METHOD AND SYSTEM FOR A CHARGED ENGINE

Abstract

Procedure, comprehensive: Operating a first compression device of an engine intake based on the torque requirement of the driver; and during the operation of the first compaction device: Operating an electric motor in an electric motor mode to provide positive electric motor torque to a second compression device while an airflow deficiency at the first compression device is higher than a threshold, and Operating the electric motor in generator mode to provide negative electric motor torque to the second compression device while the airflow deficiency at the first compression device is less than the threshold; and Disconnecting the second compression device, bypassing the second compression device by opening a bypass valve of the second compression device, and providing compressed air only via the first compression device if there is essentially no lack of airflow at the first compression device.

Description

Area

[0001] The present description generally concerns methods and systems for a turbocharged engine system with staged turbocharging devices. General state of the art / Summary

[0002] Engines can be configured with supercharging devices, such as turbochargers or superchargers, to increase the airflow into a combustion chamber. Turbochargers and superchargers compress the intake air entering the engine using an intake compressor. While a turbocharger includes a compressor driven mechanically by an exhaust turbine, an electric compressor includes a compressor driven electrically by an electric motor. In some engine systems, one or more intake supercharging devices can be arranged in series or parallel, which can be referred to as a supercharging compound configuration. For example, a fast, auxiliary supercharging device (such as the electric supercharger) can be used to temporarily boost the power output of a slower, primary supercharging device (such as the turbocharger).In such a configuration, the turbocharger can be enlarged to increase the peak power and torque output of the engine, enabling more aggressive downsized engines.

[0003] Several approaches can be used to provide boost control in a turbocharging system. An exemplary approach to turbocharging system control using pressure ratios is shown by Petrovic et al. in EP 1 927 739 A1. The pressure ratio can represent the boosting capability of a turbocharging device in the turbocharging system. In Petrovic's approach, a method for coordinating two turbochargers based on desired partial pressure ratios is disclosed. Specifically, the desired partial pressure ratios for each turbocharger are determined based on calibrated lookup tables using engine speed and engine torque as inputs. The desired partial pressure ratios are then adjusted by at least one of the following: adjusting a turbocharger wastegate opening, adjusting a turbine blade geometry (e.g.,(if a turbine with variable geometry is included) and adjustment of turbine and / or compressor bypass openings is achieved.

[0004] Further state of the art is known from WO 2007 / 020 524 A1 and US 2006 / 0 260 305 A1.

[0005] However, the inventors have identified potential problems with such systems in the present work. One example is a statistical approach that uses predefined calibrations to determine the desired partial pressure ratios, which may be independent of each other (e.g., the desired partial pressure ratio of one compression device does not affect the desired partial pressure ratio of the other compression device). If Petrovic's approach is applied to a supercharging system that includes an electric compressor staged along a turbocharger, the approach may cause the compressor to run for a longer time than necessary, resulting in a decrease in fuel efficiency. As another example, the pressure ratios commanded to each compression device may be conservatively calibrated to minimize excess boost pressure.However, this can lead to a slower boost response. Furthermore, if any of the compression devices are configured with electrical assistance (such as electric assistance from an electric motor / generator coupled to a supercharger, turbocharger compressor, or turbocharger shaft), the opening of an exhaust wastegate in response to excess boost pressure can represent a missed opportunity for energy recovery from the electric motor / generator.

[0006] In one example, the problems described above can be addressed by a procedure comprising: adjusting the operation of a first intake compression device based on a target boost pressure; commanding positive torque from an electric motor to an intake compression device when the difference between a throttle intake pressure and the target boost pressure exceeds a threshold; and commanding negative torque from the electric motor to a second intake compression device when the difference is less than the threshold. In this way, a target boost pressure can be reached more quickly while increasing the potential for energy recovery from the electric motor.

[0007] As an example, a supercharging system might include an upstream, faster-acting auxiliary compressor configured with electrical assistance (e.g., an electric compressor) and a downstream, slower-acting primary compressor (e.g., a turbocharger compressor). In response to a torque demand from the driver, an engine control unit can dynamically assign pressure ratios to each compressor to provide a target boost pressure. In particular, an overall pressure ratio demand for the turbocharger can be aggressively generated. The command for the overall pressure ratio might involve corresponding adjustments to the opening of an exhaust wastegate valve coupled to a wastegate on the turbocharger turbine.For example, if torque demand increases, the wastegate opening can be reduced more aggressively to allow more exhaust flow through the turbine, causing the turbine to spool up to drive the turbocharger compressor. However, due to the inherently slower response time of the turbocharger, a temporary shortage of boost availability may occur, as indicated by a difference above the threshold between the target boost pressure and a throttle inlet pressure (or the turbocharger compressor outlet pressure). This shortage can be addressed by spooling up the electric turbocharger using positive torque from an electric motor.If the deficit increases, such as when the difference between the target boost pressure and the throttle inlet pressure falls below the threshold before the throttle inlet pressure reaches the target boost pressure, the electric assistance can be deactivated, and the electric motor can be used as a generator to absorb torque from the compressor. By adjusting the timing for when the electric assistance is deactivated, the throttle inlet pressure can be brought to the target boost pressure without generating excess pressure, while simultaneously recovering energy from the electric motor. It is understood that, while the example is described with reference to an electric compressor, this is not intended to be limiting, and the same approach can be used for an alternative compression device configured with electrical assistance, such as an electric turbocharger.

[0008] In this way, a target boost pressure can be achieved more efficiently by more aggressively calibrating a pressure ratio commanded to each of a higher-frequency, electrically assisted auxiliary compressor and a lower-frequency primary compressor. Commanding a positive speed output to an electric motor providing electrical assistance when the actual boost pressure is farther from the target boost pressure can improve a temporary boost response. The technical benefit of commanding a negative speed output to the electric motor when the actual boost pressure is closer to, but not yet at, the target boost pressure is to reduce boost excess while maximizing the energy recovery capability of the electric motor. Overall, boost pressure can be delivered more quickly and efficiently.

[0009] It is understood that the foregoing summary is provided to present, in simplified form, a selection of concepts that are described in more detail in the full description. It is not intended to identify important or essential features of the claimed subject matter, the scope of which is defined solely by the claims following the full description. Furthermore, the claimed subject matter is not limited to implementations that overcome the disadvantages mentioned above or in any part of this disclosure. Brief description of the drawings Fig. Figure 1 shows an embodiment of a supercharged engine system with several staged intake compression devices. Fig. Figure 2 presents a high-level flowchart for dynamically mapping pressure ratios between each of several inlet compression devices in a supercharged engine compound system and matching electric motor torque output to the inlet compression device configured with electrical assistance, using a lead compensator. Fig. Figure 3 represents an exemplary dynamic pressure ratio assignment between an electric compressor and a turbocharger control during a vehicle acceleration event. Fig. Figure 4 represents an exemplary system response using a leading compensator. Fig. Figure 5 presents an exemplary block diagram of a charging control architecture that includes dynamic pressure ratio mapping and lead compensation capabilities. Fig. Figure 6 presents an exemplary method for charge control by coordinating the operation of a turbocharger and an electric compressor using dynamic pressure ratio allocation and lead compensation. Fig. Figure 7 shows an illustration with exemplary acceleration curves according to the present disclosure. Fig. Figure 8 presents a prophetic example of the pressure ratio coordination of a turbocharger and electric compressor during vehicle operation. Detailed description

[0010] The following description concerns systems and methods for charge control in an engine system with staged charging devices, wherein at least one of the charging devices is configured with electrical assistance. A non-restrictive example of such a charged engine system is given in Fig. Figure 1 shows a turbocharger staged downstream of the electric compressor. The boost control of the supercharger system can be achieved by dynamically assigning different pressure ratio commands to each compression device and by further using lead compensation to reduce pressure excesses. An engine control unit can be configured to execute a control routine via the control architecture. Fig. 5 to perform, such as the exemplary routine from Fig. 2. To assign a pressure ratio to the slower-acting compression device based on torque demand, while a pressure ratio to the faster-acting compression device (with electric assistance) is assigned based on a lack of airflow. Additionally, the control system can use a lead compensator to determine when to increase and decrease the electrical assistance from an electric motor to reduce pressure excesses. An exemplary approach, implemented in the motor system, consists of Fig. 1 can be applied, as shown in the exemplary routine from Fig. Figure 6 shows that, as a result of the dynamic pressure ratio assignment, a target boost pressure can be achieved in a shorter time and with reduced dependence on electrical assistance, as shown in Figure 6. Fig. Figure 3 shows that, as a result of the advantage compensation, the boost pressure overrun can be reduced, while energy recovery possibilities in an electric motor are maximized, as shown in Figure 3. Fig. 4 shown. By relying on these approaches, an acceleration curve, as in Fig. 7 shown, can be improved. A prophetic example of coordinating turbocharger and electric compressor operation based on pressure ratios during vehicle operation is in Fig. 8 shown.

[0011] Fig. Figure 1 schematically shows aspects of an exemplary engine system 100, which includes an engine 10 coupled to a vehicle 102. In some examples, the vehicle 102 may be a hybrid vehicle with multiple torque sources available to one or more vehicle wheels 47. In other examples, the vehicle 102 is a conventional vehicle with only one engine. In the example shown, the vehicle 102 includes an engine 10 and an electric machine 52. The electric machine 52 may be an electric motor or a motor / generator. The engine 10 and the electric machine 52 are connected to the vehicle wheels 47 via a transmission 48 when one or more clutches 53 are engaged.In the illustrated example, a (first) clutch 53 is provided between the motor 10 and the electric machine 52, and a (second) clutch 53 is provided between the electric machine 52 and the transmission 48. A controller 12 can send a signal from each clutch 53 to an actuator to engage or disengage the clutch, thereby connecting or disconnecting the motor 10 from the electric machine 52 and its associated components, and / or connecting or disconnecting the electric machine 52 from the transmission 48 and its associated components. For example, when the clutches 53 are engaged, torque can be transmitted from the motor 10 via a crankshaft 40, a transmission 48, and a drive shaft 84 to the vehicle wheels 47. The transmission 48 can be a manual transmission, a planetary gear system, or another type of transmission.The transmission 48 can be a fixed-ratio transmission incorporating a variety of gear ratios to allow the engine 10 to rotate at a different speed than the wheels 47. By changing the torque transmission capacity of the first clutch 53 (e.g., the degree of clutch slip), the amount of engine torque transmitted to the wheels via the drive shaft 84 can be modulated.

[0012] The powertrain can be configured in various ways, including as a parallel, series, or series-parallel hybrid vehicle. In embodiments as an electric vehicle, a system battery 45 can be a traction battery that supplies electrical power to the electric machine 52 to provide torque to the vehicle wheels 47. In some embodiments, the electric machine 52 can also be operated as a generator to provide electrical power for charging the system battery 45, for example, during braking. It is understood that in other embodiments, including embodiments not as an electric vehicle, the system battery 45 can be a typical starting, lighting, and ignition (SLI) battery coupled to an alternator 46.

[0013] The alternator 46 can be configured to charge the system battery 45 using engine torque drawn from the crankshaft while the engine is running. Additionally, the alternator 46 can supply power to one or more of the engine's electrical systems, such as one or more auxiliary systems, which may include a heating, ventilation, and air conditioning (HVAC) system, vehicle lights, an onboard entertainment system, and other auxiliary systems as described below, based on their electrical requirements. For example, the current drawn from the alternator can continuously vary based on each of the driver's cabin cooling requirements, battery charging requirements, requirements of other auxiliary vehicle systems, and electric motor torque.A voltage regulator can be coupled to the alternator 46 to regulate the alternator's power output based on system usage requirements, including auxiliary system needs.

