On-line catalyst monitoring using a kalman filter

• US 20050267669A1
• Filed: 05/26/2004
• Published: 12/01/2005
• Est. Priority Date: 05/26/2004
• Status: Active Grant

• Current Assignee: FCA US LLC (Stellantis NV)
• Original Assignee: Daimler Chrysler Corporation (Mercedes-Benz Group AG)
• Inventors: Wang, Wei, Lee, Anson
• Granted Patent: US 7,043,899 B2
• Time in Patent Office: Days
• US Class Current: 701/102
• CPC Class Codes: F01N 11/00 Monitoring or diagnostic devices for exhaust-gas treatment apparatus , e.g. for catalytic activity safety, indicating or supervising devices for internal combustion engines F02B77/08; testing of machines G01M13/00
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: F02D 2041/1417 Kalman filter
• CPC Class Codes: F02D 2200/0814 Oxygen storage amount
• CPC Class Codes: F02D 41/0235 in relation with the state of the exhaust gas treating apparatus control of exhaust gas treating apparatus per se F01N
• CPC Class Codes: F02D 41/1441 Plural sensors
• CPC Class Codes: F02D 41/1456 with sensor output signal being linear or quasi-linear with the concentration of oxygen
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A method of non-intrusive monitoring of catalyst performance in an automotive exhaust system uses a model of catalytic converter operation emphasizing oxygen storage capacity dominance. Model parameters are identified using a recursive Kalman filtering technique. A catalyst diagnostic index is derived from at least one identified parameter, and the index is used to judge converter performance.

Claims

1. A method of on-line, non-intrusive monitoring of a catalytic converter, the method comprising:

modeling dynamic behavior of a catalytic converter using an oxygen storage dominant model;

identifying parameters in the model using a recursive Kalman filtering technique;

deriving a catalyst diagnostic index from a preselected parameter of the model; and

using the index to judge performance of the catalytic converter.

2. The method of claim 1 wherein the storage dominant model is described by an auto-regressive moving average equation.

3. The method of claim 2 wherein the preselected parameter comprises a pole of the auto-regressive moving average equation.

4. The method of claim 3 wherein the pole is directly related to a catalyst conversion rate.

5. The method of claim 3 wherein the pole comprises a dominant pole of the equation.

6. The method of claim 1 wherein the performance of the catalytic converter is judged acceptable whenever the index is less than a predetermined threshold value.

7. The method of claim 2 wherein the equation is

y(k)=a₁y(k−

1)+b₁u(k−

1)+b₂u(k−

2)+. . . +b_nu(k−

n)+v(k)

where

u represents the upstream relative equivalent air/fuel ratio which is input to the system or catalyst;

y represents the downstream relative equivalent air/fuel ratio which is the output from the system;

a₁ and b₁,b₂, . . . ,b_n are the coefficients of the model;

k is the discrete time step;

n represents the time delay step for the input; and

v is the measurement noise.

8. The method of claim 7 wherein the preselected parameter is a₁, and the index is derived by taking the absolute value of a₁.

9. The method of claim 7 wherein the absolute value of a₁ ranges in value from zero to one and wherein the performance of the catalytic converter is judged acceptable whenever the absolute value of a₁ is less than an experimentally determined threshold value between zero and one.