User`s guide

9 Design Case Studies
9-10
This is the root locus for negative feedback and shows that the system goes
unstable almost immediately. If, instead, you use positive feedback, you may
be able to keep the system stable.
rlocus(–sys11)
sgrid
This looks better. Just using simple feedback you can achieve a damping ratio
of . You can graphically select some pole locations and determine the
corresponding gain with
rlocfind.
[k,poles] = rlocfind(–sys11)
ζ
0.45
=