[0014] In the illustrated embodiment, the motor 10 is a turbocharged compound motor configured with multiple staged supercharging devices. Specifically, the motor 10 includes a first supercharging device staged upstream of a second supercharging device. Here, the first supercharging device is an auxiliary supercharging device and the second supercharging device is a primary supercharging device, although other configurations are possible. The illustrated configuration results in a first compressor 110 (of the first supercharging device) being positioned in an engine intake duct 42 upstream of a second compressor 114 (of the second supercharging device). At least one of the supercharging devices can be configured with electrical assistance from an electric motor.In the present example, the first charging device is an electric compressor 13 configured to operate with electrical assistance from an electric motor, while the second charging device is a turbocharger 15. However, other combinations and configurations of charging devices are possible without deviating from the scope of this disclosure. For example, in alternative embodiments, the turbocharger 15 may be an electric turbocharger comprising an electric motor coupled to the compressor, turbine, or turbocharger shaft, while the compressor may be configured as an electric or mechanical compressor. In still other examples, both the first and second charging devices may be electric compressors or electric turbochargers.

[0015] In the illustrated example, the electric compressor 13 includes a first compressor 110 driven by an electric motor 108. Specifically, a fan of the first compressor 110 can be driven by power received from the electric motor 108 along a compressor shaft 80. In some examples, the first compressor 110 of the compressor 13 can additionally be driven by the motor crankshaft via a clutch and a gear mechanism. The electric motor 108 can be powered by an onboard energy storage device, such as a system battery 45. The electric motor 108 can also be powered by an alternator 46, either additionally or alternatively. The amount of electrical power supplied to the electric motor 108 can be varied to adjust the compressor's duty cycle.In one example, the amount of electrical power supplied to the electric motor 108 can be increased to increase the speed of the first compressor 110, thereby increasing the electrical load applied to the alternator and reducing the alternator current. As a result of the electrical assistance, the compressor 13 can spool up quickly, which provides for fast-acting or high-frequency boosting.

[0016] Under selected conditions, air can enter the first compressor 110 when the opening of an electric supercharger bypass valve (ESBV) 72 is reduced, thereby directing incoming air from an air box 112 through a bypass duct 70 of the first compressor and into the first compressor 110, where it is pressurized for delivery to the second compressor 114. Fresh air received at an inlet of the second compressor 114 is then compressed and fed into the motor 10. When the opening of the ESBV 72 is enlarged, an increase in the amount of air entering the second compressor 114 without having passed through the bypass duct 70 of the first compressor and the first compressor 110. During conditions in which the ESBV 72 is fully open, compressed air can only be supplied to the motor 10 via the second compressor 114 of the turbocharger 15.By spinning up the electric compressor via the electric motor, a boost pressure surge can be quickly provided to the engine.

[0017] The electric motor 108 can be configured as a motor-generator. Thus, during conditions where electrical assistance is required for boost build-up, the electric motor can provide positive torque to drive either the compressor's centrifugal compressor (or the turbocharger shaft) to enhance temporary boost pressure delivery. However, the electric motor is also capable of energy recovery by "braking" the motor shaft. In this mode, negative torque can be applied to the compressor (or shaft), reducing the compressor speed and simultaneously charging the system battery (such as battery 45) coupled to the electric motor. As referenced in Fig. 2. When executed, an engine control unit can control the time and amount of positive and negative torque applied by the electric motor to the compressor to regulate throttle inlet pressure (TIP) / boost pressure.

[0018] The turbocharger 15 includes the second compressor 114, which is driven by a turbine 116. The second compressor 114 is shown as a turbocharger compressor, which is mechanically coupled to the turbine 116 via a shaft 19, with the turbine 116 being driven by expanding engine exhaust gases. In one embodiment, the turbocharger can be a twin-scroll device. In another embodiment, the turbocharger can be a variable geometry turbocharger (VGT), wherein the turbine geometry is actively varied depending on engine operating conditions.

[0019] Fresh air is fed into the engine 10 along the intake duct 42 via an air box 112 and flows to the second compressor 114. Under selected conditions, as described below, air compressed by the turbocharger 15 can be recirculated from an outlet to an inlet of the second compressor 114 through a second compressor bypass duct 60 by adjusting the opening of a compressor recirculation valve (CRV) 62. The CRV 62 can be a continuously variable valve, and increasing the opening of the CRV 62 can involve actuating (or feeding) a solenoid of the valve.

[0020] One or both of the CRV 62 and ESBV 72 can be continuously adjustable valves, with the valve position continuously variable from a fully closed to a fully open position. Alternatively, the CRV 62 can be a continuously adjustable valve, while the ESBV 72 is an on / off valve. In some embodiments, the CRV 62 can be partially open during operation of the supercharged engine to provide clearance to the surge line. In this case, the partially open position can be a standard valve position. The opening of the CRV 62 can then be increased in response to a specified surge input. For example, the CRV 62 can be adjusted from a standard partially open position to a fully open position, with the degree of opening based on a specified surge input (e.g., compressor ratio, compressor flow rate, pressure differential at the compressor, etc.).In alternative examples, the CRV 62 can be kept closed during operation of the turbocharged engine (e.g. peak power conditions) to reduce the charging response time and increase peak power.

[0021] The second compressor 114 is coupled to a throttle valve 20 via a charge-air cooler (CAC) 18 (also referred to here as an intercooler). Air flows from the second compressor 114 through the CAC 18 and the throttle valve 20 to an intake manifold 22. The CAC 18 can be, for example, an air-to-air or water-to-air heat exchanger. The intake manifold pressure (e.g., the pressure of the air charge in the intake manifold) can be determined using a manifold absolute pressure (MAP) sensor 124.

[0022] The intake manifold 22 is connected to a series of combustion chambers 30 via a series of intake valves (not shown). The combustion chambers are further coupled to an exhaust manifold 36 via a series of exhaust valves (not shown). In the illustrated embodiment, a single exhaust manifold 36 is shown. In other embodiments, however, the exhaust manifold may include a plurality of exhaust manifold sections. Configurations featuring a plurality of exhaust manifold sections can allow wastewater from different combustion chambers to be routed to different locations in the engine system.

[0023] In one embodiment, each of the exhaust and intake valves can be electronically actuated or controlled. In another embodiment, each of the exhaust and intake valves can be actuated or controlled by cams. Regardless of whether actuation is electronic or cam-operated, the timing of the opening and closing of the exhaust and intake valves can be adjusted for the desired combustion and emission control performance. For example, the cam control can be adjusted via a variable cam control system so that the intake and exhaust cams are moved to a position that provides the optimal volumetric efficiency for the prevailing operating conditions.

[0024] One or more fuels, such as gasoline, alcohol-fuel mixtures, diesel, biodiesel, compressed natural gas, etc., can be supplied to the combustion chambers 30. The fuel can be supplied to the combustion chambers via direct injection, port injection, throttle body injection, or any combination thereof. In the example shown, fuel is supplied to each combustion chamber 30 via direct injection by a fuel injection device 66 (while in Fig. (1) only one fuel injection device is shown; each combustion chamber includes a fuel injection device coupled to it. Fuel can be supplied to the fuel injection device 66 by a fuel system (not shown) comprising a fuel tank, a fuel pump, and a fuel distributor. Combustion in the combustion chambers can be initiated by spark ignition and / or compression ignition.

[0025] As in Fig. As shown in Figure 1, exhaust gas is routed from the exhaust manifold 36 to the turbine 116 to drive the turbine. If reduced turbine torque is desired, a portion of the exhaust gas can instead be routed through a wastegate 90, bypassing the turbine. A wastegate actuator 92 (e.g., a wastegate valve) can be actuated to open, releasing at least some exhaust pressure from upstream of the turbine 116 via the wastegate 90 to a point downstream of the turbine 116. By reducing the exhaust pressure upstream of the turbine 116, the turbine speed can be reduced.

[0026] The combined flow from turbine 116 and wastegate 90 passes through an emission control device 170. In general, the emission control device 170 can include one or more exhaust aftertreatment components configured to reduce the amount of one or more substances in the exhaust stream. For example, an exhaust aftertreatment component can be configured to reduce NOₓ. x to be included from the exhaust gas stream when the exhaust gas stream is lean, and the included NO x to reduce NOₓ when the exhaust gas flow is rich. In other examples, an exhaust aftertreatment component may be configured to reduce NOₓ. x to disproportionate or NO x to selectively reduce using a reducing agent. In yet other examples, the emission control device 170 includes a three-way catalyst configured to oxidize residual hydrocarbons and carbon monoxides, while reducing NOx in the exhaust gas stream. Different catalysts for exhaust gas aftertreatment with such functionality can be arranged separately or together in washcoats or at other locations in the emission control device 170. In some embodiments, the emission control device 170 can further include a regenerable soot filter configured to trap and oxidize soot particles in the exhaust gas stream.

[0027] The treated exhaust gas from the emission control device 170 can be discharged into the atmosphere, either wholly or partially, via an exhaust gas line 35. Depending on the operating conditions, however, a portion of the exhaust gas can instead be redirected to the intake port 42 via an exhaust gas recirculation (EGR) channel (not shown), which includes an EGR cooler and an EGR valve. The EGR can be directed to the inlet of the first compressor 110, the inlet of the second compressor 114, or both.

[0028] One or more sensors can be coupled to the inlet of the second compressor 114 (as shown) and / or the first compressor 110 (not shown). For example, a temperature sensor 55 for estimating a compressor inlet temperature can be coupled to the inlet of the second compressor 114. As another example, a pressure sensor 56 for estimating the pressure of the air entering the second compressor can be coupled to the inlet of the second compressor 114. The pressure upstream of the second compressor 114 and downstream of the first compressor 110, as measured by the pressure sensor 56, is hereby designated P1. Other sensors can include, for example, air-fuel ratio sensors, humidity sensors, etc. In further examples, one or more of the second compressor inlet conditions (such as humidity, temperature, etc.) can be derived from engine operating conditions.The sensors can estimate the condition of the intake air received from the intake duct at the second compressor inlet, as well as the air charge returned from upstream of the CAC 18. One or more sensors can also be connected to the intake duct 42 upstream of the first compressor 110 to determine the composition and condition of the air charge entering the compressor. These sensors can, for example, include a pressure sensor 58. The pressure upstream of the air box 112 (e.g., atmospheric pressure), as measured by the pressure sensor 58, is hereby designated P0. Additionally, a throttle inlet pressure (TIP) sensor 59 can be connected downstream of the CAC 18 and upstream of the throttle valve 20 to estimate the boost pressure supplied to the engine. The pressure downstream of the CAC 18 and upstream of the throttle valve 20, as measured by the TIP sensor 59, is referred to here as P2.The overall pressure ratio of the charging system is considered a single factor. P2P0 defined, a pressure ratio at the first compressor 110 is considered P1P0 defined and a pressure ratio at the second compressor 114 is as P2P1 defined.

