Figure 1: Sketch of a juggler doing a "butterfly."
Figure 2: A simulation of a robotic butterfly. The contact force is shown.
The Roles of Shape and Motion in Dynamic Manipulation:
The Butterfly Example
K. M. Lynch, N. Shiroma, H. Arai, and K. Tanie
Abstract
We are studying a juggler's skill called the ``butterfly.'' Starting with a ball resting on the palm of his/her open hand, a skilled juggler can accelerate and shape his/her hand so that the ball rolls up the fingers, over the top, and back down to the back of the hand. This paper describes a robotic implementation of the butterfly. The hand's shape and motion combine to effect the rolling motion of the ball, and we find that the shape and motion parameters enter the dynamic equations in a similar way. We define parameterized spaces of hand shapes and motions, and using a simulation based on the rolling equations, we identify shape and motion solutions that roll the ball from one side of the hand to the other. We describe an implementation of the butterfly on our planar dynamic manipulation testbed FLATLAND. This example is our first step toward exploring the roles of shape and motion in dynamic manipulation.See a video of the robotic butterfly.
Figure 2: A simulation of a robotic butterfly. The contact force is shown.