Engine control method using real-time engine system model

Details Engine control method using real-time engine system model Engine control method using real-time engine system model

1999-04-12

2001-01-23

Nguyen, Hoang (Department: 3748)

Data processing: vehicles, navigation, and relative location

Vehicle control, guidance, operation, or indication

With indicator or control of power plant

C701S105000, C701S108000, C123S406470, C123S406480, C123S406440

Reexamination Certificate

active

06178373

ABSTRACT:

BACKGROUND
This invention relates generally to internal combustion engines and more particularly concerns a method for generating engine calibration parameters in real-time using a mathematical model of the engine system and combustion process.
Internal combustion engines are designed and developed in several phases. At a minimum, the engine concept is assessed, the design is engineered, and the manufacturing issues are resolved. In the final phase of engine development, the engine is mapped and calibrated for optimized performance.
Engine mapping and calibration seeks to optimize the setpoints for fuel flow, airflow (including the amount of exhaust gas recirculation (EGR)), and spark ignition timing to balance the competing interests of achieving the lowest possible emissions, the best possible fuel economy, and satisfactory performance. The engine mapping and calibration process is both costly and time consuming. All potential combinations of a variety of engine operating parameters must be analyzed and associated to set points for airflow, fueling rate and spark timing. The result of the engine mapping and calibration process is a series of detailed lookup tables storing engine subsystem setpoints for these combinations of engine operating parameters. The resulting tables are stored in the powertrain control module (PCM) for use in engine control. For example, a desired EGR valve setpoint would be retrieved from the lookup table of values based upon the operating inputs of engine speed, load, and airflow, for instance.
One drawback to using calibrated look-up tables for engine control, however, is that the calibration tables are developed based upon assumptions for the engine operating environment such as the air quality and fuel grade. Thus, if the engine operating environment differs significantly from the assumed environment for which the calibration tables were developed, the engine control strategy will not be optimized. In such a case, the engine must be remapped and new calibration tables developed if the engine is to be optimized for its environment. In other words, a vehicle operating in a thin air environment such as a high altitude location may require different lookup table values than a vehicle in a very dry air environment such as a desert location. Indeed, most calibrated lookup table setpoints are actually compromised, rather than global optimized, to allow acceptable engine performance over a wider variety of operating environments.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an improved engine control method.
Another object is an engine control method which provides real-time calibration setpoints based upon a mathematical model of the engine rather than predefined setpoints based upon assumed environmental operating conditions.
According to the present invention, the foregoing and other objects and advantages are attained by a real-time control method for an internal combustion engine having a powertrain control module which includes a microprocessor and associated memory. The method includes the steps of storing a mathematical model of the engine system in the PCM memory and continuously monitoring a variety of engine operating parameters. From these inputs, the PCM generates optimized calibration setpoints for the intake air flow, fueling right, spark timing and EGR flow for the engine using the stored mathematical model. The setpoints are generated in real-time for every engine cycle, and the engine is then operated in accordance with the generated control setpoints.
In another aspect of the invention, the engine model includes submodels for fuel delivery, the in-cylinder processes, engine heat capacitance and cooling, engine friction, air flow, engine inertia, and the front-end auxiliary drive.
One advantage of the present method is optimized control setpoints for all engine operated environments.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.


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