I used kinematic analysis to plot the motion pattern of the output of my mechanism. Thanks to the analytical tool I build in MATLAB, I am able to observe how changing the parameters of the mechanism affects the output motion.

In my physical prototype, I am limited by the variety of Lego pieces that I own. In Matlab, I was able to be much more creative and experiment with various gear ratios and link lengths that would have been impossible to create with Lego kits. In order to allow for easy changes to the variables and quick runtimes, I needed a fully analytical solution. I used MATLAB’s equation solver to derive analytical solutions, then input the solutions directly into the body of the code to reduce processing load.

The quadrangle on the right represents the approximate shape of a lens on a pair of eyeglasses. I learned from this analysis that the coverage was not very good and created an irregular shape that does not fit the profile of lenses.

Figure 6. Motion path of physical model.

I iteratively changed the link lengths and gear ratio and eventually began to notice a new group of patterns that were less random and much more useful for cleaning lenses.

I achieved a dense and approximately rectangular motion pattern by using a 1-20 gear ratio and varying several link lengths; most notably, the crank length of the blue four-bar is shorter.

Figure 7. MATLAB Model, links and gear ratio have been changed to achieve a different output pattern

One interesting thing that I found was that changing the link lengths affected the region that the output motion covers, while the gear ratio affects the path the output takes to cover that region. By changing the gear ratio from 1-20 to 1-1.05, I created a new pattern for wiping lenses.

Robot Mechanism Design

4. Wiper Kinematic Analysis

MATLAB Code: RMDproject.m