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SIMULATED SLOPES ON A TEST RIG BASED EVALUATING CONTINUOUS

CEREAL YIELD METERING ACCURACY

A Case Study of Workshop ExperienceA Case Study of Workshop Experience

SANAEI, AKBAR; PhD

Assistant Professor, Agricultural Engineering Machinery Assistant Professor, Agricultural Engineering Machinery

DeptDept . .ISLAMIC AZAD UNIVERSITY-EGHLID BRANCH-IRANISLAMIC AZAD UNIVERSITY-EGHLID BRANCH-IRAN

Director, First Iranian Applied Research Centre of Advanced Director, First Iranian Applied Research Centre of Advanced Machinery and Technologies in Precision Farming at IUTMachinery and Technologies in Precision Farming at IUT

Email: Akbars@cc.iut.ac.ir or sanaeia@yahoo.co.uk

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ABSTRACTABSTRACT Yield mapping as a prerequisite of “precision Yield mapping as a prerequisite of “precision

farming evolution” needs more both field farming evolution” needs more both field and laboratory investigations for wide varied and laboratory investigations for wide varied slope effect based crops combiningslope effect based crops combining as an as an important influenced factor. important influenced factor.

Naturally, optimised precision and accuracy Naturally, optimised precision and accuracy of continuous crop yield metering on of continuous crop yield metering on combine harvesters requires more detailed combine harvesters requires more detailed studies on points such the field-slope studies on points such the field-slope variations which affect not only on soil variations which affect not only on soil characteristics and in-field spatial crop yield characteristics and in-field spatial crop yield but it is a serious problem to measure the but it is a serious problem to measure the reliable continuous spatial variable yield reliable continuous spatial variable yield variations during combine harvesting. variations during combine harvesting.

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ABSTRACT2ABSTRACT2 Author through his practical studies Author through his practical studies

conducted at Nafferton research Farm of conducted at Nafferton research Farm of Newcastle University in UK found out very Newcastle University in UK found out very varied topographic aspects. varied topographic aspects.

Previous author’s experiences in both Previous author’s experiences in both workshop and fields showed that the slope workshop and fields showed that the slope affects accurate yield measurement through affects accurate yield measurement through combining crops (Sanaei, A. 2008). combining crops (Sanaei, A. 2008).

Then the research was extended to design Then the research was extended to design and construct a test rig using clean grain and construct a test rig using clean grain elevator’s parts of Class Combine for more elevator’s parts of Class Combine for more controlled fruitful trials by simulating varied controlled fruitful trials by simulating varied slopes (pitch and roll) in workshop site.slopes (pitch and roll) in workshop site.

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Objective & MethodObjective & Method Today, there are only a few harvester combines Today, there are only a few harvester combines

with installed full package of yield meter kits with installed full package of yield meter kits equipped with a slope (both Pitch and Roll) equipped with a slope (both Pitch and Roll) sensor as well. sensor as well.

These studies showed that the accuracy of Ceres2 These studies showed that the accuracy of Ceres2 also may be improved by adding an optional also may be improved by adding an optional hillside slope sensor. hillside slope sensor.

It measures the angle of side-slopes and the It measures the angle of side-slopes and the instrument will correct the yield measurement for instrument will correct the yield measurement for the effect of the slope sensor location.the effect of the slope sensor location.

This paper examined and analysed data of This paper examined and analysed data of multidimensional detailed wide range of slope multidimensional detailed wide range of slope effects between 0-15 degrees on measuring yield.effects between 0-15 degrees on measuring yield.

This was done through accessing to algorithmic This was done through accessing to algorithmic models by installing previous version of Ceres2 models by installing previous version of Ceres2 yield meter on constructed test rig which showed yield meter on constructed test rig which showed comprehensive results including significant comprehensive results including significant differences on yield meter accuracy.differences on yield meter accuracy.

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INTRODUCTIONINTRODUCTION As previously mentioned, accurate and precise yield

monitoring and mapping on a combine harvester is yet a serious prerequisite for more processing of other stages of a successful precision farming project.

