1. 研究目的与意义（文献综述）

this paper focuses on the design, selection and layout of power system for the 6-axis all-wheel drive evs. there are four aspects, the first is a choice of variety of battery types , and it needs to meet the requirement that the 2 tons’ car at least could drive 50km mileage; selection of drive motor, for example, dc or ac motor which with sufficient power density and torque density, and ultimately meet the maximum car speed 40km/h with the basic load and climbing requirements; at last, selection for the wheel brake system to ensure maximum utilization of energy, increase battery life and mileage.

when it comes into the 21st century, with the endless stream of energy problems and the gradually appear of drawbacks of traditional vehicles, domestic and foreign governments grow to support new energy vehicles more and more. in 2010,the government began to provide economic subsidies and concessions for electric vehicle purchases. in the year 2012, the state council issued "energy and new energy automotive industry development plan (2012-2020)". it hopes that the number of new energy vehicles in china increases to more than 5 million which is the world leading level in 2020. british energy secretary proposed a program to cancel the use of fuel vehicles in 2050. under this environment, new energy vehicles especially electric vehicles have great potential to develop.

some technologies such as nuclear power generation, tidal power generation, solar power become developed. it encourages the development of pure electric vehicles. for the replacement of the engine, domestic and foreign do much researches of electric motors. among them,the dc motor which is easy to control and the ac motor which has simple structure have made great progress in the control and output capabilities technology. in addition, it chooses the permanent magnetism motor which has excellent performance in all aspects as a research hotspot.

2. 研究的基本内容与方案

the main content of this paper is to design, selection and layout a drive system for a 6-axis all-wheel drive pure electric vehicle, which mainly for the battery, motor, controller and wheel brake system. the total mass of this vehicle is 2 tons, otherwise, its mileage is 50km and the maximum speed of 40km/h.

the design of the six-axis car’s battery is different with the ordinary pure electric vehicles. with the condition of the 50km minimum mileage, it needs to have a high specific energy, light mass, weak capacity attenuation, longer service life and has a better economy. the motor should have a high power density and energy density at a maximum speed of 40 km/h. so it could provide a large torque at low speeds. in addition , it should have a simple structure to ensure that the motor’s long life and high reliability in harsh conditions ,and it can be relatively simple to control. the target is to design a vehicle controller module based on can, battery module and motor module. for the motor, it should be able to ensure high performance of the motor output and can quickly make torque response; for the battery, it should optimize the battery energy distribution, accurately estimate the remaining energy and the remaining mileage, and could output appropriate current in different speed and torque, should provide excellent driving experience, and reasonable adjust the braking energy during the braking energy collection.for the vehicle module, it needs to receive the data of each sensor, should monitor the vehicle status of real-time to protect the normal driving function. and the wheel brake system based on disc brakes, combined with advanced braking system technology, to optimize it to achieve the appropriate braking capacity.

for the motor’s selection, dc motor can be easily controlled and had been widely used in last century, so this technology is developed; however, ac motor has more advantages than the dc motor, such as low cost, simple structure, but it has no commutator which results in complex control; but the permanent magnet motor has high power density, low energy loss and easy to control, so the initial selection is permanent magnet motor. as the target of the design is a six-axis all-wheel drive car, it is not applicable to apply the wheel motor or motor drive axle program because of many wheel axles. so the initial selection is a traditional car layout program, in which, the motor output power from the splitter assigned to the various axles. at present, there are many types of battery. however, each has its own advantages and disadvantages. considering to the technology of lead-acid battery is already very mature, and it has the advantages of low price, stable performance and simple structure. it is suitable for designing the target car. the controller selects the control strategy based on can bus. as for the wheel brake system, its mechanical structure based on the disc brakes which are commonly used, because it can provide stable braking performance.

3. 研究计划与安排

week19 -20 on 7th semester to determine the graduation design

topics, graduation design task book

(related parameters), school data

4. 参考文献（12篇以上）

(1)zhang wen-liang，wu bin，li wu-feng，lai xiao-kang and so on. discussion on development trend of battery electric vehicles in china and its energy supply mode [j].power system technology, 2009(04):1-5.

abstract: the actuality and trends of electric vehicles(ev) home and abroad are reviewed. the development trend of battery electric vehicles (bev) and its energy supply mode in china are emphatically dissertated. the development stage of bev in china is divided into two periods, namely the demonstration period and mature period, the keystone and the challenge in the current development period of bev are analyzed. finally, for the energy supply mode of bev, the key technology and technical direction to be researched are pointed out.

(2)hao ya-chuan. study of drive system based on permanent magnet synchronous motor in electric vehicle [d].beijing university of industry ,2008