Research Of Atitude Control System Of Micro Launch Vehicle With Flywheel Stystem And Thrust Vectoring Nozzle

Cost-effective micro launch vehicle will be a significant launch carrier for meeting increasing demand of launching micro-satellites and developing operationally responsive space ability.The onboard inertial measurement unit installed in the Cost-effective micro launch vehicle has reletivelly lower accurancy.Besides the complex atmospheric environmental parameter variation and fierce environmental load,and the intrincis parameter perturbation,the launch vehicle would possess larger position diviaiton and attitude diviaton against the nominal trajectory after finishing its first or second grade flight.Therefore,trajectory maneuver and attitude adjustment accomplished by upper stage would be the crucial for cost-effective micro launch vehicle to convey the launch load to the orbit,which largely depends on the prefermance of the navigation,guidance and control(GNC)system of the upper stage.For this reason,this dissertation focuses on the guidance and control system design of an upper stage of Cost-effective micro launch vehicle derived jointly by flywheel stystem and thrust vectoring nozzle.The main contents and results of this research are as follows:Sending the launch load to pre-selected orbit has to make a restricton for the final flight position and velcotiy of the upper stage,which essentially is a two point boundary value problem with end-point constraints.Taking the additional index such as minimal fuel consumption into consideration,the optimal control theory is in the centre of the possible solution to this problem.However,the answer of the maximum principle for this complex nonlinear problem seems be a time consumer,and the convergence of the simplified shooting method and finite difference method are both sensitive to the initial value,which make it unfeasible for engineering application.In view of this situation,an optimal guidance model for upper stage entering orbit,whose terminal constraint is simplified for its influence for the convergence speed and outcome accurancy,and symplectic-preserving numberical method is presented in this dissertation.This method converts the optimal control problem to Hamiltionian two-point boundary value problem.Taking the advantage of Hamiltonian function,this method could afford higher accurancy calculation outcome with fast convergence speed that meets the requirement for online calculation.Both the symplectic-preserving numberical method and shooting method are applied in the simulation,whose result shows the former could offer more reliable calculaton outcome compared the later.The research object in this dissertation adopts flywheel system as the rotation channel actuator for sable control.The flywheel system is a kind of momentum exchange actuator,whose inner friction nonlinear,retardation effect at low speed,electrical element parameter perturbation and fluctuation of inner bus voltage would result in the deviation of the output torque and desired torque at both the transient and stable condition.And the present control method for the flywheel system cannot achive the high accurancy and disturbance rejection at the same time,which cannot guarantee the upper stage rotation stable and entering orbit exactly.Aim at this,the disturbances are analysised and classified to obtain a simpler format,the new output variable is defined according to the requirement of the flywheel system,and a novel sliding controller based on disturbance observer is presented in this dissertation.The performance comparsion silumation result exhibits that the new controller possesses improved performance against tradtionary sliding controller in terms of miamatched disturbance rejection and smooth control input command.The two-degree thrust vectoring nozzle is employed in the upper stage as the pitch and yaw channel actuators.As for the larger position deviation and attitude deviation after basic stage separation,the upper stage has to maneuver in a big angle,which would resuls in attitude coupling.Therefore,the contradional three-channel decoupling control method is no longer applicable.Also,the upper stage intrincis parameter perturbation would produce adverse effect on attitude accuracy.Hence,multivariable decoupling control method based on active disturbance rejection control and terminal sliding control method based on nonlinear dynamic inverse for nonlinear attitude kinetic model are presented.Under the both controller the control output can accurately track the desired command.The comparison simulations in the presence of model parameter perturbation,external disturbance and measurement noise demonstrate the presented method is valid and robust.In order to further testify the validation of the guidance and control system of cost-effective micro launch vehicle,four hundred monte-carlo numerical simulations for gudiacne and control system with the structural deviation,assignment error and measurement error is conducted.Its result shows the presented guidance and control system could guarantee the upper stage entering orbit exactly with the presence of significant initial deviation,and the guidance and control system posseesss strong robustness against the external disturbance and measurement noise.This dissertation systematically investigates the cost-effective micro launch vehicle upper stage guidance and control control system design method.The result of research could offer theoretical support and engineering application for the guidance and control system design of upper stage,and also possesses great reference value and research significance for optimal control theory application for guidance system design and robust attitude control system design.