Study of Moving Mass Control and Predictive Guidance with Applications to Vehicle Reentry Maneuver
|School||Harbin Institute of Technology|
|Keywords||moving mass control hypersonic vehicle kinetic characteristic predictive guidance flight control computer-based simulation|
Moving mass control (MMC) technology and entry predictive guidance (PG) method are developed for the hypersonic reentry vehicle (HRV) in this thesis. MMC technology and PG method provide new ideas for maneuver penetration and precision attack of ballistic missile. However, there are still many problems needed to be resolved in practice. This thesis focuses on some aspects of these problems.An eight degree of freedom (8-DOF) dynamics equations is derived firstly based on the momentum theorem and the moment of momentum theorem for vehicle with combination control mode of differential aileron and double moving point masses. The dynamics equations are composed of a three dimensional (3-D) translational dynamics equation of the system center of mass, a 3-D rotational dynamics equation about the system center of mass and a 2-D translational dynamics equation of the moving point masses.Then, the kinetic characteristic of MMC vehicle is analyzed carefully. The analysis lays foundation for the following work of three aspects. Above all, the relationship between the mass movement and attitude motion of the vehicle is established. The lateral force generation mechanism and the existence condition of the trim angle of attack (AOA) are analyzed also. Meanwhile, the impact of the mass parameters including mass ratio, lateral offset and axial position on the trim AOA and the divert capability with different trim angle of attack are discussed. Based on the analysis results mentioned in the work of the first aspect, the impact of inertial force and inertial moment caused by the mass movement on the trajectory change and attitude motion of vehicle are studied. The impact of the roll angular velocity and lateral overload of vehicle body on mass movement is also discussed in detail. Besides, the effect of mass parameters and servo-controlled parameters on the inertial moment is investigated. At last, the kinetic characteristics of the roll subsystem are discussed theoretically, and the mechanism for the induced roll movement is explored. The analytical calculation and quantity assessment are also performed for the aero roll moment which plays a critical role in change of the roll movement. What is more, in order to avoid the disadvantage of present PG with large quantities of calculation. A new entry PG law is designed in this thesis. The idea originates from the facts that the lateral force on the reentry body is perpendicular to the direction of velocity at any time. If the lateral force acted for a micro time in a certain direction at the beginning, it would cause a velocity increment in this direction inevitably and the velocity increment would lead to an infinitesimal displacement at the end of the predictive trajectory, which is called virtual displacement (VD). This is exactly similar to the principle of VD in analytical mechanics. During the guidance procedure, the VD corresponding to the direction of lateral force required by the guidance should be along the error vector at the end of the trajectory. According to the above facts, the 3-D closed-form solutions of the zero-lift reentry trajectory equations are derived. The optimal direction of the lateral force for guidance is searched by the Newton iteration method. According to instantaneous equilibrium assumption, the command is generated according to the optimal lateral force direction. At last, the performance of guidance is analyzed by numerical simulation.Last but not least, control model is derived due to the system dynamics analysis. The attitude tracking control system is divided into attitude tracking control loop and angular velocity tracking control loop via two-time scale method. The robust sliding mode controllers are designed for both two loops and an adaptive term is introduced to compensate the effect caused by parameter uncertainties. Meanwhile, the complete mass dynamics model is taken into account in the attitude dynamics model and a sliding mode controller is designed for the mass position servo control system with the aid of feedback linearization. As regard the roll stabilization control system, bang-bang controller is adopted. The switching line for the double integrator system is determined according to the time performance index, and the chattering is fixed with the combination of double switching line bang-bang control method and continuous control method in the neighborhood of the origin. The simulation results indicate that the control system with the controllers designed herein can track angle command and position command fast, effectively and stably. The simulation results also show the following facts: the drive force of the moving mass is in the proper range, the roll angle converges to zero fast and rapidly, the chattering is suppressed effectively.The research in this thesis covers dynamics, guidance and control topics of HRV with moving masses. I hope that these researchs could provide a reference for maneuver penetration and precision attack of ballistic missile.