ABSTRACT:
This work deals with the experimental implementation of a state space
controller for a DC motor that has separate winding excitation. The
output to be controlled is the rotor position. Linux and RTAI-Lab are
the open source tools that we use in this implementation. The control
law is derived by using a model that consists in a set of ordinary
differential equations. Additionally, in order to avoid several issues
regarding the measurement of the state variables, we implement an
experimental discrete-time state observer to estimate the transient
values of the rotor speed, armature current and even the load torque.
The armature voltage is defined as a function of estimated states
excepting the rotor position, which is the only state variable that
is measured. The real time program calculates the discrete-time state
feedback including an integrator, a full order discrete-time state
observer and a rotor position sensing algorithm. In our case, a set of
five difference equations (fifth-order discrete time dynamical system)
is computed every 0.2 milliseconds (5 kHz). Important components of
the experimental set-up are: a personal computer, a National
Instruments PCI-6024E data acquisition card, comedi driver library for
Linux, RTAI-Lab, a custom-made power electronics converter, an
incremental encoder and signal conditioning circuits for measuring the
rotor position. Custom-made digital, analog and power electronics
designs are fundamental components of the hardware used in this closed
loop implementation.