Model and Simulation of Vehicle Based on Modelica Language

Abstract: Multi-field unified model based on Modelica language is the most important developing direction of multi-field model and co-simulation today. Firstly the aim of this paper is virtual flight simulation, and the universality of model need to be considered with the blocking methods. Then model of aerospace vehicle is divided, and the relationship between parameters of model is got, and model simulative bank of aerospace vehicle is based on Modelica language. At last, flight simulative model of aerospace vehicle is build on the model bank, however guidance and control of aerospace vehicle is carried out, which is used for availability of model bank.


Introduction
Co-simulation and unified model need to be solved for multi-field physical system, Modelica language is brought out, which is relate to the equation statement model, and is base on method of induction and summary for prior multi-language of model.Modelica language is adapt to the cumulative, repeatability and rebuild of acknowledge, and physical laws of different field subsystem are described with mathematics language of Modelica.According to topology relation of physical system, with model construct and integration of multi-field based on the mechanism of connected components of language ingrown, system simulation can be run through solving the differentialalgebraic equation.So model method of Modelica language being adopted in this paper, model and simulation of aerospace vehicles are researched, and model bank is construct, and flight simulation of aerospace vehicles is realized.

Flight simulation model 2.1 Layered structure of flight simulative model
In order to finish flight simulation, according to model method and blocking method of Modelica language, model parameters should be divided from main parameters of system, and universality and materiality of model should be considered.Then model parameters are regarded as initial input data, which is no relation to imulation.Layered structure of flight simulative models can be divided and showed in Figure 1.

The relation between parameters of flight simulative model
In order to finish flight simulation, according to output relation of parameters of different models, divided submodels should be assembled under the condition of multi-field model and co-simulation, and flight simulative system is completed.The relation between different models is showed as following Figure 2. Within Figure 2, initial model is the entrance of simulation, after simulation running, three dash line related with initial condition should be canceled.( From mathematical model, the process of modeling is showed as following Figure 3 with Modelica language, and the definition of equations with Modelica language is noted as Figure 4. Form two figures, model can be built by initial equations, which possesses stronger readability and higher efficiency than other models.

Building the simulative system of aerospace vehicles
The simulative system of aerospace vehicles include many subsystem, and the relationship between different subsystem need be hold together by data transferring.Subsystems catch their required data to simulate, and send out required data for other subsystems.According to management of layered structure of flight simulative model, simulative system of aerospace vehicles is showed as following Figure 5.

Simulative analysis
The whole trajectory of aerospace vehicles can be simulated with simulative system of aerospace vehicles.Initial conditions can be set as Figure 6, and results about angle of pitch, Ma, flight height, and deflections of effectors according to three directions are noted as Figure 7 to Figure 12, which is the same as curves got form traditional methods of model and simulation.

Conclusion
Base on mathematical model of aerospace vehicles, flight simulative bank is built with Modelica language, and simulative system of aerospace vehicles is built, the simulation of the whole trajectory of aerospace vehicles is realized.

Figure 2 .
Figure 2. The relation between different models

Figure 3 .Figure 4 .
Figure 3.The process of model

Figure 6 .
Figure 6.Set initial conditions of simulation

Figure 6 .
Figure 6.set initial conditions of simulation

Figure 6 .Figure
Figure 6.set initial conditions of simulation

Figure
Figure 8. Ma curve