Claims:WE CLAIM:
1. A system (100) for determining an age of a catalytic converter (110), the system comprising:
a first lambda sensor (120) connected between an exhaust port (130a) of an engine (130) and an inlet (110a) of the catalytic converter (110), the first lambda sensor (120) configured to generate a first signal indicative of oxygen level in untreated exhaust gas from the engine (130);
a second lambda sensor (140) coupled with an outlet (110b) of the catalytic converter (110), the second lambda sensor (140) configured to generate a second signal indicative of oxygen level in treated exhaust gas from the catalytic converter (110);
an Engine Control Unit (ECU) (150) coupled with the first lambda sensor (120), the second lambda sensor (140) and the engine (130), the ECU (150) configured to:
determine an operating condition of the vehicle, the operating condition comprising an operating speed of the engine (ωOP), and an operating intake manifold pressure (MAPOP) and/or a gear position (GPOP);
measure a phase shift (ᶲ) between the second signal and the first signal at the determined operating condition for a rich air fuel mixture and/or a lean air fuel mixture injected in the engine (130); and
estimate the age of the catalytic converter (110) based on the operating condition and the measured phase shift (ᶲ).

2. The system as claimed in claim 1, wherein the ECU (150) is configured to:
obtain engine speeds (ω) over a rolling window of time;
determine a standard deviation of the engine speeds (ωsd) over the rolling window of time;
determine a standard deviation of derivative of the engine speeds (dωsd) over the rolling window of time;
select the operating speed of the engine (ωOP), the operating speed (ωOP) being a mean of the engine speeds (ωmean) over the rolling window of time if: the standard deviation of the engine speeds (ωsd) is less than a first predetermined value (ωsd1) and standard deviation of derivative of the engine speeds (dωsd) is less than a second predetermined value (dωsd1).

3. The system as claimed in claim 1, comprising an intake manifold pressure sensor (160) coupled with the ECU (150) and configured to measure intake manifold pressures (MAP).

4. The system as claimed in claim 3, wherein the ECU (150) is configured to:
obtain the intake manifold pressures (MAP) over the rolling window of time;
determine a standard deviation of the intake manifold pressures (MAPsd) over the rolling window of time;
determine a standard deviation of derivative of the intake manifold pressures (dMAPsd) over the rolling window of time; and
select the operating intake manifold pressure (MAPOP), the operating intake manifold pressure (MAPOP) being the mean of the intake manifold pressures (MAPmean) over the rolling window of time if: the standard deviation of the intake manifold pressures (MAPsd) is less than a third predetermined value (MAPsd1) and the standard deviation of derivative of the intake manifold pressures (dMAPsd) is less than a fourth predetermined value (dMAPsd1).

5. The system as claimed in claim 1, wherein the ECU (150) is configured to:
inject a rich air fuel mixture in the engine (130) for a first predetermined time (tPDT1) and a lean air fuel mixture in the engine (130) for a second predetermined time (tPDT2);
calculate a ratio (R) of the second signal and the first signal;
assign the calculated ratio (R) as zero if the ratio (R) is less than a lower threshold value (RLT), and as one if the ratio (R) is in between the lower threshold value (RLT) and an upper threshold value (RUT); and
calculate a time period (t) for which the assigned value of ratio (R) remains zero during the first predetermined time (tPDT1), the time period (t) indicative of the phase shift (ᶲ) of the second lambda sensor.

6. The system as claimed in claim 1, wherein the ECU (150) comprises an estimation module (150a) having pre-fed data for multiple operating conditions, each of the operating condition corresponding to a phase shift (ᵠ) value.

7. The system as claimed in claim 6, wherein the estimation module (150a) is configured to predict age of the catalytic converter (110) based on the operating condition and the phase shift (ᵠ) value.

8. The system as claimed in claim 7, wherein the estimation module (150a) has pre-fed data for age of the catalytic converter (110) corresponding to each of the operating conditions and phase shift (ᵠ) value associated thereto.

9. The system as claimed in claimed in any of the preceding claims, comprising a malfunction indicator light (170) coupled with the ECU (150) wherein the ECU (150) is configured to illuminate the malfunction indicator light (170) if the estimated age of the catalytic converter (110) is greater than a threshold age.

10. The system as claimed in claim 5, wherein the first predetermined time (tPDT1) is 20 seconds, and the second predetermined time (tPDT2) is less than or equal to 20 seconds.

11. The system as claimed in claim 5, wherein the lower threshold value (RLT) of the ratio (R) is 0.86 and the upper threshold (RUT) value of the ratio (R) is 1.12.

12. The system as claimed in claim 5, wherein the lower threshold value (RLT) of the ratio (R) is 0.6 and the upper threshold value (RUT) of the ratio (R) is 1.20.

13. A method for determining an age of a catalytic converter (110), the method comprising the steps of:
generating (301) a first signal, by a first lambda sensor (120) connected between an exhaust port (130a) of an engine (130) and an inlet (110a) of the catalytic converter (110), indicative of oxygen level in untreated exhaust gas from the engine (130);
generating (302) a second signal, by a second lambda sensor (140) coupled with an outlet (110b) of the catalytic converter (110), indicative of oxygen level in treated exhaust gas from the catalytic converter (110);
determining (303), by an Engine Control Unit (ECU) (150), an operating condition of the vehicle, the operating condition comprising an operating speed of the engine (ωOP), and an operating intake manifold pressure (MAPOP) and/or a gear position (GPOP);
measuring (304), by the ECU (150), a phase shift (ᶲ) between the second signal and the first signal at the determined operating condition for a rich air fuel mixture and/or a lean air fuel mixture injected in the engine (130); and
estimating (305), by the ECU (150), the age of the catalytic converter (110) based on the operating condition and the measured phase shift (ᶲ).

14. The method as claimed in claim 13, comprising the steps of:
obtaining (303a), by the ECU (150), engine speeds (ω) over a rolling window of time;
determining (303b), by the ECU (150), a standard deviation of the engine speeds (ωsd) over the rolling window of time;
determining (303c), by the ECU (150), a standard deviation of derivative of engine speeds (dωsd) over the rolling window of time; and
selecting (303d), by the ECU (150), the operating speed of the engine (ωOP), the operating speed (ωOP) being a mean of the engine speeds (ωmean) over the rolling window of time if: the standard deviation of the engine speeds (ωsd) is less than a first predetermined value (ωsd1) and standard deviation of derivative of the engine speeds (dωsd) is less than a second predetermined value (dωsd1).

15. The method as claimed in claim 13, comprising the step of measuring (303e), by an intake manifold pressure sensor (160), intake manifold pressures (MAP).

16. The method as claimed in claim 15, comprising the steps of:
obtaining (303f), by the ECU (150), the intake manifold pressures (MAP) over the rolling window of time;
determining (303g), by the ECU (150), a standard deviation of the intake manifold pressures (MAPsd) over the rolling window of time;
determining (303h), by the ECU (150), a standard deviation of derivative of the intake manifold pressures (dMAPsd) over the rolling window of time; and
selecting (303i), by the ECU (150), the operating intake manifold pressure (MAPOP), the operating intake manifold pressure (MAPOP) being the mean of the intake manifold pressures (MAPmean) over the rolling window of time if: the standard deviation of the intake manifold pressures (MAPsd) is less than a third predetermined value (MAPsd1) and the standard deviation of derivative of the intake manifold pressures (dMAPsd) is less than a fourth predetermined value (dMAPsd1).

17. The method as claimed in claim 13, comprising the steps of:
injecting (304a), by the ECU (150), a rich air fuel mixture in the engine (130) for a first predetermined time (tPDT1) and a lean air fuel mixture in the engine (130) for a second predetermined time (tPDT2);
calculating (304b), by the ECU (150), a ratio (R) of the second signal and the first signal;
assigning (304c, 304d), by the ECU (150), the calculated ratio (R) as zero if the ratio (R) is less than a lower threshold value (RLT), and as one if the ratio (R) is in between the lower threshold value (RLT) and an upper threshold value (RUT); and
calculating (304e), by the ECU (150), a time period (t) for which the assigned value of ratio (R) remains zero during the first predetermined time (tPDT1), the time period (t) indicative of the phase shift (ᶲ) of the second lambda sensor.

18. The method as claimed in claim 13, wherein the ECU (150) comprises an estimation module (150a) having pre-fed data for multiple operating conditions, each of the operating condition corresponding to a phase shift (ᵠ) value.

19. The method as claimed in claim 18, comprising the step of predicting (305a), by the estimation module (150a), age of the catalytic converter (110) based on the operating condition and the phase shift (ᵠ) value.

20. The method as claimed in any of the preceding claims, comprising the step of illuminating (305b), by the ECU (150), a malfunction indicator light (170) if the estimated age of the catalytic converter (110) is greater than a threshold age.

21. The method as claimed in claim 17, wherein the first predetermined time (tPDT1) is 20 seconds, and the second predetermined time (tPDT2) is less than or equal to 20 seconds.

22. The method as claimed in claim 17, wherein the lower threshold value (RLT) of the ratio (R) is 0.86 and the upper threshold value (RUT) of the ratio (R) is 1.12.

23. The method as claimed in claim 17, wherein the lower threshold value (RLT) of the ratio (R) is 0.6 and the upper threshold value (RUT) of the ratio (R) is 1.20.

