Smoothly Combining Steady State Predictions With PI Control

Two first order nonlinear controllers are introduced: partial state setting and error modulated state setting. Both controllers smoothly combine feedforward steady state predictions with integral control. In both controllers the mixing is controlled though the use of a single gain that determines how aggressively the steady state predictions are used. Steady state error bounds are presented for each controller. For error modulated state setting control steady state errors can be eliminated if the maximum expected error in the steady state predictions is known. Both controllers are demonstrated to improve the transient response of a simulated nonlinear second order variable gain plant when compared to a well tuned proportional plus integral controller.