Introduction and Background
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Initial design of the mechanism was performed using the PMKS application which allowed me to quickly insert links and joints of different types and view the resulting kinematics. I eventually settled on a 5-bar linkage as shown below, after I observed that when the left end of Link 4 is close to the origin, Link 3’s center of rotation will nearly coincide with that of Link 2, resulting in little motion in the rest of the system. Assuming that Link 3 is slightly longer than Link 2, as long as Link 2 is pointed to the right, there should be little to no movement in links 4 and 5.
The mechanical design of the mechanism was driven primarily by the availability of materials. Birch plywood was selected as the primary building material since arbitrary 2D links can be easily cut using a laser cutter. Screws seemed to be an ideal choice for the joints since they can fasten linkages together while also allowing for relative rotation.
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The PMKS application was used for early design of the mechanism. An early draft of the mechanism is shown below. The later kinematic analysis and visualizations were completed using Matlab. The files used are attached below.
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Final Prototype
The final prototype can be seen in motion below. Notice that for approximately half of the rotation of the input, the rightmost link does not significantly move, while for the rest of the rotation, it rocks back and forth.
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