| Funded by the science and technology projects for national antiterrorism (709 project), this paper has been completed.After the"9.11"incident happened in the United States, though the voice of global antiterrorism has been raised, the attacks launched by terroristic organizations are more prevalent globally, according to incomplete statistics, car bombs were in the majority of these attacks. Consequently, in order to protect people's life and property, maintain social stability and unity, and cooperate with the relevant departments to fight against such events effectively, the design of a set of vehicle arresting system is very meaningful.At present, on the basis of arresting effects, the vehicle arresting system can be divided into two types: rigid vehicle arresting system or flexible vehicle arresting system, the rigid vehicle arresting system is more commonly used, but which can easily cause the complete destruction of vehicle and seriously threaten the safety of persons in the vehicle, because the arresting process is instantaneous, the arresting distance is very short (or zero), and a great portion of vehicle's kinetic energy can be transformed into the deformation energy. However, the flexible vehicle arresting system can avoid the above-mentioned weaknesses of rigid vehicle arresting system, which can absorb the arrested vehicle's kinetic energy by energy absorber and make the arrested vehicle slow down at a smaller retarded velocity in a safe distance to protect the safety of persons in the vehicle and avoid the complete destruction of vehicle.On the basis of different functions of the parts that compose the whole, the flexible vehicle arresting system can be divided into six subsystems: the energy-absorbing subsystem, the net subsystem for arresting vehicle, the subsystem for spreading net, the ground anchor subsystem, the electrical subsystem and the auxiliary subsystem. The performance of energy absorber as the core of flexible vehicle arresting system has a direct impact on the arresting effect, this paper used the multi-piece frictional energy absorber with complete disc type, which under a normal operating condition can produce the brake torque with fixed value and have the same working principle as the frictional clutch, that is by exerting a certain extent of positive pressure on a set of kinetic and static friction plates, the work done by the friction force between friction plates consumes the vehicle's kinetic energy.When the flexible vehicle arresting system arrests works, because its arresting process is very complex, in the center of mass the interactions of various forces form a complex system of forces in space, the interactions between them together have an impact on the arresting performance of system. Therefore, on the basis of mathematical equations of the parts that compose the whole and comprehensive mathematical models, this paper intensively studied the simulation and test of the arresting performance of flexible vehicle arresting system to enrich and improve the arresting theory, and to lay a theoretical foundation for the follow-up study of flexible vehicle arresting system.This paper is divided into 5 chapters, the main contents and conclusions of study are as follows:Chapter I: this paper introduced the research background of arresting vehicle system, provided an overview of its concept, the domestic and foreign development situation and trend of flexible vehicle arresting system, and showed the major research contents and significance.Chapter II: firstly, this paper introduced the composition and working principle of flexible vehicle arresting system, put forward the corresponding technical requirements for energy absorber which is the core of system. By going through the domestic and foreign related reference materials and comparing the strength and weaknesses of some energy absorber cases including turbine damper, frictional energy absorber with drum type, frictional energy absorber with caliper type and multi-piece frictional energy absorber with complete disc type, after considering the heat stability, brake torque, heat dispersing performance, quality, product cost and so on, finally this paper chose the multi-piece frictional energy absorber with complete disc type as the optimal case. This paper also introduced the working principle of multi-piece frictional energy absorber with complete disc type and the functions of the parts that compose the whole, then this paper derived the formula which is used to calculate the brake torque produced by the energy absorber under a normal operating condition.Chapter III: in the flexible vehicle arresting system with multi-piece frictional energy absorber with complete disc type, by using the geometric mapping method, the spatial analysis and the dynamics, in view of the simple condition that the point of contact between the vehicle and net is on the runway center, on the basis of only considering the correlation parameters of one energy-absorbing system on the side of the runway, this paper initially set up the mathematical equations of the parts that compose the whole and comprehensive mathematical models including the kinetic equations of arrested vehicle, the equation of relation between the arresting force and pulling force of brake band, the kinetic equation of energy-absorbing disc, the equation of relation between the angular velocity of disc and movement velocity of vehicle, etc.. Moreover, in view of the complex condition that the point of contact between the vehicle and net is off the runway center, on the basis of considering the correlation parameters of two energy-absorbing systems on both sides of the runway, this paper subsequently set up the mathematical equations of the parts that compose the whole and comprehensive mathematical models including the kinetic equations of arrested vehicle, the velocity expressions of brake bands on both sides of the runway, the physical quantity and parameter expressions of energy-absorbing systems on both sides of the runway, etc..Chapter IV: in view of the complex condition that the point of contact between the vehicle and net is off the runway center, on the basis of considering the correlation parameters of two energy-absorbing systems on both sides of the runway, this paper firstly used MATLAB/SIMULINK software to build the arresting process model based on the mathematical equations of the parts that compose the whole and comprehensive mathematical models. This paper also did the simulation analysis of three different conditions that the point of contact between the vehicle and net is off the runway center, these conditions include that the distance between the vehicle and the runway center is 0m, the distance between the vehicle near the energy-absorbing system 1 and the runway center is 1m, the distance between the vehicle near the energy-absorbing system 2 and the runway center is 1.5m. The simulation results show the characteristic quantity change laws of system under three different conditions that the point of contact between the vehicle and net is off the runway center, these characteristic quantities include the velocity- v y, the displacement- S y, the acceleration- a y, the pulling force of brake band- Fl 1, the pulling force of brake band- Fl 2, the offset- p x, and this paper verified the correctness and effectiveness of the comprehensive mathematical models of system which are in Chapter III, and showed that the flexible vehicle arresting system has the ability to correct the offset and can arrest the vehicle in a limited distance, but the pulling force of brake band near the vehicle gradually increases, the other pulling force of brake band far from the vehicle gradually decreases. Secondly, in view of the simple condition that the point of contact between the vehicle and net is on the runway center, the real vehicle test of flexible vehicle arresting system has been finished, so this paper compared the simulation curves with the test data to further verify the correctness and effectiveness of theoretical analysis and simulation. Finally, the paper also analyzed the problem that in the real vehicle test there was the rush curve of pulling force of brake band, and gave some corresponding improving directions to provide the theoretical support, the technical reference and the research method for the further development and application of flexible vehicle arresting system.Chapter V: summary and outlook. This paper summarized the full text and gave some advices about future research ideas. |
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