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Submitted by sameer on Wed, 04/03/2019 - 12:17
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MODEL ANSWER

SUMMER– 17 EXAMINATION

Subject Title: Mechatronics Subject Code:

Important Instructions to examiners:

17660

 

1) The answers should be examined by key words and not as word-to-word as given in the model answer scheme.

2) The model answer and the answer written by candidate may vary but the examiner may try to assess the understanding level of the candidate.

3) The language errors such as grammatical, spelling errors should not be given more Importance (Not applicable for subject English and Communication Skills.

4) While assessing figures, examiner may give credit for principal components indicated in the figure. The figures drawn by candidate and model answer may vary. The examiner may give credit for anyequivalent figure drawn.

5) Credits may be given step wise for numerical problems. In some cases, the assumed constant values may vary and there may be some difference in the candidate’s answers and model answer.

6) In case of some questions credit may be given by judgement on part of examiner of relevant answer based on candidate’s understanding.

7) For programming language papers, credit may be given to any other program based on equivalent concept.

 

Q.

No.

Sub Q.N.

Answer

Marking Scheme

   

Q.1

(A)

Attempt any three:

12-Total Marks

   
 

a)

State the importance of mechatronics in various field of engineering.

4M

   

Ans:

Mechanical System:

These system deal with behavior of matter under the action of forces. Mechanical system like hydraulic, pneumatic, rotational or translational, thermal, Fluid etc. are used in mechatronic applications. These systems are interfaced with computer through sensors, actuators and electronic systems.

Electrical systems:

Electrical components mostly used are electrical motors (ac and dc) generators, relays, circuit breakers, switches and so forth.

Electronic systems:

Analog electronics involves action and passive components such as resister, capacitor, inductor, diodes and transistors digital circuits contain logic, gates, counters, Flip-flops, memories, microcontroller and process. Instrumentation &control system: It includes transducer, signal conditioning, output device such as analog meters, display devices recorders and printers.

Information system:

It related with all the aspects regarding information transmission from signal processing to control system and analysis techniques. It is a combinational of communication systems, signal processing, control systems and numerical methods.

Computer system:

It is combinational of hardware and software. In mechatronic applications hardware is computer-specific circuit like flip-flops, counters registers, memories software is nothing

4M

(Any Four Points)

   
              
  

but system & application

    

b)

Explain in brief mechatronics. List its applications.

4M

   

Ans:

Mechatronics:

Mechatronics is the synergistic integration of mechanical engineering with electronics and intelligent computer control in designing, manufacturing processes and production. It helps to develop atomized, reliable and efficient manufacturing/production systems to produce high quality products.

A typical mechatronics system consist of mechanical system, electrical system and computer /information technology

Basic element of Mechatronics system are:

Actuator, solenoids ,motors, switch, sensor, transducer, gear, drive and so on Electrical system/Electronics : Capacitor, semiconductor device, Amplifier, Filter, Digital and analog devices, accerometer Information Technology: Certain Software, System Engineering, Part programming, Artificial Intelligent , CAD,CAM

APPLICATION:

In automatic washing machine and dishwashers.

In CD players, VCRs, camcorders.

In document scanners.

In IC manufacturing system.

In robotics used in welding, nuclear inspection and robot manipulators.

In fax and photocopier machines.

In laser printers.

In flexible manufacturing system.

In air conditioners, elevator controls.

In automotive mechatronics (in automobiles for outdoor locking, collision avoidance and ignition

and antiroll system

2M

2M

   

c)

What is optical encoder? List its types.

4M

   

Ans:

Optical Encoder :

An optical encoder is an electromechanical device which has an electrical output in digital form proportional to the angular position of the input shaft.

Optical encoders enable an angular displacement to be converted directly into a digital form. It has a shaft mechanically coupled to an input driver which rotates a disc rigidly fixed to it.

A succession of opaque and clear segments are marked on the surface of the disc. Light from infrared emitting diodes reaches the infrared receivers through the transparent slits of the rotating disc.

An analogue signal is created. Then electronically, the signal is amplified and converted into digital form. This signal is then transmitted to the data processor.

