• Subject - Mechatronics

Summer -2018 Solution

• Q .01 a) What are requirements of control system. Explain different types of control systems

with suitable example. 6

Ans- Stability, accuracy and speed of response are the three requirement s of a

control system.

Stability:

A system is to be stable if the output of the system after fluctions, variation or

oscillation, if any, settles at a reasonable value for any change in input or change in

disturbance.

Accuracy:

A system is said to be 100 percent accurate if the error ( different between input and

output ) is zero. An accurate system is costly. There is no point in going for 100

percent accurate system when that much of accuracy is not really required.

Example of accuracy:

When a variation of say 0.2 degree centigrade cannot be sensed by a human being,

there is no need to have a home heating system of temperature variation equal to

zero.

Speed of Response:

This refers to time taken by the system to respond to the given input and give that as

the output. Theoritically the speed of response should be infinity, that is, the system

should have an instantaneous response. This requirement is prime concern with

follow-up systems.

Any ideal system is perfectly stable, 100 percent accurate and has instantaneous

speed of response. Unfortunately, the requirements are incompatiable. Hence there

should be a compromise between these requirements.

There are two types of control systems namely:

• Open loop control systems (non-feedback control systems)

• Closed loop control systems (feedback control systems)

• Open loop control system

•

If in a physical system there is no automatic correction of the variation in its output, it

is called an open loop control system. That is, in this type of system, sensing of the

actual output and comparing of this output (through feedback) with the desired input

doesnot take place. The system on its own is not in a position to give the desired

output and it cannot take into account the disturbances. In these systems, the

changes in output can be corrected only by changing the input manually.

These systems are simple in construction, stable and cost cheap. But these systems

are inaccurate and unreliable. Moreover these systems donot take account of

external disurbances that affect the output and they donot initiate corrective actions

automatically.

Examples of open loop control systems:

• Automatic washing machine

• traffic signal system

• home heating system( without sensing, feedback and control)

Closed loop control system

A closed loop control system is a system where the output has an effect upon the input quantity in such a manner as to maintain the desired output value.

An open loop control system becomes a closed loop control system by including a

feedback. This feedback will automatically correct the change in output due to

disturbances. This is why a closed loop control system is called as an automatic

control system. The block diagram of a closed loop control system is shown in figure.

In a closed loop control system, the controlled variable (output) of the system is

sensed at every instant of time, feedback and compared with the desired input

resulting in an error signal. This error signal directs the control elements in the

system to do the necessary corrective action such that the output of the system is

obtained as desired.

The feedback control system takes into account the disturbances also and makes

the corrective action. These control systems are accurate, stable and less affected

by noise. But these control systems are sophisticated and hence costly. They are

also complicated to design for stability, give oscillatory response and feedback

brings down the overall gain of the control system.

Q. 01. b) Explain the following mechatronic system applications: a) Boat Auto Pilot b) High speed Tilting

train

Ans- A) BOAT AUTO PILOT

Autopilots are self-steering devices

for power or sailboats. They can hold your vessel on a pre-set compass course (even the most

basic pilots do this) and sophisticated pilots that connect to GPS receivers or gather data from

your boat's instruments can handle a lot more advanced tasks.

A boat autopilot is an electronic device capable of steering a boat on a preset course, taking the place of a crew member. On NauticExpo, this equipment is for use on leisure craft.

Applications

Autopilots are extremely useful on long passages or when sailing single- or short-handed.

Technologies

Most autopilots include the following components: - An electro-hydraulic pump and cylinder constitute the system's mechanical arm. The cylinder actuates the helm according to instructions from the electronic control unit. - The control unit analyzes input data and sends instructions to the pump/cylinder. - Sensors read the current course from a gyrocompass, as well as the helm position. - A control screen is used to configure the autopilot and indicate the course to be followed. Some autopilots are better suited to motor vessels, others to sailboats. They also may vary by steering system: tiller, wheel, quadrant, belt, etc. Computer control of the autopilot is also possible via an NMEA-compatible electronic network.

An autopilot is a combination of electric or electronic navigation tools that steer a vessel

without continual hands-on involvement. Autopilots allow short- or single-handed sailors

and boaters to leave the helm to trim or rig sails, adjust lines, set anchor, eat without

interruption, take short naps, or other activities while not at the helm.

B) HIGH SPEED TILTING TRAIN- Tilting Train consists of tilting mechanism that

enables to increase the speed on regular tracks. In the upper part of tilting trains that is

in which the passengers are seated can be tilted sideways. During the motion of the

train if the train has to

steer to left in a left turning the coaches of the train will be tilted to the left in order to

compensate the centrifugal push to the right and conversely during the right turn. Tilting

trains can be classified into different categories according the features of their tilting

system. On every types of tilting trains the tilting systems shall perform three main

functions: first, they have to identify accurately and without delay the initial position of

curve transitions, then second they have to tilt the car body according to the tilting

algorithm provided for the system and finally they have to verify that the provided

amount of tilt corresponds to the tilt demand.

PRINCIPAL/ CONCEPT/CAR BODY OF TILTING TRAINS

The active tilt relies on active technology, controlled by sensors and electronics and executed by an actuator, usually hydraulic or electric. Tilt as such has normally not an impact on safety of actively tilted train, as the centre of gravity does not essentially change its lateral position. The passive tilt relies on physical laws with a tilt centre located well above the centre of gravity of the car body. In a curve, under the influence of centrifugal force, the lower part of the car body then swings outwards. It should be noted that passive tilt has a negative impact on safety due to the lateral shift of the centre of gravity of the car body.

