Non-linear sliding mode control for a rotary inverted pendulum

Due to the nature of PID controller, the inverted pendulum will seldom be in the steady state in a noisy uncertainty environment, which degrades the usefulness of PID controller in high-precision requirement system. A new robust non-linear Lyapunov based sliding mode controller is proposed for a Rotary Inverted Pendulum System in this paper. It is applied to swing up the pendulum and to stabilize it around the balancing state in the Lyapunov sense. Both the simulation and experiment show that, not only strong robustness with respect to system uncertainties and nonlinearities can be obtained, but also the pendulum position can dynamically converge to the desired balancing state by using the non-linear sliding mode control. Our approach extends the current PID controller design to linear sliding mode design and finally to nonlinear sliding mode design.