Based on the above concept, author decided to carry out comprehensive laboratory slope tests in his more advance research project according to basic works of Ciha (1984) ; Reitz & Kutzbach (1994); Kent et al.,(1990); Sanaei & Yule (1995); Sanaei & Yule (1996) and Hammer et al., (1995) for the improvement of Ceres2 instrumented combine harvester based yield measurement.

Hence, following the multiple fields yield monitoring experiments and data collection during harvest 1994-95, a preliminary laboratory experiment was conducted to investigate the continuous crop yield monitoring on the combine harvester affected by both pitch and roll slopes (Sanaei, A. 2008).

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Previous WorksPrevious Works The first-year results of these field and The first-year results of these field and

stationary grain combining workshop stationary grain combining workshop experiments based continues yield monitoring on experiments based continues yield monitoring on Deut Fahr combine harvester on Nafferton Deut Fahr combine harvester on Nafferton research farm of Newcastle University-UK research farm of Newcastle University-UK (Sanaei, A.1999), indicated that factors such as (Sanaei, A.1999), indicated that factors such as slope (pitch and roll), changing travel and slope (pitch and roll), changing travel and elevator speed, and wheel slip might have an elevator speed, and wheel slip might have an effect on the accuracy of measured yields. effect on the accuracy of measured yields.

These special limited workshop trials of the These special limited workshop trials of the slope effects (over a range of 0-10slope effects (over a range of 0-10 for various for various sides and up/down hill slopes) on stationary sides and up/down hill slopes) on stationary working combine performance in 1995 working combine performance in 1995 emphasized on existence of significant difference emphasized on existence of significant difference in yield measurements (Sanaei A. 2008). in yield measurements (Sanaei A. 2008).

These tests confirmed that both pitch and roll These tests confirmed that both pitch and roll may change the measured yield significantly. may change the measured yield significantly.

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Why Decision for Test Rig MethodWhy Decision for Test Rig Method??

Because, author decided again to conduct Because, author decided again to conduct more precise and comprehensive workshop more precise and comprehensive workshop tests to measure slope's effect over a wider tests to measure slope's effect over a wider slope range of pitch and roll (0-15slope range of pitch and roll (0-15). ).

For this, a reliable For this, a reliable experimental test rigexperimental test rig was was started to design and construct pre-harvest started to design and construct pre-harvest 1996 which was delayed until February 1997 1996 which was delayed until February 1997 because of provided parts delay. because of provided parts delay.

This experiment was included This experiment was included more detailed more detailed slope trials with four orientations of clean slope trials with four orientations of clean grain elevator slope positiongrain elevator slope position as well as other as well as other related trails for some more influenced related trails for some more influenced factors such as factors such as clean grain elevator speedclean grain elevator speed..

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MATERIALS AND METHODSMATERIALS AND METHODS The test rig design comprises The test rig design comprises two funnel shaped two funnel shaped

discharge and feeding grain binsdischarge and feeding grain bins fitted on the main fitted on the main frame skeleton (Figure 1). frame skeleton (Figure 1).

A A magnetic speed sensor was constructedmagnetic speed sensor was constructed, the , the magnetic core fitted on the driven shaft of an electric magnetic core fitted on the driven shaft of an electric motor and the probe connected to Hermes data logger. motor and the probe connected to Hermes data logger.

A A speed converterspeed converter changed and controlled the changed and controlled the rotary speed of this electric motor where appropriate. rotary speed of this electric motor where appropriate.

A A door at the bottom of the upper bindoor at the bottom of the upper bin could be opened could be opened as an end point of each test to discharge the grain from as an end point of each test to discharge the grain from discharge tank into feeding tank. discharge tank into feeding tank.

Another door on lower binAnother door on lower bin admitted an adjusted admitted an adjusted amount of grain into bottom auger based on a fixed line amount of grain into bottom auger based on a fixed line for the whole experiment. for the whole experiment.

Three parts; Three parts; clean grain elevatorclean grain elevator (part No: 682765.0 (part No: 682765.0 for the Dominator 218) plus, for the Dominator 218) plus, discharge augerdischarge auger and and bottom augerbottom auger (filler tube) were provided by CLAAS (filler tube) were provided by CLAAS Combine Company in Germany and modified to fit the Combine Company in Germany and modified to fit the test rig.test rig.

