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Srinivasan, Krishnaswamy
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Modeling, Control, and Adaptation for Shift Quality Control of Automatic Transmissions

H G M Automotive Electronics-Gilbert Cardwell
Ohio State University-Kirti Deo Mishra, Krishnaswamy Srinivasan
Published 2019-04-02 by SAE International in United States
The parameters determining shift quality control in automatic transmissions are determined as part of the calibration of the transmission control. The resulting control system typically has three components: feedforward control, where the control output is determined before a gearshift; feedback control, where the control output is determined during the gearshift based on sensed feedback; and learning control (adaptation), where the feedforward or feedback controller parameters are modified after the current gearshift has ended and before the next similar gearshift begins. Gearshifts involving the same ratio change are referred to here as similar gearshifts, though such gearshifts may involve differences in other variables such as vehicle speed or engine torque. In most automatic transmissions, gearshifts are controlled by hydraulic clutches, and operating conditions for these clutches may vary widely, requiring a dedicated transmission controller involving significant calibration effort.In the current work, novel model-based methods are used to accomplish feedforward control of gearshifts, involving offline calibration of fill and torque phase control parameters and learning control of the fill phase. Towards this end, a physics-based model of…
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Estimation of Wet Clutch Friction Parameters in Automotive Transmissions

Ohio State University-Matthew Barr, Krishnaswamy Srinivasan
Published 2015-04-14 by SAE International in United States
In this paper, a new algorithm for the off-line estimation of wet clutch friction parameters is proposed for automotive transmissions, motivated by the usefulness of such an algorithm for diagnosing the condition of the clutch and transmission fluid in service. We assume that clutch pressure is measured, which is the case in dual clutch transmissions (DCT). The estimation algorithm uses measured rotational speeds and estimated accelerations at the input and output sides of a clutch, measured clutch pressures, and a simplified dynamic model of clutch friction to estimate the viscous and contact components of clutch friction torque. Coefficient of friction data is generated using the contact friction torque. A Stribeck friction model is fit to the data, and parameters in the model are then calculated by applying linear least squares estimation.The proposed estimation algorithm is tested using the simulation of a powertrain utilizing a DCT, where the clutch friction model incorporates a realistic level of fluid film squeeze dynamics. The algorithm is evaluated under ‘noiseless’ and ‘noisy’ conditions. In the ‘noiseless’ case, clutch accelerations and…
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Modeling and Simulation of a Shift Hydraulic System for a Stepped Automatic Transmission

The Ohio State University-Sarawoot Watechagit, Krishnaswamy Srinivasan
Published 2003-03-03 by SAE International in United States
It is well-known that the shift hydraulic system plays a major role in the operation of stepped automatic transmissions. The main functions of the hydraulic system are to generate and maintain adequate fluid pressures for transmission operation, as well as to initiate gear shifts and control shift quality. Therefore, quantitative understanding of the dynamic behavior of the hydraulic system is critical to the improvement of automatic transmission performance. This paper presents the development of a nonlinear dynamic model for the shift hydraulic system of a stepped automatic transmission. The model includes all necessary dynamics, namely, hydraulic line pressure dynamics, solenoid valve dynamics, pressure control valve dynamics, as well as clutch and accumulator dynamics. The model is developed and implemented using Matlab/Simulink®, and is validated against experimental data. The results confirm that the model predicts hydraulic system dynamic response accurately, the prediction being robust to variation of the operating condition.
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Transmission Clutch Pressure Control System: Modeling, Controller Development and Implementation

Ohio State University-Quan Zheng, Krishnaswamy Srinivasan
Published 2000-03-06 by SAE International in United States
This paper describes the modeling, controller development, and implementation of a transmission clutch pressure control system. A nonlinear analytical model for the clutch pressure control system is developed and implemented using Matlab/Simulink, and validated by experimental data. The dominant dynamics are identified via model analysis, and a linear model is derived for controller design. Openloop (feedforward) and closed loop (feedback) pressure control strategies are designed and implemented in a test setup. Experimental results show that the combined feedforward and feedback control gives superior performance as compared to feedforward control alone.
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