A continuous robust control design for a class of non-affine nonlinear dynamics with non-varnishing disturbance

In this paper, the problem for the control of a class of single-input-single-output (SISO) non-affine nonlinear system with non-varnishing disturbance is investigated. A continuous nonlinear feedback structure is utilized to tackle with the uncertain dynamics in the system. By taking the time derivative of the origin system, a transformed affine-like form is derived. The first order derivative of control input appears linearly in the augmented dynamics with unknown control direction. Nussbaum-type function is incorporated to estimate the unknown control direction. A revised Lyapunov based analysis is carried out to prove that under some moderate assumptions, the Semi-global Uniformly Ultimately Bounded (SGUUB) tracking result is achieved and all the closed loop signals are bounded. Numerical simulation results are presented to illustrate the performance of the proposed control law.