists for a long period of time it can cause the

control element reach its “fully open” or “fully closed” position before the error is

reduced to zero. If this occurs the final control element remains at the extreme and

the error must be reduced by means of a manual reset. Program this manual reset

component into your existing application.



Ensure to use the following variables and declare them at the beginning of the

program:

D200 = Tank Level (PV)

D1 = Desired Level (SP)

D2 = Error

P Gain Term K (D10)

U Controller Output (D3)

KxE Term (D12)

b Manual Reset (D20)



0vdc = 0

10vdc = 2048

7vdc = 1500

Alarm

8vdc = 1700High High Alarm

High Alarm or Warning

0vdc = 0

10vdc = 2048

7vdc = 1500

Alarm

8vdc = 1700High High Alarm

High Alarm or Warning

Chapter 3, Laboratory 2, Proportional-Control, Manual Reset &

Alarms Aim:

This laboratory expands on the P_Control of lab1 and focuses on the use of

alarms and alarm acknowledgements in PLC ladder logic.

Objective: (1) It is important to ensure the PLC program cannot circumvent the notice of

an alarm and that two alarm states can exist ((1)high and (2) high high, or

(1) low or (2) low low could also be used).

(2) The use of a [PLS ???] instruction means that the reset button cannot be

held in through the use of a piece of paper or sticky tape. The transition of

the state is therefore used.

(3) Important to highlight this program must be correctly documented,

commented and prepared in a professional manner. So marks are allocated

to this commenting activity. So the student must document the system as

they go using MSWord as their design file.

(4) The pupil should be able to ask questions to clarify the requirements where

ambiguity exists in the control philosophy text.

Control Philosophy: Using the analogue to digital rig’s in Room KEG012.

Configure the A/D card so channel 1 is set to 0-10vDC.

Setup a selectable access to the averaged and actual

A/D buffer location for channel 1 using the input X1.

Deposit the channel 1 value (either averaged or actual)

into D200 in the PLC’s memory. The averaged sample

amount should be set at 50.

When the channel 1 input goes higher than or equal to 1500 or ~7.5 vDC, initiate a

high alarm light (Y2 for this example) and have the output flash on/off at one second

intervals. If the alarm acknowledge X2 is pressed the high level alarm should be

reset.

When the channel 1 input goes higher than or equal to 1700 or ~9 vDC, initiate a high

high alarm light (Y1 for this example) and have the output flash on/off at one second

intervals. If the alarm acknowledge X2 is pressed the high high level alarm should

only reset if the level is below the 1500 or ~7.5 vDC value.

Remember to comply with the submission requirements (i.e. naming and zipping

protocol) as detailed in Chapter 1, Design File basics and document requirements.



Chapter 4, What is the standard for programming PLC’s Introduction PLC’s were developed in the 1960’s by GM to provide a flexible way to produce cars,

with an ever changing specification. Remember 1971 was the year of the first

commercial processor (x086) by Intel, so this is pre-off-the-shelf-microcontrollers.

So the system had an input interface, output interface an I/O table, a way of

constructing logic instructions and an operating system, that makes it act as a PLC

(Industrial Computer). The aim was to make the program logic similar to that already

used by electricians, so the user interface was developed to match standard wiring

diagram formats. There were no fancy graphics back then and only instructions using

standard keyboard type arrangements were used see example below. But things have

progressed and now PLC logic is now programmable in many different ways to allow,

scientists, engineers, chemists etc effectively compile operational logic without using

wiring diagram type formats. So the original approach has changed to match the

needs hence the need to introduce the IEC 61131 standard. It was called IEC 1131

when it was a pre-standard.

What is IEC 61131? Developed with the input of vendors, end-users and academics, IEC 61131 consists of

five parts:

1. General information

2. Equipment and test requirements

3. PLC programming languages

I/O Table

Address Status

X7

X6

X3

X5

Y1

0

1

0

0

0

Input Interface

Output Interface

Operating

System (OS)

IEC 1131 Part 3 focuses only on

the PLC programming

languages

I/O Table

Address Status

X7

X6

X3

X5

Y1

0

1

0

0

0

Input Interface

Output Interface

Operating

System (OS)

I/O Table

Address Status

X7

X6

X3

X5

Y1

0

1

0

0

0

I/O Table

Address Status

X7

X6

X3

X5

Y1

0

1

0

0

0

Input Interface

Output Interface

Operating

System (OS)

IEC 1131 Part 3 focuses only on

the PLC programming

languages



4. User guidelines

5. Communications

IEC 61131-3 is the international standard for programmable controller programming

languages. As such, it specifies the syntax, semantics and display for the following

suite of PLC programming languages:

• Ladder diagram (LD)

• Sequential Function Charts (SFC)

• Function Block Diagram (FBD)

• Structured Text (ST)

• Instruction List (IL)

One of the primary benefits of the standard is that it allows multiple languages to be

used within the same programmable controller. This allows the program developer to

select the language best suited to each particular task. An analogy is that a mechanic

wouldn't attempt to repair an automobile using only a screwdriver. The mechanic has

a variety of tools available and chooses the best one for each task. Follow the above

links for a description of each of the IEC 61131-3 languages and the types of

applications they are best suited to.

IEC 61131 Ladder Diagram

For people who understand relay controls, LD continues to be an advantage in terms of usability.

Although it is possible to program all control logic in LD, supplementing LD with other languages allows

users access to the language best suited for a particular control task. The standard's implementation

of LD appears below.

