Method for operating an engine assembly

Abstract

A method of operating an engine assembly is disclosed. The engine assembly includes an engine and a turbocharger assembly, wherein a control parameter of the turbocharger assembly is controllable to control a level of boost provided by the turbocharger assembly. The method includes determining a desired pressure limit of exhaust gas upstream of a turbine of the turbocharger assembly, predicting a desired limit value of the control parameter to be applied to the turbocharger assembly to achieve the desired pressure limit, determining an error of the desired limit value of the control parameter, adjusting the desired limit value of the control parameter based on the error, and controlling operation of the turbocharger assembly such that the adjusted desired limit value is not exceeded.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to United Kingdom Patent Application No. 1800098.4, entitled "A METHOD FOR OPERATING A MOTOR VEHICLE" and filed on January 4, 2018. The entire contents of the above-listed application are incorporated herein by reference for all purposes. TECHNICAL FIELD

[0003] The present disclosure relates to methods and systems for operating an engine assembly, and more particularly, but not exclusively, to methods for operating an engine assembly in order to improve the reliability of the engine assembly. BACKGROUND

[0004] A turbocharger for an engine assembly, such as a motor vehicle, typically includes a mechanism for adjusting the level of boost being provided by the turbocharger. For example, the turbocharger can incorporate a variable geometry turbine (VGT) that incorporates a set of adjustable vanes in order to control the flow of exhaust gas through the turbine to adjust the power provided to the compressor of the turbocharger for compressing intake air. Alternatively, the turbocharger can include a bypass duct configured to allow a controllable proportion of exhaust gas to bypass the turbine.

[0005] Turbo's provided within a turbocharger are typically designed to operate up to a maximum inlet pressure and / or have a maximum pressure ratio between the inlet and outlet of the turbine. Above the maximum inlet pressure or maximum pressure ratio, the performance of the turbine is reduced. Furthermore, if the inlet pressure regularly exceeds the maximum design inlet pressure of the turbine or increases such that the maximum pressure ratio of the turbine is exceeded, the turbocharger can be damaged or require more thorough and / or more frequent maintenance.

[0006] As the turbocharger is controlled to adjust the level of boost provided, the exhaust pressure upstream of the turbine, for example within the exhaust manifold of the engine assembly, can change and can approach the maximum design pressure. For example, as the angle of the variable vanes of the VGT is adjusted and the inlet area of the VGT is reduced, the exhaust pressure upstream of the VGT can increase.

[0007] Some engine assemblies include a pressure sensor configured to measure the exhaust pressure within the exhaust manifold. The pressure measurements recorded by the pressure sensor can be used to control the operation of the turbocharger, for example within a closed feedback loop.

[0008] Exhaust manifold pressure sensors allow for accurate control of a turbocharger assembly in response to changes in exhaust manifold pressure. However, using current pressure measurements in order to determine how the turbocharger should be controlled can result in undesirably long response times between an increase in exhaust manifold pressure and a response by the vehicle's turbocharger or another system. Furthermore, since the turbocharger is controlled based on current measurements of exhaust manifold pressure, in some arrangements, once high pressure has been measured, the turbocharger is only controlled to reduce the exhaust manifold pressure below the maximum design pressure. SUMMARY

[0009] The inventors have recognized that it would be desirable to have an improved method of controlling operation of a turbocharger assembly to prevent exhaust manifold pressure from exceeding a maximum design pressure.

[0010] According to an aspect of the disclosure, there is provided a method of operating an engine assembly to overcome at least a portion of the problems mentioned above. The engine assembly includes an engine, a turbocharger assembly, and a control parameter of the turbocharger assembly is controllable in order to control a level of boost provided by the turbocharger assembly, wherein the method includes determining a desired pressure limit of exhaust upstream of a turbine of the turbocharger assembly (e.g., in an exhaust manifold or high pressure exhaust pipe), predicting a desired limit value of the control parameter to be applied to the turbocharger assembly in order to achieve the desired pressure limit, determining an error of the desired limit value of the control parameter, adjusting the desired limit value of the control parameter based on the error; and controlling operation of the turbocharger assembly such that the adjusted desired limit value is not exceeded. In this way, the turbocharger assembly can be operated to reduce the likelihood of turbocharger performance degradation and turbocharger damage. As a result, the life of the turbocharger assembly is increased, thereby reducing turbocharger maintenance, repair, etc. over the life of the engine.

[0011] It is to be understood that the above overview is provided merely for purposes of summarizing some concepts of the disclosure and that the concluding statements made herein are not necessary limiting of these concepts. The scope of the claimed subject matter is not to be determined solely from the concluding statements made in this Summary. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background or any part of the disclosure.

[0012] In order to avoid unnecessary repetition and text duplication in this specification, certain features are described with reference to only one or several aspects of the embodiments of the disclosure. However, it should be understood that the features described with reference to any aspect or embodiment of the disclosure can also be used with any other aspect or embodiment of the disclosure, if technically possible. BRIEF DESCRIPTION OF DRAWINGS

[0013] For a better understanding of the invention, and to more clearly illustrate how it can be implemented, reference will now be made to the accompanying drawings by way of example, wherein:

[0014] Figure 1 This is a schematic diagram of the engine assembly arrangement according to this disclosure;

[0015] Figure 2 This is a schematic diagram of an engine assembly arranged according to another configuration of this disclosure;

[0016] Figure 3 It is a flowchart of a method for operating engine components according to the arrangement diagram of this disclosure;

