Submitted as a part of the PROJECT REPORT PATTERN GENERATION UNIT FOR PNEUMATIC SYSTEMS Submitted by NEEL PATEL

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PROJECT REPORT

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PATTERN GENERATION UNIT FOR PNEUMATIC SYSTEMS

Submitted by

NEEL PATEL & SHWET SHAH & VISHVESH JANI

In partial fulfillment for the award of the degree of

BACHELORS OF ENGINEERING

in

MECHANICAL ENGINEERING from

SAL INSTITUTE OF TECHNOLOGY AND ENGINEERING

RESEARCH.

Gujarat Technological University

Ahmadabad

DECLARATION

We hereby declare Reports, submitted along with the Project model for the project entitled

” PATTERN GENERATION UNIT FOR PNEUMATIC SYSTEMS submitted in partial fulfillment

for the degree of Bachelor of Engineering in MECHANICAL ENGINEERING to Gujarat

Technological University, Ahmadabad. Of the project work carried out at SAL INSTITUTE OF

TECHNOLOGY AND ENGINEERING RESEARCH under the supervision of PROF. PIYUSH

DEVANI and that no part of any of these has been directly copied from any students’ reports or taken

from any other source, without providing due reference.

Name of The Students

NEEL PATEL

SHWET SHAH

VISHVESH JANI

Sign of Students

CERTIFICATE

This is to certify that the report, submitted along with the project entitled “PATTERN GENERATION

UNIT FOR PNEUMATIC SYSTEMS” has been carried out by

NEEL PATEL & SHWET SHAH & VISHVESH JANI under my guidance in partial

Fulfillment for the degree of: Bachelor of Engineering in MECHANICAL ENGINEERING 8th

Semester of Gujarat Technological University, Ahmadabad during the academic year 2017. These

students have successfully completed activities under my guidance.

Internal Guide Head of the Department

ACKNOWLEDGEMENT

We have a great pleasure in presenting this project report on “PATTERN GENERATUION UNIT

FOR PNEUMATIC SYSTEMS” to express our deep regard to towards those who have offered their

valuable time and guidance in our hour of need.

We would like to express our gratitude to our inspiring guide PROF. PIYUSH DEVANI, who gave us

the guidance and encouraged us though out this project. We would like to

Thank SAL INSTITUTE OF TECHNOLOGY & ENGINEERING RESEARCH, AHMEDABAD

for giving us the facility to perform this project. We furthermore would like to thank The Head of

Department, PROF.MANISH PATEL of The mechanical Engineering Department.

We have great pleasure in offering our sincere thanks to our honorable principal DR. RUPESH

VASANI. Last but not least, we would like to thank all the direct and indirect help provided by friends,

parents and the staff of this college.

LIST OF CONTENTS

1. Abstract
2. Objectives of project
3. Chapter-1 Introduction to pneumatic systems
4. Chapter-2 Design and Development of a Pneumatic Circuits
5. Chapter-3 Control of Industrial Pneumatic Systems using Serial Communication Technology & Mat lab
6. Canvas image and product advantages
?

Abstract

? In today’s era, Automation is a vital parameter. Even Small scale industries have also started to adopt semi automatic or fully automatic machines according to their budget and productivity. As these machine are programmable, productivity automatically increases and lead time decreases.
? In order to increase the productivity, we have come up with a solution to design a Design a Computer Numerical Electro Pneumatic Control System for small scale industries. This system can create any machining sequence, which is driven by electro pneumatic system. User just have send some position and delay codes (P code like G code and M code) inside the controller to achieve any Positional step diagram in the system.

Software to be Used
? Arduino IDE
? XCTU (Testing )
? Automation Studio (Simulation of Pneumatic Part )
? Proteus ( Simulation of Electronic Part)

Hardware to be used

? Arduino UNO
? LCD
? Pushbuttons
? Solenoid Valves
? Electromechanical Switches
? Pneumatic Actuator
? Compressor

Chapter-1 Introduction to Pneumatic Systems
1 Pneumatic systems
A pneumatic system is a system that uses compressed air to transmit and control energy. Pneumatic systems are used in controlling train doors, automatic production lines, mechanical clamps, etc .

(a)Automobile production line
(b) Pneumatic system of an automatic machine
Fig. 1 Common pneumatic systems used in the industrial sector
(a) The advantages of pneumatic systems
Pneumatic control systems are widely used in our society, especially in the industrial sectors for the driving of automatic machines. Pneumatic systems have a lot of advantages.
(i) High effectiveness
Many factories have equipped their production lines with compressed air supplies and movable compressors. There is an unlimited supply of air in our atmosphere to produce compressed air.Moreover, the use of compressed air is not restricted by distance, as it can easily be transported through pipes. After use, compressed air can be released directly into the atmosphere without the need of processing.
(ii) High durability and reliability
Pneumatic components are extremely durable and can not be damaged easily. Compared to electromotive components, pneumatic components are more durable and reliable.
(iii) Simple design
The designs of pneumatic components are relatively simple. They are thus more suitable for use in simple automatic control systems.
(iv) High adaptability to harsh environment
Compared to the elements of other systems, compressed air is less affected by high temperature, dust, corrosion, etc.
(v) Safety
Pneumatic systems are safer than electromotive systems because they can work in inflammable environment without causing fire or explosion. Apart from that, overloading in pneumatic system will only lead to sliding or cessation of operation. Unlike electromotive components, pneumatic components do not burn or get overheated when overloaded.
(vi) Easy selection of speed and pressure
The speeds of rectilinear and oscillating movement of pneumatic systems are easy to adjust and subject to few limitations. The pressure and the volume of air can easily be adjusted by a pressure regulator.
(vii) Environmental friendly
The operation of pneumatic systems do not produce pollutants. The air released is also processed in special ways. Therefore, pneumatic systems can work in environments that demand high level of cleanliness. One example is the production lines of integrated circuits.
(viii) Economical
As pneumatic components are not expensive, the costs of pneumatic systems are quite low.
Moreover, as pneumatic systems are very durable, the cost of repair is significantly lower than that of other systems.
(b) Limitations of pneumatic systems
Although pneumatic systems possess a lot of advantages, they are also subject to many limitations.
(i) Relatively low accuracy
As pneumatic systems are powered by the force provided by compressed air, their operation is subject to the volume of the compressed air. As the volume of air may change when compressed or heated, the supply of air to the system may not be accurate, causing a decrease in the overall accuracy of the system.
(ii) Low loading
As the cylinders of pneumatic components are not very large, a pneumatic system cannot drive loads that are too heavy.
(iii) Processing required before use
Compressed air must be processed before use to ensure the absence of water vapour or dust.Otherwise, the moving parts of the pneumatic components may wear out quickly due to friction.
(iv) Uneven moving speed
As air can easily be compressed, the moving speeds of the pistons are relatively uneven.
(v) Noise
Noise will be produced when compressed air is released from the pneumatic components.
(c) Main pneumatic components
Pneumatic components can be divided into two categories:
1. Components that produce and transport compressed air.
2. Components that consume compressed air.
All main pneumatic components can be represented by simple pneumatic symbols. Each symbol shows only the function of the component it represents, but not its structure. Pneumatic symbols can be combined to form pneumatic diagrams. A pneumatic diagram describes the relations between each pneumatic component, that is, the design of the system.
2 The production and transportation of compressed air
Examples of components that produce and transport compressed air include compressors and pressure regulating components.
(a) Compressor
A compressor can compress air to the required pressures. It can convert the mechanical energy from motors and engines into the potential energy in compressed air (Fig. 2). A single central compressor can supply various pneumatic components with compressed air, which is transported through pipes from the cylinder to the pneumatic components. Compressors can be divided into two classes: reciprocatory and rotary.

