"Walking" Robot - Week 1

In the beginning, Aleja and I wanted to create a robot that moves forward in water. We thought of many animals that swims in the water like the ray, frogs...etc. Since the motor had to be out in the air, we thought making a ray was a bit of challenge because it would move the best if it could go in the water. Therefore, we decided to design a frog that has a motion much like human breast strokes. Two motors were to be used for the frog; one for the front arm and the other for the back legs. A off-centered circular was to be attached to the motor, pushing the legs out as it rotates. The push in the back leg would cause it to move forward. The rubber band tied to its feet part would bring the legs back in. The gears for the front arms would be tilted so that the arm moves in and out pushing the water out of the way. We rejected this idea because the we were not sure if the force on the back leg would create enough forward for the whole body to move forward. Also, it was possible that the rubber bands would undo the initial motion of pushing out the water by bringing the legs back in.

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Our second idea was to create a rowing boat. It would have two gears that are touching perpendicularly. One of the gears would be attached to the motor while the other motor will have a circular piece above it. The circular piece will be connected to a rowing stick that pushes the water out of the way as the circular piece rotates. There would be a wall that, by the time the rowing stick gets to the rear of the boat, lead the rowing stick into the air so it does not row making a circle in the same position. We created a Lego model for it and it is shown below.

When we made it up with Lego parts, we realized that we will need use a lot of Lego parts when we really should avoid doing so. Furthermore, it would be too much in a circular rotational motion when we had to manipulate the rotational motion into some other motion and have the machine move forward. Therefore, this second idea was rejected as well.

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Our third concept was to create a moving dog in the actual dog steps, which is in the order of left front leg, right back leg, right front leg, and then left back leg. We decided to use the off-centered circular piece to generate the force to move the legs forward. The legs would be connected to a horizontal piece with elliptical holes in the connection, so that the legs would be able to move back and forth. However, we had some problems. Once the off-centered circular piece pushes the front leg forward, then the back leg, it would not move forward anymore because the motor would be staying in the same position as described in the "motion" part in the picture. Therefore, we came up with our second design for the dog, in which the motor itself is connected to the horizontal piece the same way as the legs are attached. On the contrary, the back leg would not have the elliptical hole, but rather would form one piece with the horizontal piece. Instead of using a off-centered circular piece, we decided to use a teardrop-shaped piece. Front leg will still be moved forward first and when the back leg gets a push forward from the rotating teardrop-shaped piece, the whole horizontal piece would be moved forward, putting the motor back to its original position. To rotate the teardrop-shaped rotational pieces, we decided to use rubber bands because making gears with Solid Works seemed to be a waste of time since they do not work very well and because we did not want to use much Lego parts. We rejected this idea because we realized that the legs would be too heavy for the friction between the rubber bands and the dowel to create enough torque for the teardrop-shaped pieces.

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Our fourth idea came from the motion of a gorilla as illustrated in the picture above. It was just a simple design because after coming up with first three reasonably complicated designs, we realized that making the machine move forward was more important than the complexity in mechanism. This gorilla robot would move forward by the rotating four arms that would stamp on the ground, lift up the body and swing the body forward. We made a model with form core and the picture is provided below.

We rejected this idea because it was moving almost in a rotational motion and because we decided that it was too simple.

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Our last idea is based on the motion of a hopping rabbit. This design is the one that we decided to stick with because it is not in the rotational motion and is not simple in design. It will have two front legs, the connecting piece on each side, two back legs, and the body part where the motor will be fixed. The two front legs will be connected to the motor along with the connecting piece. They will be tight fit so that they rotate with the rotating part of the motor, which thankfully is a hexagonal shape. We have decided to create the holes into a hexagonal shape so that they have enough torque to rotate. We also have decided to make two types of front legs: a pair of walking ones and hopping ones. The hopping ones are to be longer in size so that they lift the whole body of the rabbit robot (It is illustrated in the pictures below). The front legs will have rubber bands glued on the bottom of it to create friction so that it does not slip off the ground, hopping in the same position. The body part where the motor will be placed will be made up of three pieces: the bottom piece and the two identical pieces as walls. The wall pieces will have two teeth that will fit into the two holes on the bottom piece like puzzles. In between the wall pieces will be the motor. We will use 1/8" for every parts except the two back legs; we will use 3/16" for stability. We will use 1.6mm stoppers to keep the front legs and connecting piece in place. We will use 5/4" long steel alloy dowels to connect the back legs to the connecting pieces. 1/4" dowel pins will be used for the ends of the steel alloy dowels. In between the connecting piece and the back legs, we will put two 3.2mm stoppers to keep the distance. The back legs will rotate 180 degrees to the front. Then, the body part will rotate 180 degrees with the help of the two front legs.

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Motion Module

I worked with Kelsey Tempel on this Motion Module Project. We wanted to produce a vertical motion by rotating one of the dowels. At first, we thought of creating a vertical object that sits on top of a tear-drop shaped piece which moves up and down as we rotate the off-centered circular piece. However, we came up with the idea of "hanging" something so that every time we rotate the circular piece, the hanging object can move up and down. We decided to make a square window on our two walls so that it is like a frame in which the hanging object appears and disappears as it moves up and down. My partner brought her cute little turtle accessory for the hanging object so it is like a peekaboo.

We decided to have four dowels; 2 for the bottom and the rest 2 for the tear-drop shaped piece and the rotating piece. Only the dowel for the rotating piece was to be 14cm in length for its handle while the others were to be 12cm in length. The holes in which the dowel was to go through had two types, a tight one and a lose one. The blue circles in the drawing above is a tight one for which the dowel should be fit too tight to rotate. For its tight fit, we decided to make the diameter of the hole to be 6.29mm since the diameter of the teflon rod was 6.3mm. The holes designed for the rotating piece and tear-drop shaped piece were lose holes, which are circled in green in the picture above. They are 6.5mm in diameter but we had to enlarge the holes because it was still too tight for the rod to rotate smoothly. Total of 4 stoppers were used at the ends of the two upper rods to hold them from moving left to right since the tear-drop piece had to be on the rotating piece. Two stoppers were used for hanging the creature for it to not slide off the rod.

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We then made our model using the form core and tested it out. From this model, we realized that the square window on the walls did not have to be so big. Therefore, we decided to shrink its height from 6cm to 4cm. Also, we discovered that the rotating piece(big circle) was too big that the tear-drop shaped piece sometimes went over to the other side and got the hanging creature all entangled up(drawing below demonstrates this). As a result, we ended up reforming our rotating piece into a weird looking shape that will still allow the tear-drop shaped piece to move stably.

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Now that our model was ready, we started our job on Solid Works. Since our two circular pieces were not circles, we had to estimate its shape when we tried to draw it on Solid Works. Here are some pictures.

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We then went ahead to print our model in the laser cutter with which we had some difficulties. Next time, we will have to double check whether or not all our pieces are extruded and saved on our thumb drive. We will also need to make sure that we know the exact thickness of the delrin piece before we put it in the laser cutter, because our piece did not cut through all the way. Anyways, we were able to get all the pieces out with some labor involved and get the model working just as we envisioned it to.

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Here is a video clip for our Motion Module.

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ITERATION

We had to make a simple iteration to our Motion Module Model because if was not strong enough to hold the upper dowels in place. We, therefore, added some more stoppers in and out of the upper dowels to keep it from moving sideways. Here are some pictures.



Here is a video of our improved Motion Module.

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