Re: [Bayes++] Square-root UKF

[Michael S. <ma...@mi...>]

On Thursday 11 January 2007 18:20, Matt Hazard wrote:
> One more idea.
>
> Would a full dynamic model of the airframe be necessary in an indirect
> formulation? It seems like you'd only be correcting the inertial navigation
> solution with the aiding sensors - only requiring an error model.

Nothing is made 'necessary' by the indirect formulation. In it simpliest form 
it is mathematically (though not numerically) the same as a simple direct 
filter. It does however allow you more flexibility in the state 
representation and how it is updated.



> A tightly-coupled filter with a nonlinear dynamics model of the airframe
> could use the control surface deflections as inputs in the predict_model,
> and the inertial and aiding sensors as measurements in the observe_model,
> correct?

To use gyro rates and acceleration as observation you need to represent them 
in the state vector. This requires a 15 variable state composed of position, 
velocity, acceleration, attitude, and attitude rate! Possible on a modern 
computers.

> It's a more complicated system, but wouldn't the specification of 
> the system dynamics model improve the results?

Hard question to answer on paper! Possibly. It would require a lot of work to 
model the sensors and dynamics such that the filter would work with the 
observation. Possibly you would not gain anything of much value for 
navigation but data that could be used by the controller.


All the best,
	Michael
-- 
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Michael Stevens Systems Engineering

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Navigation Systems, Estimation  and
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