E-Knitted Textile with Polymer Optical Fibers for Friction and Pressure Monitoring in Socks.

The objective of this paper is to study the ability of polymer optical fiber (POF) to be inserted in a knitted fabric and to measure both pressure and friction when walking. Firstly, POF, marketed and in development, have been compared in terms of the required mechanical properties for the insertion of the fiber directly into a knitted fabric on an industrial scale, i.e. elongation, bending rigidity, and minimum bending radius before plastic deformation. Secondly, the chosen optical fiber was inserted inside several types of knitted fabric and was shown to be sensitive to friction and compression. The knitted structure with the highest sensitivity has been chosen for sock prototype manufacturing. Finally, a feasibility study with an instrumented sock showed that it is possible to detect the different phases of walking in terms of compression and friction.

The effect of body postures on the distribution of air gap thickness and contact area.

The heat and mass transfer in clothing is predominantly dependent on the thickness of air layer and the magnitude of contact area between the body and the garment. The air gap thickness and magnitude of the contact area can be affected by the posture of the human body. Therefore, in this study, the distribution of the air gap and the contact area were investigated for different body postures of a flexible manikin. In addition, the effect of the garment fit (regular and loose) and style (t-shirts, sweatpants, jacket and trousers) were analysed for the interaction between the body postures and the garment properties. A flexible manikin was scanned using a three-dimensional (3D) body scanning technique, and the scans were post-processed in dedicated software. The body posture had a strong effect on the air gap thickness and the contact area for regions where the garment had a certain distance from the body. Furthermore, a mathematical model was proposed to estimate the possible heat transfer coefficient for the observed air layers and their change with posture. The outcome of this study can be used to improve the design of the protective and functional garments and predict their effect on the human body.

Contribution of garment fit and style to thermal comfort at the lower body.

The heat and mass transfer between the human body and the environment is not only affected by the properties of the fabric, but also by the size of the air gap thickness and the magnitude of the contact area between the body and garment. In this clothing-human-environment system, there is also an interaction between the clothing and the physiological response of the wearer. Therefore, the aim of this study was to evaluate the distribution of the air gap thickness and the contact area for the male lower body in relation to the garment fit and style using a three-dimensional (3D) body scanning method with a manikin. Moreover, their relation with the physiological response of the lower body was analysed using the physiological modelling. The presented study showed that the change in the air gap thickness and the contact area due to garment fit was greater for legs than the pelvis area due to regional differences of the body. Furthermore, the garment style did not have any effect on the core temperature or total water loss of the lower body, whereas the effect of garment fit on the core temperature and total water loss of lower body was observed only for 40 °C of ambient temperature. The skin temperatures were higher for especially loose garments at thigh than the tight garments. Consequently, the results of this study indicated that the comfort level of the human body for a given purpose can be adjusted by selection of fabric type and the design of ease allowances in the garment depending on the body region.

Effect of heterogenous and homogenous air gaps on dry heat loss through the garment.

In real life conditions, the trapped air between the human body and the garment has uneven shape and vary over the body parts as a consequence of the complex geometry of the human body. However, the existing clothing models assume uniform air layer between the human body and the garment or its full contact, which may cause large error in the output of simulations. Therefore, the aim of this study was to investigate the effect of a heterogeneous vertical air gap with different configuration of folds (size and frequency) on dry heat loss using a heated cylinder (Torso). It was found that the presence of folds in the garment led to an increased heat loss from the body in comparison to a homogeneous air gap of comparable size. Interestingly, the size of folds did not have an influence on the dry heat loss. Additionally, the effect of the contact area on dry heat loss became important when exceeding a threshold of about 42%. The results from this study are useful for modelling of a realistic dry heat loss through the clothing and contribute to the improvement of design of protective and active sport garments.

Physical and Perceptual Independence of Ultrasonic Vibration and Electrovibration for Friction Modulation.

Two different principles are available to modulate the user perceived roughness of a surface: electrovibration and ultrasonic vibration of a plate. The former enhances the perceived friction coefficient and the latter reduces it. This paper will highlight the independence of the two effects on the physical and perceptual point of view to confirm the increased range of sensation and stimulation that can be supplied by the two coupled techniques to the users. Firstly, a tribometric analysis of the induced lateral force on the finger by the two coupled effects will be presented, then a study on the dynamic of the two effects will be reported. In the end, a psychophysical experiment on the perception of the two coupled techniques will be shown.

Influence of physico-chemical, mechanical and morphological fingerpad properties on the frictional distinction of sticky/slippery surfaces.

This study investigates how the fingerpad hydrolipid film, shape, roughness and rigidity influence the friction when it rubs surfaces situated in the slippery psychophysical dimension. The studied counterparts comprised two 'real' (physical) surfaces and two 'virtual' surfaces. The latter were simulated with a tactile stimulator named STIMTAC. Thirteen women and 13 men rubbed their right forefingers against the different surfaces as their arms were displaced by a DC motor providing constant velocity and sliding distance. Tangential and normal forces were measured with a specific tribometer. The fingerpad hydrolipid film was characterized by Fourier transform infrared spectroscopy. The shape and roughness of fingers were extrapolated from replicas. Indentation measurements were carried out to determine fingerpad effective elastic modulus. A clear difference was observed between women and men in terms of friction behaviour. The concept of tactile frictional contrast (TFC) which was introduced quantifies an individual's propensity to distinguish two surfaces frictionally. The lipids/water ratio and water amount on the finger skin significantly influenced the TFC. A correlation was observed between the TFC and fingerpad roughness, i.e. the height of the fingerpad ridges. This is essentially owing to gender differences. A significant difference between men's and women's finger topography was also noted, because our results suggested that men have rougher fingers than women. The friction measurements did not correlate with the fingerpad curvature nor with the epidermal ridges' spatial period.

Robust control strategies for an electric motor driven accumulator with elastic webs.

This paper concerns the modelling of an accumulator used in industrial elastic web processing plant to allow changing material roll while the rest of the line remains at a constant web velocity. A nonlinear model of a motor actuated accumulator is first summarized. This model is derived from the physical relationships describing web tension and velocity dynamics in each web span of this accumulator. A linear model is deduced from the nonlinear one around a working point for frequency domain analysis. Thus the effect of some mechanical accumulator parameter variations are analyzed. In a second part, multi-model industrial PI controllers, adjusted with evolutionary algorithm on our realistic nonlinear model are compared with multi-model H∞ controllers. Both controllers allow good robustness against mechanical parameter variations.