FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION
A METHOD OF CONTROLLING FUEL FLOW VARIATIONS IN VEHICLES DURING TRANSIENT CONDITIONS
APPLICANTS
TATA MOTORS LIMITED, an Indian company having its registered
office at Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001, Maharashtra, India
INVENTORS
Aniket Kulkarni, L Srinivasan, H C Vishwanatha and Nilesh Kankariya all Indian nationals of TATA MOTORS LIMITED, an Indian company having its registered office at Bombay House, 24 Homi Mody Street, Hutatma Chowk, Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following complete specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
This invention relates to a method of controlling fuel flow variations in vehicles utilizing functional snubbing of Manifold Air Pressure (MAP). This particular method finds application in a typical Engine management system (EMS) applied onto a vehicle.
BACKGROUND OF THE INVENTION
Rising fuel costs is one of the primary motive for the demand of increasing fuel efficiency. With the ever-increasing price of fuel, fuel-efficient vehicles are desired all
around the world. The prerequisite is to develop a method to achieve increased fuel efficiency in comparison with a different EMS used on the same vehicle.
DESCRIPTION OF PRIOR ART
The prevalent methods of improving the fuel efficiency of a vehicle work on a number
of different principles. Some methods involve a complex Manifold Air Pressure (MAP) estimation model, which compares the sensor MAP values with that of the model. This is then used to determine the level of transient correction to be applied. Other methods use the rate of change of throttle position sensor (TPS) to determine the amount of transient corrections to be added. Still further methods determine the rate of fuel change during transients, and this is then utilized for further transient corrections.
Another example would be the Electronic throttle control (ETC), wherein, the driver demand (throttle opening) is converted to a torque requirement. This is achieved with the help of an Electronic control unit (ECU), which activates the throttle control depending on the requirement. A signal conditioning is done here which is also called as "snubbing"
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SUMMARY OF THE INVENTION
Current emission requirements, fuel efficiency and drivability aspects have put forth new horizons to achieve. This invention aspires to attain the fuelling efficiency aspect along with resultant benefits in reduction of emissions. In a typical transient condition the driver controls the vehicle speed by varying the throttle. These variations in throttle give rise to subsequent variations in MAP. The fuelling calculated is based on the MAP values. The method of the instant invention works when the steady state and "sporty" operations are not working. These variations in MAP, if "intelligently snubbed", will effectively result in trimming of these fuel variations thus resulting in a significant fuel saving. A table indexed with engine & vehicle speed along with correction required in MAP is used. This table if then further indexed with respect to throttle position, so that a blend of MAP & TPS is obtained. This correction is then fed to the i-MAP snubber process, which then calculates the estimated airflow. This particular method is modeled in Matlab/Simulink and tested in Software in loop simulation (SIL), for the validation of the method. Following the verification, the method is tested in Hardware in loop simulation (HIL) to validate the functionality on a real time environment. Subsequent to this the method is integrated and ported onto a rapid control prototyping hardware to validate its functionality on a real vehicle.
The present invention relates to a method of controlling fuel flow variations in vehicles during transient conditions comprising the steps of: obtaining engine speed, vehicle speed, Manifold Air Pressure (MAP) and Temperature readings through respective sensors; generating a "Differential Air Pressure" table using the values of the engine and vehicle speed; determining a throttle position variation during the transient condition of the vehicle; determining the difference between the present throttle position (Tn) & the throttle position four instances before (Tn_4 ); obtaining i-MAP trim values if the said difference Tn -Tn_4 is greater than a calibratable threshold; and applying the i-MAP trim values to the measured MAP value in a snubber process and the difference between the measured MAP value and the correction to be applied
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determines the snubbed MAP value which is used to determine the precise airflow and fuel flow in the drive injector.
A further embodiment of the invention relates to a method of controlling fuel flow variations in vehicles during transient conditions comprising the steps of: obtaining engine speed, vehicle speed, Manifold Air Pressure (MAP) and Temperature readings through respective sensors; generating a differential air pressure table using the values of the engine and vehicle speed; determining a throttle position variation during the transient condition of the vehicle; determining the difference between the present throttle position (Tn) & the throttle position four instances before (Tn_4 ); and estimating the airflow value based on the engine speed, MAP value and the temperature inputs if the said difference Tn -Tn_4 is lesser than a calibratable threshold.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 : shows the existing transient fuelling methodology
Figure : 2 shows the method of controlling fuel flow variations in vehicles utilizing functional snubbing of MAP methodology according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1 show the existing transient fuelling methodology used. The engine speed (rpm) is measured along with the MAP & Temperature readings through subsequent sensors. This information is then used to compute the estimated airflow, via a table. The estimated airflow varies according to the variation of the engine rpm and MAP readings. The values are simply interpolated from the table and the resultant output value is used for further fuelling calculations. The throttle sensor readings are also processed by the ECU. This particular information plays a vital role since it determines whether the engine is running in full / part load. In the first case, i.e. engine running in full load, the fuelling is done by a full load table, which consists of an increased fuelling to control the exhaust temperatures. In the second case, fuelling
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is done through a part load table which is mapped with respect to Lambda 1, where lambda is the measure of the oxygen content in the exhaust. The maintaining of Lambda at 1 is a crucial factor The condition of maintaining Lambda at 1 is achieved by a closed loop controller. The fuelling quantity thus arrived at is then fed to the injectors which in reality inject the desired quantity.
