SYSTEM FOR CONTROLLING THE TURBOCHARGER SHAFT SPEED OF AN INTERNAL ENGINE

Abstract

A turbocharger shaft speed control system for an internal combustion engine (ICE) includes sensors, actuators, and control modules that communicate with the sensors and actuators. The control modules store and execute control logic that generates a predicted shaft speed from the turbocharger shaft speed data. A shaft speed control algorithm (SSCA) is selectively initialized. The SSCA generates lower and upper limits for turbocharger flow corrections, which are applied via the actuators. The control outputs are selectively applied to the actuators to control mass flow through a turbocharger compressor. The SSCA selectively determines that the shaft speed has exceeded a threshold, at which point the actuators modify an ICE pressure ratio.The SSCA operates the turbocharger stably within predefined hardware limits at an optimal shaft speed, while maintaining a constant flow rate across a range of pressure conditions. A long-term memory learning process fine-tunes the turbocharger performance.

Description

INTRODUCTION

[0001] The present disclosure relates to internal combustion engines (ICEs), and more particularly to ICEs equipped with one or more boosting devices, such as turbochargers. ICEs are often equipped with boosting devices to increase ICE power density while reducing ICE mass and overall displacement and increasing efficiency. Turbocharged ICEs often utilize manual and / or electronic boost control systems and methods to achieve and maintain various performance metrics.To maximize power output for a given turbocharged ICE, the engine control unit (ECU) and boost control systems and methods may operate the one or more turbochargers of a turbocharged ICE at or very close to the physical limits of the turbocharger, which may result in thermal inefficiencies, performance degradation, premature component failure, or the like.

[0002] While current turbocharging systems and their associated methods for managing turbocharger boost pressure work for their intended purpose, there is a need for a new and improved system and method for controlling ICE turbocharger shaft speed that improves redundancy, increases ICE performance and turbocharger power, and quickly and accurately limits turbocharger output within specified margins while utilizing pre-existing assemblies and reducing complexity.

[0003] The document EP 2 434 122 A1 discloses a method for controlling an internal combustion engine in which a mass flow through a compressor is controlled. SUMMARY

[0004] According to one aspect of the present disclosure, a system for controlling turbocharger shaft speed for an internal combustion engine (ICE) includes a boost control system having one or more sensors and one or more actuators. The one or more sensors detect at least one turbocharger shaft speed and a mass flow rate through the ICE, and the one or more actuators selectively adjust the mass flow rate through the ICE and the turbocharger. The system further includes one or more control modules. Each of the one or more control modules includes a processor, memory, and one or more input / output (I / O) ports. The one or more control modules communicate with the one or more sensors and communicate with the one or more actuators via the I / O ports. The memory stores program control logic. The processor executes the program control logic.The program control logic includes at least first, second, third, fourth, fifth, and sixth control logic. The first control logic generates a predicted turbocharger shaft speed from data acquired by a turbocharger shaft speed (TSS) sensor of the one or more sensors. The second control logic selectively initializes a turbocharger shaft speed control algorithm (turbocharger SSCA). The third control logic within the SSCA generates a lower limit and an upper limit, greater than the lower limit, for an amount of turbocharger flow correction to be applied via the one or more actuators. The fourth control logic within the SSCA applies a closed-loop control output to the one or more actuators to control a mass flow rate through a compressor of the turbocharger.The fifth control logic within the SSCA selectively determines that the turbocharger shaft speed has exceeded a predetermined threshold and applies the one or more actuators to directly change a pressure ratio of the ICE. The sixth control logic within the SSCA uses a long-term memory learning process that uses the data from the one or more sensors and the one or more actuators as inputs to fine-tune turbocharger performance. The SSCA causes the turbocharger to operate stably within predetermined hardware limits at an optimal shaft speed while maintaining a constant flow across a range of pressure ratios.

[0005] According to another aspect of the present disclosure, the first control logic further includes control logic for generating a predicted turbocharger shaft speed from a sum of a measured turbocharger shaft speed and a rate of change of the turbocharger shaft speed over a predetermined prediction horizon. The measured turbocharger shaft speed is determined by one or more of: a direct measurement from the TSS sensor and a modeled turbocharger shaft speed.

[0006] According to another aspect of the present disclosure, the second control logic further includes control logic that, upon determining that the turbocharger shaft speed is greater than or equal to an initialization threshold, initializes the SSCA. Upon determining that the turbocharger shaft speed is less than the initialization threshold, the control logic reacquires the measured turbocharger shaft speed and the rate of change of the turbocharger shaft speed over the predetermined prediction horizon. Upon determining that the turbocharger shaft speed has fallen below the initialization threshold, the control logic exits the SSCA, reacquiring the measured turbocharger shaft speed and the rate of change of the turbocharger shaft speed over the predetermined prediction horizon.

[0007] According to another aspect of the present disclosure, the third control logic further includes control logic for calibrating the upper limit based on the physical characteristics of the turbocharger to a maximum possible turbocharger flow, and control logic for calibrating the lower limit to a target turbocharger flow correction for closed-loop control while SSCA is being executed. The upper limit and the lower limit are enforced at the turbocharger using actuators including a throttle valve of the ICE and a wastegate of the turbocharger.

[0008] According to another aspect of the present disclosure, the initialization threshold further includes a lookup table that multiplies the actual ICE mass flow rate by a factor based on a filtered rate of change of turbocharger shaft speed at a time the SSCA is initialized.

[0009] According to another aspect of the present disclosure, the fourth control logic further includes control logic for applying closed-loop calculations to a calibrated turbocharger target shaft speed, outputting a desired mass flow rate through the turbocharger compressor, and translating the desired mass flow rate into a cylinder air mass for the ICE boost control system.

[0010] According to another aspect of the present disclosure, the fourth control logic further includes control logic that applies a throttle pressure ratio request based on the predicted turbocharger shaft speed and the current rate of change of the turbocharger shaft speed, and control logic that maintains a constant turbocharger shaft speed and a constant flow below the upper limit and above the lower limit.

