Design Process - JS

Step 1 - Simulation and Mechanism Dimension Tuning:

The first design focus was to tune the link lengths such that the slider would move with nearly constant velocity for a significant portion of the input link rotation. The Planar Mechanism Kinematic Simulator (PMKS) facilitated this step in the design process as simulation should drive design decisions. The link lengths and pin locations were easily adjusted and moved in PMKS until the slider moved with constant velocity on the drive stroke. The final design in PMKS is shown in the video below:

Once the animation demonstrated the slider moved with constant velocity, the kinematic data was downloaded and plotted in MATLAB for confirmation. The plot confirms the slider moves with roughly constant velocity for about 200 degrees of input link rotation:

Step 2 - Material Selection and Final Dimensioning:

6mm pins were initially used for the mechanism joints, so served as the basis for the rest of the mechanism dimensions. I wanted to the mechanism to be small enough to fit in a backpack, but large enough that it was easy to operate and visualize all the links moving together, so kept link lengths under 12 inches. Additionally, smaller links have less mass and small moments of inertia, so would be easier to drive with a powered effort source. Following simulation and analysis in PMKS, the link lengths and pin positions were all dimensioned and drawn in SOLIDWORKS. I planned to 3D print the links and laser cut a piece of acrylic to serve as the mechanism ground. Final link dimensions are all included in the attached drawing: