OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
Maslab — Sensors 2009
Bhaskar Mookerji
6.186 Mobile Autonomous Systems Laboratory
5 January 2009
Bhaskar Mookerji Sensors 2009 (1/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
1 OverviewuOrc LayoutElectrical SafetyDigital InputsCable Assembly
2 Primary SensorsBarrier Range/Reflectance: InfraredOdometry: Optical EncodersBarrier Contact: Bump SensorsAngular Velocity: MEMS GyroscopeOdometry: IR Optical Encoders
3 Other Ideas and Reminders(Favorite Example Hack) USB Mouse OdometryPhototransducers, etc.Reminders
4 uOrc Errata!Bhaskar Mookerji Sensors 2009 (2/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
uOrc LayoutElectrical SafetyDigital InputsCable Assembly
Power
switch
5V
Power
Supply
Three Bidirectional
Motor Drivers
Qu
adP
has
e
BatteryConnector
Reset Digital Periph.Ethernet
RJ−45
ARM
JTag Header
Ser
vo
An
alo
g
I/O
I/O
Input
I/O
Wall Wart
Bhaskar Mookerji Sensors 2009 (3/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
uOrc LayoutElectrical SafetyDigital InputsCable Assembly
Don’t do anything that will harm you or the OrcBoards.Avoid shorts: Use electrical tape on back of the OrcBoard.Avoid ground loops: Keep cables short, twisted.Check polarity of connections. Insert sensors with theOrcBoard off.Connect to power LAST.
Bhaskar Mookerji Sensors 2009 (4/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
uOrc LayoutElectrical SafetyDigital InputsCable Assembly
Low-pass filter onanalog/IOBuilt-in (approximate)current sense (AllMotors, servos 0/1)12-bit, 400Hz ADC,CMOS/TTL compatible:
Bump sensorsHall magneticsensorsReed switches, etc.
Bhaskar Mookerji Sensors 2009 (5/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
uOrc LayoutElectrical SafetyDigital InputsCable Assembly
Bhaskar Mookerji Sensors 2009 (6/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
uOrc LayoutElectrical SafetyDigital InputsCable Assembly
Suggestions:Use 1/4" stranded wireTin wire leads and headerProtect connections with heatshrink (hot air gun)Plastic header melts easilyReinforce connections with hot glue (avoid shorting)Color code consistently for polarity (e.g., Ground–Black,+5V–Red, etc.)
Bhaskar Mookerji Sensors 2009 (7/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
uOrc LayoutElectrical SafetyDigital InputsCable Assembly
Bhaskar Mookerji Sensors 2009 (8/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
uOrc LayoutElectrical SafetyDigital InputsCable Assembly
SolderingKeep wet sponge for cleaning iron tipHeat joining surfacesBeware joint oxidation and other bad connections:
See:http://www.sparkfun.com/commerce/hdr.php?p=tutorials
http://orcboard.org/documentation/soldering.pdf
Bhaskar Mookerji Sensors 2009 (9/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
Barrier Range/Reflectance: InfraredOdometry: Optical EncodersBarrier Contact: Bump SensorsAngular Velocity: MEMS Gyroscope
IR sensors (λ = 850± 70nm):IR pulse is emittedLens transmits reflected lightonto linear CCD arrayAngle of reflected light→barrier range
Two types:GP2D12 (short range)GP2Y0A02YK (long range)
Bhaskar Mookerji Sensors 2009 (10/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
Barrier Range/Reflectance: InfraredOdometry: Optical EncodersBarrier Contact: Bump SensorsAngular Velocity: MEMS Gyroscope
Non-linear response: accuracy, resolution, and rangeShort-readings look far away
Bhaskar Mookerji Sensors 2009 (11/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
Barrier Range/Reflectance: InfraredOdometry: Optical EncodersBarrier Contact: Bump SensorsAngular Velocity: MEMS Gyroscope
Bhaskar Mookerji Sensors 2009 (12/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
Barrier Range/Reflectance: InfraredOdometry: Optical EncodersBarrier Contact: Bump SensorsAngular Velocity: MEMS Gyroscope
Beam football-shaped, widest in the middle at 16cmWide beam pattern in front/sides of robot using servos
Bhaskar Mookerji Sensors 2009 (13/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
Barrier Range/Reflectance: InfraredOdometry: Optical EncodersBarrier Contact: Bump SensorsAngular Velocity: MEMS Gyroscope
Reflectivity sensor for a disk with black/white colored wedges
Two single encoders: π/2 phase difference to distinguishfoward/backward movement:
Bhaskar Mookerji Sensors 2009 (14/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
Barrier Range/Reflectance: InfraredOdometry: Optical EncodersBarrier Contact: Bump SensorsAngular Velocity: MEMS Gyroscope
Quadrature phase detection for:Relative positioningVelocity control and feedback (PID controller). This, likevision, can detect stalling (important).Mapping and odometry
Bhaskar Mookerji Sensors 2009 (15/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
Barrier Range/Reflectance: InfraredOdometry: Optical EncodersBarrier Contact: Bump SensorsAngular Velocity: MEMS Gyroscope
Very reliable barrierdetectionSpring-loaded NESbuttonsOr, fabricate your ownwhisker switches
Bhaskar Mookerji Sensors 2009 (16/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
Barrier Range/Reflectance: InfraredOdometry: Optical EncodersBarrier Contact: Bump SensorsAngular Velocity: MEMS Gyroscope
Non-inertial referenceframe: Coriolisacceleration:a = −2 (v × ω)
Orc samples at full ADCrate, integratesSlow turns, noise,integration → driftImportant for:
Dead reckoning withother sensorsFeedback: Straightlines, turns
Bhaskar Mookerji Sensors 2009 (17/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
(Favorite Example Hack) USB Mouse OdometryPhototransducers, etc.Reminders
Read PS/2 protocol from /dev/mouse0
Java FileInputStream returns encoded (dx ,dy)bytestream
See:http://www.microsoft.com/whdc/device/input/mcompat.mspx
http://www.computer-engineering.org/ps2mouse
Bhaskar Mookerji Sensors 2009 (19/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
(Favorite Example Hack) USB Mouse OdometryPhototransducers, etc.Reminders
Ball detection? Breakbeam sensorDebugging? LED lightingStalling? Don’t let this happen to you!
Bhaskar Mookerji Sensors 2009 (20/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
(Favorite Example Hack) USB Mouse OdometryPhototransducers, etc.Reminders
RemindersStart early.Mind the size of your robot, camera calibration, and thelimits of your sensors.Competition is timed, program accordingly.Sensors can be noisy or fail entirely, depending on howyou use them.Use Athena SVN repositories for backup/version control.Read past journals/papers.Ordering new parts? (under $100!)
http://www.allelectronics.com/http://www.mcmaster.com/
Bhaskar Mookerji Sensors 2009 (21/23)
OverviewPrimary Sensors
Other Ideas and RemindersuOrc Errata!
Java got you down? Try Ed Faulkner’s Java tutorial!http://maslab.lcs.mit.edu/2004/lectures/javareference.txt
uOrc’s self-assigned IP address—192.168.1.7. Toconnect your EeePC and the uOrc on the same localnetwork, sudo ifconfig eth0:1 192.168.1.100.Updates are still being made to orc.jar (.java):
CameraDigitalInput, DigitalOutput
Easy way to disable default Gnome display:sudo apt-get install rcconf; sudo rcconfDisable gdm in menu.
Bhaskar Mookerji Sensors 2009 (23/23)