Types :

1) Incremental optical encoder

2) Absolute optical encoder:

a)Single turn absolute optical encoder

3M

1M

   
  

b)Multiturn absolute encoder

    

d)

Distinguish between transducer and sensor.

4M

  

Ans:

 

4M

Any Four Points

  
 

Serial No

Transducer

Sensor

   

1

It is device which convert any physical quantity other physical quantity which is useful for electrical purpose

It is device which sense any physical quantity and convert it into electrical variable with may signal conditioner

  

2

This is basic ,elementary Device

It is Sophisticated Device

  

3

All transducer are not sensor

All sensor are transducer

  

4

May not accurate

More accurate

  

5

Transducer may be primary or secondary, more classified

Sensor are physical to electrical

  

6

Example : proximity sensor, (photonic, magnetic metallic),

photo diode, LDR, thermistor , etc.

All sensor, LVDT, bellow, Bourdon tube, Speaker, etc.

  

B)

Attempt any One :

6M

   

a)

List advantages and disadvantages of CNC based drilling machine.

6M

   

Ans:

Advantages :

Reduce the making/production cost

Increases the productivity

CNC improves the production

Low skill operator is required

High accuracy and repeatability

Complex machining operations are also performed easily

Indirect operating cost is reduced

Disadvantage :

The initial cost is very high.

The repair and maintenance is complex.

Require part programming

Movement of machine is restricted

Its replacement is difficult, that it is difficult to change old system to new system.

3M

(Any 3 point for each)

3M

(Any 3 point for each)

  
 

b)

Draw block diagram of practical ABS system. State its advantages.

6M

   

Ans:

Advantages:

Anti-lock braking system (ABS) guarantees stable braking characteristics on all road surfaces, hence avoids overturning of the vehicle.

ABS reduces friction on wheels and road, thus increases the efficiency of tires (up to 30%).

The Vehicle with ABS can be stopped at a lesser distance than a non ABS vehicle.

Steering control is effective, i.e., the vehicle can be steered smoothly while braking. Thus minimizes the accidents.

A driver without experience can drive ABS vehicle effectively, then an experienced driver on the non ABS vehicle.

Diagram :

OR

(Any 4, 2M)

4M

   
   
  

OR

[Note- Any other  conceptual diagram mark can be given]

    
   

Q 2

 

Attempt any four :

16M

   
 

a)

Draw and explain general block diagram of Robotic system.

4M

   

Ans:

Diagram :

2M

   
  

[Note:Any other logical robotics diagram can given mark with any type of microcontroller]

Explanation :

An Industrial robot has basic parts like arm, sensor, actuators, controllers etc.

There subsystem communicates among them via, interface, whose function consists basically of decoding the transmitted information from one medium to another.

Fig. above shows block diagram of typical robotics mechanical system. The input is a prescribed task, which defined earlier

The output of robotic mechanical system is the actual task, which is monitored by sensors. These sensors sense and transmit the information in the form of feedback signals.

This is compared with the predefined task given to the controller

2M

   
   

b)

Explain in brief cam. State the types of cam. List two applications.

4M

   

Ans:

Working principle of cam:

A cam is mechanical rotating machine element which is used for converting one motion in to another. A cam is a curved or grooved surface which mates with a follower and imparts motion to it. In general the cam may be rotating or oscillating whereas the follower may be rotating, reciprocating or oscillating.

Types of CAM:

Wedge/flat cam

Plane or disc cam

Cylindrical cam

Conical cam

Helical cam

Radial

3-dimentional

1M

1M

   
  

Applications of cam:

Automatic machines.

IC engines.

2M

Any Four

   

Machine tools.

    

Printing control mechanisms.

    

Spinning and weaving machineries.

    

Textile machineries.

    

Paper cutting machines.

    

c)

Explain working of Belt. List types of Belt.

4M

   

Ans:

Working :  A belt is a loop of flexible material used to mechanically link two or more rotating shafts, most often parallel.  Belts may be used as a source of motion, to transmit power efficiently, or to track relative movement. Belts are looped over pulleys and may have a twist between the pulleys, and the shafts need not be parallel. In a two pulley system, the belt can either drive the pulleys normally in one direction (the same if on parallel shafts), or the belt may be crossed, so that the direction of the driven shaft is reversed (the opposite direction to the driver if on parallel shafts). As a source of motion, a conveyor belt is one application where the belt is adapted to continuously carry a load between two point.

