Study On Gear Shift Control For AMT Vehicle Based On Road Environment

Automobile automatic transmissions are mechatronic products with the continuousdevelopment of electronic and automatic technologies, by which drivers’ fatigue andwork intensity can significantly be reduced. Automatic Mechanical Transmission is anew version based on the improvements of a manual transmission. WithTCU(Transmission Control Unit) and actuator, AMT can accomplish the control ofclutch separation, combination and gear shifting automatically. Simple structure, highefficiency, low cost and the good production inheritance which particularly suitable forChina’s current situation all makes AMT focused in domestic development of automatictransmissions. Traditional shift strategies can only perform optimally in one conditionand have a poor adaptability with different kinds of road conditions, which affect theperformance of AMT cars directly. This paper focuses on the key issues of AMT gearshift strategies in different road environments, thus the following aspects are analyzedand studied:①Based on the analysis of AMT powertrain, the driveline dynamics simulationmodels are established, including engine numerical model, clutch model, transmissionand final drive model, wheel and vehicle driveline model. These models lay thefoundation for the gear shift strategy development and simulation.②Based on vehicle parameters and engine experimental data, the optimal powershift strategy and economy shift strategy are formulated,thengives a simple analysis ofits environmental adaptability. Based on the analysis of shifting process, shift qualityfactors and control objectives are analyzed. After that shifting process simulationanalysis for clutch control is carried on.③According to the characteristics of a car under low adhesion state, this papergives a brief introduction of traction control methods. In the analysis of thecharacteristics of a car under low adhesion state, the low-adhesion road identificationmethod is formulated. By traditional shift strategies, there may be problems ofexcessive wheel slip under low adhesion state. Thus the throttle opening control andgear intervention strategy as well as amendments of shift law on large throttle openingare used to solve these problems. The control method is simulated by Matlab/Simulink.The simulation results show that this method can effectively inhibit excessive wheel slipand improves acceleration and stability. ④Based on the analysis of problems in uphill and downhill condition bytraditional shift strategies and identification of the current slope value by calculatingvehicle load, the shifting strategies for uphill and downhill are formulated. Based onMatlab/Simulink, these shifting strategies are simulated. The results show that uphillshifting strategy can effectively solve shift circulation problem and downhill shiftingstrategy can give a fully use to the initiative engine brake torque.