  This paper describes the design and implementation of linear controllers with
a switching condition for a nonlinear hot air blower system (HABS) process
trainer PT326. The system is interfaced with a computer through a USB based
data acquisition module and interfacing circuitry. A calibration equation is
implemented through computer in order to convert the amplified output of the
sensor to temperature. Overall plant is nonlinear; therefore, system
identification is performed in three different regions depending upon the plant
input. For these three regions, three linear controllers are designed with
closed-loop system having small rise time, settling time and overshoot.
Switching of controllers is based on regions defined by plant input. In order
to avoid the effect of discontinuity, due to switching of linear controllers,
parameters of all linear controllers are taken closer to each other. Finally,
discretized controllers along with switching condition are implemented for the
plant through computer and practical results are demonstrated.
