Simulation based calibration of turbo-charger boost control
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2007.
Electronic engine control systems utilise tables, or maps, of data to determine the set-points of the various actuators on the engine and to calculate the values of variables that cannot be directly measured. To ensure accurate control of the engine processes the values in these maps have to be accurately calibrated for the particular engine being controlled. Due to the complex interaction of the various systems in the engine it is becoming more and more difficult for human calibration engineers to be able to take all the effects of changes to a particular parameter into account. This problem is made worse by increasingly strict emissions regulations and performance demands from the customer. The process of calibrating the maps in an Electronic Control Unit (ECU) is also very resource intensive since it involves taking a test engine installed in an engine test cell to every operating point on the various maps and adjusting the map values until the desired response is achieved. The aim of this project was to develop a solution to this problem in the form of a simulation based calibration system. The proposed system would use an accurate model of the engine to simulate the effect of various map values on the engine response. This data would then be used to find the map values that would enable the engine to deliver a desired torque curve. In the case where it is not practical to use engine simulation the system would be able to process a database created by testing an actual engine. This testing could also be automated. To achieve this aim the AutoCal program was created. This program can manage a commercial engine simulation code to create a database of the effect of various calibration values on the engine response. It can then evaluate the created database subject to user defined operating constraints and find calibration values that will deliver a desired torque curve. It can also be used to evaluate and process databases created by engine testing. To provide the data required for the development and testing of the AutoCal program, a naturally-aspirated engine was turbo-charged and tested at various operating points. The resulting data was used to calibrate and validate a model of the engine created and simulated with the WAVE software package from Ricardo. The project was focused on finding calibration values for the maps used to control the turbo-charger wastegate and ignition timing of the test engine. Work was limited to the full load operating region and fixed Air/Fuel Ratio (AFR) values were used. The project showed that simulation based calibration can be used to calibrate control system maps once an accurate model of the engine being controlled has been created. Very useful insight was gained into the process of building, testing and modelling a turbo-charged internal-combustion engine and calibrating modern electronic engine control systems. The end result is a useful engineering tool with the following functions: ² Automatically simulating the effect of various control inputs on engine performance. ² Determining the correct calibration settings to deliver the desired performance subject to user-definable constraints. This can be done using results from simulation or physical engine testing in the case of simulation tools not being available. ² Providing the data required when calibrating the engine model used during simulation by processing and displaying the outputs of the simulation program compared to test data. ² Plotting any test or simulation results in a format configured by the user. Using this tool facilitates a more structured and less resource intensive approach to engine control system calibration.
Imported from http://etd.sun.ac.za April 2010.