(Fig. 2)
(b) Pressure regulating component
Pressure regulating components are formed by various components, each of which has its own
pneumatic symbol:
(i) Filter – can remove impurities from compressed air before it is fed to the pneumatic components.
(ii) Pressure regulator – to stabilise the pressure and regulate the operation of pneumatic components
(iii) Lubricator – To provide lubrication for pneumatic components
(b) Pressure regulating component
Pressure regulating components are formed by various components, each of which has its own pneumatic symbol:
(i) Filter – can remove impurities from compressed air before it is fed to the pneumatic components.
(ii) Pressure regulator – to stabilise the pressure and regulate the operation of pneumatic components
(iii) Lubricator – To provide lubrication for pneumatic components

3 The consumption of compressed air
Examples of components that consume compressed air include execution components (cylinders), directional control valves and assistant valves.
(a) Execution component
Pneumatic execution components provide rectilinear or rotary movement. Examples of pneumatic execution components include cylinder pistons, pneumatic motors, etc. Rectilinear motion is produced by cylinder pistons, while pneumatic motors provide continuous rotations. There are many kinds of cylinders, such as single acting cylinders and double acting cylinders.
(i) Single acting cylinder
A single acting cylinder has only one entrance that allows compressed air to flow through.Therefore, it can only produce thrust in one direction (Fig. 4). The piston rod is propelled in the opposite direction by an internal spring, or by the external force provided by mechanical movement or weight of a load (Fig. 5).

The thrust from the piston rod is greatly lowered because it has to overcome the force from the spring. Therefore, in order to provide the driving force for machines, the diameter of the cylinder should be increased. In order to match the length of the spring, the length of the cylinder should also be increased, thus limiting the length of the path. Single acting cylinders are used in stamping, printing, moving materials, etc.
?
(ii) Double acting cylinder
In a double acting cylinder, air pressure is applied alternately to the relative surface of the piston, producing a propelling force and a retracting force (Fig. 6). As the effective area of the piston is small, the thrust produced during retraction is relatively weak. The impeccable tubes of double acting cylinders are usually made of steel. The working surfaces are also polished and coated with chromium to reduce friction.

(b) Directional control valve
Directional control valves ensure the flow of air between air ports by opening, closing and switching their internal connections. Their classification is determined by the number of ports, the number of switching positions, the normal position of the valve and its method of operation. Common types of directional control valves include 2/2, 3/2, 5/2, etc. The first number represents the number of ports; the second number represents the number of positions. A directional control valve that has two ports and five positions can be represented by the drawing in Fig. 8, as well as its own unique pneumatic symbol.

(i) 2/2 Directional control valve
The structure of a 2/2 directional control valve is very simple. It uses the thrust from the spring to open and close the valve, stopping compressed air from flowing towards working tube ‘A’ from air inlet ‘P’. When a force is applied to the control axis, the valve will be pushed open, connecting ‘P’ with ‘A’ (Fig. 9). The force applied to the control axis has to overcome both air pressure and the repulsive force of the spring. The control valve can be driven manually or mechanically, and restored to its original position by the spring.

(ii) 3/2 Directional control valve
A 3/2 directional control valve can be used to control a single acting cylinder (Fig. 10). The open valves in the middle will close until ‘P’ and ‘A’ are connected together. Then another valve will open the sealed base between ‘A’ and ‘R’ (exhaust). The valves can be driven manually, mechanically, electrically or pneumatically. 3/2 directional control valves can further be divided into two classes: Normally open type (N.O.) and normally closed type (N.C.) (Fig. 11).

Fig. 11 Pneumatic symbols

(iii) 5/2 Directional control valve
When a pressure pulse is input into the pressure control port ‘P’, the spool will move to the left, connecting inlet ‘P’ and work passage ‘B’. Work passage ‘A’ will then make a release of air through ‘R1’ and ‘R2’. The directional valves will remain in this operational position until signals of the contrary are received. Therefore, this type of directional control valves is said to have the function of ‘memory’.

(c) Control valve
A control valve is a valve that controls the flow of air. Examples include non-return valves,flow control valves, shuttle valves, etc.
(i) Non-return valve
A non-return valve allows air to flow in one direction only. When air flows in the opposite direction, the valve will close. Another name for non-return valve is poppet valve (Fig. 13).

(ii) Flow control valve
A flow control valve is formed by a non-return valve and a variable throttle (Fig. 14).

(iii) Shuttle valve
Shuttle valves are also known as double control or single control non-return valves. A shuttle valve has two air inlets ‘P1’ and ‘P2’ and one air outlet ‘A’. When compressed air enters through ‘P1’, the sphere will seal and block the other inlet ‘P2’. Air can then flow from ‘P1’ to ‘A’. When the contrary happens, the sphere will block inlet ‘P1’, allowing air to flow from ‘P2’ to ‘A’ only.

4 Principles of pneumatic control
(a) Pneumatic circuit
Pneumatic control systems can be designed in the form of pneumatic circuits. A pneumatic circuit is formed by various pneumatic components, such as cylinders, directional control valves, flow control valves, etc. Pneumatic circuits have the following functions:
1. To control the injection and release of compressed air in the cylinders.
2. To use one valve to control another valve.
(b) Pneumatic circuit diagram
A pneumatic circuit diagram uses pneumatic symbols to describe its design. Some basic rules must be followed when drawing pneumatic diagrams.
(i) Basic rules
1. A pneumatic circuit diagram represents the circuit in static form and assumes there is no supply of pressure. The placement of the pneumatic components on the circuit also follows this assumption.
2. The pneumatic symbol of a directional control valve is formed by one or more squares. The inlet and exhaust are drawn underneath the square, while the outlet is drawn on the top. Each function of the valve (the position of the valve) shall be represented by a square. If there are two or more functions, the squares should be arranged horizontally (Fig. 16).

