Study On Vector Force Measurement Technique With Variable Force Ratio

Thrust vector control engine(TVCE)enables aircraft capabilities of short takeoff and landing,and post-stall maneuver,which is a key equipment of movement control.It is of great significance to improve the design of TVCE to carry out measurement research of vector force with high precision and robustness.Thrust amplitude of TVCE is large,nozzle angle adjustment range is wide,and temperature gradient field is high around the nozzle,which brings a great challenge to the design of the force test device for TVCE.In this paper,taking piezoelectric vector force test with a reduced scale of 5000N as the object,the research is carried out in such aspects as establishment of mathematical model of high-precision vector force measurement,design of high-stiffness test device,decoupling of vector force nonlinear interference and evaluation of force test error under heat.The mathematical model of vector force measurement is established with piezoelectric force sensor multi-point arrangement method.For problem that the theoretical output is difficult to solve problem caused by the sensors' indeterminate layout in force calibration.according to the Kirchhoff plate deformation theory and layout of multiple sensors,test device working plane of displacement deformation differential equation is established with four-square layout under offset load force,the differential equation is solved with finite difference method,each sensor's output law and sensitivity under eccentric load position are obtained,and the sensitivities are optimized with sequential quadratic programming(SQP)algorithm to reduce the resultant error of multiple loading points.The multi-point calibration method of test device based on Kirchhoff plate deformation is proposed,which improves the mathematical model of piezoelectric force measurement and the measuring accuracy of dynamometer.In order to solve the problem of low frequency response and insufficient dynamic performance caused by large mass of test device,with Lagrange dynamics method,based on the six degrees of freedom motion and elastic deformation of each force transmitting component,dynamic model of test device is established and the natural frequency of the test system is solved.The natural frequency of the test device is obtained by experimental modal analysis,which verifies accuracy of the theoretical model.The influence of stiffness of key components on the natural frequency of the test system is analyzed.In order to improve stiffness of the key components,the design stiffness interval of the key components with the constraint of natural frequency is obtained with the method of Gaussian fitting,and the parallel support device is developed.The first-order natural frequency of test device increases from 248Hz to 463Hz,which improves dynamic performance of the test device.For the nonlinear disturbance existing in each component of vector force measurement,vector force calibration method of the device is investigated.In order to improve the generalization of the test data,a multi-layer DBN network based on force direction and force ratio is built and a variable force ratio vector force calibration method based on DBN test system is proposed,which can solve variable force ratio vector force nonlinear compensation problem and improve force test precision.Aiming at the problem of evaluating measurement accuracy of vector force under large temperature gradient,the influence law of thermal field on dynamometer is researched,and the uncertainty analysis of force measurement system is carried out.Combined with factors of heat source and sensor location,testing time,thermal force error analysis model of dynamometer is established,the influence law of temperature factors on measurement is revealed,and uncertainty of measurement is obtained with factors of heat,electricity and force?,which improves the measurement precision under heat and provides theoretical basis for thermal protection.In this paper,based on theoretical analysis and experimental verification,the piezoelectric vector force test system is designed,and force measurement model with multi-sensor arrangement,high-frequency vector force measurement method,calibration technology and force measurement accuracy under thermal field are researched,respectively.The measurement system realize 5000N vector force measurement with deflection angle 0-30°,and force measurement accuracy is 0.7%.When loading force is 5000N.the first-order natural frequency is 461 Hz and the uncertainty of measurement is 3.72%under the conditions where initial temperature of dynamometer is 20°C,heat source is 40°C,vector force deflection angle is 0°,and test time is 100s,which realizes high precision test of multi-dimensional high-frequency variable force ratio vector force.The results also have engineering practical value and reference significance for vector force measurement in aerospace area.