Hydraulic Robot

The first project we are doing in Engineering Design is a hydraulic robot. The challenge is to make a robot that uses hydraulics to pick up a tennis ball, move it, and drop it in a cup. We are working in teams of 3, and each member will be focusing on a certain function of the robot. The three functions are grabbing the ball, lifting the ball, and turning the robot to put the ball in a cup. There are many questions we need answered to succeed at this project. First off, we need to understand how to convert linear motion to circular motion. Another question is how do hydraulics work?

How We Completed This Project

The first part of building the grabber was to construct the frame out of mainly wood. I cut wood and made a point of rotation. This frame could open and close to simulate grabbing a tennis ball. The frame is made of all plywood. I used a Makita drill to make a point of rotation, and the wood was cut with the band saw. The prongs that scoop under the tennis ball(as shown below) are two screws.

Above is a picture of how the grabber frame picks up a tennis ball. The prongs slide under and the ball is held in place.

The next step I took was to design a housing for the syringe. I cut a small square of plywood, and used a Makita drill with a hole saw bit to cut a hole just larger than the syringe. The syringe could now be secured in place.

Now that I had a housing for the syringe, I needed to create a point of rotation to attach the syringe to the grabber. For this I made a small hole through both the wood and the syringe. For the axle I used a nail.

The next step towards having a functioning grabber was to secure the syringe in place. For this I used a hot glue gun to glue the syringe in place. Finally I added rubber bands because after some testing I came to the conclusion that the syringe has more pushing power than pulling power. This meant that adding rubber bands would help the grabber open and drop the ball, but it could still grab it securely. I also cut a small piece of plywood that could be a point of connection between my part and the lifter.

Here is a video of the grabber being able to grab the tennis ball but not release it. This was taken before the rubber bands were added.

This video is of the grabber successfully picking up and dropping the tennis ball into the target cup. This test I added rubber bands and used water. The water is better than air for pulling the syringes out so it worked.

Now that I had finished the construction of the grabber, it was time to work on integration of the three parts of our robot, the big turner, the lifter, and the grabber. Since I had already put a plate for connection, this was very simple. But we had to figure out how far from the center of the robot we wanted the grabber to be. The closer it is, the less force is required to lift it. So, we went with having it closer to the center.

Finally, after lots of trial and error, failure and success, and building and rebuilding, we had our final robot built. The lifter was something I worked on a lot because we had to almost completely redesign it. We realized that instead of pushing the weight it would be more effective to pull it. So, we had the arm pulled by the hydraulic syringe. We didn't do much testing before the final test. Below is the video of our final test.

How It Turned Out

Our robot worked successfully! After many failed practice attempts, our robot worked fully in our one chance at completing our goal of picking up the tennis ball and dropping it in the cup. Not everything went quite as planned, such as how we picked up the ball. Instead of sliding the prongs under the ball, I had to essentially dig one screw into the ball and keep it in place. This worked, and the rest worked pretty smoothly. In conclusion, we met all project goals successfully. We started our grabber above the ball, went down and grabbed the ball, turned it 180 degrees, and dropped it in the cup while only touching the syringes. We used many points of rotation to reach our goal, and also efficiently converted linear motion into circular motion.

The overarching questions for this project were simple questions about how hydraulics and motion work. The first was how can we convert linear motion into circular motion? And the answer to this is simple. To convert motion you must use a point of rotation. The next question was how do hydraulics work? Hydraulics work with two plungers. You push on one and the air or whatever substance inside the tube connecting the cylinders has no where to go but the other direction therefore pushing the other side out. The same works with pulling, if you pull one side the other side pulls too. Something we learned was that hydraulics have much more power and force pushing than pulling. Most of all, we learned how to draw orthographic and isometric drawings from either looking at an object or as a brainstorm of an idea

Conclusion

This project I learned many informal lessons in fabrication. Since I hadn't been in the shop for a while I had forgotten a lot. One informal lesson I learned was that when connecting two pieces of wood together with screws, always drill a pilot hole. At first I thought I could do without, but after seeing that it was necessary I always made a pilot hole. Another lesson I learned was when drilling vertically to make a point of rotation, make sure before you drill the pilot hole to check if the drill is straight up and down. Without the drill press it is hard to make a perfectly vertical hole but you can get close by being careful about it.

If I were to start this project over, there aren't that many things I would do to improve my grabber. I would try to make it a bit smaller and lighter, and I might make it simpler, but it wasn't very heavy and the great aspect of it was it had lots of room for error to still succeed. It didn't have to even use both prongs as I learned during our final test.

I thought this was a really fun project. I thoroughly enjoyed this challenge. It was difficult but very possible. I liked that it was very open ended and we really had to design first then build. I also liked that we had lots of work time and got to learn for ourselves what worked and what didn't. My favorite part was that instead of just results or data, you had physical success or failure.

If I were the teacher, I would not change much about this project. I think one interesting change could be that you could have the choice for extra credit of having to make a grabber that could pick up a tennis ball or skittles. That would be a challenge!