[0011] According to another aspect of the present disclosure, the sixth control logic further includes control logic for selectively applying a slow learn limit, a fast learn limit, an upper learn limit, and a zero factor to the turbocharger shaft speed settings.The slow learning limit is applied when the turbocharger shaft speed is within a first predetermined threshold that is greater than the calibrated turbocharger target shaft speed, the fast learning limit is applied when the turbocharger shaft speed is within a second predetermined threshold that is greater than the first predetermined threshold and greater than the calibrated turbocharger target shaft speed, the high learning limit is applied when the turbocharger shaft speed is within a third predetermined threshold that is less than the calibrated turbocharger target shaft speed, and the zero factor is applied when the turbocharger shaft speed is substantially equal to the calibrated turbocharger target shaft speed.The slow learn limit, fast learn limit, high learn limit, and zero factor are continuously applied to turbocharger shaft speed settings while SSCA is running.

[0012] According to a further aspect of the present disclosure, the first predetermined threshold is 500 revolutions per minute (min -1 ) above the calibrated target speed, the second predefined threshold is 1000 min -1 greater than the calibrated target speed and the upper learning limit is 500 min -1 less than the calibrated target speed.

[0013] According to another aspect of the present disclosure, the SSCA modifies the predicted turbocharger shaft speed by applying a multiplication factor that takes into account ICE and turbocharger aging.

[0014] According to another aspect of the present disclosure, a method for controlling turbocharger shaft speed for an internal combustion engine (ICE) includes detecting at least a turbocharger shaft speed and a mass flow rate through the ICE with one or more sensors disposed on the ICE and the turbocharger. The method further includes selectively adjusting a mass flow rate through the ICE and the turbocharger with one or more actuators. The one or more actuators and the one or more sensors define the components of a boost control system. The method further includes utilizing one or more control modules. Each of the one or more control modules includes a processor, memory, and one or more input / output (I / O) ports.The one or more control modules communicate with the one or more sensors via the I / O ports and communicate with the one or more actuators. The memory stores program control logic. The processor executes the program control logic. The program control logic includes control logic for: generating a predicted turbocharger shaft speed from the data acquired by a turbocharger shaft speed (TSS) sensor of the one or more sensors; and selectively initializing a turbocharger shaft speed control algorithm (turbocharger SSCA). The method generates a lower limit and an upper limit, greater than the lower limit, for an amount of turbocharger flow correction to be applied via the one or more actuators.The method applies a control output to the one or more actuators to control a mass flow rate through a compressor of the turbocharger. The method selectively determines that the turbocharger shaft speed has exceeded a predetermined threshold and uses the one or more actuators to directly change a pressure ratio of the ICE. The method applies a long-term memory learning process to fine-tune turbocharger performance, which uses data from the one or more sensors and the one or more actuators as inputs to fine-tune turbocharger performance. The method causes the turbocharger to stably operate at an optimal shaft speed within predetermined hardware limits while maintaining a constant flow rate over a range of pressure ratios.

[0015] According to another aspect of the present disclosure, the method further includes generating a predicted turbocharger shaft speed from a sum of a measured turbocharger shaft speed and a rate of change of the turbocharger shaft speed over a predetermined prediction horizon. The measured turbocharger shaft speed is determined by one or more of: a direct measurement from the TSS sensor and a modeled turbocharger shaft speed.

[0016] According to another aspect of the present disclosure, the method initializes the SSCA upon determining that the turbocharger shaft speed is greater than or equal to an initialization threshold, and reacquires the measured turbocharger shaft speed and the rate of change of the turbocharger shaft speed over the predetermined prediction horizon upon determining that the turbocharger shaft speed is less than the initialization threshold. Upon determining that the turbocharger shaft speed has fallen below the initialization threshold, the method exits the SSCA and reacquires the measured turbocharger shaft speed and the rate of change of the turbocharger shaft speed over the predetermined prediction horizon.

[0017] According to another aspect of the present disclosure, the method calibrates the upper limit to a maximum possible turbocharger flow based on the physical characteristics of the turbocharger, and calibrates the lower limit to a target turbocharger flow correction for closed-loop control while SSCA is being executed. The method enforces the upper limit and lower limit on the turbocharger using actuators including an ICE throttle and a turbocharger wastegate.

[0018] According to another aspect of the present disclosure, the method determines that the turbocharger shaft speed is greater than or equal to an initialization threshold, wherein the initialization threshold is determined by applying a lookup table that multiplies the actual mass flow rate of the ICE by a factor based on a filtered rate of change of the turbocharger shaft speed at a time the SSCA is initialized.

[0019] According to another aspect of the present disclosure, the method applies control calculations to a calibrated turbocharger target shaft speed, outputting a desired mass flow rate through the turbocharger compressor, and translating the desired mass flow rate into a cylinder air mass for the ICE boost control system.

[0020] According to another aspect of the present disclosure, the method applies a throttle pressure ratio request based on the predicted turbocharger shaft speed and the current rate of change of the turbocharger shaft speed, while maintaining a constant turbocharger shaft speed and a constant flow below the upper limit and above the lower limit.

[0021] According to another aspect of the present disclosure, the method selectively applies a slow learn limit, a fast learn limit, an upper learn limit, and a zero factor to the turbocharger shaft speed settings.The slow learning limit is applied when the turbocharger shaft speed is within a first predetermined threshold that is greater than the calibrated turbocharger target shaft speed, the fast learning limit is applied when the turbocharger shaft speed is within a second predetermined threshold that is greater than the first predetermined threshold and greater than the calibrated turbocharger target shaft speed, the high learning limit is applied when the turbocharger shaft speed is within a third predetermined threshold that is less than the calibrated turbocharger target shaft speed, and the zero factor is applied when the turbocharger shaft speed is substantially equal to the calibrated turbocharger target shaft speed.The slow learn limit, fast learn limit, high learn limit, and zero factor are continuously applied to the turbocharger shaft speed settings while SSCA is running. The first predefined threshold is 500 rpm (min. -1 ) above the calibrated target speed, the second predefined threshold is 1000 min -1 greater than the calibrated target speed and the upper learning limit is 500 min -1 less than the calibrated target speed.

[0022] According to another aspect of the present disclosure, the method further includes modifying the predicted turbocharger shaft speed by applying a multiplication factor that accounts for ICE and turbocharger aging.

