14-07-2012, 04:01 PM
Robot Sensors
[attachment=27685]
Robot Sensors
Why do Robots Need Sensors?
What can be Sensed?
What Sensors are Out There?
What can They do?
How Much do They Cost?
How Easy are They to Use?
Why Do Robots Need Sensors?
Provides “awareness” of surroundings
What’s ahead, around, “out there”?
Allows interaction with environment
Robot lawn mower can “see” cut grass
Protection & Self-Preservation
Safety, Damage Prevention, Stairwell sensor
Gives the robot capability to goal-seek
Find colorful objects, seek goals
Makes robots “interesting”
Sensors - What Can Be Sensed?
Light
Presence, color, intensity, content (mod), direction
Sound
Presence, frequency, intensity, content (mod), direction
Heat
Temperature, wavelength, magnitude, direction
Chemicals
Presence, concentration, identity, etc.
Object Proximity
Presence/absence, distance, bearing, color, etc.
Physical orientation/attitude/position
Magnitude, pitch, roll, yaw, coordinates, etc.
Sensors - What Can Be Sensed?
Magnetic & Electric Fields
Presence, magnitude, orientation, content (mod)
Resistance (electrical, indirectly via V/I)
Presence, magnitude, etc.
Capacitance (via excitation/oscillation)
Presence, magnitude, etc.
Inductance (via excitation/oscillation)
Presence, magnitude, etc.
Other Things?
What Sensors Are Out There?
Feelers (Whiskers, Bumpers) – Mechanical
Photoelectric (Visible) – Active & Passive
Infrared (light) – Active & Passive
Ultrasonic (sound) – Active & Passive
Sonic – Active & Passive
Resistive/Capacitive/Inductive – Active & Passive
Visual – Cameras & Arrays (Active & Passive)
Color Sensors (Active & Passive)
Magnetic (Active & Passive)
Orientation (Pitch & Roll)
GPS (location, altitude)
Compass (orientation, bearing)
Voltage – Electric Field Sensors
Current – Magnetic Field Sensors
Chemical – Smoke Detectors, Gas Sensors
Sensors – Feelers
Whiskers
Piano wire suspended through conductive “hoop”
Deflection causes contact with “hoop”
Springy wire that touches studs when deflected
Reaches beyond robot a few inches
Simple, cheap, binary output
Bumpers & Guards
Impact/Collision sensor, senses pressure/contact
Microswitches & wires or framework that moves
Simple, cheap, binary output, easy to read
Sensors – IR
Active (emitting)
Oscillator generates IR reflections off objects
Filtered receiver looks for “reflections”
Pulses may be encoded for better discrimination
Typically frequencies around 40KHz
Doesn’t work well with dark, flat colored objects
Passive (sensor only)
Pyro-electric (heat sensor)
Look for IR emissions from people & animals
Used in security systems & motion detectors
Active IR Sensor Specs
Sensor type = Reflective IR
IR detector = Panasonic PNA4602M
IR LED type = Narrow focus 10º
I/O required = 3 digital lines: 2 outputs, 1 input
Range = Approximately 4“ to 26"
Input voltage = 5vdc regulated @ 8mA
PC board size = 2.3" x .75"
Linear Array IR Range Sensors
Sharp GP2Dxx (one of many)
~4 to 30cm Range
Fixed Range with Discrete Output
Analog or Digital Output
Easy to Use
Laser Range Sensors
USB Interface
240º Field of View
0.36º Angular Resolution
10Hz Refresh Rate
20mm to 4m
$2695 (cool but pricey)
Also See:
Oct 2001 Encoder
Kenneth Maxon
Sensors – Ultrasonic
Active
Emit pulses & listen for echos
Times round trip sound travel (~1ft/mS)
Reaches far fairly beyond robot (inches to 30-50’)
Relatively simple, not cheap, analog output
Directional; not everything reflects sound well
Passive (listens only)
Sensor listens for ultrasonic sounds
Electronics may translate frequency or modulation
Software may perform signal analysis (FFTs, etc.)
Sensors – Ultrasonic (cont.)
Passive - Beacons & Sensors
Beacons listen: RF command to broadcast
Send light & sound pulses
Robot looks & listens for each beacon
Light pulse starts timer, sound pulse stops it
Robot knows location of each beacon
Compass on robot provides its orientation
Robot computes distance, measures bearing
Robot can then compute its location
(Speed of Light=1 ft/nS, Speed of Sound=1ft/mS)
Sensors – Sonic (Acoustic)
Active
Emit pulses & listen for echos
Times round trip sound travel (~1ft/mS)
Reaches far fairly beyond robot (30-50 ft)
Relatively simple, not cheap, analog output
Directional, not everything reflects sound
Noisy!!!!
Passive (sensor only)
Sensor listens to ambient sounds
Filters or scans selected frequencies
ADC measures conditioned signal amplitude
CPU performs signal analysis on what it hears
Sensors – Resistance
Passive (sensor only)
Measures elec. resistance between objects
Measure sensor that varies resistance
Use absolute or differential readings
Other ideas?
