First we introduce the concept of the Furuta Pendulum. A very accurate explanation of it is as follows:
"The Furuta pendulum consists of a driven arm which rotates in the horizontal plane and a pendulum attached to that arm which is free to rotate in the vertical plane". (1)
Resources:
(1) Technical Report: On the dynamics of the Furuta pendulum
Ben S. Cazzolato and Zebb Prime
University of Adelaide, SA 5005, Australia
URL: http://data.mecheng.adelaide.edu.au/robotics_novell/projects/2004/Pendulum/Furuta_Pedulum_Internal_report.pdf
DESARROLLO Y CONTROL DE UN PÉNDULO DE FURUTA
A. Valera, M. Vallés, M. Cardo Dpto. Ingeniería de Sistemas y Automática Universidad Politécnica de Valencia
URL: http://www.cea-ifac.es/actividades/jornadas/XXIV/documentos/ro/77.pdf
The Furuta Pendulum - Wikipedia Encyclopedia
URL: http://en.wikipedia.org/wiki/Furuta_pendulum
Coriolis Effect - Wikipedia Encyclopedia
URL: http://en.wikipedia.org/wiki/Coriolis_effect
Centripetal Force - Wikipedia Encyclopedia
URL: http://en.wikipedia.org/wiki/Centripetal_force
Video: Pendulo Invertido Rotacional o Pendulo de Furuta
URL: http://www.youtube.com/watch?v=IIuntmibhoA