Nonlinear State-Space

Spitsplat

Anyone have any good online sources for nonlinear state-space modeling?

I need to place nonlinear UAV dynamics into state-space form for modelling and seriously running out of good reference material for information.

Cyrus

Are you trying to linearize the dynamics model?

Spitsplat

I have to try and place it into non linear State-Space form first if that is possible. We have a new control Algorithm so we are taken on a Quad-rotor UAV as a case study.
I have uploaded the dynamics equations to flickr.... If you could cast an eye over it and give your opinion it would be great:

http://www.flickr.com/photos/spitsplat/

For the control Algorithm to work we require 6 inputs and 6 outputs from a MIMO State-Space model of the UAV Dynamics. For 6 inputs, and for an academic exercise, we have decided to make the rotors pitchable (opposed rotors coupled).
So the inputs become (S1-S3), (S2-S4),(S1+S3), (S2+S4), Alpha and Beta.
Any help would be great.... Hopefully we’ll get the thing of the ground and I’ll post the video’s on youtube.

Brian_C

I recently developed a Matlab simulation of a quadrotor with aerodynamic effects for a flight mechanics class. Quadrotor dynamics have been extensively studied by a bunch of different research groups, most notably the STARMAC group at Stanford. The linearized equations of motion without aerodynamic effects can easily be found in the literature.

The problem with quadrotor UAV's is that the rotor thrust varies with forward airspeed and angle of attack. This leads to erratic fluctuations in the climb rate of the vehicle. You might should try implementing the wind estimation/rejection algorithm discussed in the following paper:

http://pdf.aiaa.org/preview/CDReadyM...V2009_1983.pdf

Spitsplat

Hey Thanks,

Worth adding into the model so will have a look over it.

We just placed the model under feedback control using our Algo. still suffering from some instability later down the runtime of the simulation but we''ll hopefully sort it soon.