Servo - January 2007

Mighty Morphing Bioloid

for an educational robot, because it allows the Bioloid to achieve true autonomy and interact with its environment.

The comprehensive kit includes designs for four impressive robots with up to 18 joints. The four advanced designs are a puppy, a tyrannosaurus rex, the ultra-cool sounding King Spider and, of course, the iconic humanoid.

Apart from all of the obviously cool stuff in the kit, there are some final touches that we really appreciated. Probably the biggest pleasant surprise was that the Bioloid came with batteries included, a phrase practically unheard of nowadays. And if that wasn’t cool enough, the batteries are rechargeable, and the kit comes with a charger. We had been working with the kit for a while before we realized that the charger was made for AC outlets, but adapters are pretty easy to find.

Commanding the Bioloid

The programming environment for the Bioloid is an interesting beast, and, like the kit itself, comes in multiple forms. The main program editor for the Bioloid looks like a Frankensteined version of Easy C and Visual Basic, with literal blocks of code that encompass familiar commands like if, else, and for loops. Sometimes the written commands inside the blocks are accompanied by curious pictures perhaps meant to appeal to the more visual programmer, but often times we found our selves scratching our heads and wishing for a Rosetta stone of programming.

The other programming environment is the Motion Editor, something akin to what most other servo based robots have. Individual servo motors are assigned values to move to certain positions. The cool thing is that a series of commands in the motion editor can be saved in a block and implemented in the behavior control editor. Synergy is a beautiful thing.

Robots in Disguise ... As Other Robots

We decided that an effective way to gauge the Bioloid’s effectiveness as an educational tool would be to follow the natural curriculum of the kit. With that in mind, we set out to build the simplest model — a crossing gate. While this might seem like an underwhelming project to build first out of such a cool kit, we appreciate the fact that Robotis has provided a simple way for novice tinkerers to get their feet wet. A cursory glance at the kit reveals some pretty intimidating stuff — tons of tiny fasteners, intricate frame pieces, lots of cables of various lengths, and a whole mess of Dynamixel servo modules. With such a daunting kit on hand, a painfully simple design doesn’t look so painful after all.

The crossing gate did indeed use very few parts, but it still provided an adequate introduction to the kit and its unique attributes. One such attribute is a component of the Bioloid’s design,

presumably intended to make construction easier: on every servo module and the CM- 5, there are pockets that capture the nuts. This sounds like a nice way to free up some hands when building the robot, and it often is. Sometimes, though, we think the Bioloid kit falls victim to a stack up of tolerances. When you’re dealing with mass produced plastic parts that are already a tight fit, small imperfections can stymie even the most tenacious of efforts. Unfortunately, it seems like to us that this might sometimes be the case with the Bioloid. It could just be us, but it seems like on some of the modules that we could only ever get three of the requisite four nuts captured in the pockets. Even so, the crossing gate came together without

much difficulty. Most of the beginner designs can be built in a matter of minutes, even for novice roboticists.

Next we tried our hand at an intermediate level robot — the spider. We found out that dealing with the pockets becomes somewhat easier with practice. A thin screwdriver is a handy way to provide some extra leverage on the nuts, as long as you’re careful not to screw up the threads. Intermediate level bots take a bit longer to build — more like a few hours instead of tens of minutes. But once that spider was finished, it was really exciting to see that a ho-hum crossing gate could morph into something so cool.

After graduating from the intermediate level designs, we felt confident enough to tackle an advanced design. The puppy seemed like a good choice, because it would be interesting to see how this modular robot dog compared to other robots that were designed solely with imitating man’s best friend in mind. The advanced designs take many hours to complete, so it might be a good idea for roboticists that cannot devote their undivided attention to the Bioloid to find a good stopping point in the middle. Fortunately, that’s pretty easy to do with the Bioloid puppy — the limbs are built first, and then everything is connected to the body. The synthesis of the limbs into a complete bundle of puppy joy is by far the most difficult step, but the end result is wonderfully entertaining. All it takes after construction is a quick download of a sample program from the CD, and the puppy is ready to bring smiles to the faces of young and old roboticists alike. The robotic puppy can scamper along at a brisk pace, perhaps not with the agility of other