Book Analog Interfacing to Embedded Microprocessors
The software
must insure that all these special requirements are met, and that a change
from one state to another (such as from one heated material to another)
does not cause the PID loop to be confused. You don’t want to use an
integral value calculated using one set of PID parameters to generate an
output when the PID parameters change. When PID parameters are changed
for any reason, the software needs to reset or otherwise adjust the accumu-
lated values.
Motor Control
So far we have used heaters as the primary example for control system
operation, because they are easy to understand. The control methods
described in this chapter apply to motors as well, but there are some
additional complications when motors are involved. Figure 5.15 shows a
PID loop controlling a motor. The input to the system is a digital word that
indicates the desired position. The motor position is an analog quantity
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