User`s guide

Hard-Disk Read/Write Head Controller
9-21
Using the values kg , Nm/(rad/sec), Nm/rad,
and Nm/rad, form the transfer function description of this system.
At the MATLAB prompt, type
J = .01; C = 0.004; K = 10; Ki = .05;
num = Ki;
den = [J C K];
H = tf(num,den)
MATLAB responds with
Transfer function:
0.05
-----------------------
0.01 s^2 + 0.004 s + 10
The taskhere is todesign adigitalcontroller thatprovidesaccurate positioning
of the read/write head. The design is performed in the digital domain. First,
discretize the continuous plant. Because o ur plant will be equipped with a
digital-to-analog converter (with a zero-order hold) connected to its input, use
c2d with the 'zoh' discretization method. Type
Ts = 0.005; % sampling period = 0.005 second
Hd = c2d(H,Ts,'zoh')
Transfer function:
6.233e–05 z + 6.229e–05
-----------------------
z^2 – 1.973 z + 0.998
Sampling time: 0.005
J 0.01
=
m
2
C 0.004
=
K 10
=
K
i
0.05
=