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Round Baler Weighing SystemCNH Design Team
R. Andrew HackendornChris MeehanDan TraubJohn ElliottPhil Zandona
Project Goal• Determine if a load cell based weighing system is a feasible and marketable design.
• Using the three load cells provided by CNH, develop a kit to modify the round baler so that it may dynamically weigh hay bales.
• Develop a method for accurately filtering and analyzing data.
Project Benefits
• Real time bale weights– Can determine bale size by
more than simply diameter
– Can track more productive areas of farm land with GPS
• CNH will have an advantage over competitors by offering a round baler with the option of obtaining a dynamic bale weight
~6 ft
System View
Axle Load Cell
Axle Load CellHitch Load Cell
Inclinometers
SignalConditioner
Filtering/Processing Algorithm & Display
Free Body Diagram
R2
R1R3
Total Weight = W = R1 + R2 + R3
W
Error Due to Incline
• Load cells read normal to baler/ground
• True weight will not be reflected
• Inclinometers will attempt to compensate for this
Weight of Baler
Load Cell Readings
Error Due to Incline
Angle (degrees)
Error(%)
-Because of error we chose inclinometers in two orthogonal directions-We multiply the reactions by the cosine of the angles read by each inclinometer
Concept Generation
Wants, Metrics, and Target Values
Ranked Top Metrics Rate of Importance
Target Value
Parts Changed on Current Baler 14% < 1Number of Parts of Kit 13% < 15.0Manufacturing Cost 13% < $1300.0
Maintain Existing Dimensions 13%Hitch ‐Within 2” any directionAxle ‐ Only move back (< 6”)
Number of Steps in Assembly 11% < 50
Dynamic Weight Accuracy 7% 5 percentStatic Weight Accuracy 7% 5 percent
Ranked Project Wants
Easy to Attach Kit
Accurate Weight
Modification of Baler
Time to Fail Cost Simplicity Size
Rate of Importance
25% 20% 20% 15% 10% 5% 5%
Hitch Concept• Concept shaped to “hug” existing hitch structure.
• Hitch location is identical to existing design.
Load Cell
Connection to Tractor
Bolt holes for attachment to hitch ‐1000
0
1000
2000
3000
4000
5000
Hitch 1 Hitch 2 Hitch 3
Concepts vs. Score
Hitch Concept
Hitch Concept ‐ Analysis
• Dynamic load factor of 2 applied (2270 lbs)
• Stress analysis shows FOS of 1.4
Axle Concept
• Load cell would plug into “sleeve” that would be bolted into the existing hole in the orange axle.
• Simple design – 2 Parts
‐2000
0
2000
4000
6000
Axle 1 Axle 2 Axle 3
Concepts vs. Score
Axle Concept
• The blue arrow indicates the far end of the load cell in the sleeve.
• Because of the positioning of the load cell, the new axle keeps exact camber angle as the existing axle.
Load CellSupport Bracket
Axle Concept ‐ Analysis
• Dynamic load factor of 2 applied (5500lbs)
• Stress analysis shows a factor of safety of about 1.5
• Weakest point was located in load cell itself, not in axle structure
Blue is a FOS greater than 1
Installation of Selected Concepts
Hitch Installation
• Removed old hitch attachment and installed our concept.
• Metrics Satisfied – Only 2 parts
– 5 bolts to install
– Original dimensions unaltered
Axle InstallationLoad Cell and Sleeve Assembly
Load Cell / Wheel Hub Assembly Complete Assembly
• Metrics Satisfied– 4 parts per wheel
– Half hour installation
– Original dimensions unaltered
Cost AnalysisRaw Material
($ / lb)Weight (lb)
Assemblies (#)
Total Cost ($)
Axle 1.35 7.2 1 9.72
Hitch 1.35 15.2 1 20.52
Number of Raw Pieces
Time to machine raw pieces (hrs)
Time to assembly raw pieces including welds(hrs)
Cost ($)
Hitch 7 4 1.5 165.00
Axle 4 4 .5 135.00
300.00
*NOTE: 1 Man Hour = $30
Labor
Parts
Cost ($) Quantity (#) Total ($)
Load Cell 130 3 390
Inclinometer 31 2 61
Conditioner 300 1 300
Total: 751
Hardware
Target Value
• $1080.00 standard cost• Standard cost includes material and plant labor to install•Satisfies metric target value (< $1300)
• Retail price of ~$3,240 for factory installed option
Testing and Analysis
System Calibration• Testing load cells with mower at
the UD Agricultural School (could achieve same PTO speed as baler)
• Confirmed mode of collecting data
• Preliminary data acquired to gain insight on filtering techniques
• Determined load cell scale factors
• Similar method used for inclinometers
Final Testing PlanAll tests with PTO engaged:
1) Baling
2) Flat ground*
3) Bump Track*
4) Changed Roll*
5) Changed Pitch**Full bale in chamber
Sample Results
Right Axle Load Cell
• Data acquired while baling
Roll (left/right) Inclinometer
• Bump Track Raw Data
•At 4o, less than 1% error induced w/o corrections
Increasing weight
4 degrees
-4 degrees
150 sec
Bal
e W
eigh
t, lb
s
1500
Data Analysis
Frequency, Hz
Am
plitu
de
PTO Freq
Fourier TransformAfter converting from time domain to frequency domain, we observe some of the dominating frequencies contributing to the data noise, such as the PTO.
