User:Davidmichael47/enes100/fall2013/p2BioInspiredRobot504

Problem Statement (Finish description)

 * 1) Design a robot that mimics the motion of a living biological organism.
 * 2) Use 3D printer to fabricate parts for the bio-inspired robot.

Conceive

 * 1) Determine the living thing to mimic.
 * 2) As a team, we narrowed our choices down to a rat, a cat, and a snake. The team decided that the snake would be better to mimic due to their simple design and assumed simple locomotion.
 * 3) Determine the mechanics of motion.
 * 4) Snakes move using their muscles and their scales. Two possible mechanics of motion for the robot would be:
 * 5) Use rotating skin to move the snake.
 * 6) Use bone structure to move the snake.
 * 7) This video shows how the snakes move around. We will attempt to simulate this type of movement with the bone structure to lift the snake up while it moves and the skin to move it forward. The skin should also be smooth when going forward and ridged at the back in order to mimic the snake scales.

Design
To fit a micro-controller in the robot without making the snake too big, the Really Bare Bones Board Kit will be utilized as opposed to the Arduino Uno. The board will be integrated onto the snake head, which means that wires will have to be wired through the bones in order to connect to all the servos that we intended to have in the design.

The initial test with a servo connected to the RBBB was a success. More testing will be done by Renita to find out how to change its speed and how to change its movement to be smoother or jerkier.

Bones Prototypes
 File:Prototype_1.JPG|First printout. Prototype 1: The first prototype was created and printed by Ed. Because it was just a mock-up, the print was small and done with medium resolution. The result is this ball and cup. Problems found with it were the fact that the ball will not stay inside the cup. The medium resolution also led to a grainy object, and it was found that the ball would not freely move inside the cup due to that. Also, the fact that it was printed small meant that it easily broke. Prototype 2:

The idea with this prototype was to fix the problem with the cup and ball parts breaking off of the middle cylinder. Unfortunately, the way it was printed the connecting parts were hollow, and it easily broke apart. This problem may be contributed to the way 3D Tin makes the designs and files.

It was also noted that because of the way the team is printing the ball and cup design makes does not allow for the strongest printout. This page shows research of what types of PLA should be used for rigidity and strength:User:Medelen8/ENES100/MakerBot_PLA_Implement

Skin Prototypes
The first printout of the skin showed that the design had flaws. One of the main flaws was that the shell was hollow instead of solid, making it too weak. Because of that, the ridges were not supported and are easily pulled apart. Another flaw was that the ridges were to small for their intended purpose. The ridges were supposed to be filled with Pliobond to allow the snake skin to grip to surfaces and gain traction. The new prototype is in progress and will have a thicker shell. The ridges will be wider to allow for the Pliobond to be installed.

Work with Autodesk 3DS Max
Autodesk 3DS Max is free for students and is useful for creating and editing 3-dimensional objects. [This youtube tutorial] is good as a starting point of how to create objects and subtract with ProBoolean functions.

With Autodesk, another version of the ball and socket joint was created. As evidenced in the mesh images, the joint does not have the mesh going into each object, which was what created the 'holes' in our final 3D Printout. A trial print has not been conducted. Future students for this project should try printing a similar object using Autodesk 3DS Max as opposed to 3DTin or Google Sketchup.

Movement Work
Renita, Ed, and Jovy continued working with cardboard mock-ups of the snake bones to show how it will move. This time, a motor was used as opposed to a servo. The advantages of a motor would be the small footprint of the motor and its movement (full rotations as opposed to 180 degrees). Disadvantages would be that a motor connected to an Arduino will degrade the Arduino due to its requirement of more voltage and current. Renita and Jovy are researching how the motor shield is used to control the DC motor from the Arduino and wants to create a RBBB version of the motor shield. This site has a good tutorial on how to run a motor without a motor shield, but using a resistor, a transistor and a diode. This site has a good introduction to motors. The cardboard mockups are connected to each other with string, which is then connected to the motor. When the motor spins, one side of the string will pull and the other side will release. This is one way to have the bones 'wiggle' back and forth.

Next Steps

 * 1) Decide on whether to use the servo or motor.
 * 2) Research on both will have to be done.
 * 3) Re-visit the snake skin design.
 * 4) Complete 3-D model of snake bones to print without weak spots.