Optimization-based controls for diesel engine air-handling systems

System, apparatus, and methods are disclosed for a computing a first set of parameters based on operational states of an internal combustion engine and an air handling system, a second set of parameters based on a linear time varying model, and one or more control commands based upon a minimization or maximization of a cost function over a prediction horizon, the second set of parameters, and at least one physical constraint of the internal combustion engine, and controlling one or more operations based at least in part upon the one or more control commands. The acts of determining the first and second set of parameters and computing the one or more control commands are repeated over a plurality of time periods over which the first set of parameters and the second set of parameters are time variant.

BACKGROUND

The present application generally relates to optimization-based control methods and control systems for diesel engines including an air handling system, and more particularly to controlling air handling system actuators in such systems. For diesel engines, an insufficient amount of air may lead to an increase in particulate emissions, while an excess of air and low amount of recirculated exhaust gas may lead to an increase in NOx emissions. Present approaches to controls for such systems suffer from a number of limitations and shortcomings. Therefore, a need remains for further improvements in systems, apparatus, and methods for controlling air handling actuators.

SUMMARY

One embodiment is a unique system, method, and apparatus to control air handling actuators in air handling systems of a diesel engine. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. Further embodiments, forms, objects, features, advantages, aspects, and benefits shall become apparent from the following description and drawings.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

With reference toFIG. 1, there is illustrated an air handling system100that includes an engine102, such as an internal combustion engine, in fluid communication with an intake system110through which charge air enters an intake manifold104of the engine102and an exhaust system112through which exhaust gas resulting from combustion in engine102exits via an exhaust manifold106of the engine102, it being understood that not all details of these systems that are typically present are shown. Engine102includes a number of cylinders108forming combustion chambers into which fuel is injected by fuel injectors (not shown) to combust with the charge air that has entered through the intake system110to the intake manifold104. Intake valves (not shown) control the admission of charge air into the cylinders108, and exhaust valves (not shown) control the outflow of exhaust gas through exhaust system106and ultimately to the atmosphere.

The air handling system100includes an exhaust gas recirculation (EGR) loop120, including an EGR conduit122connecting the intake system110and the exhaust system112, an EGR valve126for controlling the exhaust gas flow from the exhaust system112to the intake system110, and a cooler124for cooling an intake manifold temperature. It is contemplated that in certain embodiments the cooler124may not be present.

The air handling system100further includes a turbocharger130, such as a fixed geometry turbocharger including a wastegate or a variable geometry turbocharger (VGT), for example, operable to compress ambient air before the ambient air enters the intake manifold104of the engine102at increased pressure. The turbocharger130includes a shaft132connecting a turbine134connected to the exhaust system112and a compressor154connected to the intake system110. The mixture of air from the compressor136and the exhaust gas from the EGR loop120is pumped through the intake system110, to the intake manifold104, and into the engine cylinders108, typically producing torque on a crankshaft (not shown). The air handling system100further includes a charge after cooler (CAC)138, operable to cool the charge flow provided to intake manifold104. The air handling system100may also include various components not shown for connecting exhaust system112to intake system110.

It shall be appreciated that the air handling system100is but one non-limiting illustrative embodiment of an air handling system to which the principles and techniques disclosed herein may be applied. A variety of alternate air handling system configurations and components may be utilized including, for example, air-handling systems with and without turbochargers or other types of superchargers. Exemplary forced induction systems may include one or more variable geometry turbochargers (VGTs), fixed geometry turbochargers, wastegated turbochargers, twin-turbochargers, series or parallel configurations of multiple turbochargers, symmetric or asymmetric combinations of turbochargers, and/or superchargers.

It shall be further appreciated that exemplary air handling systems may include charge air coolers with or without charge air cooler bypass valves, intake throttle valves, exhaust throttle valves, EGR valves, compressor bypass valves and/or as other types of air-handling actuators. A variety of EGR systems and configurations may be utilized including, for example, low pressure loop EGR, high pressure loop EGR, direct EGR, and/or EGR dedicated to one or more cylinders. Certain embodiments may include EGR loops with hot side EGR valves or cold side EGR valves. Certain embodiments may comprise systems including EGR bypass valves. Some embodiments may comprise non-EGR systems which omit EGR structure and functionality.

In the illustrated embodiment, the air handling system100includes a mass air flow (MAF) sensor142, an ambient air temperature sensor144, an ambient air pressure sensor146, and an intake pressure sensor148, each in fluid communication with the intake system110. The air handling system100further includes an intake manifold pressure (IMAP) sensor150in fluid communication with the intake manifold104. The intake system110and intake manifold104sensors need not be in direct communication with the intake system110or the intake manifold104and can be located at any position within the intake system110or the intake manifold104that provides a suitable indication of applicable intake system110and intake manifold106readings.

In one embodiment, the IMAP sensor150, operative to sense the air pressure in the intake manifold104, and the MAF sensor142, operative to sense the flowrate of air entering the engine102, can be utilized to calculate an EGR fraction. The EGR fraction provides an indication of the amount of EGR flow being supplied to the intake manifold104relative to the fresh air flow. However, any suitable method for determining the EGR fraction is contemplated.

The air handling system100further includes an oxygen sensor154and NOx sensor156in fluid communication with the exhaust system112, and an exhaust manifold pressure sensor152in fluid communication with the exhaust manifold106. The oxygen sensor154is operable to provide a measurement of the level or amount of oxygen in the exhaust gas from engine102. The oxygen sensor154may be a true oxygen sensor, lambda sensor, or any type of sensor from which the oxygen level in the exhaust gas can be determined. The NOx sensor156is operable to provide a measurement of the amount or level of NOx in the exhaust gas from engine102. Each of the oxygen sensor154, the NOx sensor156, and the exhaust manifold pressure sensor152need not be in direct communication with the exhaust system112or exhaust manifold106, and can be located at any position within the exhaust system112or exhaust manifold106that provides a suitable indication of applicable exhaust system112or exhaust manifold106readings. In certain embodiments, the oxygen sensor154and NOx sensor156may be located upstream and/or downstream of an aftertreatment system (not shown) for NOx reduction. It is contemplated that in certain embodiments the NOxsensor156may additionally provide for oxygen detection.

It shall be appreciated that the foregoing sensors and sensor arrangements are but several non-limiting, illustrative embodiments of sensors and sensor systems to which the principles and techniques disclosed herein may be applied. A variety of other types of sensors and sensor configurations may be utilized including, EGR flow sensors, boost pressure sensors, and/or exhaust temperature sensors to name but a few examples. It shall further be appreciated that the sensors which are utilized may be physical sensors, virtual sensors and/or combinations thereof.

The air handling system100includes a controller140structured to perform certain operations to receive and interpret signals from any component and sensor of the air handling system100. It shall be appreciated that the controller140, or control module, may be provided in a variety of forms and configurations including one or more computing devices forming a whole or part of a processing subsystem having non-transitory memory storing computer executable instructions, processing, and communication hardware. The controller140may be a single device or a distributed device, and the functions of the controller140may be performed by hardware or software. The controller140is in communication with any actuators, sensors, datalinks, computing devices, wireless connections, or other devices to be able to perform any described operations.

The controller140includes stored data values, constants, and functions, as well as operating instructions stored on computer readable medium. Any of the operations of exemplary procedures described herein may be performed at least partially by the controller. Other groupings that execute similar overall operations are understood within the scope of the present application. Modules may be implemented in hardware and/or software on one or more computer readable media, and modules may be distributed across various hardware or software components. More specific descriptions of certain embodiments of controller operations are discussed herein in connection withFIG. 2. Operations illustrated are understood to be exemplary only, and operations may be combined or divided, and added or removed, as well as re-ordered in whole or in part.

Certain operations described herein include operations to interpret one or more parameters. Interpreting, as utilized herein, includes receiving values by any method, including at least receiving values from a datalink or network communication, receiving an electronic signal (e.g., a voltage, frequency, current, or pulse-width modulation (PWM) signal) indicative of the value, receiving a software parameter indicative of the value, reading the value from a memory location on a computer readable medium, receiving the value as a run-time parameter by any means known in the art, and/or by receiving a value by which the interpreted parameter can be calculated, and/or by referencing a default value that is interpreted to be the parameter value.

The controller140is operatively coupled with and structured to store instructions in memory which are readable and executable by the controller140to operate air and fuel handling control valves, such as the EGR control valve126, for example. Other controllable actuators may include, for example, an intake throttle, an exhaust throttle, an inlet to the turbocharger130, and a wastegate of the turbine134.

One example embodiment of controller140is shown inFIG. 2. The controller140includes a number of inputs representing received signals from various sensors associated with the air handling system100described inFIG. 1. In the illustrated embodiment, the controller140includes an engine speed input202, an engine out air-fuel ratio (AFR) input204, a charge air flow input206, an EGR flow input208, an EGR fraction input210, an oxygen level input212, a mass air flow input214, an ambient air temperature input216, an ambient air pressure input218, an engine out NOx input220, an intake manifold pressure input222, an exhaust manifold pressure input224, and a compressor flow rate input226. It is contemplated that controller140inputs can come from sensors, virtual or real, and/or be calculated and/or estimated based on, for example, other sensors and/or engine operating conditions. It is further contemplated that the inputs described herein are exemplary only, and certain embodiments may contain fewer, additional and/or alternative inputs.

The illustrated controller140includes a system condition module230, a model linearization module240, a real-time cost function module250, and an air handling system controls module260. Other controller140arrangements that functionally execute the operations of the controller140are contemplated in the present application.

The system condition module230is structured to receive and interpret inputs to the controller140. In an example embodiment, the system condition module230is further structured to determine operational state information based at least in part on the inputs received by the controller140, and provide at least a portion of the operational state information to the model linearization module240and the real-time cost function module250. The model linearization module240is structured to calculate a set of parameters for a linear time-varying model of the engine based on at least the portion of the operational state information received from system condition module230and a physical model of the engine over the space of operational states and controller140inputs. The model linearization module is further structured to provide the set of parameters to the real-time cost function module250.

The real-time cost function module250is structured to receive and interpret the operational state information from the system condition module230and the set of parameters from the model linearization module240. In an example embodiment, the real-time cost function module250is structured to run a cost function, tracking the set of parameters over a prediction horizon. The real-time cost function module250may determine a solution of the cost function in a number of manners including, for example minimizing the cost function, maximizing the cost function, determining incremental solutions, converging or iteratively approaching a minimization, a maximization or another value which is selected for convergence. It shall be appreciated that minimization and maximization need not be absolute and that values differing from the absolute theoretical or practical minimum or maximum of a given function may be utilized for minimization or maximization operations. The cost function may be minimized subject to the set of parameters from the linear model and at least one physical constraint of the engine. In certain embodiments, because the linear model may be reconfigurable as a function of the operational state information, the cost function may be minimized in real-time using fast quadratic programming methods, for example, while the engine is running, which could be continuous or at discrete points in time. It is contemplated that in certain embodiments the cost function may be maximized. The real-time cost function module250is further structured to provide one or more control commands to the air handling system controls module260.

The air handling system controls module260is structured to receive and interpret the control command(s) from the real-time cost function module250. In an example embodiment, the air handling system controls module260provides at least one of an air handling system control command262and an air handling system diagnostic command264over a control sampling period. It is contemplated that the air handling system control command262may include more than one command to manipulate one or more air handling actuators, including the EGR valve126, the turbocharger130, an exhaust valve, an intake valve, and/or any other air handling actuator that may be present in the air handling system. In an example embodiment, the air handling system control command262includes an EGR valve position command, a turbocharger geometry command, an exhaust valve position command, and an intake valve position command. It is contemplated that additional air handling system control command(s)262may be provided by the air handling system controls module260for manipulating air handling actuators not illustrated and/or described herein.

In certain embodiments, where the air handling system100is electrically connected an on-board diagnostic (OBD) output device (not shown), the air handling system diagnostic command264may be provided to the on-board diagnostic output device for displaying the results of a diagnostic test or a position of one or more of the air handling actuators. It should be appreciated that the OBD output device may be any suitable device for displaying a result of the OBD tests to a user, operator, service technician, or other party, and may include, but is not limited to, an indicator lamp, a gauge, a printer, a memory device, an audible alarm, a display device, and/or other suitable output device.

The schematic flow diagram inFIG. 3and related description which follows provides an illustrative embodiment of performing procedures for controlling engine emission variations. Operations illustrated are understood to be exemplary only, and operations may be combined or divided, and added or removed, as well as re-ordered in whole or part. Certain operations illustrated may be implemented by a computer executing a computer program provided on a non-transitory computer readable storage medium, where the computer program comprises instructions causing the computer to execute one or more of the operations, or to issue commands to other devices to execute one or more of the operations.

With reference toFIG. 3, there is illustrated a flow diagram of an example procedure300for controlling air handling actuators that may be implemented in controller140for example. Procedure300begins at operation302which may begin by interpreting a key-on event and/or by initiation by an operator or technician. Operation302may alternatively or additionally include interpreting a communication or other parameter indicating that operation of a sampling interval is going to restart procedure300upon completion of procedure300.

Procedure300continues from operation302to operation304, where control parameters of the air handling system are determined based on current operational states of the air handling system100and set points of the engine102are calculated. In certain embodiments, the set points may include a desired AFR and/or an EGR fraction ratio. It should be appreciated that the air handling system control parameters may be measured and/or calculated. From operation304, procedure300continues to operation306, where a linear model of the air path is obtained by linearizing a physical model of the engine102as a function of the operational states.

Procedure300continues to operation308, where a real-time calculation is performed to minimize a norm of error vector, by using a controls cost function, for example, between the control parameters and the set points based on the linear model over a finite prediction horizon subject to the linear model and physical constraints of the air handling system100. In certain embodiments, the real-time calculation may be performed using a quadratic cost functional in discrete mode utilizing the equation:

J=∑i=0P-1⁢⁢u⁡(k+i)-ud⁡(k)Riu2+Δ⁢⁢u⁡(k+i)RiΔ⁢⁢u2+y⁡(k+i+1)-yd⁡(k+i+1)Qiy2Equation⁢⁢1
wherein P is the size of the prediction window, i is the sample time, k is the current sample time, u is the actuator commands, Δu is the change in the actuator commands, R is the weight factor for using actuators, udis the set-points for the actuator commands, y is the tracking measured outputs of air handling system, ydis the desired set-point for the air handling system outputs, and Q is the weight factor for the output tracking errors from the corresponding set-points.

From operation308, procedure300continues to operation310, where actuator positions to set the position of the air handling system actuators are determined based on the calculation results from operation308. The position of air handling system actuators may be set to regulate the AFR and the EGR fraction, for example.

Procedure300continues from operation310to operation312, where actuator position commands to set the position of the air handling system actuators are determined based on the air handling system actuator positions determined in operation308. In certain embodiments, the actuator position commands are implemented over a control sampling period of time in the framework of a model predictive control. In certain embodiments, the actuator position commands may include an exhaust valve position command, an intake valve position command, a turbocharger geometry command, and EGR valve position command. From operation312, procedure300continues to operation314, where procedure300ends. It is contemplated that in certain embodiments procedure300will be automatically repeated (i.e. restarts at operation302) at a next control sampling time when procedure300ends.

One example according to the foregoing approach comprises implementing controls for an air-handling system including an exhaust gas recirculation (EGR) valve, variable geometry turbocharger (VGT) system, and intake air throttle (IAT). Respective actuators for these three system components are utilized to control EGR flow and Charge flow at multiple operating conditions and in transients. Controls for this system may be developed using the following steps. First, it is determined that that EGR flow and charge flow are the key variables to control for attaining system level objectives and that the three actuators are needed at different conditions. Second, data is then gathered empirically to help linearize the engine system at different operating conditions (speed and fueling). Third, a cost function is defined, for example, J=min (tracking error of EGR flow, Charge flow and movement of actuators). Fourth, based on the optimization function, the actuator commands are computed which also respects the physical constraints like peak cylinder pressure, turbo speed and, turbine inlet temperature. Fifth, the controller then sends commands to the actuators to move. The implementation is based on the rate of sampling time that is needed for the controller action. For example, every 20 ms a command would be sent to the actuators based on the calculations made over past 40 ms of time.

Various aspects of the systems, apparatus, and methods are disclosed herein. For example, one aspect involves a method that includes operating a system including an internal combustion engine and an air handling system, the air handling system including an exhaust system and an intake system, the intake system including a turbocharger structured to provide charge air to the internal combustion engine, determining a first set of parameters based on a set of operational states of the system, computing a second set of parameters based on a linear time varying model of the system as a function of the first set of parameters, computing one or more control commands based upon a minimization or maximization or other solution of a cost function over a prediction horizon, the second set of parameters, and at least one physical constraint of the internal combustion engine, and controlling one or more operations of the system based at least in part upon the one or more control commands. The acts of determining the first and second set of parameters and computing the one or more control commands are repeated over a plurality of time periods over which the first set of parameters and the second set of parameters are time variant.

In one embodiment of the method, determining the first set of parameters comprises at least one of measuring an operating condition of the system and estimating an operating condition of the system. In another embodiment, the set of operational states includes at least one of an air to fuel ratio, a mass air flow, an ambient air pressure, an EGR mass flow rate, a compressor mass flow rate, a turbine mass flow rate, a charge flow, an EGR fraction, an exhaust manifold pressure, an intake manifold temperature, and an intake manifold pressure.

