Moving an Oreo cookie from its container, dipping it into milk, and bringing it to the feeding position is fundamentally a position and vel
ocity problem. To solve this we would need to create a linkage that picks up the cookie, rotates 90 degrees, dips the cookie, and then rotates 90 degrees to feed the operator. This must be done slowly enough not to lose the cookie during this process. The challenge in designing the linkage came from obtaining the three stops.
Figure 1: Three Stages of Operation
One of the challenges we faced when designing our pick and place mechanism was how to achieve a vertical profile for the picking stage. Our initial ideas all involved motion profiles that followed a parabolic profile downward, which would not work for our desired motion because this type of profile would knock the glass over in the dipping stage. We also knew we wanted some way to actuate the end effector to a position where the cookie would be easy for the consumer to get. The utilization of MotionGen played a crucial role in the iteration of the design to achieve the desired motion profile. By adding links and adjusting link lengths, we were able to see how these adjustments would affect the motion profile of the end effector.
Figure 2: Iterations of mechanism design through MotionGen
MotionGen proved to be a helpful tool as we were able to visualize how increasing the length of the top two grounded links would change the amount that the end effector would rotate in the serving position. Additionally, we were able to see how changing the bottom right grounded link affected the vertical motion that we desired.
Figure 3: Linkage Design in MotionGen (From left to right: Dipping Position, Serving Position
Figure 5: Linkage Design in Solidworks - Dipping Position
Figure 6: Linkage Design in Solidworks - Serving Position
Figure 7: Pick and Place Mechanism in Motion
Our final step in this process was to assess the real-world feasibility of our mechanism by creating a prototype. We constructed a low-resolution prototype using leftover acrylic from a previous project, optimizing the design by reducing the size of the links to minimize material wastage and using screws as placeholders for joints, as shown in Figure 8. This initial prototype highlighted the importance of spacing between links to prevent overlapping motion. Subsequently, we refined our design, leading to the second iteration of the prototype, which features smooth motion and a desirable position profile. This iteration features smooth motion, with the only remaining additions being a mechanism for grabbing the cookie and a rotational element to account for the third stop.
Figure 8: First Iteration of Prototype
Figure 9: Second Iteration of Prototype