Review of designs and flight control techniques of hybrid and convertible VTOL UAVs

This paper provides a broad perspective and analysis of the work done in control hybrid convertible unmanned aerial vehicles (UAVs) for main existing designs. These flying machines are capable vertical take off landing (VTOL) helicopter mode able to transition high-speed forward flight airplane vice versa. aims at helping engineers researchers develop systems VTOL UAVs. To this end, historical first shows technological advances aircraft over years. The concepts state-of-art methods UAVs presented discussed. study both common parts fundamental differences modeling, guidance, control, allocation each hybrid-VTOL-UAV type. open challenges current trends field highlighted. namely: 1) augmenting or replacing classical controllers with data-driven such as neural networks machine-learning-based controllers; 2) incorporating much knowledge vehicle possible into controller, example through model predictive model-based nonlinear 3) trend towards finding unified-control approach valid all modes without need switch among perform predefined-gain scheduling, 4) mitigate complexity available computing resources.