Whether it’s powering across rugged terrain, slipping through pipes or hurdling over walls, the snake-like OmniTread robot, recently developed by the University’s Mobile Robotics Laboratory, is pushing the limits of where robots can go.
Although serpentine robots are nothing new, OmniTread’s style of locomotion is unique, said Mechanical Engineering Prof. Johann Borenstein, who heads the University’s Mobile Robotics Lab. Each of the five segments making up the 26 pound robot are covered with moving tracks, which continuously propel the robot forward. Also unique is its use of pneumatic bellows — black cylinders located at the joints between the segments that inflate with compressed air to pressures reaching 80 pounds per square inch. The force produced by this expansion bends the joint to lift segments of the robot over obstacles.
“This configuration has never been done before,” said Malik Hansen, a Rackham student who helped construct OmniTread.
OmniTread’s innovations afford it a wide range of applications.
“Right now this is being funded by the Department of Energy … for inspection of radioactive storage sites,” Borenstein said. Because monitoring radioactive waste is hazardous for humans, the Department of Energy has been eyeing robots like OmniTread for the task.
Another possible application of OmniTread might be in industry because it can easily inspect confined spaces, such as pipes, Borenstein added.
But perhaps OmniTread’s most important purpose will be to seek out survivors in disaster areas.
“To me the inspiration was my desire to develop a robot that can crawl through the rubble of a collapsed building,” Borenstein said.
When an earthquake reduces a building to rubble, survivors may need to be located quickly. Because it may be too dangerous or even infeasible for humans to comb through such a landscape, robots like OmniTread may be the perfect solution, with their ability to crawl through small niches and crevices. Disasters such as Chernobyl — the Russian nuclear power plant that nearly experienced a meltdown in 1986 — and Sept. 11 might also have benefited from a robot as capable as OmniTread, Borenstein said.
The Mobile Robotics Lab began work with serpentine robots in 1998 when the OmniPede, the predecessor to the OmniTread, was developed. The prototype had three segments and walked on six feet. Together, the leg and foot resembled the cross section of an umbrella, which moved in a continuous shoveling motion to propel the robot forward. However, this model was eventually found to be problematic when, in deep gravel, the robot’s legs would squeeze and dig into the gravel and become stuck.
“The main problem that I identified in the OmniPede was that there were too few feet,” Borenstein said. “Too little of the circumference of this vehicle was surrounded by moving elements.” He realized that the solution would be in having the whole body of the robot be entirely surrounded by moving elements. “No matter how the robot is touching the environment, it would provide propulsion,” he said.
From this shortcoming of its predecessor, the OmniTread was developed. The current model is called the OT8 – “8” for the fact that it can fit through a hole eight inches in diameter. The ease at which it negotiates rubble beds and climbs walls has demonstrated the effectiveness of the OmniTread design, Borenstein said.
The OT8 model, however, is limited. It requires a tether to supply it with power, air and input from three human operators. One person controls the first two joints, a second person controls the trailing two joints and a third person is needed to control forward-backward speed.
Improvements will be made with the development of an OT4 model, which will be half the diameter of the OT8 and won’t have a tether. It will have seven segments and one hour of onboard battery power. They hope to have the prototype ready by June.
“Downsizing the robot is not nearly as difficult as designing it from scratch,” said Justin Tesmer, a Rackham student working on the OT4. Still, he added, implementing both onboard power and an air supply will pose a challenge.
Naturally, applications of the OT4 will be even more extensive than those of the OT8. “It’s mostly better for the military applications,” Borenstein said. The mobile OT4 could be used to scout out dangerous enemy territories, such as caves, providing vital surveillance and reducing the danger for troops.
Borenstein hopes to eventually minimize the number of operators for OmniTread to make the robot more efficient.
“I’m predicting in three years we’ll have the capability to run a serpentine robot like this one with a single guy who’s driving it, and with the single guy not seeing the robot itself, but rather having a picture from a nose camera.”
Giving OmniTread complete autonomy and eliminating human operators outright is the ultimate aim though, Borenstein said. “There is a need for getting a computer to synchronize and coordinate all this.”
He added that fitting the robot with an onboard computer system will be very difficult, and probably won’t be made a reality for another decade. Motivation for such an onboard computer is cost effectiveness in industry.
“You want to have zero operators for it so you don’t have to pay somebody,” he said.