Quasi-Linearization Design of Nonlinear Feedback Control Systems

This paper describes an application of the quasi-linearization principle and the use of off-line analog computers for the design of nonlinear feedback control systems. The design objective is to make the feedback system meet a set of transient as well as steady-state specifications under deterministic system inputs. According to the given specifications, the desired input to the nonlinear element is established. With the aid of an analog computer, the nonlinear element is tested by its desired input. Based on the test result, the nonlinear element is replaced by an equivalent linear element which has approximately the same input-output relationship as the nonlinear element. Linear system design techniques are then used to design the quasi-linearized systems, such that the actual input to the nonlinear element is indeed as desired. High-order feedback control systems in which the major nonlinearity, arises from the preamplifier and/or the error-measuring device are particularly amenable to this approach.