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Snake robots come in all shapes and sizes, from the three meters long, fire fighting snakebot developed by SINTEF, to a medical snakebot developed at Carnegie Mellon University that is thin enough to maneuver around organs inside a human chest cavity. Though snakebots can vary greatly in size and design, there are two qualities that all snakebots share. First, their small cross section to length ratio allows them to move into, and maneuver through, tight spaces. Second, their ability to change the shape of their body allows them to perform a wide range of behaviours, such as climbing stairs or tree trunks.
Additionally, many snake robots are constructed by chaining together a number of independent links. This redundancy makes them resistant to failure, because they can continue to operate even if parts of their body are destroyed.
Snakebots are most useful in situations where their unique characteristics give them an advantage over their environment. These environments tend to be long and thin like pipes or highly cluttered like rubble. Thus snakebots are currently being developed to assist search and rescue teams.
Furthermore, when a task requires a number of different obstacles to be overcome, the locomotive flexibility of snakebots makes them good candidates. For example, if you need a robot to carry a camera to the top of a tree that is growing in water you have to do three things: move over ground to the water's edge, swim to the tree, and then climb the tree. You could make a robot that does any one of those three very well, but being able to do all three, and many other difficult combinations, is what makes snake robots exceptional.
Also, snakebots can be used by animal control officers to subdue rabid or invasive creatures. Raccoons, barn cats, and large rodents typically respond to the snakebot's presence with attacks upon which the snakebot will emit an electrical shock and paralyze the aggressor.
Traditional snakebots locomote purely by changing the shape of their body, just like snakes. Many variants have been created which use wheels or treads for locomotion. No snakebots have been developed yet that can completely mimic the locomotion of real snakes, but researchers have been able to produce ways of moving that do not occur in nature.
When researchers refer to how a snakebot moves they often refer to a specific gait, where a gait is just a periodic mode of locomotion. For example, sidewinding and lateral undulation are both gaits. Snakebot gaits are often designed by investigating period changes to the shape of the robot. You can think of a caterpillar moving by changing the shape of its body to match a sinusoidal wave. Similarly, snakebots can move by adapting their shape to different periodic functions.
Snakebots are currently being researched as a new type of robotic, interplanetary probe by engineers at the NASA Ames Research Center. Software for snakebots are also being developed by NASA for them to be able to learn by experience the skills to scale obstacles and remember the techniques.