Reaction-force space / Spatial algebra

I have a query related to SPATIAL ALGEBRA,KINEMATIC LOOPS and JOINT REACTION-FORCE. 
Read on if you're still interested!

I've been reading "Robot Dynamics Algorithms" -what a great book- and am
having a problem with the reaction-force space. This is represented by a
matrix orthogonal to the joint-space matrix and is denoted R in
Featherstone's book. Anyhow, you need to calculate "velocity-product"
terms Ra + R'v as part of a kinematic loop resolution algorithm... this
is a step that confuses me because I'm not sure how to calculate R' (the
derivative of R). Its straightforward apparently, and includes the term
v X R... if you have a copy of the book I'm looking at page 164.

So if spatial algebra and joint reaction-force are concepts under your
command please give me a shout and I'll explain myself in more detail if
necessary!

Thanks,

Josh.

-- 
Joshua G. Hale, Ph.D.                  +44(0)141 3398855 ext 0209
Boyd Orr 420, Computing Science Dept., +44(0)141 3303119 (FAX)
University of Glasgow,                 [email protected]
Glasgow G12 8QQ, SCOTLAND              www.joshhale.com