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Figure 1- Instrumented Test Rig construction and configuration, February 1997

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Test Rig Components DesignTest Rig Components Design The The grain elevator was fitted verticallygrain elevator was fitted vertically based on based on

the manufacture’s instructions. the manufacture’s instructions. The The Moisture sensorMoisture sensor was fitted on the discharge was fitted on the discharge

auger just above the discharge bin and the auger just above the discharge bin and the yield yield sensor partssensor parts were installed inside of the upper were installed inside of the upper part of clean grain elevator. part of clean grain elevator.

The The paddle chain elevator was poweredpaddle chain elevator was powered via a 540 via a 540 rpm PTO of a ZETOR tractor through a driving rpm PTO of a ZETOR tractor through a driving system. system.

This This driving system includesdriving system includes a triangle frame to a triangle frame to carry a gearbox with a shaft for changing the carry a gearbox with a shaft for changing the rotation direction of PTO drive shaft. rotation direction of PTO drive shaft.

The The driven shaft of the gearboxdriven shaft of the gearbox is connected to is connected to main drive shaft of the pulleys (SPA 140-3 2517 & main drive shaft of the pulleys (SPA 140-3 2517 & SPA 250-3 2517) and belt (SPA 1600) via universal SPA 250-3 2517) and belt (SPA 1600) via universal drive shaft. The diameters of two slotted pulleys drive shaft. The diameters of two slotted pulleys fitted on the main drive shaft and bottom or cross fitted on the main drive shaft and bottom or cross auger shaft were 140 and 250 mm respectively. auger shaft were 140 and 250 mm respectively.

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Test Rig Design CalculationsTest Rig Design CalculationsRPM

d

drpmoutput

i

o

540140

250540 302 4.

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Other Test Rig ComponentsOther Test Rig Components The other main part of the test rig was The other main part of the test rig was

a a four-wheeled carriage basefour-wheeled carriage base, which , which could be used to make small changes in could be used to make small changes in slope and for transportation. slope and for transportation.

The steeper slopes were made using a The steeper slopes were made using a hydraulic jackhydraulic jack and and a 2 tonne hydraulic a 2 tonne hydraulic mobile crane. mobile crane.

A A magnetic speed sensormagnetic speed sensor was was constructed and fitted on the shaft of constructed and fitted on the shaft of an an electric motor connected to a electric motor connected to a transformertransformer to provide signals with to provide signals with smooth factor of 7 seconds based on a smooth factor of 7 seconds based on a normal forward speednormal forward speed of the combine of the combine (4.7 km per hour). (4.7 km per hour).

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Yield Meter CalibrationYield Meter Calibration The The Ceres2 yield-metersCeres2 yield-meters was calibrated and set was calibrated and set

up based on manufacture instructions (issue 09, up based on manufacture instructions (issue 09, 7/5/96, NG 406-537). 7/5/96, NG 406-537).

Two plastic protractors equipped with a hanging Two plastic protractors equipped with a hanging weight barweight bar fitted on both sides of grain elevator fitted on both sides of grain elevator indicated degree of slope for each treatment.indicated degree of slope for each treatment.

The constructed Test Rig after The constructed Test Rig after final setting up final setting up and rechecking for insured reliable work of all and rechecking for insured reliable work of all sensors and fitted instrumentssensors and fitted instruments was used to was used to conduct reliable tests of Ceres2 yield sensing conduct reliable tests of Ceres2 yield sensing based on both precise and accurate Ceres2 yield based on both precise and accurate Ceres2 yield meter calibration. meter calibration.

This was conducted by This was conducted by fitting four load cell unitsfitting four load cell units on each corner of the discharge grain tank.on each corner of the discharge grain tank.

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Data Logger and SignalsData Logger and Signals

The The signals sent from four load cellssignals sent from four load cells attached to discharge tank via connection attached to discharge tank via connection to an electronic data logger ‘Signal to an electronic data logger ‘Signal Centre’ could record the momentum. Centre’ could record the momentum.

This load cells was connected to four This load cells was connected to four separate channels of the ‘Signal Centre’ separate channels of the ‘Signal Centre’ data acquisition system to save the data acquisition system to save the continuous data signal records of grain continuous data signal records of grain flow rates continuously. flow rates continuously.

