ABSTRACT

Conveyor systems have been a mainstay of material handling for over 100 years. Conveyors are ideally suited to solving handling problem as a complete system rather than as a individual units. A complete conveyor system involves a combination of conveyors, accessories and controls the monitor and control the movement of material through the operation process. In this project is concerned with learning and exploring Grafcet and PLC as programming tool. The programmable logic contmller pLC) was becoming more powerful and high technology that extensively used in automation works. Thus, an efficient approach which can represent the control process by using the graphical representation perhaps a good solution to helps the designer in order to programming the PLC's. There has been a growing interest in programming languages for PLC's. In order, the sequential fhction chart (SFC), an international standard based on the GRAFCET language was introduced in 1977 at France. The GRAFCET language has been used as one of the most important means for designing, programming and describing logic sequential control system. This powerful graphical language dedicated to the specification of the behavior of sequential logical systems. It is standardized by CEI and its semantic is defined for this type of applications. The GRAFCET is a very good tool for logic controller speci.fication, and the graphical nature of the language makes GRAFCET easy or simply can learn and implement or use in automation works especially in company site. In this conveyor system it is easy to handling material because a part of conveyor in this system is can move up and down. It is suitable to handling material or product h m one plan to another plan.

Sistem konveyer telah digunakan lebih seratus tahun lama Satu system konveyer lebih sesuai digunakan untuk menyelesaikan masalah dalam pengangkutan barang atau produk berbanding dengan mengunakan konveyer secara individu. Dalam satu system konveyer, ia meliputi kombinasi konveyor-konveyer, aksesori, dan pengaturan pergerakan produk melalui satu proses operasi. Dalam projek ini iaitu mengatur pergerakan motor konveyer, ia meliputi pengetahuan dan pembelajaran mengenai PLC dan GRAFCET sebagai alat untuk mengaturcara. Grafcet merupakan satu cara pengaturcaraan dengan menggunakari PLC. Sistem pengaturcaram ini adalah satu sistern pengaturcaraan berpiawaian antarabangsa dan telah diperkenalkan pada tahun 1977 di Prancis. Dalam GRAFCET, Pengahmmaan bergantung kepada pergerakan carta (flow chart) yang dilukis berdasarkan system GRAFCET. Dengan menggunakan GRAFCET pengaturcaraan atau penyelesaian masalah dalarn satu sistem automasi menjadi senang dan mudah untuk difhhami. Dalam sistem konveyer ini, ia mudah digunakan untuk membawa produk kerana safah satu bahagian konveyer dalam sistem ini boleh bergerak ke atas dan bawah dan ia sesuai untuk mengasingkan barangan.

CHAPTER I

INTRODUCTION

Conveyor Belt Motor systems have been a mainstay of material handling for over 100 years. Conveyors are ideally suited to solving handling problem as a complete system rather than as an individual unit. A complete conveyor system involves a combination of conveyors, accessories and controls the monitor and control the movement of material through the operation process by using control Grafcet as programming tool. In this project is concerned with learning and exploring Grafcet and PLC as programming tool. The programmable logic controller (PLC) was becoming more powem and high technology that extensively used in automation works. Thus, an efficient approach which can represent the contro1 process by using the graphical representation perhaps a good solution to helps the designer in order to programming the PLC's.

Figure 1.1: CONVERYER BELT MOTOR SYSTEM

In this project according to system in Figure 1 .O, there is four conveyor are combines to result one conveyor belt system. The function of this system is to detect two types of products and transfer the products to two deferent locations in this system.

OBJECTIVE

The objective of the project is, study how to control the motor conveyor belt and automation system. Second is study and familiarize with the PLC programming and GRAFCET as programming tool. It is very important because in working environment the automation system is widely used by companies and industries. As an engineer, it is better if we understand and know how to control a conveyor or automation system by using PLC and Grafcet.

In this project we need to undemtand why we need to control the conveyor belt. For this project, we use PLC to control the conveyor and GRAFCET as programming tool. The purpose of used PLC to control the conveyor is, that the PLC is very easy to program by understanding the PLC program through ladder diagramed. If there is any problem during test or when the project is run, it's easier for troubleshoot. In this project we use GRAFCET as a prpgramming tool. When we use GRAFCET we can understand the program of PLC easier, not by the ladder diagram but by the flow chart where used GRAFCET to draw it.

