| In twenty-first Century, cars have already walked into thousands of households, and thetype of automatic transmission vehicles is diverse. In today’s configuration, the hydraulicautomatic transmission is most widely used (referred to as AT). In the running process ofthe vehicle, the use of hydraulic automatic transmission can effectively reduce shiftingimpact, and reduce the dynamic load of transmitting mechanism, making the automobilemore powerful, economical, comfortable and convenient. It is the current mainstream ofautomatic transmission.Research and development of hydraulic automatic transmission has importanttheoretical significance and practical value in promoting the development of domesticautomobile industry and technology progress. With the popularization of cars, people paymore attention on riding comfort and safety. To improve vehicle performance, intelligentshift emerges. Therefore, intelligent shift control has become the main direction of thedevelopment ofAT.The vehicle driving environment is intricate, and ramp and low adhesion is a basic roadcondition in northern China. However, in the ramp shift, if the car still follow the normalshift schedule, it will greatly reduce their work performance, and even lead to security risks.Such as when uphill, the increase of the slope resistance can easily cause a shift cycle,affecting the vehicle’s power, and reducing ride comfort; whereas, the vehicle willaccidentally upshift when it continues to accelerate downhill, frequently stepping on thebrake will cause the brake system’s life loss.Normally,the vehicle accelerating ability on low-adhesion road is constrained by two factors, namely, the output power of the engine and the adhesion of the road. When vehicles are traveling on low-adhesion surface, the latter factor would be more significant in the effect.Under this circumstance,tyres’ excess trackslip would reduce the traction which affect theaccelerating ability, meanwhile reducing the stability. Thus, this essay focused on the vehicle shifting method on rampway, and the shifting controlling on low-adhesion surface. 1. On this basis, the AT automatic transmission control system is studied. We researchthe input and output characteristics of the engine and the torque converter’s joint work, andwe get the output and input characteristic properties.2.In view that the shifting easily occures uphill,analyze the dynamic characteristics ofvehicle driving of the ramp.In view of circulation phenomenon and problem of accident shifting on downhill road,correction scheme on shift time when uphill and downhill is proposed.Then, according to the fuzzy theory, we develop the rules to control the output,which isbased on that not only the road slope, throttle change rate and braking strength for the control variables, but also the above, downhill shifting the time to be corrected; the fuzzy controller with the vehicle on the downhill, shifts the condition time to be corrected.3. To establish the vehicle dynamic model and the ramp shift model of fuzzy control. Useing the fuzzy shift controller to output the vehicle on, traveling downhill upshift, downshift point and running gear by inputting the characteristics of AT and the basic shift rule in thecorresponding module. Bys were compareing the result to the AT shift fuzzy simulation before and after the amendment, the feasibility of the AT vehicle ramp shift strategy of fuzzy correction and effectiveness of the proposed is validated.4. Analyze low adhesion road driving conditions, and introduce the low adhesionroad‘s recognition method. Simulate the ice snow road by using vehicle simulator, andcollect condition data when drive on the low adhesion road conditions, draw curves, analyzeand verify the feasibility of the low adhesion road‘s control method. |
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