Real time pull-slip curve modeling in large track-type tractors

• US 8,983,739 B2
• Filed: 11/30/2012
• Issued: 03/17/2015
• Est. Priority Date: 11/30/2012
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Faivre, Joseph
• Primary Examiner(s): Nguyen, John Q
• Assistant Examiner(s): SMITH, AARON C
• Application Number:
  US13/691,010
• Publication Number:
  US 20140156153A1
• Time in Patent Office: 837 Days
• Field of Search: 701/50, 701/82, 701/84, 701/151, 305/111, 305/136, 305/170, 305/114, 180/9.21, 180/197, 180/361, 172/1, 172/2
• US Class Current: 701/50
• CPC Class Codes: G07C 5/0808 Diagnosing performance data testing of vehicles G01M17/00; testing of electrical installation on vehicles G01R31/005
• CPC Class Codes: G07C 5/0841 Registering performance data recording measured values G01D; information storage G11B

Abstract

A method of estimating soil conditions of a work surface during operation of a track-type tractor measures current operating conditions and current operating state to develop adjustments to a nominal pull-slip curve. The adjusted pull-slip curve is used to calculate optimum performance in terms of an input variable such as track speed. Two factors are developed to reflect soil conditions, coefficient of traction and a shear modulus adjustment that affect different portions of the nominal pull slip curve.

Claims

1. A track-type tractor adapted to characterize soil conditions during operation, the track-type tractor comprising:

a slope sensor that provides a slope of the track-type tractor;

a track speed sensor that provides a track speed of the track-type tractor;

a processor coupled to the slope sensor and the track speed sensor; and

a memory coupled to the processor, the memory storing a plurality of modules that when executed by the processor, cause the processor to;

access a nominal pull-slip curve stored in the memory;

store data received from the slope sensor and the track speed sensor;

collect a plurality of samples of drawbar pull over a period of time;

calculate an instantaneous pull-weight ratio as a function of drawbar pull, rolling resistance, and slope for each of the plurality of samples of drawbar pull to generate a plurality of pull-weight ratios;

calculate a coefficient of traction(COT) from the plurality of instantaneous pull-weight ratios;

divide values of the nominal pull-slip curve by the COT to produce a normalized pull-slip curve;

determine an optimum operating state defined as the highest possible value of cycle power of the track-type tractor using the calculated COT, the normalized pull-slip curve, and the slope; and

provide the optimum operating state and a current operating point to a device for use in adjusting one or more operational settings of affecting the operating state of the track-type tractor.

2. The track-type tractor of claim 1, wherein the plurality of modules cause the processor to calculate the coefficient of traction by calculating the plurality of instantaneous pull-weight ratios (PW_ratio) as

(Drawbar Pull−

Rolling Resistance)/(machine mass*gravity*cos θ

_pitch).

3. The track-type tractor of claim 2, wherein the plurality of modules cause the processor to:

retain only instantaneous pull-weight ratios that meet all of;

data is taken while in a forward gear;

a track slip is greater than 20%;

no steering activity;

no brake activity;

deceleration pedal not activated; and

each of the instantaneous pull-weight ratios must be in a range of a minimum of about 0.5 to a maximum of about 1.2.

4. The track-type tractor of claim 3, wherein the plurality of modules cause the processor to:

perform a validation test to determine that the plurality of instantaneous pull-weight ratios meet a data population criteria and a convergence criteria.

5. The track-type tractor of claim 4, wherein the plurality of modules cause the processor to:

offset the COT by a multiple of a standard deviation to account for a population bias at a low end of a slip range.

6. The track-type tractor of claim 1, wherein the plurality of modules further cause the processor to:

develop a shear modulus adjustment factor to characterize soil conditions from pull-weight ratios observed at a slip percentage in a second range that partially overlies the first range.

7. The track-type tractor of claim 6, wherein the second range is about 0.5% to about 40%.

8. The track-type tractor of claim 6, wherein the plurality of modules cause the processor to:

calculate the shear modulus adjustment factor using a plurality of normalized pull-weight ratios (r_pw) as

9. A method of characterizing soil conditions during operation of a track-type tractor, the method comprising:

providing a nominal pull-slip curve corresponding to a standard soil condition;

receiving, at a processor, data from at least one sensor of the track-type tractor, the data corresponding to a slope of the track-type tractor and one or more of a track speed, a ground speed, and a drawbar pull;

producing, at the processor, a coefficient of traction (COT), wherein producing the COT includes;

calculating a plurality of instantaneous pull-weight ratio values using the drawbar pull and the slope;

removing instantaneous pull-weight ratio values from the plurality of instantaneous pull-weight ratio values that fail to meet a first screening criteria; and

averaging the instantaneous pull-weight ratio values that meet the first screening criteria to produce the COT;

normalizing, at the processor, the nominal pull-slip curve by the COT to produce a normalized pull-slip curve;

producing, at the processor, a shear modulus adjustment factor that characterizes soil conditions, wherein producing the shear modulus adjustment factor includes;

calculating a plurality of normalized pull-weight ratio values;

removing normalized pull-weight ratio values that fail to meet a second screening criteria;

calculating the shear modulus adjustment factor from the normalized pull-weight ratio values meeting the second screening criteria;

applying the shear modulus adjustment factor to the normalized pull-slip curve to obtain an adjusted pull-slip curve; and

using the adjusted pull-slip curve, the COT, and the slope to determine an optimum performance; and

providing the optimum performance to a device for use in adjusting a current operating state of the track-type tractor to reach the optimum performance.

