Abstract:
Methods and systems for controlling a diesel engine using a combined fuel and air-side controller are disclosed. An illustrative method may include the steps of providing a combined fuel and air-side controller adapted to coordinate both the fuel and air-side control of an engine, sensing one or more parameters, and outputting a fuel profile signal and one or more air-side control signals for controlling at least a part of the fuel-side and at least a part of the air-side of the engine. By centrally coordinating both the fuel and air-side control of the engine, the system can be configured to anticipate future fuel and/or air-side needs of the engine, thus improving system response, performance, and/or emissions.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application is a continuation-in-part of U.S. patent application Ser. No. 11/024,531 entitled “Multivariable Control For An Engine”, U.S. patent application Ser. No. 11/025,221, entitled “Pedal Position And/Or Pedal Change Rate For Use In Control Of An Engine” and U.S. patent application Ser. No. 11/025,563 now U.S. Pat. No. 7,165,399 entitled “Method And System For Using A Measure Of Fueling Rate In The Air Side Control Of An Engine”, all filed on Dec. 29, 2004. 

   FIELD 
   The present invention relates generally to engines and engine control. More specifically, the present invention pertains to methods for controlling the flow of fuel and air in engines. 
   BACKGROUND 
   Spark ignition engines typically have a gas pedal that is mechanically connected to an air throttle that meters air into the engine. Stepping on the gas pedal typically results in opening an air throttle, which allows more air into the engine. In some cases, a fuel injector controller adjusts the fuel that is provided to the engine to maintain a desired air/fuel ratio (AFR). The AFR is usually held close to a stoichiometric ratio (e.g. 14.6:1) to produce stoichiometric combustion, which helps minimize engine emissions and allows three-way catalysts to simultaneously remove hydrocarbons, carbon monoxide, and oxides of nitrogen (NO X ). 
   In contrast, compression ignition engines such as diesel engines do not usually operate at stoichiometric ratios, and thus typically result in greater emissions with different emission components. Because of recent increases in the use of diesel engines in the automotive and light truck markets, federal regulations have been passed requiring more stringent emission levels for diesel engines. Such regulations have prompted automakers to consider alternative methods for improving engine efficiency and reducing emissions. 
   Unlike spark ignition engines, the fuel pedal of a diesel engine is typically not directly connected to an air throttle that meters air into the engine. Instead, in those diesel engines equipped with electronic fuel injection (EFI), pedal position is often sensed by a pedal position sensor that senses pedal position and adjusts the fuel rate provided to the engine, allowing more or less fuel per fuel pump shot to be provided to the engine. In many modern diesel engines, the air to the engine is controlled by a turbocharger such as a Variable Nozzle Turbocharger (VNT) or waste-gate turbocharger. Typically, there is a time delay or “turbo lag” between when the operator engages the fuel pedal to inject more fuel and when the turbocharger spins-up to provide the additional air required to produce the desired AFR. This “turbo-lag” can reduce the responsiveness and performance of the engine, and can increase the amount of emissions discharged from the engine. 
   There are typically no sensors in the exhaust stream of a diesel engine that are analogous to those emissions sensors found in spark ignition engines. One reason for their absence is that diesel engines generally operate at about twice as lean as spark ignition engines. As such, the oxygen level in the exhaust of a diesel engine can be at a level where standard oxygen emission sensors do not provide useful information. At the same time, diesel engines typically burn too lean for conventional three-way catalysts. As a result, control over combustion in a diesel engine is typically performed in an “open-loop” manner, often relying on engine maps or the like to generate set points for the intake manifold parameters that are believed to be favorable for acceptable exhaust emissions. 