3. Arrows “??” are used to indicate the flow direction of air current. If the external port is not connected to the internal parts, the symbol “?” is used. The symbol “?” underneath the square represents the air input, while the symbol “?” represents the exhaust. Fig. 17 shows an example of a typical pneumatic valve.
4. The pneumatic symbols of operational components should be drawn on the outside of the squares. They can be divided into two classes: mechanical and manual (Fig. 18 and 19).

5. Pneumatic operation signal pressure lines should be drawn on one side of the squares, while triangles are used to represent the direction of air flow (Fig. 20).

(ii) Basic principles
Fig. 21 shows some of the basic principles of drawing pneumatic circuit diagrams, the numbers in the diagram correspond to the following points:

1. When the manual switch is not operated, the spring will restore the valve to its original position.
2. From the position of the spring, one can deduce that the block is operating. The other block will not operate until the switch is pushed.
3. Air pressure exists along this line because it is connected to the source of compressed air.
4. As this cylinder cavity and piston rod are under the influence of pressure, the piston rod is in its restored position.
5. The rear cylinder cavity and this line are connected to the exhaust, where air is released.
(iii) The setting of circuit diagrams
When drawing a complete circuit diagram, one should place the pneumatic components on different levels and positions, so the relations between the components can be expressed clearly.This is called the setting of circuit diagrams. A circuit diagram is usually divided into three levels:power level, logic level and signal input level (Fig. 22).

5 Different kinds of basic circuits
A basic circuit is a pneumatic circuit designed to perform basic tasks, such as flow amplification, signal inversion, memory, delay, single acting cylinder control, double acting cylinder control, etc.
(a) Flow amplification
Cylinders with a large capacity require a larger flow of air, which can be hazardous to users. It is unsafe to manually operate pneumatic directional control valves with large flow capacity. Instead we should first operate manually a small control valve and use it to operate the pneumatic control system with large flow capacity. This is called flow amplification, which can greatly ensure the safety of the operators. During operation, valves with large flow capacity should be placed near the cylinder, while valves with smaller flow capacity should be placed on control boards some distances away. Fig. 23 shows a basic flow amplification circuit. Notice how different components are placed on different levels.

(b) Signal inversion
The pneumatic diagram in Fig. 24 shows how directional control valves can be switched.When operating control valve 1, control valve 2 will stop producing pressure output. When control valve 1 ceases operation and is restored to its original position, control valve 2 will resume its output. Therefore, at any given time, the pressure output of control valve 1 is the exact opposite of that of control valve 2.

(c) Memory Function
Memory is a common basic function. It can keep a component at a certain state permanently until there is a change of signals. Fig. 25 shows a memory function circuit. When control valve 1 is operated momentarily (that is, pressed for a short time), the output signal of the 5/2 directional control valve 3 will be set to ON. The signal will stay that way until control valve 2 is operated momentarily and generates another signal to replace it, causing it to stay permanently at OFF.

(d) Single acting cylinder control
Single acting cylinders can be controlled manually. However, they can also be controlled by two or more valves. This is called logic control. Examples of logic control include ‘OR’ function,’AND’ function, ‘NOT’ function, etc.
(e) Delay function
A pneumatic delay circuit can delay the operating time of the next control valve. Its principle of operation involves the use of an orifice to slow down the flow of air and control the time of pneumatic operation.
(f) Double acting cylinder
(i) Direct control
The only difference between a single acting cylinder and a double acting cylinder is that a double acting cylinder uses a 5/2 directional control valve instead of a 3/2 directional control valve (Fig. 32). Usually, when a double acting cylinder is not operated, outlet ‘B’ and inlet ‘P’ will be connected. In this circuit, whenever the operation button is pushed manually, the double acting cylinder will move back and forth once.

In order to control the speed in both directions, flow control valves are connected to the inlets on both sides of the cylinder. The direction of the flow control valve is opposite to that of the release of air by the flow control valve of the single acting cylinder. Compared to the throttle inlet, the flow control valve is tougher and more stable. Connecting the circuit in this way allows the input of sufficient air pressure and energy to drive the piston.
(ii) Single control
A cylinder always has to maintain its position in a lot of situations, even after the operational signal has disappeared. This can be achieved by the use of a circuit that possesses the memory function. As shown in Fig. 33, the extension path of a double acting cylinder is activated by control valve 1, while retraction is governed by control valve 2. Control valve 3, on the other hand, maintains the position of the cylinder by maintaining its own position.Control valve 3 will be changed only when one of the manual control valves is pushed. If both control valves 1 and 2 are operated at the same time, control valve 3 will be subject to the same pressure and will remain in its original position.

6 The application of pneumatic systems
The application of pneumatic systems is very extensive. The following are some examples.
(a) Transport system
Fig. 34a shows a simplified industrial transport system. When the button switch is pushed, the cylinder will push one of the goods from the shelf onto the transfer belt. When the button switch is released, the cylinder will retract automatically. Fig. 34b shows the circuit diagram of the transport system.

(b) Vehicle door operation system
Pneumatic systems can be used to operate the doors of public vehicles (Fig. 35a). Assuming that the opening and closing of the doors are controlled by two button switches ON and OFF. When the button switch ON is pressed, the doors will open. When the button switch OFF is pushed, the doors will close. Fig. 35b shows a pneumatic system that can be used to operate the doors of vehicles.

7 Safety measures when using pneumatic control systems
(a) Compressed air can cause serious damage to the human body if they enter the body through ducts like the oral cavity or ears.
(b) Never spray compressed air onto anyone.
(c) Under high temperature, compressed air can pass through human skin.
(d) Compressed air released from the exhaust contains particles and oil droplets, which can cause damage to eyes.
(e) Even though the pressure of compressed air in pipes and reservoirs is relatively low, when the container loses its entirety, fierce explosions may still occur.
(f) Before switching on a compressed air supply unit, one should thoroughly inspect the whole circuit to see if there are any loose parts, abnormal pressure or damaged pipes.
(g) A loose pipe may shake violently due to the high pressure built up inside it. Therefore, each time before the system pressure is increased, thorough inspection of the entire circuit is required to prevent accidents.
(h) As the force produced by pneumatic cylinders is relatively large, and the action is usually very fast, you may suffer serious injuries if you get hit by a cylinder.
(i) Switches should be installed on the compressed air supply unit to allow easy and speedy control of air flow.
(j) In case of a leakage, the compressed air supply unit should be turned off immediately.
(k) The compressed air supply unit must be turned off before changes can be made to the system.
(l) Stay clear of the moving parts of the system. Never try to move the driving parts in the mechanical operation valve with your hand.

