Optimisation of Trajectories for Wireless Power Transmission to a Quadrotor Aerial Robot

Unmanned aircraft such as multirotors are typically limited in endurance by the need to minimise weight, often sacrificing power plant mass and therefore output. Wireless power transmission is a method of delivering power to such aircraft from an off-vehicle transmitter, reducing weight whilst ensuring long-term endurance. However, transmission of high-powered lasers in operational scenarios carries significant risk. Station-keeping of the laser spot on the receiving surface is crucial to both ensuring the safety of the procedure and maximising efficiency. This paper explores the use of trajectory optimisation to maximise the station-keeping accuracy. A multi-agent model is presented, employing a quadrotor unmanned rotorcraft and energy transmission system, consisting of a two-axis gimbal, camera sensor and laser emitter. Trajectory is parametrised in terms of position and velocity at the extremes of the flight path. The optimisation operates on a cost function which considers target range, beam angle of incidence and laser spot location on the receiving surface. Several cases are presented for a range of variables in the trajectory and different conditions in the model and optimisation algorithm. Results demonstrate the viability of this approach in minimising station-keeping errors.