Off-season training

[Tom Mosher]

Originally Posted by Dean Hystad

For light sensors? Use the "Raw Value" terminal. For a color sensor you are stuck with the intensity value which comes out of the "Detected Color" terminal when the sensor is in Light Sensor mode. Looking at "Raw Value", the numbers get smaller when the light is brighter.

Thanks Dean, I totally missed the Raw Value terminal on the Light sensor. Sadly, my NXT at home is too old to support the software required for the Color sensor.

[Dean Hystad]

Originally Posted by Tom Mosher

Thanks Dean, I totally missed the Raw Value terminal on the Light sensor. Sadly, my NXT at home is too old to support the software required for the Color sensor.

Not true. I was part of the pre-releast testing and my beta NXT is running the newest version of commercial NXT software with color sensor support.

[Tom Mosher]

Originally Posted by Dean Hystad

Not true. I was part of the pre-releast testing and my beta NXT is running the newest version of commercial NXT software with color sensor support.

Sorry, I should have been clearer that the issue is the Mindstorms software running on my computer, not the NXT brick. There's no free upgrade for the PC software I own.

[timdavid]

Originally Posted by Tom Mosher

Sorry, I should have been clearer that the issue is the Mindstorms software running on my computer, not the NXT brick. There's no free upgrade for the PC software I own.

True, LEGO does not provide the commercial version of the Mindstorms NXT 2.0 software separately. However, they do make it available for download at their site. Technically, they make the software available for people who have lost their disks. I'm really at a loss to explain why LEGO can't make physical upgrade or replacement disks available for a nominal fee. That's what they did for the 1.0 to 1.1 upgrade.

The version of the software sold by LEGO Education has some additional features, including datalogging capabilities and tutorials. I guess that's why they charge $79 for it.

[Tom Mosher]

The last 6-week period of the school year has begun, and here's what the "lego robots" after-school activity group is up to.

First, the group has a new coach (the fourth one since last September). Spring is track season, so the third coach (a PE teacher) has passed the leadership to a math teacher (who was the volleyball coach), since that is a winter activity.

The focus is on adding PID controllers (without the I portion) to the team's range of comfortable tools. The math is simple, but it's not obvious how the robot does math until it's been experienced.

The first instance is a distance-following robot, with the ultrasonic sensor pointed toward the front. The PD control loop uses the MOVE block's Power input to maintain a fixed distance from a robot ahead of it. The students tested it by setting the robot on the floor, and having it drive toward their foot. Some robots stopped promptly at the predicted distance, some didn't stop at all. So the team learned about the influence of loop gain, and why it's important.

When you line the robots up on the floor, nose-to-tail, and start the first one on a straight drive, the others all launch in sequence, automatically. The chain rapidly breaks down though, since the robots aren't being steered.

Now, replace the distance sensor with a light sensor, adjust the parameters, and the result is a PD-based line tracker that uses the MOVE block's steering input. The concept of the use of the math blocks is identical.

Once each portion is working, they'll extract the distance PD and line tracker PDs into MyBlocks, then drop them inside a single LOOP block, with a single MOVE block controlled in both power and steering.

So, by the end of six weeks, I expect to see a train of tribots driving around a loop track, managing their speed to avoid crashing into each other.

[timdavid]

Originally Posted by Tom Mosher

...
So, by the end of six weeks, I expect to see a train of tribots driving around a loop track, managing their speed to avoid crashing into each other.

That would be very fun to watch. Sounds like the kids are on their way to careers designing autonomous cars.

[Tom Mosher]

Originally Posted by timdavid

That would be very fun to watch. Sounds like the kids are on their way to careers designing autonomous cars.

When they get it working, it could be video-worthy. Who knows, maybe driving aids will appear in Senior Solutions.