Scientists Developing Robotic Arms To Clean Space Debris
Of needs and wants, there is often much confusion. Yet little doubt exists among American policymakers and the scientists advising them of the imperative to develop a robotic arm capable of quickly reacting to objects thrown its way -- dodging or catching them with the alacrity of a shortstop on a baseball diamond.
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Lt. Gen. John W. Raymond, who heads the military's space command, testified before Congress in early May on the growing threat space junk poses not only to assets in near-Earth orbit but on the ground, too. That threat was dramatized last year in the Hollywood film Gravity, in which a pair of astronauts played by Sandra Bullock and George Clooney attempt to return to Earth after a mission-killing strike by space debris.
"To meet the demands of the dynamic space environment, [the space command] is focused on three operational objectives: provide timely and accurate warning and assessment, support national users and Joint and Coalition forces, and protect and defend our space capabilities and prepare for contingency operations," Raymond told the House subcommittee on science, space, and technology in written testimony.
Yet just several days later, Swiss scientists from Ecole Polytechnique Federale De Lausanne announced a possible solution in a new bionic arm measuring 1.5 meters with three joints and four fingers. Standing motionless, the robot reacts with preternatural quickness to a variety of objects thrown its way, catching or dodging tennis rackets, balls, and even glass bottles. Described in a paper published Monday in IEEE transactions on robotics, the bionic arm is capable of reacting in less than five-hundredths of a second.
"Increasingly present in our daily lives and used to perform various tasks, robots will be able to either catch or dodge complex objects in full-motion," says Aude Billard, who led the research. "Not only do we need machines able to react on the spot, but also to predict the moving object's dynamics and generate a movement in the opposite direction."
To achieve this robotic breakthrough, researchers successfully integrated several parameters required for the quick-reacting functionality. "Today's machines are often pre-programmed and cannot quickly assimilate data changes," Billard said in a press statement. "Consequently, their only choice is to recalculate the trajectories, which requires too much time from them in situations in which every fraction of a second can be decisive."
Interestingly, scientists are finding they cannot simply imbue a robotic arm with such functionality but must guide the system through a strangely human learning process of trial and error called "programming by demonstration." With this approach, Billard and her colleagues led the robotic arm through a series of lessons demonstrating the possible trajectories of objects thrown toward its location, like parents helping a child to learn fine motor skills used for throwing and catching.
In the first lessons, researchers began by throwing several different types of objects toward the robot, allowing the system to create a kinetics model based on the varying trajectories, speeds, and rotational movement. This data captured by the system was then translated into an equation the robot could not only understand, but refine through time.
"During the few milliseconds of the approach, the machine refines and corrects the trajectory for a real-time and high precision capture," Billard says. "This efficiency is further enhanced by the development of controllers that couple and synchronize the movements of the hand and fingers."
By literally arming a satellite with the robotic capability, scientists say they might soon create the space-faring version of a street cleaner. Today, NASA tracks more than 21,000 artificial objects larger than 10 centimeters, many of which pose grave harm to assets and personnel in near-Earth orbit.
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