Output-Feedback Prescribed Performance Control for the Full-State Constrained Nonlinear Systems and Its Application to DC Motor System

In this study, an output-feedback prescribed performance technique with disturbance compensation is performed for full-state constrained nonlinear systems. A prominent characteristic of this technique is that not only the prescribed tracking performance is achieved when the partial states are measurable but the associated disturbances and full-state constraints are also considered, which makes the design of a high-performance controller extremely difficult. To this end, extended state observer (ESO) and nonlinear disturbance observer (NDO) are integrated to estimate unknown disturbances and unmeasurable states. Moreover, the barrier Lyapunov function (BLF) and prescribed performance function (PPF) are associated to keep the tracking errors within specified ranges and constrain all system states at all times. Then, an output-feedback prescribed performance control (PPC) algorithm with state estimation and disturbance compensation is developed. Furthermore, the stability of the closed-loop controller–observer system is certificated by utilizing the Lyapunov theory. Finally, the effectiveness of the algorithm is verified by its application to the dc motor system.