| The two main themes of the contemporary world are economizing energy and protecting environment. However, millions of autos running in the street are the major subjects of energy consumption and environmental pollution. Therefore, one of the directions of future automobile development is to take effective measures and apply new technology to reduce the fuel consumption and minimize exhaust gas. Because the characteristic of Internal-combustion Engine is different from that of the Ideal engine, So a transmission is needed to improve the performance of powertrain. And the most effectual and promising way is CVT ( Continuously Variable transmission ). The metal pushing V-belt type continuously variable transmission (CVT) has the advantages of simple and compact structure, easy operation, excellent performance, low cost and fuel economy. As an advanced technology to develop passenger car, it can meet the demands of developing transmission in our country. So this technology attracts much more attention in recent years. The dissertation mainly focused on the speed ratio control of CVT and matching with engine, the main research contents as follows:Firstly, the dissertation reviews the development process and the technique of CVT briefly. Through the comparison with other transmission, showing that the metal pushing V-Belt type CVT can meet the currently demand of drivability, economics and emission etc, and stating that the CVT is the ideal transmission which will be the developing tendency for the transmission of passenger car. In the paper the background and the necessity of this theme in science and practice are given.Secondly, the dissertation introduces the CVT's basic structure and critical components, which makes we know clearly that the V-mode metal belt possess unique feature, analysised the dynamics of the V-mode metal belt so as to we can understand it better. Whereas the transmission mechanism of metal belt is the rational of its transmission and control, thereby educes three critical technologies of CVT's control system---clamp force control,ratio speed control and fist time step processcontrol.Thirdly, Eatablishing foundation of continuously variable transmission system's dinamics model by using above condition.The dissertation utilized the palio motor's test data, using formula fitting process to found torque numerical model,oil wear numerical model and magnitude of power model of the motor. Thereby gotten universal characteristic and speed adjustment characteristic of the mating motor, which eatablished foundation of continuously variable transmission system's achieving the best economy and the great power matching, consequently supply clearly gist for CVT system control.Fourthly, study on the fuzzy control arthmetic and a mixed fuzzy-PID control arthmetic which logic hasthe characteristic to simulate the thinking of human being. And can be used to analyze the relationship of model description and linguistic description. And using fuzzy controller and mixed fuzzy-PID controller to control the CVT ratio.Fifthly, based on the continuously variable transmission system's dinamics model, In the dissertation, founding simulation modle of vehicle with CVT system under simulink environment of matlab software, which include engine submodel,CVT-automobile submodel,target ratio speed submodel and ratio speed control submodel which including fuzzy controller model and mixed fuzzy-PID controller model.In the end, we did the simulation which including constant speed ratio follow,step speed ratio follow,simulate fist time step working condition and deceleration .We analysised and campared fuzzy controller and mixed fuzzy-PID controller in the simulation which effected on the motor. The result of the simulation indicated that put PI contol into the fuzzy control formed the mixed fuzzy-PID control which can complete the fuzzy control precision, advance the control precision. So, the mixed fuzzy control arithmetic is better then the fuzzy control arithmetic and from the resule of the simulation we can see the mixed fuzzy-PIDcontrol system effect all right and possess definite Feasibility.In a word, the theories and critical technology have importmant practical meaning in advancing independence exploitation ability of our national made car and shorting the gap with developed country, certainly it is the common goal of each large automobile corporate.
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