Early developments in nonlinear control

The paper examines the early developments in nonlinear control engineering. It begins by briefly reviewing the status prior to world war II and then concentrates on the developments in approximately the next two decades. A significant amount of this work is seen to have had its foundations in the need to obtain methods to solve fire control and missile control problems. The major analytical techniques of the phase plane, the describing function and Tsypkin´s method for relay systems, are discussed in some detail. Further sections discuss the limitations placed on system implementation and simulation studies by the hardware available in the late 50´s and finally a brief survey of publications on nonlinear control topics at that time is given