[0017] Figure 4 It is a graph of measured and modeled exhaust manifold pressures, which can be used to understand... Figure 3 The method illustrated in the diagram;

[0018] Figure 5 This is a flowchart illustrating a method for operating engine components according to another arrangement diagram of this disclosure; and

[0019] Figure 6 This is a flowchart illustrating a method for operating engine components according to another arrangement diagram of this disclosure. Detailed Implementation

[0020] According to one aspect of this disclosure, a method for operating an engine assembly is provided. The method may include determining a desired pressure limit of exhaust gas upstream of the turbine of a turbocharger assembly, and predicting desired limit values ​​of control parameters applied to the turbocharger assembly to achieve the desired pressure limit. The method may further include determining an error in the desired limit value of the control parameters, adjusting the desired limit value of the control parameters based on the error, and controlling the operation of the turbocharger assembly such that the adjusted limit value is not exceeded.

[0021] In one aspect, the error in determining the desired limit value of the control parameter may include: predicting the current value of the control parameter based on the current pressure of the exhaust gas upstream of the turbine; determining the current (e.g., measured) value of the control parameter; and determining the error between the predicted current value of the control parameter and the current value of the control parameter.

[0022] Determining the current value of, for example, a control parameter being applied to a turbocharger component can include measuring the control parameter.

[0023] Determining the current value of the control parameters can include calculating the control parameters based on the predicted current exhaust manifold pressure.

[0024] The expected limits of control parameters can be determined using data models or lookup tables, for example, based on the expected pressure limits.

[0025] The predicted current exhaust manifold pressure can be predicted using a data model or a lookup table. Using the same data model or lookup table to determine the desired limit value of the control parameter and the predicted current exhaust manifold pressure improves the accuracy with which errors can be determined.

[0026] The desired pressure limit can be determined according to one or more of: a maximum inlet pressure limit of the turbocharger assembly; a maximum pressure ratio limit between the inlet and the outlet of the turbocharger assembly; and a maximum allowable rate of increase of exhaust pressure upstream of the turbocharger turbine.

[0027] The engine assembly can further include an exhaust gas recirculation (EGR) system configured to recirculate exhaust gas from a location upstream of the turbocharger turbine to the inlet of the engine. The maximum allowable rate of increase of the exhaust manifold pressure can be determined at least in part according to an operation of the EGR system (e.g., according to a flow rate of exhaust gas being recirculated by the EGR system). For example, exhaust flow within the EGR conduit can be controlled by an EGR valve. The maximum allowable rate of increase can be determined at least in part according to a position of the EGR valve.

[0028] The method can further include varying the operation of the EGR system, e.g., by controlling the position of the EGR valve, such that the flow rate of recirculated exhaust gas remains substantially constant while the turbocharger assembly is controlled.

[0029] The operation of the turbocharger assembly can be controlled according to a minimum of: the desired value of the control parameter; and the adjusted limit value of the control parameter.

[0030] The method can further include controlling the operation of the turbocharger assembly using a closed feedback loop if the exhaust manifold pressure exceeds the desired exhaust manifold pressure limit.

[0031] The method can include detecting a request for an increase in an amount of torque supplied by the engine assembly.

[0032] For example, to control the operation of the turbocharger assembly such that the adjusted limit value is not exceeded, the method can be performed for a predetermined period of time after the request for the increase in the amount of torque is detected.

[0033] The turbocharger assembly can include a variable geometry turbine (VGT). The control parameter of the turbocharger assembly can correspond to a geometry of the VGT. For example, the control parameter can control a nozzle angle of the VGT.

[0034] The turbocharger assembly can include a turbocharger assembly bypass conduit configured to allow exhaust gases to bypass a turbine of the turbocharger assembly. Exhaust gas flow through the bypass conduit can be controlled by a bypass valve. The control parameter of the turbocharger assembly can correspond to a position of the bypass valve (e.g., between an open position and a closed position of the valve).

[0035] According to another aspect of the present disclosure, there is provided a method for operating a motor vehicle, the motor vehicle comprising a vehicle assembly, a control parameter of the vehicle assembly being controllable in order to control operation of the vehicle assembly, wherein the method comprises determining a first limit value for the control parameter based on a modeled value of a first operating parameter of the vehicle assembly using a first method; determining a second limit value for the control parameter based on a measured value of the first operating parameter using a second method; determining an authorized limit based on a second operating parameter of the engine assembly, wherein the authorized limit limits the value of the first limit value that can be used to control operation of the turbocharger assembly; and

[0036] controlling operation of the vehicle assembly based on the first limit value if the first limit value is within the authorized limit, or controlling operation of the vehicle assembly based on the more limiting one of the second limit value and the authorized limit (e.g., for operation of the vehicle assembly) if the first limit value is outside the authorized limit, e.g., such that the imposed limit value is not exceeded.

[0037] The authorized limit can be a minimum value of the control parameter that is allowed to be applied by the first method. The vehicle assembly can be a turbocharger assembly provided within an engine assembly of the motor vehicle, for example.

