Attitude control for hypersonic vehicle based on SMDO-TLC

In consideration of actuator input constraints, a novel attitude control method driven by sliding-mode disturbance observer was presented for supersonic vehicle which is fast time-varying, strong coupling combining with parameter non-deterministic. Firstly, via introducing the concept of second-order linear differentiator (SOLD), it was indicated that peaking phenomenon caused by a combination of first-order lag and pseudo differentiator, which is similar with SOLD, would emerge during the transient profile of differentiation of the nominal command in the existing trajectory linearization control (TLC). Nonlinear tracking differentiator (TD) was used to produce the nominal command and its derivative, saturation of actuator during transition time was solved. Secondly, second order sliding-mode disturbance observer (SOSMDO) based on integration of sign function was designed to reconstruct compound disturbances in the loops of attitude and angular rate respectively, and then compensation control law was proposed to realize attitude control. Simulation results show that the technique proposed can overcome the impact of large-scale perturbations of interference and aerodynamics parameters, meanwhile good dynamic character and steady quality was achieved, the hypersonic vehicle control demand of fast time-varying, high precision and strong robustness can be satisfied.