Two marks Questions Mechatronics [MH1031] Unit – 1 1. What is Mechatronics? Give examples. Mechatronics is the synergistic integration of mechanical engineering with electronics & Intelligent control algorithms in the design & manufacture of products process. Examples : washing machine, Robot, automobile electronic fuel injection & antilock brake systems, digital camera etc. 2. Describe various elements of measurement system with help of a block diagram.
Sensor : It responds to the quantity being measured by giving as its output a signal which is related to the quantity. Signal conditioner : It takes the signal from the sensor & manipulates it into a condition which is suitable for either display (or) for use to exercise control. Display : The output from the signal conditioner is displayed. 3. Identify the sensor, signal conditioner & display elements in the measurement systems of a) mercury in glass thermometer b) a Bourdon pressure gauge. a) Sensor – mercury b) Sensor Sensor – curved curved tube tube signalconditioner–fineborestem signal conditioner – gears display – marks on the stem. displa display y – point pointer er movin moving g across across a scale. 4. Identify the various elements that might be present in a control system involving a thermostatically controlled electric heater. Process heater Controlled variable temperature Measurement device bimetallic strip Comparison element thermostat Correction element relay. 5. What is meant by sequential control & illustrate with an example. The control system in which the actions are strictly ordered in a time or event driven sequence is known as sequential control. Example : domestic washing machine. The operations to be carried out in the correct sequence are, pre wash cycle, main wash cycle & rinse cycle.
6. State steps that might be present in the sequential control of a dish washer. Water in, rinse, water out Water in, heat water, rinse, water out Water in, rinse, water out 7. Compare & contrast the traditional design of a watch with that of a Mechatronics designed product. product. Traditional design
Mechatronics design
i. Bulky
i. Compact
ii. Limited functions
ii. More functions
iii. iii. Require ires re rewindi nding
iii. iii. Does oes no not re require ire re rewind inding
iv. Costlier
iv. Cheaper.
8. Compare and contrast the control system for the domestic central heating system involving a bimetallic bimetallic thermostat thermostat and that that involving involving micropro microprocessor. cessor. Bimetallic element
Mechatronics design
i. Slow
i. Fast
ii. Limited accuracy
ii. More accurate
iii. Simple functions
iii. Many functions
iv. Cheap
iv. More Cheap.
9. List the advantages of Mechatronics system. 1. Increased functionality and letter design 2. More use of electronics & software instead of mechanical function 3. Assumes responsibility for process & operation with little interference of operators. 4. High levels of integration 5. Uses AI and intelligent process control 6. High reliability & safety. 10. Describe briefly the evolution of Mechatronics system. Modern Mechatronics systems evolved through several stages and categorized as : 1. Stand alone systems : Ex : washing washing machine, machine, compact disk player, auto focus, camera, boat auto pilot etc. 2. System with high high level level of of distributed distributed sensor, sensor, micro micro controller controller,, actuator actuator Ex : wire aircraft. 3. Larg Largee fact factor ory y syst system em.. 4. System that incorpor incorporates ates intelligent intelligent control Ex : humanoid humanoid robot. 11. What are the disadvantages of Mechatronics design. 1. Initial cost is very high 2. Complicated design 3. Repair & maintenance is complex
4. Its replacement is difficult.
12. What are the key elements of Mechatronics system. 1. Information system 2. Mechanical system 3. Electrical system 4. Computer system 5. Sensor & actuators 6. Real time interfacing.
Unit – 2 1. Define sensor & transducer Sensor is an element in a measurement system that acquires a physical parameter and changes changes it into a signal. signal. Transdu Transducer cer is a device that convert convertss the energy energy from one form to another. 2. Define range & span. The range range of a transducer defines defines the limits between between which the input input can vary. The span is the maximum value of the input menus the minimum value. 3. Define accuracy & precision Accuracy : It is defined as the ability of an instrument to respond to a true value of a measured variable under the reference conditions. Precision : It is defined as the degree of exactness for which an instrument is designed to perform. 4. Define sensitivity. It is the relationship indicating how much output may be obtained per unit input. 5. Define Hysteresis. It is defined as the difference in the output for a given input when this value is approached from the opposite directions. 6. Define repeatability & reproducibility. Repeatability : It is defined as the ability of an instrument to produce the same output for repeated applications of the same input value. Reprod Reproducib ucibility ility : It is defined defined as the closeness closeness of agreem agreement ent among the repeated repeated measurements of the output for the same value of the input under the same operating conditions over a period of time. 7. Define stability : It is the ability of the transducer to give the same output when used to measure a constant input over a period of time. 8. Define dead band and dead time Dead band : It is the range of input values for which there is no output. Dead time : It is the length of time from the application of an input until the output begins to respond & change. 9. Defin Definee Resol Resolut ution ion : It is the small smallest est chang changee in the the inpu inputt valu valuee that that will will prod produc ucee an observable change in the output. 10. Explain the significance of the following information given in the specification of a strain gauge transducers :
Range : 70 to 1000 K Pa Full range output : 40 mV Non linearity linearity & hysteresis hysteresis : ± 0.5% full range output.
