Output feedback stabilization with prescribed performance for uncertain nonlinear systems in canonical form

The problem of designing an output feedback stabilizing controller for nonlinear systems in canonical form, while guaranteeing prescribed transient and steady state performance bounds, without incorporating the actual system nonlinearities and/or their approximations, is considered in this work. The proposed design follows three steps. Assuming full state measurement, a state feedback controller is firstly constructed to solve the problem and subsequently its output is constrained via the utilization of a carefully selected saturation function to preserve the stability and performance attributes established in its absence. Finally, at a third stage the actual system states are replaced by the states of a high gain observer to formulate an output feedback controller. It is proven that only the boundedness of the closed loop system is sufficient to achieve stabilization with prescribed performance. As a consequence the proposed output feedback prescribed performance control design proves significantly less complex compared to the relevant literature, while reducing the peaking phenomenon which is typically related to the operation of the high gain observer. Simulation studies clarify and verify the approach.