Study On Ratio Control Of Continuously Variable Transmission System Under Throttle Opening Dynamic Change

Since continuously variable transmission (CVT) was first equipped in automobile, more than millions of cars have been equipped with CVT. As an ideal transmission system for automobile, CVT plays an important role for matching engine and drive load. The vehicle performances are improved and the emissions are decreased by controlling CVT ratio to make engine running along the ideal operational line. Study on control of ratio of metal pushing V-belt continuously variable transmission system has important theoretical and engineering value. Theoretical and simulated researches of dynamic characteristic and control of ratio of CVT have been carried out under the project financed by Chongqing science and technology Council. This paper involves followed content:(1) Based on the engine experiment, torque and oil consumption model of engine are established. The optimum economy and performance curves are put forward. Speed ratio control model of CVT is established which can realize the control of engine operation along target line. A practical self-adaptive fuzzy controller is designed.(2) Based on Primitive characteristic of torque converter, mathematic model of automatic vehicle system with torque converter as a starter and metal pushing belt CVT as a transmission equipment (Dual state CVT vehicle) is established. The system of Dual state CVT vehicle is simulated by using different control methods for vehicle standing start.(3) Based on the steady mathematic model of continuously variable transmission system, dynamic characteristic of CVT under normal control method is analyzed and the simulation of vehicle is found for speedup and speed-down.(4) Based on dynamic analysis of CVT, the influence of stand-by power is considered, and the formulae of CVT ratio derivative is found by calculation. The ideal CVT ratio derivative figure is found by Matlab simulating for vehicle speedup and speed-down. The actual CVT ratio derivative figure is found by considering the hydraulic pressure system.(5) The CVT speed ratio control method to improve the engine performance is proposed by considering the powertrain response lag. On the basis of model of CVT simplified, simulation model of vehicle is established. It makes the vehicle work according to the two strategies which are repaired with response lag or not in simulation. The fuel economy is estimated by fuel consumption of a ten-cycle.