Singular perturbation methods have successfully been used in control applications to deal with multi-time-scale systems, by which the system is decomposed into a ‘slow’ subsystem and one or more ‘boundary layer’ or ‘fast’ subsystems[56]. A system expressed in explicit singularly perturbed form generally has a small parameter ε appearing as a multiplier to the derivative of the ‘fast’ variables. Here, the system decomposition is achieved by setting ε =0 and solving for the ‘fast’ subsystem variables in terms of the ‘slow’ ones, and then substituting them in the ‘slow’ subsystem equations[58]. © 2013, Springer-Verlag Berlin Heidelberg.