Slope Shift Strategy For Automatic Transmission Based On Fuzzy Rectification

After development over half a century, Automatic Transmissions in cars havedeveloped into various forms. The Hydraulic Automatic Transmission (AT) withelectronic control is most commonly seen in modern cars, which can automatically selectsproper shift-level in accordance with the throttle opening degree and velocity of thevehicle, simplifying driving operation and reducing driver fatigue. With improvement ofautomotive technology and living standard in social development, people have no longerbeen content with simple convenient operation on the vehicle. Instead, its comprehensiveperformance including comfort and safety is attached more and more importance. Theintelligent shifting control is becoming one of the main trends of AT.Vehicles always run under complex environment and states, not excepting slope road asone of the typical driving conditions. On the slope-road drive, however, many problemsoccur if still applying shift schedules under flat roads and stable conditions, thusdecreasing performance of the vehicle and raising safety hazard. The increase in graderesistance easily leads up to shift cycle when driving uphill, which has a great affect onthe drawing power, resulting in climbing hard or climbing failure. Meanwhile, it willexacerbate quick wear of the transmission system and reduce driving comfort. Whendriving downhill, the vehicle will execute the up-shift selection after continuousacceleration. Accordingly, frequent brakes will also decrease the life of the braking system,and even lead to the phenomenon of overheating fate that endangers traffic safety. Aimedat those problems, the slope shift strategy for automatic transmission based on fuzzyrectification is established in the paper.1. On the basis of AT’s construction as well as working principles, the joint operatinginput and output points were achieved and plotted through torque properties of the engineand original characteristics of the torque converter(TC). Based on related data such astransmission ratio of the drive system, the corresponding driving force and velocity werecalculated, on the foundation of which, the basic up-shift and down-shift schedules withtwo parameters, namely, speed and throttle opening, were set according to driving featuresof the vehicle.2. At the same time, analyses on the slope-road driving characteristics were conductedand corresponding slope-road shift solutions were put forward with regard to differentoperating behavior and driver intention. Subsequently, influential variables including roadgrade, throttle variation ratio and brake intensity, as well as fuzzy control rules were set inthe slope-road fuzzy shift controller, which was designed based on fuzzy theory with Fuzzy Logic toolbox to output rectification coefficients used to rectify shift points underuphill and downhill driving conditions, in order to achieve a better effect of shift control.3. Ultimately, the power train model, vehicle dynamic model and fuzzy shift modelwere built under the environment of Simulink with imported basic shift schedule andfuzzy controller, simulating uphill and downhill driving conditions and outputting shiftpoints and the gear position. The simulation results have verified the feasibility andeffectiveness about the proposed slope shift strategy for automatic transmission based onfuzzy rectification.