L₁Adaptive Control For Hypersonic Vehicle In Near Space

The near space is in the height which is between the sky and the outer space,also known as nearly space. Human rarely have activities in this space. Near spacemakes the land、the sea、the sky and the space much more closely linked to eachother, realizing the whole space integration. The unique features in near space makeit a space with high value on research. Also, there is significant contribution in thesafeguard of state security and the world peace.Hypersonic vehicle is the focus among all the near space aircraft, it attractshuman’s attention for the value both in military and commercial. Large range ofchange in velocity and the flying height, complex flying environment and highlyrequirements in the controller are the main features of hypersonic vehicle. As long asincreasing the degree of difficulty in study, all these features provide manyopportunities and challenges. In this paper, in order to meet the features of the nearspace hypersonic vehicle, we start from the modeling of the vehicle, and finallydesign the controller. A new approach to design the controller is applied here tomake the vehicle have fast and robust performance.Firstly, with the help of Lagrange method, an integrated and analytical flexiblemodel is built. In this model, the facts such as the vehicle’s deformation in thehypersonic flow field, the engine and airframe integration are included, which canreflect the system’s coupling, and then reflect the dynamic characteristics of thesystem comprehensively, and lay the foundation for the subsequent controllerdesigning.In order to solve the controller problem of hypersonic vehicle, a new adaptivecontrol method-fast and robust adaptive control, which is also calledL₁adaptivecontrol, is applied in this paper. This method is the improvement of the traditionalmodel reference adaptive control. By adding a low pass filter in the system, thesystem can get rid of the effects by the high frequency characteristics, leading toperfect transient and steady state performance, for the input, output and controlsignals. It is a good control strategy that the fast and robustness of the system canmeet simultaneously.Considering the existing control strategy for the hypersonic vehicle, there are many limitations in these controllers. We useL₁adaptive control to design thecontroller. There are unmodeled dynamic characteristics in the vehicle. Thehypersonic vehicle has highly requirement for the controller’s speed, withoutdisturbing the robustness.L₁adaptive control is capable to solve these problemseffectively. The designed controller has good performance. Therefore we canconclude that the controller is effective.