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Nowadays, most automatic transmissions of passenger car adopt an electronically controlled shifting mechanism to enhance the driveability and fuel economy. As the performance requirement, especially on shift quality, of automatic transmission become rigorous in recent years, power train engineers have made an great effort to improve ride comfort during shift. EF-automatic transmissions for FWD passenger car, installed in Hyundai's EF-sonata model, are originally developed by Mitsubishi Motor Company and equipped with full electronic control system. Its major design features are that clutch-to-clutch shifting mechanism is employed for simplified construction and lighter weight and four independently operated PWM solenoid valves control the applying pressure on the friction elements during shift.

Since 1980s, the electronic control units of automatic transmissions have been greatly advanced to make smooth gear shifting and improve fuel economy. Along with it, the solenoid valves as electro-hydraulic actuators have been rapidly developed which have high pressure and large flow capacity. In these days, it is not an expensive solution to adopt more electro-hydraulic actuators to get the better performance of the automatic transmission. This paper introduces a new scheme of full electronic control system, direct active shift control, using the proportional control solenoid valves to control the pressure of each friction element independently and without any passive hydraulic or mechanical component. At first, it reviews the structures of widely used control systems from the old-fashioned to the modern. Next, the concept of the direct active shift control scheme is introduced and the performance of the actuators discussed.

In this paper a computer simulation model for control system design of gasoline engines with an automatic transmission is presented. A modular programming approach has been pursued, and MATLAB/SIMULINK has been utilized as a programming environment. Engine/transmission systems are analyzed in the object-oriented fashion. Thus, easy construction of various computer models by assembling various objects is possible. An object in this paper represents a physical part, an equation, or an algorithm. The top level in the powertrain model consists of three classes: an engine, a transmission, and a driveline. Each class is designed to perform by itself. The construction procedure of a typical powertrain model together with supplementary explanation is demonstrated. It is expected that the whole program and individual class constructed in this paper are useful for the automotive engineers who design a new engine/transmission system and/or modify an existing system.

As most of today's automatic transmissions adopt a electro-hydraulic control system, the role of electronically controlled solenoid valves occupies an important position. This paper presents a dynamic modelling technique of a proportional control solenoid valve(PCSV) for automatic transmissions in terms of the system identification theory, and analyzes the dynamic characteristics of the PCSV in frequency domain. Also we find that there are good matches between the nonlinear dynamic simulation results and the experimental data.