This website contains images and video of a series of snake robots built by Dr. Gavin Miller as part of a self-funded project to investigate snake locomotion applied to robotics applications. The question naturally arises, why snake robots? Biological snakes occupy a wide variety of ecological niches, ranging from arid desert to tropical jungle as well as swimming in rivers and oceans. Abandoning limbs and developing elongated spines has proved an effective survival strategy, allowing snakes to hunt underground in confined tunnels, above ground in grassy fields and up in the tree-tops, even falling in a controlled glide from one tree to the next. By attempting to build robots that emulate and perhaps match the capabilities of their biological counterparts, it is possible that we will create useful tools capable of carrying sensors, taking samples, and making physical changes in a wide variety of environments. The robot designs evolved from one generation to the next, incorporating lessons learned from previous prototypes.

Requirements for the designs included that they were to be untethered, which meant they had to carry their own computers and batteries. They were to be radio-controlled, to avoid the problem of artificial intelligence and sensing. They needed to be simple to drive. The large number of segments had to be controlled using one or two joysticks. The snakes were given the designation S1, S2 and so on, in homage to John Harrison's clocks H1, H2 etc. The long term goal is to enable exploration in dangerous environments and to aid in search and rescue. A hoped-for side effect is to encourage people to look at snakes in a new way, appreciating what they have to teach us about navigating and traversing the world.

The Goal: A Snake Robot Search-And-Rescue Mission

This scenario is purely imaginary and is presented to help provide a goal for future developments rather than stating current capabilities.

Following a major earthquake in the San Francisco Bay Area, old Victorian houses lie in ruins, the ground floors having collapsed as upper stories remain standing but unstable, threatening to fall at the next aftershock. Willing rescuers stand ready to climb and dig, but the question remains of whether the risk of injury to them is worth the chance of finding someone buried under the rubble. Fortunately, a new generation of search-and-rescue snake robots is now available to answer that question. Pulling out a 2-meter long tube from under the stretcher in the paramedic ambulance, the operator opens one end and powers up the system. She removes a remote control unit which has a video screen built into it, fed by the camera from the head of the robot, with a graphical overlay allowing a range of optional behaviors to be activated. There are also two joysticks and a variety of other buttons and knobs for controlling subsidiary parameters of the system. The would-be rescuers carry the tube as close as possible to the wreckage, and slide the snake robot out of the end of it. A thin composite cable goes from the inside of the tube to the tail of the snake, supplying power and carrying data in both directions. The operator activates the snake's locomotion system and moves it forwards. It automatically adapts to the uneven ground and rises up over small obstacles while maneuvering around the larger ones. Pausing every few feet to listen for signs of survivors, the snake robot's head relays binaural stereo sound back to the operator. Hearing no cries for help, the snake is directed towards a 20-cm wide gap where one house has collapsed and is leaning against another. Approaching the aperture, the snake transitions to rectilinear motion, and uses infrared distance measuring devices and flex-sensor whiskers to center it between the walls. As it moves further inside, the operator switches to the infrared-sensitive camera and illuminates the scene with high-power LEDs. As the snake progresses, it sweeps the area up ahead with a pyroelectric device to look for body heat. Its underbody (ventral) scales pull the robot along the ground like a small conveyor belt, even pushing it through the tangled heaps of cables left by the collapsed building. Then it reaches a region of shattered plaster and broken rubble, which provides insufficient grip for forward locomotion. The tether is also pulling on the snake robot's tail, caught as it is on previous obstructions. At the system's on-screen suggestion, the operator switches the snake robot to internal power and detaches the tip of the tail by remote control. This now becomes a base station communicating wirelessly with the snake robot and relaying information back to the operator. She instructs the snake to begin concertina motion in which the snake robot coils into an s-shaped curve until it can feel the walls of the fallen houses pushing in on it from both sides. Small scales on the skin of the snake robot grip the walls and allow it to push forwards by changing the amplitude of its coils in one region while gripping with another. Once through this difficult area the snake comes to a region of the original floor of the house. The snake swishes its head from side to side to sweep the area clean of rubble. Using a downward-sensing ultrasonic device in the chin of the robot, the operator determines that it is possible to make a hole leading directly to the basement of the building. The snake robot it instructed to detach, from under its head, a small shaped-explosive charge, which it leaves on the floorboards and slithers back slightly before detonating the charge and making a 10-cm hole in the floor. Curling its head downwards through the opening it pushes forwards by a meter or so and then uses its neck to point its head in a variety of directions looking for survivors. There is a peak detected by the pyroelectric sensor, and the snake freezes, going silent. The microphones pick up the faint sounds of breathing and the infrared camera indicates a blob in approximately the direction from where the sounds originated. The operator pinpoints on a map where the survivor is most likely to be found. The location is shown in relation to a reconstructed 3-D model of the path taken by the snake robot, along with the surfaces it sensed. Other rescuers are given the go-ahead to carefully approach the building as the operator talks to the survivor over a loudspeaker carried by the snake robot, letting him know that help is one its way and trying to discover the extent of his injuries.

This scenario is an extract from "Snake Robots for Search and Rescue", a book chapter about the snake robots on this website in Neurotechnology for Biomimetic Robots.