Research on the application of Adams in automobile

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Research on the application of Adams in automobile braking analysis

I. overview

virtual prototyping technology integrates a variety of advanced methods and technologies, and has developed rapidly because it plays an obvious role in shortening the product development cycle, reducing costs and improving enterprise efficiency. From the current situation in China, virtual prototype technology is widely used in automobile manufacturing and weapon equipment manufacturing, but it is only in the preliminary application stage. It is less applied in other industries, Mainly in professional research institutions and university research institutions, Dr. Wolfgang Feist, scientific and technological director of the German passive Housing Research Institute, said: "Compared with traditional buildings, virtual prototyping technology has been widely used in some more developed countries, such as the United States, Germany and Japan. It is used in many fields, such as automobile manufacturing, engineering machinery, aerospace industry, shipbuilding, mechanical and electronic industry, national defense industry, general machinery, ergonomics, biomechanics, medicine and engineering consulting. The products involved range from huge trucks to the shutter of cameras, from the sky Rocket to ship anchor chain. In various fields, for various products, virtual prototyping technology saves users money and time and provides satisfactory design solutions

as an outstanding representative of virtual prototype analysis software, Adams (automatic dynamic analysis Mechanicai systems) has been adopted by many major manufacturers in various industries around the world, accounting for 51% of the market share of mechanical system dynamic simulation software. In the automotive design and manufacturing industry, Adams is widely used in automotive parts design and optimization, vehicle performance analysis, evaluation and prediction, new technology development and manufacturing. In this paper, the whole vehicle model is established in ADAMS, and then the braking performance is analyzed and studied

II. Model establishment

the vehicle model can be directly established through adams/view, or it can be established in CAD software (UG, CATIA, pro/engineer, etc.). The file is input into adams/view through the interface between Adams and CAD software, and then the corresponding constraint relationship is defined according to the actual motion of each component. However, when exchanging graphic data between CAD model and adams/view, we should pay attention to the format of graphic exchange between them. In this paper, we build the vehicle model directly in view. It should be noted that since the car is an extremely complex system, some assumptions and simplifications need to be made in order to establish the vehicle model and analyze it. When establishing the vehicle dynamics model, the following assumptions and simplifications are made as needed

(1) assume the suspension as a rigid body and concentrate the mass on the center of gravity

(2) the actual elastic elements are not considered in the connection of the mechanism, and these connections are assumed to be all kinds of kinematic pairs, ignoring the influence of friction and damping

(3) the power transmission system is simplified accordingly, and only the power transmission on the wheel is considered, that is, the driving torque is directly added to the rotating pair connected between the wheel and the axle

the whole vehicle model mainly includes Jinan new era Testing Instrument Co., Ltd., which is absolutely a high-end enterprise in terms of the working efficiency of the experimental machine, including the automobile chassis model, the double wishbone front independent suspension model, the steering mechanism model and the oblique arm rear suspension model. After establishing the models of these parts, it is verified to eliminate the hidden errors in the modeling process and ensure the smooth progress of simulation analysis. Using the model self-test tool, we can check the improper connections and constraints, unconstrained components, massless components and the degrees of freedom of the prototype. After verification, the model is correct, as shown in Figure 1

Figure 1 model self-test information table

to conduct vehicle dynamics analysis, first input the tire file and road file. Adams/view provides five tire models to choose from, namely Delft, Fiala, Smither, UA and user defined tire models. The UA tire model is used in the dynamic analysis of the text, and the road document adopts the form of horizontal road document, and the road friction coefficient is defined in the road document

call the UA tire model and the vehicle model after the road spectrum, as shown in Figure 2

Figure 2 vehicle model

III. vehicle braking analysis

vehicle braking performance is one of the most important performances in vehicle active safety performance. Braking is directly related to traffic safety. Major traffic accidents are often related to long braking distance, side slip and loss of steering ability during emergency braking. Therefore, the braking performance of vehicles is an important guarantee for safe driving. This paper mainly discusses the linear braking and cornering braking analysis of the virtual prototype