Dated this 28th day of March 2021

TVS MOTOR COMPANY LIMITED
By their Agent & Attorney

(Nikhil Ranjan)
of Khaitan & Co
Reg No IN/PA-1471
, Description:FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
[See section 10, Rule 13]

TITLE OF INVENTION
A System for Determining Age of a Catalytic Converter and Method Thereof

APPLICANT
TVS MOTOR COMPANY LIMITED, an Indian company, having its address at “Chaitanya”, No.12 Khader Nawaz Khan Road, Nungambakkam, Chennai 600 006.

PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
[001] The present invention relates to a system for determining age of a catalytic converter and method thereof.

BACKGROUND OF THE INVENTION
[002] A catalytic converter converts toxic gases emanating from an engine of a vehicle into non-toxic through redox reaction. A honeycomb structured wash-coat provided inside the catalytic convertor increases the surface area to get in touch with the exhaust gases which improves the conversion effectiveness. The toxic gases CO, NO, and THC are converted into carbon dioxide, nitrogen, and water vapor. The wash coat of the catalyst gets filled with excess oxygen generated during the oxidation reaction. In a non-stoichiometric reaction, i.e. air-fuel ratio (AFR) not equal to 14.7:1, some moles of oxygen are required to balance the redox reaction.
[003] During a lean burn cycle, excess oxygen is stored onto the surface of the catalytic convertor whereas during a rich air-fuel mixture cycle, the catalytic convertor releases stored oxygen for burning of the unburnt hydrocarbons. The stored oxygen is released in the reduction reaction and completes the conversion reaction.
[004] Increasingly stringent regulations have limited the permissible levels for emissions. As such, vehicle manufacturers have developed various methods to reduce emissions while improving vehicle performance and fuel economy. To meet these requirements, it is necessary to monitor the performance of the catalyst using an on-board catalyst monitor. These monitors are designed to meet the onboard diagnostics II regulation (OBD-II) which states that an automobile manufacturer must be able to determine when the performance of the catalyst has deteriorated to the point that the vehicle is emitting more than the regulated limit of pollutants.
[005] Oxygen storing capability of the catalytic convertor plays a vital role in achieving a substantially balanced reaction closer to stoichiometric ratio. Thus, it is important to accurately determine the oxygen storage capacity of the catalytic convertor to monitor the age of the catalyst and thereby trigger a corrective or repair action.
[006] Health of the catalytic converter can be determined based on the mathematical modelling of the catalytic converter and data driven methods. A single state integrator model is generally used for onboard oxygen storage capacity estimation of the catalytic convertor. However, the catalytic converter is a complex nonlinear system and therefore the single state integrator model does not represent the accurate and actual time dynamics of the catalytic convertor. These models are linearized at one operating point for measuring state of oxygen storage capacity, but that measurement will not provide the accurate data in dynamically changing operating conditions of the catalytic convertor.
[007] On the other hand, implementing a complex non-linear model based on real time data necessitates high amount of data to be analyzed in short time, thereby demanding high computing power as well as more energy consumption in analyzing and computation of voluminous data, which is undesirable.
[008] Other methods are based on data selected at two operating points viz. idling condition and cruising condition. At idling condition, the AFR is at stoichiometric level, exhaust flow rate is less, temperature of catalyst is less, so conversion is less, thereby leading to more emissions above thresholds dictated by OBD-II. Thus, measurement by a lambda sensor at idling condition will not provide accurate health of the catalyst. At cruising condition, temperature of gases is less, flow is high, however, the rate of reaction (follows Arrhenius equation) is low, conversion is less, leading to more emissions above thresholds dictated by OBD-II. Thus, measurement by a lambda sensor at cruising condition will also not provide accurate health of the catalyst.
[009] Moreover, the reaction rate along the entire surface area of the catalyst is difficult to predict and the age of the catalyst based on the reaction rate needs to be predicted at different conditions of functioning of the catalyst, and not limited to cruising and idling conditions only.
[010] Thus, there is a need in the art for a system for determining age of a catalytic converter and a method thereof which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION
[011] In one aspect, the present invention is directed to a system for determining an age of a catalytic converter. The system includes a first lambda sensor connected between an exhaust port of an engine and an inlet of the catalytic converter, a second lambda sensor coupled with an outlet of the catalytic converter and an Engine Control Unit (ECU) coupled with the first lambda sensor, the second lambda sensor and the engine. The first lambda sensor is configured to generate a first signal indicative of oxygen level in untreated exhaust gas from the engine. The second lambda sensor is configured to generate a second signal indicative of oxygen level in treated exhaust gas from the catalytic converter. The ECU is configured to: determine an operating condition of the vehicle, the operating condition comprising an operating speed of the engine, and an operating intake manifold pressure and/or a gear position; measure a phase shift between the second signal and the first signal at the determined operating condition for a rich air fuel mixture and/ or a lean air fuel mixture injected in the engine; and estimate the age of the catalytic converter based on the operating condition and the measured phase shift.
[012] In an embodiment of the invention, the ECU is configured to: obtain engine speeds over a rolling window of time; determine a standard deviation of the engine speeds over the rolling window of time; determine a standard deviation of derivative of the engine speeds over the rolling window of time; select the operating speed of the engine, the operating speed being a mean of the engine speeds over the rolling window of time if: the standard deviation of the engine speeds is less than a first predetermined value and standard deviation of derivative of the engine speeds is less than a second predetermined value.
