Friction and friction compensation in the Furuta pendulum

Inverted pendulums are very well suited to investigate friction phenomena and friction compensation because the effects of friction are so clearly noticeable. This paper analyses the effect of fiction on the Furuta pendulum. It is shown that friction in the arm drive may cause limit cycles. The limit cycles are well predicted by common friction models. It is also shown that the amplitudes of the limit cycles can be reduced by friction compensation. Compensators based on the Coulomb friction model and the LuGre model are discussed. Experiments performed show that reduction of the effects of friction can indeed be accomplished.