Adaptive Control of Nonlinear Time-varying Delay Systems with Unknown Control Gain Signs

Based on the principle of sliding mode control and the property of Nussbaum-type functions, an adaptive neural control scheme is proposed for a class of MIMO nonlinear time delay systems with unknown function control gains. By utilizing the integral-type Lyapunov function and Young's inequality, the restriction of the control gains and the assumption of time-varying delay uncertainties are relaxed. By choosing appropriate Lyapunov–Krasovskii functionals, unknown time-varying delay uncertainties are compensated for. By theoretical analysis, the closed-loop control system is proved to be semi-globally uniformly ultimately bounded.