sensors 3
TRANSCRIPT
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Sensors (v.1c) 1
CENG4480_A1Sensors
Sensing the real world
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Sensors (v.1c) 2
Sensors
Motion (Orientation/inclination )sensorsForce/pressure/strainPositionTemperature and humidityRotary positionLight and magnetic field sensors
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Sensors (v.1c) 3
Motion (Orientation/inclination sensors
Acceleration GyroscopeCompassTilt Sensor
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Sensors (v.1c) 4
Accelerometerhttp://en.wikipedia.org/wiki/Accelerometer
Functions: measure acceleration in one or more directions,
position can be deduced by integration. Orientation sensing : tilt sensor Vibration sensing
Methods: Mass spring method ADXL78 (from Analog Device )
Air pocket method (MX2125)
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Sensors (v.1c) 5
ADXL78 (from Analog Device http://www.analog.com/UploadedFiles/Data_Sheets/ADXL78.pdf )Mass spring type (output acceleration in G)Measure the capacitance to create output
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ADXL330 accelerometer for three (X,Y,Z ) directions http://www.analog.com/UploadedFiles/Data_Sheets/ADXL330.pdf
3D
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2D translational accelerometerMX2125 (from www.parallax.com)
Gas pocket typeWhen the sensor
moves, the temperatures of the 4 sensors are used to evaluate the 2D accelerations
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Sensors (v.1c) 8
Accelerometer demo:orientation sensing
http://www.youtube.com/watch?v=9NEiBDBXFEQhttp://www.youtube.com/watch?v=VP4-wdMMLFo
Self-balance RobotSensor demo
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Sensors (v.1c) 9
Accelerometer demo :Tilt sensing demo
http://www.youtube.com/watch?v=C6uVrYz-j70
Tilt sensing demo
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Sensors (v.1c) 10
Gyroscopes http://en.wikipedia.org/wiki/Gyroscope
Gyroscope Measure rotational angle
Rate Gyroscope measure the rate of rotation along 3-axes of X
(pitch), Y (roll), and Z (yaw). Modern implementations are using
Microelectromechanical systems (MEMS) technologies.
Gyroscope
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Sensors (v.1c) 11
FEATURES Complete rate gyroscope on a single chip Microelectromechanical systems (MEMS) Z-axis (yaw-rate) response
APPLICATIONS GPS navigation systems Image stabilization Inertial measurement units Platform stabilization
Gyroscope to measure Rational acceleration ADXRS401 http://www.analog.com/UploadedFiles/Data_Sheets/ADXRS401.pdf
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Compass-- the Philips KMZ51 magnetic field sensor
50/60Hz (high) operation, a jitter of around 1.5°
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Sensors (v.1c) 13
Rate gyroscope demo
http://www.youtube.com/watch?v=VP4-wdMMLFoUsing Gyroscope compass for virtual reality application in an iphone
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Application of motion sensorsSelf balancing robot
by Kelvin Ko http://hk.youtube.com/watch?v=2u-EO2FDFG0
20cm
20cm
35cm35cm
Motion sensors: gyroscope and accelerometer
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Complementary filterComplementary filter
Since Since
Combine two sensors to find outputCombine two sensors to find output
1515
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Sensors (v.1c) 16
Complementary filterComplementary filterθθ=rotation angle, =rotation angle, =filter time constant, s=laplace =filter time constant, s=laplace operator operator http://en.wikipedia.org/wiki/Low-pass_filterhttp://en.wikipedia.org/wiki/High-pass_filterhttp://en.wikipedia.org/wiki/High-pass_filter
1616
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Self Balanced robot using Self Balanced robot using complementary filtercomplementary filter
1717
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Tilt Sensor by OMRONhttp://rocky.digikey.com/WebLib/Omron%20Web%20Data/D6B.pdf
Detect tilting 35 ~ 65 degrees in right-and-left inclination
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Force/pressure/strain
Force-sensitive resistor (FSR)Strain gaugeFlexionAir pressure
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Force Sensing Resistorshttp://www.interlinkelectronics.com/library/media/papers/pdf/fsrguide.pdf
FSR402
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Force Sensing Resistor Demo
http://www.youtube.com/watch?v=LQ21lXr6egs
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Application for a walking robot
Walking robot
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Application of force sensing resistance sensors to balance a walking robot
Balancing Floor tilled rightupper leg bend left
Floor tilled leftupper leg bend rightNeutral position
Four sensors under the foot
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Four Force sensors under the foot
D
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The Nao robot uses force feedback at its feet http://en.wikipedia.org/wiki/Nao_(robot)
http://www.robotshop.com/Images/xbig/fr/robot-humanoide-nao-edition-academique-v3plus-aldebaran.jpg
http://www.youtube.com/watch?v=2STTNYNF4lk
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Strain Gauge : Force sensorshttp://www.meas-spec.com/myMeas/default/index.asp
Piezoelectric crystal: produces a voltage that is proportional to force applied
Strain gauge: cemented on a rod. One end of the rod is fixed, force is applied to the other end. The resistance of the gauge will change with the force.