Error AnalysisFiltering Technique
Flat Ground and Baling Testing
• We used the Butterworth lowpass filter to remove the high frequency noise
• We found that a 5th order filter with a cut off frequency of 0.00075Hz best fit our data
• BLUE – Raw data
• GREEN – Data after filtering
Flat Ground, Bale in Chamber
Time, s
Bal
e W
eigh
t, lb
s
Baling
Time, s
Bal
e W
eigh
t, lb
s
Data Analysis
Flat Ground and Baling Testing
• Preliminary analysis utilized running averages and interval averages (after combining all components)
• RED – Raw data
• GREEN – Data after interval avg.
• BLUE – Data after running avg.
Flat Ground, Bale in Chamber
Time, s
Bal
e W
eigh
t, lb
s
Baling
Time, s
Bal
e W
eigh
t, lb
s
Error AnalysisAveraging Technique
5 Second Intervals1 Second Intervals
• Increasing time interval• Made curve smoother and reduced maximum error• Error = 2.83%
• Shorter time interval• Curve still noisy• Error = 7.55%
Error Analysis
Using only averaging techniques the accuracy metric (< 5%) was satisfied
Interval of 3.48 seconds is within 5% errorEach load cell is off by a constant factor, leading to a correction factor of 1.08
Target Interval = 3.5s
Prototype Conclusion
ALL Initial metrics for design have been satisfied!
– With prototyped concept proven feasible, a productionlevel design can be developed
Production Level Design
• Both designs contain minor differences from prototypes
• Elongated load cell is the major difference
Production Hitch Production Axle
Questions?
Concept SelectionUDesign
Benchmarking
• CNH Criteria
• CNH Grinder / Mixer Machine
• Two Online Journals – www.elsevier.com
• Vermeer 605 Super M Cornstalk Special Baler
InclinometersChange in Pitch:
z
xѲ
ground
axle
Ѳ
hitch
Lh
La
h
• Looking at the Baler geometries we are capable of solving for the weight of baler and hay given one force measurement.
Preliminary Hitch Concepts
Concept 1
Concept 2
Concept 3
Preliminary Axle Concepts
Concept 1 Concept 2
Concept 3
Concept Selection
• Using our metrics and target values, we used UDesign to give each of our concepts a score.
• Benchmark score: 1660
• Winning Hitch score: 4556
• Winning Axle score: 5853
Axle Installation
• Contrary to CNH’s drawings, the bolt hole to attach the spindle was oriented 25o off
– Did not allow for correct load cell orientation
• Needed to install a new axle
º25
Actual Location
Required Location
Original hole location on old axle
Axle Installation
• New axle required modified support bracket
• Installed 2 strips connecting the brackets
• Metrics Satisfied– 4 parts per wheel
– Half hour installation
– Original dimensions unaltered
Original Support BracketNew Support Bracket
Prototype Data Acquisition Overview1. Load Cell‐ Output Rating: 1.0 mV/V = 9382
lbs‐ Accuracy = 99.75%‐ Max. Excitation Voltage = 20 V
(AC or DC)‐ Input Resistance = 350 +20/‐0 Ω‐ Output Resistance = 350 Ω
2. Conditioner‐ Model: Somat 2100‐ Allowable Input Voltage = 7.5–
18 V‐ Use Analog for mV/V
Calibration
3. Cab Display‐ Laptop‐ USB Powered‐ Filtering and Signal Processing‐ Display Bale Weigh
Project TimelineTasks
1‐Sep 8‐Sep 15‐Sep 22‐Sep 29‐Sep 6‐Oct 13‐Oct 20‐Oct 27‐Oct 3‐Nov 10‐Nov 17‐Nov 24‐Nov 1‐Dec 8‐Dec 15‐Dec
Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9 Week 10 Week 11 Week 12 Week 13 Week 14 Week 15 Week 16
Phase 1 Phase 1
Design Requirements and Project Scope
Phase 2 Phase 2
Concept Generation
Concept Selection
Phase 3 Phase 3
Detailed Designs
Select Conditioner
Have final solid drawings ready to send to CNH
Have prototype Manufactured
Have prototype installed and ready to test
Phase 4 Phase 4
Software Acquisition and Programming
Testing
Data Analysis
Data Phases Concepts CNH Testing