2M

   
 

Types of belt :

1)Vee belt

2)Flat belt timing belt 3)Ribbed belt

4)Film belt 5)Multigrooved belt

2M

(Any 4,

½ M Each)

   
 

d)

Draw and explain electronic PID controller.

4M

   

Ans:

Diagram :

2M

   
  

Explanation

The PID control scheme is named after its three correcting terms, whose sum constitutes the manipulated variable (MV). The proportional, integral, and derivative terms are summed to calculate the output of the PID controller. Defining as the controller

output, the final form of the PID algorithm is:

Where ,

: Proportional gain, a tuning parameter

: Integral gain, a tuning parameter : Derivative gain, a tuning parameter

: Error

: Time or instantaneous time (the present)

: Variable of integration; takes on values from time 0 to the present .

The proportional term produces an output value that is proportional to the current error value. The proportional response can be adjusted by multiplying the error by a constant Kp, called the proportional gain constant

2M

   

e)

Define sensor, signal conditioner, controller and actuator in mechatronic system.

4M

   

Ans:

Sensor: - A sensor is an element in a measurements system that acquires a physical parameter and changes it into electrical signal. E.g. Bellows, Thermocouple

Signal Conditioners:- The signal conditioner performs isolation, impedance matching, noise reduction, amplification, conversion of sensor output signal.

Actuators:- Actuators are the process of conversion of energy to mechanical form. Controllers:- Controllers are the brains of control system operation and decide the kind of action taken in response to an error

1M

Each

   

f)

List out various position sensors. Explain any one in detail.

4M

   

Ans:

List : 1)Potentiometer 2) Eddy current sensorproximity sensor 3)Capacitive sensor 4)Hall effect sensor 5)Optical sensor/photo electric sensor 6)Inductive sensor Explanation : (Note : Any one can be explain with principle of position control ,basic schematic diagram and application as postion measurement and position control) Example : Capacitive sensor: Capacitance is an electrical property which is created by applying an electrical charge to two conductive objects with a gap between them. A simple demonstration is two parallel conductive plates of the same profile with a gap between them and a charge applied to

2M

2M

   
  

them. In this situation, the Capacitance can be expressed by the equation: C=, ε0 KA/d Where C is the capacitance, ε0 is the permittivity of free space constant, K is the dielectric constant of the material in the gap, A is the area of the plates, and d is the distance between the plates. There are two general types of capacitive displacement sensing systems. One type is used to measure thicknesses of conductive materials. The other type measures thicknesses of non-conductive materials or the level of a fluid. Application: Precision positioning One of the more common applications of capacitive sensors is for precision positioning. Capacitive displacement sensors can be used to measure the position of objects down to the nanometer level. This type of precise positioning is used in the semiconductor industry where silicon wafers need to be positioned for exposure. Capacitive sensors are also used to pre-focus the electron microscopes used in testing and examining the wafers. [Note: For Any logical Diagram Mark can be given] e.g potentiometer is direct contact type position control sensor as rotation will change motor will rotate that change will measureshaft rotation which will give us change in resistance that will give us voltage which can be consider as error and actuator will move according to correct position.

    
   

Q. 3

 

Attempt any four:

16M

   
 

a)

Draw and explain Fuzzy logic controller.

4M

   

Ans:

Diagram :

2M

   
  

Explanation:

Fuzzification :

It is the action of transforming a given state as crisp input into fuzzy values by evaluating membership function for purpose to be used by a fuzzy interference mechanism.

Membership function forms a crucial part in fuzzy rule base model because actually they only define Fuzzification of control variable in other word.

Fuzzification is the process of making a crisp quantity fuzzy.

In the real world, hardware such as a digital voltmeter generates crisp data, but these data are subject to experimental error.