IEC 61131 Sequential Function Charts SFC programming offers a graphical method of organizing the program. SFC is one of the methods

that can be used for programming the A series and QCPU (Q mode)/QnA series and FX series CPUs



and it stands for Sequential Function Chart. The three main components of an SFC are steps, actions

and transitions. Steps are merely chunks of logic, i.e., a unit of programming logic that accomplishes a

particular control task. Actions are the individual aspects of that task. Transitions are the mechanisms

used to move from one task to another. Control logic for each Step, Action and Transition is

programmed in one of the other languages such as Ladder Diagram or Structured Text.

As a graphical language, SFC programming offers you several choices for executing a program, each

depicted in a visually distinct way (Fig. 1). In a sequential configuration, the processor simply executes

the actions in step 1 repeatedly, until the transition logic becomes true. The processor then proceeds

to step 2. In a selection branch, only one branch is executed depending on which transition is active. In

a simultaneous branch, all branches are executed until the transition becomes active. In addition to

various types of branches, the operation of individual actions within a step can be varied with the use

of action qualifiers.

SFC Selection Branch

FIGURE 1

Action qualifiers (Fig. 2) determine how the action is scanned and allow actions to be controlled

without additional logic. For example, one could use the L qualifier to limit the time that ingredient

valve B is opened.

SFC Simultaneous Branch

FIGURE 2



In practice, an active step is highlighted to signal to the programmer which part of the program is

executing - a useful feature for troubleshooting. This highlighting is an example of the standard's

extensibility - the ability of a vendor to add a feature not specified in the standard.

Note that the standard offers SFC programming as an organizing tool. The user chooses whether to

use it or not, based on whether the process being controlled is sequential in nature. And even if SFC

programming is used, the actions will be written in one of the four programming languages described

below. Figure 3 shows a sample net weight calculation as it would be performed in each of these

languages. In each example, net weight is calculated by subtracting tare weight from the gross weight.

SFC Sequential configuration

FIGURE 3

SFC Action Qualifiers



SFC

Qualifyer Description

N Nonstored. Terminate when the step becomes inactive.

S Set (stored). Continue after the step is deactivated, until the action is reset.

R Reset. Terminate the execution of an action previously started with the S, SD, SL, or DS qualifier.

L Time Limited. Start when step becomes active and continue until the step goes inactive or a set time

passes.

D Time Delayed. Start a delay timer when the step becomes active. If the step is still active after the

time delay, the action starts and continues until deactivated.

P Pulse. Start when the step becomes Active/Deactive and execute the action only once.

SD Stored and time Delayed Action starts after time delay, continues until reset.

DS Delayed & Stored. If step is still active, action starts after time delay, continues until reset.

SL Stored & timeLimited. Action starts when step becomes active, continues for a set time or until

reset.

IEC 61131 Function Block Diagram Overview Like SFC, FBD is a graphical language that allows programming in other languages (ladder, instruction

list, or structured text) to be nested within the FBD. In FBD, program elements appear as blocks

which are "wired" together in a manner resembling a circuit diagram. FBD is most useful in those

applications involving a high degree of information/data flow between control components, such as

process control.

IEC 61131 Structured Text Overview This high-level language resembles Pascal or Basic, and, in fact, people trained in computer

programming languages often find it the easiest language to use for programming control logic. When

symbolic addressing is used, ST programs resemble sentences, making it highly intelligible to the



novice user as well. ST is ideal for tasks requiring complex math, algorithms or decision-making. Its

concise format allows a large algorighm to be displayed on a single page (vs multiple pages of ladder

logic).

The IEC 61131-3 standard is extensible. I.E. Vendors may augment their offerings to meet the needs

of specific markets. As an example of this extensibility Rockwell Software augments ST with an

exclusive feature called "PowerText™". It supplements standard ST with real-time display of discrete

status, force status, analog values and floating-point values. This PowerText information is

automatically integrated into the source code, and is invaluable for debugging and application

commissioning.

Benefits of Structured Text

• People trained in computer languages can easily program control logic

• Symbols make the programs easy to understand

• PowerText facilitates system debugging and application commissioning

• Programs can be created in any text editor

• Runs as fast as ladder logic

Structured Text Constructs

• Bit / Word assignment

• IF-THEN-ELSE

• CASE

• FOR-NEXT

• WHILE

• REPEAT

• Ladder equivalent instructions

Structured Text Examples

Example 1 (Sorting machine)

IF (LIMIT_SWITCH_1 AND BOX_PRESENT) THEN

GATE1 := OPEN;

GATE2 := CLOSE;

ELSIF ((LIMIT_SWITCH_2 OR (WEIGHT <> SETPOINT))) THEN



GATE1 := CLOSE;

GATE2 := OPEN;

ELSIF (LIMIT_SWITCH_3 XOR LIMIT_SWITCH_4) THEN

GATE1 := OPEN;

GATE2 := OPEN;

ELSE

GATE1 := CLOSE;

GATE2 := CLOSE;

END_IF;

Example 2 (Split-range temperature control, with deadband)

CASE (TEMPERATURE) OF

0 .. 120 :

HEAT_VALVE := OPEN;

COOL_VALVE := CLOSE;

150 .. 32767 :

HEAT_VALVE := CLOSE;


ELSE

HEAT_VALVE := CLOSE;


END_CASE;

PID (CONTROL_BLOCK, TANK_#27_TEMPERATURE, TIEBACK, COOLANT_VALVE);

