Frequency domain performance analysis of nonlinearly controlled motion systems

At the heart of the performance analysis of linear motion control systems lie essential frequency domain characteristics such as sensitivity and complementary sensitivity functions. For a class of nonlinear motion control systems called convergent systems, generalized versions of these sensitivity functions can be defined. Incorporating such effective means in nonlinear motion control design requires efficient computation or estimation methods. In this paper we present a computationally efficient method for estimating these sensitivity functions for a class of convergent Lur´e type systems. The results are illustrated by application to an industrial example of a variable-gain controlled optical storage drive.