Study On The Design Of Electronic Control Unit For CVT

CVT has long been the most ideal Transmission which people provide for their cars. With the consistent regulation of speed ratio, the CVT system can ensure the workings of the engine at a low consumption of fuel level. Therefore, the consumption of the fuel as well as the exhaustion of the waste gas can be greatly reduced. What's more, the CVT system can enable the cars to run smoothly and therefore make people feel more comfortably. The CVT system,as an advanced technology, it can meet the developing demands of passenger car and there will be a great developing potentiality and extensive market.The electronic hydraulic control system is the key part of CVT, the thesis mainly focuses on the study of electronic control unit of CVT. After reading many reference literatures, this thesis analyzes the features and its operating principle of CVT, and states that the CVT will be the developing tendency for the transmission of passenger car. Based on the analysis and study on the electronic hydraulic control system of CVT, the mathematical models of CVT are established, which is the theoretic foundation for CVT control system.According to the control targets of CVT, the general solution of ECU for CVT which is based on TMS320LF2407A as microprocessor is put forward. Firstly, the smallest operating system for ECU is designed. Then, interface circuit which is connected external sensor signal or actuator with microprocessor is analyzed. After accomplishing the logical design of the ECU, printing circuit board (PCB) is devised. In order to decrease the size of PCB and increase the stability of PCB, the author adopts a series of measures to realize the targets above. A number of methods which are applicable in automobile electronics field are concluded in the paper.Besides, the low-level driving program of the ECU is developed. For example, ADC program, which can be used for testifying the ECU, also be used as the subprogram for CVT control system main program. The ECU and low-level driving program are tested on the test-bed, and the test result shows that the developed ECU and low-level driving program are correct.In the end, the principle of traditional rotation speed measuring methods including frequency method and period method are analyzed, and the advantages and disadvantages of traditional rotation speed measuring methods are discussed respectively. The paper presents a new method, through which we can measure the rotation speed at a higher precision with the same rotation speed sensor.