Example 3 (Computational examples)

POWER := (CURRENT ** 2.0) * RESISTANCE;

F8:1 := ((N7:1 * 3.1428571) + (N7:3 / N7:4));

F8:0 := ( SIN (ANGLE)) MOD 6.0;

JSR (3, 0);

Example 4 (If-Then-Else example)

IF I:000/0 AND !I:001/5 THEN

N7:0 := 1;

ELSIF i:000/2 OR (N7:5 <> (N7:6 * N7:2)) THEN

N7:0 :=2;

ELSIF !I001/4 THEN

N7:0 := 3;



ELSE

N7:0 :=4;

END_IF;

Example 5 (For-Next examples)

FOR N7:0 := 10 TO 0 BY -1 DO

N7:4 := N7:4 + 1;

END_FOR;

FOR N7:1 := 0 TO 10 DO

N7:1 := N7:1 + 1;

END_FOR;

Example 6 (While example)

WHILE I:000/0 AND (I:001/0 OR !I:002/1) DO

N7:0 := N7:0 + 1;

END_WHILE;

Example 7 (Case example)

CASE N7:12 OF

0:

N7:1 := 1;

1, 9:

N7:1 := 2;

2..4:

N7:1 := 3;

10, 5..8:

N7:1 := 4;

ELSE

N7:1 :=5;

END_CASE;

Example 8 (Using Ladder Diagram instructions in Structured Text programs)

IF (!I:000/00) THEN

ARL(0, ST15:3, R6:6, 82,0);

END_IF;

R6:6.DN AND ONS(B3/4) MOV(ST15:3.LEN, N17:85);



IEC 61131 Instruction List Overview This low-level language is similar to Assembly language and is useful in cases where small functions are

repeated often. Although it is powerful, it is considered to be difficult to learn.

Instruction List example (Calculate new weight by subtracting tare weight from net weight)

LD weigh_command

JMPC WEIGH_NOW

ST ENO

RET

WEIGH_NOW: LD gross_weight

SUB tare_weight



SFC Program Editing Procedure Outline, for FX PLC



The programming code should be divided into at least three phases, Pre-Processing,

SFC (i.e. which is the main applications) and Post Processing states.



Chapter 5, Laboratory 2, Controlling Sequences ©DavidBerber Aim:

Sequence control of a 0.75 l and 1.5 l bottle labelling machine, thus control of a

parallel sequence. This laboratory explores the use of sequence flow diagrams

but focuses on the parallel decision branch aspect.

Objective: (1) Develop using an example an understanding of “What is a sequence”?

(2) How do we control a sequence (i.e. design the system, enter it into the

software, document it, parallel sequence, multiple loops etc)?

(3) How do we fault find.

(4) What are the advantages of IEC 61131-Part 3 for controlling sequences

(declare in your design file your list)

(5) What are the components of IEC 61131-part 3

System description:

The system consists of a Mitsubishi FX1S 20 PLC, three pneumatic actuators and

electro pneumatic interfaces to the PLC. The object of the system is to label

correctly 0.75 litre and 1.5 litre bottles. The bottles are detected by the Blue push

button and the size is determined by the position of the X13 selector switch (X13 Off

=0.75 l and X13 On = 1.5L).

The following information describes the PLC Input's and Outputs, system schematic

and required programming exercises.

Input / Output list: Input List

I/O PLC Name Comment

X0 A-FB .75L LAB BACK FB

X1 A+FB .75L LAB ON FB

X2 B-FB BOTTLE OUT F/B

X3 B+FB BOTTLE IN F/B

X4 C-FB 1.5L LAB BACK FB

X5 C+FB 1.5L LAB ON FB

X6 START NOT USED

X7 NSTOP NOT USED

X10 NESTOP NE STOP

X11 BLUE PB BOTTLE DETECT

X12 SPARE

X13 BOTTLE SIZE Sel X13=0=.75L and X13=1= 1.5L

Output List




Y0 A+OP .75 L LAB ON OP

Y1 B+OP BOTTLE IN OP

Y2 C+OP 1.5 L LAB ON OP

Y3 AIR ENABLE SOLINOID AIR ON

Y4 RED LAMP RED LAMP

Y5 BLUE LAMP BLUE LAMP

Y6 GREEN LAMP GREEN LAMP

Internal Relay I/O PLC Name Internal Relay 0.75l & 1.5l Label Name

M8000 ON IN RUN ON IN RUN

M8002 1 PULSE RUN 1 PULSE RUN

M8013 1SEC PULSE 1SEC PULSE

I/O PLC Name Internal Relay 0.75l & 1.5l Label Name




I/O PLC Name Control States 0.75l & 1.5l Label Name

S0 INITIAL STATE INITIAL STATE

S10 BOTTLE IN STATE BOTTLE IN STATE

S11 .75 L LAB ON STATE .75L LAB ON STATE

S12 .75 LAB BACK STATE .75L LAB BACK STATE

S13 1.5L LAB ON STATE 1.5L LAB ON STATE

S14 1.5L LAB BACK STATE 1.5L LAB BACK STATE

S15 BOT OUT STATE BOT OUT STATE

System Schematic

A- A+

0.75 l label

applicator

A-FB A+FB

C- C+

1.5 l label

applicator

C-FB C+FB

Bottle Push in and Pull out Piston

B+

B-

B+FB

B-FB

Bottle

0.75 l and 1.5 l Labelling machine schematic

Figure 1



Control Philosophy: Piston A is the 0.75 litre label applicator piston, Piston B is the Bottle push in and

pulls out of the label machine piston and Piston C is the 1.5 litre label applicator

piston.

