Method and apparatus for inferring barometric pressure surrounding an internal combustion engine

• US 5,136,517 A
• Filed: 09/12/1990
• Issued: 08/04/1992
• Est. Priority Date: 09/12/1990
• Status: Expired due to Term

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Motor Company
• Inventors: Vann, Benny, Armitage, John F., Cullen, Michael J.
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): AUCHTERLONIE, THOMAS
• Application Number:
  US07/582,704
• Time in Patent Office: 692 Days
• Field of Search: 364/431.04, 364/431.05, 364/431.06, 364/558, 364/571.01, 364/571.07, 73/117.3, 73/116, 73/115, 73/118.2, 123/494, 123/478
• US Class Current: 701/103
• CPC Class Codes: F02D 2200/704 Estimation of atmospheric pressure
• CPC Class Codes: F02D 41/04 Introducing corrections for particular operating conditions F02D41/14 takes precedence
• CPC Class Codes: F02D 41/18 by measuring intake air flow

Abstract

A mass airflow based control system for an internal combustion engine is provided which is capable of inferring barometric pressure surrounding the engine. The control system determines the air charge going into the engine from a measured value of mass airflow, and compares this value with a predicted value of air charge going into the engine, which the control system infers. Differences between the two values are first attributed to inlet air temperature, which is measured, and then to a change in barometric pressure, which is the inferred barometric pressure.

Claims

1. A method for controlling the operation of an internal combustion engine comprising the steps of:

measuring air mass flow entering said engine;

measuring the temperature of air entering said engine;

storing predetermined data which is representative of predicted air mass flow inducted into said engine at a standard pressure and temperature;

deriving from said predetermined data a first value which comprises predicted air mass flow inducted into said engine at the standard pressure and temperature;

determining barometric pressure surrounding said engine by inferring said barometric pressure in response to said measured air mass flow, said first value and said measured air temperature, said step of inferring said barometric pressure comprises the step of solving the following equation;

##EQU12## wherein BP is said inferred barometric pressure;

Ca comprises said measured air mass flow inducted into said engine;

Ci is said first value comprising predicted air mass flow inducted into said engine;

T is said measured air temperature;

Sp is equal to the standard pressure; and

St is equal to the standard temperature; and

controlling the operation of said engine by employing said determined barometric pressure.

2. A method for controlling the operation of an internal combustion engine comprising the steps of:

measuring air mass flow entering said engine;

measuring the temperature of air entering said engine;

storing predetermined data which is representative of predicted air mass flow inducted into said engine at a standard pressure and temperature;

deriving from said predetermined data a first value which is representative of predicted air mass flow inducted into said engine at the standard pressure and temperature, said first value comprising predicted air charge inducted into said engine;

deriving a second value which comprises the actual air charge entering said engine from said measured air mass flow;

determining barometric pressure surrounding said engine by inferring said barometric pressure in response to said first value, said second value and said measured air temperature, said step of inferring said barometric pressure comprises the step of solving the following equation;

##EQU13## wherein BP is said inferred barometric pressure;

Ca comprises said second value;

Ci is said first value comprising predicted air charge inducted into said engine;

T is said measured air temperature;

Sp is equal to the standard pressure; and

St is equal to the standard temperature; and

controlling the operation of said engine by employing said determined barometric pressure.

3. A method for controlling the operation of an internal combustion engine having an intake manifold, a throttle valve positionable over a given angular range, an EGR valve capable of allowing a variable amount of exhaust gases to recirculate into said intake manifold, and an air bypass valve operable over a given air bypass valve duty cycle range, said method comprising the steps of:

measuring air mass flow entering said intake manifold;

measuring the temperature of air entering said intake manifold;

storing first predetermined data which comprises predicted air mass flow inducted into said intake manifold via said throttle valve with 0 exhaust gases flowing into said intake manifold through said EGR valve;

storing second predetermined data which is indicative as predicted air mass flow which is prevented from passing into said intake manifold due to exhaust gases flowing into said intake manifold through said EGR valve;

