Methods and systems are provided for improving surge control. When surge conditions are approached, a reference governor reduces engine airflow at a slower rate and to a higher level than the engine airflow required to meet the reduced torque demand. The excess torque resulting from the extra airflo
Methods and systems are provided for improving surge control. When surge conditions are approached, a reference governor reduces engine airflow at a slower rate and to a higher level than the engine airflow required to meet the reduced torque demand. The excess torque resulting from the extra airflow is offset by applying a negative torque on the driveshaft via an electric machine coupled to the engine or via alternate engine actuator adjustments.
대표청구항▼
1. A method for a boosted engine, comprising: via an electronic controller of the engine, responsive to an indication of turbocharger surge, applying negative torque from an electric machine coupled to the engine while providing an airflow to the engine greater than a demanded airflow, the demanded
1. A method for a boosted engine, comprising: via an electronic controller of the engine, responsive to an indication of turbocharger surge, applying negative torque from an electric machine coupled to the engine while providing an airflow to the engine greater than a demanded airflow, the demanded airflow determined based on an operator torque demand,wherein applying negative torque from the electric machine includes increasing a load applied on the engine from one or more of an alternator, an electric motor, and a starter-generator, and wherein providing the airflow greater than the demanded airflow includes providing a greater than demanded throttle flow to the engine. 2. The method of claim 1, wherein responsive to the indication of turbocharger surge includes responsive to a likelihood of turbocharger surge and before an occurrence of surge of a compressor of a turbocharger, and wherein the applying negative torque while providing the airflow to the engine greater than the demanded airflow is responsive to the indication of turbocharger surge during a decrease in operator torque demand. 3. The method of claim 1, wherein providing the airflow to the engine greater than the demanded airflow to meet the torque demand includes providing an airflow that is greater than an airflow amount required to meet the torque demand, while combusting the engine at stoichiometry, where the torque demand is received at the electronic controller from an operator based on a pedal position. 4. The method of claim 3, wherein the airflow greater than the demanded airflow is based on a surge limit of a turbocharger. 5. The method of claim 4, wherein applying negative torque includes applying negative torque based on the airflow greater than the demanded airflow, the negative torque applied increased as a difference between the provided airflow and the demanded airflow increases. 6. The method of claim 2, further comprising, responsive to the indication of turbocharger surge, increasing an opening of one or more of a wastegate coupled to an exhaust turbine and a compressor recirculation valve coupled to an intake compressor of the turbocharger and wherein the decrease in torque demand is determined based on an operator pedal tip-out. 7. A method for an engine, comprising: via an electronic controller of the engine: operating the engine at stoichiometry with an initial airflow amount based on a driver demanded torque;responsive to compressor surge, increasing airflow above the initial airflow amount while maintaining operation at stoichiometry; andabsorbing excess engine torque resulting from the increasing airflow via an electric motor coupled to the engine. 8. The method of claim 7, wherein an extent of increasing airflow above the initial airflow amount is based on a surge limit of a compressor, where the surge limit includes a surge line for a given compressor pressure ratio and compressor flow rate, the airflow increased further above the initial airflow amount as the compressor pressure ratio approaches or exceeds the surge limit and wherein the increasing airflow above the initial airflow amount is further responsive to an operator pedal tip-out. 9. The method of claim 8, wherein absorbing excess torque via the electric motor includes applying negative torque from the electric motor coupled to the engine, the electric motor including one or more of an alternator, a hybrid-electric motor, and a starter-generator. 10. The method of claim 9, wherein the negative torque applied is proportional to the extent of increasing airflow above the initial airflow amount, a larger negative torque applied as the extent of increasing airflow above the initial airflow amount becomes higher. 11. The method of claim 7, further comprising, responsive to the compressor surge, opening one or more of a wastegate coupled to an exhaust turbine and a compressor recirculation valve coupled to a compressor and wherein the driver demanded torque is determined based on a pedal position. 12. A method for a boosted engine, comprising: via an electronic controller of the engine: during a first tip-out, reducing engine airflow at a first, faster rate to meet torque demand; andduring a second, different tip-out, reducing engine airflow at a second, slower rate while applying an electric machine load on the engine to meet the torque demand. 13. The method of claim 12, wherein the first tip-out includes no indication of compressor surge and wherein the second tip-out includes an indication of compressor surge and wherein the first tip-out and the second tip-out include a drop in torque demand determined based on a release of an accelerator pedal of a vehicle in which the engine is installed. 