[0029] During pedal operation by the operator, when switching from naturally aspirated to turbocharged operation in response to an increase in the operator's torque demand, turbo lag can occur. This is due to delays in the turbine 116 spinning up, as the turbocharger is a slower-acting compression device, and a temporary reduction in flow through the second compressor 114 when the throttle valve 20 opens upon pedal operation. The same can also happen when the engine is in turbocharged operation and a temporary increase in boost demand occurs due to increased pedal operation by the driver. To reduce this turbo lag, both the compressor 13 and the turbocharger 15 can be activated under these selected conditions.In particular, the faster-acting, electrically operated compression device, the electric compressor, can be used to enhance the temporary boost response. Specifically, in response to pedal actuation, the wastegate actuator 92 can be closed (e.g., fully closed) to increase the exhaust gas flow through the turbine 116. During the turbine 116's spin-up, boost pressure can be temporarily provided by the first compressor 110. Activating the compressor 13 can involve drawing energy from the system battery 45 to rotate the electric motor 108, thereby accelerating the first compressor 110. Additionally, the ESBV 72 can be closed (e.g., fully closed) to allow a larger portion of the intake air to flow through the bypass duct 70 and be compressed by the first compressor 110. Additionally, the CRV 62 can be closed (e.g.,The first compressor 110 can be fully closed to increase the current through the second compressor 114. Once the turbine has reached a sufficient speed and the turbocharger is able to provide the required amount of boost, the first compressor 110 can be slowed down by deactivating the electric motor 108 (e.g., by interrupting the power supply to the electric motor 108 from the battery 45). Additionally, the ESBV 72 can be opened to allow a larger proportion of the air to bypass the first compressor 110.As further described herein, the activation (and deactivation) of the first compressor 110 can be precisely controlled to provide the desired boost pressure, while reducing over- or under-delivery of the desired boost pressure, minimizing boost pressure disturbances when the first compressor 110 is activated / deactivated, and minimizing the operating time of the first compressor 110, thereby minimizing the amount of electrical power consumed by the compressor 13. The desired amount of charge can be provided by dynamically coordinating the turbocharger 15 and the compressor 13 based on the boosting capability of the turbocharger 15 (e.g., the pressure ratio at the second compressor 114) at a given time and at a desired overall boost pressure ratio, as described in the following. Fig. 2-6 describes this. The control unit can dynamically adjust the pressure ratio assignment to the compressor based on a lack of airflow at the turbocharger. Additionally, the control unit can adjust the timing and output of the electric motor torque supplied to the compressor by the electric motor to reduce excess pressure while maximizing energy recovery.

[0030] During an operator pedal release event, compressor surging can occur when transitioning from turbocharged to unturbed (or reduced-boost) engine operation. This is due to a reduced flow through the second compressor 114 when the throttle valve 20 closes upon pedal release. The reduced forward flow through the second compressor can cause surging and impair turbocharger performance. Additionally, surging can lead to noise, vibration, and harshness (NVH) issues, such as unwanted noise from the engine intake system.To enable a rapid reduction in torque demand during standard vehicle operation in response to pedal release, without causing compressor surging, at least a portion of the compressed air charge by the second compressor 114 can be recirculated to the compressor inlet. This allows excess boost pressure to be reduced essentially immediately. In particular, the CRV 62 can be opened to return (warm) compressed air from the outlet of the second compressor 114 upstream of the CAC 18 to the inlet of the second compressor 114. In some embodiments, the compressor recirculation system can additionally or alternatively include a recirculation channel for returning cooled compressed air from downstream of the CAC 18 to the inlet of the second compressor 114. Additionally, the wastegate actuator 92 can be opened further (e.g.,The turbine should be moved to a fully open position so that a larger portion of the exhaust flow moves to the exhaust pipe, bypassing the turbine and thus accelerating the turbine's shutdown.

[0031] The controller 12 can be contained within a control system 14. According to the diagram, the controller 12 receives information from a variety of sensors 16 (various examples of which are described here) and sends control signals to a variety of actuators 81 (various examples of which are described here). For example, the sensors 16 can include an exhaust gas sensor 126 located upstream of the turbine 116, a MAP sensor 124, an exhaust gas temperature sensor 128, an exhaust gas pressure sensor 129, a compressor inlet temperature sensor 55, a compressor inlet pressure sensor 56 (e.g., for measuring P1), a mass airflow (MAF) sensor 57, a pressure sensor 58 (e.g., for measuring P0), and a TIP sensor 59 (e.g., for measuring P2). Other sensors, such as additional pressure, temperature, air-fuel ratio and composition sensors, can be coupled to various points in the engine system 100.The actuators 81 can, for example, include the throttle valve 20, the CRV 62, the ESBV 72, the electric motor 108, the wastegate actuator 92, and the fuel injection device 66. The controller 12 can receive input data from the various sensors, process the input data, and use the various actuators to adjust the engine operation based on the received signals and instructions stored in a memory of the controller. The controller can use the actuators in response to the processed input data based on an instruction or code containing one or more routines, such as those described here with reference to the... Fig. 2 (and Fig. 6) correspond to the exemplary control routines described. As an example, in response to the measured pressures indicating a boost pressure deficit when operating the turbocharger, the control unit can actuate the electric motor that drives the compressor and actuate the ESBV to the closed position to provide additional boost via the compressor.

[0032] In this way, the components from Fig. 1. A vehicle system comprising: an engine having an inlet; an accelerator pedal for receiving a torque request from a driver; a supercharging system comprising a first (auxiliary) turbocharger compressor driven by an electric motor drawing electrical energy from a battery, and a second (primary) turbocharger compressor driven by an exhaust turbine, the second compressor being positioned downstream of the first compressor in the engine inlet; a bypass comprising a bypass valve coupled to the first compressor; a wastegate comprising a wastegate actuator coupled to the exhaust turbine; a first pressure sensor coupled to the inlet upstream of the first compressor for estimating air pressure; a second pressure sensor coupled to the inlet downstream of the first compressor and upstream of the second compressor;for estimating the turbocharger inlet pressure; a third pressure sensor coupled to the inlet downstream of the second compressor for estimating a throttle inlet pressure; and a controller with computer-readable instructions stored in non-volatile memory for the following: in response to the driver's torque demand, commanding an overall pressure ratio at the supercharging system via an adjustment of the wastegate actuator; and varying the commanded pressure ratio at the first compressor via an adjustment of an electric motor output based on an airflow deficiency at the second compressor, the airflow deficiency being estimated based on an actual pressure ratio at the second compressor. In one example, commanding the overall pressure ratio might involve reducing the opening of the wastegate actuator as the driver's torque demand increases.to increase the actual pressure ratio at the second compressor, and wherein varying the pressure ratio commanded at the first compressor includes operating the electric motor in a motor mode when the airflow deficiency increases above a threshold, and operating the electric motor in a generation mode when the airflow deficiency decreases below the threshold. In another example, the control may further include instructions to: close the ESBV when the airflow deficiency increases above a threshold to increase the pressure ratio at the first compressor; and open the ESBV when the airflow deficiency decreases below the threshold to decrease the pressure ratio at the first compressor.

[0033] The components from Fig. 1. The control system can further enable the system to command an overall pressure ratio for a first compression device of an engine intake based on the driver's torque demand; if the actual pressure ratio of the second compressor is farther from the overall pressure ratio, to provide positive electric motor torque to increase the pressure ratio of the first compressor; and if the actual pressure ratio of the second compressor is closer to the overall pressure ratio, to provide negative electric motor torque to decrease the pressure ratio of the first compressor. In the preceding example, commanding the overall pressure ratio can involve reducing the wastegate actuator opening as the driver's torque demand increases, in order to increase the actual pressure ratio at the second compressor.where providing the positive electric motor torque involves operating the electric motor in a motor mode with an electric motor output based on an airflow deficiency, the airflow deficiency being estimated based on a difference between the actual pressure ratio of the second compressor and the overall pressure ratio, and where providing the negative torque involves operating the electric motor in a generation mode with a generator output based on the difference. In another example, the control may further include instructions to close the ESBV during the provision of the positive and negative electric motor torque. The system may further include: a first pressure sensor coupled to the inlet upstream of the first compressor to estimate air pressure; a second pressure sensor,a pressure sensor coupled to the inlet downstream of the first compressor and upstream of the second compressor to estimate the turbocharger inlet pressure; and a third pressure sensor coupled to the inlet downstream of the second compressor to estimate a throttle inlet pressure; wherein the control may further include instructions for: estimating the overall pressure ratio based on an output from the third pressure sensor relative to the output from the first pressure sensor; estimating the actual pressure ratio at the second compressor based on an output from the third pressure sensor relative to the output from the second pressure sensor; and estimating the actual pressure ratio at the first compressor based on an output from the second pressure sensor relative to the output from the first pressure sensor.

[0034] With reference to Fig. Figure 2 shows an exemplary method 200 for operating a supercharged engine system with staged supercharging devices. The supercharged engine system can include at least two inlet compression devices arranged in series, at least two of which include electrical assistance. One of the at least two compression devices can be a slower-acting (low-frequency) compression device, such as a turbocharger, configured as the primary supercharging device, while the other of the two compression devices can be a faster-acting (higher-frequency) compression device, such as an electric compressor, configured as the auxiliary supercharging device. Instructions for carrying out method 200 and the other methods included herein can be issued by a controller (e.g., the controller 12 from Figure 2). Fig. 1) are executed on the basis of instructions stored in a memory of the controller and in conjunction with signals received from sensors of the motor system, such as the sensors referred to above. Fig. 1. The control system can use motor actuators of the motor system, such as a bypass valve of the electric compressor (e.g. ESBV 72 from Fig. 1), an electric motor (such as the electric motor 108 from Fig. 1) and a turbocharger wastegate actuator (e.g. wastegate actuator 92 from Fig. 1) to adapt the engine operation to the procedures described below.

[0035] In procedure 202, procedure 200 involves estimating and / or measuring engine operating conditions. For example, assessed operating conditions may include engine speed, pedal position, driver torque demand, manifold absolute pressure, manifold airflow, manifold air temperature, ambient conditions (such as ambient temperature, air pressure, and humidity), engine coolant temperature, etc. For example, the air pressure may be measured from a pressure sensor, such as pressure sensor 58. Fig. 1 can be measured.

[0036] In 204, procedure 200 involves determining whether supercharging is requested. In one example, supercharging might be requested at medium to high internal combustion engine loads. In another example, supercharging might be requested in response to pedal operation by a driver or an increase in the driver's torque demand. If no supercharging is requested, such as when the engine load is low or the driver's torque demand is low, procedure 200 proceeds to 206 and involves operating the engine with natural intake (e.g., manifold vacuum). Operating the engine with natural intake cannot involve activating the staged supercharging devices. For example, an electric motor may be used to drive the electric compressor (e.g.,electric motor 108) will not be supplied with power, and the turbocharger wastegate actuator can be commanded to be fully open to direct some of the exhaust gas through the wastegate, while one turbine of the turbocharger (e.g., the turbine 116 from . Fig. 1) is circumvented. Following 206, the procedure ends in 200.

[0037] When boost is requested at 204, such as in response to a pedal actuation event, procedure 200 transitions to 208 and involves generating a command for the total pressure ratio for the slower, primary compression device based on the driver's torque / boost requirement. In this context, the total pressure ratio is a steady-state desired pressure ratio that is gradually commanded to and achieved by the primary compression device. The total commanded pressure ratio can be described as P2*P0 be defined, whereby P2* P0 represents a desired throttle inlet pressure or a desired outlet pressure of the supercharging system. In an example, this is the outlet pressure of the slower-acting primary compression device, such as the outlet pressure of a turbocharger compressor. P0 represents an inlet pressure of the supercharging system or atmospheric pressure. In an example, this is the inlet pressure of the faster-acting auxiliary compression device, such as the inlet pressure of an electric compressor. In a configuration where the auxiliary compression device is staged upstream of the primary compression device, the actual outlet pressure of the primary compression device, P2 (e.g., as measured by a TIP sensor), can be described as follows: P2=P0×P1P0×P2P1 where P1 is an outlet pressure of the auxiliary compression device, which is also an inlet pressure of the primary compression device. P2 also corresponds to a total boost pressure achieved at the staged supercharging devices. As can be seen from the preceding equation, P1P0 a pressure ratio at the auxiliary compression device and P2P1 The pressure ratio at the primary compression device is the overall pressure ratio of the system. In other words, the total pressure ratio is the product of the pressure ratios at each compressor in series. The pressure ratio represents the capability of the charging device (e.g., electric compressor, turbocharger, or supercharging system). However, the throttle inlet pressure cannot isolate the charging contribution of each device. Thus, the transient supercharging response can be enhanced by coordinating the pressure ratios commanded to each charging device with a steady-state desired pressure ratio P2* / P0.