Initially the system should start with A-, B- and C- and if the machine is correctly

initialised to accept a bottle the Green indicator lamp should illuminate. If the

machine is not correctly initialised it should not start and the operator should

manually initialise the machine.

When all the initial conditions are true and a bottle detection signal is received, the

PLC operates Piston B in the B+ direction until the signal B+FB activates, this puts the

bottle into the labelling machine. The PLC will detect if the bottle is a 0.75 l or 1.5 l

bottle. If the bottle is a 0.75 l bottle then the next step is to operate Piston A is in

the A+ direction until the signal A+FB activates, this allows the 0.75 l labeller to

apply the correct label to the bottle. Then the 0.75 l labeller is withdrawn from the

bottle by operating Piston A is in the A- direction until the signal A-FB activates. The

bottle should now be withdrawn form the labelling machine. This is carried out by

Piston B in the B- direction until the signal B-FB activates; this pulls the bottle out of

the labelling machine.

If the bottle is a 1.5l bottle then the next step is to operate Piston C is in the C+

direction until the signal C+FB activates, this allows the 1.5 l labeller to apply the

correct label to the bottle. Then the 1.5 l labeller is withdrawn from the bottle by

operating Piston C is in the C- direction until the signal C-FB activates. The bottle

should now be withdrawn from the labelling machine. This is carried out by Piston B in

the B- direction until the signal B-FB activates; this pulls the bottle out of the

labelling machine.

The machine is now ready to accept the next bottle for labelling. The Selector switch

X13 will inform the PLC to the size of the bottle X13 input OFF is a 0.75 l bottle and

X13 input ON is a 1.5 l bottle.

Programming Exercise: 1. Draw a fully labelled Sequence Function Chart for the required operation

incorporating the following features.

2. The Green Indicator lamp should illuminate when the process is at the initial

conditions and is ready to start. The green indicator should stay on during

normal operation.



3. If the Emergency Stop is pressed the machine should commence operation on

removal of the Emergency Stop at the initial condition. The Red indicator lamp

should flash while the Emergency Stop is activated.

4. Test and debug your program

5. Print out the final version of your program, make sure that the printout has

the relevant information. DO NOT PRINT until your printer settings have been

checked by staff in lab. Incorrect settings will result in lots of unwanted

pages.



Chapter 6, Laboratory 3, Sequence control of an automatic palletising

machine ©DavidBerber Aim:

This laboratory focuses on the challenges associated with sequencing key

activities of a process. An application with multiple loops is used to

demonstrate to the learner some of the complications that can occur.

Objective: (1) Enhance the understanding of “What is a sequence”?

(2) How do we control a sequence with multiple loops?

(3) Demonstrate a single increment step button, used for maintenance and

testing of the system.

(4) What are the advantages of IEC 61131-Part 3 for controlling sequences

(declare in your design file your list)

(5) Are their alternatives in doing multiple loops in SFC?

System description: The system consists of a Mitsubishi FX1S 20 PLC, three pneumatic actuators and

electro pneumatic interfaces to the PLC. The object of the system is to place 9 bags

of cement onto a palate in a required sequence.

The following information describes the PLC Input's and Outputs, system schematic

and required programming exercises.



X0 A-FB Piston A Reverse Feedback Limit switch Bag Drop Actuator

X1 A+FB Piston A Forward Feedback Limit switch Bag Drop Actuator

X2 B-FB Piston B Reverse Feedback Limit switch Bag Push Actuator

X3 B+FB Piston B Forward Feedback Limit switch Bag Push Actuator

X4 C-FB Piston C Reverse Feedback Limit switch Row Push Actuator

X5 C+FB Piston C Forward Feedback Limit switch Row Push Actuator

X6 START Start Push Button

X7 NSTOP Stop Push Button Normally Closed

X10 NESTOP Emergency Stop Push Button Normally Closed

X11 SINGLE STEP PB Single Step through the program



X12 Spare

X13 SINGLE STEP SELECT Single Step mode On = 1 , Off = 0

Output List I/O PLC Name Comment

Y0 A+OP Piston A Forward Output Bag Drop

Y1 B+OP Piston B Forward Output Row Push

Y2 C+OP Piston C Forward Output Bag Push

Y3 AIR ENABLE SOLINOID

Air Enable Solenoid

Y4 Red LAMP Red Indicator Lamp

Y5 Blue LAMP Blue Indicator Lamp

Y6 SINGLE STEP INDICATE Green LAMP

Green Single Step Indicator Lamp on Push Button

System Schematic

Figure 1



System operation: Piston A is the bag drop piston, Piston B is the Bag push piston and Piston C is the row

push piston.

Initially the system will start with the pistons in the following positions A+, B- and C-

and bag 1 is at the top of the cement supply chute.

On pressing the Start push button the PLC will initiate a 5 second warning period

(Flashing both the Green and Red Indicator Lamps) and after the warning period has

elapsed the system should initialise itself if required.

