Over the past two decades, the achievements in computing technology, design theory, testing methods, new materials, technology and other aspects have made the modernization of automotive products and the structure and performance of automotive products glorious - new.

On the one hand, the development of automotive technology is the rapid development of internal combustion engine technology. On the other hand, to ensure high-speed driving safety, it requires good braking, safe driving performance and handling stability; on the other hand, to ensure comfort, it requires good smoothness. The improvement of power, safety and ride comfort of automobile promotes the new development of automobile technology.^[1]

In the automobile development history of more than 120 years, great changes have taken place in automobile design technology, which has gone through the stage from experiential design to design based on scientific experiments and technical analysis. In the middle and late 20th century, after introducing computer into design, new methods such as computer aided design (CAD) were formed, which gradually realized the semi-automation and automation of design.^[2]

Automobile theory is an applied science that closely combines theory with practice. The course of automobile theory mainly studies the kinematics and dynamics of automobiles (including automobile trains) and their mechanisms, studies the performance of automobiles, and provides theoretical basis for automobile design, evaluation, test, research and application.^[3]

Driving axle is one of the components of transmission system. For rear-driven vehicles, it is the general name of all transmission mechanisms and their shells installed behind the transmission or transmission shaft and before the driving wheel. Its function is to distribute the power from the universal transmission device to the left and right wheels after decelerating, increasing torsion and changing the transmission direction of the moment, and to allow the left and right wheels to run at different speeds on uneven roads and steering.^[4]

Drive axles are divided into two types: disconnected and non-disconnected. When driving wheels adopt independent suspension, disconnected driving axle should be chosen; when driving wheels adopt independent suspension, disconnected driving axle should be chosen. The structure characteristic of the disconnected driving axle is that there is no rigid integral shell or beam connecting the left and right driving wheels. The main reducer, differential and its shell are installed on the frame or body, and the wheel is driven by the universal transmission device. At this time, the mass of the main reducer, differential and part of the wheel transmission device are all spring mass. The driving wheels on both sides are elastically connected to the frame or body by independent suspension, so they can swing up and down independently relative to the frame or body. In order to prevent the movement interference between the universal transmission and the independent suspension guiding device due to the change of wheel spacing when the wheel runs.^[5]

Restricted by the development level of science and technology, traditional design is based on production experience and is based on formulas, charts and manuals formed by mechanics, mathematics and regression methods. With the deepening of theoretical research, many engineering phenomena have been sublimated and summarized, and become theories to reveal the inherent laws and essence of things, such as computational geometry of body design, various optimization design theories, modal analysis theory, reliability theory, fatigue theory, artificial intelligence theory and so on. Modern design method is based on theory. Using this method to guide design can reduce the blindness and randomness of experiential design and improve the initiative, scientificity and accuracy of design. Therefore, modern design is a kind of design which is guided by theory and supplemented by experience.^[6]

Generally, automobile suspensions are composed of three parts: elastic elements that can mitigate impact, shock absorbers that can attenuate vibration, and steering mechanisms that can transmit various forces and reactions, and maintain the correct motion relationship between wheels and body I. In order to prevent excessive lateral tilt of the car body during steering, some cars have also installed lateral stabilizing rods.

The structure type of suspension is related to the structure type of vehicle bridge used in automobiles. According to the difference of the motion relationship between the wheels and the body, the suspension can be divided into three types: independent suspension and balanced suspension. The wheels of the independent suspension are connected to the frame (or body) separately through the suspension, and can move independently. It is often matched with the disconnected axle. The left and right wheels of the independent suspension are not connected to the whole axle. The left and right wheels of the non-independent suspension are connected by a monolithic axle, together with the axle, and the frame (or body) is connected by the elastic suspension, which has a definite connection with the ups and downs of the wheels at both ends of the axle. Balanced suspension - generally matched with integral axle, it is a suspension type that can balance the load of left and right wheels on the front and rear axles.^[7]

This book discusses the basic transmission principle of manual transmission and transmission axle of current general purpose automobiles.

On the principle of maintenance, the transmission systems of rear-wheel drive, front-wheel drive and four-wheel drive are introduced.

