Design of a Fuzzy-Based Controller for Real-Time Control of CNC Machines

In a typical computer numerically controlled (CNC) machine, the servodrive system is an important component that directly affects the accuracy of the machine. Its function is to generate and convert command signals to machine motion; and to eliminate errors that are generated during the axis motion. By noting that the errors generated are accumulative, therefore any error that is generated in real time because of lack of accurate axis motion or interpolator malfunction will have a profound effect on the quality of parts produced. This paper is focused on controller design aspect of the feeddrive unit and a physical model of the feedrive system is used to do the simulation study. Controller design is based on fuzzy set theory which as opposed to conventional approaches does not require in depth understanding of dynamics of the system. In this regard, the elements of the controller are developed and used to study its performance. Axis motion is attained by controlling position based on the control output which uses error and its derivative in fuzzy domain about a predefined trajectory. Simulation results demonstrating satisfactory performance of the feedrive system in tracking the desired trajectory are reported