Weak Signal Detection System For Wind Tunnel Balance Based On Correlation Theory

With the development of aerodynamics,wind tunnels for measuring the aerodynamic forces and moments of models such as automobiles,missiles,and spacecraft have been widely used.As the electromagnetic environment of wind tunnels becomes more and more complex,wind tunnel balances The requirements for signal detection systems are getting higher and higher.Aiming at the problem that the wind tunnel balance signal is weak and the detection system is greatly affected by interference and noise,it is difficult to accurately detect the weak signal of the balance in the noise.A wind tunnel balance weak signal detection system design based on related detection principles is proposed.The main content or innovations of this article are divided into the following aspects:(1)The research status of weak signal detection methods and balance signal detection systems are introduced.Analyzed the problems in the weak signal detection of wind tunnel balance,analyzed the noise source and characteristics in the balance signal detection,compared with the current balance signal detection system,discussed that related detection methods can effectively suppress noise interference in theory.(2)Through the principle discussion of related detection methods,the design of a quadrature lock-in amplifier based on related detection is given,and its center frequency is designed to be 10 k Hz.The system model was built by Simulink for simulation analysis and the hardware circuit was built for testing.It was found that the maximum error of the detection result was 1.3%,and the stability time of the detection result was 0.4s,indicating that the quadrature lock-in amplifier can accurately and quickly detect annihilation by noise Therefore,the balance weak signal detection system based on the quadrature lock-in amplifier has strong anti-interference ability,which can effectively amplify the weak signal of the balance and suppress noise.(3)A low-noise,high-linearity quadrature reference signal source and driving source with a gain range of-11?31d B and a gain step of 0.05 d B for a multi-channel phase-locked amplifier system is designed,using a digital closed loop Feedback control.Through the actual hardware test,the quadrature reference signal source can output a quadrature reference signal with an amplitude of 1V,a frequency of 10 k Hz,and a phase difference of 90°.The gain error is less than 0.1d B;the output voltage fluctuation range is 1.00±0.02 V.The amplitude stability is better than 2%.The results show that the quadrature reference signal source and bridge drive source have low noise,strong drive capability and high output signal stability.(4)Test the output signal of the wind tunnel balance bridge under the condition that the output differential voltage range of each bridge is 0.1m V?25m V,the excitation signal is±2.5V/80 m A/10 k Hz in parallel,and the orthogonal reference signal is 1V/10 k Hz..Through the test,it is found that the voltage resolution of the system for the balance signal detection is100 u V,the maximum error is 50 u V,and the accuracy is better than 2%,and the system can judge the force state of the resistance strain gauge by the positive or negative of the DC component amplitude.It shows that the system better solves the problem of signal jump caused by interference in the traditional detection system,effectively suppresses the internal and external noise of the system,accurately detects the weak signal of the balance,and has a large anti-interference performance in the actual test.The main performance indicators of the system design have been reached.