With the improvement of people's consumption level, automobile has become the most popular means of transportation, and the road safety problem caused by it has been paid more and more attention as a common social problem all over the world. As one of the main performance of vehicles, manipulation stability has important research significance for driving safety,especially safe driving at high speed.Manipulation stability is essential to give full play to the power of the car, reduce the degree of portability of driving, and improve the rate of transport production. Maneuverability and stability are closely related, loss of maneuverability will make the car slip or even overturn, and the stability of the function can directly affect the handling performance. The main function of the steering system is to complete the steering according to the driver's steering manipulation instruction, control the handling stability of the vehicle while driving, etc.

Currently widely used in real vehicles are power steering, including HPS,EHPS and EPS, while AFS and 4WS technologies are also used on some high-end models. SBW System, as the most cutting-edge achievement of the electronic steering system, will meet people's requirements for the environmental protection, safety and comfort of automobiles. SBW System can not only design variable transmission ratio freely, but also adopt steering control strategy, which can obviously improve the control stability of automobile during driving. The SBW system can also optimize the driver's road feedback torque, design a suitable road sense, make the back positive torque on the steering wheel comfortable, increase the steering portability of driving, reduce the driver's load, increase driving safety.

TRWof the United States first proposed to replace the mechanical connection between the steering disc and the steering wheel with a control signal, after which the German Kassel Mann and Kearney designed the early linear control steering model. Subject to electronic control technology, it was not until the age of the century that the wire-controlled steering technology made great progress. in the year, Infiniti's "Q50" became the 1 mass-produced model using wire-controlled steering technology. Many foreign universities have also put into the research of SBW system, and put forward a series of related steering control strategies. Paul Yih of Stanford University in the United States has studied the full state feedback control strategy to achieve the driver's desired steering and carried out SBW hardware in the ring test. B.zheng of Indiana Purdue University at Boris United proposed an active front wheel steering control strategy based on full state feedback swing angular velocity stability control, which achieves vehicle steering and decoupling pendulum damping by feedback swing angular velocity and forward rotation angle. Bertoluzzo of the University of Padua, Italy, proposed a SBW model matching the same structure based on the traditional steering design SBW system, using the model parameters of mechanical steering, The relevant steering parameters are set in their SBW system. Ba-hai nguyenl of the Korea University of Technical education and others have proposed the direct use of current sensors to measure the current to perform motor and road sense analog motor currents to complete the back-positive torque feedback and steering execution of the closed-loop control, speed up the system's rapidity and accuracy, saving costs and simple and feasible. Japan's Yousuke Yamaguchi and others have designed a pure electric vehicle with a SBW system that increases steering through an adaptive control strategy and designs a lateral acceleration observer with parameters to estimate steering resistance. Dirk Odenthal of the German Aerospace Center proposed the SBW system as a remote control system with a degree of freedom, believing that SBW The system has the same effect as the widely used EPS system when the steering wheel has equal displacement force with the front wheel and the stability of the system is consistent.

Compared with the foreign SBW system Research, China started late, is still in the theoretical research and experimental testing stage, the domestic automobile manufacturers have not developed a prototype containing SBW system, the major domestic universities to SBW System theory research mainly, and achieved a series of results. At the Shanghai International Industrial Expo in 2004 , Tongji University showcased its independent research and development of the SBW system concept car "Chunhui third". The car does not have a design door, has four-wheel drive technology, and uses batteries and fuel cells to form an electric - electric hybrid battery system to power the vehicle, but also in its liquid crystal instrumentation system designed "and Xin" operating system. At the Shenzhen World Electric Vehicle Exhibition in 2010 , Jilin University showcased its R amp; amp; D of pure electric vehicles with wire-controlled four-wheel steering. The wire-controlled electric vehicle will be directly equipped with a 2KW DC brushless motor Hub motor as four drive wheel installation, directly to remove the transmission, main reducer and differential, clutch and other structures. According to the structure of SBW system, Dr. Yang Shengbi of Wuhan University of Engineering has established the dynamic model of steering execution and road sense respectively and determined the empirical formula, and designed the steering control strategy of fuzzy variable transmission ratio. ; The state tracking algorithm is also designed to compare with the ideal steady-state two-DOF pendulum angular velocity gain to improve the control stability of the whole vehicle, and through adams/car and matlab/simulink The steering control strategy of the design is verified by joint simulation, and the fuzzy road sense is designed, and the test verification is completed by the hardware in the ring test. Professor Roshi of Jiangsu University designed the fuzzy Feedback control algorithm of current and velocity to realize the road sense simulation and steering wheel return, and used the sensor and Kalman filter State Observer to predict the body attitude.

SBW as a brand-new steering system, the system solves the problem that the steering accuracy and manipulation stability of the traditional steering system can not be balanced, is a major innovation of the automobile steering system, has the advantages of irreplaceable, and at present, for SBW System R amp; amp; D has become a hot spot for major universities and automakers. SBW System is not fully used in real vehicles because of the influence of technology, safety, reliability and other factors, but because of its good maneuverability, saving layout space, saving energy and other advantages, so the future of SBW system has broad prospects. And China's wire control technology because of the development of too late, all aspects are not mature, in order to achieve the future domestic intelligent car online control steering Technology Universal application, there is still a long way to go. This topic is based on this purpose, according to the linear control steering, the implementation of dynamics and kinematics simulation, and finally explore its control strategy to carry out research.

2. 研究的基本内容与方案

2.1 Basic Content

1. According to the basic principle of wire control steering, complete the line control steering overall system design;

2. Complete the geometric design of key components

3. Motion Simulation and dynamic simulation of steering gear

4. Establish the control model of SBW system and carry out simulation analysis