The final prototype of the robot was successfully able to roll forward and backwards. It was able to roll for about three minutes on one 16 g cartridge of CO2 and was able to achieve a speed of about 6 m/min. It was not able to turn due to a manufacturing issue with the turning channel. Due to inconsistencies in the thickness of the long channel, it would bubble at certain points, instead of inflating evenly. There is a different prototype which has a more evenly cast channel. This one inflated uniformly, demonstrating the ability to turn, given proper manufacturing of both turning and driving channels in one mold. The timing of channel actuation was still an issue, as each channel inflated slightly differently than the next, causing non-uniform angular velocities. For future improvements, some sort of position feedback would allow for more accurate timing of channel actuation.
Final Prototype on Test Day
The turning did not work on the final prototype due to manufacturing issues; however, the turning had worked on the previous model shown below, using the same type of channels. The silicone on the final cast must have had minor inconsistencies in thickness, causing bubbling at certain points, instead of uniform inflation along the length of the channel. Without manufacturing issues, the final robot would be able to turn, drive forward, and backward.
Cast with uniformly inflated turning channel.
Here are some measured characteristics of the final robot:
Roll Speed Achieved: ~6 m/min
Duration of CO2 Cartridge while Rolling: 3 min
Mass of Silicone Body: 952.9 g
Mass of Internal Components (with full 16g CO2 cartridge): 516.4 g