This was done during This was done during accuracy tests of accuracy tests of Ceres2 yield sensor based on loading a Ceres2 yield sensor based on loading a precise weighted amount of wheat kernelprecise weighted amount of wheat kernel on the feeding grain tank. on the feeding grain tank.

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Elevator Speed Based Yield Elevator Speed Based Yield Measurement TestsMeasurement Tests

Ceres2 yield sensor accuracy was Ceres2 yield sensor accuracy was examined for examined for different elevator different elevator speeds within a range of 180-300 rpmspeeds within a range of 180-300 rpm with an increment of 20 rpm in level with an increment of 20 rpm in level condition. condition.

Trial 5 on the test rig was included a Trial 5 on the test rig was included a number of these tests. number of these tests.

This chain processing showed the This chain processing showed the actual relationship between actual relationship between different different speeds of grain elevator and yieldspeeds of grain elevator and yield measurements.measurements.

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Slope Based Yield Measurement Tests This part of experiment was carried out with This part of experiment was carried out with slopes slopes

from 0-15° in one degree incrementsfrom 0-15° in one degree increments for each for each treatment of trials in four oriented sides of test rig treatment of trials in four oriented sides of test rig and achieved data were analysed statistically in and achieved data were analysed statistically in Excel spreadsheetExcel spreadsheet

1. Trial 1 Rear Slope (RS)1. Trial 1 Rear Slope (RS) 2. Trial 2 Front Slope (FS)2. Trial 2 Front Slope (FS) 3. Trial 3 Left-hand side Slope (LHS)3. Trial 3 Left-hand side Slope (LHS) 4. Trial 4 Right-hand side Slope (RHS) 4. Trial 4 Right-hand side Slope (RHS) Each treatment was carried out by feeding a definite Each treatment was carried out by feeding a definite

amount of grain (384 kg. wheat)amount of grain (384 kg. wheat) into the system into the system with with three replications for up and downthree replications for up and down (pitch) (pitch) slopes and slopes and two replications for sidetwo replications for side (roll) slopes. (roll) slopes.

Even though each treatment contained Even though each treatment contained a significant a significant number of signal recordsnumber of signal records for the yield measurement for the yield measurement but more replications ensured the reliability of tests but more replications ensured the reliability of tests by producing a larger number of records.by producing a larger number of records.

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Test Rig Based Slope Tests ConditionsTest Rig Based Slope Tests Conditions The number of records and the time needed for The number of records and the time needed for

each test varied from 30-80 records within 2-7 each test varied from 30-80 records within 2-7 minutes. minutes.

Each test was initiated by simultaneously activating Each test was initiated by simultaneously activating the yield meter to log the records and opening the the yield meter to log the records and opening the slide door at bottom of feeding grain bin. slide door at bottom of feeding grain bin.

Each test was terminated when the yield meter Each test was terminated when the yield meter monitor displayed a ‘0.00’ for moisture and monitor displayed a ‘0.00’ for moisture and received yield signals. received yield signals.

With the purpose of providing more even conditions With the purpose of providing more even conditions for the whole experiment of each orientation the for the whole experiment of each orientation the tractor’s engine was operating continuously tractor’s engine was operating continuously without changing in rpm or other specifications.without changing in rpm or other specifications.

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RESULTS AND DISCUSSIONRESULTS AND DISCUSSION Slope Tests:Slope Tests: Ceres2 measurements at a range of slopes Ceres2 measurements at a range of slopes

were corrected relative to GCF calculated in the were corrected relative to GCF calculated in the level situation to achieve the actual mass of level situation to achieve the actual mass of the grain (Table1-third column). the grain (Table1-third column).

Comparison of corrected Ceres2 yield records Comparison of corrected Ceres2 yield records (kg) of each slope test relative to corrected (kg) of each slope test relative to corrected yield (384 kg) in the level situation gave errors yield (384 kg) in the level situation gave errors up to 58.8% at 15up to 58.8% at 15 at right slope (Table1-last at right slope (Table1-last column). column).

In overall, In overall, the results demonstrated that the results demonstrated that increased downhill slope decreased yield increased downhill slope decreased yield measurement while increased uphill slope measurement while increased uphill slope increased it with a maximum 31.8 % error for increased it with a maximum 31.8 % error for both situationsboth situations..

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Table1) Calculated yield errors at test Table1) Calculated yield errors at test rig slopes relative to level situationrig slopes relative to level situation..

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22 - -Elevator Speed EffectElevator Speed Effect:: Yield measured by Ceres2 RDS Yield measured by Ceres2 RDS

Tech. consistently decreased when Tech. consistently decreased when elevator speed was increased elevator speed was increased within 180-300 rpm (Figure 2). within 180-300 rpm (Figure 2).

Observations results 3 to 18 Observations results 3 to 18 showed peak variations of yield showed peak variations of yield measurement for variable grain measurement for variable grain elevator speeds on the test rig.elevator speeds on the test rig.

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Figure 2- Plots over the elevator speeds range Figure 2- Plots over the elevator speeds range of 180-300 rpm showed a negative relationshipof 180-300 rpm showed a negative relationship..

Yield Variation Plots on Variable Elevator Speed Observations 1- 31, Test Rig-1997

0

1

2

3

4

5

6

7

8

9

Observations/time

Yie

ld:

t/h

a

T24/180rpm T19/200rpm T23/220rpm T20/240rpmT21/260rpm T22/280rpm T28/300rpm T27/303rpm

300 rpm

180 rpm

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Figure3- Plateau yields variation plots for Figure3- Plateau yields variation plots for variable elevator speeds on the test rig-1997variable elevator speeds on the test rig-1997

Effect of Variable Elevator Speed on Yield Measurement Test Rig 1997

44.5

55.5

66.5

77.5

88.5

9

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Peak observations from 3-18

Yie

ld:

t/h

a

180 rpm

200 rpm

220 rpm

240 rpm

260 rpm

280 rpm

300 rpm

300 rpm

180 rpm

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Figure 4- Linear regression of yield against variable Figure 4- Linear regression of yield against variable elevator speed-test rig 1997 (data:3 to18)elevator speed-test rig 1997 (data:3 to18)

The mean of yield observations 3 to 18 The mean of yield observations 3 to 18 (figure3) indicates a negative (figure3) indicates a negative relationship between measuring yield relationship between measuring yield and elevator speed (r sq= 0.97***) and elevator speed (r sq= 0.97***) (Figures 4)(Figures 4)

RPM Line Fit Plot-Elevator Speed TrialTest Rig-1997

y = -0.4779x + 8.2771R2 = 0.95

0

2

4

6

8

10

0 1 2 3 4 5 6 7RPM

Yie

ld:t

/ha

Yield:t/ha Linear (Yield:t/ha)

Observations:3 to 18

RPM Residual Plot-Yield/Elevator Speed TrialTest Rig-1997

-0.6-0.4-0.2

00.20.4

0 1 2 3 4 5 6 7

RPM

Resi

dual

s

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Other regression used the whole Other regression used the whole data of the tests (Figure 5)data of the tests (Figure 5)..

Though, this model shows a high Though, this model shows a high negative correlation (r sq= 0.90***) negative correlation (r sq= 0.90***) between yield measurements and between yield measurements and elevator speed.elevator speed.

The residuals plot does not confirm The residuals plot does not confirm the linearity of the model. the linearity of the model.

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Figure 5- Linear regression of elevator speed Figure 5- Linear regression of elevator speed against yield and residuals (whole data)against yield and residuals (whole data)

Rpm/Pto Line Fit Plot-Elevator Speed TrialsTest Rig-1997

y = -0.0138x + 8.5135R2 = 0.9045

0

2

4

6

8

150 200 250 300

Rpm/Pto

Yie

ld:

t/h

a

Yield: t/ha Linear (Yield: t/ha)

Residuals Plot of Linear Yield/Speed Elevator Trial

Test rig - 1997

-2

-1

0

1

2

0 2 4 6 8

Elevator speed/rpm

Resid

uals

Linear Residuals

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Figure 6- Quadratic regression of elevator Figure 6- Quadratic regression of elevator speed against yield and residuals (whole data)speed against yield and residuals (whole data)

Using the whole data, a second order Using the whole data, a second order polynomial regression (Figure6) polynomial regression (Figure6) improved and removed the trend in improved and removed the trend in residuals (Table 2).residuals (Table 2).

