System and method for determining engine control parameters based on engine torque
First Claim
1. A method for determining engine control parameters based on a requested engine brake torque, the method comprising:
- determining a value representing engine losses based at least in part on the requested engine brake torque;
combining the value representing engine losses with the requested engine brake torque to determine a desired engine combustion torque;
modifying the desired engine combustion torque based on a desired value for at least one engine operating parameter;
determining at least one engine control parameter to control air mass delivered to at least one cylinder based on the modified desired engine combustion torque.
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Abstract
A system and method for determining control parameters for an engine include modifying a first engine torque based on estimated losses associated with a previously determined desired engine load to determine a second engine torque, modifying the second engine torque based on a desired ignition angle and air/fuel ratio to determine a third engine torque, determining a desired engine load based on the third engine torque, and converting the desired engine load to at least one engine control parameter. The invention recognizes that the transformation between torque and airflow is an affine transformation rather than a linear transformation. The present invention also recognizes the significant interrelations between various engine control parameters such as air/fuel ratio and ignition timing by determining control parameters after the desired torque has been fully compensated for losses and using a single function to account for air/fuel ratio and ignition angle excursions. In addition, the present invention accounts for the reduction in secondary pumping effects which may reduce pumping losses in some applications.
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Citations
26 Claims
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1. A method for determining engine control parameters based on a requested engine brake torque, the method comprising:
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determining a value representing engine losses based at least in part on the requested engine brake torque;
combining the value representing engine losses with the requested engine brake torque to determine a desired engine combustion torque;
modifying the desired engine combustion torque based on a desired value for at least one engine operating parameter;
determining at least one engine control parameter to control air mass delivered to at least one cylinder based on the modified desired engine combustion torque. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
modifying the desired engine combustion torque based on a single function of ignition angle and air/fuel ratio.
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11. The method of claim 10 wherein the single function comprises a lookup table referenced by a first variable representing a difference between desired ignition angle and ignition angle for maximum brake torque, and a second variable representing a ratio of desired air/fuel ratio to a stoichiometric air/fuel ratio.
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12. The method of claim 1 wherein the step of determining at least one engine control parameter comprises determining a desired air mass required to produce the modified desired engine combustion torque.
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13. The method of claim 12 wherein the step of determining at least one engine control parameter further comprises converting the desired air mass to a desired airflow.
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14. The method of claim 13 wherein the step of determining at least one engine control parameter further comprises determining a desired fuel mass based on the desired airflow.
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15. The method of claim 13 wherein the step of determining at least one engine control parameter further comprises determining a desired fuel mass based on the desired airflow and a desired air/fuel ratio.
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16. The method of claim 13 wherein the step of determining at least one engine control parameter further comprises determining a desired fuel mass based on an actual airflow and a desired air/fuel ratio.
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17. A method for determining control parameters for an engine, the method comprising:
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determining a first engine torque;
modifying the first engine torque based on estimated losses associated with a previously determined desired engine load to determine a second engine torque, the previously determined desired engine load being determined based in part on the first engine torque;
modifying the second engine torque based on a desired ignition angle and air/fuel ratio to determine a third engine torque;
determining a desired engine load based on the third engine torque; and
converting the desired engine load to at least one engine control parameter. - View Dependent Claims (18, 19, 20, 21, 22)
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23. A computer readable storage medium having stored data representing instructions executable by a computer to control an engine, the computer readable storage medium comprising:
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instructions for determining a value representing engine losses based at least in part on the requested engine brake torque;
instructions for combining the value representing engine losses with the requested engine brake torque to determine a desired engine combustion torque;
instructions for modifying the desired engine combustion torque based on a desired value for at least one engine operating parameter; and
instructions for determining at least one engine control parameter to control air mass delivered to at least one cylinder based on the modified desired engine combustion torque. - View Dependent Claims (24, 25, 26)
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Specification