Robust PI Control with Improved Performance for Nonlinear Systems under Saturated Actuation

It is interesting and challenging to investigate the problem of prescribed performance constraints of uncertain nonlinear systems subject to inelastic control input saturation due to their potential conflicts. By designing a novel reference compensation mechanism that depends simultaneously on the input saturation error and the relative distance between performance boundaries and tracking errors, the reference signals are adaptively modified only when absolutely necessary, making the tracking control with pre-specified performance attributes affordable even in the presence of strict input constraints. In addition, a robust proportional-integral (PI) control scheme featuring with structure simplification and disturbance rejection is developed for a class of nonlinear systems with mismatched uncertainties. It is proved that all the closed-loop signals are bounded, and the proposed method can also ensure the output tracking performance. Numerical simulation results verify and clarify the effectiveness and superiority of the theoretical results.