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Gear Bearing Technology

Gear Bearing Technology. December 9, 2003. Group 14: Pamela Carabetta Marisa Jenkins Sarah Kovach-Orr Anuja Mahashabde Qi Yan. Advisors: Mr. John Vranish Prof. Dinos Mavroidis Dr. Mircea Badescu Ms. Kathryn De Laurentis Mr. Brian Weinberg. Project Description.

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Gear Bearing Technology

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  1. Gear Bearing Technology December 9, 2003 Group 14: Pamela Carabetta Marisa Jenkins Sarah Kovach-Orr Anuja Mahashabde Qi Yan Advisors: Mr. John Vranish Prof. Dinos Mavroidis Dr. Mircea Badescu Ms. Kathryn De Laurentis Mr. Brian Weinberg

  2. Project Description • Need for improvement on existing planetary gear transmissions • John Vranish of NASA invented the “gear bearing” • Apply gear bearings to space exploration technology • Use gear bearings in a robotic wrist – possibly mount on explorer type robot

  3. Mission Statement • A robotic wrist that moves with greater precision and produces greater torque than those currently available through the use of gear bearings • Major Goals: • -Finalize the design of this robotic wrist along with its expected performance values by December 2003 • -Create a working model by May 2004.

  4. Significance • Robotic wrist should have improved precision, smoothness, and lift capability to weight ratio. • Potential applications outside of NASA: General robotics, prosthetics • 2 degrees of freedom

  5. Project Management

  6. Project Timeline

  7. Background: Planetary Gears Outer Ring Sun • Transmit higher torque • Low-backlash • Distributed load (longer life) • Works well with high-speed inputs (ideal for motors) • Limitations: small gear ratio, size, weight, cost Planet

  8. Gear Bearings • Advantages over planetary gears: • Phase-shifted for greater speed reduction • Lighter • Smaller • Cheaper • Stronger • Smoother (ME Magazine, 2002)

  9. Gear Bearing Kinematics • Gear Bearing = 180 = = • Planetary Gear -Stationary Carrier/Rotating Ring: = 2 = -Stationary Ring/Rotating Carrier: = 3 =

  10. Finite Element Analysis

  11. Existing Robotic Arm Rover Multidimensional Gear Bearing Robotic Arm Robotic Wrist and Hand Predicted Quality of End Product 1.)Referring to lab capabilities 2.)Referring to group’s capabilities 3.)Referring to time frame 1 4 4 4 3 5 3 2 2 4 3 4 5 5 3 Meaningfulness 1.)To group members 2.)To NASA 3 1 0 2 4 5 3 3 5 4 Risk of Failure 3 2 1 3 2 Challenge to Group 2 4 5 4 5 Market Need 1.)Application to NASA 2.)Application to Robotics Industry 1 1 4 2 5 5 3 3 4 4 Cost 4 1 5 4 4 Total 24 27 37 34 39 Ideas: Selection Matrix

  12. Concept Evolution Original Ideas: Robot Arm, Rover, Improve Existing Arm, 2D Gear Bearing, Robot Hand/Wrist Arm on Rover, 2D Gear Bearing, Robot Wrist New Direction: 2 Degree of Freedom Robot Wrist • Create robotic wrist with two degrees of freedom • Greater precision • Lift capability vs. weight

  13. Need Statements No. Need Imp. 1 the gear bearing reduces vibration in the arm 5 2 the gear bearing greater speed reduction 4 3 the gear bearing is lightweight 4 4 the gear bearing is compact 4 5 the gear bearing is easy to install 1 6 the wrist durable 5 7 the wrist is safe to user while in use and when not in use 5 8 the gear bearing high precision to pick up object 5 9 the wrist 2 degree of freedom 4 10 the wrist less motor torque required 3 11 the wrist perform more like human wrist 5

  14. Metrics Metric No. Need Nos. Metric Imp. Units 1 1 Damping coefficient range 5 N-s/m 2 2 Total torque 5 N-m 3 3 Total mass 4 Kg 4 4,10 Sizes 4 in. 5 4,10 Costs 3 Dollars 6 5 Time to assemble 3 S 7 6 Number of cycles to failure 5 Cycle 8 7 Bending strength 5 KN 9 8,11 Accuracy 5 Percentage 10 9 Area of movements 5 m2

  15. Need – Metrics Table

  16. Design Specifications • Gear Bearing: input ring – 57 teeth, sun – 27 teeth, driver planets – 15 teeth output ring – 58 teeth driven planets – 15 teeth 9 in-lb torque ability • Wrist: Approximate Dimensions: 6in X 5in X 6in Lift 3 lbs Approximate Weight 1lb (without motor and gear bearings)

  17. Concepts

  18. proE Model

  19. Exploded View Gear Bearings

  20. Safety Features • Moving parts (motors, gear bearings) are enclosed within the structure • Gear bearings allow for smaller motors • Encoders on the motors

  21. Parts and Cost • Rapid Prototype: epoxy resin ~$500 (overestimate) • Motor and Optical Encoder: $189 from Micromo • Screws: $2-10 box from the Home Depot • Metals of choice: stainless steel, titanium, aluminum

  22. Discussion and Conclusion • Gear bearings are superior to planetary gears • Use gear bearings to create a 2 degree of freedom robot wrist • Create working model using rapid prototyping • Potential applications outside of NASA

  23. Acknowledgements Mr. John Vranish & NASA Goddard Space Flight Center Advisors: Ms. Kathryn De Laurentis, Dr. Mircea Badescu, Prof. Dinos Mavroidis, & Mr. Brian Weinberg ME Magazine, 2002

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