Elevator Speed Line Fit Plot-test rig/1997

y = 0.0001x2 - 0.0714x + 15.337R2 = 0.9815

0

2

4

6

8

150 200 250 300

Speed/rpm

Yiel

d: t/

ha

Yield: t/ha Poly. (Yield: t/ha)

RPM/pto Residuals Plot-Polynomial Model

-0.15-0.1

-0.050

0.05

0.10.15

4 4.5 5 5.5 6 6.5

rpm/pto

Res

idua

ls

Residuals

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Table 2- The regression equationTable 2- The regression equation

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Slope Test DiscussionSlope Test Discussion 1- Slope Effect: Ceres2 yield error at each 1- Slope Effect: Ceres2 yield error at each

slope could not be estimated because of using slope could not be estimated because of using a definite batch of the grain for each trial and a definite batch of the grain for each trial and the technical problem of cascading back and the technical problem of cascading back and down the grain into the bottom auger and down the grain into the bottom auger and elevator respectively. elevator respectively.

These tests also completely confirmed findings These tests also completely confirmed findings of 1995 Ceres2 tests on the stationary working of 1995 Ceres2 tests on the stationary working combine and need to develop models based on combine and need to develop models based on a practical range of field slopes (i.e. 0°- 30°) a practical range of field slopes (i.e. 0°- 30°) for each orientation of different combine types for each orientation of different combine types and models. and models.

Indeed, without implementing these slope Indeed, without implementing these slope sensors, Ceres2 yield measurements would not sensors, Ceres2 yield measurements would not be reliable under realised field slope be reliable under realised field slope conditions.conditions.

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Speed Test DiscussionSpeed Test Discussion 2- Elevator Speed Tests: The 2- Elevator Speed Tests: The

importance of using a constant importance of using a constant combine velocity and elevator speed is combine velocity and elevator speed is recommended by Birrel et al., (1995) recommended by Birrel et al., (1995) and Schueller (1983) to keep a steady and Schueller (1983) to keep a steady grain flow for reliably measuring yield. grain flow for reliably measuring yield.

However, the speed may change when However, the speed may change when entering and leaving the crop, at entering and leaving the crop, at head-lands and when combining very head-lands and when combining very dense and moist standing crop or dense and moist standing crop or over-loading grain into elevator over-loading grain into elevator (Klemme et al, 1992; Reitz & Kutbatch, (Klemme et al, 1992; Reitz & Kutbatch, 1993, 1995). 1993, 1995).

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ConclusionConclusion In general, the above test rig experiments In general, the above test rig experiments

suggested both linear (r sq= 95 %***) and 2nd suggested both linear (r sq= 95 %***) and 2nd order polynomial (r sq= 98 %***) models of yield order polynomial (r sq= 98 %***) models of yield variation with elevator speed between 180-300 variation with elevator speed between 180-300 rpm. rpm.

These correspond with a mean yield difference These correspond with a mean yield difference between 5.5 to 8.5 t/ha (Figures 2-6). between 5.5 to 8.5 t/ha (Figures 2-6).

This revealed serious errors of excess yield up to This revealed serious errors of excess yield up to 54% when the combine elevator speed decreased 54% when the combine elevator speed decreased from 300 to 180 rpm. from 300 to 180 rpm.

Though yield errors affected by unexpected Though yield errors affected by unexpected changes of speed might be removed to improve changes of speed might be removed to improve data, the performance of each type and model of data, the performance of each type and model of combine harvester will require testing to preserve combine harvester will require testing to preserve a constant elevator and travel speed under a constant elevator and travel speed under fluctuated field conditions when harvesting.fluctuated field conditions when harvesting.

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ReferencesReferences Birrel et al. (1995).Birrel et al. (1995). Ciha, A. J. (1984). Slope Position and Grain Yield of Soft White Winter Wheat. Ciha, A. J. (1984). Slope Position and Grain Yield of Soft White Winter Wheat.

