Research On Aerodynamic Parameters Identification Of Projectile Based On Target Shadows

The digital Charge-coupled Device (CCD) shadowgraph system has become an important means of testing in Ballistic Range experiments with its high precision, easy data interpretation and other characteristics. Orthogonal Photos of bullet flying through the camera station captured by the digital CCD shadowgraph system are interpreted combining with the correlation coefficient of space base demarcated to get bullet attitude angle, speed and other information. Then, Aerodynamic parameters of the bullet can be received by Engineering Computing or Parameter Identification dealing with the information.For purpose of facilitating experimental operation and shortening experimental period, Photographic System Transfer Protocol is established on the basis of the description about the structure and the working principle of Target Shadowgraph System, designing and developing Shadow Photography Station Control Software and Shadowgraph General Control Software which control remotely the process of target experiment and transmit experimental data. System space calibration and image data processing method are improved and in the combination of the reality of image feature point interpretation, a Grey Threshold computing method is drawn up which enhances the speed and precision of projectile coordinate interpretation. In order to the ease of subsequent processing of experimental data, a complicated exterior ballistics model is simplified properly according to the characteristics of target experiment. In the meanwhile, a simplified ballistics model of Target experimental projectile motion is set up and it increases communicational efficiency. By means of target shooting experiment, verifying the reality of Photographic System and compiling Chapman-Kirk method and maximum likelihood method to identify the aerodynamic coefficient of obtained laboratory data and gain the aerodynamic coefficient that consistent with experimental data. In consideration of the sophisticated procedure of aerodynamic coefficient identification and inefficient calculation, an aerodynamic parameter engineering computing is proposed.The shooting experiment testified that the improved Target Shadowgraph System is highly reliable and projectile coordinate interpretation has pinpoint accuracy. In addition, it is also proved that Photographic Software Control System makes the test straightforward and convenient which provides an adequate laboratory environment to theoretical analysis. Comparing with the identified results, it has been demonstrated that Engineering Computing can meet requirements of experimental accuracy.