Analysis Of Ballistic Characteristics And Design Of Control Scheme For Terminal Trajectory Correction Mortar Projectile Equipped With Lateral Impulses

Developing low cost guided mortar projectiles is one of the most important approaches to fundamentally improve the firing accuracy for mortar guns. In this dissertation, a type of terminal trajectory correction mortar projectile is considered as the subject. This projectile is equipped with impulses and is of high accuracy by utilizeing the simple control technology. The problems concerning the ballistic characteristics and control scheme design for this type of projectiles are investigated. The main research work is listed as follows:(1) Study on the dynamic model for the terminal trajectory correction mortar peojectile equipped with lateral impulses. Aming to the mechanical action process of impulse engines and their specified characteristics, the model of transient impulse control force is established by using the rectangular wave function. The model of equivalent average impulse control force is also proposed based on the principle that the impulse is equal. In terms of Newton's second law and the theorem of moment of momentum, two kinds of 6D rigid trajectory mod-els are established. One is using the model of transient impulse control force and the other is utilizing the model of equivalent average impulse control force. The former is used to predict the trajectory and the latter is used to theoretically analyze the angular and translational mo-tion of the mortar projectile under the action of impulse engines.(2) Analysis on ballistic characteristics for the terminal trajectory correction mortar peo-jectile equipped with lateral impulses. According to the dynamic model, the code for predict-ing the trajectory of 6D model is programmed. The variation law of flight trajectory without control and the impact point dispersion under the condition of maximum range are both simu-lated and analyzed. The controlled trajectory characteristics are preliminarily analyzed based on several determined impulse parameters. By simplifying the dynamic equation of motion around the point mass, the equation of angle of attack for mortar projectiles with the action of impulse is established. And the corresponding analytical solution is deduced. The constraint condition of flight stability is proposed which can be used to guide the design of impulse magnitude and axial eccentricity.(3) The effect of impulse parameters on the trajectory. The effect of the impulse pa-rameters (including starting point, single impulse magnitude and the number of impulse en-gines, impulse duration and multi-impulses ignition mode) and the layout on the trajectory are analyzed. Due to the fact that the projectile should be spin axially so as to realize the im-pulse correction, the influence of different equilibrium spin rates on the correction effective- ness is also analyzed. With the consideration of the radial eccentricity of impulse engines, the effect of the change of spin rate caused by the action of impulse on the trajectory is studied. The result indicates that the change of spin rate can largely influence the trajectory correction and flight stability. The change of spin rate caused by the radial eccentricity should be re-duced in the process of engineering research.(4) Modeling and soluting of the optimal design for the terminal trajectory correction mortar peojectile. According to the ballistic characteristics, several optimal design variables are selected and both of the constraint conditions and the objective function are determined. An optimal model for designing the relative parameters is established. A type of modified Particle Swarm Optimization which is suitable for solving the optimal model is proposed. The simulation results show that this modified Particle Swarm Optimization can be used to obtain the optimal solution rapidly and reliably which provides theoretical basis for the pa-rameters design of this type of mortat projectile.(5) Design of terminal trjectiry control scheme under laser semi-active system. By in-troduing and analyzing the composition and principle of the terminal trajectory correction mortar projectile weapon system under the laser semi-active system, the target capture field formula of the mortar projectile equipped with strap-down laser seeker during the terminal trajectory is deduced. A method for predicting the miss distance just using the angle informa-tion provided by the laser seeker is proposed. A Fading-Memory Filter is utilized to reduce the measurement noise of the spin angle data. Based on the previous work, a suitable control scheme is designed. Simulaiton results indicate that the accuracy can be improved by adopt-ing this control scheme which is in accordance with the design purpose.(6) Design of terminal trjectiry control scheme under satellite position. Based on the measurement data (three dimensional positions and velocities) provided by satellite, the state equation and measurement equation are built respectively. By solving the 3D point mass tra-jectory model analytically, an accurate and rapid method for predicting the impact point through estimating the time-to-go is proposed. Based on the work above, a suitable control scheme is designed. Simulation results show that this control scheme can also cut down the impact point dispersion effectively and its accuracy is better than that of the control scheme based on the laser semi-active system under same conditions.