Adaptive modular control for a class of nonlinear systems with unknown time-varying parameters

Nonlinear time-varying systems exist widely in practice. However, many adaptive control schemes developed for such systems require their parameters to be slowly time-varying. This paper presents an adaptive modular control scheme for parametric strict feedback nonlinear time-varying systems. The parameters considered include continuously time-varying or discontinuous piece-wise constant parameters and they are not necessarily restricted to be slowly time-varying or infrequent jumping. It is shown that the proposed control scheme can guarantee the uniform boundedness of all closed-loop system signals. The performance of the tracking error in the mean square sense with respect to the parameter variation rate is also established.