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Single element strain gauge
sensitive to temperature change.
resistance gauge unstrainedR
gauge theof length Lfactor, gauge strainG and G for
4424220
LL
RR
LLGVb
RRVb
RRRV
RRR
RRVV bb
Vb
R
R R
Gauge=R+Rgauge
load
rodV0
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Four-element (Wheatstone bridge) strain gauge sensor, Four times more sensitive than single gauge system; not
sensitive to temperature change. All gauges have unstrained resistance R.
LLGV
RRV
RRRRRR
RRRRRRVV bbb 2
20
b1=R-Rt2=R+ R
b2=R-R t1=R+RVb
t1 t2
b1 b2
rod
load
V0
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Flexion (bend) sensors
resistance: 10 KΩ (0°); 30-40 KΩ (90°) http://www.flexpoint.com/
http://www.jameco.com/wcsstore/Jameco/Products/ProdDS/150551.PDF
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Felixon resistance Demo
http://www.youtube.com/watch?v=m4E5SP7HCnk&feature=related
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Sensors (v.1c) 31
Air pressure sensor
Measure up to 150 psi (pressure per square inch ).
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Sensors (v.1c) 32
Position sensors
Infra-red range sensorLinear and Rotary position sensors
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Sensors (v.1c) 33
Infra-red Range detectors by SHARP (4 to 30cm) http://www.acroname.com/robotics/info/articles/sharp/sharp.html
An emitter sends out light pulses. A small linear CCD array receives reflected light.
The distance corresponds to the triangle formed.
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IR radar using the Sharp range detector
http://www.youtube.com/watch?v=tStBLAiQaC8&feature=related
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Position sensors, from[1]
Rotary Linear
Optical shaft encoder
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Magnetic rotary encoder(http://www.renishaw.com/UserFiles/acrobat/UKEnglish/L-9517-9147.pdf)
non touch sensing
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Optical rotary encoder(http://en.wikipedia.org/wiki/Rotary_encoder)
The light received (on or off) will tell the rotation angle)
3 light emitters
3 light receivers
Rotation shaft
Light paths
http://www.youtube.com/watch?v=RuIislTGOwACrank shaft sensor
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Temperature and humidity
Temperaturehumidity
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Sensors (v.1c) 39
Temperature sensorsLM135/235/335 features(from NS)http://www.national.com/pf/LM/LM135.html
Directly calibrated in °Kelvin 1°C initial accuracy available Operates from 400 µA to 5 mA Less than 1 Ohm dynamic impedance Easily calibrated Wide operating temperature range 200°C over range Low cost
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Application note (connecting to an ADC e.g. ADC0820 or ADC0801)
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Capacitive Atmospheric Humidity Sensorhttp://rocky.digikey.com/WebLib/BC%20Components/Web%20Data/2322%20691%2090001.pdf
BCcomponents 2322 691 90001 10-90%RH Dc
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Leaf Sensor Alerts When Plants Are Thirsty
http://www.youtube.com/watch?v=VM4X_fqPPco
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TSL250, TSL251, TSL252LIGHT-TO-VOLTAGE OPTICAL SENSORShttp://focus.ti.com/general/docs/scproducts.jsp
Light-to-voltage optical sensors, each combining a photodiode and an amplifier (feedback resistor = 16 MW, 8 MW, and 2 MW respectively).
