Internal combustion engine control for improved fuel efficiency
A variety of methods and arrangements for improving the fuel efficiency of internal combustion engines are described. In some aspects, methods and arrangements are described for operating an engine in a throttled skip fire mode. In other aspects, methods and arrangements are described for controlling the operational state of a variable displacement engine.
1. An engine state controller for controlling an operational state of a variable displacement engine having a plurality of working chambers, wherein the variable displacement engine is capable of operating in a plurality of different operational states each corresponding to the use of a different number of the working chambers, the engine state controller including an engine state generator arranged to receive a signal indicative of the desired engine output and to output an engine state signal that indicates a desired operational state of the engine that corresponds to a designated number of operational working chambers to be used by the engine, wherein the engine state controller uses feedback indicative of working chamber firings in the determination of the engine state signal and wherein the engine is controlled to operate using the number of working chambers indicated by the engine state signal.
2. An engine state controller as recited in claim 1 further comprising:
a firing fraction calculator arranged to receiving a signal indicative of a desired output and to output a signal indicative of a desired firing fraction;
an engine settings controller arranged to set a throttle position based at least in part on the desired output; and
wherein the desired firing fraction signal is utilized as the input signal for the engine state generator.
3. An engine state controller as recited in claim 1 further comprising a working chamber output calculator arranged to determine a relative proportion of output delivered by each working chamber firing relative to a reference output under current operating conditions of the engine.
4. An engine controller as recited in claim 3 wherein the reference output is indicative of one selected from the group consisting of:
a value that varies as a function of at least one current operating condition of the engine; and
a fixed output.
5. An engine controller as recited in claim 3 wherein the reference output is indicative of an output that would be provided by an optimized working chamber firing in the current operating conditions.
6. An engine state controller as recited in claim 1 wherein the feedback of the firings is derived from one of a requested firing, an instructed firing, a calculated firing, a detected firing event or a directed firing.
7. An engine state controller for controlling an operational state of a variable displacement engine having a plurality of working chambers, wherein the variable displacement engine is capable of operating in a plurality of different operational states each corresponding to the use of a different number of the working chambers, the engine state controller comprising:
a working chamber output calculator arranged to determine a relative proportion of output delivered by each working chamber firing relative to a reference output under current operating conditions of the engine;
a firing fraction calculator arranged to receive a signal indicative of a desired output and to output a signal indicative of a desired firing fraction, wherein the desired firing fraction signal is based at least in part on results of the working chamber output calculator; and
an engine state generator arranged to receive the signal indicative of the desired firing fraction and output an engine state signal that indicates a desired operational state of the engine that corresponds to a designated number of operational working chambers to be used by the engine, wherein the engine is controlled to operate using the number of working chambers indicated by the engine state signal.
8. An engine state controller as recited in claim 7 wherein the reference output is indicative of one selected from the group consisting of:
an amount of output that would be provided by an optimized working chamber firing in the current operating conditions; and
a set output.
9. An engine state controller as recited in claim 7 wherein the engine state generator uses predictive adaptive control in the determination of the engine state signal.
10. An engine state controller as recited in claim 7 wherein the firing fraction calculator updates the desired firing fraction at least once for every firing opportunity of the engine.
11. An engine state controller as recited in claim 7 further comprising an engine settings controller arranged to set a throttle position based at least in part on the desired output.
12. An engine state controller as recited in claim 7 wherein the engine state generator includes a sigma delta converter.
13. An engine state controller as recited in claim 7 wherein the desired operational state is determined at least in part using a controller selected from the group consisting of:
a pulse width modulation (PWM) controller;
a least means square (LMS) controller; and
a recursive least square (RLS) controller.
14. A method of controlling an operational state of a variable displacement engine having a plurality of working chambers, wherein the variable displacement engine is capable of operating in a plurality of different operational states each corresponding to the use of a different number of the working chambers, the method comprising:
receiving a signal indicative of a desired output;
determining a desired operational state suitable for delivering the desired output based at least in part on feedback control that includes feedback of working chamber firings; and
running the engine in the desired operational state to deliver the desired output.
15. A method as recited in claim 14 wherein the determining step is repeated substantially continuously such that the engine output substantially tracts the desired output.
16. A method as recited in claim 14 wherein the desired operational state is determined at least in part using predictive adaptive control.
17. A method as recited in claim 16 wherein the desired operational state is determined at least in part using a sigma delta controller.
18. A method as recited in claim 14 wherein the desired operational state is determined at least in part using a controller selected from the group consisting of:
a pulse width modulation (PWM) controller;
a least means square (LMS) controller; and
a recursive least square (RLS) controller.
19. A method as recited in claim 14 further comprising setting a throttle position based at least in part on the desired output.
20. A method as recited in claim 14 further comprising determining an actual working chamber output fraction indicative of a relative proportion of output delivered by each working chamber firing relative to a reference output.
21. A method as recited in claim 20 wherein the desired output signal is scaled based on the actual working chamber output fraction and the determination of the desired state is based at least in part on the scaled desired output signal.
22. A method as recited in claim 20 wherein the reference output is indicative of one selected from the group consisting of:
an amount of output that would be provided by an optimized working chamber firing in the current operating conditions; and
a set output.
23. A method as recited in claim 14 wherein the feedback of the firings is derived from one of a requested firing, an instructed firing, a calculated firing, a detected firing event or a directed firing.