Imu

[chopsuey]

What does an IMU consist of? 3 accelerometers and 3 gyros? A microcontroller of some sort to make sense from the sensors, do some magic (kalman filter?) and output something usable? I think rotomotion use to make some but I can find them on their site anymore. How many degrees of freedom are required for a UAV (plane)? Does anyone have any links where I can learn more about IMUs? Sorry about all the questions I am just curious how these work.

[mportobello]

Yup, you've got it. The sensors measure the direction of gravity to determine how your plane is oriented. The gyros respond quickly to change but drift. The accelerometers are slow to measure changes, but do not drift. The kalman filter magic combines these two sensor readings to give the best of both.

A 3 acceleromter/3 gyro IMU will give you 6 degrees of freedom. I think for most planes you don't absolutely need to measure yaw so you can get away with a 5 degree of freedom IMU.

The first post in the forum called "Stick: UAV Links" contains a lot of information.