3 research outputs found
Unified incremental nonlinear controller for the transition control of a hybrid dual-axis tilting rotor quad-plane
Overactuated Tilt Rotor Unmanned Aerial Vehicles are renowned for exceptional
wind resistance and a broad operational range, which poses complex control
challenges due to non-affine dynamics. Traditional solutions employ multi-state
switched logic controllers for transitions. Our study introduces a novel
unified incremental nonlinear controller for overactuated dual-axis tilting
rotor quad-planes, seamlessly managing pitch, roll, and physical actuator
commands. The control allocation problem is addressed using a SQP iterative
optimization algorithm, well-suited for nonlinear actuator effectiveness in
thrust vectoring vehicles. The controller design integrates desired roll and
pitch angle inputs. These desired attitude angles are autonomously managed by
the controller and then conveyed to the vehicle during slow airspeed phases,
when the vehicle maintains its 6 DOF. We incorporate an AoA protection logic to
prevent wing stall and a yaw rate reference model for coordinated turns. Flight
tests confirm the controller's effectiveness in transitioning from hovering to
forward flight, achieving desired vertical and lateral accelerations, and
reverting to hovering
Accurate position control of a flapping-wing robot enabling free-flight flow visualisation in a wind tunnel
Flow visualisations are essential to better understand the unsteady aerodynamics of flapping wing flight. The issues inherent to animal experiments, such as poor controllability and unnatural flapping when tethered, can be avoided by using robotic flyers that promise for a more systematic and repeatable methodology. Here, we present a new flapping-wing micro air vehicle (FWMAV)-specific control approach that, by employing an external motion tracking system, achieved autonomous wind tunnel flight with a maximum root-mean-square position error of 28 mm at low speeds (0.8-1.2 m/s) and 75 mm at high speeds (2-2.4 m/s). This allowed the first free flight flow visualisation experiments to be conducted with an FWMAV. Time-resolved stereoscopic particle image velocimetry was used to reconstruct the three-dimensional flow patterns of the FWMAV wake. A good qualitative match was found in comparison to a tethered configuration at similar conditions, suggesting that the obtained free-flight measurements are reliable and meaningful