Gateway Coalition Wright State University Shoulder to Elbow Design February 4 th, 2000
Jenny Broering Mike Hill Rahul Shah Michael Wasco
Agenda Introduction Base/Shoulder Design Upper Arm Design Elbow Joint Design Conclusions Questions Introduction Conclusions Designs
Current Base Design
Base Design Swivel –Cross Roller Bearing could replace both Thrust Bearings –90 degrees of rotation (object constraint) –base plate extends 9” from wheelchair
Shoulder Design Shoulder Motor Placed Vertical –Right Angle Gearhead vs.Bevel Gears –Right Angle Gearhead much easier to integrate and only costs $200 more
Comprises of two links Provide support for the shaft and the forearm Elbow brackets introduced Lighter compared to tube Upper Arm Encompasses the parts
Elbow Joint Elbow brackets –attaches to I-beam bracket Bevel gears –2:1 ratio in addition to 50:1 gear-head Compact home position
Elbow Motor Elbow motor placement depends on motor dimensions
Gearheads/Gearing Shoulder : –K & D Magmotor servo motor –100:1 right angle planetary gearhead –477 in-lbs provided Elbow: –Brush Type DC servo motor –55:1 planetary gearhead –160 in-lbs provided –Possible 2:1 gear ratio provided at elbow joint
Torque Calculations x f e d c y b a
Torque Comparisons Shoulder motor on base –torque required: 462 lb-in Shoulder motor placed within arm –torque required: 665 lb-in 44% increase in torque required if both motors were to be placed inside the arm (Both calculations used an application factor of 1.5)
Q: What are the best benefits of our design? Meets all the torque requirements Motor outside of arm reduces torque on motor, thus reducing the size and cost. Length of arm need not be increased to accommodate motor (19 inches of motor; 21 inches of arm) Thinner upper arm allowing compact design Horizontal placement of swivel motor allows lower mounting of arm thus increasing reach A: All of the above
Dimensions
Conclusions Swivel base Vertical shoulder motor Elbow motor inside upper arm Elbow brackets allow compact folding
Questions ¿