Method for ascertaining a rough trajectory from a specified contour

A system for controlling a machine tool, the system comprising:

• the machine tool comprising at least two mutually redundant drive devices for carrying out superimposed movements following a contour function;
• and
• a computer numerical control (CNC) device configured to:
• determine a specified contour for controlling the machine tool by the contour function defined in portions by contour nodal points (P0-Pn+1) with ascending indices and contour portion functions (p0-pn) assigned to the contour nodal points (P0-Pn+1) and has a contour starting nodal point (P0),
• determine a rough trajectory by a rough trajectory function defined in portions by rough trajectory nodal points (Q0-Qn+1) with ascending indices, the rough trajectory having a rough trajectory starting nodal point (Q0),
• equate the rough trajectory starting nodal point (Q0) to the contour starting nodal point (P0),
• carry out an iteration process comprising a first iteration step and a second iteration step based on a respective rough trajectory starting nodal point (Qj) and beginning at the rough trajectory starting nodal point (Q0), wherein:
• the first iteration step comprises ascertaining, based on the contour nodal points (Pj-Pn) having an index value (k) greater than or equal to an index value (j) of the respective rough trajectory starting nodal point (Qj), a contour nodal point (Pk) having a lowest possible index value (k), and a distance of the contour nodal point (Pk) from the rough trajectory starting nodal point (Qj) that satisfies a specified distance condition, and
• the second iteration step comprises ascertaining a respective following rough trajectory nodal point (Qj+1) which follows the respective rough trajectory starting nodal point (Qj) and lies on a first connecting line between the respective rough trajectory starting nodal point (Qj) and the contour nodal point (Pk) ascertained in the first iteration step, or lies on a second connecting line between the respective rough trajectory starting nodal point (Qj) and a centroid of a portion contour between the contour nodal point (Pj) and the contour nodal point (Pk), and the distance of the contour nodal point (Pk) from the rough trajectory starting nodal point (Qj) corresponds to a factor-weighted distance of the contour nodal point (Pk) ascertained in the first iteration step from the rough trajectory starting nodal point (Qj), wherein the factor is obtained from a quotient of trajectory length (sj) of the contour portion function (pj), where the index value (j) of the trajectory length (sj) of the contour portion function (pj) is equal to the index value (j) of the respective rough trajectory starting nodal point (Qj), and ascertaining a sum of trajectory lengths (sj-sk−1) of the contour portion functions (pj-pk−1) between a contour nodal point (Pj) of the contour nodal points (Pj-Pn) and the contour nodal point (Pk) ascertained in the first iteration step, where the index value (j) of the trajectory length (sj) of the contour portion function (pj) is equal to the index value (j) of the respective rough trajectory starting nodal point (Qj), and
• direct the movement of one of the at least two mutually redundant drive devices based on the ascertained rough trajectory nodal point (Qj+1).