Nonlinear Feedback Control of the Rotary Inverted Pendulum
Naval Postgraduate School Monterey United States
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The inverted pendulum, a popular problem of study, is presented in many textbooks as a nonminimumphase system. The majority of control algorithms for this problem include linearizing the system about afixed operating point. In this thesis, a nonlinear form of control is considered.A model for the rotary inverted pendulum system was derived and validated by comparing simulationsusing the derived equations to experimental data. The system parameters were tuned until the simulationand experimental data fit. A feedback linearization controller was then designed based on the modelderived. The simulated implementation of the feedback linearization was successful but indicatedcontinuous motion of the system. The experimental results of the feedback linearization controller wereless successful than simulations. The simulated results also indicated unstable zero dynamics of the system,which were characterized and confirmed to be unstable. Finally, an intuitive fix was applied to add terms tothe feedback linearization controller to account for the zero dynamics. The results of this controller insimulation were successful but did not produce a substantially different response in the experimentalsystem.