A reduced order model for prediction of aerodynamic loads on an unmanned aerial system with hybrid quadcopter biplane configuration

Army Research Lab (ARL) has recognized Unmanned Aerial Systems (UAS) with Vertical Take-Off and Landing (VTOL) to be capable of delivering paramount tasks such as intelligence, surveillance, electronic attack, etc. in the future. Advances in manufacturing and material technologies have opened a new design space for novel VTOL UAS configurations but significant knowledge gaps still exist to design a configuration which can achieve the desired performance. ARL designed research VTOL UAS platforms called Common Research Configuration (CRC) with hybrid quadcopter biplane concept to enable a comprehensive study on such aircraft. Inherent to all VTOL UAS such as CRC platforms is the need for a transition from hover to forward flight and forward flight back to hover throughout a mission. This transition produces highly non-linear loads on the wings due to the rotor-wing interactions and may present a significant challenge for robust control. The aim of this study is to develop a reduced order model (ROM) capable of predicting loads on CRC-3, the smallest size of the CRC generation with 3lb weight. A set of data obtained from hundreds of CFD simulations for a wide range of conditions are used as the training set for a neural network. The predicted loads by the developed ROM show good agreement with the test set. Additionally, the dynamic body equations are coupled with the ROM to investigate the CRC-3 flight dynamics. CFD simulations are conducted using our in-house solver, CFDFoam.