Automatica, Vol.35, No.5, 929-935, 1999
Asymptotic regulation of time-varying uncertain nonlinear systems with unknown control directions
A robust asymptotic regulating control scheme is proposed for a class of time-varying uncertain nonlinear systems with both additive nonlinear uncertainties and unknown multiplicative terms. The signs of these multiplicative terms, so-called control directions, are unknown. The class of systems can be of arbitrary dynamic order, and except for the unknown multiplicative terms, they satisfy the strict feedback condition.