Conditional feedback systems ¿ A new approach to feedback control

In the classical single-loop feedback system, feedback acts not only to modify the influence of disturbances but also to determine the basic character of the input-output response. The inherently close association of these two effects has been a constant trial for designers and students since the inception of classical feedback, and has usually required that design requirements be compromised. Basically new configurations for feedback systems are introduced in which these effects of feedback are separated. In the new systems, feedback acts solely to reduce the influence of disturbances and thus to determine the response of the system to external loads and internal parameter variations. The character of the input-output response is independent of transmission around the feedback loop. The term ¿conditional feedback¿ has been introduced to distinguish the limited role that feedback plays in these new systems as compared with the classical system. Conditional feedback systems permit requirements on input-output response and on disturbance-output response to be met independently and offer a broad new range of performance characteristics for both linear and nonlinear systems in which there is substantial energy storage.