   SUMMARY 
   The present invention relates to methods for controlling the flow of both fuel and air in engines. An illustrative method in accordance with an exemplary embodiment of the present invention may include the steps of providing a combined fuel and air-side controller adapted to coordinate both the fuel-side and air-side control of an engine, sensing one or more parameters of the system, and outputting a fuel profile signal and one or more air-side control signals for controlling at least a part of the fuel-side and at least a part of the air-side of the engine. A number of sensors including a MAP sensor, MAF sensor, NO X  sensor and/or particulate matter (PM) emissions sensor can be provided for sensing one or more of the parameters of the engine. One or more actuators can be further provided for controlling at least part of the operation of the engine based on the control signals received from the controller as well as other system components. In certain embodiments, the controller may be a multivariable Model Predictive Controller (MPC), which can be configured to compute one or more fuel and/or air-side parameters using a central optimization algorithm or routine. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  is a schematic view of an illustrative diesel engine system in accordance with an exemplary embodiment of the present invention; 
       FIG. 2  is a schematic view of an illustrative combined fuel and air-side controller for use with the illustrative diesel engine system of  FIG. 1 ; 
       FIG. 3  is a schematic view of an illustrative combined fuel and air-side controller in accordance with another exemplary embodiment of the present invention; 
       FIG. 4  is a schematic view of an illustrative model predictive controller in accordance with an exemplary embodiment of the present invention; 
       FIG. 5  is a schematic view of another illustrative diesel engine system in accordance with an exemplary embodiment of the present invention employing a combined fuel and air-side controller; 
       FIG. 6  is a schematic view of another illustrative diesel engine system in accordance with an exemplary embodiment of the present invention employing a combined fuel and air-side controller; and 
       FIG. 7  is a schematic view of another illustrative diesel engine system in accordance with an exemplary embodiment of the present invention employing a combined fuel and air-side controller. 
   

   DETAILED DESCRIPTION 
   The following description should be read with reference to the drawings, in which like elements in different drawings are numbered in like fashion. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. Although examples of construction, dimensions, and materials are illustrated for the various elements, those skilled in the art will recognize that many of the examples provided have suitable alternatives that may be utilized. 
     FIG. 1  is a schematic view of an illustrative diesel engine system in accordance with an exemplary embodiment of the present invention. The illustrative diesel engine system is generally shown at  10 , and includes a diesel engine  20  having an intake manifold  22  and an exhaust manifold  24 . In the illustrative embodiment, a fuel injector  26  provides fuel to the engine  20 . The fuel injector  26  may include a single fuel injector, but more commonly may include a number of fuel injectors that are independently controllable. The fuel injector  26  can be configured to provide a desired fuel profile to the engine  20  based on a fuel profile set  28  as well as one or more other signals  30  relating to the fuel and/or air-side control of the engine  20 . The term fuel “profile”, as used herein, may include any number of fuel parameters or characteristics including, for example, fuel delivery rate, change in fuel delivery rate, fuel timing, fuel pre-injection event(s), fuel post-injection event(s), fuel pulses, and/or any other fuel delivery characteristic, as desired. One or more fuel side actuators may be used to control these and other fuel parameters, as desired. 
   As can be further seen in  FIG. 1 , exhaust from the engine  20  is provided to the exhaust manifold  24 , which delivers the exhaust gas down an exhaust pipe  32 . In the illustrative embodiment, a turbocharger  34  is further provided downstream of the exhaust manifold  24 . The illustrative turbocharger  34  may include a turbine  36 , which is driven by the exhaust gas flow. In the illustrative embodiment, the rotating turbine  36  drives a compressor  38  via a mechanical coupling  40 . The compressor  38  receives ambient air through passageway  42 , compresses the ambient air, and then provides compressed air to the intake manifold  22 , as shown. 
   The turbocharger  34  may be a variable nozzle turbine (VNT) turbocharger. However, it is contemplated that any suitable turbocharger may be used, including, for example, a waste gated turbocharger or a variable geometry inlet nozzle turbocharger (VGT) with an actuator to operate the waste gate or VGT vane set. The illustrative VNT turbocharger uses adjustable vanes inside an exhaust scroll to change the angle of attack of the incoming exhaust gasses as they strike the exhaust turbine  36 . In the illustrative embodiment, the angle of attack of the vanes, and thus the amount of boost pressure (MAP) provided by the compressor  38 , may be controlled by a VNT SET signal  44 . In some cases, a VNT POS signal  46  can be provided to indicate the current vane position. A TURBO SPEED signal  48  may also be provided to indicate the current turbine speed, which in some cases can be utilized to limit the turbo speed to help prevent damage to the turbine  36 . 
   To reduce turbo lag, the turbine  36  may include an electrical motor assist (not explicitly shown). Although not required in all embodiments, the electric motor assist may help increase the speed of the turbine  36  and thus the boost pressure provided by the compressor  38  to the intake manifold  22 . This may be particularly useful when the engine  20  is at low engine speeds and when higher boost pressure is desired, such as under high acceleration conditions. Under these conditions, the exhaust gas flow may be insufficient to generate the desired boost pressure (MAP) at the intake manifold  22 . In some embodiments, an ETURBO SET signal  50  may be provided to control the amount of electric motor assist that is provided. 
