Jul 12, 2008

Robot Inspiration Series #3: Self-Balancing Wheeled Robots - Part I

Did you ever consider building a robot that can balance and move around on two wheels? They have a lot of appeal over other kinds of locomotion, some of which include:
- they are faster and can carry higher payloads than bipeds,
- they are more agile (for getting around tight spaces) than robots that require more than two wheels, and
- are usually quite simple/fast to build using a LEGO NXT MINDSTORMS kit.

But they are not without disadvantages: They need to use at least one sensor port and need a motion control algorithm for balancing.

The following are a few examples as inspiration for building your own self-balancing robot.

Hitachi’s EMIEW robot:

Toyota’s MOBIRO robot:

The Segway (of course):

These all balance in one axis. If you are looking for more of a challenge, you can refer to Carnegie Mellon's Ballbot, which balances in two axes:

In Part II, I will post a tutorial to show you how easy it is to make your own self-balancing robot.

If you want a head start, here are some MINDSTORMS' examples of self-balancing robots:

Steve Hassenplug’s Legway

http://thenxtstep.blogspot.com/2006/05/we-all-knew-it-was-just-matter-of-time.html

http://thenxtstep.blogspot.com/2007/03/gyro-working.html

http://thenxtstep.blogspot.com/2007/04/gyro-sensor.html

http://thenxtstep.blogspot.com/2007/08/self-balancing-robot.html

http://thenxtstep.blogspot.com/2008/02/nxt-standalone-another-self-balancing.html

4 comments:

Andy said...

What about a robot that balances in all 3 axes? :P
Great post! Can't wait for the rest ^^

David Levy said...

Great article. I have not had a chance to read through all of the links but I did recently come across some related links which you may have already mentioned:

1) Here is a recent forum posting that demonstrates how do do this with just a light sensor.

2) Here is a NXTLog Entry that compares another Light Sensor Segway with a gyro sensor version.

BlueToothKiwi said...

Brilliant post, Kirk!

Making robust balancing algorithm is a subject very close to my heart - as I am planning a second attempt at designing my quadcopter using a Gyro (my last attempt failed).

Of course you can cheat:

(1) For Segway type vehciles, Make the diameter of the wheel so big that it behaves more like the Hailfire Droid tank wheel. The secret here is to lower the centre of the gravity of what is in between the large wheels - so all the weight is below the wheel axle. Check out my NXT Hailfire post last month

(2) For bike type vehicles, Make the wheels really thick. The secret here is to make the contact surface wider so it no longer behaves like a bike - but more like the Bat pod from the new Batman movie. Check out Linear Actuator's post on the NXT version of the Bat pod.

Kirk Backstrom said...

Thanks Andy, David, and Bluetoothkiwi!

I chose this topic because there are a lot of types of robots that can be made with this technology that hasn't been done yet with the NXT - so far I have only seen such robots that only balance or move (front/back and turn) - so much more can be done.

Kirk

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