Measurements and feature extraction in high-speed sewing

This paper presents the development of signal acquisition and analysis equipment for the measurement of sewing parameters on a high-speed overlock sewing machine. The objective of the work was to provide investigators of the textile area with hardware and software to ease the investigation on the dynamical behaviour of the following sewing parameters: force on needle bar; and presser-foot and thread tensions. It should also have enough flexibility to incorporate further signal entries, and provide the user with tools to ease the gathering and analysis of tests on different materials, sewing speeds and machine configurations and settings. Outputs for actuators to implement closed-loop control strategies are also available. The paper presents an overview of the system, which is a development of earlier hardware and software and focuses on the results concerning the measurement of the force on the needle-bar; this parameter is important to investigate needle penetration force in fabrics during sewing. Several signal-processing algorithms, that aim to automate the detection of some characteristics, are described. The purpose of this system, that implements some novel strategies, is to develop an add-on kit to apply to different sewing machines, but presently it has been implemented on a PC as a quality assessment system which will be used by textile technicians to build a quality database.