Chapter-2 Design and Development of a Pneumatic Circuits
INTRODUCTION

The transmission and control of power by means of fluid under pressure is becoming increasingly used in all branches of industry. The extensive use of hydraulics and pneumatics system to transmit power is due to the fact that properly constructed fluid power systems posses a number of favorable characteristics. They eliminate the need for complicated systems of gears, cams, and levers. Also, they transmit motion without the slack or delay inherent in the use of solid machine parts. Fluid power is a term covering both pneumatic and hydraulic power. Pneumatic deal with the use of compressed air as the fluid whilst hydraulic power covers the use of oils and other liquids.
Pneumatic systems are very common, and have much in common with hydraulic systems with a few key differences. The reservoir is eliminated as there is no need to collect and store the air between uses in the system. Also because air is a gas it is compressible and regulators are not needed to recalculate flow, but the compressibility also means that the systems are not as stiff or strong. Pneumatic systems respond very quickly, and are commonly used for low force applications in many locations on the factory floor.
Historically, the modeling, analysis, and synthesis of suitable controllers for pneumatic actuators have been largely restricted to a classical transfer function approach that ignores nonlinearities like friction in the system.
Various software were developed for design, control and simulation of hydraulic, pneumatic, and motion control 6. Hypneu processed the information in the graphical circuit and allowed the user to assign specific element to the system, to run both steady state in a meaningful manner. Several powerful add-on packages were also available, such as Frequency Analyzer, Thermal Simulator, CAE Co-simulator, Client/Server Module, etc.
Knowledge and understanding of hydraulic and pneumatic systems and their components make engineers better qualified to performance their job in industrial. The significant feedback received from employers in industry stated that the department’s graduates need better training in hydraulics and pneumatics. As a response to that feedback, the Agricultural Engineering Department, Faculty of Engineering and Architecture, University of Khartoum has initiated its Hydraulics and pneumatics laboratory to include benches with industrial motor, pumps, cylinders and valves.

COMPUTATION AND SELECTION IN PNEUMATIC CIRCUITS

The design of pneumatic circuits depends on standard tables 8. These tables allow selecting actuators and valves where needed depend on force required and pressure allows.
Theoretical Force (Push or Extend) for a given cylinder is computed from the following expression:

Where F is force in N, D is bore diameter in mm and P is air pressure in MPa. Knowing the pressure at a compressor of 11 bar (1.1MPa), maximum pressure in the cylinder of 10 bar (1MPa), diameter of bore of 20 mm (Aa= 314.16), the computed theoretical force was 314.16 N.
Theoretical Force (Roll or Retract) for a given cylinder is computed from the following expression:

where F is force in N, D is bore diameter in mm, d is piston rod diameter in mm and P is pressure in bar. Knowing the pressure at a compressor of 11 bar (1.1MPa), maximum pressure in the cylinder of 10 bar (1 MPa), bore diameter of 20 mm, rod diameter of 8 mm (Ab=263.89), the computed theoretical force was 263.89 N.
The compressed air consumption for a given cylinder is computed from the following expression:

where Qn is compressed air consumption in L/min, Aa is piston area of in mm2, Ab is piston area of B in mm2, L is stroke of cylinder in mm, P is air pressure in MPa, and n is cycle of operation in cycle/min. Knowing the maximum pressure in the cylinder of 10 bar (1 MPa), diameter of bore of 20 mm (Aa= 314.16), bore diameter of 20 mm, rod diameter of 8 mm (Ab=263.89), cylinder stroke of 250mm, operation cycle of 2.5 cycle/min, the computed compressed air consumption was 0.719 L/min.
Pneumatic valve direct the air to actuator, they may be used in combination to provide logic function for control systems. Valves are available in different types, sizes and configuration. The flow capability of a valve is determine by using flow coefficient, Cv. Cv is USA measurement and is based on an equivalent flow of water through the valve in US gallons/minute with a pressure drop of one psi. There are several Cv formulas in use but the one used is based on the NFPA recommendation.
The formula below has limited accuracy for pressure drops greater than 15% of the inlet pressure. Correction is made for compressibility of air and temperature of 200C. The air flow (L/s) for the valve is computed using the following expression:

Where is P2 is downstream pressure in bar, dP is pressure drop across valve in bar, and Q is standard air flow in L/s.
The Kv value is similar to Cv but it corresponds to the flow of water in L/min with a 1 bar pressure drop. The formula is also restricted in its use to pressure drops less than 15% of the inlet pressure. The air flow (L/s) for the valve in term of Kv is computed using the following expression

OVERVIEW OF THE PNEUMATIC CIRCUITS

PNEUMATIC CIRCUITS LABORATORY ACTIVITY APPLICATIONS

Control of a Double Acting Cylinder

A double acting cylinder exercise was successfully designed and developed. The pneumatically double acting cylinder consisted of a commercial air compressor driven by electric motor 4 kW 3-phases @ 1440 rpm and maximum pressure of 11 bars with air reservoir having 270 L capacity, 1set of FRL unit, 2 set of mechanical operated valve 3/2 (two positions three ways), 1set of pneumatically operated valve 5/2 (two positions five ways), 1 unit of double acting mini-cylinder, and 2 set of speed controller. Figure 2.a illustrates the circuit diagram of a double acting cylinder operated pneumatically.
In the pneumatically operated double acting cylinder, compressed air is supplied from compressor (1), through FRL (2) filtered, regulated and lubricated, and distributed to foot valve (3) to start progress and give pilot signal to pilot controlled valve (4) which allow air cross (4) to speed controller (5), finally air enter to cylinder (6) to give expanding stroke, in retracting stroke to control by other position for (4) by limit switch valve (3).
The electrically operated a double acting cylinder laboratory application consisted of the same compressor, one set of FRL unit, one set of double solenoid operated valve 5/2 (two positions five ways), one set of mechanical operated valve 3/2(two positions three ways), one set of magnetic sensor, and one unit of double acting mini-cylinder. Figure
2.b illustrates the circuit diagram of a double acting cylinder, operated electrically.
In the electrically operated double acting cylinder, compressed air is supplied from compressor (1), air through cross FRL (2) filtered, regulated and lubricated, distributed and entering (3) solenoid valve to direction air , after air entering (4) speed controller and last station air entering cylinder to give expanding and retracting motion , sensor inside to give continuous motion. Figure 3 explains the path step diagram for both pneumatically and electrically operation of a double acting cylinder circuits.

