The Research Of Ramp Shift Strategy To AT Vehicle

Automatic shift strategy as the core technology of hydraulic automatic transmission, its accurate or not determines the performance of the AT exert. Adopts the traditional two parameters shift strategy cannot completely meet the requirements of the complex road conditions. At the same time also does not take into account the driver intention, and working condition of slope, witch the basic condition of the vehicle is working, will appear a series of problems. Such as when driving uphill easy appear shift cycle, reduce the stability and ride comfort of driving; Downhill road unexpected shift easily, to the driver operating the pedal control speed, increased the driver’s fatigue, at the same time, increasing vehicle parts wear and tear, reduce its service life. At present, some scholars both at home and abroad were designed based on three parameters of dynamic shift strategy, solve the traditional two parameters shift strategy most of the problems. But it is complexity of the three parameters shift rule set, and the hardware equipment demand is higher, it is difficult to meet the requirements of low-cost economy cars. Therefore, this paper designed a kind of relatively simple, based on the two parameter shift law, combining with the driver’s intentions, shift point correction shifting strategy. Overcomes the traditional two parameters under the condition of the ramp shift strategy show, at the same time have characteristics of simple structure and strong practicability.On the basis of analysis of the structure characteristics and working principle of AT, with the engine bench test data and the external characteristic of torque converter test data, calculate the joint work input torque Tb and output torque Twof the engine and the torque converter. According to the transmission speed ratio and the formula to calculate the vehicle speed and vehicle dynamics driving force curve. Combine two parameters shift characteristics, based on the throttle openingα and the speed v of the two parameter shift rule curve.Then analysis of working condition of vehicles driving dynamics, in view of the cycle shift of uphill condition and unexpected shift downhill conditions, considering the influence of driver intention during, proposed to modify the ramp shift point. To calculate coefficient, through fuzzy control algorithm, design the corresponding fuzzy controller in view of the uphill and downhill conditions, and set the throttle opening rate and the intensity of automatic respectively as the working condition of uphill and downhill condition. Last, develop the vehicle model witch combine with engine module, hydraulic torque converter module, reducer module, vehicle dynamic module, shift control module by matlab/simulink software. Simulated the two parameter shift schedule and fuzzy correction shift law in the condition of the uphill and downhill. Conditions, comparison the simulation results, validate the shift rule of the fuzzy correction is effective and feasible.