Design and analysis of an adaptive λ-tracking [lambda-tracking] controller for powered gearshifts in automatic transmissions

To meet the increasing goals in vehicle fuel efficiency, a number of measures are taken in automotive powertrain engineering, such as the creation of hybrid powertrains or the increase in gear ratios. This development leads to more complex powertrain systems, such as automatic transmissions. At the same time, the need for complex control systems is increased. Automatic transmissions are controlled by an electro-hydraulic control unit that governs all operations such as gear shifting and starting. Since open-loop control is the predominant design, most of the operations have to be calibrated manually. Thus, a large number of calibration parameters have to be tuned individually for each combination of engine, transmission and vehicle model. This process is very time-consuming and costly. Hence, it would be advantageous to reduce the need for calibration by reducing software complexity while maintaining functionality and performance. The goal of this thesis is to replace parts of the control software responsible for conducting the gearshifts that require extensive tuning by implementing control systems that have no need for calibration: adaptive high-gain lambda-tracking controllers. In order to obtain the control parameters, i. e., the feedback gains, without calibration, an adaption law is implemented that continuously computes these parameters during operation of the controller. Thus, calibration is no longer needed. Since the system has to be high-gain-stabilizable, an extensive system analysis is conducted to determine whether an adaptive lambda-tracking controller can be implemented. A nonlinear model of the clutch system dynamics is formulated and investigated. As a result, high-gain stability is proven for the system class and validated in simulation. The devised adaptive controller is implemented into the control software running on the series production transmission control unit. Extensive simulations with a comprehensive vehicle model running the extended transmission software are conducted to design and to test the adaptive controllers and their underlying parameters during transmission operation in order to evaluate the control performance. The control software containing the adaptive controller is then implemented in two distinct vehicles with different automatic transmissions equipped with series production control hardware for the purpose of hardware experiments and validation. The resulting reduction of calibration efforts is discussed.