Chumby controlled mechanum wheel robot

[Madox] gutted an Insignia Infocast to use with this robot. Insignia is Best Buy’s house brand and they partnered with Chumby to make their Infocast line. If you can find a used or clearance model it’s a great way to get yourself and embedded Linux board for a project like this one.

The body and wheels are 3D printed, with design files available at [Madox's] Thingiverse page. The mechanum wheels work amazingly well, using seven bearings each for smooth operation. The body itself includes a holder for two groups of batteries. One of those battery packs powers the Chumby board while the other is used to power the four servo motors responsible for locomotion. To simplify the electronics [Madox] chose to use a USB servo drive which only set him back about $20.

We’re not sure what the USB dongle on top of the robot is used for. We’d guess it’s a WiFi adapter, since the machine sets up its own access point to act as a controller. But we thought Chumby boards had WiFi built-in. At any rate, check out the video after the break where you can see an Android phone driving the little bugger. There’s a flaw in the code that prevents side-to-side movement, it gets fixed after a video break at about 2:15 and everything is peachy after that.

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Tricycle robot using omni-wheels

[Markus Gritsch] built this six-wheeled robot using omni-wheels. Two wheels are used on each axis in order to ensure perpendicular rotation is possible no matter where the axis rotation stops. The wheels have also been improved by dipping the elliptical components to give them a rubbery coating.

The robot gets its commands wirelessly from a separate controller unit. That controller, as well as the bot seen above, uses a Teensy microcontroller board. Two analog sticks take input from the operator and transmit commands using an inexpensive RF pair. The wheel movement is facilitated by three servo motors which may seem like an odd choice. But we think that it simplifies the electronic side of the build because you do not need an H-bridge to control a servo motors. It’s a bit loud, as you can hear in the video after the break, but it certainly works quite well.

One of the commenters on the thread above asks why [Markus] didn’t use mechanum wheels. These would have allowed him to use just one wheel on each axis but the omni-wheels were so inexpensive that he went this route instead.

[Read more...]

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