The Development And Control Strategy Study Of 4WD Hybrid Electric Vehicle

Automobile has caused serious environmental pollution and crisis of petroleum. The development of electric vehicle is suffocated due to limited vehicle-used battery capacity. Hybrid electric vehicle (HEV) that combines the advantages of the conventional automobile and electric vehicle arises and becomes one of the most feasible ways to solve pollution and fuel problems. Integrated starter/generator (ISG) is one of the world-famous advanced technologies for future car which satisfies the requirements of high efficiency and low exhaust nowadays and in the future.In a HEV, the auxiliary power unit is combined with electric propulsion. The different types of HEV configurations can be classified into three basic kinds: series, parallel configurations, or a combination of both. This text put forward a kind of HEV which adapted to our country, adopting motor wheels driving technique in the meantime, developing a style car which adopted the motor wheels driving technique and merge ISG HEV. To improve the output power of the batteries and compact the structure of the driving system, we adopt the means of direct start with close clutch and enable the function of start and generation for ISG. Plate-formed ISG directly fix at end of the output shaft of engine, and make the parallel hybrid driving system advanced and compact with high efficiency. At the beginning of start process, the engine is driven to some rotate speed (a little higher than the idle speed) by ISG, and then engine is ignitus. In this way, ISG acts as a starter thus reduces the exhaust during start process. In normal situation (cruise), ISG stops, and engine provides the necessary power. When speed up or upgrade, ISG acts as a motor to assist propulsion, both the ISG and the engine can apply torque to move the vehicle and their torque combines on the engine output shaft. When speed-down or brake, ISG acts as a generator, which recovers energy through regenerative braking. When the battery SOC is lower than the minimum allowable SOC, the engine will provide excess torque which will be used by the motor to charge the battery. When vehicle waits at the idle speed for long time, ISG turns off the engine through ECU, and save the fuel and reduce the exhausts. The existence of the motor wheels, then can make the vehicle carry out purely dynamoelectric work condition, that is motor wheels purely dynamoelectric work condition; Motor wheels and engine driving together; Motor wheels , engine and ISG driving together; Engine drives ISG to generate electricity and motor wheels drives the vehicle. So opposite in the merge type ISG hybrid electric vehicle traditionally, this system has more work modes, the vivid of the choice is also larger, what to have meaning more is that it has 4W drive work mode, making the drive performance of vehicle better significantly.This text firstly carried on a detailed project design to the HEV ,mainly including: The powertrain project design;The 4W drive HEV project design such as the laying of the battery and motor wheels and their controllers, the laying of ISG and its controller, control system CAN total line network project design, the 4W drive HEV technique project design etc.. Then carried on the development of fast prototype system of the main controller, mainly carried on: the main controller's soft and hardware design; Main controller fast development and main controller hardware of the prototype system test a system development. The workflow of fast control prototype system is totally divided into the following four steps: (1) The HEV multiform energies powertrain controller model was build up in the Matlab/Simulink& Stateflow;(2)Defining the connection between fast control prototype and controlled signals, completing the link between fast control prototype and controlled signals, and increasing signal to pick up mold piece in the model according to the signals;(3)The dSPACE machine "rti 1005" edits and translate the step one off-line model to real-time model, in the meantime making use of a code auto born with download function download the model auto born codes to the DS1005 processor plank through a net line, and start real-time run, thus carried out quickly model of the control unit;(4)Making use of dSPACE the Control desk of the supervision software establish supervision interface, the control calculate way in the control unit is carried on real-time supervise and control.On this foundation, Adopting a layering, module set method for the whole car, each system was modeled. The modeling and imitating of motive system main controller was carried on, mainly including: the HCU model basic structure confirmation, the electrical logic analysis, the research of driver's intention identify technique; the energy management strategy research, The main function of the energy management is getting the best fuel economy and exhaust characteristic ,as far as possible satisfying driver's intention and demanding for driving torque and brake force , according to battery SOC, gear position at present etc., carrying on optimization of the fluxion path of multiform energies and load allotment. First analyzed energy fluxion path, then studied the method of brake energy feedback. The energy feedback mode has three method: (1) The ISG feedback generate electricity.(the speed of ISG is bigger than a certain enactment, the torque of ISG is bigger than the enactment feedback) While taking no account of motor wheels, that is, motor wheels don't participate whole drive and brake, under the condition of satisfying feedback, as far as possible make ISG feedback energy; When the feedback energy is bigger than the biggest feedback power of ISG, ISG with biggest feedback power feedback energy, while SOC is bigger than the enactment tallest value ,stop feedback; If motor wheels participate to drive and brake, motor wheels feedback energy. (2) Motor wheels feedback generate electricity. (the speed of ISG is bigger than a certain enactment, the torque of ISG is bigger than the enactment feedback) under the condition of satisfying feedback, as far as possible make motor wheels feedback energy; When the feedback energy is bigger than the biggest feedback power of motor wheels , motor wheels with biggest feedback power feedback energy, while SOC is bigger than the enactment tallest value ,stop feedback; (3) ISG and motor wheels feedback generate electricity in the meantime.( the speed of ISG or motor wheels is bigger than a certain enactment, the torque of ISG or motor wheels is bigger than the enactment feedback) The energy of feedback is bigger than motor wheels' biggest feedback power, and when battery admit, make ISG and motor wheels in the meantime feedback energy, while SOC is bigger than the enactment tallest value ,stop feedback;Made sure a bottom limitation of engine working alone zone and the control strategy with wheel motors. Carried on the research of the whole car coordination control calculation, including coordinate control engine, coordinate control ISG, coordinate control wheel motor and coordinate control AMT. Carried on an optimization of energy management strategy, put forward effect fuel consumption rate strategy. Imitated analysis of the economy of fuel of HEV in ECE+ EUDC circulation working condition, the motive system circulated appearance including purely dynamoelectric, engine driving alone, mixture driving, driving generating electricity and brake energy feedback, and the cut over of appearance. The result of imitation showed that improved basic line type control strategy had certain effect in the aspects of raising vehicle economy of fuel. Finally, carried on adjustment of the whole car, the model was well verified, carried out the optimization of the whole car control method. In the meantime on the turn drum in the laboratory experiment set and road experiment carried on the fuel economy and exhaust function, brake energy feedback experiment. Experiment results enunciation control method obtained good effect and came to an anticipant target and matched the goals.By the research of this topic, given to adopting the motor wheels driving technique and merge ISG HEV, provided a set of practical viable method and path, in the meantime for HEV control strategy, the research also has certain reference meaning. At the end of the article put forward some problems which need a thorough research.