Method for controlling vehicle emissions

1. Field of the Invention

The present invention relates generally to systems and methods for determining non-sensed vehicle operating parameters.

2. Background Art

A vehicle system may include a controller configured to facilitate controlling and/or programming any number of vehicle sub-systems. These operations may require the controller to define operating set-points or other operating guidelines for the vehicle system based on current and/or desired operating conditions. Typically, hardware sensors may be included to report the current operating conditions to the controller. However, the hardware sensors generally incorporated within the vehicle system are expensive and may be prone to failure.

FIG. 1 illustrates a vehicle system in accordance with one non-limiting aspect of the present invention.

FIG. 2 illustrates the steady state look-up table in accordance with one non-limiting aspect of the present invention.

FIG. 3 illustrates the transient look-up table in accordance with one non-limiting aspect of the present invention.

FIG. 1 illustrates a vehicle system 10 configured to facilitate driving a vehicle (not shown) in accordance with one non-limiting aspect of the present invention. The system 10 may be configured to drive any number of vehicles, including but not limited to highway trucks, construction equipment, marine vehicles, stationary generators, automobiles, trucks, light and heavy-duty work vehicles, and the like. Of course, the present invention is not intended to be limited to these vehicles and fully contemplates being applicable with any type of vehicle.

The vehicle system 10 may include an engine [ 12 , 16 , 18 ] having any number of engine cylinders 12 to create a combustion. An intake 14 may supply ambient air to an intake manifold 16 . The intake manifold 16 may be coupled to the engine cylinders 12 and may operate to distribute the ambient air and fuel mixture to the engine cylinders 12 . An exhaust manifold 18 may also be coupled to the engine cylinders 12 . The exhaust manifold may operate to deliver exhaust gas to an emission control system 20 .

The emission control system 20 may include an Exhaust Gas Recirculation (EGR) valve 22 , a Variable Geometry Turbocharger (VGT) system 24 , and a Diesel Particulate Filter (DPF) system 26 . Inclusion of the emission control system 20 may assist in controlling polluting emissions typically found in the exhaust gas prior to being released from an exhaust 28 . For example, one polluting emission commonly found in the exhaust gas of the vehicle system 10 is Nitrogen Oxide (NO x ). By including the emission control system 20 , the amount of NO x released from the exhaust 28 into the atmosphere may be controlled.

The vehicle system 10 may include a controller 30 to control any one or more of the systems [ 22 , 24 , 26 ] described above. The controller 30 may be a DDEC controller available from Detroit Diesel Corporation, Detroit, Mich. Various features of this type of controller may be found in numerous U.S. patents assigned to Detroit Diesel Corporation. The controller 30 may include any number of programming and processing techniques or strategies not described in full detail herein. The present invention contemplates that the vehicle system 10 may include more than one controller, such that, the EGR valve 22 , the VGT system 24 , the DPF system 26 , and other emission control systems may be controlled by means other than the DDEC controller described above.

The controller 30 may be configured to monitor and control the vehicle system 10 based at least partially on non-sensed operating parameters such that emissions may be controlled without relying completely on hardware sensed operating parameters. In more detail, the present invention contemplates an arrangement where the controller may rely on information provided from actual hardware sensors that physically sense vehicle operating parameters, hereinafter referred to as ‘sensed parameters’, in order to calculate any number of non-sensed operating parameters, hereinafter referred to as ‘non-sensed parameters’. The sensed and non-sensed parameters may be used by the controller to specify vehicle operating set-points for the various vehicle systems.

The controller 30 may use the sensed and non-sensed operating parameters to determine the influence of the various vehicle operating set-points on future operations of the vehicle system 10 . This forward-looking capability allows the controller 30 to virtually test whether a particular set of vehicle operating set-points affect the emissions of the vehicle system 10 . By using the virtually tested vehicle operating set-points, the controller 30 may achieve optimal performance from the emission control system 20 and further control the emissions of the vehicle system 10 .

One advantageous result of determining the non-sensed operating parameters is that numerous hardware sensors currently required in the vehicle system 10 may be eliminated. This may include eliminating reliance on hardware sensors to sense air intake mass flow rate, exhaust gas recirculation (EGR) mass flow rate, a turbine mass flow rate, an engine air mass flow rate, a turbine inlet temperature sensor, and a turbine inlet pressure.

The non-sensed intake mass flow rate may be determined according to the following equation:

M intake = V disp ⁢ RPM engine * I ⁢ ⁢ M ⁢ ⁢ P 120 * R gas * I ⁢ ⁢ M ⁢ ⁢ T ⁢ η vol

where,

M intake is the non-sensed intake mass flow rate;

V disp is a displacement volume;

RPM engine is the sensed vehicle engine speed;

IMP is the sensed intake manifold pressure;

R gas is a gas constant;

IMT is the sensed intake manifold temperature; and

η vol is a volumetric efficiency ratio.

