Measurement of Drag Coefficient and Estimation of Aerodynamic Coefficients Using Nonlinear Least Square Method on Simulated Aeroballistic Tests Considering Experimental Errors

Extraction of aerodynamic coefficients and dynamic derivatives with high accuracy is one of the most important applications of aeroballistic experiments. This is done by measuring the linear and angular positions and the relevant speeds and other parameters depending on the sensors used in the laboratory. The most important question before and after these experiments is the accuracy of the obtained results, proving the correctness of the method and algorithm used in extracting the coefficients and the effect of different errors on the results. For this purpose, the effect of error in the measured values relative to the desired aerodynamic coefficients can be calculated and investigated before performing the modeling test. In this study, in addition to performing flight tests to determine the drag coefficient, a comparison of the effect of error in a variety of parameters measured in aerodynamic coefficients is also presented. In a series of flight tests, the drag coefficient of the sphere was extracted with an error of less than 3%, which shows the ability to estimate aerodynamic coefficients with high accuracy from stests. Errors of aeroballistic tests can be caused by sensors, sample construction error, error of estimation algorithm, etc. By considering each of them, the final error rate is calculated and the flight results modeled in the presence of error can be compared with error-free values. This study will show the effect of the error of each flight data on the numerical solution of the flight model and the results of the estimated coefficients, and therefore how carefully should be selected in the selection of each sensor in aeroballistic flight tests.