Sawppy the Rover Conquers Backpack

Once Sawppy received its new power system that could deliver the amperage necessary for challenging climbs, it was time to see what the rover can do. Here’s video footage of a particular test where it climbed a backpack.


The most impressive part of this particular demonstration is the height of that backpack. At its highest point, the backpack was approximately double the diameter of Sawppy’s wheels. This was a little difficult to see from the angle of the above video, here’s a picture taken from a different angle.

Sawppy and Backpack.jpg

Credit for this climbing ability goes to the rocker-bogie suspension geometry copied from real rovers JPL sent to Mars.  It allows real rovers to roam a planet with no roads, and on this planet it allows little rover models to climb obstacles better than other wheeled vehicles of similar size.

While the suspension geometry is working marvelously, this series of climbing experiments exposed other limitations. Sometimes Sawppy’s servo motors do not have enough torque, and that is an understandable weakness of these $15 serial bus servos. Like we’ve said before: it’s a trade off for hitting its price target. Also, the wiring harnesses need to be better managed, it snagged on a few obstacles that the rover otherwise would have no problem climbing.

And lastly: grousers on these wheels only help in some situations. Sawppy’s climbing ability is frequently limited by lack of traction. The current design works well when there’s something for the grousers to grip – for example the rough texture of a backpack – but sometimes the grousers can’t find a feature to grip onto. This leaves us with the very limited friction of hard PLA plastic.

As an experiment to help Sawppy get a grip, we’ll try coating the wheel surfaces to see if we can improve traction.

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