Fuzzification based on rule base or by decision making with knowledge base

Membership function is bell shaped or triangular or trapezoidal shape

2. Fuzzy Interference:

Once membership function is found for each of variable an intelligent decision can be made to what output should be. This decision process is called interference this can be done knowledge base decision as well as rule base. This output then connected to Defuzzification block

3. Defuzzification:

Converts the fuzzy output of the inference engine to crisp using membership functions analogous to the ones used by the fuzzifier. A Defuzzification strategy is aimed at producing a non- fuzzy control action that best represent the possibility of an inferred fuzzy control action

2M

   
   

b)

Compare Electronic controllers with pneumatic controllers.

4M

   

Ans:

 

(Any 4,1M

each)

   
 

Electronic contrllers

Pneumatic controller

    

Low power requirements

High power requirements

   

Speed of response is substantially instantaneous

Speed of response is not substantially instantaneous

   

Complex networks

Simple networks

   

Difficult maintenance and test kit requirements

Essay maintenance and test kit requirements

   
       

c)

List different components of Industrial Robot. State functions of any two.

4M

   

Ans:

Components of Robots:

A robot is a complex machine which may contain mechanical, electrical, pneumatic, hydraulic and microelectronic components. Essentially a robot consists of four elements.

Drive system:

The drive system controls and velocity of end effectors. There are three major type of drive used in robots, namely,

Electrical drives;

Hydraulic drives;

Pneumatic drives.

Control system:

The control system controls and velocity of the end effectors of the robot based on the logical sequence and operating programs.

Measuring system:

A measurement of output is important; the control system continuously measures the actual position during a motion cycle and compares it with the theoretical values required, in order to provide a correction action.

Sensors:

The main function of to permit the robot to interact with the environment in

an intelligent manner. Various types of sensors are available nowadays including tactile proximity, ultrasonic ranging and vision sensors.

List-2M, Function of any Two- 1M each.

   

d)

Define DOF. Draw and explain six degrees of freedom.

4M

   

Ans:

DOF:

Degree of freedom is a term used to describe a robot’s freedom of motion in 3 dimensional spaces specifically the ability to move forward and backward, up and down,

left and right. For each DOF a joint is required. Six degrees of freedom (6DoF) refers to the freedom of movement of a rigid body in three-dimensional space. Specifically, the body is free to change position as forward/backward (surge), up/down (heave), left/right (sway) translation in three perpendicular axes, combined with changes

in orientation through rotation about three perpendicular axes, often termed yaw (normal axis), pitch (lateral axis), and roll (longitudinal axis).

Definitation

-1M,

Explanation

-1½M,

Diagram-

   
  

OR

1½M

   

e)

Draw and explain Rack and Pinion assembly.

4M

   

Ans:

Rack and Pinion :

A rack and pinion is a type of linear actuator that comprises a pair of gears which convert rotational motion into linear motion. A circular gear called "the pinion" engages teeth on a linear "gear" bar called "the rack"; rotational motion applied to the pinion causes the rack to move relative to the pinion, thereby translating the rotational motion of the pinion into linear motion.

Example :

in a rack railway, the rotation of a pinion mounted on a locomotive or a railcar engages a rack between the rails and forces a train up a steep slope.

For every pair of conjugate involute profile, there is a basic rack.

This basic rack is the profile of the conjugate gear of infinite pitch radius (i.e. a toothed straight edge).

A generating rack is a rack outline used to indicate tooth details and dimensions for the design of a generating tool, such as a hob or a gear shaper cutter.

Diagram:

Expalinatio n-2M

2M

   
  

OR

    
 

f)

Classify bearing and explain any one in brief.

4M

   
 

Ans:

Bearing :

Hydrodynamic Bearings

Hydrostatic Bearings

Rolling Element Bearings

(Classificati on-2M Explanation any 1-2M)

   
 

Types of bearings-

    
 

Radial bearing

Thrust bearing

Sliding contact bearings

Rolling contact bearings

    
 

Hydrodynamic and Hydrostatic Bearing :

Hydrodynamic and Hydrostatic Bearings are those which we design and manufacture all by ourselves for the majority cases.

These are more specific to the application, costlier in budget but work really effectively.

    
 

Rolling Element Bearing :

Rolling Element Bearings are those which are readily available catalogued products in the market.

They are surely cost effective; just select them from the catalogue based on the requirement.

