What telemetry systems are usually included in a UAV setups?
There must be a heiarcy of which instrumentation to choose first.
I know I want to fly waypoints, so the GPS is a requirement.
Barometers and airspeed indicators are a one off. Get them if you want them.
This leaves the sticky wicket:
1. I want a "stability mode".
2. I want an indicator of "the heading" in near realtime.
3. I want an indicator of "pitch", "roll", and "yaw" in near realtime.
So which to choose: the 3-axis gyros, 3-axis compass, or the 3-axis accelerometer?.
What are the pros and cons of each?
What are the redundancies?
Maybe a combination is best?
Which gives the best realtime indications?
Which holds it accuracy the best over time.
Which has a tendency to wander?
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?
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.
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.
I think I'm starting to understand a bit better.