•
• •
The The rang rangee indica indicate tess that that the the tran ransdu sducer cer can can be used sed to measure pressures between 70 & 1000 KPa It gives an output of 40 mV when the pressure is 1000 KPa Non linearity linearity & hysteresis hysteresis will lead to erros of ± 0.5% of 1000, (ie) ± 5 KPa.
11. What is the non-linearity error, as a percentage of full range, produced when a 1K Ω potentiometer potentiometer has a load of 10K 10K Ω & is at onethird of its maximum displacement. R P =1KΩ,
R L =10KΩ, R P
non-linearity error=
(x
x=0.33 2
-x 3 )
R L ×100% R P x ( 1-x ) +1 R L =
0.1( 0.332 -0.333 ) 0.1× 0.1×0. 0.3 33 ( 1-0.3 0.33 ) +1
= 0.7%
12. What is displacement & position sensor. Displacement sensors are concerned with the measurement of the amount by which some object object has been been moved. moved. Position sensors sensors are concerned concerned with with the determinatio determination n of the position position of some some object object with reference reference to some reference reference point. point. 13. Name some sensors which are used for displacement measurement. 1. potentiometer sensor 2. resistance strain gauge element 3. push push – pul pulll dis displ plac acem emen entt sen senso sorr 4. LVDT LVDT 14. Name some sensors which are used for position measurement. 1. photo electric sensors 2. Hall effect sensors
3. optical encoders.
15. Define proximity sensor. Proximity sensors are a form of position sensor and are used to determine when an object has moved to within some particular critical distance of the sensor. 16. Define Define optical encoder. What are its type. An encoder is a device that provides a digital output as a result of a linear (or) angular displacement. Incremental encoder : It detect changes in rotation from some datum position. Absolute encoder : It gives the actual angular position.
17. What is hall effect? When When a beam beam of charg charged ed parti particle cless passe passess thro throug ugh h a magn magnet etic ic field field,, the beam beam is deflected deflected from it straight line path due due to the forces acting on the the particles. This is known known as Hall effect. 18. What is the working principle of eddy current proximity sensor? If a coil coil is supp supplie lied d with with an alter alternat nating ing curre current, nt, an alter alterna natin ting g magn magneti eticc field field is produced. produced. If there is a metal object in close proximity to this alternating alternating magnetic field, then eddy currents currents are induced induced in it. The eddy eddy currents currents themselves themselves produce a magnetic magnetic field. field. As a result, the impedance of the coil changes & so the amplitude of the alternating current. 19. Name some sensors used for measurement of velocity 1. Tachogenerator 2. incremental encoder3. r3. pyro electric sensor 20. Name some signal conditioning operations. Ampl Amplif ific icat atio ion, n, line linear ariz izat atio ion, n, comp compar aris isio ion, n, prot protec ecti tion on,, filt filter erin ing, g, compensation, Analog to Digital conversion, Digital to Analog conversion.
temp temper erat atur uree
21. What is the resolution of an AD converter with a word length of 12 bits & an analogue signal input range of 100v? 100 Resolution = =24.4mV 212 22. What is the conversion time for a 12 bit ADC with a clock frequency of 1 MHz? 1 Conversion time = =0.5 µ sec 2 × 106 23. State shannon’s sampling theorem. When the signal is sampled at a rate f s ≥ 2f m, the signal can be reconstructed from its samples without distortion. Unit – 3 1. Draw the symbols for a) a pressure relief valve
b) a 2/2 valve
c) a 4/2 valve
2. A pneumatic system is operated at a pressure of 1000 k Pa. What diameter cylinder will be required to move a load requiring a force of 12 KN? Force Pres Pressu sure re = Area 12 A= =12×10-3 1000 πD2 4
=12×10-3
D 2 = 0. 0.015 D = 124mm. 3. If a stepper motor has a step angle of 7.5 °, what digital input rate is required to produce a rotation of 10 rev/sec?
No.of pulses per step =
360o
=48 pulses/sec. 7.5o Digital input =48×10 = 480 pulses/rev.
