Page 59 - Modern Control Systems

Section 1.10 Sequential Design Example: Disk Drive Read System 33

/(;) Insulin
Programmed
• delivery
signal generator
rate
(a)

Insulin
Motor, delivery Human
v(t) pump, rate body, Actual
Amplifier
and blood, and
level
valve pancreas
FIGURE 1.27
(a) Open-loop > j Sensor
(without feedback) ( ^ Measured glucose level
control and
(b) closed-loop Desired glucose level
control of blood
glucose. Cb)

have concentrated on increasing data density and data access times. Recent trends
show that hard disk drive densities are increasing at about 40 percent per year [62],
Figure 1.28 shows the disk drive density trends. Designers are now considering em-
ploying disk drives to perform tasks historically delegated to central processing units
(CPUs), thereby leading to improvements in the computing environment [63].Three

•Jr

FIGURE 1.28
Disk drive data
density trends 1980 1955 1990 1995 2000 2005 2010
(Source: IBM). Production (Year)