Transcript Document

CS 546: Intelligent Embedded
Systems
Gaurav S. Sukhatme
Robotic Embedded Systems Lab
Center for Robotics and Embedded Systems
Computer Science Department
University of Southern California
[email protected]
http://robotics.usc.edu/~gaurav/CS546
Administrative
• The CS dept is working on a bigger room for
the class
• The class cap has been raised to 45
• Is there anyone here
– who has not yet filled the questionnaire ?
– who has filled the questionnaire and not got a
response from me ?
– who wants to be in the class, and is not on the
class mailing list ?
Today
• Overview of the ENS box (Richard Pon
and Jeff Tseng, Aevena)
• TinyOS tutorial
• Homework #2
– Karthik will give a brief explanation
– Homework is online on the class website
• Sensing, sensor calibration, and
actuation basics
Homework #2
• Karthik just gave you details
• Due a week from today – no extensions
Last week
Energy supply
Memory
Processor
External
communication
Interface
Sensor and
actuator suite
Figure adapted from [Pottie and Kaiser 2005]
•Platform
•OS and SW architecture
•Tools
•User interface
•Application
Today
Energy supply
2/21: Energy management
4/18: Cyclops
External
communication
1/31: Networking
Memory
Processor
Interface
Sensor and
actuator suite
1/24, 4/18: Cyclops
Figure adapted from [Pottie and Kaiser 2005]
•Platform
•OS and SW architecture
•Tools
•User interface
•Application
2/7,14 and 28:
Time synch, localization and
data management
3/21,28 and 4/11:
Environmental monitoring
Sensors
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Basic principles
Noise and figures of merit
Types of sensors
Calibration
Sensing Architecture
Physical signal
at source
Physical signal
at transducer
Signal
channel
Transducer
A/D conversion
Analog signal
procesing
Digital signal
processing
Feedback
transducer
network
Output
signal
Sources of Noise
Physical signal
at source
Physical signal
at transducer
Signal
channel
Transducer
A/D conversion
Analog signal
procesing
Digital signal
processing
Feedback
transducer
network
Output
signal
Figures of Merit
• Responsivity:
output signal/input signal
• Sensitivity:
(output signal without input)/(responsivity)
• Drift: slow change in output due to lowfrequency noise
• Cross talk
Types of Sensors
• Environmental
– Pressure, gas phase composition, automotive exhaust gas
oxygen,
• Motion and force
– Accelerometers, rotation and rotation rate, piezoresistive
strain, microphone, capacitative position
• Electromagnetic transducers
– Antennas, magnetometers, digital cameras. laser
rangefinders
• Chemical and biochemical
– Oxygen, nitrate (amperometric)
Transduction Principles
• Pressure – capacitance change
• Gas – absorption changes conductivity
• Accelerometer and rate gyros – proof mass
displacement changes
• Microphone – diaphragm displacement changes
resistance
• Piezoelectric – force changes polarization charge
• Magetometer – motion wrt coil induces a current
• Camera – photodetectors and CCD arrays
• Nitrate – use microfluidics to reduce an electrode and
measure current
Calibration
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Compare measurements to a reference
Performed while manufacturing
Tuning parameters (say a resistor)
Need calibration methods in situ
Usually non-linear interpolation
Next time
• Network and programming models