Abstract
This paper is concerned with a robust stabilization problem for plant uncertainty of the first-order lag type. The necessity of the robust stabilizability is investigated using conformal mappings and the Nevanlinna-Pick interpolation theory. A necessary condition is derived for the existence of a controller that stabilizes all SISO linear plants with prescribed bands of the gain and time constant. The sufficiency is also discussed based on the result for the weighted stable factor perturbation. We propose a method of choosing the weighting functions and the band function corresponding to the first-order lag type perturbation.
