## Barrier Lyapunov functions for the control of output-constrained nonlinear systems.(English)Zbl 1162.93346

Summary: We present control designs for single-input single-output nonlinear systems in strict feedback form with an output constraint. To prevent constraint violation, we employ a barrier Lyapunov function, which grows to infinity when its arguments approach some limits. By ensuring boundedness of the barrier Lyapunov function in the closed loop, we ensure that those limits are not transgressed. Besides the nominal case where full knowledge of the plant is available, we also tackle scenarios wherein parametric uncertainties are present. Asymptotic tracking is achieved without violation of the constraint, and all closed loop signals remain bounded, under a mild condition on the initial output. Furthermore, we explore the use of an asymmetric barrier Lyapunov function as a generalized approach that relaxes the requirements on the initial conditions. We also compare our control with one that is based on a quadratic Lyapunov function, and we show that our control requires less restrictive initial conditions. A numerical example is provided to illustrate the performance of the proposed control.

### MSC:

 93B51 Design techniques (robust design, computer-aided design, etc.) 93C40 Adaptive control/observation systems 93D05 Lyapunov and other classical stabilities (Lagrange, Poisson, $$L^p, l^p$$, etc.) in control theory 93D30 Lyapunov and storage functions
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