storing third predetermined data which is representative of predicted air mass flow inducted into said intake manifold via said air bypass valve;

deriving from said first predetermined data a first values which comprises predicted air mass flow inducted into said intake manifold via said throttle valve with 0 exhaust gases flowing into said intake manifold;

deriving from said second predetermined data a second value indicative of predicted air mass flow which is prevented from passing into said intake manifold due to exhaust gases flowing into said manifold via said EGR valve;

deriving from said third predetermined data a third value which comprises predicted air mass flow inducted into said intake manifold via said air bypass valve;

deriving a fourth value from said first, second and third values which comprises predicted air mass flow inducted into said intake manifold via said throttle valve and said air bypass valve;

determining barometric pressure surrounding said engine by inferring said barometric pressure in response to said measured air mass flow, said fourth value and said measured air temperature, said step of inferring said barometric pressure comprises the step of solving the following equation;

##EQU14## wherein BP is said inferred barometric pressure;

Ca comprises said measured air mass flow inducted into said intake manifold;

Ci is said fourth value comprising predicted air mass flow inducted into said intake manifold;

T is said measured air temperature;

Sp is equal to a standard pressure; and

St is equal to a standard temperature; and

controlling the operation of said engine by employing said determined barometric pressure.

4. A method for controlling the operation of an internal combustion engine having an intake manifold, a throttle valve positionable over a given angular range, an EGR valve capable of allowing a variable amount of exhaust gases to recirculate into said intake manifold, and an air bypass valve operable over a given air bypass valve duty cycle range, said method comprising the steps of:

measuring air mass flow entering said intake manifold;

measuring the temperature of air entering said intake manifold;

storing first predetermined data which comprises predicted air charge inducted into said intake manifold via said throttle valve with 0 exhaust gases flowing into said intake manifold through said EGR valve;

storing second predetermined data which is indicative of predicted air charge which is prevented from passing into said intake manifold due to exhaust gases flowing into said intake manifold through said EGR valve;

storing third predetermined data which is representative of predicted air mass flow inducted into said intake manifold via said air bypass valve;

deriving from said first predetermined data a first value which comprises predicted air charge inducted into said intake manifold via said throttle valve with 0 exhaust gases flowing into said intake manifold;

deriving from said second predetermined data a second value indicative of predicted air charge which is prevented from passing into said intake manifold due to exhaust gases flowing into said manifold via said EGR valve;

deriving from said third predetermined data a third value which comprises predicted air mass flow inducted into said intake manifold via said air bypass valve;

deriving a fourth value from said first, second and third values which comprises predicted air charge inducted into said intake manifold via said throttle valve and said air bypass valve;

deriving a fifth value which comprises the actual air charge entering said intake manifold from said measured air mass flow;

determining barometric pressure surrounding said engine by inferring said barometric pressure surrounding said engine in response to said fourth value, said fifth value and said measured air temperature, said step of inferring said barometric pressure comprises the step of solving the following equation;

##EQU15## wherein BP is said inferred barometric pressure;

Ca comprises said fifth value;

Ci is said fourth value comprising predicted air charge inducted into said intake manifold;

T is said measured air temperature;

Sp is equal to a standard pressure; and

St is equal to a standard temperature; and

controlling the operation of said engine by employing said determined barometric pressure.

5. A system for controlling the operation of an internal combustion engine comprising:

means for measuring air mass flow entering said engine;

means for measuring the temperature of air entering said engine;

processor means connected to said air mass flow measuring means and said air temperature measuring means for receiving inputs of said air mass flow and said air temperature, for storing predetermined data which is representative of predicted air mass flow inducted into said engine at a standard pressure and temperature, for deriving from said predetermined data a first value which comprises predicted air mass flow inducted into said engine at the standard temperature and pressure, for inferring barometric pressure surrounding said engine in response to said measured air mass flow input, said first value and said measured temperature input, and for controlling the operation of said internal combustion engine by employing said inferred barometric pressure; and

, wherein

said processor means infers said barometric pressure by solving the following equation;

##EQU16## wherein BP is said inferred barometric pressure;

Ca comprises said measured air mass flow inducted into said engine;

Ci is said first value comprising predicted air mass flow inducted into said engine;

T is measured air temperature;

Sp is equal to the standard pressure; and

St is equal to the standard temperature.

