Designing a Generalized Predictive Control with Self-Tuning Regulator Structure to Prevent the Effect of Actuator Rate Saturation

Physical systems often contain constraints and limitations. Actuator rate saturation is one of these limitations that has adverse effects on the flight control system which increases the oscillating response and thus the instability of the system. Actuator rate saturation is one of the main reasons for pilot-induced oscillations (PIOs). This paper proposes a model predictive control algorithm with two degrees of freedom structure to prevent the destructive effects of actuator rate saturation on the flight control system. Also, by obtaining starting point of the opening loop position in the flight system and the frequency at which the actuator rate saturation is activated for the first time, the saturation effects are well predicted. Then, by introducing an analytical method similar to one of the conventional methods of robust control known as loop shaping method, proposed model predictive controller parameters are adjusted and the stability and robustness of the closed-loop system against the uncertainty of the controller parameters are investigated. In this method, by obtaining robust patterns, an attempt has been made to shape it in such a way that disturbances and noise are suppressed in a frequency range. It also shows how the controller and pilot work by using a switch. Finally, the designed controller is compared with the proportional-integral-derivative controller (PID) that is common in the industry and its advantages are shown.