Dynamics modeling and control design for a winged eVTOL aircraft

VTOL vehicles are of great interest at the moment for urban air mobility because of their versatility. These vehicles have the ability to take-off and land without the necessity of a long runway, being compared to helicopters. However, their appeal is based on the fact that are considered a breakthrough over helicopters due to their efficiency in cruise flight, comparable to fixed wing aircrafts. For these reasons, VTOL vehicles reduce the expenses in complex facilities and improve performances from an efficiency point of view. Within this new technology field, NEOPTERA Ltd presents itself as one of the companies seeking to develop a civil VTOL vehicle for urban air mobility: the eOpter. NEOPTERA is currently developing different prototypes of the eOpter, one of which was selected for this project. The main objective of the project is the development of a flight simulator and a flight controller for the mentioned prototype, a 60cm wingspan version of the eOpter. The innovative VTOL concept presented by NEOPTERA is a two wings tandem configuration with four electric motors on each wing providing energy to a propeller each. A VTOL vehicle flight can be divided into three modes. A vertical take-off and landing, a transition to cruise flight, and the cruise flight itself. The motivation behind this study is to have proper control laws capable of stabilizing the aircraft dynamics during the three flight operating modes. A remarkable aspect of the project developed is treating the entire flight envelope as a continuous flight path, avoiding discontinuity issues when passing from one flight phase to another. In order to design the flight control laws for the prototype, it is necessary to design certain mathematical models describing the dynamics of the aircraft and its behaviour during each flight mode. This study goes through the development of these mathematical models, their simulation, a stability analysis of the model created and the design of appropriate stabilizing control laws. The obtained simulation model is validated by simulating the vehicle flight and observing the physical behaviour. The control laws developed allow to stabilize the vehicle while enhancing the flight performances and an integrator controller is implemented for reference tracking purposes, being its robustness tested on the linear models of the aircraft. The results obtained shows a very reliable simulator for longitudinal flight, while for lateral-directional flight further analysis need to be done. A full mission for longitudinal flight was simulated and the results obtained are very promising. The prototype is currently undergoing some flight tests. It is expected to obtain information from these tests that will help to improve the control system of the vehicle by observing its behaviour in real flight. Further steps will include implementing the gain scheduling method in the non linear simulator, in order to achieve stability for the entire flight envelope and test the obtained tuned controller on the physical prototype without going through additional tuning campaigns.