Analysis of Torque Converter Dynamics,”

ABSTRACT A good understanding of the torque converter dynamic behavior in a wide range of its operation gains the understanding of overall power train dynamic behavior, and facilitates design of different torque converter and power train control and estimation strategies. A detail analysis of the torque converter dynamics based on the linearized "static" and dynamic torque converter models is presented in the paper. The analysis results in simplified linearized torque converter models convenient for control and estimation purposes, and yields a clear insight to the torque converter capability of damping the power train vibrations. INTRODUCTION Present automotive power trains with automatic transmissions are usually equipped with torque converters. The main advantages of the torque converter are damping of disturbances generated either on the engine or wheel side, and torque multiplication during vehicle drive away phase. The torque converter is usually modeled by using the wellknown capacity fbctor/torque ratio vs. speed ratio steady-state curves [1,2,3]. This static torque converter model has been proven to be adequate in the t?equency range up to 10-20 Hz (at the idle impeller speed) [2,3]. However, the higher frequency range may be of interest for the analysis of disturbance damping, and tbr simulation, estimation and control of highfrequency power train dynamics during throttle steps and gear shitts. In this high-frequency range, the torque converter dynamics due to fluid and stator dynamic effects should be considered. A dynamic torque converter model for operations below the coupling point has been proposed in [3]. Experimental validation of the model, and numerical analysis of its frequency response have been presented in the same paper. The model extension for operations above the coupling point (including the coast drive mode) has been discussed in [2]. By using th