   The compressor  38  may comprise either a variable or non-variable compressor. In certain cases, for example, the compressed air that is provided by the compressor  38  may be only a function of the speed at which the turbine  36  rotates the compressor  38 . In other cases, the compressor  38  may be a variable geometry compressor (VGC), wherein a VGC SET signal  52  can be used to set the vane position at the outlet of the compressor  38  to provide a controlled amount of compressed air to the intake manifold  22 , as desired. 
   A compressed air cooler  54  may be provided to help cool the compressed air before it is provided to the intake manifold  22 . In some embodiments, one or more compressed air COMP. COOLER SET signals  56  may be provided to the compressed air cooler  54  to help control the temperature of the compressed air that is ultimately provided to the intake manifold  22 . In some cases, the one or more COMP. COOLER SET signals  56  may be provided by a combined fuel and air-side controller (see  FIGS. 2 and 3 ), if desired. 
   In certain embodiments, and to reduce the emissions of some diesel engines, an Exhaust Gas Recirculation (EGR) valve  58  may be inserted between the exhaust manifold  24  and the intake manifold  22 , as shown. In the illustrative embodiment, the EGR valve  58  accepts an EGR SET signal  60 , which is used to set the desired amount of exhaust gas recirculation (EGR). An EGR POS signal  62  indicating the current position of the EGR valve  58  may also be provided, if desired. 
   In some cases, an EGR cooler  64  may be provided either upstream or downstream of the EGR valve  58  to help cool the exhaust gas before it is provided to the intake manifold  22 . In some embodiments, one or more EGR COOLER SET signals  66  may be provided to the EGR cooler  64  to help control the temperature of the recirculated exhaust gas. In some cases, the one or more EGR COOLER SET signals  66  may be provided by a combined fuel and air-side controller (see  FIGS. 2 ), if desired. 
   A number of sensors may be provided for monitoring the operation of the engine  20 . For example, an intake manifold air flow (MAF) sensor  68  may provide a measure of the intake manifold air flow (MAF). An intake manifold air pressure (MAP) sensor  70 , in turn, may provide a measure of the intake manifold air pressure (MAP). A manifold air temperature (MAT) sensor  72  may provide a measure of the intake manifold air temperature (MAT). A NO X  sensor  74  may provide a measure of the NO X  concentration in the exhaust gas. Similarly, a Particular Matter (PM) sensor  76  may provide a measure of the particulate matter concentration in the exhaust gas. While the NO X  sensor  74  and PM sensor  76  are shown located at the exhaust manifold  24 , it is contemplated that these sensors may be provided anywhere downstream of the engine  20 , as desired. In addition, the sensors shown in  FIG. 1  are only illustrative, and it is contemplated that more or less sensors may be provided, as desired. 
     FIG. 2  is a schematic view of an illustrative combined fuel and air-side controller  84  for use with the illustrative diesel engine system  10  of  FIG. 1 . As can be seen in  FIG. 2 , the controller  84  can be configured to receive a number of input parameters  86  that can be utilized to provide both fuel and air-side control of the engine  20 . The controller  84  can be configured to output one or more fuel-side signals  88  that can be utilized to control various fuel actuators and/or fuel parameters for controlling the fuel profile delivered to the engine  20  via the fuel injector(s)  26 . In addition, the controller  84  can be configured to output one or more air-side signals  90  for controlling the intake manifold  22 , exhaust manifold  24 , turbocharger  34 , compressor cooler  54 , EGR valve  58 , and/or other air-side engine components. In certain embodiments, the controller  84  can be further configured to output a number of other engine signals  92  that can be used to control various other functions of the engine system  10  such as the transmission, engine coolant system, cruise control system, etc. 
