Patent ID: 6178389
Filing Date: 2001-01-23
Classification: G01B

Abstract:
A method of determining the measuring uncertainty of a coordinate measuring machine, said machine comprising a tracer (7) for sampling the surface of a part (2) for measurement, to determine locations of points on the surface of the part (2) and to permit the measurement of geometric quantities (G.sub.1, . . . , G.sub.r) related to the coordinates of said points (P1, . . . , Pk); characterized by comprising the steps of:measuring (110), by means of said tracer (7), the coordinates of a predetermined number of points (P1, . . . , Pk) on the surface of said part (2) to obtain a set of measured coordinates (x.sub.P1, y.sub.P1, z.sub.P1 ; . . . ; x.sub.Pk, y.sub.Pk, z.sub.Pk);calculating (140), on the basis of said measured coordinates (x.sub.P1, y.sub.P1, z.sub.P1 ; . . . ; x.sub.Pk, y.sub.Pk, z.sub.Pk), a set of reference values (Ref) for said geometric quantities (G.sub.1, . . . , G.sub.r);generating (150) a perturbed-coordinate matrix (V.sub.c) comprising a predetermined number (N) of rows, each of said rows being defined by a set of perturbed coordinates (V.sub.ci), and said perturbed coordinates having values statistically close to those of said measured coordinates;and by also comprising the performance of simulated measuring cycles (170-210), each of which comprises the steps of:calculating (180), for each set of perturbed coordinates (V.sub.ci), a set of simulated values (Res.sub.i) for said geometric quantities (G.sub.1, . . . , G.sub.r);calculating (190) the difference between said reference values (Ref) and said simulated values (Res.sub.i) to obtain a set of deviation values (S.sub.i);and by also comprising the final step (220) of performing a statistical analysis of said sets of deviation values (S.sub.i) to determine said measuring uncertainty.