Carpet manufacturers certify their products for end-use applications by evaluating the wear behavior of their carpets in mechanical experiments. Currently, this process is performed by visual inspection, suffering from subjective gathers that limit reliability. To automate this process, we propose the use of image processing techniques, specifically of local binary pattern (LBP) statistics. Such statistics are tolerant against illumination changes, can be easily implemented, and perform well when combined with a symmetrized adaptation of the Kullback—Leibler divergence. As a main innovation, we extend the existing rotationally invariant LBPs by including ‘mirror’ and ‘complement’ invariants. We show an accurately improved and more reliable estimation of the degree of wear in worn carpets. The evaluation is performed on four digital reference scales, each containing eight pairs of images comparing transitional degrees of wear to the original appearance. Additionally, the texture changes due to distortions of the pile yarn tufts are enhanced by choosing a suitable scale factor per reference. We validate the findings using six physical reference scales, each containing four pairs of images. In both references, linear correlations of over 0.89 are demonstrated between the degrees of wear and extracted features from the images. These findings justify the use of the proposed LBP extensions in a first approach towards an automated low-cost inspection system for carpet wear at low computation cost.
This paper deals with the three-dimensional computer simulation of the weft insertion process as a possible solution to avoid costly weaving trials when researching this process. A three-dimensional mathematical model of the yarn was developed, in which the behavior of the yarn was described by the Second Law of Newton. For this mathematical model, a second order differential equation needed to be solved. To this end, an explicit integration using Euler’s method was chosen. In order to validate the model, high-speed camera recordings were performed on a test stand and compared with simulations of the same test stand. A very good resemblance was found between simulation and camera recordings. This is the first time that a three-dimensional model for the weft insertion on air-jet looms has been successfully tested.
The main nozzle of an air jet loom plays an essential role in the weft insertion process. This role involves sucking the weft yarn from the prewinder and launching it into the reed. Simulating the dynamic behavior of the weft yarn inside the main nozzle involves fluid–structure interaction (FSI). In this work, one-way and two-way FSI simulations of air flow–yarn interaction inside a main nozzle have been performed. A three-dimensional model of the flexible weft yarn, consisting of a chain of line segments, and a two-dimensional axisymmetric model of the supersonic flow have been developed and coupled to perform these simulations. The results of the simulations are compared quantitatively and qualitatively with experimental results. Good agreement has been found between the results of the two-way FSI simulations and the experiment. The coupled fluid and structure models provide an effective numerical tool to optimize the geometry of the main nozzle based on the calculated motion and speed of the weft yarn.
In this paper we present a novel 3D scanner to capture the texture characteristics of worn carpets into images of the depth. We first compare our proposed scanner to a Metris scanner previously attempted for this application. Then, we scan the surface of samples from the standard EN1471 using our proposed scanner. We found that our proposed scanner offers additional benefits because it has been specifically designed for carpets, performing faster, cheaper, better and also a lot more suitable for darker carpets. The results of this approach give optimistic expectations in the automation of the label assessment dealing with multiple types of carpets.
This paper deals with the computer simulation of the weft insertion process as a possible solution to avoid costly weaving trials when researching this process. A one-dimensional mathematical model of the yarn was developed, in which the behavior of the yarn is described by Newton's Second Law. For this mathematical model, a second-order differential equation needs to be solved. For this purpose, an explicit integration using Euler's method was chosen. In order to compare the results, a simulation was made, which could also be analyzed theoretically. The results were compared with the theory as well as with the results obtained by using several other integration methods.In the weft insertion process on an airjet loom, the weft yarn is withdrawn from the weft accumulator and accelerated by the main nozzle into the shed, where it is carried forward by a number of relay nozzles arranged in several groups. These groups are activated sequentially as the yarn is moving forward. Once the yarn reaches full insertion, the stopper pin on the weft accumulator closes. As a consequence, the yarn is stopped from a high speed, which generates a high tension and causes the yarn to jump back. If the tension due to the stopping of the yarn gets too high, weft breakage and thus machine stops can occur. In order to avoid this, a brake can slow down the yarn before the actual stopper pin closes. If the yarn jumps back too much, fabric errors can occur. In order to avoid this, the yarn is usually stretched by the relay nozzles and other devices at the end of the insertion. In order to study the problems which can occur near the end of the weft insertion without performing costly weaving trials, a computer model was developed simulating this process. Mathematical ModelThe mathematical model is based upon the finite volume method. In this method, the yarn is divided into a number of elements and the Newton's Second Law is applied to each element. Therefore, a differential equation of the second order needs to be solved, and this is done by integrating twice using Euler's method [6]. In order to increase the simplicity and to decrease the number of factors that 1 To whom correspondence should be addressed: tel.: +32 9 2645418, fax: +32 9 2645831; e-mail: Simon.Demeulemeester@Ugent.be influence the yarn, a one-dimensional model was used. In this model, the yarn is aligned along one axis, which we designate as the X-axis. This implies that the yarn has no thickness and there is no bending involved because only one dimension is considered. Finite VolumesIn the finite volume method [8] the simulated object is divided into a certain number of 'finite volumes.' The laws of nature are then applied to each finite volume, whereby the properties of one finite volume are assumed to be constant. In this case, the yarn is divided into N contiguous cylindrical finite volumes (segments) along the yarn length. The mass of each finite volume is assumed to be concentrated at a single point at the centre of the cylinder. Each mass point is of a constant ma...
Pneumatic splice chambers are the industry method for splicing yarns. Most investigations in the literature occurred with ends-opposed splice chambers. For several applications, ends-together splicing is industrially interesting to consider. In this paper, we determine the importance of some process and splice chamber design parameters for ends-together splice chambers. We find that splicing pressure can be maximized, splicing duration needs to exceed a minimum duration and optimum splice length depends on yarn type and chamber design. Important splice chamber design parameters are chamber size and both yarn inlet and air inlet size relative to chamber size. This study also demonstrates the usefulness of three-dimensional printing to evaluate new splice chamber designs.Splicing yarns is an important part of automatic winders in textile machinery. More recently, the warp yarn creels can be removed by using automatic splicers. This opens up the perspective for changing the warp yarn type during weaving. This calls for an automatic splicer that can splice a wide range of yarns.The principle of pneumatic splicers is simple. Two yarns ends are put parallel to each other in a small chamber on top of an air inlet. A cover is placed over the chamber, after which an air jet is introduced at high speed through the bottom air inlet. The jet is highly turbulent. Due to the air-yarn interaction in this turbulent flow, the yarn ends first open and then join together in a splice.Several pneumatic splicers are available. When comparing splice performance between splicers, the following properties are used in the literature: RSS or Retained Splice Strength, which is the strength of a splice divided by the strength of the original yarn; RSE or Retained Splice Elongation, which is the elongation at break of a splice divided by elongation at break of the original yarn; RSD or Retained Splice Diameter, which is the diameter of the splice divided by the diameter of the original yarn; and RYA or Retained Yarn Appearance, which is a qualitative/subjective parameter of the appearance of the splice compared to the original yarn.Most existing research is for ends-opposed splice chambers in which the two yarns enter the splice chamber from opposing sides, while ends-together splicing is rare. The different splicing options are illustrated in Figure 1. First we will present the results of a literature review regarding the influence of machine parameters on the splice properties. Wet splicing, whereby a fine mist is added into the air flow, results in a larger RSS. 1 The splice nozzle type (air inlet) influences the RSS as well. 2 For the air pressure used to splice, it is found 3-5 that a minimum pressure is required for a successful splice, a further increase in pressure rapidly increases RSS until a maximum RSS is reached and usually Ghent University, Belgium
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