When all the initial conditions are true the PLC operates Piston A in the A- direction

until the signal A-FB activates this allows the bag to drop down the chute. The next

step is to operate Piston A is in the A+ direction until the signal A+FB activates, this

holds the next bag 2 in position. Bag 1 is now at the bottom of the chute and the PLC

operates Piston B in the B+ direction until the signal B+FB activates. The next step is

to operate Piston B is in the B- direction until the signal B-FB activates. The above

cycle is repeated three times. At the end of the third cycle bag 1, bag 2 and bag 3

are in front of pusher C.

The PLC activates Pusher C in the C+ direction to do a row push until C+FB activates

the PLC then turns on C-FB to retract the pusher until C-F is activated. The next

three bags are placed in front of pusher C as described previously and again pusher C

pushes them into the next row. This operation continues until the final pattern of

cement bags is achieved as shown in Figure 2.

Figure 2

Cement Bag 9

Cement Bag 8

Cement Bag 7

Cement Bag 6

Cement Bag 5

Cement Bag 4

Cement Bag 3

Cement Bag 2

Cement Bag 1



Programming Exercise:

1. Draw a fully labelled Sequence Function Chart for the required operation of

the automatic palletising machine incorporating the following features.

2. After pressing the start push button, a five second warning by flashing both

the Green and Red Indicator lamps should be given. After the 5 sec warning

the system should initialise itself and then commence operation.

3. Implement your program on the Mitsubishi PLC and incorporate a single step

button in the program which will hold each step until the single step button is

operated (Hint: PLS instruction).The switch X13 will enable the single step

mode when it is on. The Blue indicator lamp should illuminate to identify that

the machine is in the single step mode.



normal operation and flash when the cycle is paused with the Nstop push

button.



should flash while the Emergency Stop is activated. The Red lamp should be on

constantly on removal of the Emergency Stop and go out when the system is

restarted.

6. If Stop is pressed the machine should pause after completing the currently

active step. The operation continues from that point on pressing the start push

button.

7. Test and debug your program.

8. Print out the final version of your program; make sure that the printout has

the relevant information. DO NOT PRINT until your printer settings have been

checked by staff in lab. Incorrect settings will result in lots of unwanted

pages.



Chapter 7, Laboratory 4, Sequence control of a Bottle Capping and

labelling machine ©DavidBerber Aim:

This laboratory focuses on the challenges associated with sequencing key

activities of a process. An application with multiple loops is used to

demonstrate to the learner some of the complications that can occur.

Objective: (1) Enhance the understanding of “What is a sequence”?

(2) How do we control a sequence with multiple loops?

(3) Demonstrate a single increment step button, used for maintenance and

testing of the system.

(4) What additional advantages of IEC 61131-Part 3 for controlling sequences

have you found (declare in your design file your list).

(5) Are their alternatives in doing multiple loops in SFC?

System description: The system consists of a Mitsubishi FX1S 20 PLC, three pneumatic actuators and

electro pneumatic interfaces to the PLC. The object of the system is to cap and label

bottles. The bottles are detected by the Green push button. The Capping and

labelling process will happen at the same time i.e. a parallel operation. The following

information describes the PLC Input's and Outputs, system schematic and required

programming exercises.



X0 A-FB LAB BACK FB

X1 A+FB LAB ON FB

X2 B-FB BOTTLE OUT F/B

X3 B+FB BOTTLE IN F/B

X4 C-FB CAP BACK FB

X5 C+FB CAP ON FB

X6 START START Push Button

X7 NSTOP STOP Push Button

X10 NESTOP NE STOP Emergency Stop

X11 BLUE PB Single Step Push Button

X12 SPARE

X13 Single Step Auto Sel. X13 = 0 Auto Mode, X13 =1 Single Step mode



Output List I/O PLC Name Comment

Y0 A+OP LAB ON OP

Y1 B+OP BOTTLE IN OP

Y2 C+OP CAP ON OP

Y3 AIR ENABLE SOLINOID

AIR ON

Y4 RED LAMP EStop or return from EStop Indicator

Y5 BLUE LAMP Single Step Mode Indicator Lamp

Y6 GREEN LAMP Running or OK to run Indicator

Internal Relays I/O PLC Name Internal Relay Label and Cap Name




State Relays

I/O PLC Name Control States Label and Cap Name

S0 INITIAL STATE INITIAL STATE

S10 5 SECOND DELAY STATE BOTLE IN STATE

S11 ITITIALISE M/C STATE ITITIALISE M/C STATE

S12 BOTLE IN STATE BOTLE IN STATE

S13 LAB ON STATE LAB ON STATE

S14 LAB BACK STATE LAB BACK STATE

S15 SMALL LAB ON STATE SMALL LAB ON STATE

S16 SMALL LAB BACK STATE SMALL LAB BACK STATE

S17 WAIT1 WAIT1

S18 CAP ON STATE CAP ON STATE

S19 CAP BACK STATE CAP BACK STATE

S20 WAIT2 WAIT2

S21 BOT OUT STATE BOT OUT STATE



System Schematic

Capping and Labelling machine schematic



System operation:

Piston A is the label applicator piston, Piston B is the Bottle push in and pull out of

the label and capping machine piston and Piston C is the bottle cap applicator piston.

Upon pressing the Start push button the PLC should implement a five second warning

period indicated by flashing the Red and Green indicator lamps. After the five

seconds warning period, if the machine is not correctly initialised it will automatically

initialise the system with A-, B- and C-. When the machine is correctly initialised to

accept a bottle the Green indicator lamp should illuminate.

