Quad-rotor unmanned helicopter control via novel robust terminal sliding mode controller and under-actuated system sliding mode controller

This paper uses the recently developed novel robust terminal sliding mode control (NRTSMC) and under-actuated system sliding mode control (USSMC) approaches to solve the strong coupling and under-actuated problems of a small quad-rotor unmanned helicopter (QRUH). The two controllers have been widely adopted to act as a single control algorithm in many fields, respectively. However, this paper just displays the useful composite application of the two controllers. The QRUH model can be divided into two subsystems, including a fully actuated subsystem (FAS) and an under-actuated subsystem (UAS). For the FAS, the NRTSMC is used to solve the strong coupling problem, it can guarantee the FAS states converge to the desired equilibrium in a very short time, then the states are treated as time invariants and the UAS gets simplified. For the UAS, the USSMC is utilized to solve the under-actuated problem. The obtained simulation results show the applicability of the composite control when faced with external disturbances.