2 Wheel Robot

kenwtn

··· New to Robotics and I was thinking about building a 2 wheel robot. But since I have not done anything like that in the past I thought I would ask. Is it enough to just have a large low center of gravity to balance a robot with only two wheels? Has anyone done anything along those lines?

Bruce Bates

kenwtn -

No, it takes a good deal more than just a low center of gravity. You must be able to detect and respond to situations where the mobile platform is tipping too far forward, or too far backwards. This can occur even during times of acceleration, de-accelleration and/or braking. It also can obviously occur going up or down hill. Two wheeled pllatforms are really quite advanced by comparison to other 3-4 or more wheeled designs.

Regards,

Bruce Bates

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kenwtn

All of what you have said makes sense, I was hoping the low center of gravity would be enough to overcome those issues. I thank you for replying and I will now re-evaluate my decision to attempt this project.

Tronic (Greece)

If you own a boe-bot, you can try my design posted below:

http://forums.parallax.com/showthread.php?p=570699


It uses standard boe-bot parts, except the floppy disk case I used for the body and the simple 4-button RC control to navigate it around.

You might want to try this before attempting more advanced setup...

Regards, Thanos


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Greekbotics: Greek Robotics Forum

kenwtn

Thanos,
That is what I had in mind only on a much larger scale. The only thing I have to lose is time so I think I will give it a try. If you have any other advice for me please contact me vai my email address. I would be most thankful for any advice you can offer.

Ken

Tronic (Greece)

My intention is to build a larger one too, maybe large enouph to carry me around (like segway does) but if you don't start with small scale models to test the principles of its operation and tweak it along, you might end-up leaving unfinished or stuck...

Its a long step to switch from theory to operation. When I joined parallax forums, one and a half years now, I was totally newbe in electronics and microcontrollers and decided to start with simple robots like the crawler my avatar shows.

I've had seen a 2 wheels robot design that was presented by a parallax customer but it was impossible to build it cause of my lack o knowledge in programming that time. http://www.parallax.com/html_pages/resources/custapps/app_bway.asp

Now I learned ways to make it·from the simplest parts and most efficient code around. But its after years of expierence in making other type of robots and minor electronic projects that allowed this design to come easy as that. And there is more yet to be learned before I'm able to make in work in larger scale model!

Thanos



PS. kenwtn,·you don't mention anywhere your e-mail address...

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Greekbotics: Greek Robotics Forum

Post Edited (Tronic (Greece)) : 3/4/2006 1:11:08 PM GMT

kenwtn

Since I seem to have nothing but time on my hands right now. Starting small and scaling up is not a problem either.

jsmasterking

I built a self balancing robot that does not need software balancing. The center of gravity can also be above the wheel's axis. I have plans for it and all you need is some like cardboard and 2 parallax continuous rotation servos and an controller. Oh also the battery pack, which helps with balancing.

You also need large wheels: http://forums.parallax.com/showthread.php?p=572161·I am trying to use CDs glued together but you can use parallax wheels if you want to put like a safety arm that bounces the bot back if it is about to tip over. I did and it works and look fine. I just want the large wheels to see if it could work without the safety arms.·Safety arms touch the ground only when the servos are quickly accelerated. You can use ramping to get rid of this problem.

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·on····· plane··········································, when catching ducks

"In this house, we obey the laws of thermodynamics!"
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http://profiles.yahoo.com/jsmasterking

Post Edited (jsmasterking) : 6/5/2006 10:54:24 PM GMT

kenwtn

Would like to see the plans or the robot. The above link only brings up a blank page when clicked.

jsmasterking

I am still here. I have plans on my other computer but my mother is calling me for breakfest. Do you have scotch tape. You'll need it. Go here: http://www.smallrobot.com/why.html Its how the drive mech works. I will post my plans later in the day!

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·on····· plane··········································, when catching ducks

"In this house, we obey the laws of thermodynamics!"
··············································································^
http://profiles.yahoo.com/jsmasterking

Post Edited (jsmasterking) : 6/5/2006 10:54:49 PM GMT

jsmasterking

I am having trouble uploading my plans. I hope this works.

Well the images are of the front and the back. On the first image, bend the top flap back and the bottom two flaps back also. On the second image bend the bottom flap and stick the two things together (I used scotch tape and foam-core boards). The two large flaps and the body will make a rectangular box. Put two pieces of cardboard or foam perpendicular to each other making and X to keep the box from collapsing. Print the picture so that the servos will fit in the holes. Insert the servos from the top and slide into toward the bottom. Mount the batteriepack on the bottom and the controller on the top. For the safety arm, I used a small pocket fact book. You can use nuts and bolts to secure everything but take extra care when making holes for them. Remember rubber bands are a little armature but sometime armature is the way to go.

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·on····· plane··········································, when catching ducks

"In this house, we obey the laws of thermodynamics!"
··············································································^
http://profiles.yahoo.com/jsmasterking

Post Edited (jsmasterking) : 6/5/2006 10:53:41 PM GMT