When all the initial conditions are true and a bottle detection signal is received by

pressing the Green start push button, the PLC operates Piston B in the B+ direction

until the signal B+FB activates, this puts the bottle into the labelling machine. The

PLC then commences a parallel operation of capping and labelling the bottle at the

same time.

The capper requires one operation but the label applicator is required to apply two

labels requiring two operations. The first label application applies the bottle size label

and the second application applies a special offer label.

The label applicator will operate Piston A is in the A+ direction until the signal A+FB

activates, this applies the first label to the bottle. Then labeller is withdrawn from

the bottle by operating Piston A is in the A- direction until the signal A-FB activates.

This operation is repeated for the second label.

At the same time the labeller is operating the cap is placed on the bottle with the C

piston. The cap applicator will operate Piston C is in the C+ direction until the signal

C+FB activates, this applies the cap to the bottle. Then cap applicator is withdrawn

from the bottle by operating Piston C is in the C- direction until the signal C-FB

activates.

When both labels and the cap are applied then the bottle should be withdrawn from

the capping and labelling machine. This is carried out by Piston B in the B- direction

until the signal B-FB activates; this pulls the bottle out of the labelling machine.

The machine is now ready to accept the next bottle for capping and labelling.

Programming Exercise:

1. Draw a fully labelled Sequence Function Chart for the required operation of

the capping and labelling machine incorporating the following features.



2. After pressing the start push button, a five second warning by flashing both

the Green and Red Indicator lamps should be given. After the 5 s warning the

system should initialise its self and then commence operation.

3. Implement your program on the Mitsubishi PLC and incorporate a single step

button in the program which will hold each step until the single step button is

operated (Hint: PLS instruction).The switch X13 will enable the single step

mode when it is on. The Blue indicator lamp should illuminate to identify that

the machine is in the single step mode.



normal operation and flash when the cycle is paused with the Nstop push

button.



should flash while the Emergency Stop is activated. The Red lamp should be on

constantly on removal of the Emergency Stop and go out when the system is

restarted.

6. If Stop is pressed the machine should pause after completing the currently

active step. The operation continues from that point on pressing the start push

button.

7. Test and debug your program.

8. Print out the final version of your program, make sure that the printout has

the relevant information. DO NOT PRINT until staff in lab has checked your

printer settings. Incorrect settings will result in lots of unwanted pages.



Chapter 8, Human Machine Interface (HMI)

Introduction The term Human Machine Interface (HMI) is also known by a number of different

names, Operator Machine Interface (OMI) and the less politically correct Man

Machine Interface (MMI). But in essence they are all the same device. They permit a

person who is responsible for a machine to interface (or operate or manage) with that

machine. Before we begin to develop the interface it is important to ensure we design

the screens and layouts carefully and methodically.

How the Brain Processes Images

This chapter focuses on how the brain connects the visual information to information

stored in memory. In order to correctly direct the person to complete a task it is

critical that the way the person interprets the information is taken into account.

Consider the example of driving a car or bike and trying to find a house. As the

person travels down the road (being careful to ensure they are focused on the road,

after all it is the law), the fields of vision to the left and right are scanned in a

sweeping motion. As shown in the Figure below. But how is information processed

within the brain.

1. Attention Phase As the information is being processed, the image shown in Figure below is observed.

The brain enters the attention phase. The gathered data from the senses passes into

Road with information left and right



the sensory memory. Visual data is held there for less than a second, before being

deleted or lost if the brain does not pay attention to it. Attention is the vital first

stage in the metal processing of any sensory input. If attention is not given to the

artefact it is lost from memory.

2. Filter and Focus Phase The next stage of the process is the filter and focus. Now the brain uses the stored

image and filters out any irrelevant information and focuses in on the important data.

This is often an unconscious process which could be a flicker or movement, a change

in contrast or colour or reflection of light. At this point the object is not identified

within the image, there is no house visible, there is a window (but cars, schools, barns

etc have windows too), there is slate or tiles and some walls but the house shape is

hidden from view.

Attention, the vital first stage in mental processing

Filter and focus of image



3. Identification Phase The brain now enters the identification phase of the process also know as the

labelling phase of the process. It is very often in the real-world that the key

information is partially obscured form the current location. The use of both eyes

here makes identifying shapes slightly quicker than a person with single eye vision as

a type of three dimensional aspects helps process the key objects more efficiently.

If this observation is via a computer screen then the three dimensional aspect is not

so reliant unless the images were heavily based on three-dimensional imagery. This is

because the single eyed person would have lost some of the ability or knack of

processing these types of images. So, all the key information artefacts in the

focused and filtered image are identified.

So far in the process the brain has been acting in a bottom up capacity. This is where

all the senses have been used and an image has been captured, attention given to the

image, the image has been filtered and focused. But in this example this is not

enough. The brain now needs to work from them top down. It must hypostasise on

what the labelled artefacts are and are they important. So the brain in its long term

memory creates a model of all kinds of things from cars to houses, friends, animals,

social groups and many more all at different levels of abstraction. These are called

stereotypes. An over simplified example of a stereotype for dwellings is show in the

Figure below, in reality they are much more complex and dynamic and have the ability

to operate with reduced levels of information. To illustrate this observe the houses

shown in the filtered and focused image does not appear exactly as per the

stereotype list. The house in the image is hidden behind a car and trees. But the

brains process the labelled artefacts in a “could it be this???” way. If it finds a close

or exact match then it ties the two together

The brains routine of creating stereotypes can also be very destructive, leading to

social problems such as racial prejudice.



