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Previous studies had mainly looked at snake movements on flat surfaces, but rarely in 3D terrain, except for on trees. Li said these did not necessarily account for real-life large obstacles such as pieces of rubble and debris that search and rescue robots would have to scale.
In the code, you can see we have a long list of if else statements controlling the speed of each motor. This code works for our snake and our photocell sensor/motor combination. If you have changed the materials for your snake or find that these values don't work for you, when feel free to change the values until you find speed control that works for you. Our snake is meant to work in low light and at a pretty fast speed. If you want your snake slower, for example, you may want to widen your range of lrValues in the if else statements, so that it will take a high powered light directed at one sensor before the motors reach highest speed. One of the main problems with the previous steps was that each piece of the project was constructed separately, but when added together it created problems in the programming. The photocell sensors required immediate reaction to control the motors, but the groups of LED and vibration motor needed different lengths of delays to control them. Also the LED groups blinked at the same time even though they are supposed to be three separate groups. To control everything in the code the way we need to, we require a timer. Cut two a piece of rubber about 1.75" diameter, so that it fits inside of the vacuum reducers. Cut two pieces of cord about 2 feet long, to act as tethers and to help position the body inside of the skin. If the steps got taller and more slippery, the snake would move more slowly and wriggle their front and rear body less to maintain stability.
The attached graphs show the output angle values of each servo mapped over time, slightly out of phase from each other. The difference is when there is a different offset (delay in the time it takes one servo to get to the angle of the previous one in the line of waves). SnakeBots are currently being researched as a new type of robotic, interplanetary probe by engineers at the NASA Ames Research Center. Software for SnakeBot is also being developed by NASA for them to be able to learn by experiencing the skills to scale obstacles and remember the techniques. Adding the vibration motor is very similar to the LEDs. It does not require to be connected to the 5V power supply on the arduino board, but gets it’s power from the Pin it connects to. We are connecting the vibration motor to Pin 10. It does not matter what pin you connect the vibration motor to, but we wanted to physically separate it from the LED groups for less confusion. To control the motors, we will be getting the base reading from all three sensors first (these are stored in photocellReading#).
Note: an arduino mega is necessary not because of the numbers of outputs but because the flash memory space in the arduino UNO is not large enough. By using the circuit diagram, set up the one LED to the breadboard and arduino. For this step, we removed the photocell sensors, so it would be easier to see the LED circuit. We recommend doing this also, it makes it easier to complete each step without previous work getting in the way of the breadboard, and eventually we wanted to reorganize the breadboard so it was configured as optimally as we could get it. Most likely, you will need to reorganize your breadboard also. We also found that each motor needed a minimum value of speed (ours was 100) to be able to pull the weight of the snake. There could never be a speed value of 0 going to a motor. If a motor would completely stop, it would then take too much work to get the motor moving again.I'm using a servo motor shield from seeed studios, but I am sort of just using it as a perf board, but a convenient one because all the ground and power pins to my servo motor are already jumped together, with a screw terminal for the battery input. And ignore those wires hanging off the board - I had prefiously soldered on female header pins for another use of the board, so I removed them so I could use this here. I eventually clipped them off but you can see them in the pics. Scientists noticed the wriggling portions provided stability to keep the snake from tipping over. As more of the snake reached the step, its front body section would get longer and its rear section would get shorter while the middle body section remained roughly the same length, suspended vertically above the two steps. Prepare the xbee breakout board (solder on the 2 rows of male headers and 2 rows of 2mm xbee female headers)
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