   Turning now to  FIG. 3 , a specific embodiment of the illustrative controller  84  of  FIG. 2  will now be described. As can be seen in  FIG. 3 , the controller  84  can be configured to receive various input signals relating to the fuel-side control of the engine  20 , including, for example, a PEDAL POSITION signal  94 , the MAF signal  68 , an ENGINE SPEED signal  98 , and/or the AFR LOW LIMIT signal  100 , each of which can be provided as a part of the fuel profile set  28  depicted in  FIG. 1 . In addition, the controller  84  can be configured to receive various other input signals relating to the air-side control of the engine  20 , including, for example, the MAP signal  70 , the MAT signal  72 , the TURBO SPEED signal  48 , the NO X  signal  74 , and/or the PM signal  76 , as shown in  FIG. 1 . While the illustrative embodiment of  FIG. 3  shows the use of several engine parameters for the coordinated control of both the fuel and air-sides of the engine  20 , it should be understood that the controller  84  could be configured to control only one side (e.g. the fuel side) of the engine  20 , if desired. Moreover, the controller  84  can be configured to receive and output other parameters and/or signals, depending on the particular application. In some embodiments, for example, the controller  84  can be configured to receive various state and actuator constraints  102 , if desired. 
   Based on the values of the input parameters  86  received, the controller  84  may provide a number of control outputs to help provide fuel and/or air-side control to the engine  20 . In certain embodiments, and as further shown in  FIG. 3 , for example, the controller  84  can be configured to output a FUEL PROFILE signal  104  that can be utilized to adjust the various fuel parameters of the fuel injection system including, for example, the fuel delivery rate, the change in fuel delivery rate, the fuel timing, any fuel pre-injection event(s), any fuel post-injection event(s), the fuel pulse on/off time, and/or other such fuel delivery characteristic, as desired. 
   As can be further seen in  FIG. 3 , the controller  84  can be further configured to output other parameters for the air-side control of the engine  20 , including, for example, the VNT SET signal  44 , the VGC SET signal  52 , the EGR SET signal  60 , and in some cases, the ETURBO SET signal  50 , the COMP. COOLER SET signal  56 , and the EGR COOLER SET signal  66 , each of which can be seen in  FIG. 1 . Other output signals and/or parameters are possible, however, depending on the application. 
   In some embodiments, the controller  84  may comprise a multivariable Model Predictive Controller (MPC). The MPC may include a model of the dynamic process of engine operation, and may provide predictive control signals to the engine  20  subject to constraints in control variables and measured output variables. The models may be static and/or dynamic, depending on the application. In some cases, the models may produce one or more output signals y(t) from one or more input signals u(t). A dynamic model typically contains a static model plus information about the time response of the system. Thus, a dynamic model is often of higher fidelity than a static model. 
   In mathematical terms, a linear dynamic model has the form:
 
 y ( t )= B   0   *u ( t )+ B   1   *u ( t− 1)+ . . . + B   n   *u ( t−n )+ A   1   *y ( t− 1)+ . . . + A   m   *y ( t−m )  (1)
 
wherein B 0  . . . B n  and A 1  . . . A m  are constant matrices.
 
   In a dynamic model, y(t) represents the output at time t, and is based on the current input u(t), one or more past inputs u(t−1), . . . , u(t−n), and one or more past outputs y(t−1) . . . y(t−m). A static model, in turn, is a special case where the matrices B 1 = . . . =B n =0, and A 1 = . . . =A m =0, which can be expressed by the simpler relationship:
 
 y ( t )= B   0   *u ( t )  (2)
 
wherein B 0  is a simple matrix multiplier. Since a static model does not have a “memory” of either the past inputs u(t−1) . . . u(t−n) or the past outputs y(t−1) . . . y(t−m), such model tends to be simpler, but may be less powerful in modeling some dynamic system parameters.
 
   For turbocharged diesel engine systems, the system dynamics can be relatively complicated and several of the interactions may have characteristics known as “non-minimum phase”. Non minimum phase is a dynamic response where the output y(t), when exposed to a step in input u(t) will initially move in one direction, and then turn around and move towards its steady state in the opposite direction. The soot emission in a diesel engine is one example of such phenomenon. In some cases, these dynamics may be important for optimal operation of the control system. Thus, dynamic models are often preferred, at least when modeling some control parameters. 
   In one example, the MPC may include a multivariable model that models the effect of changes in one or more actuators of the engine (e.g. VNT SET  44 , EGR SET  60 , COMP. COOLER SET  56 , EGR COOLER SET  66 , ETURBO SET  50 , fueling rate, etc.) on each of two or more input parameters (e.g. AFR LOW LIMIT  100 , MAP  70 , MAF  72 , NO X    74 , PM  76 , etc.), and then controls the actuators to produce a desired response in at least one of the two or more parameters. Likewise, the model may, in some cases, model the effects of simultaneous changes in two or more actuators on each of one or more engine parameters, and then control at least one of the actuators to produce a desired response in each of the one or more input parameters. 
