Study On Speed Ratio Match And Control Of Palio Vehicle With CVT

With the living standards rising rapidly, more and more people have cars of their own. Statistics show that in China alone, there are more than 18 million cars produced and sold in 2010. The increase in the number of cars brings about the air pollution and gas shortage. Therefore, how to reduce vehicle emissions and the fuel consumption more effectively has being a common problem by all the countries.As an ideal transmission, continuously variable transmission can make the engine always operate in the most economical conditions. Thereby, it can reduce the vehicle's fuel consumption. So all the auto companies pay much attention on it, and it is one of the most important automatic transmissions now. The quality of the transmission control system determines the merits of vehicle performance, while the CVT speed ratio control is the core technology of the control system. Therefore, it is necessary to study the control of the speed ratio. And it will reduce the gap for the automatic transmission technology between domestic and foreign countries.Under the project financed by Automotive Engineering Research Institute in Nanjing, this paper carries out theoretical analysis, simulation analysis and test analysis on the target speed ratio and the process of the changing ratio for the Palio car. The results will be useful for the study on the control of the speed ratio for continuously variable transmission. And the road test fills the real vehicle test verification for the study on the process of the changing speed ratio. It will benefit the development of the continuously variable transmission control system for domestic.At present, the research for CVT in domestic and international includes transmission mechanism and its control strategy. With the development of the technology, CVT will be cheaper, and can transfer much more torque .The efficiency will also be increasingly, and it will be promising in hybrid vehicles in the future.The main research contents and outcomes are as follows in this paper:Based on the study of the basic structure of the metal belt type continuously variable transmission, this paper analyzes the working principle of the transmission mechanism for each stall. And then, it establishes the engine output torque model by the test data of the engine on the bench, and finds out the optimum economic and power speeds of the engine at different throttle percentages. After analyzing the Mathematical model for the transmission and whole vehicle, build the model of the vehicle using Matlab.The car often runs in non-steady state conditions. The results show that the engine characteristics are different when the car runs in the steady-state conditions and in the non-steady-state conditions. So this paper will divide the driving cycle conditions into steady-state conditions and non-steady-state conditions. And divide the non-steady-state condition into start, acceleration and deceleration conditions. The acceleration condition includes sudden acceleration and slow acceleration conditions. The deceleration condition includes general deceleration, wholly deceleration and braking conditions. For different driving conditions, it lists the corresponding formula for the target speed ratio, draws and analyzes the map of the ratio matching.Considering that the car often works in different driving conditions, and a set of parameters can only be applied to one condition for the conventional PID controller. The expert PID controller is applied to Automatic tuning PID parameters of control system. Simulation and analysis of the vehicle model on different conditions. The results show that the actual speed ratio can track the changing of the target speed ratio, which demonstrates the correctness of the model and the expert PID controller.According to the existing hardware and software equipment, the paper designs the test system. Take the road testing under the dynamic and economic mode on typical conditions, and obtain the data by dSPACE / MicoAutoBox. Analyze the changing of the vehicle speed, engine speed and the speed ratio on different driving conditions based on the test data. And then compares the results with the simulation. The graph shows that the simulation curves are at the same trend with the experimental curves, which further verifies the speed ratio model and matching diagram.