Simulation based calibration of turbo-charger boost control

[摘要] Electronic engine control systems utilise tables, or maps, of data to determinethe set-points of the various actuators on the engine and to calculate the valuesof variables that cannot be directly measured. To ensure accurate control of theengine processes the values in these maps have to be accurately calibrated for theparticular engine being controlled.Due to the complex interaction of the various systems in the engine it is becomingmore and more difficult for human calibration engineers to be able to take allthe effects of changes to a particular parameter into account. This problem is madeworse by increasingly strict emissions regulations and performance demandsfrom the customer. The process of calibrating the maps in an Electronic ControlUnit (ECU) is also very resource intensive since it involves taking a test engineinstalled in an engine test cell to every operating point on the various maps andadjusting 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 asimulation based calibration system. The proposed system would use an accuratemodel of the engine to simulate the effect of various map values on the engineresponse. This data would then be used to find the map values that would enablethe engine to deliver a desired torque curve. In the case where it is not practical touse engine simulation the system would be able to process a database created bytesting an actual engine. This testing could also be automated.To achieve this aim the AutoCal program was created. This program can managea 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 databasesubject to user defined operating constraints and find calibration values thatwill deliver a desired torque curve. It can also be used to evaluate and processdatabases created by engine testing.To provide the data required for the development and testing of the AutoCalprogram, a naturally-aspirated engine was turbo-charged and tested at variousoperating points. The resulting data was used to calibrate and validate a modelof 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 controlthe turbo-charger wastegate and ignition timing of the test engine. Work waslimited to the full load operating region and fixed Air/Fuel Ratio (AFR) valueswere used.The project showed that simulation based calibration can be used to calibratecontrol system maps once an accurate model of the engine being controlled hasbeen created. Very useful insight was gained into the process of building, testingand modelling a turbo-charged internal-combustion engine and calibrating modernelectronic engine control systems. The end result is a useful engineering toolwith 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 performancesubject to user-definable constraints. This can be done using results fromsimulation or physical engine testing in the case of simulation tools not beingavailable.² Providing the data required when calibrating the engine model used duringsimulation by processing and displaying the outputs of the simulation programcompared 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 approachto engine control system calibration.

[发布机构] Stellenbosch University