Research On Dynamics Analysis And Control Methods Of Trajectory Correction Projectiles

In this paper, an effective trajectory correction scheme is proposed for a fixed-canard dual-spin projectile based on the analyses of its dynamic characteristics. Then, the influence of system parameters on the stability of the fixed-canard dual-spin projectile is well analyzed, based on the application of the bifurcation theory, to obtain the dynamic stability criterion and design the proposed trajectory correction scheme which are appropriate for the fixed-canard dual-spin projectile, and provide a solid foundation for the optimization of its structural and aerodynamic parameters.According to the characteristics of the pneumatic asymmetry, this paper establishes the nonlinear dynamic models for the fixed-canard dual-spin projectile, which are reduced to the inhomogeneous angular motion models. The angular motion characteristics of the fixed-canard dual-spin projectile are analyzed with the fixed setting angle or periodic rotation of the trajectory correction component respectively based on the reduced models. If the revolving speed of the trajectory correction fuze is fixed, the angular motion characteristics are found to be affected by the amplitude and the direction of the rotation and unreasonable revolving speed may lead to the instability of the angular motion on account of the resonance of the projectile body. And if the trajectory correction fuze is equipped with a fixed setting angle, a dynamic balance angle of attack, which is approximately proportional to the setting angle of the canard, can be calculated.The flight stability criterion for the fixed-canard dual-spin projectile is investigated and the gyroscopic stability criterion, the dynamic stability criterion and the tracking stability criterion of the fixed-canard dual-spin projectile are deduced respectively in this paper. On the basis of simulation tests in the light of the characteristic of its dual-spin, the influence of the rotational inertias and revolving speeds of the former and the latter bodies on its flight stability is analyzed to provide a solid foundation for the design of revolving speeds of the former and the latter bodies and the initial launching angle of the fixed-canard dual-spin projectile.On the basis of the angular motion characteristics and the stability criterion of the fixed-canard dual-spin projectile, the capacity of its trajectory correction is studied, and a trajectory correction scheme, in which the amplitude of the average control force can be regulated flexibly, is proposed in consideration of the disadvantages of existing trajectory correction approaches. Hereby, the guidance and control system are designed for the fixed-canard dual-spin projectile innovatively. In light of the characteristic of the high speed rotation of the fixed-canard dual-spin projectile and the analyses of the characteristic of its trajectory, the relationship between the resultant normal force and the deflection angle of the fixed-canard is explicitly pointed out. Then a novel trajectory correction scheme, in which the average normal force whose amplitude can be adjusted feasibly can be obtained if the trajectory correction component rotates in different revolving speeds or various amplitudes, is proposed on the basis of the concept of the period average. And the effectiveness of the proposed trajectory correction scheme is demonstrated by 6-DOF ballistic simulations. Compared with existing trajectory correction approaches with fixed trajectory correction components, this novel trajectory correction scheme can control the amplitude and the direction of the average normal force continuously to realize the guidance and control of the fixed-canard dual-spin projectile and the elimination of the trajectory deviation so that the attack precision of the projectile is improved effectively.In the end, in consideration of the insufficient maneuverability of the fixed-canard dual-spin projectile, how the equilibrium varies with the setting angles of canards in its flight is derived from a numerical approach on the basis of its nonlinear dynamic models, and some detail bifurcation graphs of the system are shown in this paper from which it can be seen that the system has three sets of stable equilibrium points, one of which is ideally feasible for the system. Thereby, the amplitude of the setting angles of canards is required to be limited in a proper range so that the stability of the fixed-canard dual-spin projectile in its flight can be guaranteed. Furthermore, a series of bifurcation graphs with different system parameters for the fixed-canard dual-spin projectile are shown in this paper respectively on the conditions that the setting angle of the trajectory correction component is fixed or periodic rotation of the trajectory correction component spins periodically. And the influence of flight parameters, structure parameters and aerodynamic parameters of the fixed-canard dual-spin projectile on the bifurcation characteristics of the dynamics system is summarized, aimed at providing a firm foundation for the design of optimization of the systems parameters.