[Rock-dev] RigidBodyState - Uncertainty and Composition

[Javier Hidalgo Carrió]

On 10/23/2012 04:58 PM, Leif Christensen wrote:
> Am 23.10.2012 16:22, schrieb Javier Hidalgo Carrió:
>> I want to extend RigidBodyState class, adding composition of Rigid
>> Bodies States as operator *
>> using the already implemented solution of envire
>> (TransformWithUncertainty class) which handles this as a first order
>> approximation of Jacobians which perfectly maps to the covariance
>> matrices of the existing class.
> What about non-parametric filters, for example histogram or particle
> filters? Do they also have to be covered by the * operator?
The operator * would just perform the composition of two rigid body states.
How you computed the uncertainties is another different question. For 
it,  you could use filters mentioned above (particle, histogram, kalman 
or whatever ) this is an estimation problem depending on the probability 
distribution that better model your case.

However, at the end logging to a port it will be stored in a covariance 
matrix (e.g.: base::Matrix3d cov_position of the RigidBodyState class) 
which assume a mean and a (co)-variance w.r.t to the mean (which is a 
Gaussian distribution).
If you have a clear no Gaussian pdf as an output of a particle filter I 
would not use RigidBodyState to represent the uncertainty (I guess must 
be another class in rock for that)

This is how I understand RigidBodyState: Let's have the opinion of more 
people, perhaps, they had something different in mind to it.

>   Obviously,
> there is no need for jacobians there and they don't have covariance
> matrices, but use the RigidBodyState. Are they covered somewhere else,
> or do we just overload the operator then? Or am I completely on the
> wrong track?
>
> Leif
>

Nevertheless, I could see more problematic how to propagate values as 
velocity and angular_velocity of the RigidBodyState when the composition 
* would be computed.

Javier.