The output voltage is directly proportional to the light intensity on the photodiode.
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Cadmium Sulfoselenide (CdS) Photoconductive Photocellshttp://faculty.uml.edu/aelbirt/16.480/pdvp5001.pdf
Light sensing using CdS
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Hall effect Sensors for sensing magnetic flux“B field”, see: http://doc.semicon.toshiba.co.jp/noseek/us/td/td2frame.htm
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Application on Magnetic levitation 磁懸浮http://myweb.msoe.edu/~muthuswamy/pubs/DesignOfMagneticLevitationControllersUsingJacobiLinearizationFeedbackLinearizationAndSlidingMode.pdf
http://www.youtube.com/watch?v=XjjBqzilkIc
Magnetic levitation Train Model 磁懸浮火車
http://www.youtube.com/watch?v=TeS_U9qFg7Y
frog levitationhttp://www.youtube.com/watch?v=A1vyB-O5i6E
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Hall effect sensors and brushless DC motors
Brushless DC motor
• http://dev.emcelettronica.com/files/u4/Brushless_DC_Motors_bldc_motor.jpg
Is it using Hall effect sensor? Don't known.
http://www.youtube.com/watch?v=JmRkxZT4XhYhttp://www.youtube.com/watch?v=cm0h2Qf3upQ
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Novel sensors
Kinect
http://www.youtube.com/watch?v=nvvQJxgykcU http://www.youtube.com/watch?v=Mf44bWQr3jc
http://www.ladyada.net/learn/diykinect/
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Many KINECT DIY projects
http://www.youtube.com/watch?v=Brpu30vjCa4&feature=related
http://www.youtube.com/watch?v=3V-TGXFZbbA&feature=related
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Control systemsExample: A temperature control
system
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Control example: Temperature control system
Temp.Sensor A/D
CPU
D/APulse Width modulation
& solid state relayHeater
Timer
Sample&
Hold
Digital controlcircuit
Instrum. amp.
Water tank
computer
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Temperature control method 1: ON-Off (bang-bang) control (poor)
Easy to implement, bad control result -- contains overshoot undershot. Algorithm for on-off-control:
Loop forever: If (Tfrom_sensor > Treq required temperature) then (heater off ) else (heater on).Treq
Undershoot
Overshoot
Time
TempOn-off control result
Steady state error
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Temperature control method 2 : Proportional-integral-differential (PID) temperature control (good)
Init. (set required temperature Treq)Loop forever{
get temperature T from sensor, e=T - Treq then Tw =e*G*{Kp+Kd*[d(e)/dt] +Ki*e dt } else
} //G,Kp,Kd,Ki can be adjusted by user
Tw
Tw
Proportional, differential, integral
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PID block diagram
http://www.controlviews.com/question12-12-03.html
Figure 1 - Parallel PID block diagram
Kd
Ki
Kp
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PID control using pulse width modulation PWM
Fixed period and fixed number of pulses
Tw (depends on e )
Treq
PID control resultof method 2
On-off control: oscillates and unstable
Time
Temperature
Time
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Summary
Studied the characteristics of various sensors
and their applications
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References [1] S.E. Derenzo, Interfacing -- A laboratory
approach using the microcomputer for instrumentation, data analysis and control prentice hall.
[2] D.A. Protopapas, Microcomputer hardware design, Prentice hall
[3] CUHK_FYP report HML0602, KHW0703 [4] http://www.engin.umich.edu/group/ctm [5] http://en.wikipedia.org/wiki/PID_controller