Three-way catalyst model for an engine air-to-fuel ratio control system

• US 6,336,084 B1
• Filed: 05/11/1999
• Issued: 01/01/2002
• Est. Priority Date: 05/11/1999
• Status: Expired due to Fees

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Omara, Ahmed Abdelaziz, Bradley, John Edward, Hamburg, Douglas Ray
• Primary Examiner(s): Teska, Kevin J.
• Assistant Examiner(s): JONES, HUGH M
• Application Number:
  US09/309,779
• Time in Patent Office: 966 Days
• Field of Search: 703/8, 602/74
• US Class Current: 703/8
• CPC Class Codes: F01N 9/005 using models instead of sensors to determine operating characteristics of exhaust systems, e.g. calculating catalyst temperature instead of measuring it directly
• CPC Class Codes: F02D 2041/1411 using a finite or infinite state machine, automaton or state graph for controlling or modelling
• CPC Class Codes: F02D 2041/1415 using a state feedback or a state space representation
• CPC Class Codes: F02D 2041/1423 Identification of model or controller parameters
• CPC Class Codes: F02D 2041/1433 using a model or simulation of the system
• CPC Class Codes: F02D 2041/1436 Hybrid model
• 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 41/1401 characterised by the control or regulation method F02D41/1473, F02D41/1477 take precedence
• CPC Class Codes: F02D 41/1441 Plural sensors
• CPC Class Codes: F02D 41/1458 with determination means using an estimation
• CPC Class Codes: F02D 41/187 using a hot wire flow sensor
• CPC Class Codes: F02D 41/2454 Learning of the air-fuel ratio control
• CPC Class Codes: G05B 17/02 electric
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A three-way catalyst model (50) and a method for modeling the dynamic response of a three-way catalyst that divides the catalyst response into sub-regions (1-7) . A sub-model (44) is constructed that represents each sub-region (1-7) . Each sub-model (44) is assigned unique attributes at which the sub-model is activated. The attributes are based on the system parameters and states. The states may be either continuous or discrete and define a hybrid state space. A larger or smaller number of sub-regions (1-7) can be utilized based on the model'"'"'s (50) use and the accuracy desired for the model (50).

Claims

1. A method for computer modeling a dynamic system for a three-way catalyst to control an air-to-fuel ratio in an internal combustion engine, the three-way catalyst having a system response, said method comprising the steps of:

dividing the system response into a plurality of separate and distinct sub-regions by isolating dynamic phenomena in the system response;

assigning attributes to each of said plurality of sub-regions based on parameters of said three-way catalyst system;

generating a sub-model for each of said plurality of sub-regions using the assigned attributes, the sub-model being a mathematical representation of a corresponding sub-region;

activating the sub-model for a corresponding sub-region when each and every attributed assigned to the corresponding sub-region is true, and wherein no two sub-regions are simultaneously active, thereby defining discrete states for each sub-region of the system response;

controlling the air-to-fuel ratio based on said active sub-model.

2. The method as claimed in claim 1 wherein said step of dividing the system response further comprises:

defining a first sub-region representing three-way catalyst behavior during a pre-catalyst rich air-to-fuel ratio and a post-catalyst stoichiometric air-to-fuel ratio;

defining a second sub-region representing three-way catalyst behavior during a post-catalyst rich air-to-fuel ratio and a lean pre-catalyst air-to-fuel ratio and wherein a reducing species is released from storage;

defining a third sub-region representing three-way catalyst behavior during a post catalyst rich air-to-fuel ratio and a lean pre-catalyst air-to-fuel ratio and wherein an oxidizing species is stored; and

defining a fourth sub-region representing three-way catalyst behavior during periods when a stored oxidizing species is above predetermined limit value, the pre-catalyst air-to-fuel ratio is lean, and the three-way catalyst is not lean saturated.

3. The method as claimed in claim 1 further comprising the steps of:

defining a fail-safe sub-model;

activating said fail-safe sub-model during periods of time when no other sub-model corresponding to a sub-region is active.