A Study on the Shifting Strategy for Automatic Transmission Vehicle in Downhill Driving

To solve the problems including the incidental up-shift of conventional automatic transmission vehicle in downhill driving, the kinetic characteristics of vehicle during coasting with clutch engaged are analyzed based on the braking characteristics of engine. On this basis, together with highway design regulations, the target reference speed and constrained gear position are determined, a shifting control strategy in downhill condition is proposed based on road slope information, and a driver-in-the-loop simulation experiment is conducted by using Matlab/Simulink and driving simulator. The results indicate that the shift strategy proposed can effectively solve the problems of conventional automatic transmission vehicle in downhill driving and embody driver's intent to a certain extent. It not only makes full use of the braking capability of engine, but also takes care of driving efficiency while ensuring driving safety, better meeting the requirements of automatic transmission vehicle in downhill driving.