[0038] In one example, the controller can generate the overall boost ratio command by estimating P0 based on an output from an air pressure sensor. The controller can further estimate P2* based on an output from a driver's accelerator pedal position sensor. The controller can refer to a lookup table where target boost pressure is stored as a function of pedal position, such as increasing target boost pressure as the accelerator pedal is pressed further (increased pedal movement towards a fully depressed position). Alternatively, the controller can use a model or algorithm that takes the pedal position as an input and provides target boost pressure as an output. Then, the boost ratio command can be determined as P2* / P0.

[0039] In one example, the turbocharger can be controlled to provide the entire requested boost pressure, P2*, to deliver. For this reason, the total pressure ratio commanded to the turbocharger compressor can be determined as follows: P2P1→P2∗P0 or P2×P0P1→P2∗, if limt→∞P1P0=1 where t represents time.

[0040] In the 210 procedure, this involves adjusting a boost pressure actuator of the slower-acting primary compression device based on the generated total pressure ratio command. For example, if the primary compression device is a turbocharger, the control unit can generate a command for a wastegate coupled to the exhaust turbine based on the generated total pressure ratio command. The wastegate command can specify a degree of wastegate valve opening, which is sent to the wastegate actuator. In one example, the commanded degree of wastegate opening can be decreased as the total pressure ratio command increases. For instance, the wastegate can be fully closed on commands above the threshold pressure ratio.

[0041] In one example, the controller can input the command for the total boost ratio and MAF (as determined by an intake MAF sensor) into a lookup table (or model or algorithm) that outputs a turbocharger wastegate actuator position, where the turbocharger wastegate actuator position corresponds to a turbine speed and a corresponding turbocharger compressor speed. In another example, the controller can refer to a compressor mapping to determine a desired turbocharger compressor speed for the commanded total boost ratio and desired airflow conditions, and can further relate the resulting turbocharger compressor speed to a corresponding turbocharger wastegate actuator position. Furthermore, the actual turbocharger boost ratio, P2P1 It can be used as feedback for wastegate control. For example, if the actual turbocharger pressure ratio increases, the turbocharger wastegate actuator can be adjusted to a wider open position. Additionally or alternatively, if the turbocharger is operating in a threshold pumping range, the openings of one or both of the CRV and the wastegate actuator can be increased.

[0042] It is understood that the ordered overall pressure ratio may be adjusted (e.g., limited) in further examples to take into account mechanical limitations of the supercharged engine system, such as a temperature, pressure, or speed limitation of the primary compression device, above which (temperature, pressure, or speed) the performance of the primary compression device may be adversely affected, for example, due to hardware problems.In one example, the control system can reduce the commanded total pressure ratio by a factor based on the difference between the predicted temperature and the threshold temperature if the commanded total pressure ratio, which is based solely on the driver's torque requirement, is predicted to result in a compressor inlet or outlet temperature (of the primary compression device) that is higher than a threshold temperature at which the hardware of the primary compression device is compromised.

[0043] Due to the slower response time of the primary compression device, in this case the turbocharger, a temporary boost pressure deficit may occur. For example, the deficit may result from a steady-state boost pressure output that requires the turbine to spool up before it can drive the turbocharger compressor. In 212, the procedure involves estimating the boost pressure deficit and a corresponding airflow deficit at the primary compression device. For example, the turbocharger boost pressure ratio deficit (Π*) can be defined as follows: Π*=P2∗P0P2P1

[0044] The control unit can calculate the boost pressure deficit as a function (e.g., ratio or difference) of the actual pressure ratio at the primary compressor relative to the desired or commanded pressure ratio. The actual pressure ratio can be determined as the compressor inlet pressure of the primary compressor relative to the actual throttle inlet pressure. This boost pressure deficit reflects the airflow deficiency at the primary compressor and is used to assign the pressure ratio command to the auxiliary compressor.

[0045] For example, if the auxiliary compressor is an electric compressor, the pressure ratio commanded to the electric compressor is dynamically planned based on the turbocharger's capability (as derived from the actual turbocharger pressure ratio, P2 / P1). This allows the control system to know the exact boost pressure deficit in real time when the turbine spools up and to regulate the speed of the electric compressor (n_eSC) to reduce the deficit. Additionally, the control system can shape the closed-loop system dynamics by knowing the electric compressor pressure ratio (P1 / P0), as described above.

[0046] For example, the desired pressure ratio target of the electric compressor (P1*P0) defined as Π* with a restriction of the turbocharger pressure ratio as follows: P1*P0=P2*P0max{1,P2P1}

[0047] The limitation is included to prevent the desired pressure ratio target for the electric compressor from exceeding the total desired system pressure ratio when P1 > P2, which could occur shortly after the throttle opens.

[0048] In section 214, the procedure involves generating a pressure ratio command for the faster auxiliary compressor. In one example, the pressure ratio command is generated based on the pressure ratio deficit. In another example, the pressure ratio command is generated based on the corresponding airflow deficit. For instance, the controller can estimate an inlet pressure for the electric compressor (e.g., based on a measured atmospheric pressure) and use a lookup table, model, or algorithm to calculate a desired outlet pressure for the electric compressor that corresponds to the airflow deficit. The pressure ratio command for the electric compressor can then be determined as the ratio of the actual inlet pressure relative to the desired outlet pressure.

[0049] In 216, the procedure involves commanding electrical assistance to the auxiliary compression device. Specifically, the controller can command positive electric motor torque from the electric motor to the auxiliary compression device, such as the electric compressor, depending on the deficiency-based pressure ratio command. In one example, commanding the positive electric motor torque involves estimating a compressor speed of the electric compressor that will provide the desired compressor outlet pressure at the electric compressor, such as via a lookup table, figure, or algorithm, and then estimating an electric motor speed (or a degree of electric assistance) that will provide the estimated compressor speed. The controller can then adjust a duty cycle commanded to the electric motor to operate the electric motor at the required electric motor speed.

[0050] Next, at 218, the actual boost pressure can be compared relative to the target throttle inlet pressure to determine if the actual boost pressure is within a target throttle inlet pressure (TIP) threshold. For example, it can be determined whether the turbocharger outlet pressure is within a threshold of the desired TIP, such as when the difference between the outlet pressure and the desired TIP is less than a threshold. In an alternative example, a ratio of the turbocharger outlet pressure to the target throttle inlet pressure can be compared. If the difference (or ratio) is not within the threshold, the control unit at 220 further dynamically adjusts the pressure ratio mapping at the primary and auxiliary compression devices.In particular, when the turbine ramps up and the turbocharger's charging capacity increases, the pressure ratio at the turbocharger can begin to approach the commanded pressure ratio, the deficiency can begin to decrease, and accordingly, the pressure ratio (and electrical assistance) commanded to the electric compressor can be reduced.

[0051] In this way, the controller continuously adjusts the auxiliary device in real time based on the actual capability of the primary compaction device. The controller can use a dynamically assigned module, as is the case here. Fig. 5 further described to adjust the pressure ratios. Accordingly, as the slower-responding turbocharger ramps up, the required assistance from the faster-responding electric compressor is gradually reduced. Ultimately, if the turbocharger is able to maintain the entire desired boost pressure, no assistance from the electric compressor is required. An example of the dynamic mapping of pressure ratios and the resulting accelerated achievement of the target boost pressure with minimal reliance on electric assistance is provided with reference to Fig. 3 described.

[0052] With brief reference to Fig. 3 represents the Fig. The graph represents a pressure ratio on the y-axis and time on the x-axis. The total commanded pressure ratio, based on the torque requirement and represented by P*2 / P0, is shown by the dashed line 302. This is the pressure ratio commanded to the primary compression device. The actual pressure ratio of the primary compression device, represented by P2 / P1, is shown by the dashed line 304 and indicates the charging capability of the primary compression device. This changes over time and evolves to the steady-state value, which was gradually commanded due to the slower response time of the primary compression device. A preliminary pressure ratio deficit, represented by Π* (uncut), is shown by the dashed line 306.The truncated version of this pressure ratio deficiency is used to plan the pressure ratio commanded to the auxiliary compaction device, which has the faster response time. The pressure ratio commanded to the auxiliary compaction device, represented by P*1 / P0, is shown by the solid line 308.

[0053] In response to the torque demand, a command 302 for the total pressure ratio is determined and issued to the primary compression device. However, due to the slow response time of the primary compression device (e.g., turbo lag), the actual pressure ratio 304 achieved at the primary compression device is lower, and initially, the pressure ratio deficit 306 may be significant. If this pressure ratio deficit is not addressed, the temporary boost response will be adversely affected. The pressure ratio deficit is addressed by issuing commands 308 to the auxiliary compression device. In particular, a larger portion of the total pressure ratio during the initial part of the boost response is dynamically allocated to the auxiliary compression device due to the larger pressure ratio deficit that occurred at the primary compression device.Then, when the primary compression device starts up, a larger portion of the total pressure ratio is supplied by the primary compression device, and the contribution of the auxiliary compression device is dynamically reduced by the phasing out of the pressure ratio commanded to the auxiliary compression device. As a result, the overall reliance on electrical assistance is minimized, while the transient charging response is improved.

[0054] With reference to Fig. 2. If the boost pressure at 218 is within the target TIP threshold but still below the target TIP, the procedure at 222 involves providing negative electric motor torque from the electric motor to the auxiliary compressor. This allows the boost pressure to move towards the target TIP, reducing the likelihood of excess pressure. Additionally, the electric motor's assistance is reduced earlier, improving fuel efficiency. Furthermore, energy recovery via the electric motor is enabled by operating it as a generator in a region where excess pressure could occur, further improving fuel efficiency while also enhancing the boost response. The control system can employ a lead compensator module, as is the case here. Fig. Step 5 is further described to determine the point in time (e.g., in relation to turbine speed or boost pressure) at which electrical assistance from the electric motor is cut off and when the electric motor transitions to operating as a generator. In one example, the electric motor can be run as a generator at a speed based on the predicted surplus. Then the routine ends.

[0055] As already mentioned, the charging system can be described as follows: P2=P0∗P1P0∗P2P1 where P0 is the inlet pressure to the first charging device and P1, P2 is the outlet pressure from the first and second charging devices (TIP). P1*, P2* This specifies the desired pressure target for the first and second charging devices. In the configuration described above, the first charging device is a temporary (auxiliary) device, such as an electric compressor, and the second charging device is the primary device, such as a turbocharger. The control reference of the first charging device is determined as follows: P1*P0=P2*P0*min{1,P1P2} or P1*=P2**min{1,P1P2}

[0056] A clamp is included to prevent the desired pressure target for the first charging device from exceeding that of the second charging device if P1 > P2, which could occur shortly after throttle opening. The main charging device is intended to provide the entire desired boost pressure. For this reason, the target for the second device should P2* Always provide the full pressure ratio (from the environment), regardless of the condition of the auxiliary device. In this case: P2P1→P2∗P0 or P2×P0P1→P2∗, if limt→∞P1P0=1

[0057] Thus, a basic control can be overridden so that it does not operate the auxiliary charging device or operates the auxiliary charging device continuously, and vice versa for the main charging device.

[0058] If the control unit is conservatively calibrated to minimize P2 excess, the boost pressure response can become slower than the system's maximum capability. Therefore, using a pre-compression compensator along with aggressive control unit calibration improves the turbo system's transient response. Meanwhile, the pre-compressor requests a reduction in engine speed before P2 P2* approximates. The command enables the energy recovery mode of the electric motor, thereby maximizing the energy recovery window.

[0059] The advantage compensator in the Laplace domain can be expressed as follows: Y(S)U(S)=as+1τs+1

[0060] Input U is the pressure ratio error of the electric compressor: U=P1∗P0−P1P0

[0061] The following transformation is derived for implementation in the discrete system: xk=(1−f)xk−1+fuk,f=Tsτ+Ts yk=(1−r)xk+ruk,r=aτ≥1 where f is the time constant in the discrete domain, r is the lead ratio, and T s The execution rate is.

