LowPassFilter as ProcessObject

[Ben van Basten]

Hello,

I just finished my override to the GroundReactionWrenchFilter that calculates the CoP instead of the PWA. (Arnaud, we can do the comparison to OpenMA as discussed here, if you like. I can even provide you with the FinishGRWComputation() of my class (which is the only thing changed wrt the btk::GroundReactionWrenchFilter implementation). I compared the results to Visual3D, and they were the same.

Now, I would like to have the global wrenches both filtered AND unfiltered. 

My personal experience is that filtering of global moments and CoP might not be optimal due to numerical issues in case of small forces. 

Therefore, I am planning to add a LowPassFilterProcessObject inbetween btk::ForcePlatformsExtractor and "my" GroundReactionWrenchFilter: I filter the "base" forces and moments first, and then compute the global forces, moments and CoP in the GroundReactionWrenchFilter. I can do the same thing without the filtering and end up with both filtered and unfiltered wrenches.

So, 

ForcePlatformsExtractor -> LowPassFilter->CoPGroundReactionWrenchFilter -> filltered wrenches

ForcePlatformsExtractor -> CoPGroundReactionWrenchFilter -> unfilltered wrenches

My question is,

- Would this be a good approach? 

- And does such a low-pass ProcessObject (that filters the force components) already exist in BTK? Surely I won't be the first...

Regards,

Ben van Basten