Replies to This Discussion

Permalink Reply by Eddie Furey on July 17, 2012 at 7:14pm

Just get the ArduPilot Mega 2.0. It will do everything you want, and more, and is in a convenient and tested package. No messing around joining all the components together yourself.

That said, afaik...

Stability requires gyros.

Heading can be calculated from GPS as long as you're moving, otherwise compass.

Pitch and roll require an accelerometer. Yaw I guess you'd need to calculate from GPS heading vs compass heading?

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Permalink Reply by James Kirkley on July 17, 2012 at 8:55pm

Thanks Eddie.

Yes, I'm going to get an APM 2.0.

But being a tinker at heart, I like to figure out how all this stuff works together.

GPS, altitude, air speed, ground speed...those are easy concepts for me to get my head around.

But I think I need to read this particular section of the forum on IMU's...to get educated.

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Permalink Reply by Derek Ernewein on July 17, 2012 at 10:00pm

Gyroscopes can tell a change in angle, but they don't 'remember' what angle they are at.
Accellerometers measure changes in speed and their direction.
Gyroscopes+Accellerometers gives you real stability. Here is a video thhat explains them both very well: http://www.youtube.com/watch?v=s19W-MG-whE

I agree, go with the ArduPilot Mega 2.0. It has gyros, accelerometers, barometer, magnometer (compas) and GPS is optional (built in or external).

If you want to know heading and roll/pitch/yaw from the ground then you will also need telemetry. You can do this several ways. Through video and an OSD (On Screen Display) or with two way radios like Xbee (or 3DR Radio) along with a PC running Ardupilot Mission Planner.

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Permalink Reply by Jake Stew on July 17, 2012 at 11:18pm

You don't have to choose.  Your two good options are STmicro and Invensense.  Both use a two chip solution to give a 9DOF IMU.

STmicro has a accel+mag chip and a gyro chip.  Invensense has a gyro+accel chip and you can a mag from another vendor.

STmicro has an actual sensor fusion and AHRS code solution that runs on their STM32 processors.  Invensense has been touting a vaporware solution for years, but no actual sensor fusion processor has materialized and most likely doesn't exist IMHO.

ST chips are cheaper, but most autopilots have gone with Invensense since they've been making good IMU chips a bit longer.

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Permalink Reply by James Kirkley on July 18, 2012 at 7:59am

Thanks guys,

I think I'm starting to understand a bit better.

 

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