[0062] The output of the lead compensator is truncated to allow a specification of the range of lead actions on U in increasing or decreasing directions. yk˜=clip(uk−Δ1,yk,uk+Δ2)

[0063] An example of the advantage compensation of the pressure ratio at the electric compressor and the resulting reduction of the pressure excess and the accelerated enabling of energy recovery at the electric motor is given here with reference to Fig. 4 described.

[0064] With brief reference to Fig. 4 represents the Fig. This demonstrates how lead compensation is used together with dynamic pressure ratio mapping to improve the transient charging response while maximizing energy recovery opportunities. Fig. includes Fig. . The Fig. Figure 408 represents changes in the electrical assistance commanded to an electric compressor (on the y-axis) over time (along the x-axis) with respect to the assignment of a pressure ratio (along the y-axis) over the same time frame (along the x-axis) between a turbocharger and an electric compressor, as represented in Figure 402. The total commanded pressure ratio, based on the torque demand and represented by P2* / P0, is shown by the solid line 408. Thus, this is the pressure ratio commanded to the primary compression device, in this case a turbocharger. The actual pressure ratio achieved via the supercharging system is represented by P2 / P0. oThe speed without lead compensation (without LC) is shown in curve 410 and is to be compared with P2 / P0, which is achieved with lead compensation (with LC), shown in curve 412. The electric motor speed commanded to the electric compressor without lead compensation (without LC) is shown in curve 430 and is to be compared with the electric motor speed command with lead compensation (with LC), shown in curve 434. The portion of the electric motor speed command received via the controller's lead compensation module is shown in curve 432.

[0065] Before t1, the engine operates without forced induction, and therefore the commanded pressure ratio is low. At t1, the boost pressure demand increases in response to an increase in the driver's torque demand. Consequently, the command for the total pressure ratio (408), generated based on the torque demand, increases. This is the signal commanded to the turbocharger to achieve a steady-state target TIP. However, due to the turbocharger's slow response time, there is a temporary pressure ratio deficit, which can be addressed by activating the electric compressor and dynamically allocating a larger portion of the total commanded pressure ratio to it. Specifically, at t1, a pressure ratio command is delivered to the electric compressor dependent on the boost pressure (for example, based on the corresponding airflow deficit) resulting from the turbocharger's slow response.Accordingly, the electric motor speed of the electric compressor is increased (430, 434), which leads to an increase in the pressure ratio at the compressor. At this point, the electric motor operates in electric motor mode to supply energy to the compressor.

[0066] As the turbine spins up, it is able to address a larger portion of the command for the overall pressure ratio. After t2, when the pressure ratio at the turbocharger is within a threshold of the overall pressure ratio, but still below the target pressure ratio, the lead compensation module sends a signal (432) to the electric motor to reduce its speed and provide negative electric motor torque. At this point, the electric motor operates in a generating mode to recover energy from the compressor. As a consequence of the lead compensation occurring before the target overall pressure ratio is reached, the pressure ratio at the turbocharger (412) moves towards the target pressure ratio.If the lead compensation were not provided, the pressure ratio at the turbocharger (410) would exceed the overall pressure ratio (i.e., P2 / P0 would exceed P2* / P0), resulting in a torque error. This can affect drivability. Furthermore, the pressure ratio at the compressor is reduced in a timely manner as a consequence of the lead compensation occurring before the target overall pressure ratio is reached. If the lead compensation were not provided, the pressure ratio at the compressor (420) would also exceed the commanded pressure ratio (i.e., P1 / P0 would exceed P1* / P0). This would not only lead to a decrease in fuel efficiency, as the electric compressor would operate longer than necessary, but also to a further decrease in fuel efficiency due to the lack of energy recovery.Instead, the pressure excess is addressed by providing earlier advance compensation through torque absorption at the electric motor. As a result, the overall transient response of the turbocharged motor is improved, while also extending the energy recovery window for the electric motor.

[0067] It is understood that the electric compressor can be a temporary device that is not continuously controlled. A monitoring controller can coordinate the operation of the electric compressor and its bypass valve. The main task of the monitoring controller can be to determine when to activate and deactivate the electric compressor and its bypass valve to meet control requirements subject to system constraints and hardware protection. At a high level, the electric compressor is activated and the bypass valve is closed when the activation criteria are met and no system faults are observed. Once the deactivation criteria are met or system faults are observed, the electric compressor is deactivated and the bypass valve is opened.

[0068] Several considerations can influence the design of the activation strategy. First, the control unit may activate the electric compressor only when necessary, such as when the vehicle's drivability is unacceptable due to the turbocharger's slow response. Second, proactive action may be desirable if the strategy doesn't need to wait until unacceptable drivability is observed. Finally, the control unit may aim to reduce unwanted activation in response to changes in the driver's mood.

[0069] Since the boost pressure ratio deficiency (Π*) can be used as an index to determine the driver requirement deficiency (which represents drivability), proactive action can be achieved by considering the rate of change of Π*, and the activation threshold (f2) is determined as a function of Π* as follows: d(Π*)dt>f2(Π*)

[0070] Two first-order low-pass filters (H lp ) both at Π* and at d(Π*)dt are added to reduce a “false positive” activation in the event of mood changes in the driver, such as when the driver aggressively presses the accelerator pedal, but quickly removes the command as follows: Hlp_k1,2=(1−h1,2)Hlp_k1,2−1+h1,2Πk∗ h1,2 =Tsτ1,2+TS where h 1,2 This involves two time constants in the discrete domain.

[0071] The activation strategy is illustrated by an exemplary acceleration curve at Fig. 7 illustrates. The at Fig. The curves shown are created with the X-axis representing the filtered boost pressure deficit and the Y-axis representing the filtered rate of change of the boost pressure deficit. The activation threshold, represented by the solid line 702, is determined as a function of the filtered Π*. The acceleration curve for the case where no electrical assistance from the electric motor is required is shown by the transparent circles 706. The acceleration curve for the case where electrical assistance from the electric motor is required is shown by the filled circles 704. The calibration shows that the electric compressor is activated when the rate of change of Π* is high, even if the absolute Π* is low. Conversely, if Π* gradually develops to an unacceptable level, the strategy activates the electric compressor.The main criteria for deactivating the electric compressor are when the turbocharger is able to maintain the desired charge or the boost pressure deficiency is reduced and is below a threshold, such as when: Π*≤α where α is a calibratable constant.

[0072] It is understood that, while the examples discussed above relate to a configuration involving a turbocharger coupled to an electric compressor, this is not intended to be limiting. In other examples, the turbocharger may be configured with electrical assistance (e.g., as an e-turbo with an electric motor coupled to the compressor, turbine, or turbocharger shaft). Further examples may relate to supercharged engines featuring staged compressors or staged turbochargers, at least one of which has electric assistance.

[0073] With reference to Fig. Figure 5 shows a block diagram of an exemplary control architecture for a supercharging system with a high-frequency, electrically assisted compressor and a low-frequency compressor. For example, the control architecture can be applied to a motor system that uses an electric compressor (e.g., first compressor 110 from Fig. 1) has a connection to an engine intake duct upstream of a turbocharger compressor (e.g. second compressor 114 from Fig. 1) is coupled. The control architecture can be controlled from a controller (e.g., controller 12). Fig. 1) be used while a tax procedure, such as procedure 200 from Fig. 2, is performed to regulate the boost pressure output.

[0074] The electric compressor control (C1) includes a dynamic distributor (D1) that divides the desired boost pressure control reference; a state machine (A1) that manages the operation of the electric compressor system; a closed-loop control (I1) consisting of a model-based forward feedback function (F1) and a feedback control (H1) for calculating the command for the desired speed of the electric compressor.

[0075] The forward linkage control action (n eSC_ff The speed of the electric compressor is based on the steady-state compressor map provided by the supplier. This compressor map is transformed to determine the desired compressor speed based on the inputs of the corrected mass flow rate (ṁ). korr ) and the desired pressure ratio (P1*P0). neSC_ff=f1(P1∗P0,m˙korr) The mass flow rate (ṁ) is estimated as the desired cylinder air flow rate, then adjusted to the reference pressure (P). ref ) and the temperature (T ref ) corrected. m˙korr=m˙T0TrefP0Pref

[0076] The desired boost pressure reference of the electric compressor is determined by the desired throttle inlet pressure. (P2*) The signal is received and processed by a high-pass filter (H1). The frequencies that pass through the high-pass filter are those frequencies to which the turbocharger cannot respond; in other words, the turbocharger's limitations. A closed-loop controller C1 determines the command for the desired speed (n). eSC ) of the electric compressor. C2 is the control unit for the turbocharger, which determines the wastegate position (θ). wg ) determined. Due to the dynamics between the wastegate and the turbocharger speed, there is generally no need for a low-pass filter. P2* C2 can be added to turbocharger control, however, one can be added if needed. Furthermore, C2 is designed so that the wastegate is saturated during large transitions and only adjusts its response as the throttle intake pressure approaches the desired target. At this point, the control actions of C1 are largely reduced due to the high-pass filter, which ensures minimal interaction between the two actuators.

[0077] A proportional feedback control (H1) is implemented to account for a mismatch in the plant model (the representation of the electric compressor). Steady-state charge tracking is designed to be provided by the main turbocharger. For this reason, there is no integral behavior in the feedback control. A lead compensator is added to shape the closed-loop control response, since the speed control of the internal-loop electric compressor may have a different bandwidth for controlling the speed in increasing or decreasing directions.

[0078] The monitoring controller (A1) is designed to coordinate the electric compressor and its bypass valve. Its primary function is to determine when to activate and deactivate the electric compressor and its bypass valve to meet control requirements subject to system constraints and hardware protection. At a high level, the electric compressor is activated and the bypass valve is closed when the activation criteria are met and no system faults are observed. Once the deactivation criteria are met or system faults are observed, the electric compressor is deactivated and the bypass valve is opened.

[0079] A desired boost pressure ratio at both compressors (P2*P0) together with a measured (e.g. achieved) pressure ratio at the turbocharger compressor (P2P1) are input into the dynamic distributor D1. The pressure ratio at the turbocharger compressor can be controlled by the turbocharger control unit C2, which receives the desired boost pressure ratio at both compressors as well as the measured pressure ratio at the turbocharger compressor as feedback. The control unit C2 then generates a signal to adjust the degree of opening of a turbocharger wastegate actuator (θ). wg ), which is then sent to turbocharger G2, resulting in the pressure ratio at the turbocharger compressor. P2P1 This allows the opening of the turbocharger wastegate actuator to be controlled based on the desired boost pressure ratio and the achieved boost pressure ratio at the turbocharger compressor. For example, if the desired boost pressure ratio increases, the degree of opening of the wastegate actuator can be reduced to allow a larger portion of the exhaust gas to flow through a turbocharger turbine rather than the wastegate actuator, thereby increasing the turbine speed and consequently the boost pressure ratio at the turbocharger compressor.

[0080] The dynamic distributor D1 uses the pressure ratio at the turbocharger compressor and the overall desired boost pressure ratio to achieve a desired pressure ratio. (P1*P0) to determine the compressor compressor, for example using the functions described above. The desired pressure ratio for the compressor, as well as the measured pressures P0 and P2 and the desired boost pressure. P2* The values ​​are fed into a state machine A1, which is a monitoring controller for a discrete event system. State machine A1 determines whether P2 is insufficient enough (e.g., greater than a threshold deficit) to trigger the activation of the electric compressor. Additional criteria ensure that operating the electric compressor would not violate other system constraints, such as those caused by faults, temperature, or the availability of electrical power. Hysteresis is also added to the activation criteria as follows: P2*P0−P2P1≥hysteresis to avoid a power cycle of the system.

[0081] Once the activation of the electric compressor is triggered, the desired pressure ratio of the compressor, along with a desired mass flow rate (ṁ), is input into a model-based feedforward control F1. For example, a model-based feedforward control F1 can look up a corresponding compressor speed from a compressor mapping. The corresponding compressor speed, n eSC_ff , is then output as an addition element 518.

