Development of laser transmission simulation syste

Development of laser transmission simulation system based on virtual prototype

Introduction

correctly simulate the laser transmission process and realize the visual simulation of laser pulse space transmission, which is of great significance to laser research and application. Especially in high-energy laser applications such as inertial confinement fusion (ICF) and laser weapon development, if the physical test is carried out directly, the risk is high and the cost is high. On the contrary, if the virtual prototype model of the laser device can be established and the laser transmission process can be simulated on the virtual prototype, it can not only reduce the test risk, save the cost and shorten the development cycle, but also test the rationality of the device and improve the reliability of the experiment

at present, there are many ICF research devices in the world, among which the National Ignition Facility (NIF) of the United States is the largest. In order to improve the reliability of nif operation and obtain the analysis results after NIF operation in time, Lawrence Livermore National Laboratory (LLNL) of the United States has developed a laser performance operation model (lpom) system to operate the first four channels of laser of nif. Lpom can provide real-time prediction of nif and determine the system parameter settings of all laser emission of NIF, such as initialization power, and has become a key tool for the debugging of the first four laser modules of nif. The research of ICF in China is being carried out gradually, but the corresponding simulation system of device operation has not been established. The comprehensive optical transmission simulation software sg99 developed by China Academy of engineering physics can simulate and calculate the main physical processes of solid-state laser device, such as pulse transmission, release, frequency conversion, etc., but it does not have the functions of laser pulse visualization and simulation. Based on the virtual prototype model of ICF device, a simulation system of laser transmission process is established by using virtual prototype technology, which provides a simulation platform for the operation of laser device

1 development requirements of simulation system

in the actual test, because the laser emission frequency is large and the transmission speed is too fast, it is impossible to study a single laser particle or laser pulse directly, which often needs the help of other auxiliary equipment. At the same time, due to the large number of optical elements, it is not easy for Liu Qi to manage in the actual test. Therefore, this system establishes the virtual prototype model of laser transmission device, and realizes the simulation system of laser transmission process on this basis. The simulation system takes the ICF device as the object, and aims at the visualization of laser transmission process, the dynamic management of optical components and the virtual training of laser emission system. It can visually simulate the laser transmission process, dynamically manage optical components in the laser transmission process, and can be used as a simulation system for virtual training

virtual prototyping technology is a new product development method. It is a comprehensive application technology based on advanced modeling technology, multi domain simulation technology, information management technology, interactive user interface technology and virtual reality technology. Virtual prototype technology can be applied to the whole life cycle of products, and has become an important technical means to test the rationality of product design, optimize product design, shorten product development cycle, and ensure product quality. By establishing the virtual prototype model of the laser device, the "slow" processing of the laser transmission process is realized in the simulation system, that is, by changing the laser pulse frequency and transmission speed, the testers can track and study the laser pulse and even the trajectory of a single laser particle in the simulation system. Through simulation, the operator can have a comprehensive grasp of the safety state of the optical parts during the test, and check the rationality of the device. Through the processing of background calculation software, a comprehensive analysis result can be obtained immediately to provide guidance for subsequent tests. Therefore, the simulation system should have the following functions:

1) three dimensional display function. Provide three-dimensional visualization to show the whole process of laser transmission in the prototype device, and provide motion tracking, viewpoint switching and other functions, so that users can easily observe the operation of simulation

2) human computer interaction function. Provide low-level interfaces for simulation operation, scene driving, simulation control, etc., so that users can control the simulation in real time:

3) information processing function. Provide the query and display of simulation information, and realize the input and output management of simulation information

4) instrument monitoring function. It provides the function of monitoring the key optical safety working state of the optical path in the process of laser transmission. When the instrument is in a dangerous state, it can prompt the user and even automatically temporarily stop the simulation with the exposed surface of the outside world than other materials until the user responds

5) data management function. It provides the function of dynamic management and maintenance of simulation information, model base, input and output information, and provides background support for the operation of simulation system

2 overall structure of simulation system

this system is mainly composed of modeling module, scene driving module, instrument monitoring module, information processing module, database management module and three-dimensional display module. The structure of simulation system is shown in Figure 1

2.1 modeling module

modeling module is divided into physical geometric model and mathematical model modeling. In this system, the modeling of laser transmission characteristics belongs to the modeling of mathematical model. Laser visual modeling and optical path modeling integrate geometric modeling and mathematical modeling technology, and space environment modeling is the modeling of physical geometric model. The construction of physical geometric models mainly relies on commercial CAD software: establish accurate solid models in pro/e, save them as VRML format files, use 3dexplorer to convert VRML format model files into 3DS format, and finally convert them into OpenFlight format model files supported by Vega in Multigen Creator. The model distortion during multiple model transformations is corrected in Multigen Creator

