Comparative Study of PID, PD-FLC and PID-FLC for Active Magnetic Bearing

Abstract

In this manuscript, a closed loop active magnetic bearing system (AMB) is proposed, dynamically modelled and linearized in form of unstable transfer function. To achieve proper bearing operation, the proposed AMB system is controlled by two separate controllers, one to control the current in the electromagnet coils by forming an inner closed loop and second to stabilize the position of the suspending object at equilibrium. To maintain the position of suspending object at equilibrium, for the proposed AMB system (considering inner closed loop as unity) a conventional PID controller, a PD-fuzzy logic controller (PD-FLC) and a PID-fuzzy logic controller (PID-FLC) is designed and their performance is observed and compared. Later, the effect of designed controllers on the complete proposed AMB system is studied with the help of control system plots and improvement among their performances is observed. The plotted step responses and calculated transient state parameters will verify that by changing the conventional PID controller to a PID-FLC could result in 48.34% improvement in overshoot, 41.52% increment in speed of response and 32.23% increment in the relative stability.