Directional adhesion
Video & pictures
About  Sangbae....

iSprawl  (Independent Sprawl robot)

iSprawl is the youngest and fastest sibling of Autonomous version of Sprawl robot family.  I joined BDML at the end of this Office of Naval Research project and designed iSprawl for the first creation at Stanford.
Sprawl robots are designed by inspiration based on study of cockroaches.   - Watch iSprawl's running on ground. Other movie clips are on video page

Whereas other sprawl robots utilize pneumatic system, iSprawl is equipped with battery and electric motor and  power transmission system that convert rotary motion to reciprocal leg thrust.  What most makes iSprawl unique is push-pull cable transmission system.  Since Sprawl family turn its orientation by rotation of their leg with respect to hip joint, power transmission path is not fixed. Which is frequent problem in legged robot with centered engine.


Usage of steel cable as pulling transmission
is very common as you can find very easily in bicycle brake and car throttle. iSprawl's cables, however, thrust and pull the legs in high speed (up to 17Hz) without significant energy loss. This enables iSprawl's light and fast movement of legs leading to fast locomotion up to 15 body-lengths/sec(2.3m/s)
Click to see video of slow motion



Critical function prototype of push-pull cable system.

I tested push-pull cable system with styrofoam body without legs. This prototype runs surprisingly well.  

 Click to see serial spring in the path of cable.

see BDML iSprawl twiki page to learn more about iSprawl.



Aqua Sprawl (April 2003)

Predecessor of iSprawl, the first sprawl robot that operates with autonomous power. It uses hydraulic power transmission system. The idea was to explore hydaulic power transmission to distribute power to the legs. The tubes contain water and the system works like hydraulic brakes on a car, with a single master piston and slave pistons at each leg. Aqua Sprawl is assembled in a bathtub to prevent air bubbles.

 After many design iterations, including remachining the original Sprawlita pistons to put in double seals to handle negative pressure on the return stroke, a version of Aqua Sprawl was produced that ran fairly well:
A movie of Aqua-Sprawl

Although Aqua Sprawl ran reasonably well, there is a fundamental limitation to the achievable speed because while retracting the pistons, only atmospheric pressure is available. On the other hand, this could be a good design for underwater use!