[013] In another embodiment of the invention, the system includes an intake manifold pressure sensor coupled with the ECU and configured to measure intake manifold pressures. The ECU is configured to: obtain the intake manifold pressures over the rolling window of time; determine a standard deviation of the intake manifold pressures over the rolling window of time; determine a standard deviation of derivative of the intake manifold pressures over the rolling window of time; and select the operating intake manifold pressure, the operating intake manifold pressure being the mean of the intake manifold pressures over the rolling window of time if: the standard deviation of the intake manifold pressures (is less than a third predetermined value and the standard deviation of derivative of the intake manifold pressures is less than a fourth predetermined value.
[014] In still another embodiment of the invention, the ECU is configured to: inject a rich air fuel mixture in the engine for a first predetermined time and a lean air fuel mixture in the engine for a second predetermined time; calculate a ratio of the second signal and the first signal; assign the calculated ratio as zero if the ratio is less than a lower threshold value, and as one if the ratio is in between the lower threshold value and an upper threshold value; and calculate a time period for which the assigned value of ratio remains zero during the first predetermined time, the time period indicative of the phase shift of the second lambda sensor.
[015] In yet another embodiment of the invention, the ECU includes an estimation module having pre-fed data for multiple operating conditions, each of the operating condition corresponding to a phase shift value.
[016] In still another embodiment of the invention, the estimation module is configured to predict age of the catalytic converter based on the operating condition and the phase shift value.
[017] In a further embodiment of the invention, the estimation module has pre-fed data for age of the catalytic converter corresponding to each of the operating conditions and phase shift value associated thereto.
[018] In a still further embodiment of the invention, the system includes a malfunction indicator light coupled with the ECU wherein the ECU is configured to illuminate the malfunction indicator light if the estimated age of the catalytic converter is greater than a threshold age.
[019] In another embodiment of the invention, the first predetermined time is 20 seconds, and the second predetermined time is less than or equal to 20 seconds.
[020] In still another embodiment of the invention, the lower threshold value of the ratio is 0.86 and the upper threshold value of the ratio is 1.12. In another embodiment, the lower threshold value of the ratio is 0.6 and the upper threshold value of the ratio is 1.20.
[021] In another aspect, the present invention is directed to a method for determining an age of a catalytic converter. The includes the steps of: generating a first signal, by a first lambda sensor connected between an exhaust port of an engine and an inlet of the catalytic converter, indicative of oxygen level in untreated exhaust gas from the engine; and generating a second signal, by a second lambda sensor coupled with an outlet of the catalytic converter, indicative of oxygen level in treated exhaust gas from the catalytic converter. The method also includes the steps of: determining, by an Engine Control Unit (ECU), an operating condition of the vehicle, the operating condition comprising an operating speed of the engine, and an operating intake manifold pressure and/or a gear position; measuring, by the ECU, a phase shift between the second signal and the first signal at the determined operating condition for a rich air fuel mixture and/or a lean air fuel mixture injected in the engine; and estimating, by the ECU, the age of the catalytic converter based on the operating condition and the measured phase shift.
[022] In an embodiment of the invention, the method includes the steps of: obtaining, by the ECU, engine speeds over a rolling window of time; determining, by the ECU, a standard deviation of the engine speeds over the rolling window of time; determining, by the ECU, a standard deviation of derivative of engine speeds over the rolling window of time; selecting, by the ECU, the operating speed of the engine, the operating speed being a mean of the engine speeds over the rolling window of time if: the standard deviation of the engine speeds is less than a first predetermined value and standard deviation of derivative of the engine speeds is less than a second predetermined value.
[023] In another embodiment of the invention, the method includes the step of measuring, by an intake manifold pressure sensor, intake manifold pressures.
[024] In another embodiment of the invention, the method includes the steps of: obtaining, by the ECU, the intake manifold pressures over the rolling window of time; determining, by the ECU, a standard deviation of the intake manifold pressures over the rolling window of time; determine, by the ECU, a standard deviation of derivative of the intake manifold pressures over the rolling window of time; and selecting, by the ECU, the operating intake manifold pressure, the operating intake manifold pressure being the mean of the intake manifold pressures over the rolling window of time if: the standard deviation of the intake manifold pressures is less than a third predetermined value and the standard deviation of derivative of the intake manifold pressures is less than a fourth predetermined value.
[025] In still another embodiment of the invention, the method includes the steps of: injecting, by the ECU, a rich air fuel mixture in the engine for a first predetermined time and a lean air fuel mixture in the engine for a second predetermined time; calculating, by the ECU, a ratio of the second signal and the first signal; assigning, by the ECU, the calculated ratio as zero if the ratio is less than a lower threshold value, and as one if the ratio is in between the lower threshold value and an upper threshold value; and calculating, by the ECU, a time period for which the assigned value of ratio remains zero during the first predetermined time, the time period indicative of the phase shift of the second lambda sensor.
[026] In a further embodiment of the invention, the ECU comprises an estimation module having pre-fed data for multiple operating conditions, each of the operating condition corresponding to a phase shift value.
[027] In a still further embodiment of the invention, the method includes the step of predicting, by the estimation module, age of the catalytic converter based on the operating condition and the phase shift value.
[028] In yet another embodiment of the invention, the method includes the step of illuminating, by the ECU, a malfunction indicator light if the estimated age of the catalytic converter is greater than a threshold age.
[029] In another embodiment of the invention, the first predetermined time is 20 seconds, and the second predetermined time is less than or equal to 20 seconds.
[030] In still another embodiment of the invention, the lower threshold value of the ratio is 0.86 and the upper threshold value of the ratio is 1.12.
[031] In another embodiment of the invention, the lower threshold value of the ratio is 0.6 and the upper threshold value of the ratio is 1.20.

BRIEF DESCRIPTION OF THE DRAWINGS
[032] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 illustrates a system for determining an age of a catalytic converter in accordance with an embodiment of the present invention.
Figure 2 illustrates the system of Figure 1 with an Engine Control Unit including an estimation module in accordance with an embodiment of the present invention.
Figure 3 illustrates a method for determining an age of a catalytic converter in accordance with an embodiment of the present invention.
Figures 3a, 3b and 3c show details of the steps illustrated in Figure 3 in accordance with an embodiment of the present invention.
Figure 4 shows a graph between a first signal from a first lambda sensor and a second signal from a second lambda sensor vs time in accordance with an embodiment of the present invention.
Figure 5 shows a graph between a ratio of the second signal and the first signal vs time in accordance with an embodiment of the present invention.
Figure 6 shows a graph between a moving average filtered ratio vs time in accordance with an embodiment of the present invention.
Figure 7 shows a graph between quantization of ratio vs time in accordance with an embodiment of the present invention.
Figure 8a shows a 3-D graph illustrating the behavior of a phase shift with throttle percentage and engine speed for a catalytic converter having an age at 10000 kilometers and used as a pre-fed data for an estimation module.
Figure 8b shows a 3-D graph illustrating the behavior of the phase shift with throttle percentage and engine speed for the catalytic converter having an age at 60000 kilometers and used as a pre-fed data for the estimation module.

