REDUCING CUTTING FORCE INDUCED BORE CYLINDRICITY ERRORS BY LEARNING CONTROL AND VARIABLE DEPTH OF CUT MACHINING

In this paper a method for on-line compensation of cyclindricity error s in machined bores is formulated and demonstrated The cyclindricity e rrors addressed are those caused by the elastic deformation of the bor e wall dire to forces applied to the workpiece both during and after t he machining process. Compensation is achieved using a piezoelectric b oring bar servo capable of varying the depth of cut rapidly for on-lin e compensation at acceptable industrial machining speeds. Control of t he boring bar servo consists of both learning and repetitive control. Learnirrg control is used to determine the cutting tool reference traj ectory? required to achieve compensation, and repetitive servo control is used to accurately track the reference trajectory. The stability a nd convergence of the el l-ou dynamics of the learning control system are analyzed using a model for the flexure-induced machining errors. E xperimental results demonstrate that the proposed method can significa ntly improve bore cylindricity in machined components.