[0038] According to another aspect of the disclosure, there is provided a method for operating an engine assembly, the engine assembly comprising: an engine; a turbocharger assembly, a control parameter of the turbocharger assembly being controllable to control a level of boost provided by the turbocharger assembly, wherein the method comprises: determining a first limit value for the control parameter based on one of a modelled value and a measured value of an exhaust manifold pressure using a first method; determining a second limit value for the control parameter based on the other of the modelled value and the measured value of the exhaust manifold pressure using a second method; determining an authorised limit based on an operating parameter of the engine assembly, wherein the authorised limit limits a value of the first limit value that can be used to control operation of the turbocharger assembly; and controlling operation of the turbocharger assembly based on the first limit value if the first limit value is within the authorised limit, or based on the more limiting of the second limit value and the authorised limit if the first limit value is outside the authorised limit, e.g. such that the imposed limit value is not exceeded. In this way, operation of the turbocharger can be limited to the extent of the authorised limit according to the first limit value determined using the first method. The authorised limit can be a minimum value of the control parameter to which the first method is permitted to limit the control parameter.

[0039] The method can comprise determining a maximum permitted value for the control parameter based on a further operating parameter of the engine assembly. For example, the maximum permitted value can be determined based on an operating speed and / or a torque output of the engine assembly.

[0040] The authorised limit can be defined relative to the maximum permitted value. In other words, the authorised limit can limit a maximum difference between the maximum permitted value and the first limit value to which operation of the turbocharger assembly can be limited by the first method.

[0041] The first limit value can be determined using a data model or a lookup table. The second limit value can be determined using a closed feedback loop method, including proportional, integral and / or derivative control. For example, a pressure of exhaust gas at an inlet of a turbine of the turbocharger (e.g. within an exhaust manifold) can be fed back and compared to a maximum desired inlet pressure.

[0042] The first limit value and the second limit value can be determined using separate controllers or modules. For example, the closed feedback loop method can be performed using a closed loop feedback controller or module.

[0043] The authorised limit can be determined based on one or more of: an engine torque, e.g. a rate of change of engine torque; a driver requested engine torque; an exhaust pressure at an inlet of a turbine of the turbocharger; a maximum exhaust pressure at the inlet of the turbine; a turbocharger boost level; a flow rate of exhaust gas through the turbine; and a maximum permitted value of the control parameter.

[0044] The authorization limit can be determined based on a rate of change of engine torque requested by the driver.

[0045] The first method can be the method of operating an engine assembly mentioned above.

[0046] According to another aspect of the disclosure, there is provided software which, when executed by a computing device, causes the computing device to perform any one of the methods mentioned above.

[0047] According to another aspect of the disclosure, there is provided an engine assembly for a motor vehicle, the engine assembly comprising: an engine; a turbocharger assembly, a control parameter of the turbocharger assembly being controllable so as to control a level of boost provided by the turbocharger assembly; and one or more controllers configured to perform any one of the methods mentioned above.

[0048] The engine assembly can further comprise an exhaust gas recirculation (EGR) system configured to recirculate exhaust gas from a location upstream of a turbine of the turbocharger assembly to an intake of the engine.

[0049] The motor vehicle can comprise the engine assembly mentioned above.

[0050] In order to avoid unnecessary repetition work and repetition of text in this specification, certain features are described with reference to only one or several aspects or embodiments of the invention. However, it should be understood that features described with reference to any aspect or embodiment of the invention can also be used together with any other aspect or embodiment of the invention, if technically possible.

[0051] Reference is made to Figure 1 , an engine assembly 2 for a vehicle 50 (e.g. a motor vehicle) comprises an engine 4, an intake system 6, an exhaust system 8, a high pressure (HP) exhaust gas recirculation (EGR) system 10 and a turbocharger assembly 14.

[0052] As depicted in Figure 1 , the intake system 6 comprises a low pressure (LP) intake duct 6a provided upstream of a compressor 14a of the turbocharger assembly. The compressor 14a is configured to increase a pressure of intake air arriving at an intake of the compressor 14a from the low pressure intake duct 6a to a level of boost pressure. The intake air that has been compressed by the compressor 14a enters a high pressure intake duct 6b. The intake air flows within the HP intake duct 6b to an intake manifold 4a of the engine and can be drawn into cylinders 5 of the engine 4.

[0053] Intake air is mixed with fuel within the cylinders 5 of the engine 4, and the fuel is combusted to provide power to drive the engine 4. Exhaust gas produced by this combustion is expelled from the engine 4 into the high pressure exhaust conduit 9b via the exhaust manifold 4b. The exhaust gas can flow through the HP exhaust conduit 9b to the turbine 14b of the turbocharger assembly 14. The exhaust gas can be expanded through the turbine 14b to reach the low pressure exhaust conduit 9a. The turbine 14b can be coupled to the compressor 14a via a shaft. By expanding the exhaust gas through the turbine, power can be generated by the turbine 14b to power the compressor 14a.

[0054] In Figure 1 the arrangement shown in the turbine 14b is a variable geometry turbine (VGT) comprising variable inlet vanes 60 arranged at an angle relative to a rotor 62 of the turbine. By varying the angle of the inlet vanes relative to the rotor, the power generated by the turbine 14b, and hence the power provided to the compressor 14a, can be controlled. The level of boost provided by the turbocharger assembly 14 can therefore be controlled by varying the angle of the variable inlet vanes. The engine assembly 2 can comprise a controller 100 for controlling the operation of the VGT, for example by controlling the position of the vanes of the VGT.

[0055] Figure 2 In some arrangements, the geometry of the turbine 14b can be fixed, and the level of boost provided by the turbocharger assembly 14 can be controlled by alternative means. For example, as shown in the turbocharger assembly 14 can comprise a bypass conduit 14c configured to allow a portion of the exhaust gas to flow from the HP exhaust conduit 9b to the LP exhaust conduit 9a without passing through the turbine 14b. The flow of exhaust gas through the bypass conduit 14c can be controlled by a bypass valve 14d, such as a wastegate. By allowing a portion of the exhaust gas to bypass the turbine 14b, the power generated by the turbine 14b, and hence available to drive the compressor 14a, can be reduced. The level of boost provided by the turbocharger assembly 14 can therefore be reduced.

