| One of the aims of automobile industry over the years has been to improve the mechanical efficiency of automatic transmissions, as well as retaining the comfort of automated gear shifting and powershifts of good shift quality. As a response to this demand, Dual-Clutch Transmission has emerged as the times require. The principle of DCT is depicted in chapter 1 and works as following: There are two gearboxes(gearbox 1 for the odd and gearbox 2 for the even gear numbers) that are both built up like conventional manual transmissions comprising of helical gears and synchronizers to engage the selected gears. Both gearboxes are connected to the output shaft via a gear stage and can be coupled to the main input shaft of the transmission and therefore to the engine by either of the two clutches. By changing from one gearbox to the other (i.e. by disengaging the off going clutch and engaging the oncoming clutch) a gearshift can be accomplished. This results in shift characteristics that are typical of clutch to clutch shifts commonly seen in conventional automatic transmissions. Be differ from other transmissions with a single clutch, a aptitude and accurate cooperation of the two clutches highly influences the running of vehicle. If the two clutches'works overlap each other too much, it will hitch two shifts at the same time, which may lead to the flameout of the engine; and if they overlap each other too small, the driving force will intermit a little as a result. Therefore, how to control the cooperation of two clutches during the process of shift is one of the most importent problems in the shift control strategy for DCT. The accurate control of oilpress in clutches is the core technology. Whereas this, it will be researched in this thesis,which is based on the"863"subject researched by automobile-engineering college of Jilin university and Jili automobile group, about one of the key technologies on DCT - control of oilpress in clutches. The main content includes:Chapter One expounds the workprinciple and characteristics as well as key technologies of DCT. DCT has two major characteristics: shift without anydiscontinuity of driving force and high efficiency. Key technologies include joint characteristic of clutch, shift control strategy and electronic control technology. Compared to other transpissions, it can be seen that DCT has outstanding advantages. It has a highly amplitude foreground, and is specialy fit for the actuality of transmission manufacture in China.Chapter Two first explains two work projects of DCT: simple middle shaft and double shaft, then points out that the latter one is more suitable for the design mode of automotive in modern times. As a following, the work system of DCT is also introduced, which mainly contains wet clutches with twisting dampers, a transmission collocated according to work principle of DCT and corresponded control systems. A total composing picture and a control system frame of DCT are also provided. The hydraulic system is diagrammatized detailedly. Hydraulic system mostly includes three parts: part of control of double clutches, part of control of shift machine and part of cooling. Two conceivable clutch systems, i.e.dry clutch system and wetclutch system, are compared. Through analyzing the characteristic of both we know that wet clutch is more furthersome for the control of DCT. Because it can transfer a large torque. The friction torque can be enhanced through adding frition patches. It can be disposed expediently. Friction patches are frayed equably. The interspace between patches has no use for a special adjustion during work. The torque it transfers can be easily controlled through control of oilpress in wet clutches. In this way, the torque that power train transfers can be easily controlled.Chapter Three first puts forward two indexes: friction work and wallop, which are used to evaluate the shift quality of DCT. The expressions of both are also calculated. Afterward, in order to analyze the process of shift, it establishes a shift dynamics model of DCT that consists four free bodies. Take the ascend shift process for example, it analyzes five phases of shift process. Through the analysis it's concluded that the output torque alters in different phase. The friction coefficient of patches wobbles. It bears on the speed difference of clutches at slip estate. In this thesis the static friction coefficient is initialized as a constant, and amethode to calculate its dynamic value is also provided for the following simulation .Chapter Four is comprised by follows: Focusing on that how to get the best changing rule of oilpress in clutches, it uses estate space to describe the shift process of DCT. According to the factors that influence slip result and wallop, it selects appropriate estate variables, then establishes an appropriate target function. Through choosing authority values properly, it abates the illogicality between them to some extent.Chapter Five first analyzes two shift rules of DCT: the best driving force shift rule and the best fuel efficiency shift rule. In order to control oilpress in clutches accurately, it decides to use fuzzy self-adaptive PID control strategy. Through fuzzy consequence it establishes fuzzy lookup-tables of PID parameters. After simulation analysis of this controller, it can be seen that it has a more extensive applicability and is more robust than a single PID control or a general fuzzy control. Then, all mathematic models of shift process are established for simulation. It simulates the shift process of DCT with the help of Simulink. Simulation results indicate that slip result and wallop are both abated through the shift control based on the fuzzy self-adaptive PID control strategy of optimization theory. The shift quality and riding comfort as well as lives of mechanical parts in power train are also improved, which is significative for the research of DCT shift-control technologies.
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