Our brainstorming process is divided into two separate parts. The first step was brainstorming the arm mechanism. We started with the desired position profile, which is based on the problem we decided to address. An image from our brainstorming stage about the desired position profile can be seen below on the left, and a sketch on the linkages on the right.
Since the desired position profile was known, the software MotionGen was used to generate different arm designs. MotionGen was helpful because it can show the position profile of a link based on an input. A final design was made in MotionGen with a position profile that matches what we wanted.
Brainstorming for the claw did not start until the arm design was finalized and prototyped. Once we knew that we had a working arm, we then started designing the claw. The claw brainstorming had the most variance as we researched different methods of coupling the grab and release of the claw to the constant movement of the arm. A functioning claw would require the successful implementation of several constraints; it needed to open and close at very particular instances along the arm traversal without independent actuators. Although designing a cam system would have been the easiest way to achieve this motion, we wanted to be creative about our implementation. Ideas included a linear gear system and some sort of escapement mechanism
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. Initial sketches of a proposed linear gear system are shown below
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Although the linear gear system could have worked, it was theoretically unreliable since it used the force of gravity to transfer the pinion gear between separate linear tracks that would enable extension and retraction. In addition, with the scope of this class
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centered
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on achieving complex motion through linkage systems, we decided to
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attempt an implementation with the escapement mechanism
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Once we finally began to implement the claw, after many unsuccessful attempts with the escapement mechanism, we decided to transition to a ratchet and spring-tensioned claw in which mechanical levers attached to the claw would engage to enable opening or closing at the respective ends, shown below.
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