In a paper in the context of controller design for DEAP actuators I came upon the following sentence:
Furthermore, the nonlinear behavior of the control plant requires either an adaptive or a robust design in order to ensure a precise and accurate control.
What is the relationship between a robust/adaptive controller and the nonlinearity of the control plant? Isn't it somehow always necessary to design a robust controller no matter whether the control plant is linear or not? Or are nonlinear plants in general more sensitive to parameter variations, e.g. nonlinear systems sensitive to initial conditions (chaotic behaviour)?