A Sliding Mode Control Scheme for Quadrotor Based on Fixed-time Extended State Observer

A tracking trajectory problem for a quadrotor via second order sliding mode is concerned. Traditional sliding mode controller exists chattering phenomenon among control input when the state variables stayed in sliding surfaced. This phenomenon that is caused by sign function which is used for anti-disturbing might stimulate the unmodeled dynamics. In past articles and essays, using deceased coefficients of sign or replaced that sign function with saturation function are to restrain chattering phenomenon. In this paper, considering using sign function to suppress internal unmatched coefficients and external disturbances during quadrotor operating, by employing sliding mode combined with fixed-time observers to handle the chattering phenomenon. The significance of utilizing fixed-time observers in control scheme is to observe state variables and disturbances of system in fixed-time. Thereby, the sign function is substituted by observation value, which means anti-disturbing term changed from sign function to observation value. Sequentially, under the control scheme the chattering phenomenon is minished or even eliminated. Finally, a comparative simulation demonstrates that the presented scheme can improve control performance and restrict chattering phenomenon.