LITERATURE STUDY

Before and to complete this project, we to study and understand abuts PLC, Graf' and automation system

3.1 Programmable logic controller

A programmable logic controller is a computer designed for use in machines. Unlike a computer, it has been designed to operate in the industrial environment and is quipped with special inputs/outputs and a control programming language. The common abbreviation used in industry for these devices, PC, can be confusing because it is also the abbreviation for personal computer. Therefore, some manufacturers refer to their progrtmable cor~troller s a PLC, which is an abbreviation for programmable logic controller.

Initially the PLC was uqed to replace relay logic, hut its ever-increacing range of functions means that it is found in many and more complex applications. As the structure of a PLC is based on the same principles as those employed in computer architecture, it is capable of performing not only relay switching tasks, but also other

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applications such as counting, calculating, comparing, and the processing of analog signals.

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Programmable controllers offer several advantages over a conventional relay type of control. Relays have to be hard-wired to perform a specific function (Figure 3.1.1). When the system requirements change, the relay wiring has to be changed or modified, which requires time. In extreme cases, such as in the automation industry, complete control panels had to be replaced since it was not economically feasible to rewire the old panels with each model changeover. The programmable controller has eliminated much of the hand wiring associated with conventional relay control circuits. It is small and inexpensive compared to equivalent relay-based process control systems. Programmable controllers also offer solid-state reliability, lower power consumption, and ease of expandability. If an application has more than a half-dozen relays, it probably will be less expensive to install a PLC- Simulating a hundred relays, timers, and counters is not a problem even on small PLCs.

PB l (light lamp) PB2(turn off lamp)

Figure 3.1.1: Relay wiring Diagram

Figure 3.1.2 : Hard-wired relay of control(Schematic Diagram)

Figure 3.13: PLC Block Diagram

A personal computer can be made into a programmable controller if you provide some

Output Module

Input Module

way for the computer to receive information fiom devices such as pushbuttons or switches. You also need a program to process the inputs and decide the means of turning

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Central processing unit

r

OFF and ON load devices. A typical PLC can be divided into three parts, as illustrated in C

the block diagram of Fig. 2. These three components are the central processing unit (CPU), the input/output (VO) section, and the programming device. The programmable controller is an event-driven device, which means, that are event taking place in the field will result in an operation or output taking place. The central processing unit (CPU) is the heart of the PLC system. The CPU is a microprocessor-based system that replaces control relays, counters, timers and

sequencers. A processor appears only once in a PLC, and it can be either a one-bit or a word processor. One-bit processon arc adequate for dealing with logic opemtions, PLCs with word processors are used when processing text and numerical data, calculations, gauging, controlling, and recording, as well as the simple processing of signals in binary code, are required. The principle of operation of a CPU can be briefly described as follows:

The CPU accepts (reads) input data fiom various sensing devices, executes the stored user program fiom memory, and sends appropriate output commands to control devices. A direct current (dc) power source is required to produce the low-level voltage used by the processor and the UO modules. This power supply can be housed in the CPU unit or may be a separately mounted unit, depending on the PLC system manufacturer.

Most CPUs contain backup batteries that keep the operating program in storage in the event of a plant power failure. Typical retentive backup time is one month to one year.

The CPU contains various electrical parts and receptacles for connecting the cables that go to the other units as well as to operational key switches.

Typical operation key switch positions are:

OFF: System cannot be run or programmed. Run: Allows the system to run, but no program alterations can be made. Program: Disables outputs and allows creating, modifLing, and deleting of programs.

The processor memory module is a major part of the CPU housing. Memory is where the control plan or prograrp is held or stored in the controller. The information stored irl the ~ ~ m o r y relates to the w y the bput and ~?!tp?!t data should hpl processed. The complexity of the program determines the amount of memory required. Memory elements store individual pieces of information called bits (for b i i digits).

The actual control program is held within electronic memory storage components, such as the RAMS and EEPROMs. The processing unit scans data fium the input and output

modules and stores their conditions in the memory. The processor unit then scans the user program stored in the memory and makes decisions that cause outputs to change.

Memory can be placed into two categories:

Volatile and nonvolatile. Volatile memory will lose its stored information if all operating power is lost or removed. Volatile memory is easily altered and quite suitable for most applications when supported by battery backup. Nonvolatile memory can retain storeci information when power is removed accidentally or intentionally. PLCs make use of many different types of volatile and nonvolatile memory device.