[0082] The desired pressure ratio of the compressor is also fed into an addition element 520 together with a feedback signal that displays the actual pressure ratio of the compressor. (P1P0) This concerns a value that is entered and subtracted from the desired pressure ratio of the compressor as part of an external circuit control system C1. The result is fed into an error feedback control to adjust the compressor speed and regulate inaccuracies in the compressor mapping. A feedback reaction that adjusts the compressor speed, n eSC_fb , which is generated by the fault feedback control, is then added to the addition element 518, which controls the speed of the electric compressor n eSC for the given operating conditions. The rotational speed of the electric compressor can be converted into a corresponding electrical signal (e.g., duty cycle) which is applied to an electric motor of the electric compressor G1 to control the pressure ratio at the compressor. (P1P0) to generate. Thus, the speed of the compressor can be adjusted based on P2*P0 and P2P1 and in particular a lack between P2P1 and P2*P0 will be continuously updated.

[0083] With reference to Fig. 6 is an exemplary method 600 for operating a supercharged engine system with an electric compressor (e.g. the compressor 13 from Fig. 1), upstream of a turbocharger (e.g. turbocharger 15 from Fig. 1) is shown in stages. In this case, the turbocharger is configured as a primary charging device and the compressor is configured as an auxiliary charging device.

[0084] In procedure 602, procedure 200 involves estimating and / or measuring engine operating conditions. For example, assessed operating conditions may include engine speed, pedal position, driver torque demand, manifold absolute pressure, manifold airflow, manifold air temperature, ambient conditions (such as ambient temperature, air pressure, and humidity), engine coolant temperature, etc. For example, the air pressure may be measured from a pressure sensor, such as pressure sensor 58. Fig. 1 can be measured.

[0085] In procedure 604, procedure 600 involves determining whether supercharging is requested. In one example, supercharging might be requested at medium to high internal combustion engine loads. In another example, supercharging might be requested in response to pedal operation by a driver or an increase in the driver's torque demand. If no supercharging is requested, such as when the engine load is low or the driver's torque demand is low, procedure 600 proceeds to 606 and involves operating the engine with natural intake (e.g., manifold vacuum). Operating the engine with natural intake cannot involve activating the staged supercharging devices. For example, an electric motor may be used to drive the electric compressor (e.g.,electric motor 108) is not supplied with power and the turbocharger wastegate actuator can be commanded to the fully open position to direct some of the exhaust gas through the wastegate, while a turbine of the turbocharger (e.g. turbine 116 from . Fig. 1) is circumvented. Following 606, the procedure ends in 600.

[0086] When boosting is requested at 604, such as in response to a pedal actuation event, procedure 600 transitions to 608 and involves generating a command for a desired pressure ratio (e.g., a target pressure ratio) for the turbocharger based on the boost command. The desired pressure ratio, defined as P2*P0, is a ratio of a desired outlet pressure of a compressor of the turbocharger (e.g., of the second compressor 114 from Fig. 1), which is also equal to the desired boost pressure (or desired TIP) relative to P0, which is an inlet pressure of a compressor of the electric compressor (e.g., the first compressor 110 from Fig. 1) represents. For example, P0 can be equal to the atmospheric pressure (e.g., as measured by pressure sensor 58). Fig. 1 measured).

[0087] In the 610, the procedure involves reducing the opening of the turbocharger wastegate based on the pressure command for the overall pressure ratio. For example, if the pressure ratio command increases, the wastegate opening can be reduced. In one example, the wastegate is completely closed. Closing the turbocharger wastegate allows the entire exhaust gas flow to pass through the turbocharger turbine, accelerating the turbine's spin-up. Optionally, a compressor recirculation valve (such as the CRV 62 from [reference missing]) can also be used. Fig. 1) are closed, thus reducing the pressure loss at the turbocharger compressor. Compressed air then flows through the turbocharger compressor to the engine. At this point, the bypass valve of the electric compressor is open, causing air to flow to the turbocharger compressor while the compressor is bypassed.

[0088] In case 612, the procedure involves calculating a boost pressure deficit at the turbocharger. This boost pressure deficit can be caused by a lack of boost pressure. (P2*−P2), which is a difference between the desired boost pressure and the measured throttle intake pressure, as well as a rate of change of the boost pressure deficiency. (d(P2*−P2)dt) This can be determined. For example, due to turbo lag, the turbocharger may not be able to reach the desired boost pressure, as in relation to Fig. 2 described. The control system can also determine an airflow deficiency at the turbocharger (inlet), corresponding to the boost pressure deficit, or use pressure ratios instead of differential pressures. In alternative examples, the boost pressure deficit is based on a ratio of the desired boost pressure to the measured throttle inlet pressure instead of the difference. In other words, the boost pressure deficit is based on the desired boost pressure relative to the measured throttle inlet pressure.

[0089] In example 614, the procedure involves closing the ESBV in response to the indication that a boost pressure deficit exists. By (completely) closing the ESBV, the electric compressor can be included in the intake flow path, and intake air flows through the electric compressor to the turbocharger compressor. This means that the airflow through the compressor is increased. In other examples, the ESBV can be closed in response to the magnitude of the boost pressure deficit, such as when the magnitude exceeds a threshold, like a threshold above which a transient boost response is adversely affected. For example, it can be determined whether an absolute magnitude of the boost pressure deficit exceeds the threshold, or whether a rate of change of the boost pressure deficit... d(P2*−P2)dt exceeds the threshold, whereby the threshold is calibrated depending on the boost pressure deficiency: d(P2∗−P2)dt>f2(P2∗−P2) where f2 represents a function. For example, the threshold can decrease as the boost pressure deficit increases. The threshold can define an allowable amount of boost pressure deficit above which the engine's peak power and torque output may be affected. Furthermore, the threshold can be set so that the amount of additional power and torque provided by operating the electric compressor outweighs the amount of electricity consumed by the electric compressor. Additionally, both the boost pressure deficit and its rate of change can be filtered through a first-order low-pass filter. Filtering the boost pressure deficit and / or its rate of change can reduce unnecessary activation of the compressor, such as that caused by the driver's mood (e.g.,Applying an accelerator pedal for a shorter period than a threshold duration). If the boost pressure deficit is not greater than the threshold, the ESBV can be kept open, the electric compressor can remain deactivated, and compressed air can flow to the engine only via the turbocharger compressor, while the compressor is bypassed.

[0090] In the 616, the procedure, in response to the boost pressure deficit, involves operating the electric compressor using electrical assistance to enhance the temporary boost response. Actuating the electric motor coupled to the compressor serves to accelerate the compressor, thereby increasing the boost pressure supplied to the engine. For example, accelerating the compressor can involve rotating the compressor via the electric motor using power from a battery (e.g., system battery 45). Fig. 1) include power drawn. For this reason, the compressor may be able to provide charging for a limited duration, the duration being limited by the state of charge of the system battery that powers the electric motor. An amount of power (or duty cycle of power) commanded to the electric motor may be based on a pressure ratio assigned to the compressor depending on the deficit. For example, the controller may determine a desired compressor pressure ratio based on the airflow deficit. The controller may further input the calculated compressor pressure ratio and MAF into a lookup table to determine the desired compressor speed.The controller can then input the compressor speed into an additional lookup table or function to output the electric motor speed and input a corresponding amount of power (or duty cycle of power) to provide to the electric motor to generate the target pressure ratio at the compressor.

[0091] The desired compressor pressure ratio, P1*P0, can be cut to prevent the desired pressure target of the compressor from being reached. (P1*) This desired value of the turbocharger is exceeded when P1 is greater than P2, which can occur shortly after the throttle opens. Therefore, a control reference for the compressor can be described as follows: P1*P0=P2*P0×min{1,P1P2} or P1*=P2*×min{1,P1P2} which is also the same as the pressure ratio deficit (or pressure deficit, if P1* instead of P1*P0 is determined) of the turbocharger compressor. This means that the compressor can be controlled based on the turbocharger's boost pressure deficit (or boost pressure deficit) to achieve the desired boost pressure ratio. P2*P0 (or boost pressure) P2* to provide. Compressed air then flows through the turbocharger compressor and the compressor compressor to the engine. Thus, the turbocharger compressor outlet pressure, P2, contains pressure generated by both the compressor compressor and the turbocharger compressor.

[0092] In procedure 618, this involves determining whether the actual boost pressure achieved at the turbocharger outlet is within a threshold of the target boost pressure or TIP. The threshold can be determined based on the target TIP or the overall commanded pressure ratio and can be adjusted to reduce the possibility of excess pressure. For example, the threshold may be higher at higher pressure ratios.

[0093] If the actual boost pressure is lower than the desired TIP by more than the threshold amount, procedure 622 involves continuing to provide electrical assistance via the compressor while the steady-state boost pressure is provided by the turbocharger. Additionally, the control unit can maintain or further reduce the wastegate opening (if possible). Furthermore, the control unit can maintain or further increase the electric motor speed (if possible).

[0094] If the actual boost pressure is only slightly below the desired TIP by the threshold amount, the control unit can apply lead compensation and cut off the electric assist. Specifically, the electric motor's speed can be reduced to bring the boost pressure closer to the target TIP with reduced excess. Additionally, the control unit can switch the electric motor to generator mode and operate the generator to apply negative torque to the compressor, thus slowing it down and recovering energy that would otherwise have caused the boost pressure excess.

[0095] At 624, it can be confirmed that the target boost pressure has been reached. If the target boost pressure is not reached, the procedure at 626 further involves adjusting the wastegate opening and / or the generator speed. For example, the actuators can be adjusted to provide a target speed profile or curve for the target boost pressure. Otherwise, if the target boost pressure has been reached, the procedure at 628 involves disabling the electric motor / generator. In this procedure, the electric motor coupled to the supercharger can be deactivated by a signal sent from the control unit to an electromechanical actuator of the electric motor, which reduces the electric motor's rotational speed. Additionally, the ESBV can be actuated to an open (e.g., fully open) position to allow intake air to flow to the engine via the turbocharger compressor while bypassing the supercharger.Subsequently, compressed air can only be supplied to the engine via the turbocharger compressor and not via the compressor compressor.

[0096] In this way, by temporarily and dynamically operating the compressor based on the pressure ratio of the turbocharger compressor, boost pressure deficiencies (e.g., due to delays in the turbocharger turbine's spool-up) are reduced. Furthermore, the compressor is activated for a longer period, and power consumption is minimized, thus reducing electrical power consumption and increasing fuel efficiency. The procedure ends after 628.

[0097] Fig. Figure 8 presents a prophetic exemplary diagram 800 of the dynamic mapping of pressure ratios to provide coordinated control of the turbocharger and the electric compressor, as per the method from Fig. 2 (and Fig. 6) and using the tax architecture from Fig. 5. The accelerator pedal position is shown in curve 802, the actual throttle inlet pressure (TIP) is shown with the solid line in curve 806 relative to the desired TIP with the dashed line in curve 805, an achieved pressure ratio at a turbocharger compressor. (P2P1) is in course 808 relative to a desired overall boost pressure ratio (P∗2P0), which is shown in sequence 804, a turbine speed of the turbocharger is shown in sequence 810, a pressure ratio achieved at the electric compressor compressor (P1P0) The electric motor speed of the electric compressor is shown in graph 812, the commanded speed of the electric compressor motor is shown in graph 816, while graph 817 shows the generator activation, the degree of opening of an electric compressor bypass valve (ESBV) is shown in graph 818, and the degree of opening of a turbocharger wastegate is shown in graph 820. For all of the above, the x-axis represents time, with time increasing from left to right along the x-axis. The y-axis represents the labeled parameter, with values ​​increasing from bottom to top. In the present example, the electric compressor is located upstream of the turbocharger compressor, as in the engine system from Fig. 1.

