Application of Systems Modeling and Simulation in the Discrete Ratio Automatic Transmission Calibration Process for an Automobile

This paper describes the application of systems modeling and simulation to the process of calibrating shift schedules for an automatic discrete ratio transmission in an automobile. A simulation tool capable of predicting the effect of transmission calibration changes on vehicle performance, fuel economy, and shift consistency and busyness is presented. The simulation tool includes a powertrain system model in which the physically based elements were developed using Modelica/Dymola and the functionality of the electronic transmission controller was realized using MATLAB/Stateflow. The complete powertrain system model is simulated in the MATLAB/Simulink environment and has been validated against data obtained from vehicle tests. The simulation tool also incorporates a graphical user interface to facilitate its use by calibration engineers as an integral part of the transmission calibration process: The paper discusses the role of the simulation tool during two phases of the calibration process: the initial design of shift schedules; and in-vehicle development of shift schedules. The results of a back-to-back comparison between the traditional, experimentally based transmission calibration process and a revised process, centered on use of the simulation tool, demonstrate that applying the simulation tool as an integral part of the calibration process can save a significant amount of calibration engineers and vehicle testing time.Copyright © 2003 by ASME