Real-Time Disturbance-Observers; Origin and Evolution of the Idea Part 1: The Early Years

This paper is the first part of a two-part series which will trace the earliest origins of the novel-idea of a "disturbance-observer", as that idea emerged within the context of modern, MIMO state-variable system theory and was published in various control-conference proceedings and in systems/control journals. The technical evolution of the Theory of Disturbance-Observers as it occurred chronologically over the period 1968-1985 will be presented in a subsequent paper.