Method and apparatus to operate internal combustion engine employing an intake air compressor

Method for limiting intake boost pressure in an internal combustion engine including an intake air compressor, comprising

• providing a compressor boost signal;
• determining an exhaust based compressor boost limit as a function of a predetermined exhaust pressure limit;
• when engine exhaust pressure exceeds said predetermined exhaust pressure limit, determining a compressor boost control command as a function of the compressor boost signal, a minimum boost setting, and said exhaust based compressor boost limit;
• when engine exhaust pressure does not exceed said predetermined exhaust pressure limit, determining the compressor boost control command as a function of the compressor boost signal, said minimum boost setting, and a maximum boost setting;
• and
• controlling the intake air compressor in response to the compressor boost control command.

Method for controlling intake airflow in an internal combustion engine including a variable-geometry turbocharger (VGT), comprising,

• providing a first VGT position signal;
• determining a second VGT position signal comprising
• employing an inverse VGT model in feed-forward operation to determine a modeled VGT position signal based upon a predetermined exhaust pressure limit, and
• employing a feedback loop including a signal correction to said modeled VGT position signal based on PID processing of the deviation of engine exhaust pressure from said predetermined exhaust pressure limit;
• determining a VGT position control command based upon the first compressor boost signal and a limit comprising said second compressor boost signal when engine exhaust pressure exceeds said predetermined exhaust pressure limit and a maximum boost setting when engine exhaust pressure does not exceed said predetermined exhaust pressure limit;
• and
• controlling variable-geometry turbocharger (VGT) in response to the VGT position control command.