Disturbance observer based on NTSM output tracking control for second-order systems with power integrators and input quantization

In this paper, a composite finite-time tracking controller is designed for second-order systems with power integrators and input quantization, where the tracking reference signal is generated by a power-integrator exogenous system. A fixed-time disturbance observer is presented to estimate the unknown disturbances. And then a novel non-singular terminal sliding mode (NTSM) surface is constructed. Based on sliding mode surface (SMS) and disturbance estimation, two composite finite-time tracking controllers are developed for two different cases. The controllers make the system trajectories track the desired signal in finite-time. Simulation results are employed to demonstrate the effectiveness of the proposed schemes.