# US 2014/0156153 A1 · Real Time Pull-Slip Curve Modeling in Large Track-Type Tractors

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- Number: US 2014/0156153 A1
- Document ID: US20140156153A1
- Status: Published application
- Kind: A1
- Application number: 13/691,010
- Filed: 2012-11-30
- Published: 2014-06-05
- Earliest claimed: 2012-11-30
- Assignees: Caterpillar Inc.
- Applicants: Caterpillar Inc.
- Inventors: Joseph Faivre
- Web page: https://patentgrep.com/patent/US20140156153A1

## CPC

- G07C 5/0841: {Registering performance data (recording measured values G01D; information storage G11B)}
- G07C 5/0808: {Diagnosing performance data (testing of vehicles G01M17/00; testing of electrical installation on vehicles G01R31/005)}
- G07C: TIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE

## 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

### Claim 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;
calculate a coefficient of traction (COT) from drawbar pull and slope at slip percentages in a first range;
divide values of the nominal pull-slip curve by the COT to produce a normalized pull-slip curve;
determine an optimum operating state using the COT and the slope; and
provide the optimum operating state and a current operating point to a device for use in adjusting one or more current operating conditions.

### Claim 2 (depends on 1)

The track-type tractor of claim 1, wherein the plurality of modules cause the processor to calculate the coefficient of traction by calculating a plurality of instantaneous pull-weight ratios (PWratio) as
(Drawbar Pull−Rolling Resistance)/(machine mass*gravity*cos θpitch).

### Claim 3 (depends on 2)

The track-type tractor of claim 2, wherein the plurality of modules cause the processor to:
retain only instantaneous pull-weight ratios that meet at least one 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;
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.

### Claim 4 (depends on 3)

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.

### Claim 5 (depends on 4)

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.

### Claim 6 (depends on 1)

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.

### Claim 7 (depends on 6)

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

### Claim 8 (depends on 6)

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 (rpw) as
r
pw
=
PW
ratio
COT
and to retain from the plurality only those values that meet additional criteria including at least one of:
data is taken while in a forward gear;
the track speed is in a range of a minimum of about 50 mm/s to a maximum of about 1500 mm/s;
track acceleration is less than approximately 50 mm/s2;
rpw is less than approximately 0.99;
a COT value must have been successfully developed;
ground speed must be available;
no steering activity;
no brake activity;
deceleration pedal not activated.

### Claim 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.

### Claim 10 (depends on 9)

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.

### Claim 11 (depends on 9)

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.

### Claim 12 (depends on 11)

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.

### Claim 13 (depends on 9)

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.

### Claim 14 (depends on 9)

The method of claim 9, wherein calculating each of the plurality of normalized pull-weight ratio values (rpw) comprises calculating
r
pw
=
PW
ratio
COT
.

### Claim 15 (depends on 9)

The method of claim 9, wherein removing normalized pull-weight ratio (rpw) 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.

### Claim 16 (depends on 15)

The method of claim 15, wherein calculating the shear modulus adjustment factor (kadj) 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.

### Claim 17 (depends on 16)

The method of claim 16, wherein determining the estimated slip of the tracks at any normalized pull weight ratio (rpw) comprises performing a calculation of (f−1 (rpw))*kadj), where f−1 is the inverse function of the normalized pull-slip curve.

### Claim 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.

### Claim 19 (depends on 18)

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.

### Claim 20 (depends on 19)

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.