Virtual test technology study of automatic weapon

Transcription

1 ISSN , England, UK World Journal of Modelling and Simulation Vol. 7 (2011) No. 2, pp Virtual test technology study of automatic weapon Jinfeng Ni 1, Xin Wang 2, Cheng Xu 3 1 College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing , P. R. China 2 School of Computer Science & Technology, Nanjing University of Science and Technology, Nanjing , P. R. China 3 School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing , P. R. China (Received May , Accepted October ) Abstract. In this paper, virtual test technology of automatic weapon is studied based on the dynamic simulation platform-adams. A systemic suit of project for modelling and simulation is provided including the computation of the interior ballistics and random ballistics simulation for the generation of work load, the simulation control method of single fire and repeating fire using parametric design, sensor and script control, as well as the computation of exterior ballistics for the forecast of the firing precision. The implement process is discussed and a simulation instance is presented finally to demonstrate the correctness and efficiency of this study. Keywords: virtual test, modelling and simulation, automatic weapon 1 Introduction In the process of developing a weapon system, experiment is an indispensable step, and need to be done repeatedly [17]. Automatic weapon is a system consisting of many mechanisms such as feed mechanism, firing mechanism and counter-recoil mechanism, etc [15]. The energy of its action is special because it comes from the powder. Traditional weapon design work needs lots of fire tests after the prime prototype weapon has been designed [11].The automatic weapon under design will undergo a series of strict tests. The overall project of the prototype weapon should be modified by the data obtained from the fire tests [3].Thus the design process consumes time and labor. Virtual prototyping has become an advanced design and development technology in the past two decades. From the view of mechanical design, virtual prototype is a computer simulation of a physical product. It can be presented, analyzed, and tested from concerned product lifecycle aspects such as design, manufacturing, service, and recycling as if on a real physical model [2]. The dynamic simulation software MSC.ADAMS is a deputy of virtual prototyping for its powerful analysis function. It has been used widely for dynamic simulation of mechanical products, including automatic weapon [16]. The Weapon Systems Division-Weapons Technology Branch of US Army ARDEC, has completed the dynamic models of M9, M16, M249 and Mk19. The results have been validated with verified data [1]. During the program of LSAT (Lightweight Small Arms Technologies) of US Army ARDEC, modeling and simulation has become a major contributor to the success of this program [12]. Virtual model is established and dynamic simulation is done based on ADAMS [6, 10]. However, some questions in this area still need to be solved to make the simulation process systematical. The object of this paper is to study virtual test technology and it is divided into four parts (the generation of load, the fire control method, the forecast of fire precision and instance of virtual test). Corresponding author. address: nijinf@nuaa.edu.cn. Published by World Academic Press, World Academic Union

2 156 J. Ni & X. Wang & C. Xu: Virtual test technology study of automatic weapon 2 The generation of load 2.1 Module for interior ballistics computation The powder provides energy for the motion of automatic weapon. So it s necessary to obtain average gas pressure and corresponding ballistics parameters such as bullet velocity leaving the muzzle. Programming is the traditional method to solve the basic equations of the interior ballistics [14]. In this paper, the bullet is taken as the study object and the basic equations are analyzed. Dynamic simulation is done on the bullet. It is driven by the force expressed including velocity function and displacement function [8]. During the simulation, the solver of ADAMS will solve the kinematics differential equation of the bullet. The simulation will stop when a sensor monitors that the displacement of the bullet is equal to the length of the tube. Thus the interior ballistics question can be solved using the solver of the dynamic simulation platform. The interior ballistics computing module based on the method above is developed by the tool of the simulation platform. The interior ballistics is solved when the parameters such as the powder figures, the charge structure and the structure of the tube are inputted. The results can be observed from the post-processing module. This work changes the way that the interior ballistics data must be imported by special computing software. It also provides the possibility of achieving random simulation of interior ballistics. 2.2 Random simulation of interior ballistics The interior ballistics process is random actually for the reasons such as the charge and ignition conditions. So the random simulation must be considered for accuracy of the virtual test, which is not considered in previous simulations. According to vast data from the shooting range and statistics verification of the distributing functions, the initial parameters such as the charge quantity, the powder force and the bullet weight obey the normal distributions [4]. Meanwhile they are independent random variables. Monte Carlo method can be used to simulate this random process. From the view of experimental design, the interior ballistics circulation can be viewed as the bullet shooting under different initial parameters. In this paper, the random simulation of interior ballistics is done with the additional module of ADAMS-ADAMS/Insight. ADAMS/Insight is a powerful module. It helps us design sophisticated tests for measuring the performance of mechanical system. It also provides a collection of statistical tools for analyzing the results of tests so that we can understand how to refine and improve our system better. It provides various experimental methods including Monte Carlo method. When the data such as the mean and variance of the design variable are inputted, the design variables matrix which obeys the normal distribution will be created. The random simulation of the interior ballistics can be finished by selecting the parameters such as bullet weight and powder force as the random variables. The interior ballistics computing module mentioned above is used. Fig. 1 shows five chamber pressure curves of some 12.7mm caliber machine gun. 3 Fire control of virtual test The fire modes of weapon include single fire, burst fire and repeating fire. Burst fire belongs to repeating fire virtually. The fire control of virtual test can improve the efficiency of simulation. At the same time it s crucial to achieve repeating fire. In this section, the gas-operation machine gun is taken as the study object and the control problem is studied. 3.1 Single fire control If simulation is done to simulate single fire, the expression of load should be revised manually. Thus the whole virtual test is discontinuous and depends on man-machine interaction. Here the effect of load changes on the prototype is analyzed from the view of parametric analysis. By this method, different parameter values are get from the design variables every time and simulation is executed automatically. It can consider the effect on the prototype when multiple design variables change. WJMS for contribution: submit@wjms.org.uk

3 World Journal of Modelling and Simulation, Vol. 7 (2011) No. 2, pp When single fire simulation is done on the prototype, AKISPL function is used to get values from the corresponding load curves. The expression in function builder is AKISPL (t, 0, SP ID, 0), where t is the simulation time variable and SP ID is the parametric ID variable of load curve. The load curve stored in the model has a unique identifier, that s ID. The IDs of curves are numbered in series. Here we suppose five groups of load curves are considered. The initial Ids are numbered n and m representing the load curves in the tube chamber and gas chamber respectively. Two design variables, DV 1 and DV 2,are created to represent Fig. 1. Five chamber pressure curves Fig. 2. Displacement curves of ten bullets the parametric ID variables of load curves on the tube chamber and gas chamber. The load expressions are AKISPL (t, 0, DV 1, 0) and AKISPL (t, 0, DV 2, 0) respectively. The test times and design matrix are inputted directly to fix the combination of variables. Fig. 4 shows a created design matrix and its denotative IDs. It denotes the simulation is repeated five times. Every time the design variables get different values. Thus single fire control can be finished. 3.2 Repeating fire control The load and cycle differ when weapon fires repeatedly. It s difficult to select another load curve after the finish of a cycle by common method. There are two problems to be solved: the time record and the automatic transformation of load when the automatic mechanisms count-recoil [9]. For the first problem, a sensor can Fig. 3. Dynamic model of weapon Fig. 4. The Design matrix and its denotative IDs be created to record the time. Sensor can be used to monitor if some certain event happens and change the simulation control process if needed. It can also be used to record the value of expression to be evaluated. During the work of automatic weapon, the displacement between the bolt carrier and the tube varies and becomes minimum when the automatic mechanisms count-recoil. So a sensor can be created to monitor if the above displacement reaches some given value and record the time. Its expression is as follows: SENSOR/1, VALUE = XX, LE, FUNCTION = ABS(DX(6, 4))/EVALUATE = time. It expresses that when the absolute displacement value between the markers of the bolt carrier (ID number 6) and the tube (ID number 4) is equal to or less than the given value XX, the simulation time is returned. The function SENVAL (1) is used to get value from the sensor with ID number 1. The expression is revised correspondingly: AKISPL (t-senval (1), 0, SP ID, 0), which will get values from the same load curve and finish repeating fire under the same load. WJMS for subscription: info@wjms.org.uk

4 158 J. Ni & X. Wang & C. Xu: Virtual test technology study of automatic weapon Simulation script control can be used to achieve the automatic load transformation. This method can control the analysis type during simulation, the in-out of analysis results and the lock or unlock of elements such as force and sensor. Script control is discussed here for the weapon action for two cycles. Now supposing the IDs of load curves are n n + 1 in the tube chamber and m m + 11 in the gas chamber, two groups of forces are created and each group has two forces. Their expressions are the same: AKISPL (t-senval (1), 0, SP ID, 0). Another sensor is created with ID number 2 to monitor if the bolt carrier count-recoils. But it doesn t return the value and the simulation will proceed. Its expression is as follows: SENSOR/2, VALUE = XX, RETURN, FUNCTION = ABS(DX(6, 4)). When the simulation starts, the forces of second group are deactivated. When sensor with ID number 2 monitors that the bolt carrier count-recoils, the forces of first group are deactivated and those of second group are activated. The sensor with ID number 2 should be deactivated at the same time to proceed with the simulation. And then the sensor with ID number 2 should be activated to monitor if the bolt carrier count-recoils next time. The script control expressions are listed as follows and this method can finish the control of repeating fire perfectly.! Insert ACF commands here: DEACTIVATE/SFORCE, ID = n + 1m + 1 SIMULATE/DYNAMIC, END = 0.12, DTOUT = 1.0E 002 DEACTIVATE/SENSOR, ID = 2 DEACTIVATE/SFORCE, ID = nm ACTIVATE/SFORCE, ID = n + 1m + 1 SIMULATE/DYNAMIC, END = 0.15, DTOUT = 1.0E 002 ACTIVATE/SENSOR, ID = 2 SIMULATE/DYNAMIC, END = 0.25, DTOUT = 1.0E Module for external ballistics computation The basic problem of exterior ballistics is the movement of bullet leaving the muzzle which is related to fire precision. For large caliber weapon, index of standing target disperses is taken as the evaluation generally. R50 means the radius of circle which takes the disperse center as its center and includes fifty percent of the bullets on the target. During the flight of bullet in air, there are two forces on the bullet: the gravity and the atmosphere resistance [13]. Supposing the bullet mass, initial ballistics coefficient and weather condition are given, the atmosphere resistance is a function of the height and velocity of bullet after analysis [7]. Thus a dynamic simulation can be done on the bullet using the same method of the interior ballistics computation. The exterior ballistics computation module is developed. It can be used to analyze the fire precision if the initial conditions of bullet such as the initial velocity and initial shooting angle are inputted. 5 Instance of virtual test Virtual test is carried through on some 12.7 mm caliber machine gun. Fig. 3 shows its dynamic model. A series of data are obtained. Among those, the movement parameters of automatic mechanisms and firing precision are two important evaluation factors. Fig. 5 and 6 show the velocity curves of automatic mechanisms with five rounds fire from virtual test and from shooting range respectively. The data extracted from the curves are compared and found to be in good coincidence. For example, when the automatic mechanisms recoil and counter-recoil, the maximum velocities are 9.14meters per second and 5.24 meters per second from virtual test, and are 9.07 meters per second and 5.14 meters per second from shooting range. The firing frequencies are 631 rounds per minute and 623 rounds per minute respectively. Fig. 2 shows the longitudinal displacements WJMS for contribution: submit@wjms.org.uk

5 World Journal of Modelling and Simulation, Vol. 7 (2011) No. 2, pp Fig. 5. Velocity of automatic mechanisms from virtual test Fig. 6. Velocity of automatic mechanisms from shooting range vs. transverse displacements of ten rounds bullets on the target 100 meters far from the firing spot. The end of each curve is the bullet location on the target. The R50 is 11.8 cm from the virtual test and 12.4 cm from shooting range. As can be seen, the data from virtual test reflect the characteristics of the weapon exactly. 6 Conclusion In this paper, virtual test technology of automatic weapon is discussed. A systemic suit of project for modelling and simulation is provided including computation of interior and exterior ballistics, consideration of random ballistics and simulation control on the same simulation platform. A virtual test instance is provided. The simulation results are verified by the experimental data from the shooting range. This technology can be used for the design and improvement of automatic weapon with less tests from the shooting range. As for future research, we will further perfect the project with more instances. More over, we will study the interaction between weapon and human body in depth since some researches have been carried on [5]. References [1] M. Daniti, E. Binter. Dynamic simulation of legacy weapon systems. in: NDIA Joint Services Small Arms Systems Annual Symposium, [2] G. Gary. Proceedings of the 2001 asme design technical conference and computers in engineering conference. Pittsburgh, Pennsylvania, [3] Y. Hang, X. Wang, G. Yang. Realization of a virtual experiment system of gun. World Journal of Modelling and Simulation, 2006, 2: [4] Z. Jin. Gun interior ballistics. Beijing Institute of Technology Press, Beijing, (In Chinese) [5] Y. Lee, Y. Choi. A study on the human impulse characteristics of standing shooting posture. Transactions of the Korean Society of Mechanical Engineers, 2004, 4: [6] J. McConville. The creation of a fully functional virtual prototype of an automatic weapon using msc adams. in: MSC.Software Virtual Product Development Conference, [7] J. Ni, C. Xu. Development of exterior ballistics module based on dynamic simulation software. Armament Automation, 2005, 5: (In Chinese) [8] J. Ni, C. Xu. A new method based on dynamic simulation software for the computation of interior ballistics. Computer Simulation, 2005, 9: (In Chinese) [9] J. Ni, C. Xu, Y. Wang. Virtual experiment technology study of weapon automatic mechanisms. Journal of System Simulation, 2006, 6: (In Chinese) [10] K. Phillips, P. Shipley. Lightweight small arms technologies. in: NDIA Joint Services Small Arms Systems Annual Symposium, [11] G. Song. Weapon system engineering. National Defense Industrial Press, Beijing, (In Chinese) [12] K. Spieg, P. Shipley. Lightweight small arms technologies (lsat) program update. in: NDIA Joint Services Small Arms Systems Annual Symposium, [13] Z. Wang, W. Zhou. Theory and method of exterior ballistic design. Science Press, Beijing, (In Chinese) WJMS for subscription: info@wjms.org.uk

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