Spring into Summer Ambassador Competition: Robotic Banana Slug–Part 3

2021-10-06 | By Eliot Wachtel

License: See Original Project

Demo and Conclusions

The University of California, Santa Cruz entry for the Spring into Summer Ambassador Design Competition, nicknamed Slugbot is a robotic banana slug inspired by our mascot Sammy the banana slug.

Demo

Unfortunately, this project was not completed within the competition time frame. The code is not fully functional and the pulley system for actuating the slug robot does not work reliably. As a result, we never printed the slug themed casing or the wheels.

What we did finish was the entire electrical system, and base structure (Figure 1).

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Figure 1: Slugbot base structure and electrical system

For the electrical system we have a Arduino Every as the “brain” of the robot, two motor driver breakout boards which run the two geared drive motors and the one encoder equipped twist motor, and a 6 degree IMU, and two limit switches as the sensory input.

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Figure 2: Some of the connectors used on the Slugbot

Mechanically there are five sections made up of four section types:

The head (Figure 3) holds the two limit switches and would have held the IMU had the project been completed.

The switches are mounted upside down but angled upwards so an object in front would cause the arms to rise and warn the slug of an obstacle.

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Figure 3: The Slugbot head with the two “antennae” on limit switches to sense the environment

The two drive modules (Figure 4) hold 1 gear motor each and are mirrored across the middle of the slug.

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Figure 4: The two drive modules for the Slugbot

Motor drivers would have been mounted behind the motor of each module.

The twist module (Figure 5) holds the gear motor and pulley system for twisting the robot during turns.

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Figure 5: The Slugbot’s twist module

This module would have allowed the entire robot to twist as shown in Figure 6.

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Figure 6: The twist module would have enabled the Slugbot to twist

The final module is the tail (Figure 7) which holds the custom 6-volt battery module that powers the entire system.

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Figure 7: The Slugbot’s tail housed the 6-volt battery module

Conclusions

For what we have done with the time given we are very proud, despite not being able to fully complete the self-assigned project.

Our group was a two-person team, and what was planned to be a cute little robo-slug, turned into a near-meter-long monster whose base alone took 11 hours to print (even at the fastest print settings).

The scope of our project got a little bit out of hand, however we pushed to finish as much as we could. The most impactful issue we encountered was in the turning system of the slug. We designed a pulley system which pulled strings to physically curl the slug, but it came with a glaring problem. The size of the slug meant a lot of force was imparted on the strings which led to them slipping on our PLA wheel design. Tension was also an issue with the strings slipping off often. Our lack of motor controllers for most of the project meant we didn’t test the system until it was too late to make big changes, but we already have some new designs to fix these issues planned.

If we had hashed out the small engineering problems, the slug would have been fully capable of movement and capable of navigating autonomously; sensing its environment with its eye stalks (limit switches) and curling up in defense, if something “attacked” (leading to sharp changes in acceleration).

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Thanks to Digi-Key for helping us get as far as we did!