Final Design Demonstration

Modified MATLAB Solution

We used the following equations to place constraints on our system. We wanted both the bottle and the glass to be vertical at their lowest points and go to some given max angle. This placed two constraints equations on the problem. Using dimensional analysis and these constraint equations, it made it possible to only have to iterate over the length of c and dx. Lengths a and b were calculated from c and dx. This made our code much more efficient.

Following our observation that some of the link lengths were too small and therefore needed to be altered, we ran the MATLAB program again to solve for new link lengths with an added input constraint: ranges of the output link length, which was limited between 0.25 - 3 (non-dimensionalized). Our final solution is plotted in the graphs showing output link angles vs. input link angles for the glass and bottle four-bar assemblies, respectively. We determined that our solution generally represented the motion profile well. Notable differences are seen in the bottle assembly solution. We have determined that the sharper output link angle change in our solution compared with the desired profile cannot be adjusted with the link length. The full lists of the non-dimensionalized link lengths, phase angles, and other parameters for the glass and bottle assemblies that we solved for in the MATLAB program are documented in Appendix IV.

Design Modifications

In the final prototype, we modelled the entire assembly that we planned on manufacturing and added all of the following: mountings, bearings, metal shafts, spacers, nuts, bolts, screws, pulleys, belts, bottle/glass grippers, and motor in Solidworks. Every linkage was laser cut out of acrylic sheets, mostly because we were concerned about the weight of the assembly and the capability of the motor to drive it without stalling. All of the added components were purchased from McMaster-Carr, except for the bottle/glass grippers, which were 3D printed out of PLA material. Velcro straps were added to the grippers to allow the grippers to adjust for varied diameter bottles.

We had decided to use belt pulleys to drive the input links. The tension of the pulleys can be adjusted by altering the position of one of the linkages; this is facilitated by slots that are cut out from the mounting board, which was made of acrylic in the final design. In addition, we double-layered several linkages to increase their combined stiffness, since acrylic is moderately elastic and deflects easily. However, acrylic is still much easier to machine and replace than metal, which could also be too heavy for our assembly. For the mounting and any 90-degree attachment, we decided to use metal L-brackets to ensure as minimal deflection as possible. We were especially careful with the mountings for the glass/bottle linkages, since those were especially heavy components.

Overall, the design features of our robot are that it is modular, adjustable, and easy to manufacture. 

Video: Final Prototype with Real Glass/Bottle