Adaptive Tracking Control With Global Performance for Output-Constrained MIMO Nonlinear Systems

In this article, a novel adaptive tracking control technique is developed for multiple-input-multiple-output nonlinear systems with model uncertainty and under output constraints occurring in a limited time interval (OCOLT). The OCOLT, which is a type of constraints occurring sometime after (rather than the beginning of) system operation and with limited duration, can be found in many practical systems and has not been effectively addressed in the literature until now. By designing a new shift function and with the aid of barrier functions, the constrained system is transformed into an unconstrained one. A new disturbance observer is then designed to estimate unknown disturbances. The resultant control method is able to not only address the OCOLT, but also deal with the constraint-free output case and the infinite-time constrained one (i.e., constraints existing for all $t\geq 0$ ) without the need to revise the control structure. Finally, the effectiveness of the proposed technique is assessed in simulation.