| Knitted materials have obvious advantages in terms of lightweight,extensibility,breathability,comfort,and structural stability,and can perfectly fit the human body for accurate collection of signs and signals.It has become one of the important directions in the development of flexible wearable smart devices.This topic takes the warp-knitted structure with excellent mechanical properties as the research object.By selecting silver-plated nylon yarns with good weaving properties,warp-knitted elastic conductive sensing fabrics with different structural parameters are prepared together with nylon and spandex,and the electrical properties of the samples in the process of one-way stretching,two-way stretching and three-dimensional top pressure are tested and analyzed in depth.Explain the mechanism of the influence of loop structure and process parameters on its sensing performance,and then optimize the design plan to prepare sensing equipment that can dynamically monitor limb movement data.The specific research content mainly includes four parts.(1)Firstly,the process design and preparation method of warp-knitted strain-sensing fabric is studied.Considering the important effect of silver coating on the resistance value of conductive yarn,the influence of friction force on the surface of warping and weaving process is analyzed,and the good braided performance of yarn is verified.Based on the basic parameters of warp knitting structure,17 kinds of samples for testing and analyzing the electrical and sensing characteristics of fabric are prepared by changing the yarn density of silver-plated nylon yarn,the structure of conductive yarn and the size of sensing area.(2)The correlation mechanism between loop structure parameters and electrical properties of the sensing fabric is studied under unidirectional tensile stress,and the working principle of the warp-knitted strain-sensing fabric is analyzed.Through the test,the correlation between the electrical resistance change rate of the conductive fabric and the maximum strain,tensile speed and tensile direction of the tensile test,as well as the linear density of the silver-plated nylon yarn,the tissue structure,the elastic spandex content,the fabric pulling density,the opening and closing of the loop,the conductive yarn pad yarn sequence and the number of loops in the sensing area is analyzed.The sensitivity,linearity,hysteresis and repeatability are evaluated.(3)To further explore the sensing performance of the warp-knitted strain-sensing fabric under the complex deformation of X-Y bidirectional stretching and three-dimensional surface,test the relationship between the resistance change rate and time of the warp-knitted strain-sensing fabric with different loop structure parameters under bidirectional stretching,as well as the influence of different top pressing speed and depth on the deformation electrical properties of the warp-knitted strain-sensing fabric under three-dimensional top pressing condition.The rate-time curve of resistance change of warp knitted strain sensing fabric under unidirectional stretching,bidirectional stretching and three-dimensional curved strain is synthetically compared to explore the influence of strain generation mode on the sensitivity of fabric sensing.(4)Based on the conclusion of the above experimental study,the fabric design scheme is optimized,and 9 different parameters of open cord lap,open satin lap and open atlas stitch are prepared.The samples are tested by comprehensive unidirectional,bidirectional and three-dimensional curved strain test.Finally,the wearable elastic product is made by selecting the warp-knitted strain sensing fabric with the fabric structure of the conductive yarn as open atlas stitch and the threading mode as 1 interval,which is used for monitoring the motion of the upper limb.The slow,medium and fast motion data of the upper limb swing amplitude of 90° and145° are effectively monitored..The research comprehensively analyzes the important influence of loop structure parameters on the sensing performance of warp-knitted strain-elastic sensing fabrics,establishes the relationship between structural parameters and fabric deformation,electrical properties and strain sensing properties,realizes the dynamic monitoring of limb movement status,and provides theoretical basis and technical support for the design of efficient and accurate smart wearable products. |