   In one illustrative embodiment, for example, a state-space model of a discrete time dynamical system may be represented using equations of the form:
 
 x ( t+ 1)= Ax ( t )+ Bu ( t )
 
 y ( t )= Cx ( t )
 
The model predictive algorithm involves solving the problem:
 
 u ( k )=arg min{ J }, where the function  J  is given by:
 
           J   =         x   ^     ⁡     (     t   +       N   y     ⁢          t   )     T     ⁢   P   ⁢       x   ^     (     t   +     N   y            ⁢   t       )       +       ∑     k   =   0         N   y     -   1       ⁢     [         x   ^     ⁡     (     t   +     k   ⁢          t   )     T     ⁢   Q   ⁢       x   ^     (     t   +   k          ⁢   t       )       +         u   ⁡     (     t   +   k     )       T     ⁢     Ru   ⁡     (     t   +   k     )           ]               
Subject to Constraints
   y   min   ≦ŷ ( t+k|t )≦ y   max     u   min   ≦u ( t+k )≦ u   max     x ( t|t )= x ( t )   {circumflex over (x)} ( t+k+ 1| t )= A{circumflex over (x)} ( t+k|t )+ Bu ( t+k )   ŷ ( t+k|t )= C{circumflex over (x)} ( t+k|t ) 
In some embodiments, this is transformed into a Quadratic Programming (QP) problem and solved with standard or customized tools.
 
   The variable “y(k)” contains the sensor measurements (for the turbocharger problem, these include but are not limited to MAF  68 , MAP  70 , MAT  72 , TURBO SPEED  48 , NO X    74 , PM  76 , etc). The variables ŷ(k+t|t) denote the outputs of the system predicted at time “t+k” when the measurements “y(t)” are available. They are used in the model predictive controller to choose the sequence of inputs that yields the “best” (according to performance index J) predicted sequence of outputs. 
   The variables “u(k)” are produced by optimizing J and, in some cases, are used for the actuator set points. For the turbocharger problem these include, but are not limited to, VNT SET  44 , EGR SET  60 , COMP. COOLER SET  56 , EGR COOLER SET  66 , ETURBO SET  50 , etc. The variable “x(k)” is a variable representing an internal state of the dynamical state space model of the system. The variable {circumflex over (x)}(t+k|t) indicates the predicted version of the state variable k discrete time steps into the future and is used in the MPC to optimize the future values of the system. 
   The variables y min  and y max  are constraints and indicate, respectively, the minimum and maximum values that the system predicted measurements ŷ(k) are permitted to attain. These often correspond to hard limits on the closed-loop behavior in the control system. For example, a hard limit may be placed on the PM emissions such that they are not permitted to exceed a certain number of grams per second at some given time. In some cases, only a minimum y min  or maximum y max  constraint is provided. For example, a maximum PM emission constraint may be provided, while a minimum PM emission constraint may be unnecessary or undesirable. 
   The variables u min  and u max  are also constraints, and indicate the minimum and maximum values that the system actuators û(k) are permitted to attain, often corresponding to physical limitations on the actuators. For example, the EGR valve  58  may have a minimum of zero corresponding to a fully closed valve position and a maximum value of one corresponding to the fully open valve position. Like above, and in some embodiments, only a minimum u min  or maximum u max  constraint may be provided, depending on the circumstances. Also, some or all of the constraints (e.g. y min , y max , u min , u max ) may vary in time, depending on the current operating conditions. The state and actuator constraints may be provided to the controller  84  of  FIGS. 2-3  via interface  102 , if desired. 
   The constant matrices P, Q, R are often positive definite matrices used to set a penalty on the optimization of the respective variables. These are used in practice to “tune” the closed-loop response of the system. 
     FIG. 4  is a schematic view of an illustrative model predictive controller in accordance with an exemplary embodiment of the present invention. As shown in  FIG. 4 , the MPC  84  may include a State Observer  106  and a MPC Controller  108 . As described above, the MPC Controller  108  provides a number of control outputs “u” to actuators or the like of the engine  20 . Illustrative control outputs include, for example, the FUEL PROFILE signal  104 , the VNT SET signal  44 , the VGC set signal  52 , the EGR SET signal  60 , the ETURBO SET signal  50 , the COMP. COOLER SET signal  56 , and the EGR COOLER SET signal  66 , all shown and described above with respect to  FIGS. 1 and 3 . The MPC Controller  108  may include a memory for storing past values of the control outputs u(t), u(t−1), u(t−2), etc. 
   The State Observer  106  receives a number of inputs “y”, a number of control outputs “u”, and a number of internal variables “x”. Illustrative inputs “y” may include, for example, the PEDAL POSITION signal  94 , the MAF signal  68 , the ENGINE SPEED signal  98 , the AFR LOW LIMIT signal  100 , the MAP signal  70 , the MAT signal  72 , the TURBO SPEED signal  48 , the NO X  signal  74 , and/or the PM signal  76 , as shown and described above with respect to  FIGS. 1 and 3 . It is contemplated that the inputs “y” may be interrogated constantly, intermittently, or periodically, or at any other time, as desired. Also, these input parameters are only illustrative, and it is contemplated that more or less input signals may be provided, depending on the application. In some cases, the State Observer  106  may receive present and/or past values for each of the number of inputs “y”, the number of control outputs “u”, and a number of internal state variables “x”, depending on the application. 
   The State Observer  106  produces a current set of state variables “x”, which are then provided to the MPC Controller  108 . The MPC Controller  108  then calculates new control outputs “u”, which are presented to actuators or the like on the engine  20 . The control outputs “u” may be updated constantly, intermittently, or periodically, or at any other time, as desired. The engine  20  operates using the new control outputs “u”, and produces new inputs “y” accordingly. 
   In one illustrative embodiment, the MPC  84  can be programmed using standard Quadratic Programming (QP) and/or Linear Programming (LP) techniques to predict values for the control outputs “u” so that the engine  20  produces inputs “y” that are at a desired target value, within a desired target range, and/or that do not violate any predefined constraints. For example, by knowing the impact of the VNT SET signal  44 , the EGR SET signal  60  and/or the ETURBO SET signal  50  on the NO X  and/or PM emissions, the MPC  84  may predict values for the control output VNT SET signal  44 , EGR SET signal  60  and/or the ETURBO SET signal  50  so that future values of the NO X    74  and/or PM emissions signals  76  are at or remain at a desired target value, within a desired target range, and/or do not violate current constraints. This prediction capability may be particularly useful since there is often a “turbo lag” (e.g. 1 second) from when a change in the VNT SET signal  44 , EGR SET signal  60  and/or the ETURBO SET signal  50  occurs and when the resulting change in the NO X  and/or PM emissions signals  74 , 76  occurs. In some cases, the constraints may change, and may depend on the current operating conditions. 
   It is contemplated that the MPC  84  may be implemented in the form of online optimization and/or by using equivalent lookup tables computed with a hybrid multi-parametric algorithm depending on the complexity of the problem. Hybrid multi-parametric algorithms may allow constraints on emission parameters as well as multiple system operating modes to be encoded into a lookup table that can be implemented in an Engine Control Unit (ECU) of a vehicle. The emission constraints can be time-varying signals, which enter the lookup table as additional parameters. Hybrid multi-parametric algorithms are further described by F. Borrelli in “ Constrained Optimal Control of Linear and Hybrid Systems ”, volume 290 of Lecture Notes in Control and Information Sciences, Springer, 2003, which is incorporated herein by reference. 
   Alternatively, or in addition, the MPC  84  may include one or more Proportional-Integral-Derivative (PID) control loops, one or more predictive constrained control loops (e.g. a Smith predictor control loop), one or more multiparametric control loops, one or more multivariable control loops, one or more dynamic matrix control loops, one or more statistical processes control loop, a knowledge based expert system, a neural network, fuzzy logic or any other suitable control mechanism, as desired. Also, it is contemplated that the MPC  84  may provide commands and/or set points for lower-level controllers that are used to control the actuators of the engine. In some cases, the lower level controllers may be, for example, single-input-single-output (SISO) controllers such as PID controllers. 
     FIG. 5  is a schematic view of another illustrative diesel engine system in accordance with an exemplary embodiment of the present invention employing a combined fuel and air-side controller. The illustrative diesel engine system, represented generally by reference number  110 , can include a diesel engine  112  coupled to a variable nozzle turbine (VNT) turbocharger with electric motor assist and an Exhaust Gas Recirculation (EGR) valve that is inserted between the engine exhaust manifold and the engine intake manifold. Alternatively, and in other embodiments, the diesel engine  112  can include other types of turbochargers along with the EGR valve, including, for example, a variable geometry inlet nozzle turbocharger (VGT) or waste-gate turbocharger, if desired. As with the illustrative embodiment of  FIG. 1 , the diesel engine system  110  may include other components such as a compressor cooler, EGR cooler, etc., as desired. 
   A number of sensor outputs can be provided for monitoring various parameters of the engine  112  during operation. In certain embodiments, for example, the illustrative sensor outputs of the engine  112  may include an ENGINE SPEED signal  114 , an intake MAF signal  116 , an intake MAP signal  118 , an intake MAT signal  120 , a TURBO SPEED signal  122 , a NO X  signal  124 , a PM signal  126 , and an ENGINE TEMPERATURE sense signal  128 , as shown. As with other embodiments herein, the number and/or type of engine sensor outputs provided may vary, depending on the application. 
   As can be further seen in  FIG. 5 , a combined fuel and air-side controller  130  can be coupled to the engine  112  and tasked to coordinate both the fuel and air-side control of the engine  112 , including the fuel profile  132  delivered to the engine  112  by the fuel injectors. In some embodiments, a PEDAL POSITION signal  134  and a STATE AND ACTUATOR CONSTRAINTS signal  136  can be used by the controller  130  to calculate the desired amount of fuel for the engine  112 . Other input signals such as that described above with respect to  FIG. 3  may also be inputted to the combined fuel and air-side controller  130 , if desired. In some cases, stepping on the pedal increases the fuel flow in a manner dictated by one or more static and/or dynamic control maps, as described herein. 
   By knowing the impact of fueling rate and/or a change in fueling rate on various engine parameters such as MAP, MAF, MAT, TURBO SPEED, NO X  emissions, PM emissions, etc., the controller  130  may adjust one or more control signals such as the VNT SET signal  138 , VGC SET signal  140 , EGR SET signal  142 , the ETURBO SET signal  144 , the COMP. COOLER SET signal  146  and/or the EGR COOLER SET signal  148  to cancel or mitigate disrupting effects on, for example, MAP, MAF, turbo speed, NO X  emissions, PM emissions, etc. In use, the control of these signals may help to improve the responsiveness, performance, and/or emissions of the engine. 
   In addition to controlling the fuel profile  132  delivered to the engine  112 , the illustrative controller  130  can be further configured to coordinate the air-side control of the engine  112 . The term “air-side control”, as used herein, may include both intake air and exhaust or emission control. In the illustrative embodiment of  FIG. 5 , for example, the controller  130  can be configured to receive input signals such as the MAF signal  116 , the MAP signal  118 , the MAT signal  120 , the TURBO SPEED signal  122 , the NO X  signal  124 , the PM signal  126 , and/or the ENGINE TEMPERATURE signal  128 . These input parameters are only illustrative, and it is contemplated that more or less input signals may be received, depending on the application. 
   Based on the value(s) of the current and/or past-received input parameters, the illustrative controller  130  may provide a number of control outputs to help provide fuel and/or air-side control to the engine  112 . In certain embodiments, for example, the controller  130  can provide a FUEL PROFILE signal  132 , a VNT SET signal  138 , a VGC SET signal  140 , an EGR SET signal  142 , an ETURBO SET signal  144 , a COMP. COOLER SET signal  146 , and an EGR COOLER SET signal  148 , as shown in  FIG. 5 . It should be understood, however, that other control outputs can be provided to the engine  112 , depending on the application. In some cases, the controller  130  may be similar to the controller  84  of  FIG. 3 . 
     FIG. 6  is a schematic view of another illustrative diesel engine system  150  in accordance with an exemplary embodiment of the present invention. Diesel engine system  150  is similar to that described above with respect to  FIG. 5 , with like elements in each drawing numbered in like fashion. In the illustrative embodiment of  FIG. 6 , however, the controller  130  can be further configured to receive a PEDAL RATE signal  152  and a BRAKE POSITION signal  154  that can be further used by the controller  130  to regulate the fuel and/or air-side control of the engine, if desired. 
   In some cases, the PEDAL RATE signal  152  can be utilized in conjunction with the PEDAL POSITION signal  134  to anticipate future fuel and/or air needs by determining the change in rate at which the fuel pedal is being engaged or disengaged. In similar fashion, the BRAKE POSITION signal  154  can be used to anticipate future fuel and/or air-side needs based, for example, on the pressure exerted on the brake by the driver, the brake rate, and/or the brake travel. Using such input signals  152 , 154 , the controller  130  may anticipate the future fuel and/or air needs of the engine, and may adjust the fuel profile and/or air profile to meet those anticipated needs. 
