question on mindstorm capabilities for competition

[George Nychis]

Hi all,

Every year on our campus we have a robotics competition called the Mobot
race, where home built robots attempt to steer through a course by
following a painted white line. This white line curves and breaks at
some points depending on the sidewalk condition.

I wanted to enter the race with a 10 year old to give him some
experience with robotics, he would love it to death. He is great with
legos but neither of us have mindstorm experience.

I am under the impression that a light sensor is all we might need for
this.  Using the light sensor we could detect the edge of the white line
and attempt to follow it.  When there are cracks, we could just program
it to keep its wheels straight and keep going.

Is the RCX or NXT best for this?  And what kind of programming might be
involved?  I have a lot of programming experience such that I could do
it all for the kid, but it's best if it provides something he can play
with too.

I found this, which gives me the impression that there is some base
programming kit that might allow us to program something simple like
following the line:
http://www.stanford.edu/class/cs229/proj2006/Townsend-MachineLearningWithALegoMindstormsRobot.pdf 


Thanks!
George

[Steve Hassenplug]

George,

I think the NXT would be an excellent way to get your son involved in
robotics.  And, it should do just fine in that competition.  That's
pretty much what it was designed for.

Don't worry about a lack of experience with Mindstorms.  I'm sure your
son will be able to help you.  :)

Or, you can post here...

Steve

On Thu, Jun 26, 2008 at 1:45 PM, George Nychis <gnychis@...> wrote:

>
> Hi all,
>
> Every year on our campus we have a robotics competition called the Mobot race, where home built robots attempt to steer through a course by following a painted white line. This white line curves and breaks at some points depending on the sidewalk condition.
>
> I wanted to enter the race with a 10 year old to give him some experience with robotics, he would love it to death. He is great with legos but neither of us have mindstorm experience.
>
> I am under the impression that a light sensor is all we might need for this.  Using the light sensor we could detect the edge of the white line and attempt to follow it.  When there are cracks, we could just program it to keep its wheels straight and keep going.
>
> Is the RCX or NXT best for this?  And what kind of programming might be involved?  I have a lot of programming experience such that I could do it all for the kid, but it's best if it provides something he can play with too.
>
> I found this, which gives me the impression that there is some base programming kit that might allow us to program something simple like following the line: http://www.stanford.edu/class/cs229/proj2006/Townsend-MachineLearningWithALegoMindstormsRobot.pdf
>
> Thanks!
> George

[Parax]

In lugnet.robotics, George Nychis wrote:
> Hi all,
>
> I am under the impression that a light sensor is all we might need for
> this.  Using the light sensor we could detect the edge of the white line
> and attempt to follow it.  When there are cracks, we could just program
> it to keep its wheels straight and keep going.
>
> Thanks!
> George


Hi George,
NXT will do this fine, however you might want to try two light sensors (1 more
than in the Retail Kit) Otherwise you might not be able to tell going off line
and a break in the line!

The NXTG language would be fine for this task and im sure your ten year old will
be showing you how it works within 20 minutes... your programming skills would
not help with NXTG (your logic would though!) but there are many freely
available languages you can get hold of for more standard programming languages.

Mike

[George Nychis]

Hi all,

Just wanted to follow up on this!

It turns out that Tim (the 10y/o) has a next door neighbor with a
complete RCX mindstorm kit with tons of extras from being in a lego
robotics club in the past.  The neighbor was nice enough to give us all
of the legos!  We were super excited.

We have 3 light sensors, 4 motor sensors, and 4 touch sensors.  So I
think we're set on sensors.

 > NXT will do this fine, however you might want to try two light
sensors (1 more
 > than in the Retail Kit) Otherwise you might not be able to tell going
off line
 > and a break in the line!

I kind of want to discuss the 1 light sensor vs 2 light sensors now :)
I originally wanted to stick with 1 for simplicity, but you're right,
i'm not sure how it would be able to tell a break from going off the
line.  How would you use the 2 exactly?  One stays further ahead of the
robot?

Also, the kit came with an RCX 1.0 and a infrared tower with a serial
connection. Is it possible we can swap out the serial infrared with a
USB infrared and it still work OK?  I don't know if there was anything
specific built in for the RCX 1.0.  If so, I'm going to try and snag one
on ebay since most of our machines are USB and have no serial.

Thanks!
George

[Steve Hassenplug]

On Wed, Jul 9, 2008 at 11:11 AM, George Nychis <gnychis@...> wrote:
> It turns out that Tim (the 10y/o) has a next door neighbor with a complete RCX mindstorm kit with tons of extras from being in a lego robotics club in the past.  The neighbor was nice enough to give us all of the legos!  We were super excited.
>

Lucky you.  :)  Sounds like you have everything you need.

> I kind of want to discuss the 1 light sensor vs 2 light sensors now :) I originally wanted to stick with 1 for simplicity, but you're right, i'm not sure how it would be able to tell a break from going off the line.  How would you use the 2 exactly?  One stays further ahead of the robot?
>

With 2 light sensors, two possible (there are other) strategies are
(1) Try to keep both sensors on the line.  When one goes off, turn
towards the one still on the line.  If both go off at the same time,
you may have reached the end of the line (go straight?)
(2) Try to keep the line between the two sensors.  If either sensor
sees the line, turn away until it doesn't see the line, and continue.
This approach has the slight disadvantage that you never really know
if the line is still between the sensors

With three sensors, there are also several options, like:
(1) Mount three sensors very close, and try to keep the line under the
middle sensor.  As the robot drifts, you can correct different amounts
based on which sensors are on the line
(2) Keep two outside sensors OFF the line, and use the third to
determine if the line is still between them.  If not, do something to
search for the line.

Make sense?

> Also, the kit came with an RCX 1.0 and a infrared tower with a serial connection. Is it possible we can swap out the serial infrared with a USB infrared and it still work OK?  I don't know if there was anything specific built in for the RCX 1.0.  If so, I'm going to try and snag one on ebay since most of our machines are USB and have no serial.
>

You can use either the serial or USB tower with your RCX, without any problem.

Steve