Fractional-order non-singular global time-varying terminal sliding mode attitude controller for unpowered reentry vehicle

This paper proposes a fractional-order time-varying nonsingular terminal sliding mode controller for attitude control of unpowered reentry vehicles. The system is able to converge in a finite time with the proposed controller. The introduced time-varying term ensures the global robustness, and the introduced fractional-order term improves the convergence performance of the system. The stability and globality of the system have been proven, and the finite-time convergence has been demonstrated through a new method. The simulation results show that the proposed controller has better control performance compared to existing fractional-order sliding mode attitude controllers and integer-order time-varying terminal sliding mode attitude controllers.