[0056] Figure 2 In the arrangement shown in

[0057] In other arrangements, the exhaust system 8 can comprise the VGT 14b, and can also comprise the bypass conduit 14c and the bypass valve 14d. In such arrangements, the power generated by the turbine 14b can be controlled by varying the geometry of the turbine 14b and / or by varying the position of the bypass valve 14d.

[0058] Increasing the pressure (e.g., boost level) of the intake air entering the engine 4 allows a greater amount of air to be drawn into the cylinders of the engine, which in turn allows more fuel to be mixed with the air and combusted. Combusting more fuel within the engine 4 allows the engine to produce more power and torque to drive the vehicle. When the driver of the vehicle requests more power to be supplied by the engine 4, such as by pressing on the accelerator pedal 162 of the vehicle, the turbocharger assembly 14 can be controlled to increase the boost level provided by the turbocharger assembly and thus increase the power and torque produced by the engine.

[0059] The engine assembly 2 can further include a low pressure (LP) EGR assembly 16 including an LP EGR conduit 16a configured to recirculate a portion of the low pressure exhaust gas back to the intake system 6 (e.g., to the low pressure intake conduit 6a). The flow of exhaust gas within the LP EGR conduit 16a can be controlled by an LP EGR valve 16b.

[0060] The exhaust system 8 can further include one or more exhaust aftertreatment devices 18 provided downstream of the turbine 14b. For example, the exhaust system 8 can include a lean NOx trap 18, a particulate filter 18, and / or a selective catalytic reduction device 18. The exhaust aftertreatment devices can be configured to reduce the concentration of polluting substances present within the exhaust gas.

[0061] One or more of the exhaust aftertreatment devices 18 can be controllable, for example, to adjust their efficiency of removing polluting substances from the exhaust gas. Controlling the operation of the exhaust aftertreatment devices can affect the mass flow rate of the exhaust gas through the exhaust system 8 and thus through the turbine 14b.

[0062] Referring to Figure 1 and Figure 2 The HP EGR system 10 includes an EGR conduit 12 configured to recirculate a portion of the exhaust gas away from the engine 4 back to the intake system 6. The recirculated exhaust gas is mixed with the intake air within the intake system 6 and can be drawn back into the engine 4. A first end 12a of the HP EGR conduit can be coupled to and in fluid communication with the HP exhaust conduit 9b, for example, at a location on the exhaust system 8 upstream of the turbine 14b. For example, the first end 12a of the HP EGR conduit can be coupled to the exhaust manifold 4b. A second end 12b of the HP EGR conduit can be coupled to and in fluid communication with the HP intake conduit 6b, for example, at a location on the intake system 6 between the compressor 14a and the engine 4.

[0063] The flow of exhaust gas within the HP EGR conduit 12 can be controlled by the HP EGR valve 10a. The flow rate of the exhaust gas can depend on the position of the HP EGR valve 10a and the pressure difference between the first end 12a and the second end 12b of the HP EGR conduit 12. For example, in the arrangement shown in Figure 1 and Figure 2 for a given position of the HP EGR valve 10a, the flow rate of the exhaust gas within the HP EGR conduit 12 can increase as the pressure of the exhaust gas within the HP exhaust conduit 9b increases relative to the pressure of the intake air within the HP inlet conduit 6b.

[0064] An increased flow rate of EGR gas due to a change in the position of the HP EGR valve or a change in the pressure difference across the HP EGR conduit 12 can result in a reduced amount of intake air present within the intake air being drawn into the cylinders of the engine 4, thereby reducing the amount of fuel that can be combusted within the engine. The power produced by the engine 4 can therefore be reduced. Controlling the power produced by the engine in this way can be beneficial as it can result in a reduction in the production of pollutants, such as nitrogen oxides, compared to controlling the engine 4 in other ways, for example by using an intake throttle.

[0065] As described above, when the driver of the vehicle requests an increase in power or torque, the operation of the turbocharger assembly 14 can be controlled to increase the level of boost provided. In the arrangement depicted in Figure 1 controlling the turbocharger assembly to increase the level of boost can be achieved by adjusting the angle of the variable vanes of the turbine 14b.

[0066] Adjusting the angle of the vanes can reduce the area through which exhaust gas passing through the turbine 14b can flow. Therefore, after controlling the turbine in this way, the pressure of the exhaust gas upstream of the turbine, for example within the exhaust manifold 4b, can increase.

[0067] The controller 100 can be configured to control the operation of the turbocharger assembly 14 in response to a request for an increase in power or torque. The controller 100 can be configured to control the operation of the turbocharger assembly 14 in response to a request for an increase in power or torque. Figure 1The controller 100 is configured to receive various signals from sensors coupled to the engine 4 and send command signals to actuators in components in the vehicle, such as the throttle (not shown). In addition, the controller 100 is also configured to receive a pedal position (PP) from a pedal position sensor 160 coupled to a pedal 162 actuated by an operator 164. Thus, in one example, the controller 100 can receive a pedal position signal and adjust an actuator in the throttle to change the engine speed based on the pedal position signal. It should be appreciated that other components that receive command signals from the controller can operate in a similar manner. It should also be appreciated that in some examples, Figure 2 The controller 100 in Figure 1 may also include components described above and included in the controller 100 shown in It should also be appreciated that the controller 100 can be configured to implement one or more of the methods, control strategies, etc. described herein.

