"Walking" Robot - Week 3 [Hopping Rabbit]

After creating the parts in Solid Works, we went ahead and printed them out. We assembled all the parts. Then we encountered six problems.

THE SIX PROBLEMS
1. The shaft on each side would spin at different rates.
2. Some more stable friction was needed in the front leg to not slip off the ground.
3. The back legs (larger legs) needed some more weight on the rear part. Otherwise, it the pointy front part would touch the floor when it moves forward and would flip over, causing a disaster.
4. It needed something springy on the bottom of its back side to support it. Otherwise, the body part would rotate instead of the legs rotating.
5. We needed to find out the right orientation of the front leg and the connecting rectangular piece (the one that connects the back legs to the motor shaft) in order for the rabbit robot to "hop."
6. We needed to find a place for the batteries. Since it was pretty heavy compared to the other parts of the robot, misplacing it could cause a serious balance issue.

Here are solutions that we came up for the problems.

THE SIX SOLUTIONS
1. Change the two separate shafts into one long single piece so that they spin at the same rate.
2. Stretch rubber bands and tape it onto the front legs for friction.
3. Drill 3 holes into the back legs. Add screws (head piece and the tightening piece) to the holes. Achieve stable balance either by adding or removing the tightening piece.
4. Use the red sponge form to support the body because it has the needed "springy" characteristic.
5. Since the shaft is hexagonal, experiment all six orientations and find out the orientation that would allow the robot to hop forward.
6. Observe carefully whether the body part leans forward or backwards when it moves forward. If it leans forward then place it on the back of it and vice versa.

When taking Solution #1 into action, we had some difficulties with our motor. It would make this loud noise when it is on. We later figured out that the motors were spinning in the opposite direction, and because of the friction, it was making the sound. We, therefore, had to sauter our wires again so that the motors would spin in the same direction.

When processing Solution #3, we added two screws (including the head piece and the tightening piece) for the middle and the back holes. We only added the tightening piece to the front most hole for the better balance in the leg when moving.

For solution #5, we did try all the orientations. The only orientation that would allow the robot to hop forward had the connecting rectangular piece (the one that connects the back legs to the motor shaft) 90 degrees before the front legs.

For solution #6, we observed the balance of the body part when moving forward and came to conclusion that it actually leans a little bit forward. So, we decided to place the batteries on its back side, which worked just fine.

We ended up not using the jumping legs that we created on Solid Works because out shorter legs were working just fine. We figured that rabbits don't necessarily have to jump as long as they can hop :)

We also tried to add some more decoration to our cute rabbit robot: something like its face and ears. But we ended up leaving it look "modern" and robot-like without much rabbit looking decoration for its balance.

Here are some pictures of our final outcome :)
We like it very much!

Here is a video of our hopping rabbit!

"Walking" Robot - Week 2 [1st Print, Iteration on Solid Works]

We have printed the parts that we made in the Solid Works and here are some pictures below.



We attached some rubber bands to our front legs to create friction so that the front legs can drag the body forward. However, we had an issue with the body. We needed some buttress on the bottom of the body piece for it not to fall backwards. There was no supporting piece to hold the motor upright. We, therefore, attached some red foams (as shown in the picture) to see if they help. They did help and we decided to make them in Solid Works, print them out and add to the bottom of the body. We also had some problem with the back legs (large legs). Even though they were balanced by having the hole in their center of mass position, they would fall backwards whenever they rotated. To improve on this, we decided to give some more weight to their lower parts to help on their stability.

* * * * *

Here are some newly designed model in Solid Works.



We created two new puzzle pieces (second picture) that would fit in the four new rectangular holes on the bottom of the body piece (first picture). We will have four pieces of ones shown in the third picture. They will fit into the two new puzzle pieces (second picture). This may sound confusing but the fourth picture illustrates it well. We also have created two holes on the back leg to give it some more weight and thereby easier and more stable in balance.

"Walking" Robot - Week 2 [Solid Works]

Making parts of our "Rabbit Robot" in Solid Works was not much of a challenge. We easily drew the parts using straight lines and "spline" method. Here are some picture of the parts in solid works.

The above are the body pieces where the motor will be placed. We will need two of the piece on the top picture which will tightly fit into the rectangular holes of the piece on the bottom picture, creating two walls around the motor.




The top picture is the linking piece between the back legs to the motor so that the back legs and the body take turns in motion. We also created two types of front legs. One is called "jumping leg (bottom left picture)" and the other is just a regular front leg (bottom right picture). Jumping legs will make the machine "hop" just like rabbits do. But, it is only to be used if the regular leg works.



The back legs of the rabbit, however, was a bit of challenge because we wanted the leg to balance in the air; we needed to find out their center of masses in order to do so. Thankfully, the Solid Works had a system that would find us the exact position of the center of mass in a piece only if we knew the density of the material. We measured the density to be approximately 0.05 lb/in³, and was able to get the hole in the right position.