Sensors – Capacitive
Passive
Really doesn’t work (Needs excitation)
Active (emitting)
Generate AC or DC voltage
Apply to external environment
Measure current to determine Resistance
Short range applications
Sensors – Inductive
Passive
Really doesn’t work (Needs excitation)
Active (emitting)
Current flows through inductor
Magnetic field mostly ignores non-metals
Inductance changes with metallic proximity
Short range applications
Sensors – Visual
Active (emitting)
Camera with field of view illumination
Looks for particular reflections
Filter removes non-significant light sources
Linear array senses single axis of motion
Passive (camera only)
Scans field of interest
Looks for objects, artifacts, features of interest
Processes digital data to simplified interpretation
Sensors – Color
Active (emitting)
Selective field illumination (specific color(s))
Sensor filter removes extraneous light sources
Output can be analog (prop.) or digital (on/off)
Passive (sensors only)
Different sensors for different colors
Color filter removes extraneous light sources
Output can be analog (prop.) or digital (on/off)
Sensors – Magnetic
Active (emitting)
Metal detectors
Follows metallic strips on or under the floor
Magnetometer
Magnetic Resonance Imaging (MRI)
Passive (sensors only)
Compass
Magnetic field sensor (→oscillating current)
Sensors – Orientation
Rate Gyros
Output proportional to angular rotation speed
Integrate to get position
Differentiate to get acceleration
DC Accelerometer
Output proportional to sine of vertical angle
Sensors – Position/Location
Wheel Encoders
Relative position & motion
Integrate/Differentiate for other parameters
Global Positioning System
Absolute position/location on earth
Local differential error correction
Integrate/Differentiate for other parameters
Sensors – Conclusion
Sensors provide a way of simulating “aliveness”
Sensors give robots environmental awareness
Sensors provide of means of human protection
Sensors help robot preserve itself
Sensors enable goal seeking
Sensors enable closed-loop interaction
Sensors make robots interesting
Sensors can make programming “challenging”
Parallax Sensor Sampler - $165
Memsic 2125 Accelerometer
Sensirion Temperature and Humidity Sensor
Flexiforce Demo Kit
PING))) Ultrasonic Sensor
PIR Sensor
Hitachi HM55B Compass Module
Hitachi H48C Tri-Axis Accelerometer Module
Piezo Film Vibra Tab Mass
QTI Sensor (IR Surface Color)
[attachment=27685]
Robot Sensors
Why do Robots Need Sensors?
What can be Sensed?
What Sensors are Out There?
What can They do?
How Much do They Cost?
How Easy are They to Use?
Why Do Robots Need Sensors?
Provides “awareness” of surroundings
What’s ahead, around, “out there”?
Allows interaction with environment
Robot lawn mower can “see” cut grass
Protection & Self-Preservation
Safety, Damage Prevention, Stairwell sensor
Gives the robot capability to goal-seek
Find colorful objects, seek goals
Makes robots “interesting”
Sensors - What Can Be Sensed?
Light
Presence, color, intensity, content (mod), direction
Sound
Presence, frequency, intensity, content (mod), direction
Heat
Temperature, wavelength, magnitude, direction
Chemicals
Presence, concentration, identity, etc.
Object Proximity
Presence/absence, distance, bearing, color, etc.
Physical orientation/attitude/position
Magnitude, pitch, roll, yaw, coordinates, etc.
Sensors - What Can Be Sensed?
Magnetic & Electric Fields
Presence, magnitude, orientation, content (mod)
Resistance (electrical, indirectly via V/I)
Presence, magnitude, etc.
Capacitance (via excitation/oscillation)
Presence, magnitude, etc.
Inductance (via excitation/oscillation)
Presence, magnitude, etc.
Other Things?
What Sensors Are Out There?
