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Abstract



Model Predictive Control of a drivetrain with a Starter/Generator


The aim of this Master Thesis is to control a vehicle with a Starter/Generator included in the drivetrain with the help of an on-line control method called Model Predictive Control (MPC). The controller is to be used as a cruise controller and attempts are made to lower the fuel consumption with the help of MPC. The control signals are the throttle angle and a current associated with the torque that can be obtained from the Starter/Generator. The reference signal is velocity. The control work is divided into two parts, linear and nonlinear MPC. For the linear MPC the vehicle model is firstly linearized and the obtained linear model is used in the making of the linear controllers. The controllers are derived for different criteria and around different working points, and tested on the nonlinear model. The following of the reference velocity is good, but it is not possible to directly influence the fuel consumption. To be able to cover a larger reference velocity range the linear controllers are combined in two different switching strategies, were a supervisor decides what controller to use in a particular instant. To be able to more directly influence the fuel consumption, nonlinear MPC is tried. A complete numerical solution would require substantial calculation time so a approximative method is used. The approximative method is tested for two different criteria, were one directly includes the fuel consumption. The approximative method does not give as good a result as the linear controllers with regards to the reference following. With regards to the fuel consumption the result is hard to interpret since the control values assume unrealistic values.

Zandra Jansson

2001

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