Design of the Pendulum Juggler

We present the analysis and design process of the Pendulum Juggler, a robot that juggles a ball with an actuated paddle mounted to a swinging pendulum. The unconstrained ball travels up to 1 m horizontally, reaching an apex height of 1.1 m between impacts. Using a perturbation analysis, we show that the ball trajectory is locally stable without feedback. The pendulum consists of a four-bar linkage, optimized to keep the paddle perpendicular to the impact velocity of the ball. We verify the stability in experiments with a prototype of the Pendulum Juggler, demonstrating sustained juggling at amplitudes of up to 25°.