Robotics-Kinetic Sculptures (The Tennis Ball)

December 13, 2018

Introduction: My kinetic sculpture is my first experience of hitting the tennis ball. This is a very memorable moment because, until that time, I didn’t know how to play any sport. Making the kinetic sculpture, I have explored different tools and was able to think about the time I hit the tennis ball again.

Scratch Prototype

What is this: This is the picture of scratch which was the first step to plan and design my project. Even though the drawing may not be the best, I tried to show how the mechanics work. Different from my design right now, this one does not have the linkages because until this part of my project I had no idea on how the ties work. The movements are straightforward as the tennis racquet moves up and down and the ball goes from bottom-right to the top-left.

Challenges: The challenges for my project was coding each actor to do the actions that I wanted to them to do. I tried to make the excited motion after the tennis ball goes over the net to show my excitement to the audience. However, another problem of this motion is that I would have to use too many servos, so I decided to not include this part but only put it in scratch.

Paper Scale-Model

What is this: This is my scale model linkages for the tennis ball. After thinking through many different ways of moving the tennis ball, I have decided to use a 4 bar linkage for my tennis ball. When I push the most extended tie, the linkage on the other side will move. The motion of running the most extensive linkage would be the servo’s job. I made the scale model with a paper because I wanted an essential kind of a structure for my actual project. Even though this was a straightforward job, I have tried using 3 bar linkages and tried out through lego with some ideas from Mr. Beatty.

Challenges: As stated above from the explanation, the biggest problem was to find the best type of linkage for my tennis ball. Originally from the scratch model, I wanted to have two different movements for the tennis racquet and tennis ball. However, I found out that with the three bar linkages, the motions would be too complicated. If using a four-bar linkage, I would be able to connect the tennis ball the tennis racquet together making them move in the same direction. Another main problem I had of this linkage was planning out the where to put this linkage on the box. I first thought of putting it on the bottom. However, this would be seen from the bottom and also the ball might not move over the net. So, instead, I decided to put the linkage hanging on the top of the box. Another problem of this is that because the ball will be moving as a “U” shape, it may not trace the path just like the tennis ball. If it was the original path, it should go downwards, however using the linkage I have, it would downwards–> upwards. Other challenges were small things such as twisting the paper clip to link all the ties and finding the exact sizes so the linkages would move the way I want it to do. While exploring the linkages, I found out that not only the number of ties would affect the movement. However, the sizes also change the motions of the objects.

Adobe Illustrator File

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What is this: This is my Adobe Illustrator file which is used for laser cutting. (The fun part!) First, we used boxes.py to make a box of what we want. I set my dimensions as a 120mm*140mm*110mm box (width *length*height). After that, we got to design our own box using the servo cutouts. The holes on the bottom are for the base to fit in the bottom. We needed the servo cutouts for us to connect the servos which were mentioned from the second step. I made some more holes on the top because I decided to put the ball hanging on the top from the previous steps. There are 7 parts in total because 2 parts on the top-right corner would be for the top part of the box. One has a hole, and one has nothing changed. This is because I have to put the bigger one on top of the smaller one which is the one with the holes and servo cutouts. Other than that, I have other parts such as the “stick man,” tennis racquet, ball, and net.

Challenges: The challenge I had was making the smaller parts. The box was straightforward because it was only using the website and the cutouts that I was given. However, for the smaller pieces, I had to draw it by myself. The net was primarily the hardest because when I drew my net, at first, it wouldn’t fit through the holes I have for the bottom part of my box. Therefore, I had to redraw my net and do draw out the squares again with the arranged measurement. Another challenge was the tennis racquet. At first, I drew all the lines, however as I transformed it, the segments would overlap each other. After that, I decided to delete some of the lines, however, because I drew it with a paintbrush, the paths were so messed up, so I had to laser cut again. Finally, I have erased my idea of lines and decided to use paint is, so I only cut out the border of my tennis racquet.

Fusion 360

What is this: This is the scale prototype that I made with Fusion 360. From the picture, I can see I have made the joints, and I had used about 4 classes to make this box. Throughout my project, I had trials and errors, as of making wrong dimensions for the box. At first, I was thinking of having my sizes bigger such as 300*220*300. However, I found out that this would be too big for just a little amount of parts to the project. The reason why this project took a long time is that I had to make sure every part and every joint was correct. From this project, unlike the ones I showed from the Adobe Illustrator, we are not able to see the servo cutouts. With that, this model would be much more accurate.

Challenges: For this piece of the project, I had to face small but complicated problems. When I started to join all the parts together because the joints were a line segment rather than a flat surface, it was hard to get them all in line. Because of that reason, it took me a long time to join all the boxes. Another problem I had was the lid. From the scale-model, I observed that the top part of the box would go in between the sides making it impossible stay right on top of the box. At this point in my project, I wasn’t able to solve this problem, however, when I made the Actual Prototype, there was a solution to it.

Actual Prototype

What is this: This is my actual prototype for the end of the semester. From observation, we can see that it is not finished. However, I think I have achieved a lot by reflecting from several previous steps. Even though there aren’t any servos or mechanical gears, I have fixed 90% of the problems I had from the earlier stages. I have attached the lid by having another piece of plastic by using the laser cutter and then placing it on the bottom of the top part of my project so that my top would look like it is staying free on the air. I still haven’t put the linkages in the box. However, I have all the parts needed for my project to be done. For now, I am looking forward to finishing this project during the computer science course which I would be taking next semester.

Challenges: There were several problems I had faced making my prototype. The first one was the tennis racquet and the ball. Since my project is about the first time play tennis, essential parts I need are the tennis racquet, tennis ball, and myself. However, two of my essential parts either broke or disappeared. My tennis racquet’s path kept on getting messed up, and because my tennis ball went missing, I had to redo it but didn’t find the one I was going to use. The biggest challenge I faced for my actual prototype is trying to make the top part of my box stay in mid-air which was needed because I will need to hang my tennis ball and make sure it won’t fall down. If I don’t have my lid, my whole project and linkages will not work. Other than that, my challenge was the time. Since I took too much time thinking about my tennis ball linkages, I didn’t have enough time to make the finished product, and with the given time, it is barely possible to make my finished product. This was an unfortunate part of this year’s robotics course.

 

Entry Filed under: 2018-2019,Electives,Robotics. Posted in  2018-2019 ,Electives ,Robotics .


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