PolyBot G1v4 with 5 modules in a four-legged lizard configuration.

This version was made to be a testbed for adding sensors and for testing the functionality of various configurations. Although it is not self-reconfigurable, it is very easy to manually reconfigure. Additionally, a simple cable is attached between modules to create a power and communications bus as both computation and power is onboard but shared among modules.

PolyBot G1v4 Design

Each module uses a standard hobby servo. from FMA direct (a coreless version) which have an output torque of 150 oz-in. The body of the servo is used as the main structure for the module as well.

There are four identical connection plates on every module along with four seperate electrical (power and communications) ports. As in the other versions of PolyBot, the modules may be attached at 90 degree rotated intervals. Connecting two modules is easy, with a simple push and a twist to lock the modules together.

Another feature of the easy to attach connection plates is that arbitrary "passive" pieces may also use the same interface. In many of the demonstrations we use plastic parts in various shapes as feet or hooks or whatever may be needed, all easily attached or replaced.

Power (~6V) is supplied on board with NiMH batteries. Our initial tests with COTS AAA batteries using the loop or rolling track gait, a system with 10 modules was able to achieve approximately 0.5 kilometers on one charge, running for about 45 minutes. This should be easy to improve upon.

Computation is also onboard. A Microchip Technologies PIC (16F877) 8-bit microcontroller is used on every module. The modules are connected together through either an RS232 or an RS485 serial bus. The modules may run either fully autonomously or under supervisory control from a PC sending commands through a wired or wireless radio link.

We've experimented with a variety of sensors (besides tapping the angle sensor (potentiometer) on the servo) including force sensor (FSR's) and light position sensors (PSD's - lateral effect photo diodes).

G1v4 Demonstrations

• Tricycle Riding
• Conforming Loop
• Fence Climbing
• Stair Climbing
• Pole climbing
• Tree climbing
• Porous material climbing
• Navigation
• Loop Gait Battery Test
• Lizard Gait