Study On Dynamic Characteristics Of Wind Tunnel Strain Gauge Balance Under Varying Loads

Wind tunnel strain gauge balance is a kind of multi-axis force sensor, and iswidely used in a variety of wind tunnel tests to measure the aerodynamic force andmoment loaded on aerodynamic models. The study of balance dynamiccharacteristics includes dynamic calibration experiment, mathematical modeling,dynamic decoupling and dynamic compensation. In the dynamic calibrationexperiment, balance is equipped with an unchanged load head to supply accurateloading points, and thus the dynamic characteristics of the balance under fixed loadcan be studied. However, in wind tunnel test, the balance is installed in aircraftmodel which is equivalent to a load on the balance, and it is required to measure theaerodynamic force and moment of various aircraft models. So, when the aircraftmodels are different, the equivalent loads on the balance are different and thusleads to changes of the balance dynamic characteristics. Then, the dynamicdecoupling and compensation device which is designed according to a fixed loadcannot play an effective role of decoupling and compensation for wind tunnel testdata. Therefore, the variation of the balance dynamic characteristics should beresearched and the dynamic characteristics of the balance under different loadsshould be corrected, so as to measure aerodynamic force and moment loaded onvarious aircraft models accurately.In order to study the load effect on the dynamic characteristic of the balance,the dynamic calibration experiments are conducted with different loads by the wayof changing weights fixed on the load head. The system identification methodbased on output error model is adopted to describe the dynamic mathematicalmodels of various channels of the balance with different loads. According to themathematical models of the balance, the dynamic feature parameters are analyzed,and the curve fitting method is employed to study the relationship between thebalance feature parameters and the loads mass. Then, in order to ensure gooddynamic response performance of the balance under different loads, the method ofstaged dynamic compensation solution is proposed and the dynamic compensatorare designed by the system identification method, so as to implement dynamiccompensation for balance under different loads and achieve good results. Furthermore, it is also studied that how to apply the zero-pole configuration methodto the adaptive dynamic compensation for balance under different loads.