Using Predictive Techniques within CNC Machine Tools Feed Drives

The paper presents a hierarchical predictive control architecture dedicated to axis feed drives of machining centres. The primary level is built with Generalized Predictive Control (GPC) strategy, without considering any constraints action. The controller is formulated under the polynomial RST form, as a convenient framework for CNC systems. Robustification of this controller towards measurement noises that often drastically affect machine-tool environment is also examined. This basic level is further enhanced with a predictive-based mechanism allowing constraints avoidance by an adequate local change of the tool path. Finally, if this is action is not sufficient, as the full path during machining is known, an advanced constraints avoidance option is added, that may recompute the whole remaining trajectory with a lower speed profile. This strategy is validated in a virtual machining centre.