DETAILED DESCRIPTION OF THE INVENTION
[033] Various features and embodiments of the present invention here will be discernible from the following further description thereof, set out hereunder. In the ensuing exemplary embodiments, the vehicle is a two wheeled vehicle. However, it is contemplated that the disclosure in the present invention may be applied to any automobile capable of accommodating the present subject matter without defeating the spirit of the present invention.
[034] In one aspect, the present invention relates to a system for determining an age of a catalytic converter.
[035] In the present context, the catalytic converter includes a catalyst which is usually platinum (Pt), along with palladium (Pd), and rhodium (Rh). Additionally, the catalytic converter also includes a substrate for depositing the catalyst, a washcoat which is a carrier for the catalyst, and ceria or ceria-zirconia which are mainly added as oxygen storage promoters.
[036] As shown in Figure 1, the system 100 includes a first lambda sensor 120 connected between an exhaust port 130a of an engine 130 and an inlet 110a of the catalytic converter 110, and a second lambda sensor 140 coupled with an outlet 110b of the catalytic converter 110. The first lambda sensor 120 is configured to generate a first signal indicative of oxygen level in untreated exhaust gas from the engine 130. The second lambda sensor 140 is configured to generate a second signal indicative of oxygen level in treated exhaust gas from the catalytic converter 110.
[037] The system 100 also includes an intake manifold pressure sensor 160 and a malfunction indicator light 170. The intake manifold pressure sensor 160 is configured to measure intake manifold pressures MAP. The malfunction indicator light 170 illuminates to indicate that the catalytic converter has aged and should be replaced.
[038] The system also includes an Engine Control Unit (ECU) 150 coupled with the first lambda sensor 120, the second lambda sensor 140, the engine 130, the intake manifold pressure sensor 160 and the malfunction indicator light 170.
[039] As shown in Figure 2, the ECU 150 includes an estimation module 150a. The estimation module 150a has a pre-fed data for multiple operating conditions, each of the operating condition corresponding to a phase shift ᵠ value. Further, the estimation module 150a is configured to predict age of the catalytic converter 110 based on the operating condition and the phase shift ᵠ value. Operating condition and phase shift have been described in detail hereinbelow.
[040] In an embodiment, the estimation module 150a is trained and tested using the pre-fed data. For instance, the estimation module 150a is based on machine learning techniques or artificial neural networks which is trained using the pre-fed data. In this regard, Figures 8a and 8b show two sets of data used as pre-fed data for the estimation module 150a for the catalytic converter aged at 10000 kilometers and 60000 kilometers, respectively. The data from Figures 8a and 8b is then utilized for predicting the age of the catalytic converter based on the operating condition and the phase shift ᵠ value determined in real time.
[041] In an embodiment, the ECU 150 is configured to: determine the operating condition of the vehicle, the operating condition includes an operating speed of the engine ωOP, and an operating intake manifold pressure MAPOP and/or a gear position GPOP; measure a phase shift ᶲ between the second signal and the first signal at the determined operating condition for a rich air fuel mixture and/or a lean air fuel mixture injected in the engine 130; and estimate the age of the catalytic converter 110 based on the operating condition and the measured phase shift ᶲ.
[042] For determining the operating condition of the vehicle, the ECU 150 is configured to obtain: engine speeds ω over a rolling window of time, and the intake manifold pressures MAP over the rolling window of time. In the present context, rolling over time implies that the data (for e.g., engine speeds and the intake manifold pressures) is obtained and kept as buffer for some time and processed thereafter. For instance, the data is collected for past 5 seconds with a sampling frequency of 10 Hz. This implies that 50 data points have been collected. The ECU 150 utilizes these 50 data points to calculate standard deviation for determining the operating condition of the vehicle. The rolling here implies that the vehicle is running with continuous generation of the data which is rolled ahead with one step with the oldest data point being removed. For this, the ECU 150 includes a computer readable media, which may include but are not limited to read only memory (ROM), a random access memory (RAM), and a keep-alive memory (KAM).
[043] In the present context, the standard deviation refers to a measure of the amount of variation or dispersion of a set of values, for e.g., engine speeds ω, and the intake manifold pressures MAP.
[044] Since the present invention determines the operating condition of the vehicle while estimating the age of the catalytic converter 110, the present invention is no longer limited to fixed operating condition of the vehicle, such as an idling condition and/or a cruising condition. Therefore, the present invention determines the age of the catalytic converter 110 more precisely and in real time.
[045] It is further to be understood that the purpose of determining standard deviation and standard deviation of the derivative of the engine speeds ωsd as well as the intake manifold pressures MAP over the rolling window of time is to ensure that the vehicle operating condition is constant while determining the age of the catalytic converter 110. This further ensures an accurate estimation of the age.
[046] As described hereinbefore, the ECU 150 is configured to estimate the age of the catalytic converter 110 based on the operating condition and the measured phase shift ᶲ. In this regard, reference is now made to Figures 3, 3a, 3b and 3c which illustrate configuration of the system 100 and a method for determining the age of the catalytic converter. As shown in Figure 3, at step 301, the first lambda sensor 120 generates the first signal which indicates the oxygen level in the untreated gas from the engine 130.
