Snake Monster robot can be easily reconfigured to suit user needs

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The Snake Monster robot is claimed to be the precursor to a range of robots intended to be built using a modular system (Photo: CMU Robotics Institute)

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Carnegie Mellon University (CMU) has created a new robot that has six legs, looks creepily like a spider when it walks, and is dubbed "Snake Monster". Not exactly endearing traits, but the Snake Monster isn’t designed to win any popularity contests. It has been created as an easily reconfigurable platform using a modular system architecture that may be easily programmed to govern robots with a varied array of configurations.

Designed and created in around six months in the lab of Howie Choset, a professor in CMU's Robotics Institute, Snake Monster is claimed to be the precursor to a range of robots intended to be built using a modular system. Current work being carried out on various other modules in the lab include force-sensing feet, wheels and tank-style treads that will allow users to modify the base structure into a selection of totally different robots suited to a range of tasks.

"By creating a system that can be readily reconfigured and that also is easy to program, we believe we can build robots that are not only robust and flexible, but also inexpensive," said Choset, who led the team responsible for the robot. "Modularity has the potential to rapidly accelerate the development of traditional industrial robots, as well as all kinds of new robots."

Choset’s lab has a history of creating segment-jointed, snake-style robots designed for all types of applications, from inspecting nuclear power plants to slithering down the throats of surgical patients. The similarity in the construction and operation of the legs of the Snake Monster to those earlier CMU robot incarnations gives it its name. Unlike the earlier robots, however, the Snake Monster doesn’t roll along the ground or slither along the floor. Instead, it uses its legs to move along in a tripod gait with three legs in the air at any time – two on one side and one on the other.

Weighing in at a total of around 18 lb (8 kg), the robot has six multi-jointed legs that are capable of a reach of about 12 in (30 cm). Sporting a rectangular body, and currently supplied with power via an umbilical tether, the Snake Monster is capable of ambulation in any direction and has the ability to climb over obstacles.

In addition, a series elastic actuator consisting of an electric motor with a spring in series with its output shaft that allows the actuator to gauge and control the force it exerts, and the forces exerted upon it to help protect from high impacts. In other words, the actuator allows the linkages to respond in a way similar to that found in living organisms.

"When we push the Snake Monster forward, the joints in the leg 'feel' the force of the robot being pushed and, then, in an effort to zero-out the force it feels, the robot walks in the direction it is being pushed," said Choset. "When the robot goes over bumpy terrain, the springs in the series elastic actuators allow us to not perfectly plan the foot steps, but rather let the robot automatically conform to the environment the way animals do."

Using the hardware knowledge gleaned from their many years of snake robot construction, Choset and his team have created small, powerful, interconnected modules as the basis for their new Snake Monster and the line of reconfigurable robots promised to follow it. They have also relied on the many years of information gathered on controlling snake robots to allow them to build and develop an easily-programmable and extensible system architecture to control robots a wide variety of configurations.

"The architecture is built on Ethernet computer networking technology," said Choset. "Ethernet doesn't require that the computers connected to it be of a specific type, but that they all communicate with each other in the same way. The interfaces used in the modular architecture allow robot designers to focus on specific capabilities without having to worry about detailed systems issues or having to modify the robot later."

Sponsorship was received from the Defense Advanced Research Projects Agency (DARPA) and Snake Monster, along with several other of CMU’s robots, will be demonstrated in the finals of the DARPA Robotics Challenge running June 5 - 6 in Pomona, California.

The short video below shows the prototype Snake Monster in action.

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