2kπ, the juggling robot

Abstract

2k/spl pi/ is an experimental robot consisting of a manipulator carrying a pendulum. It has 5 DOF; 3 angles for the manipulator and 2 angles for the pendulum. The manipulator DOF are actuated by electric drives, while the pendulum DOF are not actuated. The goal is to design a control law steering the pendulum from the lower equilibrium to the upper equilibrium, and more generally able to stabilize the pendulum while the manipulator is moving around. This system is typical of underactuated, nonlinear and unstable mechanical systems. The paper presents a planification of open-loop trajectories steering the pendulum from the lower to the upper equilibrium and the design of a tracking controller, each time exploiting the flatness property. The control is implemented in real-time.