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Senior Design: Tachometer Calibration Device. Team 4: Jennifer Egolf, Matthew Hagon, Michael Lee, Christopher Pawson Sponsor: DuPont Advisor: Dr. Glancey. Mission Statement. Design and manufacture a portable device for the relative calibration of multiple surface tachometers. - PowerPoint PPT Presentation
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Senior Design:Tachometer Calibration Device
Team 4: Jennifer Egolf, Matthew Hagon, Michael Lee, Christopher Pawson
Sponsor: DuPont
Advisor: Dr. Glancey
Mission Statement
Design and manufacture a portable device for
the relative calibration of multiple surface
tachometers.
Surface Tachometers
Shaft
Encoder
Wheel Bracket
Surface Tachometers
V1 V2 V3 V4
Surface tachometers measure surface velocity
Detect small differences in speed across a system
Calibrated tachometers used as diagnostic tools
Reduce downtime of continuous processes
V1=V2=V3=V4
Desired Features with Metrics
Constant Speed % Variation in Speed
Portable Size / Weight
Ease of Use Set up time
Adaptable # of tachometers mounted
Adjustable # of attainable speeds
Durable # of cycles until failure
Inexpensive Cost
Wants Metrics
Benchmarks
High inertia devices Lathe
Current method used + Low variation in speed - Only accommodates one tachometer at a time - Cannot calibrate tachometers relative to one another - Not portable
Drum Previous method employed for calibration + Low variation in speed - Large and not portable
Hand-held calibration devices + Portable - Cannot calibrate tachometers relative to one another
Initial System Concept
Tachometers
User interface
Motor Controller
Motor
Tachometer mounting brackets
Subsystem Configuration
Three concepts for the critical subsystem were developed through benchmarking and brainstorming
Conveyor Belt Rotating Disc Rotating Drum
Metrics and Target ValuesDesign Specifications
< $20,000
> 105
at least 3
< 5 minutes
4
< 0.05%
< 3' x 3' x 3' & < 90lbs
0 5 10 15 20 25 30 35 40
% of speed variation
size & weight
# of tachometers mounted
set up time
# of attainable speeds
# of cycles until failure
cost
Met
rics
Rate of Importance (%)
Concept Selection
•Advantages
•Easy to mount multiple tachometers
•Disadvantages
• Vibrations associated with belt and linkage joints
• Difficult assembly
•High cost
•Advantages
•Ease of assembly
•Consistent performance
•Low cost
•Disadvantages
•Machining accuracy of disc crucial
•Advantages
•Ease of assembly
•Consistent performance
•Easy to mount multiple tachometers
•Disadvantages
• Large / Heavy
•Machining accuracy of drum crucial
Conveyor Disc Drum
Choosing the Best Solution
The disc was chosen as the best concept because:
Easy to assemble Consistent performance throughout life Low Cost Smallest / Least material
Chosen Concept of Subsystem
Tachometers
Motor & Gearbox
Tach mounts
Disk and Shaft
System Component Considerations
Tachometer mounts Positioning
Must be able to accommodate tachometers of circumference:• 6”• 12”• 30”
Disc Dimensional variability
Motor and Controller Selection Speed
Must be able to achieve specified surface velocities• 16 fpm• 110 fpm• 240 fpm
Torque Inertia Ripple
Motor and Controller
SGDH Servo Drive
Yaskawa SGMPH Servo Motor
Power requirements Start-up torque = 0.66 N-m
Inertia requirements System Inertia = 0.03 kg-m2
Speed requirements Three speed options
12 rpm 84 rpm 183 rpm
Velocity Ripple
Velocity Ripple
Fluctuations around the steady state velocity
Exact relationship between motor speed and % velocity ripple unknown 100 rpm: ± 5% Above 1000 rpm: <1%
Need to maintain high motor speeds but output relatively low disc speed Solution Gearbox
Gearbox Selection
Allows motor to run at optimal speeds 1000 - 5000 rpm
CGI, Inc. Planetary Gearbox 22:1 ratio
Motor speed of 2000 rpm = Disc speed of 91 rpm
Motor speed of 4000 rpm = Disc speed of 182 rpm
Design of Subsystem Components
Disc 5” diameter 2” thickness Machined in house
Tachometer mounts Purchase framing
materials from Bosch Machine mounting
blocks in house
Eccentricity Testing
Results: 0.0005” < variations <0.001” Create variations in speed
< 0.02%
Positioning Testing
Prototype
Locking handle
Gearbox
Motor
Tachometer
Disc and shaft
Slider Carriages
* Controller and user interface not pictured
Testing Method
Mount tachometer to rotating disc
Record speed variations over time
Peaks on graphs indicate Amplitude of recurring
speed variations Frequency of speed
harmonics
Time
Spe
edA
mpl
itude
Frequency
Speed in Time Domain
Speed in Frequency Domain
Full System Testing
Testing of the system revealed Large variations in
speed Many frequencies
Need to determine cause of variations
Spe
ed A
mp
litu
de
Speed
Tachometer speed variations from disc:
Testing of Motor and Gearbox
Remove disc and shaft Mount tachometer
Directly to shaft of gearbox Directly to shaft of motor
Record speed variations for each case
Tachometer speed variations with gearbox:
Tachometer speed variations without gearbox (just motor effect):
Direct Drive System Testing
Objective: Confirm that the gearbox is
the problem source (not bearings or coupling)
Procedure: Mount tachometer to directly
driven shaft Record variation in speed
Results: 0.2 – 0.6% speed variation Located at a distinct
frequency
Speed
Spe
ed A
mp
litu
de
Tachometer speed variations with directly driven shaft:
Similar variations to motor testing
Observations
The purchased gearbox is inappropriate for the application Creates many and large speed
variations (2.5%) Multi-stage construction
creates problems
The purchased motor exhibits acceptable performance Speed variations few and small (0.2%)
Recommendations for Further Development
Eliminate multiple stage gearbox Test system using worm gearbox Consult custom gearbox manufacturers
Rino GAM Andantex
Expense Summary to Date
Item Quantity Cost
Motor and Drive System 1 $3100
Bearings-NTN pillow block 2 $70
Coupling 1 $100
Gearbox 1 $540
Aluminum Bosch profile 3800 mm $190
Bosch Accessories Many $690
Total Cost 1 ~ $4700
* $1500 under budget – use toward carrying out recommendations for further development
Questions?