The volumetric efficiency ratio may be determined according to the following equation:

η vol =α(RPM engine ,PR engine )η vol — map (RPM engine ,ρ intake )

where,

α is a function determined by the vehicle engine speed and an engine pressure ratio; and

η vol — map is a function determined by the vehicle engine speed and an engine intake density.

The non-sensed EGR mass flow rate may be determined according to the following equation:

M EGR 2 * T ⁢ ⁢ T ⁢ ⁢ I T ⁢ ⁢ P ⁢ ⁢ I * Disc ⁢ ⁢ C 2 = C 1 * Δ ⁢ ⁢ P + C 2

where,

M EGR is the non-sensed EGR mass flow rate;

TTI is the non-sensed turbine inlet temperature;

TPI is the non-sensed turbine inlet pressure;

DisC is an EGR valve discharge coefficient;

C 1 is a constant value dependent upon the vehicle system 10 provided;

C 2 is a function of the sensed vehicle engine speed and a vehicle engine load; and

αP is an engine pressure differential between the intake manifold 16 and the exhaust manifold 18 that may increase the non-sensed EGR mass flow rate.

The present invention contemplates that the EGR valve discharge coefficient may be determined using a controlled EGR valve pulse width modulation value.

The non-sensed turbine mass flow rate may be determined according to the following equation:

M turbine = M turbine_reduced * T ⁢ ⁢ P ⁢ ⁢ I T ⁢ ⁢ T ⁢ ⁢ I

where,

M turbine is the non-sensed turbine mass flow rate;

M turbine — reduced is a reduced turbine mass flow rate;

TTI is the non-sensed turbine inlet temperature; and

TPI is the non-sensed turbine inlet pressure.

The reduced turbine mass flow rate, M turbine — reduced , may be determined using the following equation:

M turbine — reduced =f turbine — map ( S ,PR turbine )

where,

M turbine — reduced is the reduced turbine mass flow rate;

f turbine — nap is a mapped turbine function;

S is the VGT vane pulse width modulation value; and

PR turbine is a VGT pressure ratio.

The reduced turbine mass flow rate may be determined by mapping the VGT pressure ratio at differing VGT vane pulse width modulation values. The present invention contemplates that the look-up table of the reduced turbine mass flow rate may vary depending upon the vehicle system 10 provided such that multiple look-up tables may be required.

The non-sensed turbine inlet temperature may be determined using the following equation:

T ⁢ ⁢ T ⁢ ⁢ I = I ⁢ ⁢ M ⁢ ⁢ T + L ⁢ ⁢ H ⁢ ⁢ V * F exh_energy * M fueling Cp exh * M intake

where,

TTI is the non-sensed inlet turbine temperature;

IMT is the sensed intake manifold temperature;

LHV is a lower heat value of the fuel;

F exh — energy is an engine exhaust energy fraction;

M fueling a mass fueling rate;

Cp exh is a specific heat of the exhaust gas; and

M intake is the non-sensed intake mass flow rate.

The non-sensed inlet turbine temperature, TTI, may be determined using a steady state and transient look-up table as illustrated in FIG. 2 . The steady state look-up table 50 may map a steady-state exhaust energy fraction against the vehicle engine load at various vehicle engine speeds. Using the steady state look-up table 50 may determine the steady state exhaust energy fraction using the sensed vehicle engine speed and vehicle engine load.

With reference to FIG. 3 , a transient look-up table 52 may map a relative mass rate change at varying vehicle engine speeds so that a correction multiplier may be determined. The correction multiplier may be used in conjunction with the determined steady state exhaust energy fraction in order to determine the engine exhaust energy fraction.

The present invention further contemplates that the steady state look-up table 50 and transient look-up table 52 may vary depending upon the vehicle system 10 provided. Thus, numerous steady state and transient look-up tables that correlate to the vehicle system 10 provided.

The non-sensed turbine inlet pressure may be determined using the following equation:

· V exh_manifold R exh_gas ⁢ ⅆ ⅆ t ⁢ ( T ⁢ ⁢ P ⁢ ⁢ I T ⁢ ⁢ T ⁢ ⁢ I ) = M fueling + M intake - M EGR - M turbine

where,

V exh — manifold is a exhaust manifold volume;

R exh — gas is an exhaust gas constant;

TPI is the non-sensed turbine inlet pressure;

TTI is the non-sensed turbine inlet temperature;

M Fueling is the mass fueling rate;

M intake is the non-sensed intake mass flow rate;

M EGR is the non-sensed EGR mass flow rate; and

M turbine is the non-sensed turbine mass flow rate.

Using the non-sensed intake mass flow rate and the non-sensed EGR mass flow rate the controller 30 may determine an engine air mass flow rate. For example, the difference of non-sensed intake mass flow rate and EGR mass flow rate is equal to the engine air mass flow rate.

While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.