[0098] Before time t1, the engine runs without supercharging due to lower driver demand (curve 802) (curve 806), requiring a lower TIP (curve 805). Thus, the actual pressure ratio of the turbocharged compressor (TC) (curve 808) and the electric supercharger compressor (curve 812) are at an output value (e.g., approximately 1), indicating that the pressure upstream of each compressor is equal to the pressure downstream of each compressor, since air is not compressed by each compressor. Because the electric supercharger (ES) is not activated, the commanded speed of the electric supercharger remains at zero (curve 816), and the ESBV is fully open (curve 818). As a result, intake air bypasses the electric supercharger compressor instead of being directed to it, as described in the previous diagram. Fig.1 further described. Furthermore, the turbocharger wastegate is fully open (curve 820), which keeps the speed of the turbocharger turbine low (curve 810), as the exhaust gas bypasses the turbine through the open wastegate.

[0099] At time t1, the driver depresses the accelerator pedal, as shown by the increase in the accelerator pedal position (curve 802), moving the engine from naturally aspirated to supercharged operation. A desired amount of boost pressure, as reflected by an increase in the desired TIP (curve 805), is determined based on the amount of torque requested by the driver, and the desired overall pressure ratio at the supercharged engine system (curve 804) increases accordingly. The turbocharger is controlled by a command based on the overall desired boost pressure ratio. To provide the desired overall boost pressure ratio in steady state, the turbocharger wastegate closes completely (curve 820), directing all exhaust gas through the turbocharger turbine (rather than the wastegate) to spin the turbine.As a result, the turbine speed (curve 810) begins to increase. However, due to the slow response time of the turbine speed, the turbocharger is unable to achieve the desired overall pressure ratio (see difference between curves 804 and 808) and the desired TIP. The actual pressure ratio of the turbocharger compressor (curve 808) is below the desired overall boost pressure ratio (curve 804) between time t1 and time t2.

[0100] A pressure ratio deficit and a corresponding airflow deficit at the turbocharger are determined based on the desired overall pressure ratio (804) relative to the actual boost pressure ratio at the turbocharger (808) (e.g., based on the difference as in this example or based on a ratio). A pressure ratio corresponding to the airflow deficit is then commanded to the compressor (curve 812), so that the combination of the pressure ratio at the compressor (812) and the pressure ratio at the turbocharger (808) together can correspond to the overall desired boost pressure ratio (curve 804). Thus, between t1 and t2, when the turbine speed is lower, a larger portion of the overall boost pressure ratio is allocated to the compressor, since a smaller portion is supplied by the turbocharger.

[0101] In response to the boost pressure deficit exceeding the threshold, the electric compressor is activated shortly after time t1 to replenish the deficit while the turbine spins up. Activating the electric compressor involves closing the ESBV (Curve 818) to direct intake air to the electric compressor and supplying power to an electric motor that drives the compressor, during a duty cycle that operates the electric motor at a speed (Curve 816) based on the turbocharger compressor's boost pressure deficit. Specifically, the commanded speed of the electric motor coupled to the compressor is selected to provide the desired pressure ratio at the compressor. The desired pressure ratio of the electric compressor increases as the turbocharger compressor's boost pressure deficit increases.Between time t1 and time t2, a larger portion of the total boost pressure ratio (curve 806) is provided by the boost pressure generated by the electric compressor, with the electric compressor's pressure ratio increasing rapidly (curve 812) when the electric motor is activated. A smaller portion of the total boost pressure ratio is provided by the turbocharger's pressure ratio (curve 808) due to the lower rotational speed of the turbocharger turbine (curve 810).

[0102] Between time t1 and time t2, the turbine speed increases slowly (curve 810). However, the pressure ratio at the turbocharger compressor (curve 808) still falls short of the total achieved boost pressure ratio (curve 806). Between time t2 and time t3, the turbine speed (curve 810) increases more rapidly, with a corresponding increase in the pressure ratio at the turbocharger compressor (curve 808) and a corresponding decrease in the boost pressure deficit. As the pressure ratio at the turbocharger compressor (curve 808) increases, the pressure ratio at the compressor decreases, so that the total achieved boost pressure ratio (curve 806) equals the desired boost pressure ratio.Then, once the achieved total boost pressure ratio (curve 806) is close to the desired boost pressure ratio (804), the pressure ratio at the compressor is gradually reduced (by adjusting a duty cycle of the electric motor) as the pressure ratio at the turbocharger increases. Between t2 and t3, an increasing portion of the total boost pressure ratio (curve 806) is provided by the boost pressure generated by the turbocharger, and the remaining portion is provided by the boost pressure generated by the electric compressor.

[0103] At time t3, the actual TIP (curve 806) is within a threshold of the desired TIP (curve 805) due to the boost pressure generated by both the turbocharger compressor and the electric compressor. To reduce excess boost pressure, the control system applies a lead compensation between t3 and t4 to reduce the speed of the electric motor before P2 P2* approximates. In particular, before the actual TIP reaches the target TIP, the electric motor brakes the compressor to reduce the compressor speed and the ES pressure ratio. The generator command (curve 817) implies that the electric motor operates in generator mode, allowing energy recovery at the electric motor / generator coupled to the compressor. The turbocharger wastegate can begin to open between time t3 and time t4 (curve 820). If this lead compensation had not been provided, the TIP would have exceeded the desired value, resulting in torque errors, and an opportunity for energy recovery would be lost.

[0104] At time t4, the turbocharger compressor pressure ratio (curve 808) reaches the desired overall pressure ratio (curve 804). Therefore, the desired pressure ratio at the compressor (curve 812) is reduced to an output value (e.g., approximately 1), and the electric compressor is deactivated (e.g., no power is supplied to the electric motor driving the compressor). The ESBV (electrical self-contained blower valve) opens (curve 818) to direct intake air directly to the turbocharger compressor instead of the compressor, and the commanded speed of the electric compressor (curve 816) is reduced to zero. As the compressor slows down, the pressure ratio at the compressor (curve 812) returns to the output value.Furthermore, the degree of opening of the turbocharger wastegate actuator is increased (curve 820) in response to the turbocharger compressor's boost pressure ratio (curve 808) reaching the desired boost pressure ratio (curve 804). This maintains the turbine speed (curve 810) to provide the desired boost pressure target with feedback regarding the achieved turbocharger compressor boost pressure ratio (curve 808).

[0105] At time t5, the accelerator pedal position decreases (curve 802). Consequently, the desired overall boost pressure ratio decreases (curve 804). To reduce the boost pressure, the turbocharger wastegate actuator (curve 820) opens further to slow down the turbocharger turbine (curve 810) and thus the turbocharger compressor. As a result, the achieved pressure ratio at the turbocharger compressor (curve 808) decreases. Since the electric compressor is deactivated, the turbocharger compressor also supplies the entire boost pressure.

[0106] At time t6, the accelerator pedal position continues to decrease (curve 802), for example, due to the pedal being released. The desired overall boost pressure ratio (curve 804) decreases to the initial value when boosting is no longer required, based on driver demand. The turbocharger wastegate opens fully (curve 820) to reduce the boost pressure, which slows the turbocharger turbine (curve 810) down to an initial speed. The turbocharger compressor speed decreases accordingly, thus decreasing the amount of boost pressure generated by the turbocharger compressor. As a result, the pressure ratio at the turbocharger compressor (curve 808) decreases to the initial value (e.g., approximately 1). As described above, the overall boost pressure ratio (curve 806) also decreases to the initial value, as the turbocharger compressor is supplying all the boost pressure.

[0107] In this way, a turbocharger compressor coupled downstream of a supercharger can be operated via a wastegate adjustment to provide an overall pressure ratio between a supercharger inlet and a turbocharger compressor outlet based on the driver's torque demand, while the supercharger operation is dynamically adjusted via an electric motor based on a real-time pressure ratio (or airflow) deficiency at the turbocharger compressor. In this context, operating the turbocharger compressor via the wastegate adjustment can involve reducing the wastegate opening as the driver's boost demand increases, thereby increasing the speed of a turbocharger exhaust turbine and raising the overall pressure ratio.In another example, the real-time pressure (or airflow) deficit at the turbocharger compressor can be estimated based on the actual pressure ratio at the turbocharger compressor relative to the desired overall pressure ratio. The actual pressure ratio at the turbocharger compressor changes as the exhaust turbine spins up. An engine control unit can adjust the compressor's operation by increasing a positive electric motor torque supplied to the compressor. This increases the compressor's speed as the airflow deficit increases, while maintaining an actual pressure ratio at the compressor below a threshold pressure. This adjustment is based on the desired overall pressure ratio and, further, on the actual pressure ratio at the turbocharger compressor.Furthermore, in response to a difference (or ratio) between the actual throttle inlet pressure and a target throttle inlet pressure exceeding a threshold, based on the driver's boost demand, the control system can increase negative electric motor torque supplied to the compressor to reduce the compressor speed. In another example, the compressor speed can be reduced in response to excess boost pressure by supplying negative electric motor torque while maintaining the reduced wastegate opening. Conversely, the compressor speed can be increased in response to underboost pressure by supplying additional positive electric motor torque while further reducing the wastegate opening.Adjusting the operation of the compressor based on the lack of airflow can, for example, involve adjusting the compressor output independently of the position of the wastegate and independently of the turbine speed of the turbocharger.

[0108] In this way, an electric compressor can be activated in response to a boost pressure deficit, while boost is provided by a turbocharger in a turbocharging system to achieve the desired boost pressure. Both the turbocharger and the electric compressor are controlled based on pressure ratio measurements. The technical benefit of dynamically adjusting the pressure ratio assignment to the electric compressor based on the turbocharger's boosting capacity in real time is that the boost response can be improved. In particular, the electric compressor can be activated only as long as necessary to assist the turbocharger, thus minimizing the electric assistance from the compressor. By conserving electrical power, fuel efficiency is improved.By more aggressively calibrating the pressure ratio commanded to the electric compressor and turbocharger, boost demand can be met more effectively. Providing positive electric motor torque to the electric compressor when the turbocharger's boost capacity is equal to or less than the actual boost pressure can address turbo lag. The technical benefit of switching to negative electric motor torque when the boost pressure is within a certain threshold of the target pressure is that the boost pressure can move towards the target pressure without creating a pressure surge. Additionally, the electric motor's energy recuperation capability is improved. Overall, boost pressure can be delivered more quickly and efficiently.

[0109] An exemplary method comprises: commanding an overall pressure ratio for a first compression device of an engine intake based on the driver's torque demand; and adjusting the timing of the electrical intervention provided to a second compression device of the engine intake based on a lack of airflow at the first compression device. In the preceding example, the method additionally or optionally comprises adjusting the amount of electrical intervention provided to the second compression device of the engine intake based on the lack of airflow at the first compression device. In any or all of the preceding examples, the timing and amount of electrical intervention are additionally or optionally adjusted to dynamically vary a pressure ratio at the second compression device.In any or all of the preceding examples, the adaptation additionally or optionally includes: operating the electric motor in an electric motor mode to provide positive electric motor torque to the second compression device while the airflow deficiency at the first compression device is higher than a threshold, and operating the electric motor in a generator mode to provide negative electric motor torque to the second compression device while the airflow deficiency at the first compression device is lower than the threshold.In any or all of the preceding examples, providing positive electric motor torque to the second compression device additionally or optionally includes accelerating the second compression device and increasing the pressure ratio at the second compression device, and providing negative electric motor torque to the second compression device includes accelerating the second compression device and decreasing the pressure ratio at the second compression device. In any or all of the preceding examples, the threshold is additionally or optionally based on the total pressure ratio commanded to the first compression device, and the throttle inlet pressure during electrical intervention is below a target boost pressure based on the driver's torque requirement.In any or all of the preceding examples, adjusting additionally or optionally involves further disabling electrical intervention in response to the throttle inlet pressure being at the target boost pressure. In any or all of the preceding examples, the first compression device is a turbocharger, the second compression device is an electric compressor, and the first compression device is staged downstream of the second compression device in the engine inlet. In any or all of the preceding examples, commanding an overall pressure ratio for the first compression device additionally or optionally involves adjusting the opening of an exhaust wastegate valve coupled to an exhaust turbine of the turbocharger.In any or all of the preceding examples, the airflow deficiency is additionally or optionally estimated in real time based on an actual pressure ratio at the first compression device relative to the commanded total pressure ratio, the actual pressure ratio at the turbocharger compressor changing as the exhaust turbine spins up.