[0068] Figure 2 Similarly, in the arrangement shown in , the control turbocharger assembly to increase the boost level can be achieved by closing the wastegate 14d. Closing the wastegate can reduce the flow area available for exhaust gas to bypass the turbine 14b, which can result in an increase in the pressure of the exhaust gas within the HP exhaust conduit 9b and / or the exhaust manifold 4b.

[0069] In some arrangements, when the engine assembly 2 requires a high torque level and the turbocharger assembly 14 is controlled to provide an increased boost level in response to the torque requirement, the pressure of the exhaust gas at the inlet of the turbine 14b (e.g., within the exhaust manifold 4b and / or the high pressure exhaust conduit 9b) of the turbocharger assembly can approach the maximum design pressure of the turbine 14b. Additionally or alternatively, the pressure ratio between the inlet and the outlet of the turbine 14b can approach the maximum design ratio. As described above, if the maximum design pressure of the turbine 14b or the maximum design pressure is exceeded, the performance of the turbine can be reduced, the turbocharger can be damaged, and / or the turbocharger can require more thorough and / or more frequent maintenance.

[0070] Referring to Figure 3 , to reduce the risk of the pressure of the exhaust gas at the turbine inlet exceeding the maximum design pressure or the pressure ratio between the inlet and the outlet of the turbine exceeding the maximum design ratio, the turbocharger assembly can be controlled, e.g., by the controller 100, in accordance with the method 300.

[0071] The method 300 includes a first step 302 in which a desired exhaust pressure limit P3 of the exhaust gas at the inlet of the turbine is determinedmax The desired exhaust pressure limit can be determined based on at least one of a maximum design pressure, a maximum design ratio, and one or more other pressure limits (e.g., dynamic pressure limits based on the operating conditions of the engine components).

[0072] In a second step 304 of the method 300, a desired limit value VGT max The control parameter can correspond to any desired control parameter of the turbocharger that can be applied to control the operation of the turbocharger in order to affect the pressure of the exhaust gas at the inlet of the turbine 14b. For example, the control parameter can correspond to the angle of the variable vanes of the VGT 14b or the position of the turbocharger bypass valve 14d.

[0073] In Figure 4 , the line LI is a curve of actual exhaust manifold pressure on a vertical axis versus variable vane position on a horizontal axis, and the line L2 is a curve of modeled exhaust manifold pressure on a vertical axis versus variable vane position on a horizontal axis determined from a data model relating VGT position to exhaust manifold pressure.

[0074] The desired limit value VGT max may be determined by referencing a data model or lookup table. For example, as depicted in Figure 4 , the desired limit value VGT max is determined by using the desired exhaust pressure limit P3 max as input to a model relating VGT position to exhaust manifold pressure.

[0075] In a third step 306 of the method 300 shown in Figure 3 , an error AVGT lim is determined.

[0076] As shown in Figure 4 and with reference to Equation 1 below, the error AVGT lim may be determined by comparing a measured value VGT1 of the current control parameter (e.g., measured using a vane angle sensor and / or a bypass valve position sensor of the turbocharger assembly) to a predicted current value VGT2 of the control parameter. The predicted current value VGT2 of the control parameter can be determined using the exhaust pressure value P3 measured (measured using an exhaust manifold pressure sensor) as input to a model relating VGT position to exhaust manifold pressure.

[0077] AVGT lim = gain * (VGT2 - VGT1) (1)

[0078] Alternatively, the error AVGT lim may be determined by comparing the estimated value VGT3 of the control parameter with a predicted current value of the control parameter. As illustrated in Figure 4 , the estimated value VGT3 of the control parameter is calculated by using a modelled value P3 modelled of the exhaust gas pressure as an input to a model relating VGT position to exhaust manifold pressure. As depicted in Figure 4 , using the estimated value VGT3 of the control parameter results in calculating substantially the same error value AVGT lim .

[0079] As depicted in equation (1), in some arrangements, the error AVGT lim may be multiplied by a gain value. The gain can be a constant value applied at all operating conditions of the engine assembly 2. Alternatively, the gain value can be adjusted in dependence on current operating parameters of the turbocharger assembly 14 or the engine assembly 2. For example, the gain value can be determined in dependence on the current exhaust gas pressure at the turbine inlet.

[0080] In a fourth step 308 of the method 300 shown in Figure 3 , a desired limit value VGT max of the control parameter is adjusted based on the error AVGT lim , for example by adding / subtracting the error from / to the desired limit value to determine an adjusted limit value, see equation (2) below.

[0081] VGT corrected = VGT max - AVGT lim (2)

[0082] In a fifth step 310 of the method 300, the operation of the turbocharger assembly 14 is controlled such that the adjusted limit value VGT corrected is not exceeded. For example, the turbocharger assembly can be controlled using the adjusted desired limit value VGT corrected and the minimum of the desired value of the control parameter determined by the controller, for example, to provide a desired turbocharger boost level.

[0083] By controlling the turbocharger assembly 14 based on the modelled value of the exhaust gas pressure, the response time of the control can be shorter than a method which relies on measurements from a pressure sensor to establish whether a pressure limit has been reached. Furthermore, by controlling the turbocharger assembly 14 based on the modelled value of the exhaust gas pressure, for example when the model determines that the value of the control parameter can result in the pressure limit being exceeded, the control of the turbocharger assembly can be adjusted to prevent the pressure limit being exceeded before it is reached.

