Stabilization of inertia wheel pendulum using output feedback back-stepping

The main contribution of the paper is an output-feedback application in the inertia wheel pendulum (IWP). Due to the absence of a separation principle, it is necessary to design control laws that guarantee robustness against the observer error. We present a design, which renders the system iISS with respect to the observer error and, hence, ensures robustness when the error is exponentially decaying. The advantage of our design over the observer-based backstepping scheme is that we employ nonlinear damping terms, which grow slower than those in (A toolkit for nonlinear feedback design, 1989), (Singular perturbations and input-to-state stability, 1996), and result in a "softer" control law.