|
This experiment demonstrates
process dynamics and control concepts.
A solution of methylene blue dye is
pumped through a computer-driven control valve. The solution mixes with water
from the mains and enters a small glass vessel equipped with a valved bypass
line. Effluent from the vessel flows through a cuvette mounted in a modified
spectrophotometer. The spectrophotometer signal is sent via an A/D board to a
computer, where it is processed by a program which implements a PID control
algorithm to drive the valve.
The students choose the water flow
rate, set point, and proportional and integral gains, and then make a run in
which the dynamic response of the system is recorded. When the vessel is not
bypassed, the system is more difficult to control. The set point and gains may
be changed in the middle of a run.
A specially designed injector is provided with which
the students can also study the system's impulse response. Varying water flow
rates and resident volumes may be used, and system volume calculated from the
classical response to dye injection.
|
