Optimum, machine tool axis traverse regulation

Abstract

A hybrid, distributed parameter model for a milling machine axis drive system is derived from measured results. Spatial variation effects arising from the machine system geometrical changes are incorporated enabling multivariable regulation via feedback control. Design procedures enabling the realization of an optimum, minimum energy, multivariable regulator for this system are presented. Table velocity and lead-screw twist interaction are controlled via armature and field voltage variations, restricting the effect of cutting loads and lead-screw length changes, respectively. The feedback compensators for this system are evaluated and the open and closed-loop model response transients, following reference input variations, are presented. Disturbance suppression and the surface finish capabilities of the closed-loop, minimum energy, system, were investigated. The performance advantages promoted by multivariable minimum effort control are emphasized with the confinement of lead-screw wind-up and cutting load disturbance effects whilst limiting output cross coupling with improving transient behaviour and steady state accuracy.