Control Enhancement of Cutting Force in CNC Turning Machines Based on a New MRAS

Abstract

ABSTRACT Controlling the cutting force in machining is a challenging problem since the cutting dynamics varies significantly under normal operating conditions. In this paper, a linearized state-space model for a Computerized Numerical Control (CNC) turning machine is synthesized. A model reference adaptive control system (MRAS), which includes the cutting force as a controlled output and the feed rate as a control input, is implemented. The deterministic autoregressive moving average (DARMA) model with auxiliary input is introduced to cope with any disturbances of the system. The parameters of the DARMA model are obtained using the structure of a lattice adaptive control system. A minimum variance controller is designed to maintain the cutting force at a prescribed level by adjusting the feed rate. The robustness of the proposed controller copes with any changes in depth of cut and/or the cutting speed. These changes are embedded in the Iinearized model of the CNC machine and are considered as system paran1eters. Extensive computer simulations are made to prove the applicability of the proposed controller for controlling the cutting force over different operating conditions.