Tilty was developed as a side research project during my first year as a Master's student. The main goal was to quickly develop a new tilt-rotor aircraft using off the shelf components and using a simple control system. This would enable us to quickly move from construction, to testing, without a lengthy code development time. It is important to remember this was built in 2017 before PX4 and Ardupilot had implemented tilt-rotor flight control. Once the aircraft was developed and transitioned, we examined different control schemes that could make the aircraft simpler for the test pilot. Two research papers were written about the project in depth and are linked at the bottom of the article.
The design takes off like a normal quadcopter and can use a standard quadcopter PID controller. In forward flight, the rear 2 rotors tilt backward to provide forward thrust while the front two rotors shut off. Control in airplane mode uses the same PID control loops used for the quadcopter controller with scheduled gains. In fact, the control surfaces are always reacting to the output from the PID in both hover and cruise. To quickly tune the system, the airplane gains and the quadcopter gains were tuned independently. During transition, the gains shift as the motors tilt. A full video of the transition is shown below. Despite the very simple control scheme, the design allows for a nice steady transition.