Pushing Device

The pushing device application was successfully designed and developed. The pneumatically operated pushing device consisted of the air compressor, one set of FRL unit, one set of pilot operated valve 5/2 (two positions five ways), one set of mechanical operated valve 3/2 (two positions three ways), and one unit of double acting mini-cylinders. Figure 4.a illustrates the circuit diagram of a pneumatically operated pushing device.
In the pneumatically operated pushing device, compressed air is supplied from compressor (a), air through cross FRL (b) filtered, regulated and lubricated, distributed and entering (c) start valve, air across (c) to enter limit.

(A) PNEUMATICALLY OPERATED (B) ELECTRICALLY OPERATED

PATH STEP DIAGRAM OF A PUSHING DEVICE
It will send a pilot signal at the same time to (d2) to supply cylinder (e2) by air through speed controller (f4), as a result of that (e2) will make it is retracting stroke, and at the end of it is retracting stroke it will touch limit switch valve (ls2) will supply (g1 & g2), then (g1 & g2) will give a pilot signal to pilot operated valve (d1) to let air enter cylinder (e1) through speed controller (f2) to make it is retracting stroke. When (e1) reach to it is retracting it will touch limit switch (ls1) to start the progress again.
The electrically operated a pneumatic press laboratory application consisted of the same compressor, one set of FRL unit, two set of double solenoid operated valves 5/2 (two positions five ways), four set speed controller valves, four set of magnetic sensors, two set of relays, and two unit of double acting mini-cylinders. Figure 6.b illustrates the circuit diagram of a pneumatic press operated electrically.
In the electrically operated pneumatic press compressed air is supplied from compressor (a), air through cross FRL
(b) filtered, regulated and lubricated, distributed. When the push button was pressed the progress will started, the air will entered the double solenoid valve (c1) and from it through speed controller (d1) to cylinder (e1) to make it do it is an expanding stroke, at the end of it is an expanding stroke it will touch magnetic sensor (ms3), as a result of that (ms3) will send an electric signal to (c2) to let air cross it through speed controller (d3) to enter cylinder (e2), then (e2) will make it is expanding stroke and at the end of it is stroke it will touch (ms4), as a result of that (ms4) will send an electric signal to (c2) to let air a cross it through speed controller (d4) to enter (e2) to let it make it is retracting stroke, when (e2) reach the end of it is stroke it will touch (ms2), then (ms2) will send an electric signal to double solenoid valve (c1) to let air a cross it through speed controller (d2) to enter (e1) to let it make it is retracting stroke. Also there are two relays (r1 & r2) to make signal sensor regulated. Figure 7 explains the path step diagram both pneumatically and electrically operated pneumatic press.

Chapter-3 Control of Industrial Pneumatic Systems using Serial Communication Technology & Mat lab

INTRODUCTION

The current high-growth nature of digital communications demands higher speed serial communication circuits. Present day technologies barely manage to keep up with this demand, and new techniques are required to ensure that serial communication can continue to expand and grow. The goal of this work was to research, design, implement, and test high speed serial communication with pneumatic and hydraulic circuits. 1
In this paper Mat lab software is used for serial communication. The purpose of this research is only to show the serial communication technique implemented between pneumatic/ hydraulic system and computer. However it can also be done between a microcontroller and the pneumatic system, but for better control computer has been used to provide a signal (serially) to the pneumatic setup.
Here in this paper arduino microcontroller used as a mediator between computer and the pneumatic system. In fact the whole program is written in Mat lab. Mat lab will communicate with Arduino (Microcontroller) and accordingly Arduino will generate a signal at its I/O ports, which will be used to activate the solenoid valve of the pneumatic system.
Now the question is: what is the need of Arduino microcontroller if Matlab can generate a serial port without any microcontroller? The answer is: Matlab can definitely generate outputs at serial port of the computer. But there are very less I/O pins are available at computer?s own serial port, so to have more I/O pins arduino microcontroller has been attached with computer, so Matlab will communicate with Arduino instead of communicating with local serial port of the computer. Summary of the introduction in this fashion: “Matlab will control the pneumatic system through extra hardware called „Arduino?. 2-4

Fig. 1: communication between Matlab and Arduino 4

I. BLOCK DIAGRAM OF THE SYSTEM
In figure 1 two devices are shown, the first one is the computer and the second one is Arduino microcontroller (In the blue one). As mentioned in the introduction part there is a serial communication between arduino and Matlab. USB to USB cable (2.0) is used for this purpose.
In figure 2 block diagram of the system is shown, in which one can understand the flow of signal also. Having gone through the introduction part it is very much clear that programming code should have been written in Matlab.

Fig. 2: Block Diagram of the system 2

Having connected to Arduino using USB to USB cable, Matlab will give a signal to Arduino. Arduino will generate a voltage signal at its I/O pins according to the logic fade in Matlab. In fact Matlab will force Arduino to do so. Then the signal generated at the I/O pins of the arduino will travel towards the Relay unit. Relay unit will provide the amplified signal to solenoid valve. Then solenoid valve would get actuated and pneumatic system will start working. 35

I. ARDUINO MICROCONTROLLER
Arduino is a tool that makes the computers to sense and control the physical world. It’s an open-source physical computing platform based on a simple microcontroller board, and a development environment for writing software for the board.
Arduino can be used to develop interactive objects, taking inputs from a variety of switches or sensors, and controlling a variety of lights, motors, and other physical outputs. Projects of Arduino can be stand-alone, or they can be communicating with software running on the computer (e.g. Flash, Processing, MaxMSP) The boards can be assembled by hand or purchased preassembled; the open- source IDE can be downloaded for free.23

Fig.3:Arduino Micro controller3

In this research work Arduino ATMEGA168 has been utilized. It has 14 digital I/Os and 6 Analog I/Os. It works on +5volts DC, 10 bit analog to digital converter and 14kb ROM. (www. ATMEL.com). Figure 6 shows the image of an Arduino ATMEGA168 controller. 2
The Arduino is a tool. A little computer that can help designers interacts with the physical world. Ostensibly though, it?s not much more than any other similar platform; what makes it special is how it?s been designed and supported. “Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It?s intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or environments” (Arduino, 2007). The key is its intention – intended for artists and designers, two groups of people whose backgrounds aren?t necessarily technical ones (or if they are, they aren?t likely to be deep in embedded computing). So, in the city where Olivetti once stood (it is now a part of Telecom Italia), the designers of Arduino substituted corporate ownership and support with community and openness. This shift is what makes the Arduino accessible, and it is what has caused its rapid growth and popularity in the communities using it. 67.

I. SERIAL COMMUNICATION
Serial means “One after another”. Serial communication is when we transfer data one bit at a time, one right after the other. Information is passed back & forth between the computer and Arduino by, essentially, setting a pin high or low. Just like we turn an LED on and o_, we can also send data. One side sets the pin and the other reads it. MATLAB can read/send the data from/to the serial port of the computer and process it.
It is most important to understand the nature of buffer to avoid errors later while writing codes. There exists a buffer between the two events of sending and reading the data. Say a sensor is streaming back data to your program, more frequently than your program reads it. Then the data is stored to a list which we call a buffer. One writes data into it and other reads it, may be with different speeds. Buffers are of finite length.
Initially the buffer is empty. As new data values come in they get added to the bottom of the list (most recent data). If your program reads a value from the buffer, it starts at the top of the list (oldest data). Once you read a byte of data, it is no longer in the buffer. The data in the second position on the list moves up to the top position As soon as the buffer is full and more data is sent, the oldest data gets discarded to make space for new data. 1112

II. SERIAL COMMUNICATION BETWEEN MATLAB AND ARDUINO
We have to connect the Arduino board to the PC. Each serial port on the PC is labeled COM1, COM2 etc. The Arduino will be given a COM Port Number. Figure it out by following these steps:
1) Right click on “My Computer icon” and select Manage.
2) Select Device Manager in the tree view you will see on the left side in the new window opened.
3) Find and select Ports (COM& LPT) in the center panel.
4) Find lists of all the ports attached to the computer.
5) Figure out the one you are concerned with. Refresh the window. 11
First Serial port object has to be created. Serial port object is just a name given to that serial port so that can be used it in later commands.

>> s = serial (‘COM1’);
Serial Port Object: Serial-COM1 Communication Settings
Port: COM1 Baud Rate: 9600 Terminator: ‘LF’
Communication State Status: closed
Record Status: o_
Read/Write State Transfer Status: idle Bytes Available: 0
Values Received: 0
Values Sent: 0 11

I. PNEUMATIC CIRCUIT
Figure 5 shows an electro pneumatic circuit diagram developed in Atomism Studio software. In the circuit two cylinders are there among which one is double acting and another is a single acting spring return. Valves also used to control them. One is double acting solenoid operated valve (5/2) and the second is single solenoid spring return (3/2) valve.

The circuit shown in figure is used to achieve following position step diagram. Below figure shows position step diagram to be achieved. In figure 6 position step diagram is shown. Understanding of this diagram will be in this fashion. When cylinder 1 goes forward (Point 0 to 1 in the figure 6) and gets its extreme position cylinder 2 should go forward (Point 1 to 2). But immediately should get retracted (Point 2 to 3). At the same time cylinder 1 should get retracted (Point 3 to 0).
MULTI ACTUATOR CIRCUITS
1. SINGLE ACTUATOR CIRCUIT VERSUS MULTI ACTUATOR CIRCUITS

In the previous chapter, we have learnt about the various means and ways to control a single actuator circuits, both for single acting and double acting cylinders. Implementation of logic gates along with use of pressure sequence valve and time delay was systematically presented. Most of the practical pneumatic circuits use multi cylinders. They are operated in specific sequence to carry out the desired task. For example, to drill a wooden component first we need to clamp and then drill. We can only unclamp the cylinder, if and only if the drill is withdrawn away from the workpice. Here sequencing of movement of clamp cylinders and cylinder which carries the drill is important.

This sequencing is carried out by actuation of appropriate final control valves like directional control valves. The position of the cylinders is sensed by the sensors like limit switches, roller or cam operated valves. Multi cylinder pneumatics circuits can be designed in various methods. There is no universal circuit design method that suits all types of circuits. Some methods are commonly used for compound circuits but would be too expensive for simple circuits.
There are five common methods used by engineering and they are given below

• Classic method or Intuitive method

• Cascade method

• Step counter method

• Karnaugh–veitch method

• Combinational circuit design

In this chapter Classic method, cascade method and step counter methods are discussed. Chapter 8 deals with Boolean algebra, KV mapping method and combinational circuit methods. Double piloted 4/2 and 5/2 directional control valves are susceptible to signal conflicts. Cascading and Step counter method are more systematic methods than intuitive methods. Signal conflict can be eliminated by using cascade and stepper counter method.
2 CLASSIC METHOD OR INTUITIVE METHOD
In intuitive method, circuit design is done by use of general knowledge of pneumatics following the sequence through intuitively.
In general, steps involves
• Write down sequence and draw motion diagrams
• Draw in cylinders and control valves
• Complete circuits intuitively.

Coordinated and sequential motion control. In majority of the pneumatic applications more than one cylinder is used. The movement of these cylinders are coordinated as per the required sequence. Sensors are used for confirming the cylinder position and the resultant actuation of the final control element. Normally limit switches are used. The activation of limit switches of different cylinders will provide set or reset signal to the final control valves for further controlling the movement of various cylinders. The limit switches have to be arranged in the proper location with the help of motion diagram

Demonstration of Classic method In order to develop control circuitry for multi cylinder applications, it is necessary to draw the motion diagram to understand the sequence of actuation of various signal input switches-limit switches and sensors. Motion diagram represents status of cylinder position -whether extended or retracted in a particular step

Example 1: In a press shop, stamping operation to be performed using a stamping machine. Before stamping, workpice has to be clamped under stamping station. Then stamping tool comes and performs stamping operation. Work piece must be unclamped only after stamping operation

Step 1: Write the statement of the problem: Let A be the clamping cylinder and B be the stamping cylinder as shown in the Figure xxx. First cylinder A extends and brings under stamping station where cylinder B is located. Cylinder B then extends and stamps the job. Cylinder A can return back only cylinder B has retracted fully.

Step 2: Draw the positional layout. (Figure 1.1)

Step3: Represent the control task using notational form

Cylinder A advancing step is designated as A+
Cylinder A retracting step is designated as A
Cylinder B advancing step is designated as B+
Cylinder B retracting step is designated as B

Therefore, given sequence for clamping and stamping is A+B+B-A

Step 6: Analyse and Draw Pneumatic circuit.

Step 6.1 Analyse input and output signals.

Input Signals

Cylinder A – Limit switch at home position ao
Limit switch at home position a1
Cylinder B – Limit switch at home position bo
Limit switch at home position b1
Output Signal
Forward motion of cylinder A (A+)
Return motion of cylinder A (A-)
Forward motion of cylinder B (B+)
Return motion of cylinder B (B+)
Step 6.2 using the displacement time/step diagram link input signal and output signal. (Figure 1.4)
Usually start signal is also required along with a0 signal for obtaining A+ motion.
1. A+ action generates sensor signal a1, which is used for B+ motion
2. B+ action generates sensor signal b1, which is used for B- motion
3. B- action generates sensor signal b0, which is used for A- motion
4. A- action generates sensor signal a0, which is used for A+ motion above information (given in 6.2) is shown below graphically

Step 7 Draw the power circuit (Figure 1.5)
i) Draw the cylinders A (1.0) and B (2.0).
ii) Draw the DCVs 1.1 and 2.1 in unactuated conditions.
iii) Mark the limit switch positions for cylinders A (1.0) and B (2.0).

Step 9 Analysis of pneumatic circuit
1. When the start button is pressed, the signal appears at port 14 of valve 1.1 through limit switch signal a0.
2. Check for the presence of the signal at the other end (12) of valve 1.1. Notice that the signal is also present at port 12 of valve 1.1. (Because Bo is also pressed).
This results in signal conflict and valve 1.1 is unable to move. (Figure 1.7)

3. Let us assume for time being, Bo is somehow disengaged so that valve 1.1 can switch over and consequently cylinder A can extend. When the start button is pressed. (Figure 1.8)

4. When cylinder A fully extends, it generates a limit switch signal a1, which is applied to port 14 of the valve 2.1.
5. Check for the presence of the signal at the other end (12) of valve 2.1. Signal is not present at port 12 of valve 2.1 and hence there is no signal conflict
6. Signal applied to port 14 of the valve 2.1 causes the shifting of DCV 2.1 and cylinder B extends.
7. When cylinder B fully extends, it generates a limit switch signal b1, which is applied to port 12 of valve 2.1 1.
Check for the presence of the signal at the other end of 14 of valve 2.1. It can be seen that signal is also present at the port 14 of valve 2.1(because a1 is also pressed). This results in signal conflict and valve 2.1 is unable to move (Figure 1.9)

9. Let us assume for time being, b1 is somehow disengaged so that valve 2.1 can switch over and consequently cylinder B can retract.(Figure 1.10)

10. When the cylinder B is fully retracted, it generates a limit switch signal b0, which is applied to port 12 of the valve 1.1. (Figure 1.11)

11. Check for the signal at the other end 14 of the valve 1.1 Notice that signal is not present at port 14 of the valve 1.1 and hence there is no signal conflict. So valve 1.1 can switch over and Cylinder A can retract.

Example 2 : Two cylinders are used to transfer parts from a magazine onto a chute (Figure 1.12). When a push button is pressed, the first cylinder extends. Pushing the part from the magazine and positions it in preparation for transfer by the second cylinder onto the out feed chute. Once the part is transferred, the first cylinder retracts, followed by the second. Confirmation of all extended and retracted positions are required.

Step 1: Write the statement of the problem: Let A be the first cylinder (Pushing) and B be second cylinder (feeding) as shown in the Figure xxx. First cylinder A extends and brings under stamping station where cylinder B is located. Cylinder B then extends and stamps the job. Cylinder A can return back only cylinder B has retracted fully.

Step 2: Draw the positional layout. (Figure 1.13)

Step3: Represent the control task using notational form
Cylinder A advancing step is designated as A+
Cylinder A retracting step is designated as A
Cylinder B advancing step is designated as B+
Cylinder B retracting step is designated as B
Therefore, given sequence for clamping and stamping is A+B+A-B

Step 4 Draw the Displacement –step diagram (Figure 1.14)

Step 6: Analyse and Draw Pneumatic circuit.
Step 6.1 Analyse input and output signals.
Input Signals
Cylinder A – Limit switch at home position ao
Limit switch at home position a1
Cylinder B – Limit switch at home position Bo
Limit switch at home position b1
Output Signal
Forward motion of cylinder A (A+)
Return motion of cylinder A (A-)
Forward motion of cylinder B (B+)
Return motion of cylinder B( B+)
Step 6.2 using the displacement time/step diagram link input signal and output signal. (Figure 1.16)
Usually start signal is also required along with b0 signal for obtaining A+ motion.
1. A+ action generates sensor signal a1, which is used for B+ motion
2. B+ action generates sensor signal b1, which is used for A- motion
3. A- action generates sensor signal a0, which is used for B- motion
4. B- action generates sensor signal b0, which is used for B- motion
Above information (given in 6.2) is shown below graphically

Step 7 Draw the power circuit (Figure 1.18)
i) Draw the cylinders A(1.0) and B(2.0).
ii) Draw the DCVs 1.1 and 2.1 in unactuated conditions
iii) Mark the limit switch positions for cylinders A(1.0) and B(2.0).

Step 8 Draw the control circuit (Figure 1.19)

Step 9 Analysis of pneumatic circuit
1. When the start button is pressed, the signal appears at port 14 of valve 1.1 through limit switch signal b0.
2. Check for the presence of the signal at the other end (12) of valve 1.1. Notice that the signal is not present at port 12 of valve 1.1. (Because b1 is not pressed). There is no signal conflict and valve 1.1 is able to move. So A advances to forward position.
3. When cylinder A fully extends, it generates a limit switch signal a1, which is applied to port 14 of the valve 2.1. Cylinder B advances to forward position.

5. Check for the presence of the signal at the other end (12) of valve 2.1. Signal is not present at port 12 of valve 2.1 (because a0 is not pressed, A is already in extended position now) and hence there is no signal conflict
6. Signal applied to port 14 of the valve 2.1 causes the shifting of DCV 2.1 and cylinder B extends.
7. When cylinder B fully extends, it generates a limit switch signal b1, which is applied to port 12 of valve 1.1 . Cylinder A returns and ao is pressed. There is no signal conflict, as ao and a1 are mutually exclusive signals.
8. When the cylinder A is fully retracted, it generates a limit switch signal a0, which is applied to port 12 of the valve 2.1. Cylinder B retracts. All five sequence of operations are shown in Figure 1.20 to Figure 1.24

Elimination of Signal Conflict Various methods are used to solve problem of signal conflicts in multi cylinder circuits.
a) Idle return roller
b) Reversing valves ( memory valves)
c) Modules as combination of valves cascading method uses the revering valves (also known group changing valves) and Step counter method uses modular valves.
Both methods are discussed in subsequent section in this chapter.

Use of Idle Return Rollers. An idle-return roller valve consists of a 3/2 DCV fitted with an idle return roller mechanism. The two designs of the idle roller is shown in Figure 1.25

The action of the idle return roller valve can be understood using the Figure 1.26 The idle return roller may be positioned in the control system so that when the cylinder extends, the piston passes over the idle – roller mechanism of the valve, thus activating the valve. (Figure 1.26a ), but also permitting the valve to be deactivated immediately when the piston moves to the extreme end position (Figure 1.26b). As a result, the valve generates a short output pulse during the forward motion of the cylinder. The idle return mechanism also allows the cylinder to retract without reactivating the valve (Figure 1.26c and Figure 1.26d). Hence, in the end position or during the return motion of the piston, the valve does not gets actuated, and no output signal is produced. For the generation of short output pulse by the idle-return roller valve during the return motion of the cylinder, this valve may be positioned in the opposite direction as compared to the case during the forward motion of the cylinder. In the previous sequence problem, we have identified that roller valves b1 and a1 are responsible for signal conflicts.
To eliminate the problem of signal conflicts the roller valve b1 and a1 to be replaced by idle return rollers. Drawbacks of idle –return rollers.
1. This method is not reliable
2. End position cannot be sensed accurately
3. Fast control system cannot be set up.

Example 3: Develop Pneumatic circuit for A+ B+ B- A- sequence. Avoid signal conflict using idle – return roller. Figure 1.27 shows the circuit for getting the control sequence A+ B+ B- A- using the idle –return rollers at the position bo and a1. The roller valves at position a0 and b1 need be replaced with the idle return rollers as these valves do not cause signal conflicts for the given sequence circuit.

1.1 CASCADE METHOD
A Bi-stable memory valve or reversing valve can be used to eliminate signal conflicts. Signal conflict is avoided by allowing the signal to be effective only at times when they are needed. Two of the possible designs are possible.

i) Cascade method
ii) Shift register method

1.1.1 Demonstration of Cascade method
In order to develop control circuitry for multi cylinder applications, as done before in classic method, it is necessary to draw the motion diagram to understand the sequence of actuation of various signal input switches-limit switches and sensors. Motion diagram represents status of cylinder position – whether extended or retracted in a particular step

Step 1: Write the statement of the problem: First cylinder A extends and brings under stamping station where cylinder B is located. Cylinder B then extends and stamps the job. Cylinder A can return back only cylinder B has retracted fully.

Step 2: Draw the positional layout. (Figure 1.28)

Step3: Represent the control task using notational form
Cylinder A advancing step is designated as A+
Cylinder A retracting step is designated as A
Cylinder B advancing step is designated as B+
Cylinder B retracting step is designated as B
Given sequence for clamping and stamping is A+B+B-A
Step 4 Draw the Displacement –step diagram (Figure 1.29) Step 5 Draw the Displacement –time diagram (Figure 1.30)

Step 5 Draw the Displacement –time diagram (Figure 1.30)

Step 6: Analyse and Draw Pneumatic circuit.
Step 6.1 Analyse input and output signals.
Input Signals
Cylinder A – Limit switch at home position ao
Limit switch at home position a1
Cylinder B – Limit switch at home position bo
Limit switch at home position b1
Output Signal
Forward motion of cylinder A ( A+)
Return motion of cylinder A (A-)
Forward motion of cylinder B ( B+)
Return motion of cylinder B( B+)

Step 6.2 Using the displacement time/step diagram link input signal and output signal. (Figure 1.31)
Usually start signal is also required along with a0 signal for obtaining A+ motion.
1. A+ action generates sensor signal a1, which is used for B+ motion
2. B+ action generates sensor signal b1, which is used group changing.
3. B- action generates sensor signal b0, which is used for A- motion
4. A- action generates sensor signal a0, which is used for group changing Above information (given in 6.2) is shown below graphically

Step 7 Draw the power circuit (Figure 1.32)
i) Divide the given circuits into groups. Grouping should be done such that there is no signal conflict. Do not put A+ and A- in the same group. Similarly B+ and B- should not be put in the same group. In other word A+ and A- should belong to different group to avoid signal conflict. In our example of A+ B+ B- A- we can group as

ii) Choose the number of group changing valve = no of groups -1 In our example, we have 2 groups so we need one group changing valve Connect the group changing valve as follows. From the figure it is clear that when the control signals I and II are applied to group changing valve, the air (power) supply changes from Group 1(G1) to Group 2 (G2)

iii) Arrange the limit switch and start button as given below (Figure 1.33)

iv) Draw the power circuit (Figure 1.34)

Step 8 Draw the control circuit (Figure 1.35)

Step 9 Analysis of pneumatic circuit
1. Assume that air is available in the line G2 to start with. (Say from last operation)
2. When the start button is pressed, Air supply from Group G2 is directed to line 2 through actuated limit switch a0. Now the air available in line 2, actuates the Group changing valve (GCV) to switch over to position I. This switching of the GCV causes air supply to change from G2 to G1.
3. Now the air is available in line G1. The air supply from group G1 is directed to port 14 of the valve 1.1. As there is no possibility of signal conflict here, valve 1.1 switches over causing the A+ action.
4. Sensor a1 is actuated as the result of A+ action, allowing the air supply from the Group G1 to reach to line 1 through a1. Now the air available reaches port 14 of valve 2.1. As there is no possibility of signal conflict here, valve 2.1 switches over, causing B+ action automatically. 5. Sensor b1 is actuated as result of B+ action, allowing the air supply in line 3. Air from line 3 allows the air to reach port 12 of Group changing valve (also called reversing valve). As a result, the Group changing valve switches over, causing the group supply to change from G1 to G2.
6. Now the air is available in G2. Air from G2 acts on port 12 of the Valve 2.1. As there is no possibility of signal conflict here, valve 2.1 switches over, causing B- action automatically.
7. Sensor is actuated as the result of B- action. Now the air is available in line 4.Air from line 4 reach port 12 of the valve 1.1 , As there is no possibility of signal conflict here, valve 2.1 switches over , causing A- action automatically. The cascade system provides a straightforward method of designing any sequential circuit. Following are the important points to note: a) Present – the system must be set to the last group for start-up b) Pressure drop- Because the air supply is cascaded, a large circuit can suffer from more pressure drop. c) Cost – Costly due to additional reversing valves and other hardware.

Chapter 6 CANVAS IMAGE

Advantages

? Low cost Solutions
? Programmable
? Open Source (No License Required)
? USB Interfacing
? Windows and LINUX Supported

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