Swing-up control of pendubot with friction around an actuated joint

This paper considers the swing-up control problem of a 2-link underactuated manipulator called the Pendubot. For the system, a large number of useful methods have been obtained, but they cannot be applied to the system with friction around the links due to the existence of singular points. In this paper, we extend the energy-based control method of the Pendubot, taking in account the effect of friction around the actuated link. Applying the proposed control method, we can obtain a sufficient condition for vanishing of the singular points. In addition, the convergence to the swing-up position is guaranteed by using the proposed Lyapunov function and the LaSalle's invariance principle. The effectiveness of the proposed method is illustrated by numerical simulations.