Frequency-Domain Decoupling-Correction Method for Wind Tunnel Strain-Gauge Balance

Abstract

A frequency-domain decoupling-correction (FDC) method based on frequency-domain parameter matrix inversion is proposed to solve the problems of cross-axis dynamic coupling interference and dynamic error existing in the main channel output for multiaxis force sensors, for example, wind tunnel strain-gauge balance. The frequency-domain decoupling-correction function is calculated by means of power spectrum estimation according to the sensor step response experimental data, and the windowing approach is adopted to overcome the calculation error caused by the cycle extension of the intercepting data when FFT or IFFT is conducted. The method of FDC based on high/low-frequency signal decomposition is put forward in the process of the dynamic decoupling correction for the sensor output. The low-frequency components are decoupled and corrected by the method of static linear decoupling and static linear correction, and the high-frequency components are decoupled and corrected by the method of frequency-domain parameter matrix inversion in order to overcome the boundary aliasing error and the Gibbs phenomenon caused by the cycle extension of the intercepting data when FFT or IFFT is conducted. According to the static relationship between the sensor input and output, the static characteristic between the sensor input and the sensor dynamic decoupling-correction result is reconstructed so as to ensure that the sensor static characteristic remains unchanged. The dynamic decoupling-correction method is applied to the bar-shaped strain-gauge balance to validate its effectiveness. The result shows that the cross-axis dynamic coupling error ratios are reduced from 98.09% to less than 2%, and the adjust time of the balance main channel step response is shortened from nearly 4 s to less than 6 ms with the overshoot being reduced from 111.24% to less than 5% at the same time. The proposed method can substantially reduce the cross-axis dynamic coupling interference and further improve the response speed of the balance.