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The force profile/mechanical advantage of the end effector should ideally peak at the maximum close position (small relative distance between critical points) to maintain adequate contact with the object being picked up. The plot below demonstrates a possible ideal plot of mechanical advantage, calculated from the design of end effector iteration twowith a peak mechanical advantage at small linear displacements (indicating a closed configuration for iteration one). For future iterations, a better alternative would be to design a system that achieves a mechanical advantage that approaches infinity as the linear displacement decreases.
Mobility Analysis
Kinematic Positonal Analysis
We chose to focus on the kinematic/position analysis for the overall linkage system because its motion determines the opening/closing/position of the end effector and the rotation/displacement of the package volume.
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The analysis below will focus on the end effector. We chose to focus on the mechanical advantage of the end effector because the main goal of the end effector is to maintain adequate package contact through force applied from the end effector links.
First Iteration Animation Second Iteration Animation
First Iteration Mechanical Advantage Second Iteration Mechanical Advantage
From the graphs above, it can be seen that the second iteration has a slightly more favorable mechanical advantage trend than the first iteration does. With the first iteration, the mechanical advantage peaks when the mechanism opens and drops when the mechanism closes. This is validated by the fact that the mechanism moves quickly when approaching the vertical portion of the curved slot as the vertical input force aligns with the direction of motion. The second iteration continues to have the same issue, where mechanical advantage peaks at an open configuration. It's worth noting that the reason for iteration was purely as a proof of concept for a redesign due to manufacturing concerns with slots overconstraining the system and providing excess friction.
For future iterations, the movement of the joints constraining end effector link motion needs to be inverted, initially moving with a vertical downward portion of the arc and ending with the horizontal portion of the arc for opening and vice versa for closing. To further increase the mechanical advantage, we would like to pursue lever stacking, in which multiple levers are coupled together to vastly increase the force output. As the second iteration proved, slots overconstrain the design of our system, which means that our project will likely not include slotted pathways in the final iteration.
Physical Prototype Design Process
Prototyping Reflection
Bill of Materials: