Output Feedback Tracking Control for Second-Order Nonlinear Systems in Predefined Time

This paper investigates the tracking control problem for second-order nonlinear systems by output feedback. First, a novel predefined-time state observer is designed by introducing a time-varying scaling function. Then, a continuous predefined-time control law is presented with the help of the sliding mode control method. The proposed control law has no singularity problem and it can ensure the upper limit of the resulting convergent time can be predesignated without relying on initial conditions. Finally, a simulation example is carried out to testify the efficiency of the present control law.