Computer Aided Measuring of Textile-Mechanical Parameters

A new equipment for measuring the draping characteristics of static cloth is presented in the paper. In contrast with Kawabata Evaluation System 3D geometrical data of the sample are captured from photo images. Based on a mathematical reconstruction of geometry, and drape coefficients and mechanical parameters are evaluated upon the geometrical model. The computer controlled equipment moves a round table positioned in the centre providing the natural pleating of fabric for the measuring. The core part of the equipment is a computer moved frame. The sample is scanned by laser-beams. Lasers light the cross section curves of the sample on different levels. There are four cameras on the frame taking the pictures of cross section curves in different levels. 3D geometry is reconstructed upon the pictures. A mass, spring and damping element system is the basis of the cloth simulator. Springs are assumed to be linear, while damps are proportional to the velocity. The physics engine running the simulator calculates vertex positions at a time based on interaction forces with neighbouring vertices, including stretch, bend and shear forces. Collision of the cloth model with the model of the underlying object is performed and handled in each time step. To evaluate the influence of the individual parameters, a series of simulations was performed. For the real cloth samples, a range of cross-section curves is captured, digitalized and interpolated by Fourier series. The same Fourier coefficients are determined for the cloth model as a function of simulation parameters. The actual simulation parameters are defined by the minimum of the difference between the modelled and the measured geometry.