Prescribed performance fuzzy back-stepping control of a flexible air-breathing hypersonic vehicle subject to input constraints

The design of prescribed performance fuzzy back-stepping tracking control for a flexible air-breathing hypersonic vehicle (FAHV) with actuator constraints is discussed. Fuzzy logic systems (FLSs) are applied to approximate the lumped uncertainty of each subsystem of the FAHV model. Every FLS contains only one adaptive parameter that needs to be updated online with a minimal-learning-parameter scheme. The sliding mode differentiator is introduced to obtain the derivatives of the virtual control laws, which avoid the explosion of the differentiation term in traditional back-stepping control. To further improve the control performance, a prescribed performance function characterizing the error convergence rate, maximum overshoot and steady-state error is utilized for the output error transformation. In particular, novel auxiliary systems are explored to handle input saturation. Fuzzy backstep control has obvious advantages in system robustness, control accuracy and highly real-time. Finally, reference trajectory tracking simulations show the effectiveness of the proposed method regarding air-breathing hypersonic vehicle control applications.