Research On SAW Sensors For Monitoring Pressure In Micro-gaps

In engineering applications and mechanics,detection of contact stress is still one of the hot topics researched.Especially,it is necessary and also important to detect contact pressure on the surface of the object in micro-gaps which is between two objects and elastic medium.In this paper,analysis and research of monitoring pressure in micro-gaps are carried out in view of the problem.Up to now,there are different kinds of sensors used to measure contact pressure.They have their own advantages and disadvantages.However,most of them need the power to work,and their working mode is wired.This working mode in the environment of micro-gaps is not suitable to measure contact pressure,and the power and antennas increase the difficulty of system to integrate and monitor contact stress.In view of the shortcomings of the traditional testing methods,SAW technology is adopted in this paper,which can realize the passive wireless operation mode.SAW based on a micro sensor is one kind of contact sensors.Considering micro-gaps,sensors designed can give full play to their own advantages.SAW sensors designed in the paper are different from the structure of traditional sensors,and their double-layer hollow structure has the advantages of function.Using machining technology,SAW sensors can be made smaller,can be convenient integration,and the cost is low.Based on the SAW sensing technology,the scheme of measuring contact pressure in micro-gaps is proposed.Combined with the characteristics of SAW technology,the core components of the monitoring system are studied,analyzed and designed.Through theoretical analysis,software simulation and test verification,related knowledge is systematically studied.First of all,around the environment of measuring contact pressure in micro-gaps,structures and working principle of SAW pressure sensors are mainly researched.In order to solve the problem of monitoring stress in micro-gaps,an appropriate scheme of monitoring pressure is proposed.SAW based on a micro force sensor pressure is designed to monitoring pressure,and a new type of delayed SAW sensors based on lithium niobate piezoelectric material is designed.Secondly,according to models of SAW sensors,SAW sensors with delay line which use lithium niobate material and adopt double layer structure are analyzed including It includes force form,selection of the material,finite element analysis of the piezoelectric substrate,and design of the interdigital transducer.What's more,design of the interdigital transducer is emphatically analyzed.Fabrication of SAW sensors with delay line which use lithium niobate material is studied,including substrate pretreatment,dicing,welding and so on.Finally,SAW sensors are tested and data are analyzed.Then the least square method and the matrix method are used to analyze,two ways are compared with each other.According to results,the conversion relationship between the frequency and pressure of SAW based on a micro force sensor is summarized.