The work of main assemblies such as clutch, transmission, drive axle, transmission shaft, differential and universal joint

Principle, common faults and their causes, fault diagnosis methods, maintenance methods and maintenance points.

The book is divided into two chapters and 16 chapters. The first part is theory and the second part is practice. At the end of each chapter, there are summaries and dimensions.

Examples of repair analysis, ASE fault diagnosis table and ASE review questions. This book has a lot of illustrations, the next part

A large number of photographs describing the detailed maintenance process are also attached.^[8]

Transmission is one of the most important components of automotive transmission system. It is mainly used to change the speed and torque of the car, make the car run in the opposite direction, and achieve neutral sliding. The drive axle is located at the end of the automotive transmission system, and its performance directly affects the performance of the whole vehicle, which is particularly important for heavy-duty vehicles. This book studies the design of vehicle transmission and drive axle, including the design of hydraulic torque converter, two-axle manual transmission, three-axle manual transmission, hydraulic mechanical automatic transmission and drive axle.^[9]

The purpose of this book is to introduce the basic theory and method of automobile chassis design. The book is divided into 12 chapters, including the overall design of the car, load and strength calculation methods of automobile parts, clutch design, mechanical transmission design, universal joint and transmission shaft design, drive axle design, frame design, wheel positioning, suspension design, steering system design, brake system design, vehicle steady-state handling stability design. The book mainly deals with design requirements, analysis and selection of structural schemes, determination of main performance and structural parameters, calculation methods of performance and strength, determination of calculation loads, etc.^[10]

There are a series of development bottlenecks behind the huge market prospects of China's automobile and bridge industry, and the manufacturing technology of automobile and bridge is the first one to be affected. In recent years, with the introduction of the whole vehicle and joint ventures, many vehicle and bridge products have been localized through technology introduction, digestion, absorption and imitation, and the products have been localized. At present, the biggest advantage of domestic automobile axle products is low cost and low price. However, there is still a big gap between domestic automobile axle products and foreign advanced technologies in noise, processing accuracy, life and bearing capacity.^[11]

Including reducer, transmission, commonly used motor, electrical appliances and electric (hydraulic) push rod. The general design information of reducer and transmission is mainly introduced. The structure, characteristics, shape and installation dimensions, performance parameters and selection of common standard reducers (cylindrical gear bevel-disc CVT, RING-CONE planetary CVT, belt CVT, tooth chain CVT, three-phase and four-link pulsating CVT, etc.) are introduced. Electrical appliances and electric (hydraulic) push rods mainly introduce common motors (general asynchronous motors, variable speed and deceleration asynchronous motors, three-phase asynchronous motors for lifting and metallurgy, flameproof asynchronous motors, vibration asynchronous motors, low-power motors, DC motors, etc.) and common electrical appliances (electromagnets, stroke switches, proximity switches, photoelectric switches, tubular electric heating elements, etc.). The types, characteristics and selection of electric push rod, electro-hydraulic push rod and elevator products.^[12]

This research is based on a four-axle vehicle with eight in-wheel motor driving wheels and dual-axles steering system, and its original mechanical steering system was preserved. We proposed a new steering pattern that can be used on the in-wheel motor driving vehicle which features the independent driving of in-wheel motor driving wheel. With focus on the differential drive steering system, its working principles were introduced and its feasibility was discussed. A dynamics model for the vehicle including the steering system was built based on Matlab/Simulink. The characteristic curve of the target torque distribution and the control algorithm for the torque output of both sides of steering wheels were presented and simulated. The simulation results show that differential drive steeringis feasible, which can greatly reduce driver's workload, and improve the steering performance of the vehicle, the requirements of steering were achieved.^[13]

Firstly, based on the theories and methods of acoustic array measurement, the surface radiation noise of the rear driving axle of minibus was tested in the bench experiment. With the analysis of the experiment data, sound holography contour map was used to plot the noise distribution of the rear driving axle. It is found that the major noise source closes to the case of main reducer of the driving axle. The major noise frequencies are related to the gear meshing vibration. These results basically coincide with the sound intensity experimental results.^[14]