Very rarely are rolling element bearings designed and manufactured.

Although the bearings are classified into these three types the varieties each type of bearing holds is enormous. The forthcoming articles will deal more with these details.

    
       

Q. 4

A)

Attempt any three :

12M

   
 

a)

Draw block diagram of microcontroller based pick and place Robot. List the four movements required by this Robot.

4M

   

Ans:

Diagram :

OR

Explanation:

The robot has three axes about which motion can occur.

Rotation in a clockwise or anti-clock wise direction of the unit on its base Arm extension or contraction and arm up or down.

Gripper can open or close.

These movements can be actuated by the use of pneumatic cylinders operated bysolenoid controlled valves with limit switches to indicate when a motion is completed ,Thus clock wise rotation of the unit might result from the piston in a cylinder being

extended and the anticlockwise direction by its retraction.

Likewise the upward movement of the arm might result from the piston in a linear cylinder being extended and the downward motion from it retracting.

The extension of the arm by the piston in another cylinder extending and its return movement by the piston retracting.

The gripper can be opened or closed by the piston in a linear cylinder extending or

2M

2M

   
   
  

retracting as.

    

b)

List advantages and applications of PLC.

4M

   

Ans:

Advantages Of Programmable Controller :

1. Very fast

2. Easy to change logic i.e. flexibility

3. Reliable due to absence of moving parts

4. Low power consumption

5. Easy maintenance due to modular assembly

6. Facilities in fault finding and diagnostic

7. Capable of handling of very complicated logic operations

8. Good documentation facilities

9. Easy to couple with the process computers

10. Analog signal handling and close loop control programming

11. Counter, timer and comparator can be programmed

12. Ease operator interface due to colourographic and advisory system introduction.

(Any 4 -½M Each)

   
 

Application :

1. Home automation

2. Railway signaling

3. Chemical plant

4. Packaging industry

5. Automobile industry

(Any 4 -½M Each)

   

c)

Draw block diagram of pneumatic system showing its basic components. State the functions of control value and air actuator.

4M

   

Ans:

Diagram :

Control valve: - control and regulates the direction of flow and pressure etc.

Air actuator: - Air cylinders and motors are used to obtain the required movements of direction flow.

2M

   
 

1M

   
 

1M

   

d)

Explain the principle of operation of solenoid. State two parameters on which

selection of solenoid is based.

4M

   

Ans:

Diagram :

    
       

Note: Diagram is optional

    

Principle:

A solenoid is a simple electromagnetic device that converts electrical energy directly into linear mechanical motion, but it has a very short stroke (length of movement), which limits its applications. A solenoid valve is the combination of a basic solenoid and mechanical valve. So a solenoid valve has two parts namely- Electrical solenoid, mechanical valve. Solenoid converts electrical energy to mechanical energy and this energy is used to operate a mechanical valve that is to open, close or to adjust in a position.

Principle- 2M

   

Parameters on which selection of solenoid is based-

1. Size

2M

   

2. Flow capacity

    

3. Applied Voltage

    
 

B)

Attempt any one :

6M

   

a)

Draw and explain schematic of PLC based automatic car parking barrier system.

6M

   

Ans:

Diagram :

Ladder Diagram- 4M

   
  

Explanation:

Automatic car parking system allow to park maximum numbers of car in parking zone according to size of parking zone. parking zone number of vehicle parked in parking zone is less than available parking space then automated parking system allow entering next car in parking zone. In parking zone number of vehicle parked in parking zone is equal to available parking space then automated parking system does not allow enter

next car in parking zone.

Explanation

:2M

   

b)

Draw a ladder diagram for following conditions of conveyor motor.

I) Start push button to start the conveyor motor.

II) Bottle moves past the photo sensor and the conveyor motor stops automatically after count of 25 bottles.

III) The counter is to be rest to zero after 25 bottles.

IV) The conveyor motor can be stopped manually at any time.

V) The accumulated count of the courter is reset manually by means of count reset button.

6M

   
 

Ans:

Diagram :

Note: Any other relevant logic for program can be considered.

