STriDER (Self-excited Tripedal Dynamic Experimental Robot) is under development at Virginia Tech University. This cunning robot has a totally unique gait. One researcher described it as being like "a biped with a walking stick."
The STriDER tripedal robot is able to change direction by selecting which of its legs to swing through. I could write a long complicated paragraph describing how it walks, and still fail. A good youtube video is worth a thousand words.
One of the researchers delivered himself of these details:
[It] “is a novel three-legged walking machine that exploits the concept of actuated passive dynamic locomotion to dynamically walk with high energy efficiency and minimal control. Unlike other passive dynamic walking machines, this unique tripedal locomotion robot is inherently stable with its tripod stance and can change directions while walking. The simple tripod configuration makes it lightweight, enabling it to be launched to difficult to access areas, and its height makes it ideal for deploying and positioning sensors at high position for surveillance, for example.”
As soon as I read about the STriDER three-legged robot, I thought immediately of the "spiders" - three-legged bots that roamed the vast interior of the alien craft in Rendezvous With Rama, the classic 1972 novel by Arthur C. Clarke.
Ten metres away was a slender-legged tripod surmounted by a spherical body no larger than a football. Set around the body were three large, expressionless eyes, apparently giving 360 degrees of vision, and trailing beneath it were three whiplike tendrils. The creature was not quite as tall as a man, and looked far too fragile to be dangerous, but that did not excuse their carelessness in letting it sneak up on them unawares. It reminded Norton of nothing so much as a three-legged spider, or daddy-long-legs, and he wondered how it had solved the problem - never challenged by any creature on Earth - of tripedal locomotion.
(Read more about Clarke's spider tripod robot)