In another embodiment, the act of controlling operation of the system comprises controlling the air handling system. In one refinement of the embodiment, the intake system further includes an EGR loop and an EGR valve structured to control exhaust flow through the EGR loop, and wherein controlling the air handling system includes controlling at least one of an EGR valve, a turbocharger valve, an exhaust valve, and an intake valve. In another refinement, the turbocharger is a variable geometry turbocharger and the intake system includes an EGR loop and an EGR valve structured to control exhaust flow through the EGR loop, wherein the determining comprises determining an air-fuel ratio and an EGR fraction, and wherein the controlling comprises controlling the EGR valve and/or controlling the geometry of the turbocharger.

In still another embodiment, the second set of parameters varying over time as a function of first set of parameters. In yet another embodiment, the act of second computing a control command comprises one of minimizing the norm of an error vector between predicted outputs and operating set points subject to physical constraints of the internal combustion engine, and computing a solution to a linear quadratic programming problem, computing a solution to a continuous optimization problem, or computing a solution to a combinatorial optimization problem.

Another aspect includes a system, including an internal combustion engine, an air handling system including an exhaust system and an intake system, the intake system including a turbocharger structured to provide charge air to the internal combustion engine, and a controller operatively coupled with the air handling system and the internal combustion engine. The controller is structured to perform the following operations during operation of the engine: determine operational state information of the air handling system, determine a set of parameters of a linear time varying model of the air handling system as a function of the operational state information, determine a control command based upon a minimization or maximization or other solution of a cost function over a prediction horizon, the computed set of parameters, and at least one physical constraint of the internal combustion engine, and control operation of the air handling system based at least in part upon the control command.

In one embodiment of the system, the controller is further structured to determine the control command over a control sampling period. In one refinement of the embodiment, the controller is further structured to repeat determining the control command over a plurality of control sampling periods over which the operational state information is determined and the set of parameters is determined over the prediction horizon. In a further refinement, controlling the intake system includes controlling at least one of an EGR valve, a turbocharger, an exhaust valve, and an intake valve. In still a further refinement, the intake system further includes an EGR loop and an EGR valve structured to control exhaust flow through the EGR loop, and wherein controlling the intake system further includes controlling an EGR valve.

In another embodiment of the system, the turbocharger is a variable geometry turbocharger and the intake system includes an EGR loop and an EGR valve structured to control exhaust flow through the EGR loop, wherein the set of parameters includes an air-fuel ratio and an EGR fraction, and wherein the controller is further structured to control the EGR valve and/or controlling the geometry of the turbocharger. In still another embodiment, the act of determining the control command comprises minimizing the norm of an error vector between predicted outputs and operating set points subject to physical constraints of the internal combustion engine. In yet another embodiment, the act of determining the control command comprises computing a solution to a linear quadratic programming problem, computing a solution to a continuous optimization problem, or computing a solution to a combinatorial optimization problem.

Still another aspect includes an apparatus, including an electronic controller in operative communication with a plurality of sensors operable to provide signals indicating conditions of a system, the system including an engine and an air handling system operationally coupled to the engine, the air handling system including an exhaust system and an intake system each operationally coupled to the engine, the intake system including a turbocharger structured to provide charge air to the internal combustion engine. The electronic controller includes: a real-time system condition module structured to determine operational state information of the system based upon the signals provided by the plurality of sensors, a real-time model computation module structured to compute a set of parameters of a linear time varying model of the system, the set of parameters varying over time as a function of the operational state information, a real-time cost function module structured to compute a control command in real-time based upon a minimization or maximization or other solution of a cost function over a prediction horizon, the computed set of parameters, and at least one physical constraint of the engine, and an air handling system controls module structured to provide at least one of an air handling system control command and an air handling system diagnostic command based on the control command.

In one embodiment of the apparatus, the at least one of the air handling system control command and the air handling system diagnostic command comprises at least one of the commands selected from the commands consisting of: an exhaust valve position command; an intake valve position command; and a turbocharger geometry command. In a refinement of the embodiment, the exhaust system includes an exhaust gas recirculation (EGR) loop including an EGR valve, wherein the at least one of the air handling system control command and the air handling system diagnostic command further comprises an EGR valve position command. In a further refinement, the set of parameters includes an air-fuel ratio and an EGR fraction.

In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary.