Modeling and control of powertrains with stepped automatic transmissions

This dissertation addresses the modeling and control of automotive powertrains with emphasis on stepped automatic transmissions. An extensive survey of the state-of-the-art of modeling and control issues with emphasis on automatic transmission is provided, the survey indicating the need for improved modeling and control of powertrain systems, especially the need for integrated powertrain control.; Development of model-based approaches to integrated engine-transmission control design offers the potential for addressing more demanding control applications and significantly greater gains. Simulation models of the automatic transmission shift process with varying levels of complexity, suitable for dynamic response simulation, controller design and validation, are implemented using Matlab/Simulink. Linearized models of transmission dynamic response during the inertia phase of a gear shift are obtained directly from the Simulink block diagram.; Closed-loop shift control algorithms for the inertia phase of a gear shift are developed based on these linearized models and implemented in the powertrain simulation. An open-loop control strategy for the torque phase of a gear shift is developed and shown to be effective in reducing the torque drop in the torque phase. The results indicate the ability of integrated engine and transmission control to achieve satisfactory shift quality.; Powertrain neutral idle control improves fuel economy in urban driving and minimizes the engine vibrations transmitted to the driveline. Neutral-idle control requires fast and smooth application of the forward clutch in coordination with engine control functions. Understanding of pressure control system dynamics is essential to devise a control strategy for the neutral-idle process, as well as for other shift control applications such as clutch-to-clutch control. Detailed analysis of the dynamic response of a clutch pressure control system resulting in a nonlinear simulation model is presented and validated by experiments. Closed loop control of clutch pressure using feedforward plus feedback control is implemented in a test setup. Experimental results show that clutch pressure can be accurately controlled.; The formulation of the powertrain neutral-idle control problem is presented. A multivariable control strategy involving coordinated engine and transmission control is developed based on quantitative models of powertrain dynamic responses. Simulation results show that satisfactory neutral-to-first gear shift quality is achieved. neutral-to-first gear shift quality is achieved.