[0023] According to another aspect of the present disclosure, a system for controlling turbocharger shaft speed in an internal combustion engine (ICE) includes a boost control system having one or more sensors and one or more actuators, wherein the one or more sensors detect at least one turbocharger shaft speed and a mass flow rate through the internal combustion engine, and the one or more actuators selectively adjust the mass flow rate through the ICE and the turbocharger. The system further includes one or more control modules, each of the one or more control modules having a processor, memory, and one or more input / output (I / O) ports, the one or more control modules communicating with the one or more sensors via the I / O ports and communicating with the one or more actuators. The memory stores program control logic.The processor executes the program control logic. The program control logic includes at least first, second, third, fourth, fifth, and sixth control logic. The first control logic generates a predicted turbocharger shaft speed from a sum of a measured turbocharger shaft speed and a rate of change of the turbocharger shaft speed over a predetermined prediction horizon. The measured turbocharger shaft speed and the rate of change of the turbocharger shaft speed are determined by one or more of: a direct measurement from a turbocharger shaft speed (TSS) sensor and a modeled turbocharger shaft speed. The second control logic selectively initializes a turbocharger shaft speed control algorithm (turbocharger SSCA) that includes: control logic that initializes the SSCA upon determining that the turbocharger shaft speed is greater than or equal to an initialization threshold. The SSCA includes control logic that reacquires the measured turbocharger shaft speed and the rate of change of the turbocharger shaft speed over the predetermined prediction horizon upon determining that the turbocharger shaft speed is less than the initialization threshold. The SSCA further includes control logic that exits the SSCA and reacquires the measured turbocharger shaft speed and the rate of change of the turbocharger shaft speed over the predetermined prediction horizon upon determining that the turbocharger shaft speed has fallen below the initialization threshold.The initialization threshold includes a lookup table that multiplies the actual ICE mass flow rate by a factor based on a filtered rate of change in turbocharger shaft speed at a time the SSCA is initialized. Third control logic is located within the SSCA and generates a lower limit and an upper limit, greater than the lower limit, for an amount of turbocharger flow correction to be applied via the one or more actuators. The third control logic further includes control logic for calibrating the upper limit based on the physical characteristics of the turbocharger to a maximum possible turbocharger flow and control logic for calibrating the lower limit to a target turbocharger flow correction for closed-loop control while the SSCA is executing.The upper and lower limits are enforced on the turbocharger using actuators that include an ICE throttle valve and a turbocharger wastegate. The fourth control logic is located within the SSCA and applies a closed-loop control output to the one or more actuators to control a mass flow rate through a turbocharger compressor. The fourth control logic also applies closed-loop calculations to a calibrated turbocharger target shaft speed, outputs a desired mass flow rate through the turbocharger compressor, and converts the desired mass flow rate into a cylinder air mass for the ICE boost control system.The fourth control logic further applies a throttle pressure ratio request based on the predicted turbocharger shaft speed and the current rate of change of the turbocharger shaft speed, and maintains a constant turbocharger shaft speed and constant flow below the upper limit and above the lower limit. The fifth control logic is within the SSCA and selectively determines that the turbocharger shaft speed has exceeded a predetermined threshold and applies the one or more actuators to directly change a pressure ratio of the ICE. The sixth control logic is within the SSCA and applies a long-term memory learning process that uses the data from the one or more sensors and the one or more actuators as inputs to fine-tune turbocharger performance.The sixth control logic further includes control logic for selectively applying a slow learn limit, a fast learn limit, an upper learn limit, and a zero factor to the turbocharger shaft speed settings.The slow learning limit is applied when the turbocharger shaft speed is within a first predetermined threshold that is greater than the calibrated turbocharger target shaft speed, the fast learning limit is applied when the turbocharger shaft speed is within a second predetermined threshold that is greater than the first predetermined threshold and greater than the calibrated turbocharger target shaft speed, the high learning limit is applied when the turbocharger shaft speed is within a third predetermined threshold that is less than the calibrated turbocharger target shaft speed, and the zero factor is applied when the turbocharger shaft speed is substantially equal to the calibrated turbocharger target shaft speed.The slow learn threshold, fast learn threshold, high learn threshold, and zero factor are continuously applied to the turbocharger shaft speed settings while SSCA is running. The first predefined threshold is 500 rpm (min. -1 ) above the calibrated target speed, the second predefined threshold is 1000 min -1 greater than the calibrated target speed and the upper learning limit is 500 min -1 less than the calibrated target speed. The SSCA causes the turbocharger to operate stably at an optimal shaft speed within specified hardware limits while maintaining a constant flow rate over a range of pressure ratios. Furthermore, the SSCA includes control logic that modifies the predicted turbocharger shaft speed by applying a multiplication factor that accounts for ICE and turbocharger aging.

[0024] Further areas of application will become apparent from the description provided herein. It should be understood that the description and specific examples are provided for illustrative purposes only. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described here are for illustrative purposes only; they show: Fig. 1 is a graphical representation of a vehicle having a system and method for controlling turbocharger shaft speed of an internal combustion engine (ICE) according to an aspect of the present disclosure; Fig. 2 a compressor map for a turbocharger in the system according to Fig. 1 for controlling ICE turbocharger shaft speed according to one aspect of the present disclosure; Fig. 3A is a flowchart illustrating a first set of logical steps of the system and method for controlling ICE turbocharger shaft speed according to Fig. 1 according to one aspect of the present disclosure; Fig. 3B is a flowchart illustrating a second set of logical steps of the system and method for controlling ICE turbocharger shaft speed according to Fig. 1 according to one aspect of the present disclosure; and Fig. 4 is a flowchart illustrating a long-term memory learning process for the system and method for controlling ICE turbocharger shaft speed according to Fig. 1 according to one aspect of the present disclosure. DETAILED DESCRIPTION

[0026] The following description is merely exemplary.

