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