Pulse frequency calculation and estimation in yarn evenness analysis

The present paper describes work carried out, within a project to the textile industry, to achieve supervision and characterization of spun yarn. One of the main goals was to establish a methodology to easily determinate the roller draft that causes irregularities. Two different approaches to achieve decomposition of a binary signal in digital signals with known pulse frequencies are presented. The first approach, already used and tested in the laboratory, is based on two different methods: the first method uses an accelerated algorithm based either on the Fourier or Walsh transforms, while the second one presents a new methodology, DFI (impulse frequency determination), for signals where long periods with very short duty cycle are expected. The use of one of these methods instead of the other depends on the characteristics of the signals under analysis and on the pursued objectives. A new methodology to decrease memory amount and increase the speed of the DFI calculation is presented and discussed. Several techniques are compared. A new approach using logical analysis of the thresholded signal of the yarn mass, to establish the probability of a pulse frequency to be one of the signal components, is under study at our lab