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

• within a control module;
• 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;
• controlling the intake air compressor to operate at a position that controls flow of intake air to the internal combustion engine in response to the compressor boost control command;
• and
• operating the internal combustion engine with the intake air compressor operating at the compressor boost control command, comprising maintaining exhaust pressure of the internal combustion engine at the predetermined exhaust pressure limit.

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

• within a control module;
• 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;
• controlling variable-geometry turbocharger (VGT) to operate at a position that controls flow of intake air to the internal combustion engine in response to the VGT position control command;
• and
• operating the internal combustion engine with the VGT operating at the VGT position control command, comprising maintaining exhaust pressure of the internal combustion engine at the predetermined exhaust pressure limit.