Senior Design: Tachometer Calibration Device

1. Senior Design:Tachometer Calibration Device Team 4: Jennifer Egolf, Matthew Hagon, Michael Lee, Christopher Pawson Sponsor: DuPont Advisor: Dr. Glancey

2. Mission Statement • Design and manufacture a portable device for the relative calibration of multiple surface tachometers.

3. Surface Tachometers Encoder Shaft Wheel Bracket

4. Surface Tachometers • 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 V1=V2=V3=V4

5. Desired Features with Metrics Wants 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

6. 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

7. Initial System Concept User interface Tachometers Motor Controller Motor Tachometer mounting brackets

8. Subsystem Configuration • Three concepts for the critical subsystem were developed through benchmarking and brainstorming Conveyor Belt Rotating Disc Rotating Drum

9. Metrics and Target Values

10. Concept Selection Conveyor Disc Drum • Advantages • Ease of assembly • Consistent performance • Easy to mount multiple tachometers • Disadvantages • Large / Heavy • Machining accuracy of drum crucial • 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

11. 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

12. Chosen Concept of Subsystem Tachometers Disk and Shaft Tach mounts Motor& Gearbox

13. 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

14. Motor and Controller SGDH Servo Drive • 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 Yaskawa SGMPH Servo Motor

15. 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

16. Allows motor to run at optimal speeds 1000 - 5000 rpm CGI, Inc. Planetary Gearbox 22:1 ratio Gearbox Selection Motor speed of 2000 rpm = Disc speed of 91 rpm Motor speed of 4000 rpm = Disc speed of 182 rpm

17. Design of Subsystem Components • Disc • 5” diameter • 2” thickness • Machined in house • Tachometer mounts • Purchase framing materials from Bosch • Machine mounting blocks in house

18. Eccentricity Testing • Results: • 0.0005” < variations <0.001” • Create variations in speed < 0.02%

19. Positioning Testing

20. Prototype Tachometer Locking handle Slider Carriages Motor * Controller and user interface not pictured Gearbox Disc and shaft

21. Testing Method Speed in Time Domain • Mount tachometer to rotating disc • Record speed variations over time • Peaks on graphs indicate • Amplitude of recurring speed variations • Frequency of speed harmonics Speed Time Speed in Frequency Domain Amplitude Frequency

22. Full System Testing • Testing of the system revealed • Large variations in speed • Many frequencies • Need to determine cause of variations Tachometer speed variations from disc: Speed Amplitude Speed

23. Testing of Motor and Gearbox Tachometer speed variations without gearbox (just motor effect): • 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:

24. 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 Tachometer speed variations with directly driven shaft: Speed Amplitude Speed • Similar variations to motor testing

25. 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%) Observations

26. Recommendations for Further Development • Eliminate multiple stage gearbox • Test system using worm gearbox • Consult custom gearbox manufacturers • Rino • GAM • Andantex

27. Expense Summary to Date * $1500 under budget – use toward carrying out recommendations for further development

28. Questions?