6. A system for controlling the operation of an internal combustion engine comprising:

means for measuring air mass flow entering said engine;

means for measuring the temperature of air entering said engine;

processor means connected to said air mass flow measuring means and said air temperature measuring means for receiving inputs of said air mass flow and said air temperature, for storing predetermined data which is representative of predicted air mass flow inducted into said engine at a standard pressure and temperature, for deriving from said predetermined data a first value which comprises predicted air charge inducted into said engine at the standard pressure and temperature, for deriving a second value which comprises the actual air charge entering said engine from said measured air mass flow, for inferring barometric pressure surrounding said engine in response to said firs value, said second value and said measured temperature input, and for controlling the operation of said internal combustion engine by employing said inferred barometric pressure; and

, wherein `said processor means infers said barometric pressure by solving the following equation;

##EQU17## wherein BP is said inferred barometric pressure;

Ca comprises said second value;

Ci is said first value comprising predicted air charge inducted into said engine;

T is said measured air temperature;

Sp is equal to the standard pressure; and

St is equal to the standard temperature.

7. A control system for controlling the operation of a motor vehicle internal combustion engine including an intake manifold, a throttle valve positionable over a given angular range, an EGR valve capable of allowing a variable amount of exhaust gases to recirculate into said intake manifold, and an air bypass valve operable over a given air bypass valve duty cycle range said system being capable of inferring barometric pressure surrounding said engine and comprising:

means for measuring the rotational speed of said internal combustion engine;

means for measuring the angular position of said throttle valve;

means for measuring air mass flow entering said intake manifold;

means for measuring the temperature of air entering said intake manifold;

derivation means being connected to said engine speed measuring means, said throttle valve position measuring means, said air mass flow measuring means and said air temperature measuring means for receiving inputs of said engine speed, said throttle valve angular position, said air mass flow and said air temperature;

said derivation means including memory means for storing predetermined data in a first look-up table which is representative of predicted air mass flow inducted into said intake manifold via said throttle valve with 0 exhaust gases flowing into said intake manifold through said EGR valve as a function of a first portion of said inputs, storing predetermined data in a second look-up table which is indicative of predicted air mass flow which is prevented from passing into said intake manifold due to exhaust gases flowing into said manifold through said EGR valve as a function of a first portion of said inputs, and storing predetermined data in a third look-up table which is representative of predicted air mass flow inducted into said intake manifold via said air bypass valve as a function of the air bypass valve duty cycle and a ratio of predicted current air charge going into said engine to predicted peak air charge capable of going into said engine; and

said derivation means deriving a first value representative of predicted air mass flow inducted into said intake manifold via said throttle valve with 0 exhaust gases flowing into said intake manifold by comparing said first portion of said inputs with said predetermined data stored in said first look-up table, deriving a second value indicative of predicted air mass flow which is prevented from passing into said intake manifold due to exhaust gases flowing into said manifold through said EGR valve by comparing said first portion of said inputs with said predetermined data stored in said second look-up table, deriving a third value representative of predicted air mass flow inducted into said intake manifold via said air bypass valve in response to said air bypass valve duty cycle, said ratio of predicted current air charge going into said engine to predicted peak air charge and said third look-up table, and deriving a fourth value from said first, second and third values which is representative of predicted air mass flow inducted into said intake manifold via said throttle valve and said air bypass valve;

said derivation means inferring said barometric pressure surrounding said engine in response to said fourth value and a second portion of said inputs; and

said derivation means controlling the operation of the internal combustion engine by employing said inferred barometric pressure.

8. A control system as set forth in claim 7, wherein said first portion of said inputs comprises said engine speed input and said throttle valve angular position input, and said second portion of said inputs comprises said air mass flow input and said air temperature input.