[0084] The method 300 can further include controlling operation of the turbocharger using a closed feedback loop, for example, where the pressure of the exhaust gas upstream of the turbine is fed back to the controller 100 or another controller, such as a closed loop feedback controller, if the pressure of the exhaust gas upstream of the turbine exceeds a desired pressure limit. The pressure sensor and feedback controller can thereby be used as a fall back in the event that the predicted values or models used within the method 300 are inaccurate.

[0085] In some arrangements, the method 300 can include detecting a request to increase the amount of torque supplied by the engine assembly. For example, if the driver of the vehicle presses the accelerator pedal of the vehicle.

[0086] When a request to increase the amount of torque is detected, the steps of the method 300 described above can be performed in order to control operation of the turbocharger assembly 14 so that the desired exhaust pressure limit is not exceeded. The method can be performed for a predetermined period of time after the request is detected in order to control operation of the turbocharger assembly 14.

[0087] Prior to the request being detected, operation of the turbocharger assembly can be controlled using the previously proposed methods (e.g. using a closed loop feedback controller that takes into account pressure measurements of the exhaust gas upstream of the turbine). After the predetermined period of time, the turbocharger assembly can return to being controlled using the previously proposed methods. Alternatively, for example, the method 300 can be repeatedly performed regardless of the torque requirements.

[0088] The increase in the pressure of the exhaust gas upstream of the turbine 14b due to the change in operation of the turbocharger assembly can occur at a higher rate than the increase in the pressure of the intake air within the HP intake duct 6b due to an increase in the power supplied to the compressor 14a (e.g. by the turbine 14b). This can result in a change in the pressure difference between the first end 12a and the second end 12b of the HP EGR duct 12, which in turn can affect (e.g. increase) the flow rate of the EGR gas within the HP EGR duct.

[0089] Accordingly, when a driver requests an increase in the power supplied by the engine, the interaction between the operation of the turbocharger assembly 14 and the HP EGR system 10 due to the increased rate of EGR can result in an undesirable decrease in the power provided by the engine 4.

[0090] The position of the HP EGR valve 10a can be controlled based at least in part on the pressure difference across the HP EGR duct 12, and therefore the HP EGR valve 10a can be controlled to compensate for this effect. However, if the driver requests a rapid increase in the power supplied by the engine, the HP EGR valve 10a can not be controlled quickly enough to sufficiently compensate for the change in the pressure difference across the HP EGR duct 12.

[0091] Referring to Figure 5 In order to prevent an undesired reduction in engine power, a method 500 of operating an engine assembly arrangement according to the present disclosure can be performed.

[0092] The method comprises a first step 502 in which a pressure of exhaust gas upstream of the turbine 14b (e.g. within the HP exhaust conduit 9b or exhaust manifold 4b) is determined. In a second step 504, the operation of the turbocharger assembly can be controlled at least partly in dependence on the determined pressure.

[0093] Changes in the pressure differential across the HP EGR conduit 12 that can be caused by changes in the operation of the turbocharger assembly 14 can be dependent on the pressure of exhaust gas upstream of the turbine 12b (e.g. within the exhaust manifold 4b of the engine). Thus, by controlling the operation of the turbocharger assembly 14 at least partly in dependence on the exhaust manifold pressure, an undesired reduction in power provided by the engine can be avoided.

[0094] The pressure of exhaust gas upstream of the turbine 14b can be determined using a pressure sensor provided on the HP exhaust conduit 9b and / or exhaust manifold 4b. Alternatively, the pressure of exhaust gas upstream of the turbine 14b can be determined using a data model or look-up table.

[0095] In one arrangement of the present disclosure, the data model used allows the pressure of exhaust gas upstream of the turbine 14b to be determined based on a combination of the geometry of the VGT 14b and / or the position of the bypass valve 14d, the mass flow rate of exhaust gas through the turbine 14b, and the pressure downstream of the turbine. However, in other arrangements it is envisaged that a data model or look-up table can be applied that allows the pressure of exhaust gas upstream of the turbine 14b to be determined based on a combination of the geometry of the VGT 14b and / or the position of the bypass valve 14d, the mass flow rate through the turbine, the pressure downstream of the turbine, the operating speed of the engine, the position of the HP EGR valve 10b, the position of the LP EGR valve 16b, and / or any other suitable parameter of the engine assembly 2.

[0096] In some examples, the method 500 can further comprise determining a maximum allowable rate of increase of the pressure of exhaust gas upstream of the turbine. The operation of the turbocharger can be controlled such that the rate of increase of the pressure of exhaust gas upstream of the turbine is maintained at or below the maximum allowable rate.

[0097] The maximum allowable rate of increase of the pressure can be determined such that the HP EGR system 10 is able to be controlled to sufficiently compensate for changes in the pressure differential across the HP EGR conduit 12. For example, by changing the position of the HP EGR valve 10a to maintain the flow rate of recirculated exhaust gas within the HP EGR conduit 12 at a desired level.

[0098] Operation of the turbocharger assembly 14 can be controlled such that the pressure of the exhaust gas upstream of the turbine 12b is maintained at or below a maximum allowable value. For example, a maximum allowable rate of pressure increase can be used in the first step of the method 300 to determine a desired exhaust gas pressure limit for controlling operation of the turbocharger assembly within the method 300.