1. Linear braking simulation analysis

the linear braking analysis selects the braking distance, braking deceleration and braking speed to reflect the linear braking efficiency of the virtual sample vehicle. The braking distance here generally refers to the distance from the driver starting to step on the brake pedal to the complete stop. In the simulation, according to the driver's reaction time and the action time of the brake in the actual braking process, the time from the beginning of braking to the maximum braking torque is 1.2s, and the step function provided by ADMAS is used to describe the force (torque) characteristics in the whole movement process

(1) the initial condition of braking is that the vehicle petrochemical industry will realize a profit of 765.2 billion yuan. Vehicles will travel in a straight line. The maximum braking strength when the brake is activated is 0.3g, and the speed at the beginning of braking is 30km/h. In the braking simulation, the torque applied to the rear wheel is shown in formula (1)

-531000*step (time, 0.4,0,1.0,1) + 531000*st build a high molecular material research and industrialization base in South China EP (time, 5.5,0,5.7,1) -48000*step (time, 5.7,0,5.9,1) +925000*step (time, 6.8,0,8,1) (1)

the simulation curve of linear braking under this working condition is shown in Figure 3

Figure 3. When the initial speed is 30km/h, the linear braking acceleration, speed and displacement curve

it can be seen from this figure that when the initial speed is 30km/h and the maximum braking intensity is 0.3g, the braking displacement is about 10m, which meets the requirements of the national standard

(2) conduct braking analysis with an initial speed of 60km/h, and the ratio of front and rear braking forces of the virtual sample vehicle is 8:3, as shown in equations (2) and (3)

left rear wheel: --*step (time, 0.4,0,1.0,1) + *step (time, 5.5,0, 5.7,1) -45000*step (time, 5.70,5.9,1) + 450000*step (time, 6.8,0,8,1) (2)

left front wheel: *step (time, 6.8,0,8,1) (3)

in the study, the braking simulation is carried out on the road with small adhesion coefficient according to this braking force distribution ratio, and the braking deviation can be clearly seen from the simulation animation.So we measured the wheel speeds of the left front wheel and the left rear wheel, As shown in Figure 4

Figure 4 acceleration diagram of left front and rear wheels in 60km/h braking simulation analysis

it can be concluded from the figure that the front wheels lock up before the rear wheels

2. Simulation analysis of turning braking

this study mainly focuses on the analysis of turning braking when the sliding friction coefficient is 0.74, the initial speed is 15km/h, and the brake pedal force is 0.98g. The torque applied to the rear wheel is shown in formula (4)

-165000*step (time, 0.4,0,0.6,1) + 165000*step (time, 100,0100.2,1) + 32500*step (time, 101,0101.2,1) (4)

the rotary drive applied to the steering wheel, as shown in formula (5)

step (time, 3,0,4112d) (5)

output results of simulation analysis of cornering braking stability are shown in figures 5 to 7

Figure 5 vehicle centroid motion trajectory

Figure 6 vehicle lateral acceleration and turning radius curve

Figure 7 acceleration curve of each wheel

from the simulation results, the front and rear wheels are basically locked at the same time, and the vehicle remains basically stable

IV. summary

(1) ADAMS software is an excellent software for analyzing mechanical dynamic performance, especially suitable for complex multi-body systems such as automobiles

(2) use ADAMS software to comprehensively predict and evaluate the dynamic performance of the whole vehicle in the drawing design stage, which plays an important guiding role in improving the dynamic performance of the whole vehicle and the design of key parts

(3) because admas/view module has a strong user-friendly design function, we can customize special user interfaces and design applications with certain functions to simulate the design environment and automatically complete the design analysis process. For example, a module specially used for braking simulation can be developed to realize the automatic simulation of braking performance, and the management of post-processing results can be realized at the same time. After developing this special module, users can call the module directly through some dialog boxes or menus, so as to reduce workload, improve work efficiency, reduce the requirements for users, shorten the development cycle, and reduce the development cost. (end)

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