Method and system using fuzzy logic for controlling a cvt transmission

Abstract

According to the present invention, the driver's operation quantity and the vehicle running status are measured, the target value of speed ratio or the target value of revolution speed on the input side of the transmission is determined on the basis of the above measured values, and the speed ratio is changed using different algorithms (particularly fuzzy rules) on the basis of the magnitude of deviation between the target value and the actual value. Furthermore, when a vehicle has a continuously variable transmission, a change of at least one of the vehicle acceleration and the shaft torque of a drive wheel is predicted, the engine output torque is controlled on the basis of the prediction, and finite speed ratio characteristics or intermediate characteristics between finite speed ratio characteristics and continuously variable speed ratio characteristics are controlled for the continuously variable transmission. By doing this, speed ratio control stressed on stability is available when the absolute value of the above deviation is small, while speed ratio control stressed on rapid response and smooth acceleration variation is available when the absolute value of the deviation is large. Furthermore, a smooth acceleration feeling and a rapid acceleration response can be realized, the maneuverability is improved, and the driver can find pleasure in more speed ratio characteristics.