[0027] Fig. 1 shows a system 10 for controlling an internal combustion engine (ICE) 12 having a boosting device such as a turbocharger 14. The system 10 operates to accurately, precisely, and quickly control the shaft speed of the turbocharger 14 to achieve optimal power density of the ICE 12 under various different operating conditions. The ICE 12 shown is depicted within a vehicle 16, however, it should be recognized that the ICE 12 may be disposed within a vehicle 16 or may be a stationary ICE 12 used to power any number of other systems not specifically shown.Furthermore, it should be appreciated that while the ICE 12 shown is depicted as a V8, other configurations of the ICE 12 are contemplated, including, but not limited to, rotary engines, radial engines, inline engines, V-engines, horizontally opposed engines, or any other form of ICE 12 with one or more turbochargers 14. Likewise, it should be appreciated that the ICE 12 may be a gasoline-powered ICE 12 or may combust other types of fuels, including, but not limited to, diesel, natural gas, propane, hydrogen, or the like, without departing from the scope or intent of the present disclosure. The vehicle 16 shown is a passenger vehicle; additionally, it should be appreciated that the vehicle 16 may be any type of vehicle 16 that utilizes an ICE 12 without departing from the scope or intent of the present disclosure.According to several examples, vehicle 16 may include a passenger car, a truck, a sport utility vehicle (SUV), a semi-trailer truck, a tractor, a bus, a motorcycle, a motor scooter; an aircraft such as an airplane, a helicopter; or a watercraft such as a motorboat, a seaplane, hovercraft, or the like.

[0028] The system 10 includes the ICE 12, which has a turbocharger 14 attached thereto. The turbocharger 14 further includes a compressor 15 and a turbine 17. The turbine 17 is attached to a turbocharger shaft (not specifically shown) at a first end, while the compressor 15 is attached to the turbocharger shaft at a second end opposite the first end. The turbine 17 is driven by the exhaust gases generated by the operation of the ICE 12. As the turbine 17 rotates, this causes the compressor 15 to rotate and draw fresh air into the turbocharger 14, where it is compressed and then fed into the ICE 12 at a pressure higher than ambient air pressure.

[0029] The ICE 12 and the turbocharger 14 are equipped with various sensors 18 and actuators 20, including, but not limited to, a throttle body 22, a wastegate valve 24, an intake airflow (IAF) sensor 26, and a turbocharger shaft speed (TSS) sensor 28. In several aspects, the ICE 12 and the turbocharger 14 are equipped with a boost control system (BCS), which may be electronic (EBCS), manual (MBCS), or a combination thereof. The BCS of the ICE 12 and the turbocharger 14 may further include the sensors 18 and the actuators 20, such as a boost control solenoid (not specifically shown) that controls one or more of the wastegate valve 24 and a wastegate valve, such as a boost pressure relief valve. B. a bypass valve or a blow-off valve 27, in conjunction with the boost pressure control valve 24.The IAF sensor 26 may be any of various different sensors 18 used to detect air movement, air volume, and / or air pressure within the intake tract 29 of the ICE 12. Accordingly, the IAF sensor 26 may be one or more of a mass air flow (MAF) sensor, a manifold absolute pressure (MAP) sensor, or the like. Additionally, it should be appreciated that any number of IAF sensors 26 may be present in the system 10 and detect intake airflow information within the system 10 without departing from the scope or intent of the present disclosure. According to further examples, the sensors 18 and actuators 20 include torque sensors, intake air temperature sensors, exhaust temperature sensors, chassis dynamics sensors, powertrain actuators, chassis dynamics actuators such as active suspension components, or the like.The sensors 18 and the actuators 20 communicate with one or more control modules 30.

[0030] In several aspects, the one or more control modules 30 each define non-generalized electronic control devices having a pre-programmed digital computer or processor 32, a non-transitory computer-readable medium or memory 34 used to store data, such as control logic, software applications, instructions, computer code, data, lookup tables, etc., and one or more input / output (I / O) ports 36. The computer-readable medium or memory 34 includes any type of medium accessible by a computer, such as read-only memory (ROM), random access memory (RAM), a hard disk drive, a compact disk (CD), a digital video disk (DVD), solid-state storage, or any other type of memory.A "non-transitory" computer-readable medium or "non-transitory" computer-readable memory 34 excludes wireless, optical, or other communication connections that carry electrical or other signals. A non-transitory computer-readable medium or non-transitory computer-readable memory 34 includes media in which data can be permanently stored and media in which data, such as any type of program code, including source code, object code, and executable code, can be stored and later overwritten. The processor 32 is configured to execute the code or instructions. According to some examples, the control module 30 may be a dedicated wireless or Wi-Fi controller. The I / O ports 36 are configured to communicate via wired or wireless means using Wi-Fi protocols conforming to IEEE 802.11x, Bluetooth communication protocols, radio frequency (RF) protocols, or the like.

[0031] In several aspects, the control modules 30 include one or more applications 38. An application 38 is a software program configured to perform specific functions or sets of functions. The application 38 may include one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, associated data, or a portion thereof, adapted for implementation in suitable computer-readable program code. The applications 38 may be stored within the memory 34 or in an additional or separate memory 34. Examples of the applications 38 include powertrain management services, such as ICE 12 control services, transmission 39 control services, chassis control services, brake control services, audio or video streaming services, audio or visual processing services, and the like.According to several examples, the applications 38 include a shaft speed control application (SSCA) 40 of the turbocharger 14. The SSCA 40 is used to manage the performance characteristics of the ICE 12 and the attached turbocharger 14.

[0032] In Fig. 2 and further with regard to Fig. 1, a compressor map 50 of the turbocharger 14 is shown. The compressor map 50 represents the corrected air mass flow rate along the X-axis and a pressure ratio across the turbocharger 14 along the Y-axis. The compressor map 50 further represents an example of the standard operating conditions 52 of the turbocharger 14, as well as plots of the high-temperature operating conditions 54 and a throttled flow region 56. In several aspects, it should be appreciated that when operating in the throttled flow region 56, the gas flow through the turbocharger 14 has the potential to become more unstable due to a decrease in the required compressor power for a given flow and flow instabilities.The operating conditions for the throttled flow region 56 vary for different compressor 15 and ICE 12 designs, but are generally represented by the close proximity and high rate of rise of the edges of the efficiency islands 58 of the compressor map 50 and the region of the compressor map 50 where the speed lines 60 begin to converge. In the throttled flow region 56, a small increase in flow provides a large increase in the turbocharger 14 shaft speed and a decrease in the compressor 15 efficiency. The efficiency islands 58 are represented as differently shaded regions of the compressor map 50 and are graphical representations of the relative ability of the turbocharger 14 to compress air without generating excessive heat. The higher the efficiency, the cooler the outlet temperature for a given turbocharger 14 boost pressure.A left boundary 62 of the compressor map 50 defines a compressor surge line that represents a maximum amount of pressure that the turbocharger 14 can generate while flowing the least possible air mass.