Figure 2 illustrates the invention. Here we see that using the inputs from engine and vehicle speed sensors, a differential air pressure table is generated. This 2d table is tabulated with differential air pressure (DAP) values required to overcome rolling inertia. Thus typically DAP values will be higher at lower inertia of vehicle in comparison with higher inertia values. In a particular driving scenario, the variations in the throttle position by the driver will serve as input used to determine a TPS rate. This TPS rate is the difference between the present throttle position (Tn) & the throttle position four instances before (Tn-4). If this TPS variation (Tn -Tn_4) is greater than a calibratable threshold then the i-MAP trim values are used.
This particular 1d table is indexed with respect to TPS rate and will give a resultant correction to the measured MAP that is to be applied. The difference between the measured MAP and the correction to be applied will determine the 'intelligently snubbed' MAP value. Thus a large variation in MAP, which occurs during a transient operation, is effectively "snubbed" thus leading to precise airflow estimation, resulting in increased fuel efficiency. This intelligence is operative only during low speed & a high inertia i.e. when the steady state and sporty operations are not working. Thus a typical range for this band would be between 20 to 40km/h. This results in a snubbed MAP value which will then be the input of the air flow estimator.
The new intelligently snubbed MAP value is then used for airflow estimation. A simple interpolation will result in the fuelling values being calculated.
The estimated airflow varies according to the variation of the engine rpm and the snubbed i-MAP readings. The values are simply interpolated from the table and the resultant output value is used for further fuelling calculations. The throttle sensor
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readings are also processed by the ECU. The throttle variations plays an important role in determining if the engine is running in full load or in part load. In the case of the engine running in full load, the fuelling is done by a full load table, which consists o f an increased fuelling to control the exhaust temperatures. In the second case, fuelling is done through a part load table, which is mapped with respect with respect to Lambda 1, Where Lambda is the measure Of the oxygen content in the exhaust. The maintaining of Lambda is the measure of the oxygen content in the exhaust. The maintaining of Lambda at 1 is crucial factor, for satisfying emission criteria that is achieved by a closed loop controller. The fuelling quantity thus arrived at is then fed to the injectors which in reality inject the desired quantity.
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We Claim:
1. A method of controlling fuel flow variations in vehicles during transient conditions
comprising the steps of:
obtaining engine speed, vehicle speed, Manifold Air Pressure (MAP) and
Temperature readings through respective sensors;
generating a differential air pressure table using the values of the engine and vehicle speed;
determining a throttle position variation during the transient condition of the vehicle;
determining the difference between the present throttle position (Tn) & the throttle position four instances before (Tn_4 );
obtaining i-MAP trim values if the said difference Tn - Tn_4 is greater than a calibratable threshold; and
applying the i-MAP trim values to the measured MAP value in a snubber process and the difference between the measured MAP value and the correction to be applied determines the snubbed MAP value which is used to determine the precise airflow and fuel flow in the drive injector.
2. The method as claimed in claim 1, wherein the estimated airflow is determined using the engine speed and the snubbed i-MAP value.
3. The method as claimed in claim 1, wherein, if the throttle position sensor indicates that the engine is running in full load, the fuelling is done by interpolation based on a full load table, which computes an increased fuelling based on the estimated airflow to control the exhaust temperatures during full load.
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4. The method as claimed in claim 1, wherein, if the throttle position sensor indicates that the engine is running in part load, the lambda controller is tuned to achieve a stoichiometric air/fuel ratio of Lambda = 1 to satisfy emission criteria and the fuel flow rate is then computed based on the estimated air flow and the part load running condition of the engine.
5. A method of controlling fuel flow variations in vehicles during transient conditions comprising the steps of:
obtaining engine speed, vehicle speed, Manifold Air Pressure (MAP) and Temperature readings through respective sensors;
generating a differential air pressure table using the values of the engine and vehicle speed;
determining a throttle position variation during the transient condition of the vehicle;
determining the difference between the present throttle position (Tn) & the throttle position four instances before (Tn_4); and
estimating the airflow value based on the engine speed, MAP value and the temperature inputs if the said difference Tn -Tn_4 is lesser than a calibratable threshold.
6. The method as claimed in claim 5, wherein, if the throttle position sensor indicates that the engine is running in foil load, the fuelling is done by interpolation based on a full load table, which computes an increased fuelling based on the estimated air flow to control the exhaust temperatures during full load.
7. The method as claimed in claim 5, wherein, if the throttle position sensor indicates that the engine is running in part load, the lambda controller is tuned to achieve a stoichiometric air/fuel ratio of Lambda = 1 to satisfy emission criteria and
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the fuel flow rate is then computed based on the estimated air flow and the part load running condition of the engine.
8. A method of controlling fuel flow variations in vehicles during transient conditions substantially as hereinabove described with respect to the accompanying drawings.
Dated this 6th day of October 2006

(KARUNA GOLERIA)
Of DePENNING & DePENNING
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TATA MOTORS LIMITED By their Agent and Attorney

ABSTRACT
"A method of controlling fuel flow variations in vehicles during transient
conditions"
The invention mentioned herein is a method to control the fuel How variations during a transient environment. In a typical transient condition on a vehicle we see that due to the driver's perception of controlling a said vehicle speed, we sec subsequent variations in throttle. These lead to variations in the Electronic control unit (ECU) calculated fuelling. The method aims to control these variations thus leading to increased fuel efficiency along with resultant reduction in emission.
(Fig 2)