The Circular Cloverleaf Blind Juggler (CCBJ) pushes the boundary of sensorless robotic juggling even further. Developed in the Bachelor Thesis of Alessandro Schär, the CCBJ features four tilted paddles that result in a circular ball motion where the ball bounces from paddle to paddle.
A numerical stability analysis revealed that the same paddle shape and motion as used in the Blind Juggler enable the CCBJ to juggle balls without sensors. The key difference to previously developed machines is that the ball impact velocities are nominally oblique to the paddle surface (as opposed to perpendicular in the other juggling machines). For this reason, it is essential to consider the ball’s spin and its relation to the horizontal component of the impact velocity in the derivation of the nominal ball trajectory and in the stability analysis. We used the same impact model as in the stability-analysis of the Blind Juggler, which is presented by Rod Cross in Grip-Slip Behavior of a Bouncing Ball in the American Journal of Physics (2002).