4. State the number of degrees of freedom each of the following mechanism has: Your knee – degrees of freedom – 1 Your ankle – degrees of freedom – 3 Wind screen wiper mechanism – DOF – 1 5. A hydraulic cylinder is to be used to more a work piece through a distance of 60 mm in 20 secs. A force of 15KN 15KN is required required to move move the work work piece. piece. Determine Determine the required required working working pressure & hydraulic hydraulic flow rate if a cylinde cylinderr with a piston piston diameter diameter of of 75mm is available. available. Area =
π ( 0.075 )
flowrate = pressure =
2
4 0.06× 20 F A
=
m2
=
15×103
= =
m3 /sec. KPa
6. Suggest suitable actuator for robot arm joint & justify.
7. An actuator actuator has a stem movement movement which at full travel is 40mm. 40mm. It is mounted with with a linear plug process control control valve which has a minimum minimum flow rate of 0.4 a maximum flow rate of 0.2 m3/s. What will will be the flow rate when the stem movement is a) 10 mm b) 20 mm? For For a linea linearr valv valvee the the perce percenta ntage ge flow flow rate rate is the the same same as the percen percentag tagee stem stem displacement. a) a percentag percentagee stem displacem displacement ent of 25% gives gives a percentage percentage flow flow rate of 25% (ie) 0.05 0.05 3 m /s. b) a percentage percentage stem displacement displacement of 50% gives a percentage percentage flow rate of 50% (ie) 0.1 3 m /s. 8. An actuator has a stem movement movement which at full travel is 40 mm. It is mounted on a process control valve with an equal percentage plug & which has a minimum flow rate of 0.2 m 3/s & a maximum flow rate of 4 m 3/s. what will be the flow rate when the stem movement movement is a) 10mm b) 20mm. 20mm. Q min = 0. 0.2m3 / sec sec Q max = 4m 4m 3 / sec sec S max = 40mm
S
a)
Q max = Q min
Q Q min
S max
10
4 Q = 0 .2 × 0.2
40
= 0.42m /sec. 3
20
b) Q = 0.2 × 0.2 4
40
= 0.89m
3
/s /sec.
9. What is mechanism & Kinematics. Mechanism are motion converters in that they transform motion from one form to some other required form. Kinematics is the study of motion without regard to forces. 10. What is kinematics chain & four bar chain. A sequence of joints & links is known as kinematics chain.The connection of four links to give four joints about which turning can occur is known as four bar chain. 11. What is cam? What are its types. A cam is a body which rotates or oscillates and in doing so imparts a reciprocating or oscillatory motion to a second body called the follower. Types : eccentric, heart shaped & pear shaped. 12. A compound gear train consists of the final driven wheel with 15 teeth which meshes with a second wheel wheel with 90 teeth. teeth. On the same shaft as the second second wheel is a wheel with 15 15 teeth. This meshes with a fourth wheel, the first driver, with 60 teeth. What is the overall gear ratio? overall gear ratio =
= =
wA
=
wD N B N A
×
wA wB
wB wC
=
wC wD
ND NC
15 15
×
=
60 90
=
1 24
.
13. Identify the motions involved in the following mechanism. 1. The keys keys on a compu computer ter keybo keyboard ard – transla translation tional al motion motion 2. The pen pen in an XY XY plotter plotter – trans translati lational onal motio motion n 3. The hou hourr hand hand of a clock clock – rota rotation tional al motio motion n 4. the pointe pointerr on a moving moving coil coil ammete ammeterr – rotationa rotationall motion motion 5. An automatic automatic screw driver – translational translational plus rotational rotational motion. motion. 14. A d.c moter is required to have a) a high torque at low speeds for the movement of large loads loads b) a torque torque which which is almost almost constant constant regardle regardless ss of speed. speed. Sugges Suggestt suitable suitable forms forms of motor. a) Ser Series ies wou wound nd d.c. d.c. mot motor or b) Shu Shunt nt wou wound nd d.c. d.c. mot motor. or.
15. Suggest possible motors d.c (or) a.c, which can be considered for applications where a) cheap, cheap, constant constant torque operatio operation n is required required b) high controlle controlled d speeds speeds are require required d c) low speeds are required d) maintenance maintenance requirements have to be be minimized. a) D.C. shunt wound b) induction motor
c) d.c. motor
d) a.c. motor.
Unit – 4 1. Define programmable logic controller PLC is defined as a digital electronic device that uses a programmable memory to store instr instruct uction ionss and and to impl implem emen entt functi function onss such such as logi logic, c, seque sequenci ncing ng,, timing timing,, count counting ing & arithmetic in order to control machines & processes. 2. Sketch the timing diagram for ON delay & OFF delay timer. ON delay timer : This type of timer waits for a fixed delay period before turning ON.
OFF delay timer : This type of timer switches off an output after a time delay from being energized.
