PolyBot G1 with 16 modules in a four-legged spider configuration.

The first generation of PolyBot has the basic ideas shared in all the generations of repeated modules being about 5 cm on a side. The modules are built up from simple hobby RC servos, power and computation are supplied offboard. The modules are manually screwed together, so they do not self-reconfigure. The G1 modules showed the first instance of simple reconfiguration for locomotion in 1997.

PolyBot G1 Design

There are two structural parts to each module, represented as blue and green in the figure. These parts are made from laser cut plastic sheet. We have tried various plastics (acrylic and ABS) and settled on delrin for the g1v3 version. The modules are screwed to their neighbors with bolts in the four corners. Each face is square so that modules can be attached at 90 degree increments allowing motion all in-plane or out of plane if desired.

The two parts are rotated relative to each other by a standard hobby servo. We use servos from FMA direct (S355M) which have an output torque of 114 oz-in and fit well in the form factor.

Power (6V) and control signals are provided offboard in this version. The current required can be up to 500mA per module. We have used a 68HC11 microcontroller to generate the PWM servo control signals and interpret a higher level joint angle commands sent to it from a PC by RS232. A later solution was to use the miniSSC, a serial servo controller. Note, that external control and power makes cabling and a wire harness a painful necessity.

The design is fairly straight forward to construct from off the shelf parts and laser cutting is available from many plastics shops. The design has been made available to other researchers, please contact yim@parc.com for more info.

G1 Demonstrations

• First Loop-to-Snake Reconfiguration (1997)
• Distributed Manipulation (1997)
• Locomotion in tubes(1997)
• 4-legged spider-like(1998)
• snake-like turning(1998)