New results are summarized which extend the
Evans root locus design technique to fully coupled, twochannel
control law architectures. The new results are
based upon various root migration plots, and the
underlying framework concerning how the plots
influence one another, for the closed-loop poles and
zeros in each channel, as key system gains are varied.
Instead of traditionally closing one feedback loop at a
time to build-up a multi-loop system, the new theory
facilitates closure of all loops simultaneously, allowing
efficient assessment of stability and performance in all
channels. The closed-loop pole migration behavior is
uniquely interesting in that poles "track moving zeros".
Atypical root migration features include direction
reversal on real axis loci. Root locus sketching rules
for this new framework are developed to assist the
designer in implementing gain and compensation
strategies by anticipating effects upon system stability
and performance. The new theory is demonstrated with
a lateral-directional flight control example.