Robot Framework Design

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Robot Framework

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Robot framework refers to the supporting structure of our robot; it involves a top plate, 6 shaker cans attached to the top plate, 3 legs attached to the top and bottom plates, a bowl holder plate with wheels, and a bottom plate. The three plates are made of panel boards, and the three legs are made of furring strips.

For the top and bottom plates, we shaped them to be circular as shown in Figure 1 and Professor Skovira helped us with the sawing. Our base is smaller in diameter than the top cover since we need to account for the space occupied by the legs. Specifically, our top cover diameter is 14” and our base diameter is 12”. The furring strip is 8’ in length i.e. 96”. We set the 3 legs of the robot to be 11” and attached them at the edge, 120 degrees apart, to the top cover with the help of Professor Skovira. We divided the top cover into 8 sectors with each spanning 45 degrees, marked out the radial lines and drilled 6 holes along 6 of these radial lines. We decided on 8 sectors and did not place shaker cans on two neighbouring radial lines so we can easily place and retrieve the bowl holder. The 6 holes are 10” from the center of the circle as we want the bowl’s center to ultimately align with the center of the shaker can to prevent spillage during the dispensing process. Professor Skovira also helped us with drilling the holes both on the top cover as well as the bottom of the shaker can so we can screw the shaker cans to the top cover. We then attached the top plate to the 3 legs using screws. This setup can be seen in Figure 2. We finally attached the bottom plate to the legs in a similar fashion.

figure 1	figure 2

For the bowl holder, since there are 4 wheels -- two driving two idle, we decided they will be 90 degrees apart and marked out the radial lines on the circular bowl holder. Based on the size of the wheels and the servos, we decided the bracket will be placed 1.5” from the edge of the circle so the wheels are entirely below the bowl holder. We then measured the distance between the centers of the two holes on each bracket and marked out them out on the bowl holder so we know exactly where to drill the holes on the bowl holder for attaching the brackets. Two of the servos we are using will be driven by the Raspberry Pi and will be responsible for turning the bowl holder. However, two of the other servos are broken and is in place simply to help stabilize the bowl holder. We attached the wheels on these two servos loosely so they can spin along as the bowl holder rotates. This can be seen in Figure 3. We found the midpoint of the bowl holder plate, and used a screw to pin this mid-point to the base. The goal of this attachment is to pin the center of the bowl holder, so that it can rotate in a circle instead of wondering around. To do that, we also need the connection between the screw and the bottom plate to be loose enough so that there is space for the screw to rotate. Thus, we used a small chunk of wood and attached it firmly onto the bottom plate. The thickness of wood allows us to prevent the screw from pulling out and, at the same time, attach the screw loose enough for rotation.

figure 3	figure 4

After every individual component was setup, we inserted the bowl holder plate in between the shaker cans and the bottom plate to finish our robot framework, as shown in Figure 4.