[047] At step 302, the second lambda sensor 140 also generates the second signal indicative of oxygen level in the treated exhaust gas from the catalytic converter 110.
[048] Subsequently, at step 303, the ECU 150 determines the operating condition of the vehicle. For this, the ECU 150 takes into consideration the operating speed of the engine ωOP, and the operating intake manifold pressure MAPOP and/or the gear position GPOP. In an embodiment, the operating gear position GPOP remains fixed while determining the operating condition. Said otherwise, the ECU 150 takes into consideration the operating speed of the engine ωOP, and the operating intake manifold pressure MAPOP only.
[049] Once the operating condition of the vehicle is determined, the subsequent steps of the method are performed at constant operating condition. Said otherwise, in the subsequent method steps the operating condition remains fixed.
[050] Thereafter, at step 304, the ECU 140 measures the phase shift ᶲ between the second signal and the first signal at the determined operating condition for the rich air fuel mixture or the lean air fuel mixture injected in the engine 130.
[051] The operating condition and the measured phase shift ᶲ is then used by the ECU 150 for estimating the age of the catalytic converter, as shown at step 305.
[052] Referring to Figure 3a which shows the detailed steps for determining the operating condition of the vehicle. Since the ECU 150 is coupled with plurality of sensors (including engine speed sensor, vehicle speed sensor, and the likes), the ECU 150 is configured to obtain the engine speeds ω over the rolling window of time as shown at step 303a.
[053] Thereafter, at step 303b, the ECU 150 determines the standard deviation of the engine speeds ωsd over the rolling window of time. Subsequently, at step 303c, the ECU 150 also determines the standard deviation of derivative of the engine speeds dωsd over the rolling window of time.
[054] At step 303d, the ECU determines the operating speed of the engine ωOP. The operating speed of the engine ωOP is the mean of the engine speeds ωmean over the rolling window of time if: the standard deviation of the engine speeds ωsd is less than a first predetermined value ωsd1 and the standard deviation of derivative of the engine speeds dωsd is less than a second predetermined value dωsd1.
[055] Meanwhile, at step 303e, the intake manifold pressure sensor 160 measures the intake manifold pressures MAP. At step 303f, the ECU 150 obtains the intake manifold pressures MAP over the rolling window of time. Thereafter, at step 303g, the ECU 150 determines the standard deviation of the intake manifold pressures MAPsd over the rolling window of time. At step 303h, the ECU 150 determines the standard deviation of derivative of the intake manifold pressures dMAPsd over the rolling window of time. Finally, at step 303i, the ECU 150 selects the operating intake manifold pressure MAPOP. The operating intake manifold pressure MAPOP is the mean of the intake manifold pressures MAPmean over the rolling window of time if: the standard deviation of the intake manifold pressures MAPsd is less than a third predetermined value MAPsd1 and the standard deviation of derivative of the intake manifold pressures dMAPsd is less than a fourth predetermined value (dMAPsd1).
[056] The operating condition of the vehicle as determined in the present invention ensures that the vehicle is neither accelerating nor decelerating and that the engine speeds ω and the intake manifold pressures MAP are constant over the rolling window of time.
[057] Referring to Figure 3b which shows the detailed steps for measuring the phase shift ᶲ between the second signal and the first signal at the determined operating condition. For measuring the phase shift ᶲ, at step 304a, the ECU 150 injects the rich air fuel mixture in the engine 130 for a first predetermined time tPDT1. After the first predetermined time tPDT1, the ECU 150 also injects the lean air fuel mixture in the engine 130 for a second predetermined time tPDT2. In an embodiment, the first predetermined time tPDT1 is 20 seconds, and the second predetermined time tPDT2 is less than or equal to 20 seconds.
[058] At step 304b, the ECU 150 calculates a ratio R of the second signal and the first signal.
[059] Referring to Figure 4, the pre and post values correspond to the first signal and the second signal from the first lambda sensor 120 and the second lambda sensor 140, respectively. The graph shown in Figure 4 is recorded at one specific operating condition. During this operating condition, the rich air fuel mixture is injected for the first predetermined time tPDT1 and the lean air fuel mixture is injected for the second predetermined time tPDT2. It is also possible that first the lean air fuel mixture is injected for the second predetermined time tPDT2 followed by the rich air fuel mixture for the first predetermined time tPDT1.
[060] As shown in Figure 4, there are four regions to identify the ratio R for the second lambda sensor 140 and the first lambda sensor 120. A first region is where the catalyst is fully filled with oxygen (refer the region between t1 seconds to t2 seconds). In this region, when a lean air fuel mixture is injected in the engine for the second predetermined time tPDT2, the first signal indicates that exhaust gas has a composition of lean air fuel mixture and the second signal indicates that exhaust gas coming out of the catalytic converter also has a composition of lean air fuel mixture, i.e. the ratio R is 1.
[061] Now at this point when a rich air fuel mixture is injected for a first predetermined time tPDT1, referring to a second region between t2 seconds to t3 seconds, the first signal will now indicate the rich air fuel mixture and the second signal will indicate the lean air fuel mixture, i.e. the ratio R will be 0. This will continue till the oxygen is completely emptied out. When the catalyst is completely empty, referring to a third region between t3 seconds to t4 seconds, both the second signal and the first signal will indicate rich air fuel mixture, i.e. the ratio R will be 1. At this point, when lean air fuel mixture is injected, i.e. at t4 seconds, the first signal will indicate lean air fuel mixture while the second signal will indicate the rich air fuel mixture. Hence, the ratio R will be greater than 1.
