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System nonlinearities, immeasurableness, and uncertainties (especially their coupling/coexistence) have constantly challenged the control design, which requires the controller to be powerful enough to counteract the resulting negative effects. In this paper, a global adaptive output-feedback controller is designed for uncertain nonlinear systems. The proposed controller is of switching type, in which the design parameters are online adjusted on the basis of a switching logic in a recursive manner. This makes the controller powerful enough to compensate the system unknowns and dominate the system nonlinearities and therefore be applicable to a rather wide range of systems. Remarkably, our strategy allows the coexistence of an unknown control direction and unmeasured state--dependent growth but which are substantially excluded in the related literature.An example of the single-link robot arm systemis provided to illustrate the effectiveness of the proposed controller. [ABSTRACT FROM AUTHOR]

This paper is concerned with the adaptive leader-following consensus for first- and second-order uncertain nonlinear multi-agent systems (NMASs) with single- and double-integrator leader, respectively. Remarkably, the control coefficients of the followers need not belong to any known finite interval, which makes the systems in question essentially different from those in the related works. Moreover, parameterized unknowns exist in the nonlinearities of the followers, and unknown control input is imposed on the leader, which make the problems difficult to solve. To compensate for these uncertainties/unknowns, the leader-following consensus protocols are constructed by employing adaptive technique for the first-order and the second-order NMASs. Under the designed adaptive consensus protocols and the connected graph, the leader-following consensus is achieved. Finally, two examples are given to show the effectiveness of the proposed leader-following consensus protocols. [ABSTRACT FROM AUTHOR]