New to the forums.. questions about AQ6 GPS+INS fusion

[aharmon]

Hello,

I am new to the multi-rotor world, and interested in learning more about the GPS-INS sensor fusion employed by the AQ6 FC. I hope I'm not violating your forum policies by asking where to find information, but I had no luck using the search utilities on the website..

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Could someone please point me to any resources/ documentation where I can read about the sensor fusion that the AQ6 flight controller implements to integrate the UBLOX LEA-6T and DIMU?

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Background:

While I am new to multi-rotors and the RC world, I eat nonlinear filters for breakfast, and I have several years of experience writing filters for GPS-INS state estimation.

I discovered AutoQuad while poking around online. I have been developing algorithms for multi-rotor control as a hobby, doing simulations and trade studies, getting ready to buy hardware. For me, the fun is in the sensor fusion algorithm development and the nonlinear control design. I don't want to just drop a control board on a frame and have something that flies; the fun part for me is going through the systems engineering activities of developing performance metrics and error budgets, and then writing estimators, algorithms, and controllers to meet the specified design criteria. E.g. I want to design a stochastic linear quadratic controller by modeling the moments and products of inertia of the airframe, characterizing the motor inertia, damping, and engine thrust, and placing the PVA eigenvalues where I want them.

I'm excited about the AQ6 platform because it's open-source firmware will allow me to play with the parts of the system that interest me (sensor fusion and control) without spending hours and hours on a ground-up hardware design (a huge win!). I can't wait to get started!

[bn999]

Howdy. The state estimate filter that I designed for AQ was originally based on the work of Rudolph van der Merwe. A most useful document is his 2004 PhD thesis "Sigma-Point Kalman Filters for Probabilistic Inference in Dynamic State-Space Models" and can be found here:



There is no formal documentation for the AQ implementation other than the source code itself, which is relatively well commented. Most of the work went into making the UKF fit into the computational constraints of the MCU. The rest was determining the variance and noise parameters that hold everything together.

On the control side, we have developed a quaternion based adaptive attitude control system we call Quatos. Although it is not generally available quite yet, it may soon be.

[kinderkram]

Welcome to AutoQuad, aharmon!

Sounds like the AQ will be the ideal playground for you - Im pretty sure you´ll find the Quatos quite interesting.

Norbert

[aharmon]

[bn999]

[sandmen]

If it's possible, keep this thread here.

[phynix]

I would also like to follow (quietly) your explanations / discussions, even so I just started reading through the code.

[srinath]

I would like to work on the ukf documentation too. It also estimates GPS latency.
I started the ukf documentation about 2 years ago, but left it midway. Would be good to pick up where I left off

[Max]

Excellent info here, please keep.

-Max

[chestnut]

I love UKF very much, and I have been researching UKF for 3 years, but still not really understand.