Finite-time fractional-order nonsingular terminal sliding mode attitude controller for unpowered reentry vehicle

For the convergence time of fractional order sliding mode attitude control for unpowered reentry vehicle is difficult to estimate, a fractional order nonsingular terminal sliding mode attitude controller is proposed in this paper. Combining the advantages of fractional calculus and non-singular terminal sliding mode, the controller has the characteristics of higher control precision, faster convergence rate and convergence in a finite time. The chattering problem is solved by introducing a saturation function into the control signal. The stability of the system is proved by Lyapunov's second method. A new method is adopted to obtain the analytical expression of the state error by solving the fractional differential equation, and then the finite time convergence of the system is proved. The simulation results show that the controller has good robustness and better convergence than the existing fractional order and integer order sliding mode attitude controller.