Contouring control of machine tool feed drive systems: A task coordinate frame approach

In this paper, we will show that contouring performance can be viewed as a regulation problem in a moving task coordinate frame that is attached to th e desired contour. By transforming the machine tool feed drive dynamics to this task coordinate frame, a control law is designed to assign different d ynamics to the tangential and normal directions. The transformation also il lustrated the effect of contour curvature and feed rate in the control acti on as well as the system dynamics in the task coordinate frame. The resulti ng control law consists of a linear time-varying proportional-plus-derivati ve (PD) position error feedback control law and a linear time invariant tra jectory feedforward control law. Experimental results of the proposed contr ol law on the motion axes of a machining center, Matsuura MC510V, showed si gnificant improvement of the contouring accuracy compared to the existing s ervo controller as well as the successful decoupling between the tangential dynamics and the normal (contouring) dynamics for feedrate up to 6 m/min ( 4 in/s).