Research Of Doubly-clamped Beam Yarn Tension Sensor Based On Surface Acoustic Wave

Textile intelligent manufacturing is one of the critical programs of China's 13th Five-Year Plan for the textile industry.Yarn tension sensor,as a vital device for obtaining information on textile technology,plays a decisive role in improving the performance and parameters of textile equipment.In the process of yarn,fabric and synthetic fiber processing,the tension is a critical production parameter that cannot be avoided in the means of winding,twisting,and knitting.Accurate and stable obtaining of tension parameters of textile products is one of the important goals of intelligent textile manufacturing.In this dissertation,we study a new type of yarn tension sensor with high resolution and strong stability,and propose a doubly-clamped beam yarn tension sensor based on the surface acoustic wave.This dissertation focuses on the theory of surface acoustic wave,device design and signal detection method of yarn tension sensor.The main research content and innovation points are as follows:1)A method of yarn tension sensor with doubly-clamped beam designed by surface acoustic wave device is presented.The functional relationship between the output frequency of the sensor and the yarn tension is deduced.When the yarn tension is applied to the sensor's doubly-clamped beam(i.e.,the piezoelectric substrate with double-ended clamped supports),the tension is proportional to the change of the output frequency of the sensor,so as to measure the yarn tension.2)We solved three key problems of yarn tension sensor based on surface acoustic wave.Firstly,solve the problem of choosing piezoelectric substrate material.Among the five commonly used surface acoustic wave piezoelectric materials(LiTaO3,LiNbO3,LGS,LBO,and SiO2),using the Quartz material as the piezoelectric substrate,the strain of the piezoelectric substrate could be maximized.Secondly,solve the problem of choosing piezoelectric die size.In the condition of 22 mm?L?30mm and 6mm?W?10mm,choosing the length L=30 mm and the width W=6mm,the stress of the doubly-clamped beam(i.e.,the piezoelectric substrate with double-ended clamped supports)would reach its maximum.Thirdly,solve the problem of the placing of inter-digital transducers.When inter-digital transducers are placed in the maximum strain region of the piezoelectric substrate,the sensitivity of the sensor can be significantly improved.3)Four methods were used to reduce the second-order effect of surface acoustic wave devices in yarn tension sensors.Firstly,we select the piezoelectric material with small electromechanical coupling coefficient to minimize the regenerated wave.Secondly,we design the IDT of an unbalanced split-finger structure to reduce the problem of electrode reflection.Thirdly,we paint sound absorbing material at the ends of the substrate to minimize the edge reflection of the transducer.Fourthly,we cut the back grooves of the piezoelectric substrate to reduce the bulk acoustic wave of the surface acoustic wave device.In addition,in order to reduce the sideplobe level of the surface acoustic wave device,the hamming function is used to weight the input inter-digital transducer.4)We designed the peripheral circuit of yarn tension sensor.The peripheral circuit includes a surface acoustic wave oscillator,mixer and low pass filter.The purpose of converting yarn tension into frequency signal is realized by designing and debugging these circuits.5)We produced the high precision doubly-clamped beam yarn tension sensor based on the surface acoustic wave,and its essential performance and parameters are measured.Test results:sensor sensitivity is 12699 Hz/N,sensor range is 0-2 N,linearity is 0.4218%,hysteresis is 0.5232%,repeatability is 1.2183%,accuracy is 1.3914%,zero temperature coefficient is 4.21 x 10-4 Hz/?,maximum overload capacity is 200%(4N),the fracture strength of the substrate is 5 N.