Now all the details are identified, the person does some more brain processing to see

if that is the house of interest or not and act accordingly.

Name: Bungalow

Style: Single-Story

Colour: White wall & Brown Roof

Name: HouseStyle: Two-story

Colour: Dark, black and charcoal

Name: Condo

Style: Multi-storey


Name: House

Style: Single-storey with porchColour: Bright, Terracotta walls grey roof

Stereotype: Dwelling

Name: Bungalow

Style: Single-Story

Colour: White wall & Brown Roof

Name: HouseStyle: Two-story


Name: Condo

Style: Multi-storey


Name: House

Style: Single-storey with porchColour: Bright, Terracotta walls grey roof

Stereotype: Dwelling

Stereotypes options for dwellings

Stereotype bottom up processing



How the eyes scan and brain interprets From the age of one, a child can find two objects the same in a pack of visual cue

cards. So from a very young age the iconic image is formed in the brain. This is done

in the Right side of the brain as illustrated in the diagram below. When the child goes

to school for the first time at the age of four or five the child begins to see shapes

of letters of the alphabet and eventually in the form of words. This is accomplished

in the Left side of the brain. So there is fundamental separation in the brain in

regard to images and text. But as the brain develops connections between the two

individual sides begin to be made.

As a result of this user interfaces that use images have faster and usually more

accurate identification than the text based versions.

LEFT Brain RIGHT BrainThe left side of the brain is responsible for the logical and rational as aspects of thinking as

well as verbal and mathematical skills

Language: Your ability to

express yourself in words is

usually controlled by the

frontal lobe of the left cerebral

hemisphere

Methodical thinking: Logical,

technical thinking, although

most science also involves

being creative which is an

activity of the right side of

brain.

Rational thought: Thinking

and reacting in a judicious

way is a left-brain activity. It

allows forward problem

solving abilities.

Mathematical skill: Research

highlights the left-brain is

much better at dealing with

numbers and algorithmic

patterns necessary for

mathematical skills.

Writing skills: Like spoken language, writing skills that

involve organising ideas and

expressing them in words are

largely controlled by the left

hemisphere.

The right side of the brain focuses on creative thoughts,

emotional and intuitive responses. It is also important

for spatial awareness.

Spatial skills: Ability to

visualise and work with three-

dimensional shapes

Art: Visual art is related to

spatial skills i.e. drawing,

painting or looking at art.

Imagination: Creative

imagination is mainly directed by

the right hemisphere. Although

expressing imagination involves

left-brain skills.

Perception: Ability to see clearly

and intuitively into the nature of

a complex person, situation, or subject. Understanding and

Comprehension. But this is tied

to rational thought which is an

activity of the left brain.

Music: Live visual art, music

involves a lot of right-brain

activity, but trained musicians

also use their left brains to

master musical theory which

is mathematically based.

LEFT Brain RIGHT BrainThe left side of the brain is responsible for the logical and rational as aspects of thinking as

well as verbal and mathematical skills

Language: Your ability to

express yourself in words is

usually controlled by the

frontal lobe of the left cerebral

hemisphere

Methodical thinking: Logical,

technical thinking, although

most science also involves

being creative which is an

activity of the right side of

brain.

Rational thought: Thinking

and reacting in a judicious

way is a left-brain activity. It

allows forward problem

solving abilities.

Mathematical skill: Research

highlights the left-brain is

much better at dealing with

numbers and algorithmic

patterns necessary for

mathematical skills.

Writing skills: Like spoken language, writing skills that

involve organising ideas and

expressing them in words are

largely controlled by the left

hemisphere.

The right side of the brain focuses on creative thoughts,

emotional and intuitive responses. It is also important

for spatial awareness.

Spatial skills: Ability to

visualise and work with three-

dimensional shapes

Art: Visual art is related to

spatial skills i.e. drawing,

painting or looking at art.

Imagination: Creative

imagination is mainly directed by

the right hemisphere. Although

expressing imagination involves

left-brain skills.

Perception: Ability to see clearly

and intuitively into the nature of

a complex person, situation, or subject. Understanding and

Comprehension. But this is tied

to rational thought which is an

activity of the left brain.

Music: Live visual art, music

involves a lot of right-brain

activity, but trained musicians

also use their left brains to

master musical theory which

is mathematically based.

Left and Right operation



From our early education we have been taught to read from left to right and from

top down. This is illustrated by the gaze hot spots on this sample web sight published

in a paper by Nielsen in 2006. This is assuming that there are no other obvious stimuli

which would immediately attract the attention of the observer.

Now using that concept it has been shown that it important that screen layouts

assimilate to use these natural visual cues.

Eye Gaze illustrated using hot spots Nielsen, J. (2006)

Screen Layout

Assuming our culture of reading from left to right and top to bottom

Most looked at zone

With high awareness of stimuli

Least looked at zoneWith low awareness of stimuli

Normal activity zone

Normal awareness of stimuli

Normal activity zoneNormal awareness of stimuli

Screen Layout


Most looked at zone


Least looked at zoneWith low awareness of stimuli



Normal activity zoneNormal awareness of stimuli



Take for example the following home energy meter display. On the left is the actual

display, on the right is the over laying of the stimuli awareness zones.

The stimuli awareness zones apply to all types of media and is based on our cultural

upbringing. Make a mental note of where their logo is and where the price is on the

display. It makes the layout more interesting when viewing billboard or websites.

