Capture of Fixed Wing UAVs with Robot Arms and Other Capture Mechanisms

This thesis explores the feasibility of catching fixed-wing UAVs with robotic systems as a space-economic alternative to conventional runway landings. The type of recovery method proposed here is relevant to enabling the use of fixed-wing aircraft in space-deprived urban environments for applications where multirotors would be unsuitable. To begin, capture with a robot arm is studied in a small-scale experiment where a Denso VS050 robot is used to catch a 0.5 kg foam glider. These experiments highlight the importance of timing and velocity matching during interception as well as the inherent complexity of the approach. Next, in an effort to reduce complexity, several stationary capture mechanisms are conceptualised and the most promising is built for testing. The chosen mechanism is a fully-passive capture solution where the deceleration force is provided by a spring-powered arrest line. Tests with a 4.5 kg aircraft show that the deceleration profile experienced during capture is on par or better than that of a typical grass landing. Lastly, a hybrid system is explored where the robot arm and passive mechanism approaches are combined. This system is studied through simulation in an environment where an ABB IRB4600-60 robot is used to catch a 21.5 kg UAV. For this purpose an optimisation-based trajectory planner is proposed. Results indicate that the addition of a passive mechanism mitigates the timing and velocity matching issues observed with the first robot arm system. However, results also indicate that a larger robot with higher joint torque limits is needed to catch the UAV in the simulation. Overall, the thesis provides strong evidence that space-economic recovery methods are indeed feasible and that the hybrid mechanism approach is the most promising method for further research and development.