A train and its passengers are subjected to lateral forces when the train passes horizontal curves. Car body roll inwards, however, reduces the lateral acceleration felt by the passengers, allowing the train to negotiate curves at higher speed with maintained ride comfort [1]. Trains capable of tilting the car bodies inwards in curves are called tilting trains. Tilting trains can be divided in two groups: the naturally tilted trains and the actively tilted trains Natural tilt relies on physical laws with a tilt center located

well above the Center of gravity of the car body. In a curve, under the influence of lateral acceleration, the lower part of the car body then swings outwards. Active tilt may have car body center of gravity and rotation center at about the same height. This form of tilt does not normally have an impact on the safety of the train, since the center of gravity does not essentially change its (lateral) position. Active tilt relies upon control technology involving sensors and electronics and is executed by an actuator, usually hydraulic or electric, without actuation there is no significant tilt action.

Q.02. Explain mechatronic design process?

Ans- Mechatronics is a methodology used for the optimal design of electromechanical products. A methodology is collection of practices, procedures and rules used by those who work in particular branch of knowledge or discipline. The familar technological disciplines include thermodynamics, electrical engineering, computer science and mechanical engineering, to name several. The mechatronical system is multi-disciplinary, embodying four fundamental disciplines: electrical, mechanical, computer science and information technology. The mechatronic design methodology is based on a concurrent, instead of sequential, approach to discipline design, resulting in products with more synergy. Mechatronics is a design philosophy, an integrating approach to engineering design. The primary factor in mechatronics is the involvment of these areas throughout the design process. Through a mechanism of simulating interdisciplinary ideas and techniques, mechatronics provides ideal conditions to raise the synergy, thereby providing a catalytic effect for the new solutions to technically complex situations. An importatant characteristic of mechatronical devices and systems is their built-in intelligence, which results through a combination of precision mechanical and electrical engineering and real-time programming integrated with the design process. Mechatronics makes possible the combination of actuators, sensors, control systems, and computers in the design process. Starting with the basic design, and progressing through the manufacturing phase, mechatronic design optimizes the parameters at each phase to produce a quality product in a short cycle time. Mechatronics uses the control systems in providing a coherent framework of component interactions for system analysis. The integration within a mechatronical system is performed through the combination of hardware (components) and software (information processing). Hardware integration results from designing the mechatronical system as an overal system and bringing together the sensors, actuators, and microcomputers into the mechanical system. Software integration is primarily based on advanced control functions. The first step in the focused development of mechatronical systems is to analyze the customer and the technical enviroment in which the system is integrated. Complex technical systems designed to solve problems tend to be a combination of mechanical, electric, fluid, power, and thermodynamic parts with hardware in digital and analog form coordinated by complex software. Typical mechatronical systems gather data and information from their technical enviroment using sensors. The next step is to use elaborate ways of modeling and description methods to cover all subtasks of this system in an integrated manner.

Q- 02 b) Mechatronics is synergic integration of mechanical engineering with electronics

and control engineering for design and manufacture of products. Justify the statement

Ans- echatronics: the synergistic integration of mechanical engineering with electronics

and control engineering. ... The input signal conditioning and interfacing system provide

connection between the control circuits and input/ output system. The overall control of

the system is carried out by digital controls.

Mechatronics engineering may be regarded as a modern approach to automation

techniques

for the broadly defined needs of engineering and education.

It can be assumed that mechatronics is an interdisciplinary field of science and

technology,

dealing with general problems of mechanics, electronics and informatics. However, it

contains too many related mechatronics areas that form the foundation of

mechatronics and cover many well-known disciplines such as electrical engineering,

power

electronics, digital technology, microprocessor technology, and other techniques.

Mechatronics

engineering provides an opportunity, not only humanization of machines, but also it

changes

the mindset and the approach to technological issues and most importantly teaching

new

technologies and ways of acquiring knowledge and skills. The most important feature

of mechatronic devices is the ability to process and communicate information accurately

in a

form of different types of signals (mechanical, electrical, hydraulic, pneumatic, optical,

chemical, biological), with high level of automation of these devices.The course aims to

produce students who can design and develop smart machines and use their

multidisciplinary skills to meet growing demands of an industry.

Mechatronics Engineering is offered with an integrated curriculum to provide a broad-

based

education in the basic principles of electrical, electronics, mechanical, control,

instrumentation

and computer engineering. Broad range of topic covered include: Design of machine

elements,

Analog and Digital system Design, Signal Processing, Measurements, Material Science,

Mechanical Vibration, Kinematics of Machinery, PLC Programming, Control Systems,

Microcontrollers, Hydraulic and Pneumatic Systems, Industrial Robotics, Embedded

Systems,

Nanotechnology and Computer Integrated Manufacturing.Application in Industry Sectors

Mechatronics is a multidisciplinary field of engineering with far reaching applications on

various

sectors of the society. Mechatronics plays a key role in the development of tomorrow’s

products by being at the forefront of cutting-edge designs. Today, Mechatronics

Engineering

has gained much recognition and importance in the industrial world and has become an

engineering discipline on high demand. Mechatronics may be viewed as a modern

mechanical

engineering design in the sense that it is the synergistic integration of mechanical

engineering

with electronics and intelligent computer control in the design and manufacturing that

aims at

improving and/or optimizing its functionality.

Q.03 a) Explain interfacing requirements in Data Acquisition Systems.

Ans- Data acquisition systems, as the name implies, are products and/or processes

used to collect information to document or analyze some phenomenon. In the simplest

form, a technician logging the temperature of an oven on a piece of paper is performing

data acquisition. As technology has progressed, this type of process has been simplified

and made more accurate, versatile, and reliable through electronic equipment.

