Optimal Matching Of The Heavy Truck's Transmission

Now road transport is the major means of transportation , and heavy-duty vehicles are the main tools of road transport. In recent years, with the rapid development of industries which is closely related to heavy-duty vehicles market (for example coal, steel, ports, cement, food, petroleum, fixed investment, etc), the number of the heavy-duty vehicles is growing rapidly, which increase the consumption of oil resources. The increase demands for more energy supply. So higher request of the vehicles property is set up by the users, especially the fuel economy.Drive transmission is an important component of the power train. Following with the increasing density of urban vehicles, automatic transmission has become an essential equipment of motor vehicles because it can change the speed easily and the best speed ratio can be achieved. It's important to study the match of transmission, which have an effect of the vehicle's power and fuel economy. In the design of the vehicles, the optimal match of the engine and power train is a reasonable choice of transmission parameters; In the use of the vehicles, the optimal match of the engine and power train is a reasonable selection of the appropriate gear ratio or transmission parameters. So that the engine can work in its ideal working areas.In this paper, the transmission of the heavy-duty vehicles is matched with the engine. The transmission gear ratio is optimized; A gear-shift controller is established with fuzzy control theory, which can realize automatic gear shifting according to the change of the speed and throttle opening. Specific studies are as follows:The Optimization of the Transmission Ratio(1) On the basis of the conclusion of the experience at home and abroad, the evaluations of power performance and fuel economy are established, which includes the maximum speed, acceleration time, the biggest climb, the drive power loss rate, 100 kilometers speed fuel consumption and multi-cycle fuel consumption. These indicators reflect the degree of the match of the power train and the exertion of the engine. They also reflect the difference of the engine working conditions between actual vehicle driving cycle and ideal conditions, suggesting the potential and possible ways to improve power train.(2) The mathematical model of the engine external characteristic and universal characteristics is established respectively using least-square method and surface fitting method. To a certain range of accuracy required, analog calculation can meet the requirement of analysis of the vehicle's power performance and fuel economy. The correct establish of the engine characteristics is the basis for analyzing the vehicle's power performance and fuel economy.(3) The optimization mathematical model of the transmission is established. Choosing the weighted value of driving power losing rate and the 6-cycle fuel consumption as the objective function; Using the dynamical factor of the first gear,the maximum speed,the biggest climb of the first gear,coefficient of adhesion for the constraint condition. The transmission ratio is optimized by Matlab optimization toolbox. The comparative analysis of the vehicle's performance figures before and after optimization shows that the vehicle's power performance and fuel economy are all improving to some degree.Design of the optimization programBased on the optimization of the transmission ,the program is compiled and the visualization interface is developed, which greatly shorten the design time,to a large extent to improve the working efficiency and provide help for other designers.The establishment of the fuzzy shift controllerTwo-parameters shift schedule is established. The vehicle's automatic transmission shift is achieved by the fuzzy control which can determine the shift characteristics according to the different driving cycle. It can make the shift match with the engine characteristics. The fuzzy shift controller is established by determining the membership function of the input and output variables, as well as the corresponding control rules. It can associate a variety of input information with the selection of fuzzy control block. In most cases the vehicle are able to correctly identify the best of gear and automatically shift in accordance with the wishes of the driver. In Matlab/Simulink environment, the establishment of vehicle automatic transmission simulation system is supported to verify the effectiveness of the fuzzy shift controller. Theoretical analysis and simulation results show that the system design is feasible.