Automotive transmission control system and method

• US 20060241841A1
• Filed: 04/20/2005
• Published: 10/26/2006
• Est. Priority Date: 04/20/2005
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Brunstetter, Craig A.
• Granted Patent: US 7,315,775 B2
• Time in Patent Office: Days
• US Class Current: 701/63
• CPC Class Codes: G01K 15/00 Testing or calibrating of thermometers
• CPC Class Codes: G01K 15/007 Testing

Abstract

The present invention is a control system and method for the determination of a simulated transmission fluid temperature value using multiple linear regression. The present invention also provides a control system and method to diagnose the health of the transmission fluid temperature sensor and provides a default transmission fluid temperature value should failure of the transmission fluid temperature sensor occur.

Claims

1. A method of determining a simulated transmission fluid temperature value comprising:

recording values for a plurality of independent variables over a plurality of driving cycles and vehicle configurations;

utilizing multiple linear regression analysis to fit a curve to a dependent variable based upon inputs from said plurality of independent variables thereby determining the respective coefficients for each one of said values of said plurality of independent variables and an intercept value;

multiplying each of said plurality of independent variables by said respective coefficients to determine the respective products;

summing said respective products and said intercept value to generate a synthetic transmission fluid temperature value; and

selecting said synthetic transmission fluid temperature value as said simulated transmission fluid temperature value if an engine run time value is greater than a calibrated simulated transmission fluid temperature delay latch value, or alternately, selecting the start up transmission fluid temperature value as said simulated transmission fluid temperature value if said engine run time is less than or equal to said calibrated simulated transmission fluid temperature delay latch value.

2. A method of diagnosing a transmission fluid temperature sensor failure comprising:

enabling diagnostic testing of the transmission fluid temperature sensor;

enabling a fail timer if the absolute value of the difference between a measured transmission fluid temperature value and a simulated transmission temperature value is greater than or equal to a calibrated transmission fluid temperature failure threshold value, said fail timer being operable to output a time to fail test value; and

setting a test failed bit if said time to fail test value is greater than or equal to a calibrated transmission fluid temperature fail timer value.

3. The method of diagnosing a transmission fluid temperature sensor failure of claim 2 further comprising:

enabling a pass timer if the absolute value of the difference between said measured transmission fluid temperature value and said simulated transmission temperature value is greater than or equal to a calibrated transmission fluid temperature pass threshold value and said test failed bit has not been set, said pass timer being operable to output a time to pass test value; and

setting a test passed bit if said time to pass test value is greater than or equal to a calibrated transmission fluid temperature pass timer value.

4. The method of diagnosing a transmission fluid temperature sensor failure of claim 2 further comprising:

outputting an offset of an engine coolant temperature value as a function of an engine inlet air temperature value as a default transmission fluid temperature value upon the setting of said test failed bit and if the absolute value of the difference between a engine start-up transmission fluid temperature sensor value and a measured transmission fluid temperature value is greater than a calibrated start-up transmission fluid temperature difference action value.

5. The method of diagnosing a transmission fluid temperature sensor failure of claim 2 further comprising:

outputting said simulated transmission fluid temperature value as said default transmission fluid temperature value when said test failed bit has not been set or when said absolute value of said difference between said engine start-up transmission fluid temperature sensor value and said measured transmission fluid temperature value is less than said calibrated start-up transmission fluid temperature difference action value.

6. A transmission control system comprising a controller operable to determine a simulated transmission fluid temperature value and diagnose the state of health of a transmission fluid temperature sensor, said controller being sufficiently configured and programmed to implement a control loop for performing the following operations:

calculating a synthetic transmission fluid temperature value;

determining and outputting a simulated transmission fluid temperature value;

enabling diagnostic testing of a transmission fluid temperature sensor;

determining the accuracy of a measured transmission fluid temperature value via a pass/fail algorithm and reporting one of a pass condition and a fail condition; and

generating a default transmission fluid temperature value if said pass/fail algorithm reports said fail condition.

