1 Introduction
With the development of technology, many practical engineering systems can be transfomed into strict-feedback systems, such as battery energy storage systems[1] and wind turbine systems[2]. Therefore, the control design of strict-feedback systems has been a hot research direction[3]-[5]. However, the uncertainties arising from the unknown control coefficients make the control design of strict feedback systems extremely difficult. Thus, the study of strict-feedback systems with unknown control coefficients is both challenging and meaningful. For the unknown control coefficients, the reference [6] overcame the lack of information about the virtual control coefficients by utilizing the observation gain matrix determined by the convex combination technique. The reference [7] constructed an adaptive backstepping procedure based on the fuzzy approximation capability and variable partition technique to compensate for uncertainties. The reference [8] approximated an unknown nonlinear function of a system using fuzzy-logic systems and designed a novel Lyapunov function to eliminate the requirement of lower bounds of the unknown virtual control coefficients in control laws. However, most of the current studies of strict-feedback systems with unknown control coefficients are limited to a backstepping design approach, which makes the design process more complex when the model order is large. In the existing studies, the fully actuated system approach has not been utilized. To further simplify the controller design process, the fully actuated system approach will be applied in this paper.