[0110] Another exemplary procedure includes: adjusting the operation of a first inlet compression device based on a target boost pressure; commanding positive torque from an electric motor to an inlet compression device while the difference between an outlet pressure of the first compression device and the target boost pressure is higher than a threshold; and commanding negative torque from the electric motor to the second inlet compression device while the difference is less than the threshold.In the preceding example, the first intake compression device is additionally or optionally a turbocharger with a slower response time than the second intake compression device, and the adjustment involves commanding an overall pressure ratio for the first intake compression device based on the target boost pressure and adjusting the opening of a wastegate valve coupled to the turbocharger's exhaust turbine based on the commanded overall pressure ratio. In one or all of the preceding examples, the outlet pressure of the first compression device is additionally or optionally below the target boost pressure, while both the positive torque and the negative torque are commanded.In any or all of the preceding examples, the method further comprises, additionally or optionally, disabling the electric motor in response to the first compressor's outlet pressure reaching the target boost pressure. In any or all of the preceding examples, the second compressor is additionally or optionally an electric compressor, and the command involves dynamically varying a pressure ratio at the second compressor via the negative torque or the positive torque, while maintaining the pressure ratio at the second compressor below a desired pressure ratio at the first compressor.In any or all of the preceding examples, positive torque commands additionally or optionally include estimating an airflow deficiency at the first compression device in real time based on the difference between the first compression device's outlet pressure and the target boost pressure; and increasing a compressor speed of the second compression device via the positive torque as the estimated airflow deficiency increases.

[0111] Another exemplary vehicle system comprises: an engine having an intake; an accelerator pedal for receiving a torque request from a driver; a supercharging system comprising a first turbocharger compressor driven by an electric motor drawing electrical energy from a battery, and a second turbocharger compressor driven by an exhaust turbine, the second compressor being positioned downstream of the first compressor in the engine intake; a bypass comprising a bypass valve coupled to the first compressor; a wastegate comprising a wastegate actuator;which is coupled to the exhaust turbine; and a control system with computer-readable instructions stored in non-volatile memory for the following: commanding an overall pressure ratio for the second compressor based on the torque demand from the driver; if the actual pressure ratio of the second compressor is farther from the overall pressure ratio, providing positive electric motor torque to increase the pressure ratio of the first compressor; and if the actual pressure ratio of the second compressor is closer to the overall pressure ratio, providing negative electric motor torque to decrease the pressure ratio of the first compressor. In the preceding example, commanding the overall pressure ratio additionally or optionally includes reducing the wastegate actuator opening as the driver's torque demand increases.to increase the actual pressure ratio at the second compressor, wherein providing the positive electric motor torque involves operating the electric motor in a motor mode with an electric motor output based on an airflow deficiency, the airflow deficiency being estimated based on a difference between the actual pressure ratio of the second compressor and the overall pressure ratio, and wherein providing the negative torque involves operating the electric motor in a generation mode with a generator output based on the difference. In one or all of the foregoing examples, the control further includes, additionally or optionally, instructions to: close the ESBV during the provision of the positive and negative electric motor torque. In any or all of the foregoing examples, the system further includes, additionally or optionally, a first pressure sensor,a pressure sensor coupled to the inlet upstream of the first compressor to estimate air pressure; a second pressure sensor coupled to the inlet downstream of the first compressor and upstream of the second compressor to estimate turbocharger inlet pressure; a third pressure sensor coupled to the inlet downstream of the second compressor to estimate throttle inlet pressure; and wherein the control further includes instructions for: estimating the overall pressure ratio based on an output from the third pressure sensor relative to the output from the first pressure sensor; estimating the actual pressure ratio at the second compressor based on an output from the third pressure sensor relative to the output from the second pressure sensor; and estimating the actual pressure ratio of the first compressor based on an output from the second pressure sensor relative to the output from the first pressure sensor.

[0112] In another representation, the control may further include instructions for: estimating the actual pressure ratio of the first compressor based on an output from the second pressure sensor relative to the output of the first pressure sensor; estimating the actual pressure ratio at the second compressor based on the output of the third pressure sensor relative to the output of the second pressure sensor; and estimating the overall pressure ratio of the engine inlet based on the output of the third pressure sensor relative to the output of the first pressure sensor.

[0113] In another further embodiment, a method for a turbocharged engine system involves routing a total pressure ratio command to a turbocharger; and dynamically adjusting the assignment of part of the total pressure ratio command to the compressor based on an airflow deficiency at the turbocharger compressor, the airflow deficiency being based on the turbine speed. In the preceding example, routing a total pressure ratio command to the turbocharger additionally or optionally includes wastegate adjustment. In any or all of the preceding examples, the airflow deficiency is additionally or optionally estimated based on an actual pressure ratio at the turbocharger relative to the total pressure ratio command, the actual pressure ratio being derived from the turbine speed.

[0114] It should be noted that the exemplary control and estimation routines contained herein can be used with various engine and / or vehicle system configurations. The control procedures and routines disclosed herein can be stored as executable instructions in non-volatile memory and can be executed by the control system, which includes the control unit in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Accordingly, various illustrated actions, operations, and / or functions can be performed in the illustrated sequence or in parallel, or in some cases, omitted.Likewise, the processing sequence is not strictly necessary to achieve the features and benefits of the embodiments described herein, but is provided for easier illustration and description. One or more of the illustrated actions, operations, and / or functions can be performed repeatedly, depending on the specific strategy employed. Furthermore, the described actions, operations, and / or functions can graphically represent code to be programmed in the non-volatile memory of the computer-readable storage medium within the engine control system, with the described actions being performed by executing the instructions in a system that includes the various engine hardware components in combination with the electronic control unit.

[0115] It is understood that the interpretations and routines disclosed herein are exemplary in nature and that these specific embodiments are not to be interpreted in a restrictive sense, as numerous variations are possible. For example, the foregoing technology can be applied to V-6, I-4, I-6, V-12, 4-cylinder boxer, and other engine types. The subject matter of this disclosure includes all new and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and / or properties disclosed herein.

[0116] The following claims describe, in particular, certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one" element or "a first" element, or the equivalent thereof. Such claims are to be understood as including one or more such elements, without requiring or excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new claims in this or a related application.Such patent claims, regardless of whether they have a broader, narrower, the same or a different scope of protection compared to the original patent claims, are also considered to be included in the subject matter of the present disclosure.

Claims

[1] Procedure, encompassing: Operating a first compression device of an engine intake based on the torque requirement of the driver; and during the operation of the first compaction device: Operating an electric motor in an electric motor mode to provide positive electric motor torque to a second compression device while an airflow deficiency at the first compression device is higher than a threshold, and Operating the electric motor in generator mode to provide negative electric motor torque to the second compression device while the airflow deficiency at the first compression device is less than the threshold; and Disconnecting the second compression device, bypassing the second compression device by opening a bypass valve of the second compression device, and providing compressed air only via the first compression device if there is essentially no lack of airflow at the first compression device. [2] Method according to claim 1, wherein providing positive electric motor torque to the second compression device includes accelerating the second compression device and increasing a pressure ratio at the second compression device, and wherein providing negative electric motor torque to the second compression device includes decelerating the second compression device and decreasing the pressure ratio at the second compression device. [3] Method according to claim 1, wherein the threshold is based on an overall pressure ratio commanded to the first compression device, and wherein the airflow deficiency occurs when a throttle inlet pressure is less than a target boost pressure, the target boost pressure being determined on the basis of the driver's torque requirement. [4] Method according to claim 3, wherein the first compression device is a turbocharger, the second compression device is an electric compressor, and wherein the first compression device is stepped downstream of the second compression device in the engine inlet. [5] Method according to claim 4, wherein commands of the overall pressure ratio for the first compression device include adjusting an opening of an exhaust wastegate valve coupled to the exhaust turbine of the turbocharger. [6] Method according to claim 5, wherein the airflow deficiency is estimated in real time on the basis of an actual pressure ratio at the first compression device relative to the commanded total pressure ratio, wherein the actual pressure ratio at the turbocharger changes when the exhaust turbine starts up. [7] Vehicle system, comprising: an engine that has an inlet; an accelerator pedal for receiving a torque request from a driver; a charging system comprising a first turbocharger compressor driven by an exhaust turbine, wherein the first turbocharger compressor is positioned downstream of a second turbocharger compressor in the engine inlet, wherein the second turbocharger compressor is driven by an electric motor which receives electrical energy from a battery; a bypass which includes a bypass valve coupled to the second compressor; a wastegate that includes a wastegate actuator coupled to the exhaust turbine; and a controller with computer-readable instructions stored in non-volatile memory for: Commands of an overall pressure ratio for the first compressor based on the torque requirement from the driver; Adjusting the timing of the electrical intervention provided to the second turbocharger compressor, wherein the adjustment of the timing includes, If the actual pressure ratio of the first turbocharger compressor is farther away from the overall pressure ratio, provide positive electric motor torque to increase the pressure ratio of the second turbocharger compressor; and If the actual pressure ratio of the first turbocharger compressor is closer to the overall pressure ratio, but not yet reaching it, provide negative electric motor torque to reduce the pressure ratio of the second turbocharger compressor; and When the actual pressure ratio of the first turbocharger compressor reaches the total pressure ratio, the second turbocharger compressor is deactivated and the bypass valve is opened to bypass the second turbocharger compressor, while compressed air continues to be supplied via the first turbocharger compressor, based on the torque demand of the driver. [8] System according to claim 7, wherein commanding the overall pressure ratio includes reducing the opening of a wastegate actuator when the driver's torque demand increases in order to increase the actual pressure ratio at the first turbocharger compressor, wherein providing the positive electric motor torque includes operating the electric motor in a motor mode with an electric motor output based on an airflow deficiency, wherein the airflow deficiency is estimated based on a difference between the actual pressure ratio of the first turbocharger compressor and the overall pressure ratio, and wherein providing the negative torque includes operating the electric motor in a generation mode with a generator output based on the difference. [9] System according to claim 8, wherein the control further includes instructions for the following: Closing the bypass valve during the provision of positive and negative electric motor torque. [10] System according to claim 8, further comprising: a first pressure sensor coupled to the inlet upstream of the second turbocharger compressor to estimate air pressure; a second pressure sensor coupled to the inlet upstream of the first turbocharger compressor and downstream of the second turbocharger compressor, for estimating the turbocharger inlet pressure; and a third pressure sensor coupled to the inlet downstream of the first turbocharger compressor for estimating a throttle inlet pressure; and wherein the control further includes instructions for the following: Estimating the overall pressure ratio based on an output from the third pressure sensor relative to an output from the first pressure sensor; Estimating the actual pressure ratio at the second turbocharger compressor based on an output from the third pressure sensor relative to the output of the second pressure sensor; and Estimating the actual pressure ratio of the first turbocharger compressor based on an output from the second pressure sensor relative to the output of the first pressure sensor. [11] Procedure, encompassing: Adapting the operation of a first intake compression device based on a target boost pressure; and During the adjustment of the operation of the first inlet compression device: Commands of a positive torque from an electric motor to a second inlet compression device when the difference in exhaust pressure between the first inlet compression device and the target boost pressure is higher than a threshold; and Commands of negative torque from the electric motor to the second intake compression device when the difference is less than the threshold; and Deactivating the electric motor and bypassing the second inlet compression device when the outlet pressure of the first inlet compression device reaches the target boost pressure.

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