Servo - April 2009

Twin Tweaks ...

would work perfectly on a number of levels for the educational bots.

Due to the tragic and unforeseen injury suffered by our grasshopper, the ladybug was left to roam the tracks alone. A true test of the bug’s line-following ability would demand a proper race, and a proper race would demand a proper rival. Our dad’s Mark III OOPIC robot was eager for a challenge,

and perhaps a bit overconfident due to the advantage it possessed in the form of wheels.

The small oval and the mix and match track were a bit on the small side for a race between the ladybug and the Mark III, so we turned to a larger line-following track. The LEGO Mindstorms starter kit comes with an excellent large scale line-following track, and it would be a perfect proving ground for our bug. We allowed it the luxury of a couple of test laps, and we were very pleased with what we saw.

The walking robot navigates corners surprisingly well, and even when it seems to be veering off course it always corrects itself. If the bug does happen to stray from the course, it has an automatic shutoff feature to keep it from wandering off into oblivion. Hopefully, it wouldn’t take advantage of that feature during

FIGURE 12. MIX AND MATCH TRACKS.

line-following mode, the bug pauses to allow a proper positioning at the starting line before sounding a charming charge jingle and setting off.

The Ollo Bug kit comes with two line-following tracks of its own. One is a simple oval on the back of the quick start pamphlet, and the other is made out of cardboard squares that can be cut up, mixed, and matched. The small oval is a nice testing ground, and the mix and match track is tons of fun.

One caveat about the mix and match track is that the cardboard squares tend to get pushed around by the scurrying legs of the bugs. Setting up the track on a high friction surface mitigates this problem, and we think something between carpeting and tile would be ideal. Come to think of it, the short, dense carpet that covers the floors of many school classrooms

the showdown with the Mark III.

Speaking of the Mark III, things were not as they should have been with regards to the programming. The Mark III is equipped with three phototransistors for line-following (the same exact type that we used on our safe-cracking robot, incidentally), and it did at one time have a killer line-following program on it. But now, in a twist of sabotage that would feel right at home in another Francis novel, the Mark III was experiencing some serious issues downloading programs. The only logical culprit that we could identify was the serial cable that connected the robot to the programming computer, but the problem was not resolved in time for race day.

With the Mark III lacking a program, the Ollo ladybug ran circles around it in an unexpected upset, enough to arouse the suspicion of any amateur detective. The Ollo Bug was triumphant, but the serial cable debacle left us a bit unsatisfied.

Flying Finish

FIGURE13. HEADINGFORTHEHOMESTRETCH.

FIGURE 14. MAKING DICK FRANCIS PROUD.

The Ollo Bug line-following program is quite effective, but intrepid tinkerers that think they can do better have the opportunity to find out. The kits that we were given did not have the necessary components to allow the bugs to be programmed, but

Robotis does make a downloader module to allow for custom programming.

The greatest thing about the Ollo downloader is that it takes the form of a simple USB plug-in that uses infrared communication to connect with the Ollo Bug. We are positively ecstatic that a robotics kit has finally seen the light and chosen a USB connection over the tragically outdated and anachronistic serial connection that seems inexplicably preferred in almost all of the other robot kits that have meandered through our column.