Extensions of dithered feedback systems

Abstract

Single loop dithered (at frequency ω₀) feedback systems containing a severely non-linear element, can be designed to behave quasilinearly to control signals with bandwidth small relative to ω₀. They can also have zero sensitivity to gain factor uncertainty. However, the constraints due to quasilinearity may lead to severely large ω₀. This paper presents an externally excited adaptive loop structure with ‘externally excited’ signal A₀ sin ω₀t and an added ‘adaptive loop’, which permits a large reduction in g. An additional phase-adaptive loop can be added to the above structures, which reduces the plant phase uncertainty and consequently the loop bandwidth requirements. Quantitative design procedures, with examples, are presented for the above structures, which reveal the advantages of the more complex designs.