Simulation And Test Research On Metal Belt CVT Based On Bond Graph Theory

Automobile is one of the symbols of human civilization, it's development must conform to the requirements of the society. 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, which based on the science and technology major research emphasis item of The Ministry of Education——"The research of car's continuously variable transmission dynamic matching rule andthe electrohyraulic control systems integration exploitation"and Changchun City science and technology bureau tackle key problems item——"The hydraulics building block design means very combination control characteristic of Car's continuously variable transmission(CVT)".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, therefore V-mode metal belt's transmission mechanism is different from apron belt. The stess analyse of metal belt is extraordinary intricacy, 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 process control.Thirdly, summarizes background and history as well as character and basic principle of bond graph as research theory. Pay much attention to bond graph applied in continuously variable driving system simulation. Analyze deeply the continuously variable driving system structure and working principle, set up each assembly bond graph model, couple whole car bond graph model, establish research and simulation foundation for continuously variable driving system dynamic characteristic adopting bond graph.Fourthly, to different engine, load bearing characteristic and speed characteristic is different, therefore CVT's ratio speed is different too. The dissertation utilized the mating motor's test data,using formula fitting process to found torque numerical model,according to lumped mass method, continuously variable transmission system is boiled down to two rotating mass model system, then based on the motor numerical model, we got the vehicle's best power and optimal economy ratio speed. Using PID control method to control ratio speed rate of change, thereby achieve the aim of speed ratio control. I did some simulation analyses before test for prove the feasibility of control method. 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, then made simulation analysis to three different working condition: fist time step process,starting-up to speed process and accelerate came in for road resistance process. The simulation result indicate that ratio speed following condition of this model is in order which explain the PID control design is reasonable, and it made a favorable foundation for the next bench test.In the end, we did bench test under the test condition we have to demonstrate the control-theory right or not. The test included constant speed ratio follow,step speed ratio follow,simulate fist time step working condition and deceleration , from the test resule we can see this control system effect all right and possess definite feasibility,but owing to limitation of test condition, we can't proceed the next bench test and auto-test.In a word, CVT is the most newfashioned automatic transmission gearing which have multitude mechanism,hydraulic pressure,eletron and computrerized technology. This kind of transmission now is on research phase in our country, there are some challenge problems in transmission mechanism,system design and test. So maste these 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.