PROCESS MONITORING METHOD, COMPUTER PROGRAM, DATA PROCESSING DEVICE, COMPUTER-READABLE MEDIUM AND PROCESS MONITORING DEVICE

The invention relates to a method for process monitoring in a mechanical joining process, the method comprising receiving (S100) a plurality of measured values fi(xi) during the performance of the mechanical joining process, wherein the measured values each relate at least two process variables fi, xi, where i = 1... n, to one another. The method further comprises performing (S110) a Fourier transformation, wherein a number of Fourier coefficients (φ1, φ2,... φn, A1, A2,... An) are determined for the measured values fi(xi) and reducing (S120) the number of Fourier coefficients to an at least 2-dimensional subspace, thereby obtaining a measuring point (φk, φl,...), (φk, Al) or (Ak, Al) (214, 216). The method moreover comprises comparing (S130) the measuring point (φk, φl,...), (φk, Al) or (Ak, Al) (214, 216) with at least one reference point (Rk, Rl,...), (Rk, Sl,...) or (Sk, Sl,...) (219) in the at least 2-dimensional subspace and determining (S140) a monitoring outcome on the basis of the comparison with the reference point (219).