Feelers (Whiskers, Bumpers) – Mechanical
Photoelectric (Visible) – Active & Passive
Infrared (light) – Active & Passive
Ultrasonic (sound) – Active & Passive
Sonic – Active & Passive
Resistive/Capacitive/Inductive – Active & Passive
Visual – Cameras & Arrays (Active & Passive)
Color Sensors (Active & Passive)
Magnetic (Active & Passive)
Orientation (Pitch & Roll)
GPS (location, altitude)
Compass (orientation, bearing)
Voltage – Electric Field Sensors
Current – Magnetic Field Sensors
Chemical – Smoke Detectors, Gas Sensors
Sensors – Feelers
Whiskers
Piano wire suspended through conductive “hoop”
Deflection causes contact with “hoop”
Springy wire that touches studs when deflected
Reaches beyond robot a few inches
Simple, cheap, binary output
Bumpers & Guards
Impact/Collision sensor, senses pressure/contact
Microswitches & wires or framework that moves
Simple, cheap, binary output, easy to read
Sensors – IR
Active (emitting)
Oscillator generates IR reflections off objects
Filtered receiver looks for “reflections”
Pulses may be encoded for better discrimination
Typically frequencies around 40KHz
Doesn’t work well with dark, flat colored objects
Passive (sensor only)
Pyro-electric (heat sensor)
Look for IR emissions from people & animals
Used in security systems & motion detectors
Active IR Sensor Specs
Sensor type = Reflective IR
IR detector = Panasonic PNA4602M
IR LED type = Narrow focus 10º
I/O required = 3 digital lines: 2 outputs, 1 input
Range = Approximately 4“ to 26"
Input voltage = 5vdc regulated @ 8mA
PC board size = 2.3" x .75"
Linear Array IR Range Sensors
Sharp GP2Dxx (one of many)
~4 to 30cm Range
Fixed Range with Discrete Output
Analog or Digital Output
Easy to Use
Laser Range Sensors
USB Interface
240º Field of View
0.36º Angular Resolution
10Hz Refresh Rate
20mm to 4m
$2695 (cool but pricey)
Also See:
Oct 2001 Encoder
Kenneth Maxon
Sensors – Ultrasonic
Active
Emit pulses & listen for echos
Times round trip sound travel (~1ft/mS)
Reaches far fairly beyond robot (inches to 30-50’)
Relatively simple, not cheap, analog output
Directional; not everything reflects sound well
Passive (listens only)
Sensor listens for ultrasonic sounds
Electronics may translate frequency or modulation
Software may perform signal analysis (FFTs, etc.)
Sensors – Ultrasonic (cont.)
Passive - Beacons & Sensors
Beacons listen: RF command to broadcast
Send light & sound pulses
Robot looks & listens for each beacon
Light pulse starts timer, sound pulse stops it
Robot knows location of each beacon
Compass on robot provides its orientation
Robot computes distance, measures bearing
Robot can then compute its location
(Speed of Light=1 ft/nS, Speed of Sound=1ft/mS)
Sensors – Sonic (Acoustic)
Active
Emit pulses & listen for echos
Times round trip sound travel (~1ft/mS)
Reaches far fairly beyond robot (30-50 ft)
Relatively simple, not cheap, analog output
Directional, not everything reflects sound
Noisy!!!!
Passive (sensor only)
Sensor listens to ambient sounds
Filters or scans selected frequencies
ADC measures conditioned signal amplitude
CPU performs signal analysis on what it hears
Sensors – Resistance
Passive (sensor only)
Measures elec. resistance between objects
Measure sensor that varies resistance
Use absolute or differential readings
Other ideas?
Sensors – Capacitive
Passive
Really doesn’t work (Needs excitation)
Active (emitting)
Generate AC or DC voltage
Apply to external environment
Measure current to determine Resistance
Short range applications
Sensors – Inductive
Passive
Really doesn’t work (Needs excitation)
Active (emitting)
Current flows through inductor
Magnetic field mostly ignores non-metals
Inductance changes with metallic proximity
Short range applications
Sensors – Visual
Active (emitting)
Camera with field of view illumination
Looks for particular reflections
Filter removes non-significant light sources
Linear array senses single axis of motion
Passive (camera only)
Scans field of interest
Looks for objects, artifacts, features of interest
Processes digital data to simplified interpretation
Sensors – Color
Active (emitting)
Selective field illumination (specific color(s))
Sensor filter removes extraneous light sources
Output can be analog (prop.) or digital (on/off)
Passive (sensors only)
Different sensors for different colors
Color filter removes extraneous light sources
Output can be analog (prop.) or digital (on/off)
Sensors – Magnetic
Active (emitting)
Metal detectors
Follows metallic strips on or under the floor
Magnetometer
Magnetic Resonance Imaging (MRI)
Passive (sensors only)
Compass
Magnetic field sensor (→oscillating current)
Sensors – Orientation
Rate Gyros
Output proportional to angular rotation speed
Integrate to get position
Differentiate to get acceleration
DC Accelerometer
Output proportional to sine of vertical angle
Sensors – Position/Location
Wheel Encoders
Relative position & motion
Integrate/Differentiate for other parameters
Global Positioning System
Absolute position/location on earth
Local differential error correction
Integrate/Differentiate for other parameters
Sensors – Conclusion
Sensors provide a way of simulating “aliveness”
Sensors give robots environmental awareness
Sensors provide of means of human protection
Sensors help robot preserve itself
Sensors enable goal seeking
Sensors enable closed-loop interaction
Sensors make robots interesting
Sensors can make programming “challenging”
Parallax Sensor Sampler - $165
Memsic 2125 Accelerometer
Sensirion Temperature and Humidity Sensor
Flexiforce Demo Kit
PING))) Ultrasonic Sensor
PIR Sensor
Hitachi HM55B Compass Module
Hitachi H48C Tri-Axis Accelerometer Module
Piezo Film Vibra Tab Mass
QTI Sensor (IR Surface Color)