Study On Dynamics Modeling And Parameters Identification For Typical Mechanisms Of Guns

As a complex hydromechatronics system,the gun presents a series of physical and chemical phenomena while launching,such as abrasion,ablation,contact impact and complex relative motion.These phenomena are difficult to be accurately described by conventional modeling methods while the system identification theory provides an effective way to solve these problems.Against this background,funded by the national basic research program of China,"Time-varying dynamic research of ×××" and "Transfer law research of ×××",the dynamics modeling and parameters identification for typical mechanisms of guns were researched systematically.The main research contents were indicated as below.The dynamic models of the launching mechanism with two degrees of freedom abstracted from typical mechanisms of guns,such as the throttling valve recoil mechanism,the floating piston type recuperator,the short throttling bar recoil and conterrecoil mechanism,the hydraulic vertical slide breech mechanism,the horizontal slide breech mechanism and the torsion bar equilibrator,were established while the identification for the linear statically determinate structure,the linear statically indeterminate structure,the nonlinear statically determinate structure and the nonlinear statically indeterminate structure were researched systematically.By using the derivatives of the least square method,the stiffness and damping of the linear statically indeterminate launching mechanism under the coloured noise were identified successfully.By using the least square method based on the limited data window concept or the function fitting concept,the damping of the nonlinear statically indeterminate launching mechanism under the coloured noise was identified effectively.And by using the genetic algorithms or the particle swarm optimization algorithms based on the limited data window concept and setting up the search space of the parameters,the dynamics modeling and parameters identification method were proposed which avoided the shortcoming of the least square method,such as the objective function and parameter bound can not be defined.After the motion nonlinear term of this dynamic model was described quantificationally,a conclusion was reached that motion nonlinear term can not be ignored.The operating principle and the measurement error of the laser displacement sensor,the piezoelectric acceleration sensor and the piezoelectric pressure sensor were expounded while the mounting fixtures of the laser displacement sensor and the piezoelectric acceleration sensor were designed.In terms of the experiment equipment,the experiment environment and the practical operation,the measurement error of the high speed photography caused by high speed camera,optics lens,light's transmission,vibration,photographing position,exposure time and coordinate system's alibration was discussed.An image post-processing method was proposed which reduced the measurement error to 0.02mm under 5 lever nature wind condition,while the calibration device of high speed photography was designed to decrease the measurement error caused by the coordinate system's alibration.The dynamics modeling and parameters identification for the large displacement relative motion launching mechanism were researched in depth.A modeling thought that replaceing the fixed constraint boundary conditions with multiple constraint boundary conditions was proposed.The equivalent physical model of the large displacement relative motion launching mechanism experimental device under eccentric drive force was established based on mechanical vibration theory while the actual dynamic response of this experimental device was measured during the dynamic experiment.By choosing the bound reasonably and using the genetic algorithms,the dynamic parameters of this equivalent physical model was identified.And the process of nitrogen driving was simplified as the process of adiabatic expansion.Then by using numerical methods,the mechanical efficiency and the consumed energy of this experimental device were derived.The mapping relation between the engraving force and the strain rate was described as the function relation between the engraving force and the engraving velocity approximatively.By using the gun chamber throat detection device,the actual structure size of a typical gun's chamber throat was obtained.After distinguishing the engraving characteristic of the gun's different parts,the engraving force modeling method was proposed based on dynamic behavior of the material and structure of the chamber throat and the projectile rotating band.By measuring the dynamic parameters of the launching gun,identifying the bound reasonably and using the genetic algorithms,the parameters of this engraving force model in the fifth working condition were identified finally.After being compared with the finite element numerical simulation results,the calculation results of the other four conditions verified this engraving force model.