Modeling and Control of a Pendubot with Static Friction

The pendubot is an underactuated mechanical system with two degrees of freedom but only one control input. Several control techniques have been applied for swinging up and balancing the pendubot, but it is common to neglect the effects of friction in the joints of the system. In this paper we take a different approach by considering that the first joint of the pendubot has a significant amount of friction and it can not be neglected. We first review some friction models, including one that has been recently proposed by the authors. Secondly, we use some simple swing up and balancing controllers which compensate the friction effects. At the end, the results allow us to validate not only the viability of this approach, but also the proper identification of the friction model.