Design,Fabrication And Properties Of The Elastic Sensing Woven Webbing

Traditional textiles have gradually been given much richer functions in recent years for fulfilling diverse demands in people’s lives.Fabrics with sensing functions could convert structural changes into other forms of characterized signal,for example,there are many strain sensing fabrics with knitted structure,using for the studies related to human physiological signals or posture monitoring of small joint movements.In contrast,the movements of large body areas or joints such as the people’s shoulder,back,knees and elbows are usually subject to larger stress load,so when someone is doing rehabilitation orthopedic training with a small range of strains,the movement feature with large stresses and small strains is formed.However,the knitted fabric with coil structure is prone to cause large strains,so that strain sensing knitted fabrics are not suitable for motion monitoring in this case.Woven fabric could generate a small range of strains under relatively large stress with its more compact structure,but it is more difficult for common rigid woven fabrics to meet the required effective strains for sensing.At present,there is a lack of research focusing on sensing woven fabrics,especially their sensing performance and mechanism.Therefore,so as to meet the needs of the application scenario of large stress and small strain,in this study,a type of woven webbing with the conductive yarn was developed,it would have the required stretch strain through the addition of elastic yarns in warp direction for sensing effect,then sensing properties could be reflected by measuring the change of resistance with strain in certain length of the elastic woven webbing.This research investigated the methods of design,fabrication and sensing properties of the elastic sensing woven webbings,also explored and analyzed the application feasibility through corresponding human wearing test.The work includes the following aspects:In the preliminary design and preparation of the elastic sensing woven webbing,weft yarns contributed to the selvage formation of webbing in weaving process,and conductive yarns were used as wefts.Some main sensing characteristics and the influence of on-machine weft density,fineness of elastic yarn and woven structure on sensing properties were obtained after analyzing the structure,sensing mechanism and a series of measurements.The results show that conductive yarns as weft yarn inside the webbing do not contact with each other.The main reason for their sensing characteristics is the selvages on both sides which were formed by conductive yarns,when the webbing was strained by the warp stretch,both sides of selvages and the internal weft yarns would connect to form the equivalent parallel resistance,the resistance changed.The stress of elastic sensing woven webbing was relatively large in a small strain.The sensitivity was ideal,and the influence of fineness of elastic yarn and on-machine weft density on the sensing performance test results was more significant.However,the linearity could not be further discussed in this stage because the corresponding sensing curves had no distinctly linear characteristics.The use of conductive yarns in this type of elastic sensing woven webbing is wasteful for its not ideal sensing effect,what’s more,the sensing properties especially linearity need to be improved,therefore,the fabrication method need to be optimized.Based on preliminary exploration,this study further designed and improved the fabrication of the elastic sensing woven webbing by adding a selvage locking device in the weaving process.Conductive yarns here were separately woven as weft yarn and locking yarn these two ways in the webbing which had special locked type selvage on the right side.By changing the on-machine weft density,the fineness of the elastic yarn and the number of conductive yarns inside the locked selvage,9 webbing samples with conductive yarns as weft yarns and 27 webbing samples with conductive yarns as locked selvage yarns were formed.In the latter case,conductive yarns mainly formed the right locked selvage with a more complicated structure,so the equivalent resistance model of this structure was constructed.The corresponding equivalent resistance calculation formula obtained from that model would helpful to analyze the corresponding varying trend of each equivalent resistance unit under the strain.About the improved elastic sensing woven webbing with locked selvage,the measuring sensing curves and corresponding data was the basis for analyzing the sensitivity,linearity and reproducibility of different specification webbings.The results show that the sensing linearity of the latter samples woven with conductive yarn as the locked selvage yarns was more ideal.Comparing the results of the samples with different specifications,it was found that the changes in the specifications of the elastic yarns had distinct effects on both the basic resistance value and the sensitivity.Overall,the sensitivity of this type of webbing was generally high,the linearity was low,and the reproducibility was more stable,which was suitable for sensing applications.Finally,the improved elastic sensing woven webbing was applied to the test for monitoring the angle of human postural hunchback,the results also initially verified the stability of sensing data and application feasibility of the webbing.In summary,this study mainly explored the structural design,fabrication and sensing properties of different elastic sensing woven webbing by changing the weaving method of conductive yarns,and focused on the influence of on-machine weft density and fineness of elastic yarn on the sensing performance.The webbing with conductive yarn as the locked selvage yarn showed better results in various sensing properties,especially in improving the linearity.It achieved a generally low linearity,high sensitivity and stable reproducibility,and mainly relied on the special selvage structure of webbing to play a sensing role.The increase of the on-machine weft density and fineness of elastic yarn,or the increase of the number of elastic yarns within the locked selvage would make a higher sensitivity.In addition,the human wearing test further verified that the elastic sensing woven webbing with conductive yarn as the locked selvage yarn could meet the needs of human shoulder and neck motion monitoring,the sensing performance of this type of webbing were stable under large stress and small strain.The design and fabrication method of the elastic sensing woven webbing in this study is still waiting for further research for future application in this field.