10. The method of claim 9, further comprising performing a validation test on each of the plurality of instantaneous pull-weight ratio values that meet the first screening criteria to determine that the plurality of instantaneous pull-weight ratio values meet a data population criteria and a convergence criteria.

11. The method of claim 9, wherein removing instantaneous pull-weight ratio values that fail to meet the first screening criteria comprises removing the instantaneous pull-weight ratio values that fail any of:

data is taken while in a forward gear;

a track slip is greater than 20%;

no steering activity;

no brake activity;

deceleration pedal not activated;

must be in a range of a minimum of about 0.5 to a maximum of about 1.2.

12. The method of claim 11, further comprising offsetting the COT by a multiple of a standard deviation to account for a population bias at a low end of a range of track slip.

13. The method of claim 9, wherein normalizing the nominal pull-slip curve by the COT comprises dividing each point on the nominal pull-slip curve by the COT.

14. The method of claim 9, wherein calculating each of the plurality of normalized pull-weight ratio values (r_pw) comprises calculating

15. The method of claim 9, wherein removing normalized pull-weight ratio (r_pw) values that fail to meet the second screening criteria comprises removing the normalized pull weight ratio values that fail any of:

data is taken while in a forward gear;

track acceleration is less than approximately 50 mm/s²;

track slip is in a track slip range of a minimum of about 0.5% to a maximum of about 40%;

a COT value must have been successfully developed;

the ground speed must be available;

no steering activity;

no brake activity;

deceleration pedal not activated.

16. The method of claim 15, wherein calculating the shear modulus adjustment factor (k_adj) comprises fitting an estimated slip (s′

) to a measured slip (s) based on the inverse function of the normalized pull-slip curve over the normalized pull-weight ratio values meeting the second screening criteria using a data fitting technique.

17. The method of claim 16, wherein determining the estimated slip of the tracks at any normalized pull weight ratio (r_pw) comprises performing a calculation of (f⁻

1 (r_pw))*k_adj), where f<sup>−

1</sup> is the inverse function of the normalized pull-slip curve.

18. A method of characterizing soil conditions during operation of a track-type tractor implemented by execution of computer-executable instructions stored on a computer readable memory storing computer-executable instructions, the method comprising:

providing a nominal pull-slip curve corresponding to a standard soil condition;

receiving, at a processor, data from at least one sensor of the track-type tractor, the data corresponding to a slope of the track-type tractor and one or more of a track velocity, a ground speed, and a drawbar pull;

producing, at the processor, a coefficient of traction (COT), wherein producing the COT includes;

calculating a plurality of instantaneous pull-weight ratios using the drawbar pull and the slope;

removing from the plurality of instantaneous pull-weight ratios the instantaneous pull-weight ratios that fail to meet a first screening criteria, the first screening criteria including removing the instantaneous pull-weight ratios corresponding to a slip value less than 20%; and

averaging the instantaneous pull-weight ratios that meet the first screening criteria to produce the COT;

normalizing, at the processor, the nominal pull-slip curve by the COT to produce a normalized pull-slip curve;

producing, at the processor, a shear modulus adjustment factor, wherein producing the shear modulus adjustment factor includes;

calculating a plurality of normalized pull-weight ratio values;

removing normalized pull-weight ratio values that fail to meet a second screening criteria, the second screening criteria including removing the normalized pull-weight ratio values corresponding to a slip outside a range of about 0.5% to about 40%;

calculating the shear modulus adjustment factor from the normalized pull-weight ratio values meeting the second screening criteria;

applying the shear modulus adjustment factor to the normalized pull-slip curve to obtain an adjusted pull-slip curve; and

using the adjusted pull-slip curve, the COT, and the slope to determine an optimum performance; and

providing the optimum performance to a device for use in adjusting an operating state of the track-type tractor to achieve a performance closer to the optimum performance.

19. The method of claim 18, further comprising:

collecting a minimum of about 300 pull-weight ratio values that meet the first screening criteria to produce the COT;

collecting a minimum of about 800 of the normalized pull-weight ratio values that meet the second screening criteria to produce the shear modulus adjustment factor.

20. The method of claim 19, further comprising:

collecting additional normalized pull-weight ratio values;

producing two additional shear modulus adjustment factors; and

averaging the three shear modulus adjustment factors to produce a final shear modulus adjustment factor used in further calculations.