Research On Multi-dimensional Force Sensor Based On Quartz Crystal

With the development and progress of industrial technology,the multi-dimensional force measurement technology has been widely used in the field of engineering testing.After decades of research and exploration by scholars,a series of force measurement techniques have been developed.The test method that uses piezoelectric crystal as the force-sensitive source has high sensitivity and superior dynamic performance,which is widely used in multi-dimensional force measurement in the engineering field.At the same time as science and technology advances,piezoelectric sensors still measure force by inducing charges from the entire surface of the piezoelectric sheet.The use of the piezoelectric effect still stays on the linear relationship between the force and the charge of the entire surface.There is a lack of research and exploration work on the charge distribution in the local area of the piezoelectric body.As a result,the measurement of multi-dimensional force(above three dimensions)must rely on the way of multi-point arrangement of force measurement units.So there is a lack of major innovation in the measurement principle.Further research and analysis of the force-induced charge in each local area of the quartz crystal has great significance to the development of new measurement methods.This paper will put aside the inherent concept of using the linear relationship between force and charge on the entire surface to make piezoelectric sensors.The cube quartz block will be the research object.Then solve the stress and induced charge distribution formula on the quartz block under the action of multi-dimensional force.According to the form of charge distribution,divide the area to measure the different forces or moments.Finally,a force measurement device using a single cubic quartz block is designed based on this method.The specific contents are as follows.After comparing and analyzing different piezoelectric materials,quartz is finally selected as the research object of this article.Combining the material properties of quartz with the theory of anisotropic elasticity,the theoretical analytical formula of the internal stress field of quartz placed in different directions under the six-dimensional force is obtained by deriving and solving step by step.Then complete stress simulation analysis of quartz with the finite element software.The formula for the charge density distribution of the quartz crystal block is derived based on the piezoelectric theory of quartz.According to the method of solving the induced charge quantity,the integral equation of the charge quantity in a specific area is obtained.Subsequently,the charge simulation analysis is performed on the quartz block to verify the correctness of the induced charge distribution formula.Finally,the surface of the crystal block placed in different directions is divided and the solution formula for measuring the multi-dimensional force when the crystal block is placed in each direction is obtained.Based on the above analysis theory,a multi-dimensional force measuring device using a single quartz block is designed and the first-order frequency is 1165.16 Hz.The cross-sectional size of the device is about 50*50mm,and the size of the similar four-point torque measuring equipment is about 200*200mm.This method effectively reduces the structural size of similar equipment.The calibration experiment of the torque direction has been completed.The experiment shows that the linear error of the measured torque is within 3% and the repeatability error is within 5%.The corresponding relationship between the input and output of the experiment is the same as the theoretical calculation.It is found by comparison that the relative error between the calibration result and the calculated result is 6% to 13%.Finally,the interference of the pressure on the measuring device through experiments is evaluated and propose a theoretical correction method that can remove interference.In this paper,this research preliminarily confirmed the feasibility of using a single cubic quartz crystal block to measure the six-dimensional force which provides new ideas for the further innovation of piezoelectric force measurement methods.