Study On The Dynamic Characteristics And Motion Stability Of The Hedgehopping Smart Munition

The the smart hedgehopping ammunition(SHA)directly uses the mother missile as a steady-state scanning platform.Using the characteristics of the ballistic plane under a small shooting angle,it flies and rotates at a high speed to detect and damage the target.Due to the new steady-state scanning mechanism,the flying fly smart missile has put forward many new demands on its aerodynamic performance.Besides,its motion characteristics and steady-state scanning characteristics are also significantly different from those of traditional smart bullets.Thus,in this paper,the theoretical analysis,numerical simulation and experimental research are applied to study the aerodynamic characteristics,motion characteristics and steady-state seanning characteristics of the SHA,and the corresponding theoretical model,research methods and conclusions are illustrated.The research results can provide reference for analysis of aerodynamic characteristics of missiles,aerodynamic shape optimization design,motion stability analysis,and analysis of hit probability and damage effectiveness.The main contribution of this work include the following aspects:(1)According to the demand of high speed and low drag coefficient for SHA,the multi-objective optimization is proposed for increasing rotation and drag reduction of SHA.By analyzing the forces of different tail structures in the roll state,an analytical relationship between the balance speed of the bullet and the geometric parameters of the tail is established.The steady-state CFD(Computational Fluid Dynamics)simulation method based on rotating coordinate system was used to verify the theoretical analysis results,and comparisons are demonstrated in roll performance of different tail structures.Furthermore,an example using the new twisted empennage structure is presented,a multi-objective optimization method for the aerodynamic shape of missiles and missiles based on orthogonal simulation experiments,stepwise regression analysis,and multi-objective genetic algorithm was proposed,and the fly-flying smart missiles were developed.The multi-objective optimization is proposed for increasing rotation and drag reduction of SHA,and the Preto multi-objective optimization scheme for the fin structure is obtained.The results show that the proposed optimal design method has a good ability for optimizing,and can effectively deal with the multi-objective optimization problem of the aerodynamic shape for missiles and rockets that have conflicting relations.(2)In order to investigate aerodynamic characteristics of the hedgehopping projectile under condition of high-speed rolling,the contrast experimental investigations using wind tunnel tests are implemented first at static and freely rolling.A balanced speed measurement method suitable for small-scale experimental models was proposed.The experimental data of balanced speed and various aerodynamic parameters under subsonic,transonic and supersonic conditions were obtained,and the influence of such a high-speed rolling state on aerodynamic parameters was quantitatively analyze.Main results indicate the follows:all the aerodynamic parameters of the SHA have certain nonlinear characteristics;Due to the reduced airfoil pressure coefficient and the enhanced Magnus effect,the aerodynamic characteristics at states of high-speed rolling are distinctly different from the static case,besides the larger yawing moment,the lower pitching monent and forward shift of pressure center are also accompanied,both which are adverse to the flight stability of empennage projectile.(3)According to the fact that the pithing motion coupling with the rolling and coning motion during the hedgehopping smart munition flight,the study on the characteristics of projectile's Coupled Motion dynamic derivatives was carried out.Due to the coupled motion simulation is relatively difficult,In this paper a method based on the Euler rotation theorem and spherical sliding meshing technique has been propose to deal with simulation of the complex angular motion,where in details,through applying the Rodriguez transformation matrix,the modification value of the projectile's angular velocity at each time step is interpolated out and further allocated to the sliding meshing zone.Based on the method,the influences on pitching combination dynamic derivatives and lift coefficient made by the projectile's rolling and coning motion are analyzed after solving and identifying the unsteady aerodynamic parameters.The results indicate that:in the solving process for the unsteady flow field,the proposed method can eliminate the accumulative errors in calculation of attitude angles effectively,realizing the accurate simulation under arbitrary given angular motion;When the projectile does the coupling angle movement,the hysteresis loop of aerodynamic loads are obviously oscillated and offset,and the identification results of pitching combination dynamic derivatives and lift coefficient change significantly with the increase of roll frequency and taper frequency.(4)Aiming at the characteristics of high-speed rotating tail-wing ammunition,the theoretical research on nonlinear angular motion characteristics and coning motion characteristics is carried out.Based on the aerodynamic performance researches of the hedgehopping smart munition,the hedgehopping dexterous projectile dynamics equation and nonlinear angular motion equation were established.Combined with the improved linear method,amplitude plane method and the singularity theory,the angle equation was analyzed.Addressing the shortcomings of existing theory methods,by means of the Taylor expansion of amplitude plane equation,the comprehensive and in-depth discussions on the non-zero singularity's existence and stability of amplitude plane equation were conducted under different parameter selections.The limit coning motion forming conditions,amplitude and frequency of the rotation projectile were obtained with clear analytic relations.Finally,the theoretical model was verified by combining the results of the aerodynamic parameters of the hedgehopping dexterous projectile.The results show that the stable limit cone motion form criterion in this paper is more comprehensive and clearer than that of the existing theory results.Based on the obtained criterion,the performance of limit the coning motion can be analyzed and estimated conveniently and effectively.(5)Based on the nonlinear motion and ballistic characteristics of the gliding smart ammunition,the modeling and analysis of scanning characteristics of the SHA under the coning motion are carried out.As the SHA will probably form the steady extreme conical motion under the effect of nonlinear aerodynamic force and moment,we make a coordinate transformation of its kinematic equation based on the research results of aerodynamic characteristics and nonlinear angular motion characteristics.Scanning equation of steady state and scanning equation of ground gap are deduced when the SHA in a condition of extreme conical motion.The effect of amplitude and frequency of extreme conical motion as well as aerodynamic parameter on ground gap scanning is analyzed.The results indicates that,the scanning trace formed by the SHA will not be uniform and it will change between sparse and dense as the extreme conical motion existing,compared to the extreme conical motion inexisting.It could make the scanning gap larger than the characteristic length of target in some regions as it meets the requirement of detecting target at first,consequently,the target will be missed by scanning.And it must be avoided when the SHA is designed.