Transcript Sensor Fusion

Sensor Fusion
Donald Heer
11/10/10
The Questions
Can two things happen at the ‘same’ time?
Can the same thing be observed ‘identically’ by two different
observers?
Example
You are designing a system that measures ‘instantaneous power’
of a AC circuit. You are using a current sensor and a voltage
sensor fed into a microcontroller. Can you display ‘instantaneous
power’?
Discuss in your groups
What Contributes to Timing Error?
ADC Timing
Microcontroller Processing
Wire delay
Does it even matter though? Discuss.
What is ‘instant enough’?
Depends on specifications
Another Example
You are tasked with building a dead reckoning device. This
system has a digital compass, a GPS, a 3 axis accelerometer, and
a 3 axis gyroscope. The device will be installed on an off road
buggy the can reach speeds of 60mph.
Specifics
GPS – Accurate with in 10M, 10Hz refresh
Accelerometers – Accurate with in .001Gs, 1KHz refresh rate
Gyroscopes – Accurate within .1ft/sec/sec, 1KHz refresh rate
Digital Compass – accurate with in 1 degree, 100Hz refresh rate
Come up with some rules to combine these inputs into a single
‘picture’ of where the buggy is. Discuss
Which Sensors are More Useful?
GPS? Only on rough terrain or when moving fast
Accelerometers? Update fast, but noisy
Gyroscopes? Measures rotation, but drifts over time
Digital Compass? Only gives direction
Take Away
Be sure you know if you need ‘simultaneous’ measurements, or
what error you can accept
If needed, use one sensor to confirm another