Summary about PLC

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Push Button

I:/ Push Butbn

17 External power

Figure 3.1.4: Processor Memory

L1

Load Power

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+ +

CPU

b

b

P R 0 C C E S S I N G

I N P u T

b

o e,

$

0 . u T P u T

MEMORY

I Figure 3.1.7: PLC Ladder Diagram

1 .o 1 0.0 1 0.03 1 I In

1-01 I I

1.02 0.02 0.03 I I I A

1.02 I I

3.2 GRAFCET

In PLC Ladder Diagram, Jnput Start O.OX and Output Start 1.OX

Input:- PB = Push Button PBl = 0.03 PB2 = 0.02 PB3 = 0.03 Output:- Motor = 1 .Ol Lamp = 1.02

3.2.1 History Of GRAFCXT

GRAFCET was proposed in France in 1977 as a formal specification and realization method for logical controllers. The name GRAFCET was derived from graph, since the model is graphical in nature, and AFCET (Association Francaise de Cybernetique Economique Et Technique) the scientific association that supported the work

During several years, GRAFCET was tested in French industries. It soon proved to be a convenient tool for representing small and medium scale sequential systems. GRAFCET was therefore introduced in the French educational programs and proposed

as a standard to the French association AFNOR where it was accepted in 1982. In 1988 GRAFCET, with minor changes, was also adopted by the International Eledro technical Commission HIECI as an international standard named IEC 848, JIEC, and 1988K. In this standard GRAFCET goes under the name Sequential Function Chart HSFCI.

The standard concerns programming languages used in Programmable Logic Controllers HPLCI. It defines four different programming language paradigms together with SFC. No matter which of the fbur different languages that is used, a PLC program can be structured with SFC. Because of the two international standards, GRAFCET, or SFC, is today widely accepted in industry, where it is used as a representation format for sequential control logic at the local PLC level.

33.2 What is GRAFCET?

The Grafcet language has three basic elements: States, actions and transitions. The state is represented by notation S; and the transitions will be represented by t;. Since we will describe the control system that using the PLC as the wntroiler, we need to describe the Grafcet into the ladder diagram, to be specific, the Boolean logic equations. The ladder diagram consists of:

(i) Transition Firing Equation (ii) L8icIring E q d n ( i i i i Power Circuit/ Output enablin~dbabling Quation

The Grafit evolves from one step to another by firing transitions. A transition fires when its inputs steps are active and its transition-condition is true. When a transition fires, its input steps is disabled and its output step is enabled. The above evolution is captured in two sets of Boolean equations: the transition firing equations and latching

equations. By using the power circuit or output enabling/disabling equations, we can see the step is being coincident with the taking the actions ofthnt step.

3.23 State

State can be defined as the memory of specifications and their activity is characteristics of the steps. We can represent the state as Keep relay or i n t e d relay in the PLC programming. We can assume the function of the Keep relay just the same as the flip flop characteristics.

We have 2 types of state:

a) For the initial state, it is represented by a double square (Figure 3.2.3.1) with a 0 inside. This state which should be active when the system is started.

Figure 3.23.1: Initial state

b) The internal state represented by a circle (Figure 3.2.3.2) is converted into a square with a number corresponding to the state (Figure 3.2.3.3)

b

Figure 3.232: Internal state Figure 323.3: State

3.2.4 Actions

Actions are used to specify the value of outputs according to active steps and value of input. The actiodsteps to be performed at a given state tue described inside a rectangle linked to the corresponding state as in Figure 32.4.1

e Output when the State No I is active

1 State No. 1

Figure 3.2.4.1: Actions

3.2.5 Transitions

Transitions are used to describe the evolution of the state according to the changes of input variables. Each transition is associated with a step of preceding steps, a set of succeeding steps and a transition-condition that is a Boolean hc t ion of inputs. The transition is cleared when all preceding steps are active and the transitiokcondition is true.

A transition between two states is represented by a line with a stroke and labeled with the transition capacity which should be 1 if the transition has to take place

Figure 1 Lamp ON 3.2.5.1: Transition line

I 1

2 I Motor ON I

Figure 33.2: 512 way valve positioning

The 512 valve is used to control items such as double acting cylinders which have two inputs. The inputs to the cylinder are connected to ports 2 and 4, the air supply to port 1. Ports 3 and 5 are allowed to exhaust to atmosphere.

The number 5 signifies that the valve has five ports, whilst the number 2 signifies that the valve has 2 directions or states.

Figure 3 3 3 cylinder extend

3 E B 5 Y . d 3 rn tz ? C-, 3 a 5 C 3 2 3 2 Ei U d . C 8 8 .d + U z a m 2 0 E - S: I-, b d 8 Ti W 7