Skip fire transition control
First Claim
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1. A method of controlling the transition of an engine between different firing fractions, the method comprising:
- while the engine is operating at a first firing fraction using a first value for an operating parameter that affects working chamber air charge, determining a target value for the operating parameter that is different than the first value, and a target firing fraction selected to deliver a requested engine output;
transitioning from the first firing fraction to the target firing fraction;
during the transition, determining a feed forward adjusted firing fraction that at least partially compensates for engine dynamics that occur during the change from the initial value for the operating parameter to the target value for the operating parameter, wherein the feed forward adjusted firing fraction changes over the course of the transition;
during the transition, determining a firing fraction correction factor indicative of a difference between an actual engine output and the requested engine output, wherein the firing fraction correction factor potentially varies over the course of the transition;
determining a commanded firing fraction during the transition that combines the firing fraction correction factor with the feed forward adjusted firing fraction; and
directing skip fire operation of the engine utilizing the commanded firing fraction during the transition, whereby the commanded firing fraction changes over the course of the transition.
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Abstract
A variety of methods and arrangements are described for controlling transitions between firing fractions during skip fire operation of an engine in order to help reduce undesirable NVH consequences and otherwise smooth the transitions. In general, both feed forward and feedback control are utilized in the determination of the firing fractions during transitions such that the resulting changes in the firing fraction better track cylinder air charge changing dynamics associated with the transition.
123 Citations
24 Claims
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1. A method of controlling the transition of an engine between different firing fractions, the method comprising:
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while the engine is operating at a first firing fraction using a first value for an operating parameter that affects working chamber air charge, determining a target value for the operating parameter that is different than the first value, and a target firing fraction selected to deliver a requested engine output; transitioning from the first firing fraction to the target firing fraction; during the transition, determining a feed forward adjusted firing fraction that at least partially compensates for engine dynamics that occur during the change from the initial value for the operating parameter to the target value for the operating parameter, wherein the feed forward adjusted firing fraction changes over the course of the transition; during the transition, determining a firing fraction correction factor indicative of a difference between an actual engine output and the requested engine output, wherein the firing fraction correction factor potentially varies over the course of the transition; determining a commanded firing fraction during the transition that combines the firing fraction correction factor with the feed forward adjusted firing fraction; and directing skip fire operation of the engine utilizing the commanded firing fraction during the transition, whereby the commanded firing fraction changes over the course of the transition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of controlling the transition of an engine between different firing fractions, the method comprising:
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while the engine is operating at a first firing fraction using a first value for an operating parameter that affects working chamber air charge, determining a target value for the operating parameter that is different than the first value, and a target firing fraction selected to deliver a requested engine output, the target firing fraction being different than the first firing fraction; transitioning from the first firing fraction to the target firing fraction, wherein during the transition, the method further includes, (i) determining a firing fraction correction factor indicative of a difference between an actual engine output and the requested engine output, wherein the firing fraction correction factor potentially varies over the course of the transition; (ii) determining a commanded firing fraction that combines the firing fraction correction factor with the target firing fraction; and (iii) directing skip fire operation of the engine during the transition utilizing the commanded firing fraction. - View Dependent Claims (16, 17)
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18. An engine controller arranged to direct skip fire operation of an engine, the engine controller comprising:
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a firing fraction determining unit arranged to determine a desired operational firing fraction suitable for delivering a desired engine output, wherein the desired operational firing fraction changes based at least in part on changes in the desired engine output; a transition adjustment unit arranged to adjust the desired operational firing fraction during transitions from a first operational firing fraction to a target operational firing fraction; and a firing timing determining unit arranged to determine a skip fire firing sequence that delivers a commanded firing fraction; and wherein the transition adjustment unit includes, a feed forward firing fraction determining unit that determines a feed forward adjusted firing fraction that at least partially compensates for engine dynamics that occur during the change from the first operational firing fraction to the target operational firing fraction, wherein the feed forward adjusted firing fraction changes over the course of the transition, and an error determining unit that determines a firing fraction correction factor based at least in part upon a difference between an estimated or actual engine output and the requested engine output, wherein the firing fraction correction factor potentially varies over the course of the transition, and wherein the transition adjustment unit is configured to determine the commanded firing fraction during transitions based at least in part on the feed forward adjusted firing fraction and the firing fraction correction factor. - View Dependent Claims (19, 20, 21)
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22. An engine controller arranged to direct skip fire operation of an engine, the engine controller comprising:
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a firing fraction determining unit arranged to determine a desired operational firing fraction suitable for delivering a desired engine output, wherein the desired operational firing fraction changes based at least in part on changes in the desired engine output; a transition adjustment unit arranged to adjust the desired operational firing fraction during transitions from a first operational firing fraction to a target operational firing fraction; a mode switching unit arranged to cause the desired operational firing fraction to be used as a commanded firing fraction during steady state skip fire engine operation and an output of the transition adjustment unit to be used as the commanded firing fractions during firing fraction transitions; and a firing timing determining unit arranged to determine a skip fire firing sequence that delivers a commanded firing fraction. - View Dependent Claims (23, 24)
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Specification