Quadrocopter ball juggling

This paper presents a method allowing a quadrocopter with a rigidly attached racket to hit a ball towards a target. An algorithm is developed to generate an open loop trajectory guiding the vehicle to a predicted impact point - the prediction is done by integrating forward the current position and velocity estimates from a Kalman filter. By examining the ball and vehicle trajectories before and after impact, the system estimates the ball´s drag coefficient, the racket´s coefficient of restitution and an aiming bias. These estimates are then fed back into the system´s aiming algorithm to improve future performance. The algorithms are implemented for three different experiments: a single quadrocopter returning balls thrown by a human; two quadrocopters co-operatively juggling a ball back-and-forth; and a single quadrocopter attempting to juggle a ball on its own. Performance is demonstrated in the Flying Machine Arena at the ETH Zurich.