Kazuo Tanie

The roles of shape and motion in dynamic manipulation: the butterfly example

We study the juggler 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 combined hand shape and motion set 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 parametrized spaces of hand shape and motion, 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.

Motion planning for a 3-DOF robot with a passive joint

Studies motion planning from one zero velocity state to another for a three-joint robot in a horizontal plane with a passive revolute third joint. Such a robot is small-time locally controllable on an open subset of its zero velocity section, allowing it to follow any path in this subset arbitrarily closely. However some paths are preferred by the dynamics of the manipulator in that they can be followed at higher speeds. We describe an algorithm that plans collision-free paths in the robots configuration space, where the motions correspond to dynamically preferred robot motions. Thus the problem of planning fast trajectories in the robots six-dimensional state space is reduced to the computationally simpler problems of planning paths in the three-dimensional configuration space and time-scaling the paths according to the manipulator dynamics. Implementation on an underactuated manipulator is described.