Digital Control of Multiaxial-Motion System*

Abstract The paper deals with simultaneous control of multi-axial motion (linear, or also circular in a planar system) in machine tools. Currently, in N.C. machines each axis is controlled separately, with speed commands given by a small computer (interpolator) mostly of the DDA type. In the proposed device, all axis control loops are unified in a single system by means of an additional loop for each pair of axes, so that a load disturbance (or any other) in a motor loop is corrected not only by the loop involved but by the system as a whole. The result is improved path accuracy in contouring. The proposed system involves time-varying gains, preferably realized by means of additional DDA integrators connected to those forming the interpolator. By this means, the instantaneous information recorded on the additional integrators is updated, permitting satisfactory follow-up even in the case of sine-wave inputs. Two auxiliary circuits - a decelerator (comprising an additional DDA integrator) and a frequency divider - are used to prevent overshooting following a stop command, thereby contributing to improved product accuracy.