[0099] In some arrangements, a nominal maximum value of a control parameter (e.g., an angle of vanes of the VGT 14a or a setting of the turbocharger wastegate 14d) applied to control operation of the turbocharger assembly 14 can be determined based on a function of one or more operating parameters of the engine assembly. For example, the nominal maximum value of the control parameter can be determined based on a speed and / or power of the engine assembly.

[0100] The adjusted desired limit value determined, for example, in the fourth step 308 of the method 300 can be applied to override the nominal maximum value (e.g., impose a more restrictive setting on the turbocharger assembly 14) to the extent that can be determined based on one or more operating parameters of the engine assembly, such as torque, requested torque, and / or exhaust manifold pressure.

[0101] In this way, in some desired situations, for example, where there is a high torque request, or the exhaust manifold pressure is greater than a limit pressure (e.g., the desired exhaust pressure limit), the adjusted desired limit value determined using the method 300 can be used to control the turbocharger assembly 14. In other situations, it can be determined that the adjusted desired limit value can be overly restrictive, and another control parameter calculated using another method and / or by a different controller, such as a closed loop feedback controller, can be applied to control the turbocharger assembly 14.

[0102] Referring to Figure 6 According to some arrangements of the present disclosure, operation of the turbocharger turbine 14b and / or the turbocharger wastegate 14d is controlled using the method 600, in which a selection is made from a plurality of control parameters and control parameter limits to control operation of the turbocharger assembly 14.

[0103] In a first step 602 of the method 600, an adjusted desired limit value of a control parameter is determined, for example, using the method 300 described above.

[0104] In a second step 604, an authorized limit for the adjusted desired limit value is determined. The authorized limit can be determined based on a function of one or more operating parameters of the engine assembly. For example, the authorized limit can be determined based on a function of an engine torque request (e.g., a rate of change of torque over time) and a difference between the exhaust pressure and a maximum design pressure.

[0105] The authorized limit can be defined as a minimum value of the control parameter that can be applied by the method 300 as a limit value on the control of the turbocharger assembly 14. In other words, the authorized limit can be a minimum value of the adjusted desired limit value VGT corrected that can be applied by the method 300 to control the operation of the turbocharger assembly. Alternatively, the authorized limit can be defined as a maximum allowable difference between the nominal maximum value of the control parameter and the adjusted desired limit value.

[0106] In a third step 606, a trimmed limit value of the control parameter is calculated by comparing the adjusted desired limit value, the authorized limit, and optionally the nominal maximum value. For example, when the authorized limit defines a minimum authorized value of the control parameter, the trimmed limit value is calculated by taking the maximum of the adjusted desired limit value and the authorized limit.

[0107] In a fourth step 608, a closed loop control parameter value is determined by using a closed loop feedback controller. The closed loop control parameter value can be based on a measured value of the exhaust pressure (e.g., exhaust manifold pressure) and a maximum design pressure of the turbocharger.

[0108] In a fifth step 610, a maximum nominal value of the control parameter is determined as described above (if not already available from determining the authorized limit or the trimmed limit value).

[0109] The method 600 can include a sixth step 612 in which a further control parameter value is calculated based on one or more measured and / or modeled operating properties of the engine assembly, such as engine speed, engine load, intake and / or exhaust pressure, and / or any other operating property of the engine assembly.

[0110] In a seventh step 614 of the method 600, a final control parameter value is determined based on the control parameter values determined in the other steps of the method. For example, the final limit value can be determined as a minimum value of the trimmed limit value, the closed loop control parameter value, the maximum nominal value, and / or the further control parameter value.

[0111] The final limit value can be used to control the operation of the turbocharger assembly, for example, such that the value of the control parameter does not exceed the limit value.

[0112] Method 600 provides a way to smoothly transition between a method of controlling limits on turbocharger assembly operation, such as method 300, and a method of using closed feedback loop control, depending on which method is deemed most suitable for the current operating conditions of the engine assembly. For example, during dynamic maneuvers, method 300 can be used to reduce the risk of the turbo inlet pressure limit being exceeded, and under steady state conditions, closed loop feedback control can be used to accurately maintain the turbo inlet pressure at a desired value.

[0113] The technical effect of providing the methods for controlling turbocharger operation described herein is to reduce the likelihood of turbocharger performance degradation and turbocharger damage. As a result, the life of the turbocharger assembly is increased, thereby reducing turbocharger maintenance, repair, etc. over the useful life of the engine. The methods for operating a turbocharger assembly described herein can also reduce control delays in turbocharger operation that can lead to overpressure conditions in the turbocharger.

[0114] Those skilled in the art will recognize that the present application has been described herein with reference to one or more examples in accordance with the present application, but that the application is not limited to the examples disclosed and that alternative examples can be constructed without departing from the scope of the present application as defined by the appended claims.

[0115] It should be appreciated that the configurations disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, as numerous variations are possible. For example, the above-described techniques can be applied to V-6, I-4, I-6, V-12, opposed 4 cylinder, and other engine types. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various systems and configurations disclosed herein, as well as other features, functions, and / or properties.

[0116] The following claims particularize certain combinations and subcombinations thought to be novel and nonobvious. These claims can refer to "an" element or "a first" element or the equivalent thereof. These claims should be understood as embracing one or more such elements in their entirety, either conjunctively or disjunctively. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties can be claimed by amending present claims or by presenting new claims in this or a related application. Such appended claims, as can stand broadest claim scope, as well as narrower subcombination claims, are intended to include all such subcombinations.

