Nonlinear adaptive observer design without a priori knowledge on the unknown parameters
无未知参数先验信息的非线性自适应观测器设计

The adaptive observer design is investigated for a class of nonlinear systems with unknown parameters. Being different from the existing results, the nonlinear system studied here is more general and less dependent on a priori knowledge including 1) the upper bound of the (Euclidean) norm of the system unknown parameters; 2) the non-Lipschitz continuous nonlinear dynamics of the measurable output; 3) the explicitly dependence of the system output upon the control input. By adding an adaptive regulator to estimate the norm of the unknown parameters, a novel approach is developed under some conditions to design the nonlinear adaptive observer. The observer designed is globally asymptotically convergent, i.e., it not only gives the convergent reconstruction of the system states, but also guarantees the uniform boundedness of the estimations of the unknown parameters. In addition, the reduced-order observer design is considered when the system output is independent of the control input. A simulation example is given to illustrate the correctness of the theoretical results of this paper.