There are nearly 8,000 species of reptiles on the planet, and most of them crawl, walk, slither, and undulate through the water in unique ways. Because reptiles are cold-blooded creatures, often their movements are designed to help them move quickly and efficiently.
Snakes, in particular, seem to have unique movements that can get them in and out of places quickly and effortlessly, and one professor has found a way to replicate many of those movements mechanically. Howie Choset, a professor at Carnegie Mellon University, has worked for years to develop snake-like robots that he hopes will be able to help people out in numerous ways, from inspecting the undercarriage of bridges to slithering through the rubble of collapsed buildings looking for trapped survivors.
"Right now, the way to get to these trapped survivors is to pull the rubble out one rock at a time," Choset says. "So our dream is to have the snake robot thread through this collapsed rubble and get to the victims more quickly." Similar robots are being developed at other universities, but according to Dan Kara, owner of Robotics Trends, none of the other prototypes can climb pipes, as Choset’s snakebots can do.
The Carnegie Mellon robots move using basic cyclic movements called "gaits," which can be programmed by a computer and drive the snake indefinitely. Combining the basic gaits with other types of controls can result in the development of "behaviors," where the snake robots can perform higher-level tasks such as climbing stairs and poles. Some of the basic gaits include:
Linear progression, where sine waves are sent through the entire length of the snake robot, propelling it forward or backward. This gait is perfect for having the robot fit into tight areas, such as inside pipes or through links in a fence.
Strafing is a movement taken from snakes such as sidewinders, which move sideways. This gait is currently one of the fastest ways for the snakebots to move, and is the best fit for rugged terrain. One vertical and one horizontal sine wave interact, moving the front half of the snake to the right and the back half of the snake to the left, having the effect of spinning the snake robot in place.
Corkscrewing causes the snake to move in a spiral motion, which is useful for propelling the robot forward or backward through obstacles in its path, where linear progression would be difficult. Corkscrewing is also useful for maneuvering the robot through a chain link fence or a small hole in a wall or floor.
Rolling is the most energy efficient gait, because the robot curves into a half-moon shape and then rolls sideways, using its momentum to move quickly. This gait is particularly useful for climbing hills and traveling over uneven terrain.
Pipe/Tube/Pole Climbing allows the snakebot to climb up the inside or outside of pipes or tubes. The robots can climb through pipes as small as they will fit into, or up the outside of poles whose perimeters are less than the length of the robot.
Cornering is a motion that allows the snake robot to maneuver around tight corners, such as the corners inside building structures, plumbing systems, or construction undercarriages. The body of the robot bends to match the corner as it encounters it, and the bend is maintained as the snake moves forward. Once the robot clears the corner, the bend is removed.
Gaits such as these, combined with other movements, make the snake robots extremely efficient in helping with numerous tasks in the field. The machines can be fitted with cameras and electronic sensors, and controlled with a joystick. If they are housed in a waterproof skin, the robots are even able to move across the top of water, simulating swimming. The robots are built from lightweight aluminum or plastic, and are about the size of a human arm or smaller.
According to Sam Stover, a search team manager with the Federal Emergency Management Agency, snake robots such as the ones Carnegie Mellon is designing would greatly enhance search and rescue efforts because they would offer greater mobility than the equipment currently being used, such as cameras attached to extendable poles. Sniffer dogs have the one quality that robots can’t replicate, Stover says, but dogs can be used only when rescuers have access to the areas where survivors may be trapped.
The Carnegie Mellon robots may not be ready for use for another 5-10 years, depending on funding. For now, Choset and his team are continuing to test the machines at mock disaster sites around the country.