[062] Thereafter, the ECU 150 assigns the calculated ratio R as zero if the ratio R is less than a lower threshold value RLT, as shown at step 304c. Alternately, at step 304d, the ECU 150 assigns the ratio R the value one if the ratio R is in between the lower threshold value RLT and an upper threshold value RUT.
[063] In an embodiment, the lower threshold value RLT of the ratio R is 0.86 and the upper threshold value RUT of the ratio R is 1.12. In another embodiment, the lower threshold value RLT of the ratio R is 0.6 and the upper threshold value RUT of the ratio R is 1.20.
[064] The purpose of assigning the ratio R the value of zero or one is to ensure that the measurement is free of any noise. The air fuel mixture measured by the first lambda sensor 120 and the second lambda sensor 140 is prone to lot of noises in measurement. Due to aging effect of the lambda sensors, the measured values may deviate from the true value. It might be possible that the values measured by the lambda sensors are lesser than the actual measurement. This results in the ratio R being very noisy. Therefore, to take into consideration such incorrect measurements by the lambda sensors, the present invention utilizes the upper threshold value RUT and the lower threshold value RLT and quantize the ratio into three stages (R = 0, RLT < R < RUT, and R > RUT). With this methodology, the lambda sensor aging effect and measurement noise is taken care of. This is also referred as moving average filtering in the ratio R, as shown in Figure 6.
[065] Whenever RLT < R < RUT, R is assigned a value of 1, however, a phase shift is not computed. Whenever, R > RUT, R is assigned a value of 2 and a phase shift is not computed. In both these scenarios as determined by the ECU 150, the ratio R is recalculated. Only if the ratio R is zero during the first predetermined time tPDT1, at step 304e, the ECU 150 calculates a time period t. The time period t is indicative of the phase shift ᶲ of the second lambda sensor. In fact, the time period t represents the phase shift ᶲ of the second lambda sensor.
[066] Referring to Figure 5, the ratio R between the second signal and the first signal shows multiple peaks, thereby indicating the ratio being noisy. The noise depicted in the ratio R is due to the noise in the second signal and the first signal. In the present context, noise refers to an unwanted disturbance in the signals. Therefore, to overcome the noise in the signals, quantization of the ratio R is done, as shown in Figure 6. Here, the ratio R is filtered, and the moving average filtering of the ratio R is plotted against time. The “average” plotted in the graph shown in Figure 6 is the moving average filtered value of the ratio R. Prior to moving average filtering, the ratio R has a significant range of values, for instance in between 0 to 15. After the moving average, the ratio R ranges between 0 to 3.
[067] In this regard, Figure 7 shows the quantized value of R (referred as “flag” in the graph). As discussed hereinbefore, the quantization of the ratio is done to reduce the sensitivity of the first lambda sensor 120 and the second lambda sensor 140 towards noise. For this, the ratio R near the lower threshold value RLT are brought down to zero and the ratio R around 1 or in between the lower threshold value RLT and the upper threshold value RUT is set to 1. Further, the ratio R beyond the upper threshold value RUT is set to 2. The time period t during which the ratio R remains 0 indicates the phase shift ᵠ value of the second lambda sensor. Refer the phase shift ᵠ values of (t3-t2) seconds, (t6-t5) seconds, and (t9-t8) seconds shown in Figure 7.
[068] Referring to Figure 3c which shows the detailed steps for estimating the age of the catalytic converter 110. At step 305a, the estimation module 150a predicts the age of the catalytic converter 110 based on the operating condition and the phase shift ᵠ values obtained in steps 303 and 304, respectively.
[069] Based on the operating condition and the phase shift ᵠ values obtained hereinbefore, the predicted age of the catalytic converter 110 by the estimation module 150 is checked against a threshold age of the catalytic converter 110. If the predicted age is less than or equal to the threshold age, the ECU 150 continuously predicts the age of the catalytic converter with new operating condition and the phase shift ᵠ values. However, if the predicted age is more than the threshold age, as shown in step 305b, the ECU 150 illuminates the malfunction indicator light 170, thereby indicating that the catalytic converter 110 has aged and should be replaced now.
[070] For this, specific monitors are designed and coupled with the controller 150. For instance, the specific monitor could be an onboard diagnostics II (OBD-II) dashboard. The (OBD-II) dashboard is also coupled with other subsystems of the vehicle and indicates via the malfunction indicator light 170 as to the age of the catalytic converter 110.
[071] Advantageously, the present invention allows estimation of the age of the catalytic converter for any operating condition of the vehicle and is no longer limited to idling condition and/or cruising condition only. Hence, the estimation can be made at any driving condition of the vehicle.
[072] Further, the fact that the present invention obtains the data (such as engine speeds and intake manifold pressures) over the rolling window of time ensures that the ECU 150 has a minimum set of data available at all times and therefore, the overall system is computationally efficient or not computationally intensive. This also results in reduced manufacturing cost and maintenance cost of the ECU 150, which is easy to implement and less vulnerable to faults.
[073] Moreover, the present invention also takes into account any noise in the signals generated by the first lambda sensor 120 and the second lambda sensor 140, thereby providing an accurate and precise estimation of the age.
[074] The present invention estimates the age of the catalytic converter using the estimation module 150a in the ECU 150. Since the estimation module 150a is rigorously trained with huge amounts of data, the predicted age is much more accurate than the conventional systems not employing such an estimation module.
[075] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.