| Under the action of high speed and complex airflow,how to accurately measure the dynamic aerodynamic loads on the all-movable rudder wind tunnel model is directly related to the aircraft's contour design,weight distribution,internal reinforcement structure design and other fields.This requires the wind tunnel balance with high stiffness,large range,high measurement accuracy and good dynamic characteristics.At present,the more mature strain balances have the disadvantages of low stiffness and poor dynamic characteristics.The deformation of the balance is mixed with the deformation of the rudder surface,which will seriously affect the measurement of the load on the all-movable rudder.In addition,the dynamic characteristics of the strain balance restrict its application in the dynamic real-time measurement.In addition,the dynamic characteristics of the strain balance restrict its application in dynamic real-time measurement applications.Therefore,the use of piezoelectric quartz with high stiffness and high sensitivity as a balance for force sensors is more suitable,which is very important for the accurate measurement of aerodynamic load of the rudder surface and the design of the aircraft.In this paper,a large-scale four-point layout piezoelectric balance is developed for the design requirements of large-load,narrow installation space for wind tunnel balances.The piezoelectric balance is mainly composed of key components,such as cover plates,three-way force sensors,preloaded screws and bases.The precision of the balance measurement is improved from the design,processing and assembly of the parts,and structure checking,static calibration and modal analysis are carried out by finite element analysis.The decoupling algorithm for the coupling between the two dimensions is deduced and applied to the data processing of the static calibration experiment of the balance.The calibration matrix C and static performance indicators such as linearity error,repeatability error,and interference coefficient are obtained,and dynamic excitation experiment is used to test the dynamic response ability and measurement precision of balance.The natural frequency and frequency response curve of the balance are obtained through the impulse excitation experiment.The source of the measurement error of the piezoelectric balance is briefly analyzed,and the influence of the calibration force/torque on the equivalent point of the sensor contact surface is emphatically analyzed.By using the finite element method,the offset law of the equivalent point of the contact surface of the balance sensor under the action of the unidirectional force / torque is simulated,and the offset of the sensor spacing is compensated and the compensation mechanism is applied to the multi direction loading.The median value filtering method is applied to deal with the noise signal in the test,and is applied to the commissioning test and wind tunnel test.The experimental results show that the nonlinearity error of the balance does not exceed 1.6%,the repeatability error is around 1%,the maximum interference coefficient is 1.625%,the minimum natural frequency is in the Y direction,and the value is 558.17 Hz.It has high measurement accuracy,good signal followability and dynamic performance.It meets the aerodynamic load measurement requirements of the all-movable rudder wind tunnel model.Based on the study of the offset law of the equivalent point of the contact surface of the sensor and the method of sensor distance compensation,the measurement accuracy of the balance is effectively improved.Therefore,the research on the piezoelectric balance technology and the error compensation method for the aerodynamic load measurement of the all-movable rudder wind tunnel model is of guiding significance to the improvement of the structure design and the static calibration method of the parallel piezoelectric multidimensional force sensor. |
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