Equipment ranges from simple recorders to sophisticated computer systems. Data

acquisition products serve as a focal point in a system, tying together a widevariety of

products, such as sensors that indicate temperature, flow, level, or pressure.Recorders

and Dataloggers are products used with sensors to document information relating to a

process. Recorders usually have a pen that deflects as a percentage of input span,

while paper moves beneath it at a defined speed in relation to time. The recorder output

is an easy-to-read, continuous trend line. Dataloggers typically print the actual value of

the input with a time stamp. The advantages of the datalogger include less paper

usage, higher resolution of the reading, and less chance of misinterpretation of the data.

Hybrid recorders are instruments that have both trend recording and datalogging ability.

Some of these units also include features such as math calculations and communication

ability to transfer data to a host computer for further analysis.

Communication-Based data acquisition products, those that interface with a computer

through a communication port, can range from dataloggers to remote intelligent control

systems. The most common communication interface for short distances is RS-232.

RS-232 defines serial communication for one device to one computer communication

port, with speeds up to 115 K baud (bits per second). Typically 7 or 8 bits (on/off signal)

are transmitted to represent a character or digit. The ASCII code provides a standard

definition allowing alphanumeric characters to be represented by a string of bits. Other

serial communication interfaces includeRS-422 and RS-485. Both provide

communicate longer distances with multiple units on the line. Two common parallel

communication interfaces are the Centronic and IEEE488. Parallel interfaces

communicate data at 8 or more bits at one time. The Centronic interface is the common

parallel interface used to connect printers to a computer. The IEEE488 interface (also

sometimes known as GPIB or HPIB) provides a high speed parallel interface forup to 15

devices

Q- 03 b) What is digital communication? Explain modes of serial communication

Ans- Data can be transmitted between a sender and a receiver in two main ways: serial and parallel. Serial communication is the method of transferring one bit at a time through a medium. ... For this reason, the internal connections in a computer, ie: the busses, are linked together to allow parallel communication.

Definition - What does Serial Communication mean?

Serial communication is a communication technique used in telecommunications wherein data transfer occurs by transmitting data one bit at a time in a sequential order over a computer bus or a communication channel. It is the simplest form of communication between a sender and a receiver. Because of the synchronization difficulties involved in parallel communication, along with cable cost, serial communication is considered best for long-distance communication.

erial communication is the most widely used approach to transfer information between data processing equipment and peripherals. In general, communication means interchange of information between individuals through written documents, verbal words, audio and video lessons.

Every device might it be your Personal computer or mobile runs on serial protocol. The protocol is the secure and reliable form of communication having a set of rules addressed by the source host (sender) and destination host (receiver). To have a better insight, I have explained the concept of serial communication.

In embedded system, Serial communication is the way of exchanging data using different methods in the form of serial digital binary. Some of the well-known interfaces used for the data exchange are RS-232, RS-485, I2C, SPI etc.

n serial communication, data is in the form of binary pulses. In other words, we can say Binary One represents a logic HIGH or 5 Volts, and zero represents a logic LOW or 0 Volts. Serial communication can take many forms depending on the type of transmission mode and data transfer. The transmission modes are classified as Simplex, Half Duplex, and Full Duplex. There will be a source (also known as a sender) and destination (also called a receiver) for each transmission mode.

The Simplex method is a one-way communication technique. Only one client (either the sender or receiver is active at a time). If a sender transmits, the receiver can only accept. Radio and Television transmission are the examples of simplex mode.

In Half Duplex mode, both sender and receiver are active but not at a time, i.e. if a sender transmits, the receiver can accept but cannot send and vice versa. A good

example is an internet. If a client (laptop) sends a request for a web page, the web server processes the application and sends back the information.

The Full Duplex mode is widely used communication in the world. Here both sender and receiver can transmit and receive at the same time. An example is your smartphone.

Q-04 a) What is Digital to Analog converter? Explain adder type Digital to Analog

convertor?

Ans- A D/A Converter is used when the binary output from a digital system is to be

converted into its equivalent analog voltage or current. The binary output will be a

sequence of 1’s and 0’s. Thus they ma be difficult to follow. But, a D/A converter help

the user to interpret easily.

Basically, a D/A converter have an op-amp. It can be classified into 2 types. They are

Digital to Analog Converter using Binary-Weighted Resistors

A D/A converter using binary-weighted resistors is shown in the figure below. In the

circuit, the op-amp is connected in the inverting mode. The op-amp can also be

connected in the non-inverting mode. The circuit diagram represents a 4-digit converter.

Thus, the number of binary inputs is four.

e know that, a 4-bit converter will have 24 = 16 combinations of output. Thus, a

corresponding 16 outputs of analog will also be present for the binary inputs.

Four switches from b0 to b3 are available to simulate the binary inputs: in practice, a 4-

bit binary counter such as a 7493 can also be used.

Weighted resistor digital to analog Converter is a very basic D/A converter. By using

simple resistor network we can easily build that. As we discuss earlier about how digital

to analog converters works you may refer that first. Let us consider a N-bit straight

binary resistor network, which produces a current I corresponding to logic 1 at the most

significant bit, I/2 corresponding to logic 1 at the next lower bit, I/22 for the next lower bit

and so on, and I/ 2N–1 for logic 1 at the least significant bit position. Now the total

current thus produced by that resistive network will be proportional to the digital inputs,

which we want to convert in equivalent analog signal. Farther this current can be

converted to voltage with the help of a converter circuit by an using operational amplifier

(OP AMP). Finally then we get the produced voltage is analog in nature and will be

proportional to the digital inputs.

