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Overview of Phase 4
Overview of Phase 4
In Phase 4 of this project, we designed a rotating mechanism that would transfer our payload between two locations. This Phase 4 represents the culmination of this entire project because it completes the functionality of our robotic arm. Each group member created a gear train that would be able to rotate the entire robotic arm to the designated degrees. It was important to calculate the correct gear ratio before starting our design so that our gears would not cause the arm to rotate too little or too far past the drop zone.
Design Constraints
Design Constraints
Implicit Constraints
Implicit Constraints
The design must be compatible with Phase 3 of the project
Mechanism pieces would be created of 1/4" plywood using laser cutter.
The servomotor cannot exceed 180 degrees of rotation
The rotating mechanism must fit within 10" diameter circle made of 0.75" MDF. The drop zones for the payload will be located on boards of 0.75" MDF.
Explicit Constraints
Explicit Constraints
The team must complete this phase of the project in two weeks
The mechanism must rotate 180*(N-2)/N degrees, where N is the number of groups in the class. For our class that would be 180*(8-2)/8=135°
Must be gear-driven servo, must travel through at least 150° of rotation during the pickup/drop-off sequence.
The gears of the mechanism must be involuted to allow proper meshing
Gear Ratio Calculation
Gear Ratio Calculation
180(N-2)/N
180(8-2)/8 = 135 degrees
Emma's Design
Emma's Design
Pros:
Gear ratio 1.11:1
Driving gear would need to rotate 150° in order for it to rotate the driven gear 135°.
Moshier's Design
Moshier's Design
Pros:
Gear Ratio of 1.33:1
Driving gear would need 179.5° to rotate in order for it to rotate the driven gear 135°.
Brenden's Design
Brenden's Design
Pros:
Gear ratio of driving gear to driven gear is 1.25:1.
Rotation of driving gear 168.75 degrees causes a rotation of driven gear by 135 degrees.
Cons:
Larger driven gear results in greater force but slower angular velocity.
Rotation Mechanism Design
Rotation Mechanism Design
We chose Brenden's design because it fulfills the requirements of this phase. The driving gear is actuated via a servomotor. The driving gear is rotated clockwise to 168.75°, causing the driven gear to rotate 135° counterclockwise. The driven gear has 30 teeth with a diametral pitch of 8 while the driving gear has 24 teeth also with a diametral pitch of 8. This design utilizes two gears to rotate the robotic arm to the necessary degree to allow for the payload to be released within the drop zone. The only negative to this design is that using a larger driven gear results in slower angular velocity.
Up Position
Up Position
Down Position
Down Position
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