FIGURE A


The PalmPilot Robot Kit is at home on a table or desk. Roll over picture for a larger image.

The Palm computer makes a handy robot controller: it packs a great deal of computational power in a small form factor, runs on batteries, and communicates with external devices through a serial port (or USB in later models). Best of all, a Palm device's display provides an excellent graphical user interface. In robotics, debugging is even more of a challenge than with ordinary computer programming. The ability of a robot to show you such information as its sensor values and its current state is crucial, and that's why the Palm device screen is truly valuable.

Our robot empowers a Palm unit to move about on any flat surface and sense its environment. The configuration of three omni-wheels, pictured in Figure B, is the key to robot's motion.

FIGURE B


The PPRK wheels can slide in any direction. Roll over picture for a larger image.

The wheel design allows the robot to move in any direction, turn in place, or do both at once. Thus, the robot moves fluidly, spinning and gliding to align itself with flat surfaces like a nearby wall at some desired distance.

The kit also has three infrared optical range sensors, each positioned between a pair of wheels. These sensors, shown in Figure C, measure straight-line distance from the robot out to the closest obstacle in each direction and provide reliable range readings between 10 centimeters and 1 meter away.

FIGURE C


These sensors measures distance using an infrared beam and triangulation. Roll over picture for a larger image.

Surprisingly, even though these sensors use infrared light, they continue to work reasonably well even in a sunlit room.

Building the PPRK
On our Web page, at http://www.cs.cmu.edu/~pprk/, we've documented complete instructions for building the PPRK as well as open source software for controlling its motion. A parts page identifies sources for all eleven parts required to build the PPRK. Step-by-step instructions and photographs document the process of putting it all together, from gluing the wheels and servo discs together to mounting the wheels, sensors, and Palm device cable on the acrylic chassis. The most challenging part of assembly, by far, is a soldering step. You need to attach the relevant lines from a Palm HotSync cable to the serial port of the SV203 microprocessor. Happily, there is an alternative. Acroname, Inc. (at http://www.acroname.com) has licensed our PPRK and is selling a fast-build kit that comes partially assembled. You can find it at http://www.acroname.com/robotics/info/PPRK/PPRK.html. With their kit, you can finish the fast-build PPRK, pictured in Figure D, in about one hour using just a screwdriver.