Modeling and Simulation of a Low-Aspect-Ratio UAV in Gliding Flight

The object of this study was a fast gliding unmanned aerial vehicle (UAV) with an extremely small aspect ratio which is dropped by another aircraft (a carrier). The aim was to investigate the behavior of the UAV using different mathematical models for flight simulations. To address this problem, two different simulation tools were employed: SDSA (Simulation and Dynamic Stability Analysis) package and MATLAB Simulink. Simulations were performed (with and without a controller) using aerodynamic data that were computed by PANUKL package (low-order potential software) and compared with MGAERO software (Euler’s equations). The results showed that for a given aerodynamic dataset, the effectiveness of control surfaces which is associated with static stability has the biggest impact on range for a gliding UAV in tailless configuration. It was noticed that neglecting the change in inertia moment due to the CG shift is less important than neglecting the derivative with respect to pitch rate; however, the overall impact is small enough to be neglected. The best results were obtained when the vehicle was unstable but operated with an active PID controller, yielding a very significant increase in range, from several dozen percent to over 100%, depending on the specific case. The model fidelity, especially the impact of compressible effect, must be included when the vehicle is dropped from a high altitude and acceleration to supersonic speed is expected to avoid range overestimation. The research presented in this paper combines all subjects discussed above: aerodynamic fidelity for a low-aspect-ratio object in compressible flow conditions and closed-loop control optimized for enhanced flight performance.