Optimal Preview Control of Cutting Force in CNC Turning Machines

Abstract

In this paper, a new linearized state-space model for a Computerized Numerical Control (CNC) turning machine is synthesized. The linearization is implemented using a factorization method in which the feed is divided into two terms. The first term is the measurable part of the integer feed and the second is a fractional of feed, which will be calculated. An optimal preview controller for the CNC machine is implemented. A new error system technique is introduced into the control system to cure the adverse phenomena that is caused due to parameter uncertainties, un-mode led dynamics and disturbances. The disturbances comprise material properties, depth of cut and tool conditions while the un-modeled dynamics to dispense with the fractional feed. A preview feed-forward controller utilizing the desired cutting force is designed to improve the transient response of the CNC control system. The robustness of the proposed controller copes with any changes in depth of cut and/or cutting speed during the cutting process where they are embedded in the linearized model of the CNC machine and are considered as system parameters.