Nonlinear control of swing-up inverted pendulum

This paper presents plant modeling, analysis, and nonlinear control design and implementation for swing-up, pendulum regulation, and arm tracking of a rotational inverted pendulum plant. For the ideal case, the equilibrium states are characterized. It is shown, for example, that the pendulum cannot be kept at a fixed angle above the horizontal except in a vertical position. The control design centers on the pendulum regulation and arm tracking controllers. A sliding mode and a variable-gain PID controllers are chosen for regulation and tracking. Due to the strong coupling of the arm and pendulum dynamics, a 2DOF control configuration was used. A simple technique was used to swing-up the pendulum to within the region of attraction of the regulation controller. Results of computer simulations and laboratory photos are presented.