Study Of Three Components Piezoelectric Balance For Large-scale Model Wind Tunnel Experiment

The rapid development of the aerospace,national defense and scientific research,higher requirements have been placed on the force balance about response speed and natural frequency.In this paper,a new type of three-component piezoelectric balance is developed to meet the demands of dynamic force measurement in wind tunnel tests of a large-scale model.The piezoelectric balance is characterized by large measurement range,high measurement accuracy,high natural frequency,good stability,and so on,which ensure reliability of measurement data and testing accuracy of the wind tunnel.Firstly,based on the positive piezoelectric effect and the piezoelectric mechanism of piezoelectric quartz crystal,the expression formula between the output charge of quartz and its acting stress is deduced,and the piezoelectric coefficient matrix showing the piezoelectric effect is obtained.The piezoelectric coefficient matrix is used as the theory to design force sensor.Based on the force sensor,the diamond and square space layout and measurement principle of the four-support point sensor are introduced.Combined with the research contents and requirements of the subject,the key technical problems and difficulties that need to be solved are put forward,which provide direction in measurement plan selection and structural design of follow-up piezoelectric balance.Secondly,according to the size and load capacity requirements of the balance,the traditional four-point support diamond layout structure and square layout structure are extended,and a four-point support rectangular layout structure and an eight-support double rectangle layout structure are designed.According to the Static and Modal analysis of ANSYS Workbench,analysis and comparison of balance stiffness and natural frequency are made to determine the final measurement plan of the balance.The size of the quartz wafer used in the sensor is calculated,and the problems of inter-directional interference and the change rule under different action points during the use of the balance are studied.Finally,according to the structure of the balance and the calibration range,the two-way piston type of hydraulic pressure generator was selected as the force-applying device.The three-dimensional calibration loading model of the balance was established and analyze the calibration process.Using the calibration loading device to calibrate static calibration system,obtain the accuracy indexes of the balance that include nonlinearity,repeatability,and inter-directional interference.The decoupling-compensated balance indicators were all within 2%,which meet the requirements of the three-dimensional aerodynamic measurement.Aiming at the dynamic characteristics of the balance,a dynamic excitation experiment was designed.Experiments show that the balance has good dynamic characteristics and high natural frequency,which meets the dynamic testing requirements of the wind tunnel.