Existing DisplayExisting Display

Most looked at zone





Normal awareness of stimuliLeast looked at zone

With low awareness of stimuli


Most looked at zone





Normal awareness of stimuliLeast looked at zone



Most looked at zone






Least looked at zone


Most looked at zone






Least looked at zone




When using a control panel and manual valves etc it is essential that an operator

would need to know about the process and retain a mental perspective of the system.

However, over time the operator would begin to develop a mental model of system.

This is enhanced over time, but if after a period of time the acquired knowledge is

not used it is lost and the residual knowledge contains only the normally encountered

information. So when a change occurs that was not normally encountered the

operators have difficulty to identify it and rectify it.

Act

SeeSmellHear

Direct control

Real Process(to control)

Mental

model

Image from real (illusion)

Distant/remote control

Drawing

Symbolic

Illusion and mental model:

build an appropriate tool

successive exploration

areas

Increase knowledge surface

Key points Residual knowledge after

using the system for a while

Knowledge acquisition Residual knowledge

(a) (b)

Mental model developmentMental model development

Beginner Expert

successive exploration

areas

Increase knowledge surface

Key points Residual knowledge after

using the system for a while

Knowledge acquisition Residual knowledge

(a) (b)

Mental model developmentMental model development

Beginner Expert



As each operator residual memory develops differently it is possible for

inconsistency to occur in the management of a process. This is a disaster in the

making especial if complex processes are involved. Imagine not have consistent bread,

milk and pens.

So if the designer of the system wants consistency in its operation they need to

develop a number of screens that are linked together and spoon feed the operator as

to what needs to be done.

The operator is

prompted on the

best operation of

the system.

Not as much process

training

information

needed.

The operator needs to retain

information and knowledge about

the process in their memory

The operator is

prompted on the

best operation of

the system.

Not as much process

training

information

needed.

The operator is

prompted on the

best operation of

the system.

Not as much process

training

information

needed.









Chapter 9, High Speed Control

Introduction As discussed in previous lectures the PLC is designed using the latest processers and

components; however the clock speeds for these devices is normally slower, so they

can be used reliably in harsh environments. The inputs are opto-isolated and the

components are normally encapsulated in a faradays type cage structure. In addition

to this the manufacture only allows the devices to be programmed using their own

software. This is different to the PC market where many third party suppliers can

provide software. But a caveat to this scheme is that the computer system is at the

mercy of the programmers and some are poor and some are very good. The poorly

constructed software application however, holds the whole PC to ransom.

This is avoided in the PLC as only one software application can be used. The

manufacture ensures the program is accurate and appropriate for the attached

device. Any problems and the user will receive an error.

The high speed function of a PLC is achieved by altering the scan cycle and including

the concept of interrupts. If you have done any microcontroller courses, interrupts

are one of the main backbone facilities employed. Most peripheral devices can

generate interrupts in order to receive service from the operating system (OS).

Some examples of devices that can use interrupts are PC cards, onboard timers, audio

input devices, keyboards, touch screens, and pointing devices. Nearly any type of

peripheral device might use interrupts as the principle method of initiating servicing

actions by the OS. On the PLC side this interrupt is accomplished within the OS of

the PLC and is used on Counters, Inputs, Reads, compare instructions.

In addition to this the peripheral devices such as the Analogue to Digital also have

their own high speed facility.

• When an interrupt occurs, continuation of the execution of the current

program is meaningless.

– Execution of the Current program needs to be stopped.

• In a controller, PLC or Industrial Computer system, there are many sources of

interrupts:

– Needs to prepare interrupt processing routines for each source of

interrupts.

– Source of interrupt needs to be identified.

– Needs to initiate execution of the interrupt processing routine

associated with the identified interrupt.



• When the interrupt is resolved, the interrupted program needs to be continued

for the efficiency reason:

– Needs to resume execution of the interrupted program

Interrupt process:

(a) Program ceases to execute, When ?

– At the completion of the current instruction in the CPU

– Not at the end of current memory(machine) SCAN cycle

(b) Save Information, Where ?

– Stack, Memory

(c) Execute interrupt preprocessing

– Identify the source of interrupt

» Initiate the execution of the Interrupt Processing Routine of the identified interrupt source

(d) Execution of the interrupt processing routine

– Save the state of the interrupted program, Where ?

– Resolve the interrupt

(e) Restore Information and the status of the interrupted program, and

resume execution of the interrupted program.

When an interrupt is processed, a specific sequence of events takes place. You write

the interrupt service request (ISR) and interrupt service thread (IST) for the

device driver with the following sequence of events in mind:

1. When an interrupt occurs, the microprocessor jumps to the kernel exception handler.

2. The exception handler disables all interrupts of an equal and lower priority at the

microprocessor, and then calls the appropriate ISR for the physical interrupt request (IRQ).

3. The ISR returns a logical interrupt, in the form of an interrupt identifier, to the interrupt

handler and typically masks the board-level device interrupt.

4. The interrupt handler re-enables all interrupts at the microprocessor, with the exception of

the current interrupt, which is left masked at the board, and then signals the appropriate IST

event.

5. The IST is scheduled, services the hardware, and then finishes processing the interrupt.

6. The IST calls the InterruptDone function, which in turn calls the OEMInterruptDone function.

Control Engineering Major 2-Automation Section, …eleceng.dit.ie/jmcgrory/dt021_Y4_ControlEngineeringV1_CONT4601... · module on control engineering. ... Control Engineering Major

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