On-line Trajectory Generation And Attitude Control System Reconstruction For Launch Vehicle With Thrust Decline

To satisfy the demand of military satellite reconnaissance,space surveillance,space flight,deep space exploration and commercial launching,every country in the world tries their best to boost the level of spacerockt technology.In order to improve the transport capacity and the attitude control capacity of launch vehicle,the number of rocket engine of the new type of launch vehicle increases obviously.Although increased number of rocket engines increases the odds of failure,it also enhances the capacity of control system.This paper studies the dynamic model,fault simulation analysis,online trajectory generation and fault-tolerant control when the thrust of launch vehicle declines.The nonlinear dynamic model for rigid body of the rocket with six degrees of freedom is established under the circumstance of the thrust decline.The nonlinear dynamic model for rigid body with three degrees of freedom is established for online trajectory generation.A general attitude dynamic model of strap-on launch vehicle is established.The thrust decline of launch vehicle leads to the deviation of the mass center is considered.The effect of thrust decline of engine on the flight path and the control system is analyzed.Based on the loss of thrust,a modularized simulation method is developed for launch vehicle by applying the Matlab/Simulink.Subsequently,influences of the failure of booster engine and core engine are investigated by failure simulation.The flight path is reconstructed under the circumstance of the engine thrust decline fault by applying Gauss pseudopectral.Because of weaker controlling force,the rocket can not fly in accordance with the planned trajectory any more.So it is necessary to generate a new trajectory by applying Gauss pseudopectral.An optimal control allocation method,fixed-point method(FXP),which is based on pseudo-inverse method,is proposed.The simulation results demonstrate that the method is simple and effective.