A METHOD OF DETERMINING AMBIENT AIR TEMPERATURE

• US 20060209921A1
• Filed: 03/16/2005
• Published: 09/21/2006
• Est. Priority Date: 03/16/2005
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Brown, Kenneth, Kyrtsos, Christos, Hernandez, Esteban
• Granted Patent: US 7,387,437 B2
• Time in Patent Office: Days
• US Class Current: 374/109
• CPC Class Codes: G01K 1/20 Compensating for effects of temperature changes other than those to be measured, e.g. changes in ambient temperature
• CPC Class Codes: G01K 3/00 Thermometers giving results other than momentary value of temperature G01K7/42 takes precedence
• CPC Class Codes: G01K 7/42 Circuits effecting compensation of thermal inertia; Circuits for predicting the stationary value of a temperature

Abstract

A method of predicting ambient air temperature outside a passenger compartment of a vehicle. The method measures air temperature with a temperature sensor, applies a correction strategy, and determines a predicted temperature value.

Claims

1. A method of determining air temperature outside a passenger compartment of a vehicle, the vehicle including first and second temperature sensors disposed outside the passenger compartment, the method comprising:

measuring air temperature with the first temperature sensor to produce a first measured temperature value;

measuring air temperature with the second temperature sensor to produce a second measured temperature value;

applying a correction strategy to the first and second measured temperature values to determine first and second predicted temperature values, respectively; and

calculating a predicted ambient air temperature value based on the first and second predicted temperature values.

2. The method of claim 1 wherein the predicted air temperature value is determined as a function of the expression

T_Predicted=(T1_Predicted+T2_Predicted)/2

where:

T_Predicted is the predicted ambient air temperature value,

T1_Predicted is the first predicted temperature value, and

T2_Predicted is the second predicted temperature value.

3. The method of claim 1 wherein the predicted ambient air temperature value is determined as a function of the expression

T_Predicted=C1*T1_Predicted+C2*T2_Predicted

where:

C1 and C2 are values between 0 and 1 selected such that C1+C2=1,

T_Predicted is the predicted ambient air temperature value,

T1_Predicted is the first predicted temperature value, and

T2_Predicted is the second predicted temperature value.

4. The method of claim 1 wherein the step of applying the correction strategy further comprises setting the first predicted temperature value equal to the first measured temperature value when

heating from a non-ambient heat source is predicted and either

the first measured temperature value is less than a previous first measured temperature value and a speed of the vehicle is greater than a threshold speed value, or

the first measured temperature value is not less than a previous first measured temperature value, the speed of the vehicle is not greater than the threshold speed value, and the first measured temperature value is not increasing rapidly;

or

heating from a non-ambient heat source is not predicted.

5. The method of claim 1 wherein the step of applying the correction strategy further comprises setting the second predicted temperature value equal to the second measured temperature value when

heating from a non-ambient heat source is predicted and either

the second measured temperature value is less than a previous second measured temperature value and a speed of the vehicle is greater than a threshold speed value, or

the second measured temperature value is not less than a previous second measured temperature value, the speed of the vehicle is not greater than the threshold speed value, and the second measured temperature value is not increasing rapidly;

or

heating from a non-ambient heat source is not predicted.

6. The method of claim 1 wherein the step of applying the correction strategy further comprises setting the first predicted temperature value equal to the first measured temperature value and increasing the first predicted temperature value at a predetermined rate when

heating from a non-ambient heat source is predicted, and

the first measured temperature value is not less than a previous first measured temperature value, and

a speed of the vehicle is greater than a threshold speed value.

7. The method of claim 1 wherein the step of applying the correction strategy further comprises setting the second predicted temperature value equal to the second measured temperature value and increasing the second predicted temperature value at a predetermined rate when

heating from a non-ambient heat source is predicted, and

the second measured temperature value not is less than a previous second measured temperature value, and

a speed of the vehicle is greater than a threshold speed value.

8. The method of claim 1 wherein the step of applying the correction strategy further comprises calculating the first predicted temperature value based on a moving average of sequential first measured temperature values when heating from a non-ambient heat source is predicted and either

the first measured temperature value is less than a previous first measured temperature value, a speed of the vehicle is not greater than a threshold speed value, and the first measured temperature value is not decreasing rapidly, or

the first measured temperature value is not less than a previous first measured temperature value, the speed of the vehicle is not greater than the threshold speed value, and the first measured temperature value is increasing rapidly.

9. The method of claim 1 wherein the step of applying the correction strategy further comprises calculating the second predicted temperature value based on a moving average of sequential second measured temperature values when heating from a non-ambient heat source is predicted and either

the second measured temperature value is less than a previous second measured temperature value, a speed of the vehicle is not greater than a threshold speed value, and the second measured temperature value is not decreasing rapidly, or

the second measured temperature value is not less than a previous second measured temperature value, the speed of the vehicle is not greater than the threshold speed value, and the second measured temperature value is increasing rapidly.

10. The method of claim 1 wherein the step of applying the correction strategy further comprises calculating the first predicted temperature value with an exponential correction formula when heating from a non-ambient heat source is predicted and either

the first measured temperature value is less than a previous first measured temperature value, a speed of the vehicle is not greater than a threshold speed value, and the first measured temperature value is not decreasing rapidly, or

the first measured temperature value is not less than a previous first measured temperature value, the speed of the vehicle is not greater than the threshold speed value, and the first measured temperature value is increasing rapidly.

11. The method of claim 1 wherein the step of applying the correction strategy further comprises calculating the second predicted temperature value with an exponential correction formula when heating from a non-ambient heat source is predicted and either

the second measured temperature value is less than a previous second measured temperature value, a speed of the vehicle is not greater than a threshold speed value, and the second measured temperature value is not decreasing rapidly, or

the second measured temperature value is not less than a previous second measured temperature value, the speed of the vehicle is not greater than the threshold speed value, and the second measured temperature value is increasing rapidly.

12. The method of claim 1 wherein the step of applying a correction strategy to the first and second measured temperature values to determine first and second predicted temperature values is determined using an exponential correction formula that as a function of the expression

13. A method of predicting ambient air temperature outside a passenger compartment of a vehicle, the vehicle including a temperature sensor, the method comprising:

predicting whether heat from a non-ambient heat source is increasing air temperature proximate the temperature sensor; and

calculating a predicted temperature value with a correction expression when non-ambient heating is likely and a speed of the vehicle is not greater than a threshold value, or when non-ambient heating is not likely and the measured temperature value is stable.

14. The method of claim 13 wherein the predicted temperature value is set equal to a previous temperature value when non-ambient heating is not likely and the measured temperature value is not stable.

15. The method of claim 14 wherein the correction expression is an exponential correction formula is based on a non-linear regression analysis.

16. The method of claim 15 wherein the exponential correction formula is based on the expression:

T_Predicted=C_Average when |C_i−

C_Average|<

C_Threshold

where;

T_Predicted is the predicted ambient air temperature,

C_Threshold is a constant between 0 and 1,

C_i is the value of parameter C from a non-linear regression analysis at time i, and

C_Average is the average of n consecutive C values based on the expression;

$\frac{\underset{i=1}{\overset{n}{\sum <br><br>}}<br><br>C_i}{n}$

where;

n is an integer indexed for each data point.

17. The method of claim 13 wherein the temperature sensor is disposed proximate an air intake manifold.

18. The method of claim 13 wherein the step of predicting whether heat from a non-ambient heat source is increasing air temperature proximate the temperature sensor includes determining whether an engine coolant temperature is greater than a threshold coolant temperature value.

19. The method of claim 13 wherein the step of predicting whether heat from a non-ambient heat source is increasing air temperature proximate the temperature sensor includes determining whether an amount of time since the engine was turned off is less than a predetermined time value.

20. A method of determining ambient air temperature outside a vehicle, the vehicle including a temperature sensor adapted to detect air temperature, the method comprising:

setting a predicted air temperature value equal to a measured temperature value provided by the temperature sensor when non-ambient heating is not likely, or when non-ambient heating is likely and either the measured temperature value is less than a previous measured temperature value and a speed of the vehicle is greater than a threshold speed value, or the measured temperature value is not less than a previous measured temperature value, the speed of the vehicle is not greater than the threshold speed value, and the measured temperature value is not increasing rapidly;

setting the predicted air temperature value equal to the measured temperature value increased at a predetermined rate when non-ambient heat source is likely, the measured temperature value is not less than the previous measured temperature value, and the vehicle speed exceeds the threshold speed value; and

calculating the predicted air temperature value using a correction expression when non-ambient heating is likely and either the measured temperature value is less than a previous measured temperature value, the speed of the vehicle is not greater than the threshold speed value, and the measured temperature value is not decreasing rapidly, or the measured temperature value is not less than the previous measured temperature value, the speed of the vehicle is not greater than the threshold speed value, and the measured temperature value is increasing rapidly.