     FIG. 7  is a schematic view of another illustrative diesel engine system  156  in accordance with an exemplary embodiment of the present invention employing a combined fuel and air-side controller. In the illustrative embodiment of  FIG. 7 , a PEDAL POSITION signal  158  is shown provided to a fuel-side position and rate map  160  and an air-side position and rate map  162 , which can be dynamic maps, static maps, or combinations thereof. As indicated by the dashed box  164  in  FIG. 7 , the maps  160 , 162  can both be provided as a single (i.e. integral) map for controlling both the fuel and air-sides of the engine. It should be understood, however, that the maps  160 , 162  could be implemented separately, if desired. 
   In the illustrative embodiment, the fuel-side position and rate map  160  may translate the pedal position and/or pedal change rate (and in some cases, further derivatives of the pedal position) into one or more fuel-side set points  166 . The air-side position and rate map  162 , in turn, may translate the pedal position and/or pedal change rate (and in some cases, further derivates of the pedal position) into one or more air-side parameters  168 . In some embodiments, another air-side set point map  170  may receive a number of other engine parameters  172  such as a brake position parameter, a VNT position parameter, an outside air temperature parameter, an outside air pressure parameter, an engine temperature parameter, a humidity parameter and/or any other desired parameter, which may be provided to the set point map  170  as one or more air-side set points  174 . 
   A combined fuel and air-side controller  176  can be configured to receive one or more fuel and air-side set points and/or parameters from the fuel-side position and rate map  160 , the air-side position and rate map  162 , and, in some cases, the air-side set points  174  from the air-side set point map  170 . The combined fuel and air-side controller  176  can be further configured to receive various sensor signals from both the fuel and air-sides of the engine. In certain embodiments, for example, the combined fuel and air-side controller  176  can be configured to receive a number of fuel-side signals  178  such as ENGINE SPEED, MAF, etc., which can then be provided as a FUEL PROFILE signal  180  to one or more fuel-side actuators (e.g. fuel injectors) of the engine. 
   For air-side control of the engine, the combined fuel and air-side controller  176  can be configured to receive a number of air-side signals  182  such as MAF, MAP, MAT, NO X , PM, TURBO SPEED, VNT POS, EGR POS, etc., which in combination with the optional air-side set points  174  provided by the set point map  170 , can be provided as one or more air-side control signals  184  such as VNT SET, VGC SET, EGR SET, ETURBO SET, COMP. COOLER SET, EGR COOLER SET, etc., as desired. 
   In certain embodiments, the combined fuel and air-side controller  176  may be a multivariable Model Predictive Controller (MPC), which can be configured to compute all of the actuator signals using a central optimization algorithm or routine. As with other embodiments herein, the combined fuel and air-side controller  176  may be implemented in the form of online optimization and/or by using equivalent lookup tables computed with a hybrid multi-parametric algorithm depending on the complexity of the problem. Hybrid multi-parametric algorithms may allow constraints on emission parameters as well as multiple system operating modes to be encoded into a lookup table, which can be implemented in an Engine Control Unit (ECU) of a vehicle. The emission constraints can be time-varying signals that enter the lookup table as additional parameters. 
   Alternatively, or in addition, the combined fuel and air-side controller  176  may include one or more Proportional-Integral-Derivative (PID) control loops, one or more predictive constrained control loops (e.g. a Smith predictor control loop), one or more multiparametric control loops, one or more multivariable control loops, one or more dynamic matrix control loops, one or more statistical processes control loop, a knowledge based expert system, a neural network, fuzzy logic or any other suitable control mechanism, as desired. Also, it is contemplated that the combined fuel and air-side controller  176  may provide commands and/or set points for lower-level controllers that are used to control the actuators of the engine. In some cases, the lower level controllers may be, for example, single-input-single-output (SISO) controllers such as PID controllers. 
   Having thus described the several embodiments of the present invention, those of skill in the art will readily appreciate that other embodiments may be made and used which fall within the scope of the claims attached hereto. Numerous advantages of the invention covered by this document have been set forth in the foregoing description. It will be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size and arrangement of parts without exceeding the scope of the invention.