Q.04 b) Explain impedance matching in mechanical system? State effects of improper

impedancematching

Ans- mpedance is the opposition by a system to the flow of energy from a source. For

constant signals, this impedance can also be constant. For varying signals, it usually

changes with frequency. The energy involved can be electrical, mechanical, acoustic,

magnetic, or thermal. The concept of electrical impedance is perhaps the most

commonly known. Electrical impedance, like electrical resistance, is measured in ohms.

In general, impedance has a complex value; this means that loads generally have a

resistance component (symbol: R) which forms the real part of Z and a reactance

component (symbol: X) which forms the imaginary part of Z.

In simple cases (such as low-frequency or direct-current power transmission) the

reactance may be negligible or zero; the impedance can be considered a pure

resistance, expressed as a real number. In the following summary we will consider the

general case when resistance and reactance are both significant, and the special case

in which the reactance is negligible.

Reflection-less matching

Impedance matching to minimize reflections is achieved by making the load impedance

equal to the source impedance. If the source impedance, load impedance and

transmission line characteristic impedance are purely resistive, then reflection-less

matching is the same as maximum power transfer matching.[1]

Maximum power transfer matching Complex conjugate matching is used when

maximum power transfer is required, namely

{\displaystyle Z_{\mathsf {load}}=Z_{\mathsf {source}}^{*}\,} Z_{{\mathsf

{load}}}=Z_{{\mathsf {source}}}^{*}\,

where a superscript * indicates the complex conjugate. A conjugate match is different

from a reflection-less match when either the source or load has a reactive component.

If the source has a reactive component, but the load is purely resistive, then matching

can be achieved by adding a reactance of the same magnitude but opposite sign to the

load. This simple matching network, consisting of a single element, will usually achieve

a perfect match at only a single frequency. This is because the added element will

either be a capacitor or an inductor, whose impedance in both cases is frequency

dependent, and will not, in general, follow the frequency dependence of the source

impedance. For wide bandwidth applications, a more complex network must be

designed. Power transfer Main article: Maximum power theorem Whenever a source of

power with a fixed output impedance such as an electric signal source, a radio

transmitter or a mechanical sound (e.g., a loudspeaker) operates into a load, the

maximum possible power is delivered to the load when the impedance of the load (load

impedance or input impedance) is equal to the complex conjugate of the impedance of

the source (that is, its internal impedance or output impedance). For two impedances to

be complex conjugates their resistances must be equal, and their reactances must be

equal in magnitude but of opposite signs. In low-frequency or DC systems (or systems

with purely resistive sources and loads) the reactances are zero, or small enough to be

ignored. In this case, maximum power transfer occurs when the resistance of the load is

equal to the resistance of the source (see maximum power theorem for a mathematical

proof).

Impedance matching is not always necessary. For example, if a source with a low

impedance is connected to a load with a high impedance the power that can pass

through the connection is limited by the higher impedance. This maximum-voltage

connection is a common configuration called impedance bridging or voltage bridging,

and is widely used in signal processing. In such applications, delivering a high voltage

(to minimize signal degradation during transmission or to consume less power by

reducing currents) is often more important than maximum power transfer.

In older audio systems (reliant on transformers and passive filter networks, and based

on the telephone system), the source and load resistances were matched at 600 ohms.

One reason for this was to maximize power transfer, as there were no amplifiers

available that could restore lost signal. Another reason was to ensure correct operation

of the hybrid transformers used at central exchange equipment to separate outgoing

from incoming speech, so these could be amplified or fed to a four-wire circuit. Most

modern audio circuits, on the other hand, use active amplification and filtering and can

use voltage-bridging connections for greatest accuracy. Strictly speaking, impedance

matching only applies when both source and load devices are linear; however, matching

may be obtained between nonlinear devices within certain operating ranges.

Q.05 a) Explain the principle and working of Brushless D. C. Motor?

Ans- Electrical equipment often has at least one motor used to rotate or displace an

object from its initial position. There are a variety of motor types available in the market,

including induction motors, servomotors, DC motors (brushed and brushless), etc.

Depending upon the application requirements, a particular motor can be selected.

However, a current trend is that most new designs are moving towards Brushless DC

motors, popularly known as BLDC motors.

This article will concentrate on the following aspects of BLDC motor design:

Construction of the BLDC motor

Operation of the BLDC motor

Torque and Efficiency requirements

Comparison with Induction and Brushed DC motors

Selection criteria for a BLDC motor

Motor control – Speed, Position and Torque, to be covered in Part II of this article.

Construction -BLDC motors have many similarities to AC induction motors and brushed

DC motors in terms of construction and working principles respectively. Like all other

motors, BLDC motors also have a rotor and a stator.Similar to an Induction AC motor,

the BLDC motor stator is made out of laminated steel stacked up to carry the windings.

Windings in a stator can be arranged in two patterns; i.e. a star pattern (Y) or delta

pattern (∆). The major difference between the two patterns is that the Y pattern gives

high torque at low RPM and the ∆ pattern gives low torque at low RPM. This is because

in the ∆ configuration, half of the voltage is applied across the winding that is not driven,

thus increasing losses and, in turn, efficiency and torque.teel laminations in the stator

can be slotted or slotless as shown in Figure 2. A slotless core has lower inductance,

thus it can run at very high speeds. Because of the absence of teeth in the lamination

stack, requirements for the cogging torque also go down, thus making them an ideal fit

for low speeds too (when permanent magnets on rotor and tooth on the stator align with

each other then, because of the interaction between the two, an undesirable cogging

torque develops and causes ripples in speed). The main disadvantage of a slotless core

is higher cost because it requires more winding to compensate for the larger air

gap.Proper selection of the laminated steel and windings for the construction of stator

are crucial to motor performance. An improper selection may lead to multiple problems

during production, resulting in market delays and increased design costs.

rotor- The rotor of a typical BLDC motor is made out of permanent magnets. Depending

upon the application requirements, the number of poles in the rotor may vary.

Increasing the number of poles does give better torque but at the cost of reducing the

maximum possible speed.

Another rotor parameter that impacts the maximum torque is the material used for the

construction of permanent magnet; the higher the flux density of the material, the higher

the torque.

Q-05 b) Explain how PWM technique is used to control the speed of D.C. motor.

Ans- By increasing or decreasing pulse width, the controller regulates energy flow to the

motor shaft. ... The circuit is used to control speed of DC motor by using PWM

technique. Series Variable Speed DC Motor Controller 12V uses a 555 timer IC as a

PWM pulse generator to regulate the motor speed DC12 Volt.

DC motor speed control is one of the most useful features of the motor. By controlling

the speed of the motor, you can vary the speed of the motor according to the

requirements and can get the required operation.

When the conductor (armature) is supplied with a current, it produces its own magnetic

flux. The magnetic flux either adds up to the magnetic flux due to the field windings at

one direction, or cancels the magnetic flux due to field windings. The accumulation of

magnetic flux at one direction compared to the other exerts a force on the conductor,

and therefore, it starts rotating.

According to Faraday’s law of electromagnetic induction, the rotating action of the

conductor produces an EMF. This EMF, according to Lenz’ law, tends to oppose the

cause, i.e., the supplied voltage. Thus, a DC motor has a very special characteristic of

adjusting its torque in case of varying load due to the back EMF.

Q-06 a)What is the function of a control valve? Explain with neat sketch construction

and working of 4/2- way Spoal valve.

Ans- Process plants consist of hundreds, or even thousands, of control loops all

networked together to produce a product to be offered for sale. Each of these control

loops is designed to keep some important process variable such as pressure, flow,

level, temperature, etc. within a required operating range to ensure the quality of the

end product. Each of these loops receives and internally creates disturbances that

detrimentally affect the process variable, and interaction from other loops in the network

provides disturbances that influence the process variable.

To reduce the effect of these load disturbances, sensors and transmitters collect

information about the process variable and its relationship to some desired set point. A

controller then processes this information and decides what must be done to get the

process variable back to where it should be after a load disturbance occurs. When all

the measuring, comparing, and calculating are done, some type of final control element

must implement the strategy selected by the controller.

The most common final control element in the process control industries is the control

valve. The control valve manipulates a flowing fluid, such as gas, steam, water, or

chemical compounds, to compensate for the load disturbance and keep the regulated

process variable as close as possible to the desired set point.

Control valves may be the most important, but sometimes the most neglected, part of a

control loop. The reason is usually the instrument engineer's unfamiliarity with the many

facets, terminologies, and areas of engineering disciplines such as fluid mechanics,

metallurgy, noise control, and piping and vessel design that can be involved depending

on the severity of service conditions.

Any control loop usually consists of a sensor of the process condition, a transmitter and

a controller that compares the "process variable" received from the transmitter with the

"set point," i.e., the desired process condition. The controller, in turn, sends a corrective

signal to the "final control element," the last part of the loop and the "muscle" of the

process control system. While the sensors of the process variables are the eyes, the

controller the brain, then the final control element is the hands of the control loop. This

makes it the most important, alas sometimes the least understood, part of an automatic

control system. This comes about, in part, due to our strong attachment to electronic

systems and computers causing some neglect in the proper understanding and proper

use of the all important hardware.

What is a Control Valve?

Control valves automatically regulate pressure and/or flow rate, and are available for

any pressure. If different plant systems operate up to, and at pressure/temperature

combinations that require Class 300 valves, sometimes (where the design permits), all

control valves chosen will be Class 300 for interchange-ability. However, if none of the

systems exceeds the ratings for Class 150 valves, this is not necessary.

Control Valve Arrangement

The image below shows how a control valve can be used to control rate of flow in a line.

The "controller" receives the pressure signals, compares them with pressure drop for

the desired flow and if the actual flow is different, adjusts the control valve to increase or

decrease the flow.

Comparable arrangements can be devised to control any of numerous process

variables. Temperature, pressure, level and flow rate are the most common controlled

variables.

Q. 06 b) When a push button is pressed cylinder A extends; when it is fully extended,

cylinder B extends. Then cylinder A retracts; when it is fully retracted, the piston of the

cylinder B too retracts. Design the pneumatic circuit to give the sequence of cylinders

operation as follows: A , B , A ,B + + − −

Ans- This resource is designed to help the student gain the knowledge and skills

required

to achieve the competency MEM18018C – Maintain Pneumatic System Components.

This unit may be assessed on the job, off the job or through a combination of both. The

skills covered by this unit can be demonstrated by an individual working alone or as

part of a team. The unit consists of the two elements detailed in the table below. This

unit can be clustered with MEM15004B – Perform Inspection.How to use this learner’s

guide

This resource is your guide to developing the underpinning knowledge and practical

skills required to pass this unit of competency. It is divided into six sections. These

can be worked through separately (in no particular order) or in sequence. However,

Section 1 must be completed first, as it covers pneumatic safety and basic pneumatic

principles – on which you will be assessed in the practical activities. Each section has

an introduction to the topic area and directs you to undertake tasks, such as reading a

section of a reference text or watching a video, before you do the practical activity for

that section. Most sections also include review questions. These are designed to allow

you to check your understanding of the topic area before you start the practical activity.

Your lecturer will question you to assess your underpinning knowledge during the

practical assessments.

How you will be assessed

Due to the range of available pneumatic equipment and systems in industry, the

practical tasks you will need to undertake to meet the outcomes for this competency

will be determined by your assessor. See your assessor for the practical task

worksheets applicable to the equipment you are using. You must have a good

understanding of the topic area prior to attempting these tasks and you must adhere to

the appropriate manuals and precautions. Adherence to safety procedures, correctness

of maintenance procedures and underpinning knowledge will also be assessed during

these tasks. These assessments can be performed either on or off the job. Your

assessor must be a qualified workplace assessor.

Q. 07 a) Given the logical equation

Y (A BC) (B CA) = + +

i) Design a circuit using gates to realize this functions.

ii) Find out whether it is possible to design the circuit with only one type of gates

(NAND or NOR) If yes, design the circuits

Ans-

Q. 07 b) Using Boolean law simplify the following expressions:

i) X A B C A B C = + ,

ii) Y (A B)(A C)

Q. 08a) Convert the following:

i) 10 8 (320 72) (?) =

ii) 16 8 (4B 2E) (?) =

iii) 8 16 2 (275) (?) (?)

Q.08 b) Using k-map, minimize the following logic function;

f (A,B,C,D) m (0, 1, 2, 3, 5, 7, 8, 9, 11, 14)

Q. 09 a) Explain the following with reference of PLC (a) Jump control, (b) Shift register

Ans- PLC A Programmable Logic Controller, or PLC, is a ruggedized computer used for

industrial automation. These controllers can automate a specific process, machine

function, or even an entire production line.

How does a PLC work?

The PLC receives information from connected sensors or input devices, processes the

data, and triggers outputs based on pre-programmed parameters.

Depending on the inputs and outputs, a PLC can monitor and record run-time data such

as machine productivity or operating temperature, automatically start and stop

processes, generate alarms if a machine malfunctions, and more. Programmable Logic

Controllers are a flexible and robust control solution, adaptable to almost any

application.

a) Jump control- A function often provided with PLCs is the conditional jump. We can

describe this as:

IF (some condition occurs) THEN perform some instructions ELSE perform some other

instructions

Such a facility enables programs to be designed such that if certain conditions are

met,certain events occur, and if they are not met, other events occur. Thus, for

example, we might need to design a system so that if the temperature is above 60 C a

fan is switched on, and if below that temperature no action occurs.Thus, if the

appropriate conditions are met, this function enables part of a ladder program to be

jumped over. Figure illustrates this concept in a general manner. When there is an input

to Input 1, its contacts close and there is an output to the jump relay. This then results in

the program jumping to the rung in which the jump end occurs and skipping the

intermediate program rungs. Thus, in this case, when there is an input to Input 1, the

program jumps to rung 4 and then proceeds with rungs 5, 6, and so on. When there is

no input to Input 1, the jump relay is not energized and the program then proceeds to

rungs 2, 3, and so on.

Figure shows the preceding ladder program in the form used by Mitsubishi. The jump

instruction is denoted by conditional jump (CJP) and the place to which the jump occurs

is denoted by end of jump (EJP). The condition that the jump will occur is that there is

an input to X400. When that happens, the rungs involving inputs X401 and X403 are

ignored and the program jumps to continue with the rungs following the end-jump

instruction with the same number as the start-jump instruction—in this case, EJP 700

Q. 09 b) Explain the criterion for selecting a PLC for the application

PLC selection criteria consists of:

* System (task) requirements.

* Application requirements.

* What input/output capacity is required?

* What type of inputs/outputs are required?

* What size of memory is required?

* What speed is required of the CPU?

* Electrical requirements.

* Speed of operation.

* Communication requirements.

* Software.

* Operator interface.

* Physical environments.

System requirements

* The starting point in determining any solution must be to understand what is to be

achieved.

* The program design starts with breaking down the task into a number of simple

understandable elements, each of which can be easily

described. Application requirements

* Input and output device requirements. After determining the operation of the system,

the next step is to determine what input and

output devices the system requires.

* List the function required and identify a specific type of device.

* The need for special operations in addition to discrete (On/Off) logic.

* List the advanced functions required beside simple discrete logic.

Electrical Requirements

The electrical requirements for inputs, outputs, and system power; When determining

the electrical requirements of a system, consider three items:

Incoming power (power for the control system); Input device voltage; and

Output voltage and current.

Q. 10 a) Describe application of PLC for extending and retracting pneumatic piston

using latches.

Ans- A programmable logic controller (PLC) is essentially a user friendly micro-

processor based microcomputer, consisting of hardware and software, designed to

control the operation of Industrial equipment and processes. An important advantage of

the PLC is that it can be easily programmed and reprogrammed. PLC has tremendous

impact on Industrial control and instrumentation due to its high reliability and flexibility at

the design and implementation stages. The decreasing cost of microprocessor with

increasing facilities in them is acting as catalyst in their widening scope of applications.

In recent years, PLC are being used in place of electromechanical relays or cam

operated logic controllers to control fluid power systems. Modern day PLCs are

developed into a sophisticated and highly versatile control systemcomponent capable of

performing complex mathematics functions and operate at fast microprocessor

speeds. Some leading PLC manufacturers are ABB, Allen Bradley, Honeywell,

Siemens, GE Fanuc, Mitsubishi, Modicon, Omron etc. PLC can be defined as digital

electronic device that uses a programmable memory to store instructions and to

implement functions such as logic, sequencing, counting, timing and arithmetic in order

to control machine, processes and instrumentation PLC is user –friendly digital

computer used for making logic decisions and providing output. It consists of solid state

digital elements and is a replacement for hard-wired electro-mechanical relays to control

pneumatic systems. The term „programmable logic controller‟ is defined as follows by