When turning at high speed, multi-axle vehicles are prone to steering shimmy, and even turning out of control and other issues. According to the characteristics that the driving torque of each electric-wheel can be independently controlled, the Direct Yaw Control strategy was proposed to improve the vehicle's steering characteristics. According to vehicle steering characteristics, a yaw rate calculation formula was established, that was also a yaw rate of the control objectives. The five-axle vehicle dynamics model was established with software ADAMS, and DYC-TCS control strategy was built with software Simulink. The step input response test was proceeded with different driving speed. It was found that when turning with DYC-TCS control strategy, the controllability of yaw rate can be significantly improved, the yaw rate convergence time became short, in particular, steering shimmy tendency can be reduced. It can improve the vehicle's handling and stability.^[15]

In the design process, the design requirements of the driving axle should be analyzed, and the structure, performance and characteristics of the common steering driving axle should also be analyzed. Then the steering driving axle of the Maiteng 1.8T car should be designed, and the general assembly plan of the steering driving axle should be made. The position layout and structure selection of the main reducer, differential, half axle, steering knuckle and axle housing should be completed. Finally, the motion and strength of the mechanism should be checked.

Technical programme:

Firstly, the structure type and layout of the automobile driving axle assembly are understood. Starting from the type of automobile and its use and production conditions, and adapting to the other parts of the design collar, especially the structure type and characteristics of the suspension, the purpose is to ensure the expected performance of the whole automobile. Considering that the front suspension used by the Metten 1.8T car is the McPherson independent suspension, the design of the automobile driving axle assembly is carried out. Therefore, the disconnected driving axle is chosen.

Secondly, the main reducer of the driving axle is designed, including the structure type of the main reducer, the determination of the main reduction ratio, the determination of the calculation load of the main reducer gear, the selection of the basic parameters of the main reducer gear, the material and heat treatment of the main reducer gear, the calculation of the bearing of the main reducer, and the lubrication of the main reducer.

Then the structure type of the differential and the driving device of the driving wheel are determined, the transmission efficiency of the differential, the locking coefficient and the torque distribution coefficient of the differential are calculated, the type of the automobile half-axle is selected, the design and calculation of the automobile half-axle are completed, and the form of the universal joint of the driving wheel transmission device is properly considered.

Finally, a reasonable steering system is selected to adapt to the designed driving axle, and the position relationship between the driving axles of the steering system is considered to avoid the occurrence of motion conflicts.

[1]名顺平.汽车构造[M].武汉：武汉理工大学出版社,2016.

[2]张炳力.汽车设计[M].合肥：合肥工业大学出版社，2011.

[3]余晨光，邓宝清.汽车理论[M].长沙：中南大学出版社，2016.

[4]于秀涛.汽车构造[M].北京理工大学出版社，2018.

[5]王望予.汽车设计[M].北京：机械工业出版社，2008.

[6]李胜琴，王若平，张文会.现代汽车设计方法[M].北京：机械工业出版社，2013.

[7]吴基安.汽车工程师手册[M].哈尔滨：黑龙江科学技术出版社,2005.

[8]Jack Erjavec.汽车手动变速器和变速驱动桥[M].北京：机械工业出版社,1998.

[9]许兰贵.车辆变速器及驱动桥设计[M].北京：中国水利水电出版

社，2018.

[10]罗永革，冯樱.汽车设计[M].北京：机械工业出版社，2011.

[11]刘惟信.汽车车桥设计[M].北京：清华大学出版社，2006.

[12]成德夫，姬奎生，韩学铨，姜勇，李长顺，王雄耀，虞培清，成杰，谢京耀.机械设计手册[M].北京：机械工业出版社，2017.

[13]Junhan Tang, Junqiu Li, Yuebo Liu. Transportation Electrification Asia-Pacific[J]. 2014.

[14]Huibin Li,Mengxi Ning,Chengxia Zhang,Bo Yu. Intelligent System Design and Engineering Application[J].2013.

[15]Zhu Yong-qiang,Chen Quan-shi,Zhang Ping-xia. Consumer Electronics, Communications and Networks[J]. 2013.