Questions and discussion for this lecture live here. Fire away by hitting Reply below 
Hi Sean,
I got a bit confusing about your Remove ENA from member actions part.
We convert the ENA_local and calActions_local matrix to the global coordinator. And then we convert the finalActionsLocal from global coordinator back to the local coordinator. Why do we have to do that? Cos I think both ENA_local and calActions_local are in the local coordinator.
Hey @trongnhanhpf,
Great question - in this case, this is a redundant step! As you’ve correctly identified, you don’t need to convert from local to global and back to local again…we could just remove the influence of ENA in the local reference frame.
So, your understand is correct - you’re not missing anything!
So, where/why did the conversion to global come from?!
Because we’re only dealing with one member at a time (i.e. all of the operations in a single iteration of the for loop only apply to a single member, as mentioned, the conversion is a redundant step.
Where conversion to a common global RF is helpful is when we’re trying to combine actions from multiple members that may be at different orientations in space (not the case here). Converting everything to a common RF is important in that case for simple arithmetic to be applied.
I’m generally in the habit of doing any operations in a common global RF which is probably why I did that here…a bit confusing I now appreciate! Thanks for asking the question…it will help plenty of other people I’m sure!
S
I got it. Thank you so much for helpful information!