[0033] In contrast, the right boundary of the compressor map 50 defines an absolute choke line 64. The absolute choke is the maximum amount of air that the turbocharger's compressor 15 can flow at a given pressure ratio. When the turbocharger 14 operates at or near the absolute choke line 64 or choke region 56 of the compressor map 50, the compressor 15 outlet temperatures and the turbocharger 14 shaft speed increase rapidly. The rapid increase in the turbocharger 14 shaft speed along the absolute choke line 64 indicates a maximum flow limit of the turbocharger 14.

[0034] The compressor map 50 further includes a plurality of example shaft speed lines 60 of the turbocharger 14. The shaft speed lines 60 represent a specific speed of the turbocharger shaft. As the compressor map 50 shows, the shaft speed of the turbocharger 14 near the choke line 64 is close to a maximum possible value, and the flow rate is also approaching a maximum. Accordingly, for maximum output of the turbocharger 14 and maximum power output of the ICE 12, it is beneficial to maintain the shaft speed of the turbocharger 14 within or near the throttled flow region 56. However, maintaining operation of the turbocharger 14 within the throttled flow region 56 is challenging due to the potential for unstable and uneven control of the shaft speed of the turbocharger 14.To maintain operation of the turbocharger 14 in high performance situations within or immediately adjacent to the restricted flow region 56, the system 10 utilizes the SSCA 40.

[0035] In the Fig. 3A and Fig. 3B, the SSCA 40 is shown in more detail in flowchart form. The SSCA 40 manages the shaft speed of the turbocharger 14 at a maximum speed, where the maximum speed is defined by calibrated hardware and software limits described in more detail herein. In several aspects, the SSCA 40 operates to control the shaft speed of the turbocharger 14 via the operation of one or more actuators 20 when a predetermined set of initialization conditions are met and until exit conditions are met. The SSCA 40 begins in block 200. In block 202, the SSCA 40 determines whether the ICE 12 is active and running. If the SSCA 40 determines that the ICE 12 is inactive, the SSCA 40 returns to block 200, beginning the cycle again. The SSCA 40 can run continuously, cyclically, or periodically to determine whether the ICE 12 is running.

[0036] Upon determining at block 202 that the ICE 12 is active and running, the SSCA 40 proceeds to block 204, where the SSCA 40 performs a lookup procedure to determine a prediction horizon from one or more lookup tables and / or prediction calibrations. In several aspects, the lookup tables and / or prediction calibrations include a turbine power 206, a compressor power 208, an engine speed rate of change (dn) 210, and an atmospheric pressure 212. In several aspects, the turbine power 206, the compressor power 208, the engine speed dn 210, and the atmospheric pressure 212 are based on both live data from the one or more sensors 18 and actuators 20, as well as predetermined information generated through test procedures or the like.According to further examples, the forecast horizon is a calibrated value based on the lookup tables of the power ratio of turbine 17, the speed change rate of ICE 12, and the atmospheric pressure compensation factors that take into account the ambient air density.

[0037] In block 214, a turbo speed rate of change (dn) 216 is obtained from the TSS sensor 28 via the I / O ports 36 and multiplied by the prediction horizon from block 204. In several aspects, the turbocharger speed dn 216 is a filtered rate of change of the shaft speed of the turbocharger 14. In block 218, a shaft speed 220 of the turbocharger 14 is obtained from the TSS sensor 28. The prediction horizon and the turbocharger speed dn 216 are combined to generate a predicted shaft speed 217 of the turbocharger 14. In some aspects, the shaft speed 220 of the turbocharger 14 is filtered to reduce erroneous data or noise in the data.It should be appreciated that the TSS sensor 28 may directly measure the shaft speed data from the shaft of the turbocharger 14, or the outputs of the TSS sensor 28 may be modeled or interpolated from data obtained by other sensors 18 of the system 10 without departing from the scope or intent of the present disclosure. According to some examples, the shaft speed of the turbocharger 14 may be modeled by the IAF sensors 26, the intake air temperature sensors, the exhaust gas temperature sensors, the boost pressure sensors, or the like without departing from the scope or intent of the present disclosure.

[0038] In block 222, the SSCA 40 compares a turbocharger 14 shaft speed limit calibration 224 and a turbocharger 14 target shaft speed calibration 226 with the predicted turbocharger shaft speed 217 and the turbocharger 14 shaft speed data 220 from block 218. According to several aspects, the turbocharger 14 shaft speed limit and the target calibrations 224, 226 are subtracted from the data from block 218. The results of the comparison are output as a turbocharger 14 speed limit difference 228 and a turbocharger 14 target speed difference 230. According to several aspects, the turbocharger 14 speed limit difference 228 is a difference between a current operating turbocharger 14 shaft speed and a predetermined turbocharger 14 shaft speed limit.In several aspects, the turbocharger 14 shaft speed limit is one or more of a hardware-defined limit or a calibrated limit determined through testing and stored in memory 34. Likewise, the turbocharger target speed difference 230 is a difference between a target turbocharger 14 shaft speed for a given set of conditions and the current turbocharger 14 shaft speed as measured by the TSS sensor 28.

[0039] In block 232, an initialization threshold 234 of the target shaft speed of the turbocharger 14 is compared to the turbocharger speed limit and the target speed differences 228, 230. If the turbocharger speed limit and the target speed differences 228, 230 are less than the initialization threshold 234 of the target shaft speed, the SSCA 40 returns to block 204, where the prediction horizon calibrations are again obtained. However, upon determining that the turbocharger speed limit and the target speed differences 228, 230 are greater than or equal to the initialization threshold 234 of the target shaft speed, the SSCA 40 proceeds to block 236.

[0040] In block 236, the SSCA 40 looks up an initialization factor based on a calibration curve that is based at least in part on the turbo speed change rate 216. In several aspects, the initialization factor calibration curve is defined by a series of experimentally determined values ​​that are applied as multiplicative weights to set the initial target airflow 242. More specifically, the larger the turbo speed change rate (dn) 216, the smaller the initialization factor drawn from the initialization factor calibration curve. Likewise, the smaller the turbo speed dn 216, the higher the initialization factor drawn from the initialization factor calibration curve. According to one example, the initialization factor calibration curve may be calculated for a turbo speed dn of 0 revolutions per minute (min -1 ) per second (min -1 / s) or less than 1.0 and for a turbo speed dn of 2000 min -1 / s 0.8. That is, if the turbo speed change rate is less than or equal to 0 min -1 / s, the initial target airflow 242 is equal to the current engine airflow 240, while when the turbo speed change rate is 2000 min -1 / s, the initial target air flow 242 is smaller than the current engine air flow 240.

