Microcomputer as a Programmable Controller for State Feedback Control of a DC Motor Employing Thyristor Amplifier

A microprocessor-based state feedback control of a single-phase thyristor bridge/dc motor drive system is presented. Considering the drive system as a regulator problem in multivariable system theory, suitable control laws are developed using a state space model and applying a pole placement technique for fast regulation coupled with system stability by state feedback. To improve the response further, feedforward control is included in the control law so that the output follows the reference with minimum delay. A minimal order observer is also incorporated to make a quick estimate of the armature current (assumed to be inaccessible) from the knowledge of output speed and inputs of the system. Finally, the controller including the feedback control, feedforward control, and minimal order observer has been implemented in real time using an Intel 8085 microprocessor kit with suitable interfacing and standard software package. The experimental setup is fabricated and tested, and the test results are compared with digital simulation results for step changes in reference and load torque.