| Nowadays, the energy crisis and environmental pollution has increasingly become the subject of attention, the car is a source of oil consumption, at the same time it's emissions are urban air pollution sources.Therefore, when we consider the energy crisis and environmental pollution problems to be taken seriously, it is clear that we need to seek the solution from the performance and the use of motor vehicles. In addition, in the large and medium-sized cities,traffic congestion is worsening day by day, people waste their life in creeping traffic, along with the mood of anxiety, it's a serious impact on people's work efficiency and quality of life.More and more families possess cars because of there improving income, and this makes the problems mentioned above more serious. At this stage, a reasonable program to solve the above problem is to develop pubilc transport, and encourage everyone to take the trip by more efficient public transport vehicles.Public transport vehicles because of its operational needs, and in the process of moving the frequent starts and stops, bus drivers take a long time as a chauffeur driving operation. And public transportation vehicle more passengers.Therefore, starting to reduce driver fatigue and improve driving safety and comfort point of view, obviously the automatic transmission is a reasonable choice of public transport vehicle powertrain. The automatic transmission shift strategy is the law of the automatic transmission gear the vehicle was performed according to the change of shift parameters of the gear change. The formulation of the shift schedule is a key link in the development process of the automatic transmission, it is good or bad, directly affect the car's dynamic economy, emissions, comfort, and adaptability to the environment. The shift schedule should be formulated according to the specific situation to determine the shift strategy, driving parameters such as shift quality requirements and the availability of vehicles. Shift strategy can be divided into a single parameter, the shift of two parameters and three parameters. Power Shift and economic shift schedule in accordance with the acceleration of the car or the fuel consumption performance can be divided into. Automatic transmission shift strategy in public transport vehicles to shift strategy and validated through the modeling and simulation.Site parking, traffic lights to make public transport the vehicle process contains more start, acceleration, braking, deceleration and other driving conditions, increase energy storage in the vehicle driveline components to absorb the kinetic energy consumed in the brake deceleration, and release the energy to assist the vehicle started to accelerate when the vehicle started to accelerate.This will not only improve vehicle efficiency, reduce fuel consumption, but also improve the dynamic performance of the vehicle. In this paper, additional bus vehicle powertrain components of the hydraulic accumulator, and through theoretical analysis and calculation for reasonable parameters, and then through the modeling and simulation to verify its performance.The subject combined with enterprise project "XQ6102SH2 urban bus automatic transmission development test", the project for the FAW (Wuxi) Bus plant for city buses XQ6102SH2 equipped with self-developed four-speed automatic transmission, including supporting software and hardware development and vehicle Experimental study. Paper as follows:(1) analysis and the establishment of a mathematical model of the vehicle powertrain including the engine, torque converter, automatic transmission model.(2) analysis and the establishment of the mathematical model of the hydraulic energy storage device.(3) shift strategy:shift in accordance with the selected number of parameters, the shift strategy can be divided into a single parameter, the shift of two parameters and three parameters. Power Shift and economic shift schedule in accordance with the acceleration of the car or the fuel consumption performance can be divided into. This paper analyzes the automatic shift schedule, on the basis of several typical shift schedule, test analysis through the characteristic parameters of the engine, the engine load rate as the shifting parameters of the shift schedule. According to the characteristics of public transport vehicles operating conditions, the development of optimum power for the test car and the best economic shift schedule, shift schedule based on the economic dynamic factor. Special conditions buses should be used to shift strategy.(4) the establishment of a simulation study based on the vehicle simulation model in Matlab/Simulink, and shift control strategy. Shift control strategy, simulation results show that the proposed comprehensive shift control strategy based on economic power factor has a better economy, dynamic performance.(5) Control of torque converter lockout:torque converter is the ideal starting components in the vehicle, the torque converter when the car started torque ratio that car a smooth start. And hydraulic transmission characteristics of the engine and transmission, isolation, and to facilitate the automatic transmission automatic transmission. However, the hydraulic efficiency of the transmission is far lower than the mechanical transmission, torque converter applications in modern vehicles are equipped with a locking clutch for the completion of the vehicle starting to reach a certain speed, the torque converter input pump wheel and the output turbine lock as a whole, variable hydraulic mechanical transmission, the transmission in order to improve its transmission efficiency.Torque converter lockout control strategy was proposed for the study of public transport vehicles., Matlab/Simulink vehicle simulation model of the typical conditions of a torque converter lockout control simulation, the simulation results show that the implementation of the control strategy can be a good torque converter locking operations, improve vehicle fuel economy performance.(6) Application AMESim software to establish a parallel hydraulic hybrid vehicle model, the main structural parameters of the hydraulic accumulator devices are optimized through the simulation study of the typical operating conditions.(7) The design of the automatic transmission electronic control system, the development of the automatic transmission control software. Based on the Freescale MC9s12XDT256 single-chip design of the electronic control unit for automatic transmission and hydraulic accumulators. First analysis of the specific design requirements of the electronic control unit, and then according to the design requirements of the design and development of the electronic control unit, electronic control unit hardware and software design features. The main innovation is the first proposed application of the engine electronic control unit broadcast to the CAN bus engine percentile torque as a parameter of the characterization of engine load rate, and economic momentum factor was developed based on this parameter change file rule, in order to be able to better coordination of economic performance and dynamic performance of the vehicle, especially suitable for such as bus load range, and frequent change of vehicles.
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