[0041] In block 238, the initialization factor from block 236 and a current airflow value 240 of the ICE 12 are combined to generate an initial target airflow value 242. In several aspects, the current airflow value 240 of the ICE 12 may be obtained through one or more direct or indirect measurements, including data obtained directly or indirectly from the IAF sensor 26 and / or calculated from the boost pressure sensors, exhaust flow sensors, a position of the throttle valve 22, or the like. In several aspects, the initial value of the target flow 242 defines an input to a proportional-integral-derivative (PID) control loop 246 of the SSCA 40, which operates to manage the shaft speed of the turbocharger 14 within the throttled flow region 56 while the system 10 is operating.

[0042] Specifically in Fig. 3B and further with regard to the Fig. 1-2 and 3A, the PID control loop 246 of the SSCA 40 is shown in more detail. In several aspects, the PID control loop 246 is a closed-loop control that includes both proportional and integral processes operating simultaneously, in parallel, and at least partially interdependently.

[0043] In block 244, the SSCA 40 begins the integral portion by accessing one or more integral lookup tables. The integral lookup tables are populated with data that are functions of the target turbocharger speed differential 230, the turbine inlet temperature 248, and the compressor outlet temperature 250. In block 252, the integral values ​​from the lookup tables are limited by applying a minimum integral calibration 254 and a maximum integral calibration 256. That is, based on the target turbocharger speed differential 230, the turbine inlet temperature 248, the compressor outlet temperature 250, and the initial target flow rate 242, the SSCA 40 limits the integral output in block 252. The limited integral output is then sent to block 258, where the limited integral output is combined with an output from the long-term memory 260.

[0044] In Fig. 4 and further with regard to the Fig. 1-3B, the long-term memory 260 is shown in more detail. The long-term memory 260 is generated through a learning process, which may be performed continuously, periodically, recursively, and / or through a hard-coded data set by a manufacturer without departing from the scope or intent of the present disclosure. It should be appreciated that, to ensure consistent results, the long-term memory 260 checks the current stability of the system 10 before actively updating any data stored therein. In several aspects, the initialization criteria for the learning process of the long-term memory 260 include: determining that the turbo speed dn 216 is within calibrated limits, the engine speed dn 210 is relatively stable, the exhaust temperatures are below a calibrated limit, such asThe values ​​can be as high as approximately 1100°C, and the atmospheric pressure is higher than a certain threshold, but are by no means limited to this. According to one specific example, the atmospheric pressure can be calibrated to a given maximum altitude with some allowance for weather fluctuations.

[0045] According to several aspects, the long-term memory 260 includes a slow learn limit 300, a fast learn limit 302, and an upper learn limit 304. Each of the slow learn, fast learn, and upper learn limits 300, 302, 304 is based on the differences between the actual shaft speed of the turbocharger 14 and the target shaft speed for a given set of circumstances. According to one example, the slow learn limit may be based on a difference of 500 revolutions per minute (min -1) between the actual shaft speed and the target shaft speed for the turbocharger 14. That is, the slow learning limit 300 can be applied when the actual shaft speed of the turbocharger 14 is approximately 500 min -1 greater than the target shaft speed. Similarly, the fast learning limit can be applied if the actual shaft speed of the turbocharger 14 is approximately 1000 rpm -1 greater than the target shaft speed, while the upper learning limit can be applied when the actual shaft speed of the turbocharger is 14 500 min -1 or more less than the target shaft speed. The slow, fast, and upper learning limits 300, 302, 304 are compared to the turbocharger speed limit difference 228 in block 306.

[0046] Upon determining that the actual shaft speed of the turbocharger 14 is within the slow learn limit 300, a slow learn calibration 308 is applied. Upon determining that the actual shaft speed of the turbocharger 14 is within the fast learn limit 302, a fast learn calibration 310 is applied. Upon determining that the actual shaft speed of the turbocharger 14 is within the upper learn limit 304, an upper learn calibration 312 is applied. Upon determining that none of the slow learn limit 300, the fast learn limit 302, or the upper learn limit 304 is applicable, the SSCA 40 applies a zero factor 314 to the shaft speed of the turbocharger 14.To generate a properly calibrated correction to the long-term memory 260, the SSCA 40 takes a current speed 316 of the ICE 12 and a current pressure ratio 318 of the compressor 15 as inputs to look up a current long-term memory value 320. In block 322, the current long-term memory value 320 is translated into an output for the PID control loop 246. The data from block 322 is combined in block 324 with that of the slow learn calibration 308, the fast learn calibration 310, the high learn calibration 312, and / or the zero factor 314, whichever is appropriate given the actual and target shaft speeds of the turbocharger 14. The minimum and maximum limits for the output of the long-term memory 260 are applied to the data from block 324, with the resulting values ​​being stored within the table of the long-term memory 260.As indicated above, the learning process of the long-term memory 260 may be performed continuously, periodically, and / or recursively to fine-tune the outputs of the SSCA 40 or otherwise cause the outputs of the SSCA 40 to accurately, precisely, and quickly adjust the shaft speed of the turbocharger 14 to match the target shaft speed, thereby maintaining the performance and operation of the turbocharger 14 within the throttled flow region 56. The long-term learning is generally biased to learn downward more easily than upward to provide a margin for hardware safety. Additionally, several different learning rates for downward learning may be applied based at least in part on a difference between the current and target shaft speeds of the turbocharger 14.