3. Draw the relay programming & PLC Programming Programming equivalents for two input AND & NOT gate. Relay programming PLC programming
AND gate
A coil is not energized unless two, normally open switches are both closed.
NOT gate
A coil is energized, when there is no input to the switch. 4. What is latching in PLC’s? In some situation’s, it is necessary to hold a coil energized, energized, even when the input which energiz energized ed it ceases. ceases. The latch latch circuit circuit is used used to carry carry out out such an opera operation tion.. It is a self maintaining circuit, in that after being energized, it maintains that state until another input is received. It remembers remembers its last state. 5. Device a PLC timing circuit that will switch an output ON for 10 secs & then switch it off.
6. What are the criteria that need to be considered for selecting a PLC? 1. input / output capacity is required 2. type of input / output is required 3. size of memory is required 4. speed & power required for CPU is needed. 7. Mention specific features of PLC’s 1. PLC’s are rugged & designed to withstand vibrations temperature, humidity & noise. 2. The interfacing for inputs & outputs is inside the controller. 3. They are easily programmed. 8. State the programming methods of PLC. 1. Ladder programming 3. Function block diagram 5. Instruction list
2. Structured text programming 4. Sequential function charts
9. What are the three major types of PLC application? 10. Name the two ways in which input / output is incorporated into the PLC. 11. Draw the ladder logic diagram to represent a) two switches that are normally open & both have to be closed for a motor to operate b) Either of two, normally open, open, switches have to be closed for a coil to be energized & operate an actuator.
12. What is ladder programming? The ladder programming involves each program task being specified as though a rung of a ladder. Thus such a rung could could specify that the state of switches switches A & B are both closed then a solenoid, the output is energized. 13. Write about internal relays? The internal relays behave like relays with their associated contacts, but in reality are not actual relay but associated by the software of the PLC. PLC. Internal relays are used when there are programs with multiple input conditions. 14. What is an up counter & down counter?
An up counter could count up to the preset value (ie) events are added until the number reaches the set values, when the set value is reached the counters contact changes state. A down counter could count down from the preset value to zero (ie) events are subtracted from the set value. When zero is reached the counters contact changes state. 15. What are operations that are carried out with a PLC on data words? 1. moving data 2. comparison of magnitudes of data 3. Arithmetic operations such as additons & subtraction 4. Conversions between BCD, binary & octal.
Unit – 5 1. What are the various stages in designing Mechatronics system? The various stages in Mechatronics design are a) The need b) Analysis Analysis of the problem problem c) Preparation of the specification d) Generation of the possible solutions. e) Selection of the suitable solutions f) production of a detailed design g) Production of working drawings 2. What are the advantages of the micro processor controlled system? The microprocessor controlled system can cope easily with given precision & programmed programmed control. control. The System System is much more flexible. flexible. This improve improvement ment in flexibility flexibility is a common characteristic of Mechatronics systems when compared with traditional systems. 3. List down the various Mechatronics elements in an automatic camera. The basic elements of the control system used in an automatic camera is body, lenses & flash. The other elements are 1. sensors – Light Light sensor, sensor, range range sensor, lens sensor sensor metering sensor. 2. sole soleno noid id valv valvee 3. flas flash h sett settin ing g unit unit 4. motor motor drive drives, s, zoom zoom & expo exposure sure unit. unit. 4. What are the axes of a pick & place robot? The robot has three axes about which motion can occur a) Rotation Rotation in a clockwise clockwise (or) counter counter clockwise clockwise direction direction of of the unit unit on its base. b) Arm extension extension or or contraction contraction & arm up or down down c) Gripp Gripper er open open (or) (or) clo close. se. 5. How do the movement of robot take place? • Clockwise rotation of the unit might result from the piston in a cylinder being extended extended & the counter counter clockwise clockwise direction direction by its retraction. retraction. • The upward movement of the arm might result from the piston in a linear cylinder being extended and the downward motion from it retracting. 6. List the actuators used in automatic camera & its function.
ACTUATOR
FUNCTION
Motor I
Film transport
Motor II
Shutter & mirror action, film rewind
Motor III
Focusing drive
Motor IV
Lens aperture drive
Motor V
Flash zoom drive
Shutter magnet
Exposure time control
7. List the difference between traditional design & Mechatronics design. TRADITIONAL DESIGN
MECHATRONIC DESIGN
Bulky system
Compact
Complex mechanisms
Simplified mechanisms
Non – adjustable adjustable movement movement cycle cycle
Programmabl Programmablee movements movements
Constant speed drives
Variable speed drives
Mechanical synchronization
Electronic synchronization
Rigid heavy structures
Lighter structures
Accuracy racy deter termined ned mechanism Manual controls
by
toleran erance ce
of Accuracy achieved by feedback Automatic and programmable controls