IEC 1131 ( PLC standard) part 1 ―A digitally operating electronic system, designed for

use in an industrial environment, which uses a programmable memory for the internal

storage of user- oriented instructions for implementing specific functions such as logic ,

sequencing , timing , counting and arithmetic, to control through digital or analog inputs

and outputs, various types of machines or processes. Both the PC and its associated

peripherals are designed so that they can easily integrated into an industrial control

system and easily used in all their intended function‖ PLC is quite similar to digital

computers. They also have certain features which are specific to logic controllers. They

are

1. PLC are rugged and designed to withstand vibrations, temperature , humidity and

noise

2. The interfacing for input and output is part of the controller

3. They are easily programmable and primarily use logic and switching functions

Q. 10 b) Explain the application of PLC in control of conveyor motor

Ans- A programmable Logic Controller (PLC) is a specialized computer used for the

control and operation of manufacturing process and machinery. It uses a programmable

memory to store instructions and execute functions including on/off control, timing,

counting, sequencing, arithmetic, and data handling. Programmable Logic Controllers

(PLC) is used in almost every aspect of industry to expand and enhance production.

Where older automated systems would use hundreds or thousands of

electromechanical relays, a single PLC can be programmed as an efficient replacement.

The functionality of the PLCs has evolved over the years to include capabilities beyond

typical relay control. Sophisticated motion control, process control, distributive control

systems, and complex networking have now been added to the PLC’s Functions.

Therefore, PLCs provide many advantages over conventional relay type of control,

including increased reliability, more flexibility, lower cost, communication capability,

faster response time and convenience to troubleshoot. The paper is based on

systematic conveyor controller programming by programmable logic controller using

omron software which is a world smallest plc, offers variety of expansion options and

has user-friendly software.

A programmable Logic Controller (PLC) is a specialized computer used for the control

and operation of manufacturing process and machinery. It uses a programmable

memory to store instructions and execute functions including on/off control, timing,

counting, sequencing, arithmetic, and data handling. Programmable Logic Controllers

(PLC) is used in almost every aspect of industry to expand and enhance production.

Where older automated systems would use hundreds or thousands of

electromechanical relays, a single PLC can be programmed as an efficient replacement.

The functionality of the PLCs has evolved over the years to include capabilities beyond

typical relay control. Sophisticated motion control, process control, distributive control

systems, and complex networking have now been added to the PLC’s Functions.

Therefore, PLCs provide many advantages over conventional relay type of control,

including increased reliability, more flexibility, lower cost, communication capability,

faster response time and convenience to troubleshoot. The paper is based on

systematic conveyor controller programming by programmable logic controller using

omron software which is a world smallest plc, offers variety of expansion options and

has user-friendly software.

Block diagram of PLC system.

Q.11 a) What is CMOS? Explain the characteristics of CMOS.

Ans- Stands for "Complementary Metal Oxide Semiconductor." It is a technology used to produce

integrated circuits. CMOS circuits are found in several types of electronic components, including

microprocessors, batteries, and digital camera image sensors.

The "MOS" in CMOS refers to the transistors in a CMOS component, called MOSFETs (metal oxide

semiconductor field-effect transistors). The "metal" part of the name is a bit misleading, as modern

MOSFETs often use polysilicon instead of aluminum as the conductive material. Each MOSFET includes

two terminals ("source" and "drain") and a gate, which is insulated from the body of the transistor.

When enough voltage is applied between the gate and body, electrons can flow between the source and

drain terminals.

The "complimentary" part of CMOS refers to the two different types of semiconductors each transistor

contains — N-type and P-type. N-type semiconductors have a greater concentration of electrons than

holes, or places where an electron could exist. P-type semiconductors have a greater concentration of

holes than electrons. These two semiconductors work together and may form logic gates based on how

the circuit is designed.

CMOS Advantages

CMOS transistors are known for their efficient use of electrical power. They require no electrical current

except when they are changing from one state to another. Additionally, the complimentary

semiconductors work together to limit the output voltage. The result is a low-power design that gives

off minimal heat. For this reason, CMOS transistors have replaced other previous designs (such as CCDs

in camera sensors) and used in most modern processors.It is shown by DC analysis that NAND and NOR

CMOS logic circuits can be replaced by equivalent CMOS inverters. The threshold voltage depends on

the number and position of active inputs. It is further shown that the optimum geometry ratio of PMOS

and NMOS transistors depends also on the number of inputs.

characteristics of CMOS- CMOS transistors have replaced other previous designs (such as CCDs in

camera sensors) and used in most modern processors.It is shown by DC analysis that NAND and NOR

CMOS logic circuits can be replaced by equivalent CMOS inverters. The threshold voltage depends on

the number and position of active inputs. It is further shown that the optimum geometry ratio of PMOS

and NMOS transistors depends also on the number of inputs.

Q.11 b) Explain functionality of SCADA

Ans- It is impossible to keep control and supervision on all industrial activities manually. Some

automated tool is required which can control, supervise, collect data, analyses data and generate

reports. A unique solution is introduced to meet all this demand is SCADA system.It is one of the

solutions available for data acquisition, monitor and control systems covering large geographical areas.

It refers to the combination of data acquisition and telemetry.In this system, measurements are made

under field or process level in a plant by number of remote terminal units and then data are transferred

to the SCADA central host computer so that more complete process or manufacturing information can

be provided remotely.

This system displays the received data on number of operator screens and conveys back the necessary

control actions to the remote terminal units in process plant. In Modern SCADA-

SCADA performs automatic monitoring, protecting and controlling of various equipments in distribution

systems with the use of Intelligent Electronic Devices (or RTUs). It restores the power service during

fault condition and also maintains the desired operating conditions.

