Specifications

Hard-Disk Read/Write Head Controller
10-23
step(Hd)
The system oscillates quite a bit. This is probably due to very light damping.
You can check this by computing the open-loop poles. Type
% Open-loop poles of discrete model
damp(Hd)
Eigenvalue Magnitude Equiv. Damping Equiv. Freq.
9.87e-01 + 1.57e-01i 9.99e-01 6.32e-03 3.16e+01
9.87e-01 - 1.57e-01i 9.99e-01 6.32e-03 3.16e+01
The poles have very light equivalent damping and are near the unit circle. You
need to design a compensator that increases the damping of these poles.
Thesimplestcompensatoris justa gain,sotrytherootlocustechniqueto select
an appropriate feedback gain.