[0047] Again in Fig. 3B and further with regard to the Fig.1-3A and 4, the SSCA 40 begins the proportional section by accessing one or more proportional lookup tables 262. The proportional lookup tables 262 are populated with data that are functions of the target turbocharger speed difference 230, the turbine inlet temperature 248, and the compressor outlet temperature 250. In block 264, an output of the proportional lookup tables 262 is combined with the data from block 258, producing a target flow rate 266. The target flow rate 266 defines a flow rate of the turbocharger 14 that optimally causes the turbocharger 14 to operate within the throttled flow region 56 without over-revving or otherwise approaching hardware or software limits and to maintain thermal performance targets.A minimum flow control calibration 268 and a maximum flow control calibration 270 are applied to the target flow 266 at block 272. In some aspects, the minimum and maximum flow control calibrations 268, 270 define lower and upper limits for the amount of turbocharger 14 flow correction that may be requested for a particular set of inputs. In some examples, a maximum flow calibration 270 may be approximately 500 grams / second of air, while a minimum flow calibration may be approximately 350 grams / second of air, although the minimum and maximum flow calibrations 268, 270 may vary significantly from the values ​​discussed above depending on the specific hardware in system 10 and the like.By applying the minimum and maximum flow control calibrations 268, 270, large, erratic, and / or undesirable flow fluctuations of the turbocharger 14 may be avoided. In several aspects, the minimum and maximum flow calibrations 268, 270 may be enforced through the use of the one or more actuators 20 of the system 10. The maximum flow calibration 270 may also be a hardware-imposed limit for the turbocharger 14, wherein the throttle 22 and the wastegate 24 may operate individually or in conjunction to enforce the maximum flow calibration 270. Likewise, the minimum flow calibration 268 may be enforced through actuation of the throttle 22 and the wastegate 24.However, the minimum flow calibration 268 is not a hardware-imposed limit, but rather a lower limit used in control during the PID control loop 246.

[0048] At block 274, the SSCA 40 performs a comparison of the turbocharger 14 speed difference limit 228, the turbocharger 14 shaft speed limit calibration 224, the turbocharger 14 target shaft speed calibration 226, and the turbocharger 14 current shaft speed 220. Upon determining that the turbocharger 14 speed difference limit 228 is greater than or equal to a turbocharger 14 speed limit threshold and the turbocharger 14 current shaft speed 220 is greater than or equal to the turbocharger 14 target shaft speed calibration 226, the SSCA 40 proceeds to block 276 where a lookup calibration of the desired throttle pressure ratio is applied.However, upon determining that the turbocharger 14 speed difference limit 228 is less than the turbocharger 14 speed limit threshold and / or the current turbocharger 14 shaft speed 220 is less than the turbocharger 14 target shaft speed calibration 226, the SSCA 40 proceeds to block 278 where the SSCA 40 does not execute a throttle request.

[0049] At block 280, a flow limit of the turbocharger 14 and a pressure ratio request value are passed as a limit and / or request to the torque control system of the ICE 12. That is, the SSCA 40 uses both the limited flow output from block 272 and the throttle request information from blocks 276 or 278 to define the operating conditions for the torque control system. In several aspects, at block 280, the SSCA 40 uses the current or predicted speed of the ICE 12 as an input to the torque control system request. According to some examples, the torque control system request may be a direct pressure ratio request. It should be appreciated that the wastegate or multiple wastegates 24 of the ICE 12 have hardware-related rate limits.That is, the wastegate valves 24 may be capable of moving from fully closed to open, or vice versa, in approximately one second. The one-second delay at such a position affects how well the wastegate valves 24 can manage the speed of the turbine 17 and, therefore, the shaft speed of the turbocharger 14. To quickly, accurately, and precisely adjust the speed of the turbine 17, the shaft speed of the turbocharger 14, and the power of the turbocharger 14, the system 10 uses the one or more throttle bodies 22 of the system 10 to quickly change the flow through the ICE 12 and, therefore, the flow through the turbine 17 of the turbocharger 14. That is, the throttle bodies 22 are faster-acting actuators 20 than the wastegate valves 24 and have the capability of moving from fully closed to fully open, or vice versa, many times faster than the wastegate valves 24.According to some examples, the throttle valves 22 can move from fully closed to fully open, or vice versa, in less than a quarter of a second. Accordingly, the throttle valves 22 provide rapid control, allowing them to quickly change the gas flow through the ICE 12 and the turbocharger 14. By throttling the boost pressure and increasing the pressure ratio of the compressor 15, the required power of the compressor 15 is quickly increased. The ratio of the required power of the compressor 15 to the available power of the turbine 17 is increased, immediately slowing the shaft speed of the turbocharger 14.Accordingly, the rapid control of actuator 20 via throttle valves 22 allows compressor 15 to operate near maximum speed line 60A in throttled flow region 56 with the ability to almost instantly slow the shaft speed of turbocharger 14 by actuating throttle valve 22 to change flow through ICE 12 and turbine 17.

[0050] In several aspects, the SSCA 40 continuously receives the shaft speed 220 of the turbocharger 14 from the TSS sensor 28, and compares the shaft speed 220 to an exit threshold in block 282. The exit threshold is a predetermined set of values ​​that may vary from application to application and from turbocharger 14 to turbocharger 14, but are generally understood to be values ​​that define a low speed boundary of the throttled flow region 56. The exit speed threshold in block 282 is initialized to an exit threshold speed calibration 284, which may be permanent or may change periodically and / or continuously.In several aspects, the exit threshold speed calibration 284 may differ from application to application and from turbocharger 14 to turbocharger 14 and / or may vary over time as the components of the ICE 12 and turbocharger 14 age and the performance of the ICE 12 and / or turbocharger 14 changes.

[0051] Accordingly, upon determining that the shaft speed 220 of the turbocharger 14 is below the exit threshold speed, the SSCA 40 is exited and normal operation of the control systems of the ICE 12 and the turbocharger 14 resumes in block 286. Specifically, in block 286, a flow limit is set to a predetermined maximum value defined in software, and the throttle requests are released. The SSCA 40 terminates in block 288.

[0052] Upon determining that the shaft speed 220 of the turbocharger 14 is greater than or equal to the exit threshold speed, the SSCA 40 proceeds to block 290, wherein the PID control loop 246 is executed continuously, iteratively, recursively, or the like, until it is determined at block 282 that the shaft speed 220 of the turbocharger 14 is below the exit threshold speed, at which point the SSCA 40 proceeds to blocks 286 and 288, as described above.

[0053] A system and method for controlling the shaft speed of the turbocharger 14 of the ICE 12 of the present disclosure offers several advantages. These include the ability to very precisely, quickly, and accurately control and / or limit the torque and power of the ICE 12 at a given turbocharger 14 speed target by increasing the flow of the compressor 15 and / or the ICE 12 to meet the targets as needed, while utilizing pre-existing assemblies and reducing complexity.Additionally, the system 10 and method of the present disclosure provide the ability to control the shaft speed of the turbocharger 14 of the ICE 12 within the throttled flow region 56 to optimize the output of the turbocharger 14 and the ICE 12 with robust and redundant control through the use of multiple separate control functionalities working together to limit the airflow through the ICE 12 and physically increase the pressure ratio across the compressor 15, which increases the performance of the compressor 15.