7. The transmission control system of claim 6 wherein said synthetic transmission fluid temperature value is calculated by:

a plurality of multipliers, each having as inputs the value of one of a plurality of independent variables and their respective calculated multiple linear regression coefficients; and

at least one summing circuit that inputs the output values of said plurality of multipliers and an intercept value calculated by multiple linear regression, and outputs said synthetic transmission fluid temperature value.

8. The transmission control system of claim 7 wherein said plurality of independent variables includes:

at least one of engine run time, total torque converter slip, start up transmission fluid temperature, engine coolant temperature, total engine torque, and engine intake air temperature.

9. The transmission control system of claim 7 wherein said control loop for determining said simulated transmission fluid temperature value includes the following elements:

an IF/THEN/ELSE logic gate having an IF input, a THEN input, and an ELSE input, said IF/THEN/ELSE logic gate having a start up transmission fluid temperature value as said THEN input and said synthetic transmission fluid temperature value as said ELSE input, the output of said IF/THEN/ELSE logic gate is said simulated transmission fluid temperature value; and

a comparator operable to compare an engine run time value with a calibrated delay latch value and output a result to said IF input of said IF/THEN/ELSE logic gate.

10. The transmission control system of claim 6 wherein said control loop for enabling testing includes the following elements:

at least one comparator operable to enable diagnostic testing of said transmission fluid temperature sensor if the output of said at least one comparator is true based on the relationship between at least one measured value to at least one calibrated value.

11. The transmission control system of claim 6 wherein said pass/fail algorithm has a fail loop that that is implemented by:

a first summing circuit operable to output the difference between said measured transmission fluid temperature value and said simulated transmission fluid temperature value;

a first comparator operable to compare the absolute value of the difference between said measured transmission fluid temperature value and said simulated transmission fluid temperature value with a calibrated value for the transmission fluid temperature failure delta;

an AND logic gate and a fail timer, said AND logic gate being operable to input the output from said first comparator and a test enable value, and output an enable signal to said fail timer if both inputs to said AND logic gate are true;

a second comparator operable to compare the output value from said fail timer with a calibrated transmission temperature failure time value and output a result; and

a timer reset circuit operable to reset said fail timer.

12. The transmission control system of claim 6, wherein said pass/fail algorithm has a pass loop that is implemented by:

a summing circuit operable to output the difference between said measured transmission fluid temperature value and said simulated transmission fluid temperature value;

a first comparator operable to compare the absolute value of the difference between said measured transmission fluid temperature value and said simulated transmission fluid temperature value with a calibrated value for the transmission fluid temperature pass delta;

an AND logic gate and a pass timer, said AND logic gate being operable to input the output from said first comparator, the test enable value, and the inverted value of said fail condition, said AND logic gate outputs an enable signal to said pass timer if all inputs to said AND logic gate are true;

a second comparator operable to compare the output value from said pass timer with a calibrated transmission temperature pass time value and output a result; and

a timer reset circuit operable to reset said pass timer.

13. The transmission control system claim 6 wherein said control loop for determining said default transmission fluid temperature value includes the following elements:

an IF/THEN/ELSEIF logic block operable to output a default transmission fluid temperature value if said pass/fail algorithm reports as failed, said IF/THEN/ELSE logic block having an IF input, a THEN input, an ELSEIF input, a _THEN input, and an _ELSE input, where an inverted value for said fail condition is input to said IF input and the simulated transmission fluid temperature value is input to said THEN and said _THEN inputs;

a first summing circuit operable to output the difference between a start up transmission fluid temperature value and said measured transmission fluid temperature value;

a comparator operable to compare the absolute value of the difference between said start up transmission fluid temperature value and said measured transmission fluid temperature value with a calibrated start up transmission fluid temperature difference action value and outputting a result to said ELSEIF input of said IF/THEN/ELSE logic block; and

a second summing circuit operable to determine the difference between the engine coolant temperature value and a conditioned engine intake air temperature value and outputting the value to said _ELSE input of the IF/THEN/ELSE logic block.