Claims

1. A method of operating an engine assembly, the engine assembly comprising: Engine; and A turbocharger assembly, wherein the control parameters of the turbocharger assembly are controllable to control the boost level provided by the turbocharger assembly, and wherein the method comprises: Determine the desired pressure limit of the exhaust gas upstream of the turbine of the turbocharger assembly; Predict the desired limit values ​​of the control parameters applied to the turbocharger assembly to achieve the desired pressure limit; The error in determining the desired limit value of the control parameter; The desired limit value of the control parameter is adjusted based on the error. as well as The operation of the turbocharger assembly is controlled so that the adjusted desired limit value is not exceeded; The error in determining the desired limit value of the control parameter includes: The current value of the control parameter is predicted based on the current pressure of the exhaust gas upstream of the turbine; Determine the current value of the control parameter; as well as Determine the error between the predicted current value of the control parameter and the current value of the control parameter.

2. The method of claim 1, wherein determining the current value of the control parameter comprises calculating the control parameter based on a predicted current exhaust manifold pressure.

3. The method of claim 1, wherein the desired pressure limit is determined according to one or more of the following: The maximum inlet pressure limit of the turbocharger assembly; The maximum pressure ratio limit between the inlet and outlet of the turbocharger assembly; and The maximum permissible rate of increase in exhaust pressure upstream of the turbine.

4. The method of claim 3, wherein the engine assembly further comprises an exhaust gas recirculation system, i.e., an EGR system, the exhaust gas recirculation system being configured to recirculate exhaust gas from a location upstream of the turbine of the turbocharger assembly to the inlet of the engine, wherein the maximum permissible rate of increase in the pressure of the exhaust gas upstream of the turbine is determined at least in part based on the operation of the EGR system.

5. The method of claim 4, wherein the method further comprises: The operation of the EGR system is altered so that the flow rate of the recirculated exhaust gas remains substantially constant when the turbocharger assembly is controlled.

6. The method of claim 1, wherein the method further comprises controlling the operation of the turbocharger assembly using a closed feedback loop if the pressure of the exhaust gas upstream of the turbine exceeds the desired pressure limit of the exhaust gas upstream of the turbine.

7. The method of claim 1, further comprising detecting a request for an increase in the amount of torque supplied by the engine assembly.

8. The method of claim 7, wherein the method is performed within a predetermined time period after the request for an increase in torque is detected.

9. The method of claim 1, wherein the turbocharger assembly includes a variable geometry turbine, or VGT, and wherein the control parameters of the turbocharger assembly correspond to the geometry of the VGT.

10. The method of claim 1, wherein the turbocharger assembly includes a turbocharger assembly bypass passage configured to allow exhaust gas to bypass the turbine of the turbocharger assembly, wherein the exhaust gas flow through the bypass passage is controlled by a bypass valve; and wherein the control parameters of the turbocharger assembly correspond to the position of the bypass valve.

11. The method of claim 1, wherein the method is executed by software, and when the computing device executes the software, the software causes the computing device to execute the method.

12. An engine assembly comprising: engine; A turbocharger assembly, wherein the control parameters of the turbocharger assembly are controllable in order to control the boost level provided by the turbocharger assembly; as well as One or more controllers, which are configured to; Determine the desired pressure limit of the exhaust gas upstream of the turbine of the turbocharger assembly; Predict the desired limit values ​​of the control parameters applied to the turbocharger assembly to achieve the desired pressure limit; The error in determining the desired limit value of the control parameter; The desired limit value of the control parameter is adjusted based on the error. as well as The operation of the turbocharger assembly is controlled so that the adjusted desired limit value is not exceeded; The error in determining the desired limit value of the control parameter includes: The current value of the control parameter is predicted based on the current pressure of the exhaust gas upstream of the turbine; Determine the current value of the control parameter; as well as Determine the error between the predicted current value of the control parameter and the current value of the control parameter.

13. The engine assembly of claim 12, wherein the engine assembly is included in a motor vehicle.

14. A method of operating an engine assembly, the engine assembly comprising: Engine; and A turbocharger assembly, wherein the control parameters of the turbocharger assembly are controllable to control the boost level provided by the turbocharger assembly, wherein the method comprises: Determine the desired pressure limit of the exhaust gas upstream of the turbine of the turbocharger assembly; Predict the desired limit values ​​of the control parameters applied to the turbocharger assembly to achieve the desired pressure limit; The error in determining the desired limit value of the control parameter; The desired limit value of the control parameter is adjusted based on the error. as well as The operation of the turbocharger assembly is controlled so that the adjusted limit value is not exceeded; The operation of the turbocharger assembly is controlled according to the minimum of the following: The expected value of the control parameter; and The adjusted desired limit value of the control parameter; The error in determining the desired limit value of the control parameter includes: The current value of the control parameter is predicted based on the current pressure of the exhaust gas upstream of the turbine; Determine the current value of the control parameter; as well as Determine the error between the predicted current value of the control parameter and the current value of the control parameter.

15. The method of claim 14, further comprising detecting a request for an increase in the amount of torque supplied by the engine assembly; The method is executed within a predetermined time period after the request for an increase in torque is detected.

16. The method of claim 14, wherein determining the current value of the control parameter comprises calculating the control parameter based on a predicted current exhaust manifold pressure.

17. The method of claim 14, wherein the method further comprises controlling the operation of the turbocharger assembly using a closed feedback loop if the pressure of the exhaust gas upstream of the turbine exceeds the desired pressure limit of the exhaust gas upstream of the turbine.

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