FUZZY LOGIC PID SPEED CONTROLLER FOR BRUSHLESS DC MOTOR DRIVES

Abstract:
A simple but robust fuzzy speed controller for the brushless dc motor drives is
proposed. The output is adjusted by fuzzy rules according to the current value of the
speed error and the associated rate of change. Using only five triangular membership
functions with twenty-five rule-base inference engine, the implementation of the
controller was made possible. The proposed controller mixes two control actions, the
fuzzy logic controller as proportional derivative control action and a non-fuzzy integral
controller to eliminate the steady state error. The overall controller design is equivalence
to proportional-integral-derivative (PID) controller. The fuzzy logic controller plays the
main role and the added integral controller is just to provide a variable bias to eliminate
the steady state error at every load condition. The sampling time in the designed
controller is 200 􀈝s. Which allows the use of low speed-processing device in the
implementation of the control algorithm. The proposed speed controller succeeded in
controlling the speed of a brushless dc motor over all operating speed range of the drive.
From the response results, it is found that the controller operates like adaptive
controllers but without the complication needed to do it adaptively. The performance of
the proposed controller was assessed in terms of several simulation cases. The
responses due to step set point change and load disturbance showed that the proposed
controller is controlling the speed of the brushless dc motor drive with fast nonoscillatory
behavior. The proposed controller makes the control system response similar
over a wide range of operating points.