Investigation On Ballistic Characteristics And Control Mechanism For A Type Of Air-defense Guided Projectiles Equipped With A Pair Of Canards

Developing guided projectiles is one of the most important approaches to fundamentally improve the firing accuracy for anti-aircraft guns. In this dissertation, a type of anti-aircraft guided projectile equipped with a pair of canard surfaces is considered as the subject. Focusing on some theoretical and technical problems encountered during the research process, the exterior ballistic characteristics and control mechanism of this type of guided projectile are investigated, which are included as follows:1. Based on the trajectory model of conventional fin-stabilized projectiles, both of the transient 6 degree of freedom rigid body trajectory model and average 6 degree of freedom rigid body trajectory model are established under the action of canard control. According to the requirements of different applications, the 6 degree of freedom rigid body trajectory model is simplified from different points of views. Subsequently, an order-reduced linearized rigid body trajectory model, an extended point-mass trajectory model and a controlled point-mass trajectory model considering lateral overload are obtained.2. Aiming to the aerodynamic model of "canard-body-fin" configuration, a set of aerodynamic engineering algorithms is determined, which is of good generality, little time-consuming and relatively high precision. The effect of the aspect ratio and position of canard surface and tail fin on the static stability of projectiles is analyzed. The aspect ratio and position of tail fin have significant influence on the static stability of guided projectiles. The effect of free stream conditions for different altitude on the aerodynamic coefficients is also discussed. The result shows that the drag coefficient varies obviously with respect to the altitude. Within the range of altitude from 0 km-20 km, the variation of drag coefficient is about 15%-30% at different Mach numbers.3. Under the action of canard control, the equivalence between transient model and average model is, to some extent, proved by flight simulation. And then the effect of variation of muzzle velocity, elevation angle, phase angle and width modulation angle of control signal on the controlled trajectory is discussed. The ballistic distribution induced by stochastic errors of control signal is also analyzed. Taking the control item as the transient perturbation, the initial condition of uncontrolled angular motion equation is deduced, base on which the effect of aerodynamic shape parameters of canards, spin rate, effective slant range and phase angle of control signal on the transient process of angle of attack motion is studied. On the other hand, the controlled angular motion equation is established taking the control item as long-playing perturbation. The Lyapunov's direct method is adopted to deduce the dynamic stability condition of the guided projectiles. By virtue of solving the angular motion equation analytically, the effect of the deflection angle, the deflection angular speed, the arm of control force and the moment of inertial on the characteristics of angle of attack is analyzed.4. By analyzing the characteristics of angle of attack, a design method of spin rate based on controlling the angle of attack is proposed. According to the swerving motion theory of point-mass trajectory, an estimation formula for normal induced velocity with relatively high precision is also deduced, which can be used in the optimization of trajectory correction capability. A complex optimum method of aerodynamic shape and controlled trajectory is proposed and the corresponding optimum model is also established. The feasibility and effectiveness of this approach is verified through an example.5. Based on the extended point-mass trajectory model and the measured position and velocity data, both of the system state equation and measurement equation are established regarding the stochastic cross-wind as the process noise. The trajectory parameters are estimated by using extend Kalman filter (EKF) and linearized Kalman filter (LKF) respectively, on the basis of which a hybrid Kalman filter is proposed. The theoretical analysis and simulation results indicate that the calculation amount online is reduced significantly and the estimation precision of flight state is also improved. Based on the process noise control, a scheme of estimation of flight state is proposed to reduce or alleviate the negative influence of the bias between system theoretical model and real world.6. Under some assumed circumstances, two types of simple control modes based on determining the starting control point and stopping control point respectively are proposed. The effect of different trajectory correction requirements and elevation angles on the applications of two modes is analyzed by simulations. The results show that both of the two modes are of satisfied performance. The trajectory prediction (TP) and modified proportional navigation (MPN) guidance are applied to the anti-aircraft guided projectile. The theoretical analysis and simulation results indicate that good effect of trajectory control is obtained by using both TP and MPN, through which, to some extent, the feasibility and effectiveness is verified. Under the conditions of different downranges and trajectory correction quantitities, the variation law of control error of TP is similar to that of MPN. Compared with TP, the MPN is of relatively better control accuracy.7. To persuit the optimal control, the lateral overload of the anti-aircraft guided projectile during its control flight phase is optimized. Based on developing a reasonable controlled trajectory model and taking the least energy cost as the performance index, an optimal control model on the effective trajectory of anti-aircraft guided projectiles is established with the constraint of overload. This model is firstly converted to the TPBVP by using the Pontryagin's minimum principle. And then the TPBVP is solved numerically by the boundary value shooting method. The results indicate that the optimal control theory can be applied to the optimization of the overload of guided projectiles effectively.