This paper focuses on the design of nonlinear robust controller and disturbance observer for the longitudinal dynamics of a hypersonic vehicle （HSV） in the presence of parameter uncertainties and external disturbances. First, by combining terminal sliding mode control （TSMC） and second-order sliding mode control （SOSMC） approach, the second- order terminal sliding control （2TSMC） is proposed for the velocity and altitude tracking control of the HSV. The 2TSMC possesses the merits of both TSMC and SOSMC, which can provide fast convergence, continuous control law and high- tracking precision. Then, in order to increase the robustness of the control system and improve the control performance, the sliding mode disturbance observer （SMDO） is presented. The closed-loop stability is analyzed using the Lyapunov technique. Finally, simulation results illustrate the effectiveness of the proposed method, as well as the improved overall performance over the conventional sliding mode control （SMC）.
When the light wave propagates through the hypersonic flow field, the aero-optic distortion happens. It is necessary to recognize the vortex structure for studying the light propagation model. A new vortex structure recognition method is proposed in this paper. Firstly, the refractive index field, which is transformed from the turbulent density field, is changed to gray scale images with a- bundant texture information equivalently. Then, wavelet transform is performed to decompose these images and the entropy values of the wavelet base coefficients are calculated. Comparing the entropy value to a given threshold, the modules with lower entropy are considered to be the large-scale vortex modules while those with higher entropy are small-scale vortex modules. The computer simulation results show that the proposed method is valid to recognize the vortex structures. This paper provides basis for investigation on the optics propagation model in terms of the turbulence vortex structures.
By referring to adaptive control method,the consensus tracking problem for multi-vehicle system with a well-in...
JingMei ZHANG,Li WANG,Jianwei XIA are with School of Automation,Southeast University,Nanjing,210096 China.ChangYin SUN is with the school of Automation,Southeast University.He is currently a full time Professor.His major research fields are nonlinear control,intelligence control and pattern recognition.
