Abstract

The rotary inverted pendulum (RIP) is an underactuated mechanical system that can be balanced in the upward position, by applying the linear control theory based on a nonlinear dynamical model linearized around that position. Its structure makes it possible to implement controllers designed for energy minimization in the non-linearizable region. Due to the limited validity of the resulting linear model, a nonlinear control is needed to automatically move the pendulum close to the linearized region, starting from its stable downward position. A RIP platform has been built to experimentally test a switched control strategy design, which combines an energy-based nonlinear controller for swinging up the pendulum and a linear quadratic regulator for the balancing task. Experimental results validate the performance of this approach on the physical prototype.