Adaptive Terminal Sliding Mode Attitude Control of Hypersonic Vehicles During Re-entry

Based on the principles of the non-singular terminal sliding mode control(NTSMC),a new control method along with the adaptive filter technology,which can tolerate external disturbances and noises with unknown statistics,is proposed for the attitude control of hypersonic vehicles during re-entry. First,a disturbance compensated module is used as a discontinuous control part of the NTSMC to enhance the performance of the controller due to chattering. Second,a new methodology is proposed based on a real-time estimate of system states by the nonlinear filter and the measurement and process noise covariances. To compare this evolutionary method with classical methods,an optimal filter algorithm is introduced. The results show that,compared with many existing works on the terminal sliding mode control(TSMC),the proposed method exhibits three attractive features:(i) it can avoid singularity problems without any constraints,and provide faster responses by tuning the parameters in the algorithm;(ii)for constant or eventually constant disturbances,zero steady-state error can be achieved when a boundary layer is used to alleviate chattering;(iii)the switching gain is only required to be designed to be greater than the bound of the disturbance. Finally,the effectiveness of the proposed control method is verified by the simulation results of both the numerical and application examples.