Optimization and control of feed and transfer pumps

Abstract: A new low pressure fuel system implementation for Scania’s trucks is being investigated. The main challenge consists in exchanging the mechanical pump with electrical pumps. The electrical pumps must then be controlled to supply exactly the demanded amount of fuel at the required pressure. System redundancy allows a lot of degrees of freedom influencing the final performance. This thesis studies the factors influencing system’s performance to design a controller that enhances its behavior. The physical basis of the elements in the system are investigated and stated with that purpose. The system is analyzed and the output pressure and tank level are controlled by a LQG regulator giving successful results in reference tracking. Integral action is included for disturbance rejection and the states are estimated to overcome quantifications and noise from the signals. The disturbance rejection performance is improved by extending the regulator with a Smith Predictor for time delay compensation and including information about the engine mass-flow demand. The control actions are minimized by the tuning of the controller in order to extend component’s life. The controller includes different modes for when an external action should be input e.g., when a diagnosis test must be run. The optimization of free set-points is discussed and holistic criteria from experience is set. The result is that the system endurance is enhanced by running only two pumps when one does not provide higher efficiency. Results show that different pumps should be chosen in the final design for an improvement of the global efficiency. Future work will consist in implementing the resulting controller in the real system built with actuators selected accordingly to the optimization results.