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Three Palms in a Robot

by John Ochwat
02/23/2001

Palm Robot in Action

Click to view a QuickTime movie of the Palm robot in action.

See the Palm Robot in action -- 3.9MB fast start QuickTime movie.

Back in November, when the PalmIII PPRK Robot Kit was merely a blip on Slashdot, we decided it would be a fun pre-Christmas story to buy and build one. We'd talk about the build, how the thing worked, and a bit about the physics and software. It sounded like a good story at the time, and a fun one too.

We decided to order the bare-bones kit instead of the easier one. My editors wanted me to experience the "joy" of scientific discovery myself. I agreed, though I probably had too much coffee when we talked.

We waited a few weeks for Acroname -- the company that licensed the rights to sell the kits from Carnegie Mellon University where the kit was developed -- to wrangle all the parts. Finally the kit arrived, and in mid-December, I eagerly set to work. I had no idea what I was getting myself into.

Some pre-assembly required

The bare-bones model required some pre-assembly steps, which according to the documentation were "not extremely difficult but require some comfort and familiarity with soldering, small components, and tearing apart servos."

Contents of the kit.
The complete kit contents spread out on the floor. So tell me again, why did we want the bare-bones version? Photos by John Ochwat and Derrick Story

Did I have any of that? Of course not. I haven't soldered anything since junior high metal shop, I have no familiarity with small components, and servos makes me think of Mystery Science Theater 3000.

The soldering wasn't very difficult. But Step 3 read, "Using your Pontech controller as a guide, make sure to get the red wire on the '+' side of the controller when the socket is plugged in."

This wasn't at all clear. I had to take out the little red socket to figure out how it plugged into the controller, then worked backwards from there.

Assembling the kit.
Various pieces of the robot kit.

The next major step involved modifying the three servos so that they rotate continuously. To do that, I had to open up each servo, take apart the gears in it, replace the bushings with ball bearings, and then put it all back together again.

"Adjust the servo until it stops moving by turning the small brass pin that protrudes. This is the potentiometer that typically gives the servo feedback. Here, we disengage it physically from the servo gear and so the servo rotates continually, thinking it is never reaching the input position."

That's not that tricky; but what takes some dexterity is keeping that brass pin in the same position when you reassemble the darned things -- especially after your fingers get coated with ball bearing grease.

Also, getting the servo wheel off is hard. I ended up using a small pair of vice grips to hold the wheel when I took the screw off, because I couldn't keep the wheel from turning otherwise. And the ball bearings you put on are tight -- so tight -- I had to jam them on using brute force.

"Now, put the lid back on top of the servo," the instructions read. "This may be snug and require a bit of finesse [read: brute force] as the bearings seat tightly."

After finishing with the servos I had to glue the roller wheels together, which -- surprise! -- required 5-minute epoxy. After a short trip to the hardware store, I was back at it. I glued the wheels, then glued the base of the serial cable to the deck, the acrylic triangular slab that's the base for all the parts.

Then it was back to the soldering gun (my new favorite toy) to attach three wires from the serial cable to the DB-9 connector. The instructions were well-marked, and even though I mostly avoided the tech wing of my high school, I had little trouble.

The soldering and servo-rebuilding make up the pre-assembly steps, and now I'm ready for the "standard assembly."

Assembling the frame.
Servos mounted in the aluminum sides with infrared sensors between them.

Basically I needed to put all the parts together now, starting with bolting the little infrared sensors to the aluminum sides, then bolting the sides together to make a hexagon. This was a simple but clumsy process, since an individual nut and bolt assembly fit on about a third of my thumbnail. Once the hexagon was in place, I bolted the servos to the frame.

The little robot was starting to take shape, especially after I attached the controller and top deck of the robot. Then I went on to the wiring, which consisted of a lot of "plug-black-wire-into-jack-#2" and "plug-servo-connection-3-into-position-S3".

"Between the servo wires and the detector wires, your robot will look a bit like a teenager in the middle of an orthodontist appointment with wires hanging out in all directions," the directions read. They're not kidding.

Robots: Almost home

During the assembly process I talked to Steve Richards, the founder of Acroname, the company that licensed the rights to sell Palm robot kits from Carnegie Mellon.

I'm apparently not the only one building one of these. When I talked to him in late December, Acroname had been selling the kits for a little over a month -- and had finally been able to meet demand. He was selling one bare-bones kit to about every two easy kits.

"The Palm robot paralleled some of our development we were doing," Richards said, adding that Acroname had its own designs for several years, but "this is the first one that's been in the national media's attention."

"Robotics is at a strange point where people are asking what good is it," he said, likening it to "the way people were looking at computers, and what the Homebrew Computer Club was doing 20 years ago."

There are a lot of special-purpose robots around (and on the way), and we aren't reluctant to send robots to perform hazardous duty such as fighting fires or tooling around on the surface of Mars. However, robots haven't made it to the home in any measurable form, he said, in part because "We haven't seen the killer app come along."

View of robot from above.
Top view of the completed Palm robot.

View of the underside of the robot.
Bottom view of the robot.

There are robotic vacuum cleaner prototypes available, he notes, but for now they're priced out of widespread market acceptance. "What it's going to take for these things to be absorbed into our culture," he said, "is when the robot can do three important household tasks, like vacuum, shovel the walkway, and take out garbage."

The Palm-powered robot does none of these things, but for the moment that's not important. Though this kit is "a novelty device inside the house," it opens up a lot of opportunity for educational and research projects to further what can be done -- both with Palm devices, and with robots.

The final stages of the build were an anticlimax. I screwed the wheels on, and then mashed all the wires into a manageable lump so I could bind them in place with the two cable ties (one of mankind's greatest inventions).

Voila! I'm done. Or so I thought.

Next page: It's a sofware problem.

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