Robust control for uncertain systems with application to helicopter model

This paper is concerned with robust stabilization and robust H_∞ control of a class of uncertain systems. The class of the systems is continuous-time systems with norm-bounded time-varying parameter uncertainties. We first show relationships between robust H_∞ control via linear output feedback and a scaled H_∞ control problem and between quadratic stabilization and a standard H_∞ control problem for uncertain systems. These implies that a quadratic stabilizing controller for uncertain systems can be designed by solving a standard H_∞ controller. Next, the results are applied to a helicopter model. The model is likely to have identification error between the original model and its linear mathematical representation. It is shown that robust controllers designed for uncertain systems work effectively.