Ladder Diagram- 6M

   
  

Ladder Diagram for entry-

Ladder Diagram for Exit-

    
   

Q.5

 

Attempt any four :

16M

   
 

a)

Draw and explain the working principle Linear Velocity Transducer (LVT).

4M

   

Ans:

Diagram :

Principle :

2M

2M

   

b)

Explain working principle of stroboscope with neat sketch.

4M

   

Ans:

Diagram :

Explanation :

The arrangement of two flanges A and B placed at a distance on the shaft is as shown. Flange A carries a scale while flange a pointer.

2M

2M

   
  

When a torque is applied on the shaft it causes angular displacement of pointer relative to the scale due to the angular twist.

The deflection of the shaft may be read off directly when the shaft is stationery. However this is not possible if the shaft is rotating.

In such cases, stroboscope is used. The flashing light of the stroboscope is applied onto the scale and the flashing frequency is adjusted till a stationery image is obtained.

The scale reading can now be taken for measuring the angular twist. This method is simple and inexpensive. However, the accuracy of measurement is poor.

    

c)

Draw and explain pneumatic proportional controller.

4M

   

Ans:

Explanation :

Basic :

Proportional control is one in which the process input is change in direct proportion to the error(t) controls the output so that the manipulated variable and the error has proportional relation. The controller set the manipulated variable in proportion to The difference between the set point SP and the measured variable MV.

The variable to be controlled, e.g. speed of a motor. Higher the difference, more is the change in the manipulated variable.

The coefficient of deviation is called proportional gain, Kp and is mathematically written as:

Diagram :

OR

2M

2M

   
  

The controller is effectively an amplifier with a constant gain having certain range called as appropriate band.

The proportional control action is used where the position of the final operator is determined by the relationship between the MV and SP reference value called as error Given as :

Error = SP - MV

    
 

d)

Draw and explain block diagram of MEMS.

4M

   
 

Ans:

Diagram :

Explanation :

2M

2M

   
       
 

e)

List advantages and disadvantages of MEMS.

4M

   
 

Ans:

Advantages :

1. Batch fabrication and hence reduced cost.

2. Reduced size and reduced power ( due to pin size and reduced package volume)

3. High precision and resolution.

4. Reduced parasitic due to interconnecting devices.

Disadvantages :

1. Very small to trace out

2. Due to small size, it is physically impossible for MEMS to transfer any significant power.

3. They are made from poly-si , a brittle material , they cannot be loaded with large forces because brittle materials can be fractured easily under high stress.

2M

Any Two

2M

Any Two

   
 

f)

For a signal conditioner explain the terms linearization and signal conversion.

4M

   
 

Ans:

Definition :

1. linearization :

Many primary elements produce nonlinear outputs and the signal must be linearized to produce a nearly ideal calibration. Specialized analog circuits such as offsetting circuits, proportional output circuits, V to I convertor etc. are used to linearize a signal. Even computer algorithms are also used.

2.Signal conversion :

2M

2M

   

Q.6

 

Attempt any four :

16M

   
 

a)

Give two applications of each :

1) Eddy current sensor

2) Optical sensor.

4M

   

Ans:

Eddy current sensor :

1. Detection of non-magnetic but conductive materials.

2. Displacement sensing

3. Position sensing

2M

(Any Two)

   
  

Optical sensor.:

1. Position Detection

2. Velocity Detection

3. Acceleration Detection

4. Direction Detection

2M

(Any Two)

   

b)

Draw and explain implementation of proportional type Hydraulic controller.

4M

   

Ans:

Diagram :

OR

Explanation :

2M

2M

   
   
       

c)

List different types of Gears and state two applications of each.

4M

   

Ans:

 

4M

(Any Four Points)

   

d)

Draw and explain the working principle of MEMS accelerometer.

4M

   

Ans:

Diagram :

Explanation :

2M

2M

   
       

e)

Draw a ladder diagram for

I) To ON-off a motor with push button.

II) To off a motor after 5 sec.

4M

   

Ans:

To ON-off a motor with push button :

To off a motor after 5 sec :

2M

2M

   
   
       
 

f)

Explain the working principle of capacitive sensor with neat diagram.

4M

   
 

Ans:

Diagram :

Working Principal:

2M

2M