A higher order sliding mode control with self-tuning law algorithm is proposed for SISO uncertain nonlinear
systems with unknown bound in order to reduce chattering. A bipolar sigmoid function on-line adaptation and an adjustable
control gain tuning approach without high frequency switching are developed. The stability of proposed algorithm is proven
by using the Lyapunov theory in finite time and the robustness is guaranteed. The upper bounds of uncertainties are not
required to be known in advance. The simulation results show the effectiveness of the control method.