SCADA improves the reliability of supply by reducing duration of outages and also gives the cost-

effective operation of distribution system. Therefore, distribution SCADA supervises the entire electrical

distribution system. The major functions of SCADA can be categorized into following types.

Substation Control

Feeder Control

End User Load Control

Q.12 a) What are MEMS? Draw the basic block diagram of MEMS and explain it

Ans- Micro-Electro-Mechanical Systems, or MEMS, is a technology that in its most general form can be

defined as miniaturized mechanical and electro-mechanical elements (i.e., devices and structures) that

are made using the techniques of microfabrication. The critical physical dimensions of MEMS devices

can vary from well below one micron on the lower end of the dimensional spectrum, all the way to

several millimeters. Likewise, the types of MEMS devices can vary from relatively simple structures

having no moving elements, to extremely complex electromechanical systems with multiple moving

elements under the control of integrated microelectronics. The one main criterion of MEMS is that there

are at least some elements having some sort of mechanical functionality whether or not these elements

can move. The term used to define MEMS varies in different parts of the world. In the United States

they are predominantly called MEMS, while in some other parts of the world they are called

“Microsystems Technology” or “micromachined devices”.

While the functional elements of MEMS are miniaturized structures, sensors, actuators, and

microelectronics, the most notable (and perhaps most interesting) elements are the microsensors and

microactuators. Microsensors and microactuators are appropriately categorized as “transducers”, which

are defined as devices that convert energy from one form to another. In the case of microsensors, the

device typically converts a measured mechanical signal into an electrical signal.

ver the past several decades MEMS researchers and developers have demonstrated an extremely large number of microsensors for almost every possible sensing modality including temperature, pressure, inertial forces, chemical species, magnetic fields, radiation, etc. Remarkably, many of these micromachined sensors have demonstrated performances exceeding those of their macroscale counterparts. That is, the micromachined version of, for example, a pressure transducer, usually outperforms a pressure sensor made using the most precise macroscale level machining techniques. Not only is the performance of MEMS devices exceptional, but their method of production leverages the same batch fabrication techniques used in the integrated circuit industry – which can translate into low per-device production costs, as well as many other benefits. Consequently, it is possible to not only achieve stellar device performance, but to do so at a relatively low cost level. Not surprisingly, silicon

based discrete microsensors were quickly commercially exploited and the markets for these devices continue to grow at a rapid rate.

More recently, the MEMS research and development community has demonstrated a number of microactuators including: microvalves for control of gas and liquid flows; optical switches and mirrors to redirect or modulate light beams; independently controlled micromirror arrays for displays, microresonators for a number of different applications, micropumps to develop positive fluid pressures, microflaps to modulate airstreams on airfoils, as well as many others. Surprisingly, even though these microactuators are extremely small, they frequently can cause effects at the macroscale level; that is, these tiny actuators can perform mechanical feats far larger than their size would imply. For example, researchers have placed small microactuators on the leading edge of airfoils of an aircraft and have been able to steer the aircraft using only these microminiaturized devices.

The real potential of MEMS starts to become fulfilled when these miniaturized sensors, actuators, and structures can all be merged onto a common silicon substrate along with integrated circuits (i.e., microelectronics). While the electronics are fabricated using integrated circuit (IC) process sequences (e.g., CMOS, Bipolar, or BICMOS processes), the micromechanical components are fabricated using compatible "micromachining" processes that selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices. It is even more interesting if MEMS can be merged not only with microelectronics, but with other technologies such as photonics, nanotechnology, etc. This is sometimes called “heterogeneous integration.” Clearly, these technologies are filled with numerous commercial market opportunities.

Q.12 b) Explain motor isolation schemes.

Ans- Electric motors are ubiquitous in industrial applications. They are used in fans, conveyor belts, printing presses, paper mills, cranes, mixers, hoists, lifts, cooling and recirculating pumps, blowers, compressors, factory robotics, and many other applications. More than 300 million industrial electric motors are in use worldwide, with the number growing steadily every year.

What is Isolation?

A means of transporting data & power between circuits with different ground references (functional isolation) or hazardous voltage levels (user safety) while preventing uncontrolled transient current from flowing in between the two.

Fault detection, isolation, and recovery (FDIR) is a subfield of control engineering which concerns itself with monitoring a system, identifying when a fault has occurred, and pinpointing the type of fault and its location. Two approaches can be distinguished: A direct pattern recognition of sensor readings that indicate a fault and an analysis of the discrepancy between the sensor readings and expected values, derived from some model. In the latter case, it is typical that a fault is said to be detected if the discrepancy or residual goes above a certain threshold. It is then the task of fault isolation to categorize the type of fault and its location in the machinery. Fault detection and isolation (FDI) techniques can be broadly classified into two categories. These include model-based FDI and signal processing based FDI.

A motor is rigidly mounted in the center of an acrylic plate of mass m and flexural rigidity cm. This motor generally produces displacement excitation on its surface. Therefore, the motor produces oscillatory excursions in the outward direction, and thus the mass of the motor is not significant for the excitement of the plate. The middle of the mounting plate experiences displacement excitation of x(t). The mounting plate possesses a natural frequency that is dependent on its mass and flexural rigidity. In

order to decouple or isolate the motor, it must be flexibly attached to the mounting plate. To accomplish this, an additional elasticity c added is interposed between the displacement excitation and the excited mass m, thus creating a single-degree-of-freedom system. This decoupling causes the motor to act like a loudspeaker without a diaphragm; sound radiation is correspondingly low, and the low frequencies are short-circuited. If the decoupling were not present, the case would be that of a loudspeaker coil equipped with a diaphragm: The airborne noise level increases and the perceived spectrum changes in the direction of lower frequencies.