Research On Charge Distribution Law Of Quartz Crystal Under Multi-dimensional Force

The multi-dimensional force/torque measurement technology has been widely used in the field of equipment manufacturing.As the most critical sensing link of the measurement and control system,the six-dimensional force sensor can provide feedback on all the information of three force components and three torque components.Piezoelectric force sensor,which is made of quartz crystal as force sensitive component,is widely used in the measurement of spatial multi-dimensional loads due to its advantages such as high sensitivity,high natural frequency,good stability and dynamic characteristics.With the development of industrial technology,new measuring requirements such as complicated load form,miniaturization of sensor structure and high efficiency of measurement performance have emerged,which has caused that higher requirements are placed on the structural dimensions and measurement performance of the six-dimensional force sensor.However,most of the existing piezoelectric six-dimensional force sensors can't realize integrated measurement of multi-dimensional complex loads because of complicated manufacturing processes and large sensor sizes.Therefore,it is of great scientific significance to explore novel piezoelectric six-dimensional force measurement theory and develop the piezoelectric six-dimensional force sensor with novel form of force-sensitive component structure.In this paper,the basic theories of multiple subject areas such as anisotropic elastic mechanics,crystal physics,dielectric physics,piezoelectric theory are used to carry out the research on principle and technology of six-dimensional force piezoelectric measurement based on cubic quartz crystal blocks.A novel piezoelectric multi-dimensional force measuring device is developed according to the distribution law of local area induced charge.The performance index is obtained by static calibration experiments,which can verify the theoretical derivation of the previous paper.The specific contents are as follows.The stress field distribution of cubic quartz ingots in a specific crystal coordinate system under the function of multi-dimensional force is analyzed by applying the basic theory of anisotropic elastic mechanics.And the analytical solution of the stress field is calculated by means of superposition.The stress field distribution of quartz crystal under the function of six-dimensional force is simulated by using Workbench software.The internal polarization electric field is calculated according to the basic theory of piezoelectric effect of quartz crystal and the law of tensor coordinate transformation.And the law of equivalent polarization plane charge distribution is obtained by solving the mapping relationship between the induced charge density and the six-dimensional force of each surface region.The surface area of the cubic quartz ingot is divided,and the mapping relationship between the six-dimensional force and the induced charge of the local area of the crystal block is obtained by solving the linear equations.A novel piezoelectric multi-dimensional force measuring device using two cubic quartz crystal blocks as force sensitive components is developed and fabricated by means of "partition area output charge".The calibration curves of each dimension force are obtained by static calibration experiments on the device.The static precision indexes such as nonlinear error,repeatability error and inter-directional interference are calculated,and measurement error is corrected and compensated.The specific accuracy index is that most of the nonlinear error and repeatability error are less than 3%,and most of the inter-directional interference error are less than 5%.Both theoretical derivation and calibration experiments have verified the feasibility of using cubic quartz crystal blocks as force sensitive components to achieve five-dimensional force measurement except torque.The results of the research in paper will further enrich the piezoelectric multi-dimensional force measurement theory and lay the foundation for the innovation of the design idea of piezoelectric multi-dimensional force sensors.