Objective Statement:

For this portion of the project, the group made a linkage system that served as a grasping arm. Before constructing the linkage system, a graphical linkage synthesis was created. However, to be sure that the grasping arm had the mechanical advantage to hold the claw and to lift the desired object; calculations such as finding the instant centers and degrees of freedom analysis were conducted. Once finalized and verified via MATLAB, the final assembly was constructed.

Design Constraints

Explicit Constraints:

• Must include at least one four bar linkage

• No counterweight

• 1/4" plywood material

• Servo motor has 180 degrees of motion

• Must mount to 1" x 2" post

• 8 inches between center of drop zone and center of mounting holes on 1"x2" post

• Gears cannot be used to create mechanical advantage

• Wires must be secured and out of the way of arm

• Testing sequence must start with the arm in the up position

• Payload must be lifted 1 to 3 inches off of the ground

• Lifting motion must be activated by a sonar sensor

Implicit Constraints:

• Design must be light enough to not pull over arm

• Arrange it so no linkages interfere with the movement of other linkages

• Can lower to reach smallest payload

• Must have enough mechanical advantage so servo is able to move claw and arm

Team Imposed Constraints:

• Shape of grasping mechanism requires lifting mechanism to be positioned in a way for it to grabbed from above rather than the side

Design Considerations:

This design allows for easier movement and less likely to interfere. The problem with this design is the slider might have to be longer or shorter to make sure the mechanism doesn't move in the resting position. It was too complicated and hard to imagine how the slider would work.

This design is simple and effective which is why it was chosen to be our lifter design. Mechanical advantage can easily be increased by changing the lengths of the rocker, crank, and coupler allowing this design to easily lift the grasping mechanism.

GLS Screenshots

Narrative

When designing this lifter mechanism some considerations had to be made in order for the mechanism to be able to lift the claw. While trying to create the GLS we noticed that a long coupler and a short crank created the highest torque output when plugging the dimensions in MATLAB. We also noticed that shortening the crank length too much resulted in the mechanism not being able to lift the claw and payload high enough so the length of each link had to be carefully chosen to create enough lift and torque.

Mechanical Advantage Calculations

Model