Sensitivity shaping with degree constraint by nonlinear least-squares optimization

Authors:	Nagamune Ryozo, University of California, Berkeley, United States Blomqvist Anders, Royal Institute of Technology, Sweden
Topic:	2.5 Robust Control
Session:	Robust Controller Synthesis by Norm Minimization
Keywords:	Sensitivity function, Frequency responses, Least-squares approximation, Robust control, H-infinity control

Abstract

This paper presents a new approach to shaping of the frequency response of the sensitivity function. A sensitivity shaping problem is formulated as an approximation problem to a desired frequency response with a function in a class of sensitivity functions with a degree bound, and it is reduced to a finite dimensional constrained nonlinear least-squares optimization problem. A numerical example illustrates that the proposed method generates controllers of relatively low degrees.