Robust Nonlinear Control Design — State Space And Lyapunov Techniques Systems Control Foundations Applications

This concept extends Lyapunov theory to quantify how disturbances affect the state. Instead of requiring the system to converge to zero, the goal is to bound the state by a function of the input disturbance. A system is ISS if its behavior remains within an acceptable region, regardless of bounded disturbances. This allows engineers to design controllers that guarantee safety margins rather than just theoretical convergence.