2.2 scene driving module

scene driving module is one of the core modules of wood simulation system and the supporting platform of simulation. The scene driving module includes scene interactive driving, laser movement, particle system update, scene observer observation viewpoint switching, simulation environment setting, observation mode switching, scene special effects, background sound engine, etc

1) scene interaction. Provide human-computer interaction function, modify the simulation step, and be able to operate the components in the scene in real time during simulation, such as adding, deleting, saving optical components, adjusting the component attitude, etc

2) laser motion. The laser beam is simulated by the particle system, and the laser motion is driven by the background database under the control of the simulation clock. In the simulation process, the laser constantly triggers various optical components to obtain the changes of external shape and energy, which are reflected in the simulation scene through the changes of color and shape

3) viewpoint switching. By changing the position of the observer's viewpoint, the best observation angle and observation effect can be obtained in the simulation process

4) switching of observation mode. The system provides several switching modes, such as viewpoint static, viewpoint following, fixed viewpoint, etc

5) simulation environment setting. Initialize the simulation scenario and modify the simulation environment according to the user's habits

6) scene effects. It mainly refers to the special effects of laser track, instrument out of control and laser hitting the target

7) background sound. The main purpose is to better simulate the simulation environment, enhance people's sense of presence, and give people a real feeling

2.3 instrument monitoring module

this module mainly monitors the operation status of the optical instruments in the device during the simulation process. In this system, optical instruments have four working states, namely, safe working state, critical working state, dangerous state and unknown state. For the convenience of monitoring, these four working states are marked as green, yellow, red and purple respectively. The specific working state is determined by relevant judgment standards. In the simulation process, when the laser pulse passes through an optical instrument, the collision detection program will judge whether the two collide. If they collide, the monitoring program will be triggered. The monitoring program then calls the calculation results of the laser transmission simulation software running synchronously in the background, analyzes and judges the current working state of the optical instrument, marks it with the corresponding color, and outputs relevant information at the same time

2.4 information processing module

the information processing module includes two parts: information output and information query. The information output is mainly to output the working state of simulation optical elements, energy of key instruments, light intensity distribution and other information in the form of words or pictures. The query part can query the simulation information of key optical instruments in real time, such as current luminous flux, maximum flux curve, etc. The output and query of simulation information are completed by calling the background database, optical computing software sg99 and MATLAB. Sg99 simulates and calculates the physical characteristics related to laser pulse transmission and the luminous flux of optical instruments, and then transfers the relevant calculation data to the drawing program, which calls matlab to draw the maximum luminous flux curve of key instruments, and then displays it in the graphic information output area of the simulation software interface

3 key technology for the construction of simulation system

the main function of this system is to simulate the laser transmission process and monitor the state of optical components in the transmission process. A series of key technologies such as optical path interactive design, laser equivalent processing, transmission process visualization and so on should be used in the construction of the simulation system

3.1 laser optical path interaction design

in the simulation process, in order to obtain the real-time processing effect, it is necessary to obtain the current state of the laser in real time, the energy change and morphological change of the laser beam when passing through the optical components, the damage caused by the laser beam to the optical components, and the impact on the laser transmission results when changing the attitude, quantity and placement position of the optical components in real time

the system establishes the following set of data structures, which are used to dynamically add, delete, save and adjust the posture of the simulation model:

data structures are associated with ODBC database. The input function is the dynamic reading of optical components, the setting of attitude parameters, morphological parameters and other attribute data. The output function is mainly to output graphics, simulation data and other information, which is completed by the simulation engine calling the background database and the calculation software sg99 and MATLAB

3.2 laser equivalent processing technology

in the actual laser transmission process, it is usually impossible to track and observe it with the naked eye, and can only be observed with the help of instruments. In order to reproduce the transmission track and physical characteristics of the laser in the simulation scene, the following technologies are used in this system to treat the laser equivalently

3.2.1 equivalent processing technology of laser morphology

in this system, the visualization of laser morphology is a very important aspect. The visualization of laser morphology mainly refers to how to use geometric models in the simulation scene to simulate the trajectory and motion law of laser

the spatial transmission process of laser beam can be regarded as a discrete driving event, laser particles can be regarded as a flowing entity, and optical instruments are equivalent to fixed entities, so the laser beam can be regarded as a solid flow of these entities moving according to a certain law. Therefore, the visual simulation of laser transmission process can be regarded as process oriented discrete event simulation, that is, entity flow simulation. In this system, the particle system is used to simulate the laser and its spatial transmission process. Particle system is mainly used to simulate