Claims

[1] A system (10) for controlling turbocharger shaft speed for an internal combustion engine (ICE) (12), the system (10) comprising: a boost pressure control system having one or more sensors (18, 26, 28) and one or more actuators (20, 22, 24), wherein the one or more sensors (18, 26) detect at least one turbocharger shaft speed and a mass flow rate through the ICE (12), and the one or more actuators (20, 22, 24) selectively adjust the mass flow rate through the ICE (12) and the turbocharger (14); one or more control modules (30), each of the one or more control modules (30) comprising a processor (32), a memory (34), and one or more input / output ports (I / O ports) (36), the one or more control modules (30) communicating with the one or more sensors (18, 26, 28) and communicating with the one or more actuators (20, 22, 24) via the I / O ports (36), the memory (34) storing program control logic, the processor (32) executing the program control logic, the program control logic comprising: first control logic for generating a predicted turbocharger shaft speed (217) from data acquired by a turbocharger shaft speed (TSS) sensor (28) of the one or more sensors (18, 26, 28); a second control logic for selectively initializing a turbocharger shaft speed control algorithm (turbocharger SSCA) (40); third control logic within the SSCA (40) for generating a lower limit and an upper limit, greater than the lower limit, for an amount of turbocharger flow correction to be applied via the one or more actuators (20, 22, 24); a fourth control logic within the SSCA (40) for applying a control output to the one or more actuators (20, 22, 24) to control a mass flow through a compressor (15) of the turbocharger (14); a fifth control logic within the SSCA (40) that selectively determines that the turbocharger shaft speed has exceeded a predetermined threshold and that uses the one or more actuators (20, 22, 24) to directly change a pressure ratio of the ICE (12); and a sixth control logic within the SSCA (40) for using a long-term memory learning process that uses the data from the one or more sensors (18, 26, 28) and the one or more actuators (20, 22, 24) as inputs to fine-tune the performance of the turbocharger (14), wherein the SSCA (40) causes the turbocharger (14) to operate stably within predetermined hardware limits at an optimal shaft speed while maintaining a constant flow over a range of pressure ratios. [2] The system (10) of claim 1, wherein the first control logic further comprises: control logic for generating a predicted turbocharger shaft speed (217) from a sum of a measured turbocharger shaft speed and a rate of change (216) of the turbocharger shaft speed over a predetermined prediction horizon, wherein the measured turbocharger shaft speed is determined by one or more of: a direct measurement from the TSS sensor (28) and a modeled turbocharger shaft speed. [3] The system (10) of claim 2, wherein the second control logic further comprises: control logic that initializes the SSCA (40) upon determining that the turbocharger shaft speed is greater than or equal to an initialization threshold (234); a control logic that, upon determining that the turbocharger shaft speed is less than the initialization threshold (234), re-obtains the measured turbocharger shaft speed and the rate of change (216) of the turbocharger shaft speed over the predetermined prediction horizon; and control logic that, upon determining that the turbocharger shaft speed has fallen below the initialization threshold (234), exits the SSCA (40) and re-obtains the measured turbocharger shaft speed and the rate of change (216) of the turbocharger shaft speed over the predetermined prediction horizon. [4] The system (10) of claim 2, wherein the third control logic further comprises: control logic for calibrating the upper limit based on the physical characteristics of the turbocharger to a maximum possible turbocharger flow; and control logic for calibrating the lower limit to a target turbocharger flow correction for control while the SSCA is executing; and wherein the upper limit and the lower limit are enforced at the turbocharger (14) by using actuators including a throttle valve (22) of the ICE (12) and a wastegate valve (24) of the turbocharger (14). [5] The system (10) of claim 3, wherein the initialization threshold (234) further comprises: a lookup table (262) that multiplies the actual mass flow rate of the ICE (12) by a factor based on a filtered rate of change of the turbocharger shaft speed at a time when the SSCA (40) is initialized. [6] The system (10) of claim 3, wherein the fourth control logic further comprises: control logic for applying control loop calculations to a calibrated turbocharger target shaft speed and for outputting a desired mass flow through the compressor (15) of the turbocharger (14) and for converting the desired mass flow into a cylinder air mass for the boost pressure control system of the ICE (12). [7] The system (10) of claim 3, wherein the fourth control logic further comprises: control logic that applies a throttle pressure ratio request based on the predicted turbocharger shaft speed (217) and the current rate of change (216) of the turbocharger shaft speed; and a control logic that maintains a constant turbocharger shaft speed and a constant flow below the upper limit and above the lower limit. [8] The system (10) of claim 7, wherein the sixth control logic further comprises: a control logic for selectively applying a slow learning limit (300), a fast learning limit (302), an upper learning limit (304) and a zero factor (314) to the turbocharger shaft speed settings, wherein the slow learning limit (300) is applied when the turbocharger shaft speed is within a first predetermined threshold that is greater than the calibrated turbocharger target shaft speed, the fast learning limit (302) is applied when the turbocharger shaft speed is within a second predetermined threshold that is greater than the first predetermined threshold and greater than the calibrated turbocharger target shaft speed, the high learning limit (304) is applied when the turbocharger shaft speed is within a third predetermined threshold that is less than the calibrated turbocharger target shaft speed, and the zero factor (314) is applied when the turbocharger shaft speed is substantially equal to the calibrated turbocharger target shaft speed; and wherein the slow learn limit (300), the fast learn limit (302), the high learn limit (304) and the zero factor (314) are continuously applied to the turbocharger shaft speed settings while the SSCA (40) is executed. [9] System (10) according to claim 8, wherein the first predetermined threshold value is 500 revolutions per minute (min -1 ) is above the calibrated target speed, the second predefined threshold is 1000 min -1 greater than the calibrated target speed and the upper learning limit is 500 min -1 is less than the calibrated target speed. [10] The system (10) of claim 2, further comprising: control logic that modifies the predicted turbocharger shaft speed (217) by applying a multiplication factor that takes into account ICE and turbocharger aging.

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