Adaptive Tracking Control of Nonlinear Systems with Unmodeled Dynamics and Unknown Gain Sign

Based on backstepping design, a novel adaptive tracking control scheme is proposed for a class of strict feedback nonlinear systems with unmodeled dynamics and completely unknown function control gain in this paper. An available dynamic signal is used to dominate the unmodeled dynamics. The unknown virtual control gain signs are dealt with using the property of Nussbaum function. The controller singularity problem is avoided using integral Lyapunov function. By theoretical analysis, the closed-loop systems is proved to be semi-global uniformly ultimately bounded.