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With the design constraints set, the team went to work brainstorming many ideas. 
The first idea that the team landed on is shown in Figure 2. This design idea was to use a four-bar linkage to actuate the linear bar. The problem with this first design was that the linkages would never be able to disconnect from the drive motor without an extra mechanism, but provided the linear actuation part of the mechanism with low friction.
Figure 2: Design Idea One. Perform linear translation with a four-bar linkage
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To try and design a simple method to decouple the drive motor, since they have immense friction when trying to back drive. The next idea the team had is shown in Figure 3. This drawing shows an idea where a drive motor would drive a swivel block that was on a lead screw. The swivel block has a lever that would drive the actual rail the robotic gripper was attached to when spinning in one direction. Then when the user want to release the user would spin the motor the opposite direction to quickly release the spring loaded block. This mechanism would work in concept, but with so much force on the spring loaded block, the lever action to turn the drive block out of the way would never open with just spinning the motor the opposite direction.
Figure 3: Design Idea Two. Create a linear translation with a lead screw and sprung shaft that unlatches to release the spring-loaded block.
Another idea that the team had to drive this linear actuation rail connected to the gripper is shown in Figure 4. This drive mechanism was based off a rack and pinion design where a drive motor and gear would be connected to the spring-loaded shaft that drives the entire assembly to close. When the user was ready to release they would be able to disconnect the gear from the rack and spring back. 
The issue with this design is that the motor and everything would be moving as one, which add more weight that the spring had to force backwards.
Figure 4: Design Idea Three.
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Rack and pinion design for opening and closing the gripper
References
[1] R. Acharya, E. J. Challita, M. Ilton, and M. S. Bhamla, “The ultrafast snap of a finger is mediated by skin friction,” p. 12.
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