Agronomy JournalAgronomy Journal, , 7676, PG193-196., PG193-196. Reitz, P., & Kutzbach, H. D. (1993). Reitz, P., & Kutzbach, H. D. (1993). Measurement Techniques for Yield Mapping Measurement Techniques for Yield Mapping

During Grain Harvesting With Combine. In During Grain Harvesting With Combine. In XXV CIOSTA CIGR CongressXXV CIOSTA CIGR Congress, (pp. 48-53). , (pp. 48-53). GermanyGermany

Reitz, P., & Kutzbach, H. D. (1995). Reitz, P., & Kutzbach, H. D. (1995). Investigations on a Particular Yield Mapping Investigations on a Particular Yield Mapping System for Combine Harvesters. System for Combine Harvesters. Computers and Electronics in AgricultureComputers and Electronics in Agriculture, , 1414, 137-, 137-150.150.

Hammer, R. D.; Young, F. J.; Wollenhaupt, N. C.; Barney, T. L. & Haithcoate, T. W. Hammer, R. D.; Young, F. J.; Wollenhaupt, N. C.; Barney, T. L. & Haithcoate, T. W. (1995). Slope Class Maps from Soil Survey and Digital Elevation Models. (1995). Slope Class Maps from Soil Survey and Digital Elevation Models. Soil Soil Science Society American J.Science Society American J., , 5959(-), 509-519.(-), 509-519.

Klemme et al. (1992)Klemme et al. (1992) Kent et. al. (1990) Kent et. al. (1990) Yule, I. J. ; Sanaei, A. ; Hodgkiss, A. & Korte, H. (1995). Yule, I. J. ; Sanaei, A. ; Hodgkiss, A. & Korte, H. (1995). Yield Mapping Combinable Yield Mapping Combinable

Crops: Field Experience, Problems and Potential. In Crops: Field Experience, Problems and Potential. In Agricultural And Biological Agricultural And Biological Engineering Conference; New Horizons, New ChallengesEngineering Conference; New Horizons, New Challenges, 1 (pp. 2). Newcastle - , 1 (pp. 2). Newcastle - England: University of Newcastle Upon Tyne. EnglandEngland: University of Newcastle Upon Tyne. England

Sanaei, A. & Yule, I. J. (1996a). Accuracy of Yield Mapping Systems: The Effects of Sanaei, A. & Yule, I. J. (1996a). Accuracy of Yield Mapping Systems: The Effects of Combine Harvester Performance. Combine Harvester Performance. AgEng’96 Conference,AgEng’96 Conference, Paper 96G-016. Madrid. Paper 96G-016. Madrid. SpainSpain

8. Sanaei, A. & Yule, I. J. (1996b). Yield Measurement Reliability on Combine 8. Sanaei, A. & Yule, I. J. (1996b). Yield Measurement Reliability on Combine Harvesters. In ASAE (Ed.), Harvesters. In ASAE (Ed.), ASAE Annual International MeetingASAE Annual International Meeting, Paper No. 961020 , Paper No. 961020 (pp. 14). Phoenix Arizona: ASAE. USA(pp. 14). Phoenix Arizona: ASAE. USA

9- Sanaei, A. (1998).Instrumented Combine Harvester Based Related Yield 9- Sanaei, A. (1998).Instrumented Combine Harvester Based Related Yield Mapping Aided by GIS/GPS. Unpublished PhD Dessertation. Agricultural and Mapping Aided by GIS/GPS. Unpublished PhD Dessertation. Agricultural and Environmental Science Department. University of Newcastle Upon Tyne. England.Environmental Science Department. University of Newcastle Upon Tyne. England.

10- Sanaei, A. (2008). Slope and Wheel Slip’s Variations Based Continuous 10- Sanaei, A. (2008). Slope and Wheel Slip’s Variations Based Continuous Cereal Yield Monitoring on Combine Harvester Aided by GPS/GIS. Cereal Yield Monitoring on Combine Harvester Aided by GPS/GIS. A case study of A case study of field-workshop experience. field-workshop experience. World Conference on Agricultural Information and IT-World Conference on Agricultural Information and IT-IAALD AFITA WCCA, Tokyo, Japan, 24-27 August, 2008IAALD AFITA WCCA, Tokyo, Japan, 24-27 August, 2008