This document discusses various types of sensors used in mechatronic design and control systems. It describes sensors for measuring position, speed, proximity, displacement, force, pressure, temperature and light. Specific sensors covered include LVDT, RVDT, eddy current, capacitive, inductive, Hall effect, strain gauge, optical encoder, photoemitter-detector, piezoelectric and tactile sensors. Applications are provided for different sensors in areas like level measurement, machine tools, assembly lines, hydraulic cylinders and automated inspection. Characteristics of sensors like sensitivity, linearity, range, accuracy and response time are also summarized.

1. Mechatronic design

2. Design process
• Need
• Analysis
• Preparation of specification
• Conceptual stage
• Selecting a solution
• Production (prototype)
• Wkg dwg

4. Modelling systems
• Response not instantaneous
• Relating output with input
• Steady state and transient

6. Control systems
• Open loop
• Closed loop

7. MECHATRONICS
Session 5
BOOKS
W. BOLTON, MAHALIK, Rajput. R.K,

8. Closed loop
• Basic elements
• Comparison element
• Control element
• Correction element
• Process element
• Measurement element

9. Control system
• Analogue
• Continuous fun of time which measures variable
• Signals are converted to digital using ADC

10. Ctrl sys
• Digital
• Sequence of ON/OFF signals
• Converted to analog using DAC

11. Example

12. Shaft speed control

13. Washing machine

14. Auto focus camera

15. • Sensors
• Transducer
• Smart Sensor

16. sensors
• Classification
• Displacement
• Proximity
• Velocity
• Force
• Fluid pressure
• Temperature
• Light sensors

17. Sensors- Characteristics
• Static
• Steady state characteristics
• Dynamic
• Time between and steady state

18. Terminology
• Range and Span
• Accuracy
• Sensitivity
• Error
• Hysteresis
• Non linearity
• Repeatability
• Dead band
• Resolution

19. sensors
displ proximity velocity flow temp light

20. Static Characteristics
• Sensitivity
• Ratio of change in output to change in input
• Output per unit input
• Also used to indicate factors affecting sensors

21. • Linearity
• Constancy of output to input ratio
y= cx
• Range
• Diff between max and min value measured

22. • Accuracy
• Difference between measured and actual value
• It is dimensionless value
• Repeatability
• Difference in value between two measurement under same conditions

23. • Resolution
• Minimum change of input detected at output of sensing system
• No of measurement with in a range
• Output
• In any form mechanical, electrical ( voltage o/p)

25. Dynamic characteristics
• Response time
• Time to respond (95% of inp value steady state)
• Time constant
• Inertia of sensor ( 63.2 % of steady state)
• Rise time
• Time for rise of output (10% -90% of steady state)
• Settling time
• Time for output to settle ( 2% of steady state)

26. Measurement system
system sensor transducer Display

27. SENSORS
TYPE SENSOR
NAME
MAT
USED
APPLICATION

28. Level Measurement
• Direct Methods
• 1.Bob and tape method
• 2.Sight glass method
• 3.Float type method
• Indirect Methods
• 1.Pressure gauge method
• 2.Manometric level method
• 3.Diaphragm box method
• 4.Air trap method

29. LVDT

32. RVDT

33. OUTPUT (LVDT RVDT)

34. EDDY CURRENT SENSORS
• Coil carrying current produces mag field
• Eddy currents are induced when is metal close,
• Eventually producing mag field, distorting the field
produced by current carrying coil
• It triggers a switch at threshold
• Used in non magnetic ,conductive environment
• Highly reliable and sensitive

35. Position and Speed Measurement
• By position measurement we may need to check
• If a part is reached a predefined location or not
• The total displacement of the part
• Both the measurements are again divided in two types
• Linear
• Angular/ Rotary

37. Capacitive

39. Applications
• These sensors are primarily used in the control systems with a
feedback loop to ensure that the moving member or component
reaches its commanded position.
• machine-tool controls, elevators, liquid-level assemblies, forklift
trucks, automobile throttle controls
• woodworking machinery, printing, spraying, robotics

42. Applications
• Feed hopper level monitoring
• Small vessel pump control
• Grease level monitoring
• Assembly line testing o to test assembled parts for uniformity,
thickness or other design features
• to analyze and optimize the rotation of spindles in various machine
tools such as surface grinders, lathes, milling machines, and air
bearing

43. Proximity Sensors
• Activating a switch by a presence of object
• Reed switch
• Mag contact sealed in glass tube
• Switch close when mag brought near
• Used in tachometers , as sensors in pneumatic eqpts
• Microswitch
• Small electrical requiring small force to close
• Detects presence of object by its weight
• Lever , roller , cam operated

44. Reed switch & photo detector

45. Eddy current

46. Application
• Eddy current proximity sensors are used to detect non-magnetic but
conductive materials. They comprise of a coil, an oscillator, a detector and
a triggering circuit
• Automation requiring precise location
• Machine tool monitoring
• Final assembly of precision equipment such as disk drives
• Measuring the dynamics of a continuously moving target, such as a
vibrating element,
• Drive shaft monitoring
• Vibration measurements

47. Inductive

48. • the coil, oscillator, detection circuit and output circuit. An alternating
current is supplied to the coil which generates a magnetic field.
When, a metal object comes closer to the end of the coil, inductance
of the coil changes.
• Applications of inductive proximity switches
• Industrial automation: counting of products during production or
transfer
• Security: detection of metal objects, arms, land mines

49. Hall effect
• Observed and discovered by Hall in 1880s
• Beam of charged particles deflects when passes through mag field
• Two fields – electric and magnetic field
• Magnetic field due to pot diff being applied
• Electric field due to charge separation
• Two types linear and threshold

50. Hall effect sensor

52. Hall effect sensor

53. Applications
• Measurement of spool position in a wide range of servo valve applications
• To provide displacement feedback for hydraulic cylinders
• To control weight and thickness of medicinal products viz. tablets or pills
• For automatic inspection of final dimensions of products being packed for
dispatch
• To measure distance between the approaching metals during Friction
welding process
• To continuously monitor fluid level as part of leak detection system
• To detect the number of currency bills dispensed by an ATM

54. Strain Gauge
• The Gauge Factor for metallic strain gauges is typically around 2

55. Strain gauge

56. Applications
• Strain gauges are widely used in experimental stress analysis and
diagnosis on machines and failure analysis
• bending and deflection measurement, compression and tension
measurement and strain measurement.
• force measurement in machine tools
• impact sensors in aerospace vehicles

57. Optical encoder
• Absolute and incremental encoder
• Senses both speed and direction of rotation
• Detected by no of pulses captured by sensor
• Three concentric tracks
• Home , direction and speed
• Output in terms of binary num of digits (000, 011)
• Sequential output from slots with 10 tracks
• 10 tracks give 10 bits = 210 = 1024 positions
• Resolution of 360/10= 0.350

58. Encoder

59. SPEED MEASUREMENT
• Speed measurements can be obtained by taking consecutive position
measurements at known time intervals and computing the ‘time
rate’of change of the position values.
• Tachometer is an example of speed sensor which does the same
thing for a rotating shaft.

60. photoemitter-detector

63. piezoelectric
• Generates electric charge when stretched or compressed with +ve & -
ve charge in opp faces
• Ionic crystals , charge distribution when stretched or compressed
• Used in measurement of pressure , force , acceleration

64. Tactile sensor

65. Tactile sensor
• A pressure sensor
• PVDF – polyvinylidene fluoride( piezo)
• Touch display, fingertip of robot hands
• Two layers of PVDF separated by soft film
• When pressure is applied on upper layer of PVDF vibrations are
affected , changing output voltage