14. The method of claim 13, wherein during each of the first and second tip-outs, fuel injection is adjusted based on the reduced engine airflow to maintain stoichiometric combustion and wherein reducing engine airflow at the second, slower rate includes decreasing the engine airflow less than during the first tip-out. 15. The method of claim 13, wherein during the second tip-out, the reducing is based on a surge limit, the second rate reduced further as a compressor ratio exceeds the surge limit, and wherein the electric machine load applied is based on a difference between the torque demand and a torque resulting from the reduced, surge limited engine airflow, the electric machine load applied increased as the difference increases, the electric machine load applied from one or more of an alternator, a starter-generator, and a hybrid-electric motor. 16. The method of claim 12, wherein during the first tip-out, engine airflow is reduced to a first level that is based on the torque demand, and wherein during the second tip-out, engine airflow is reduced to a second level, higher than the first level and wherein reducing the engine airflow at the second, slower rate includes limiting throttle flow reduction in response to the second tip-out. 17. A hybrid vehicle system, comprising: an engine for providing propulsion power;an electric motor for also providing propulsion power;a pedal for receiving an operator torque demand;a starter-generator for starting the engine;a compressor for providing a boosted aircharge to the engine; anda controller with computer readable instructions for: in response to an operator pedal tip-out, reducing engine airflow, the reducing limited based on a surge limit of the compressor; andincreasing an electric machine load applied on the engine based on the limited reducing to meet the operator torque demand. 18. The system of claim 17, wherein the reducing limited based on the surge limit includes reducing engine airflow to a lower airflow amount when a compressor ratio is further away from the surge limit, the lower airflow amount based on the operator torque demand, and reducing engine airflow to a higher airflow amount as the compressor ratio approaches the surge limit, further comprising a throttle disposed upstream of the compressor, and wherein the reducing limited based on the surge limit includes limiting closing of the throttle based on the surge limit. 19. The system of claim 18, wherein increasing the electric machine load applied on the engine based on the limited reducing includes, estimating an excess torque resulting from the reduced engine airflow, and increasing the electric machine load to absorb the excess torque, wherein the electric machine load includes a load from one or more of an alternator, the starter-generator, and the electric motor, the start-generator including a crank-integrated starter-generator and a belt-driven integrated starter-generator. 20. A method for a boosted engine, comprising: via an electronic controller of the engine: responsive to an indication of turbocharger surge, providing an airflow to the engine greater than a demanded airflow, the demanded airflow determined based on operator torque demand; andduring a first condition, applying negative torque from an electric machine while providing the airflow; andduring a second condition, adjusting an engine torque actuator while providing the airflow. 21. The method of claim 20, wherein the airflow greater than the demanded airflow is a first airflow amount that is greater than a second airflow amount required to provide a demanded torque based on an accelerator pedal position and wherein during the first condition, the negative torque applied is based on the airflow greater than the demanded airflow and wherein during the second condition, the engine torque actuator adjustment is based on the airflow greater than the demanded airflow. 22. The method of claim 20, wherein adjusting the engine torque actuator includes adjusting one or more of spark ignition timing and intake valve opening and closing timing, the spark timing retarded as the airflow greater than the demanded airflow increases, the intake valve timing retarded as the airflow greater than the demanded airflow increases and wherein the providing the airflow greater than the demanded airflow is responsive to the indication of turbocharger surge and a throttle of the engine closing. 23. The method of claim 20, further comprising, during a third condition, applying the negative torque from the electric machine and adjusting one or more of spark timing and valve timing while providing the airflow greater than the demanded airflow. 24. The method of claim 23, wherein the first condition includes a battery state of charge being low enough to support the negative torque from the electric machine, wherein the second condition includes one or more of the battery state of charge being at an upper limit preventing the electric machine from supporting the desired negative torque, cam position being within a limit, and spark timing being within a combustion stability limit, and wherein the third condition includes the battery state of charge being low enough to support the negative torque from the electric machine, and one or more of the cam position being within the limit and spark timing being within the combustion stability limit.
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