Singular perturbation methods in the design of observers and stabilising feedback controllers for multivariable linear systems

Singular perturbation methods are used to reduce the design of stabilising feedback controllers for a class of (n+m)th-order systems with inaccessible states to the design of nth-order observers and associated feedback controllers for nth-order reduced systems obtained by ignoring `parasitic¿ elements that correspond to the presence of a small parameter in the state equations of the (n+m)th-order systems.