PLC and Fuzzy Logic Control of a Variable Frequency Drive

Abstract—This work deals with the control of a VFD which acts as an intermediary between a three-phase induction motor and the PLC. The induction motor drives a conveyor belt which has three proximity sensor inputs. The first sensor gives the signal for motor to move in the forward direction, the second sensor halts the conveyor for a pre-defined period of time and the third sensor gives the signal for motor to move in the reverse direction. The PLC takes these inputs from the sensors and takes an appropriate action based on the logic developed for the motor control. Finally, the PLC output then becomes the VFD input, which after being reprocessed within the drive brings about the necessary control of the motor with respect to speed and position. In addition, Fuzzy Logic has also been applied to the system so that it can be trained to predict a reasonable output for even those inputs which were not foreseen by the network, therefore making the system flexible and easy to predict the result for various operating conditions