Research On Control System Of Reusable Boosted Vehicle Based On Robust Gain Scheduling

The reusability of space vehicle plays a very important role in reducing transport costs, increasing carrying capacity and launch frequency. Reusable Boosted Vehicle(RBV) is one of reusable space vehicle which is a power return and glide path landing vehicle. The characteristics, such as nonlinearity, time-varying, dynamical coupling, aero-dynamical coupling, inertial coupling, Super maneuver with high attack angle existing in RBV model make the design of control system very difficult. This thesis researched the attitude control system of RBV in reentry phase, using a method, which integrates theμ-synthesis in robust control theory with the gain schedule control method, to design the controller. On the one hand, robust control method can ensure the stability with the existing of uncertainties; on the other hand, gain schedule control method can reduce the conservation resulting from the robust control method. The main research works of this thesis are described as follows:1. According to the characteristics of RBV, first, the nonlinear motion model of RBV in reentry phase is established. On this basis, the nonlinear model is linearized using the theory of small perturbation linearization.2. Design of robust gain scheduling controller.According to the four steps of traditional gain schedule method, first, choose appropriate scheduling variable. Second, choose proper operating points. Third, design the controllers corresponding to the operating points usingμ-synthesis method. The three channels are considered to be independent with each other. The aero-dynamical coupling and inertial coupling are regarded as perturbation, included in the range of uncertainty. Considering the measurement noises and the external disturbances, these factors are uniformly described by uncertainty block. In order to transform the RBV control system into standardμ-synthesis configuration, the weighting functions are used to normalize the uncertainties and external input signals and output signals. When the above steps finish, the controllers corresponding to the operating points can be designed by D-K iterative method. Putting the controller into the closed loop system, the robust stability and robust performance can be analyzed. Because the order of controller designed by D-K iterative method is very high, for the feasibility of engineering application, this thesis uses balanced truncation method to lower the order of controller. Final step, get the controllers corresponding to the area between the operating points by interpolation. Since the structure and order of robust controller are uncertain, this thesis use a method named control signal interpolation to interpolate and then the global nonlinear controller of RBV is obtained.3. At last, the effectiveness and feasibility of the controller are verified by nonlinear 6-DOF mathematical simulation.