Tricycle robot using omni-wheels

[Markus Gritsch] built this six-wheeled robot usingĀ 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.

10 thoughts on “Tricycle robot using omni-wheels

  1. I would lay odds he didn’t ‘dip’ the wheels (He doesn’t say how it is applied). I have tried dipping and it doesn’t give acceptable results for rubberizing wheels. Plastidip has a spray on version of their coating which works quite well.

  2. I’m not sure how he could have used mechanum wheels for this platform, since they are used in pairs to generate movement parallel to the wheel’s axis. I guess it could be done with some careful programming, but mechanums are (afaik) used in pairs.

    Those are also single wheels even though they have two layers. The rollers are just offset. I’ve used Kornylak Transwheels (http://www.kornylak.com/wheels/transwheel.html) for my triwheel robot.

  3. @Brian.Holiday: Yes, I used the spray (http://www.conrad.at/ce/de/product/888183/PLASTI-DIP-SPRAY-311G-SCHWARZ/SHOP_AREA_19752&promotionareaSearchDetail=005)

    @eddt: Yes, modifying servos for continuous rotation is not hard. Just make sure the potentiometer is mechanically not connected to the rotating wheel anymore.

    @Soo-Hyun: Although you need pairs of wheels, they are sold in single quantities (http://at.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0408536). I glued them sogether using superglue :)

  4. Mecanum wheels require a minimum of four wheels to move omnidirectionally. Their advantage being that they can be mounted in existing chassis with normal wheel placement, where omni-wheels need a triangular arrangement for full holonomic movement.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s