Swooping down like a mechanized bird of prey comes the latest nightmare fuel from the robotics researchers at the University of Pennsylvania: a motorized claw attached to a drone that can grab objects and carry them away.
In a recent video, the university’s GRASP team — for General Robotics, Automation, Sensing and Perception — show an AscTec Hummingbird quadrotor drone diving onto a cylinder and snatching it with a gripper claw before flying away. Taking a cue from how eagles work, the researchers believe that diving drones can make for drones that weigh less and use less power, using acceleration velocity gained from diving to quickly regain altitude. It may even be possible to build drones that perch. The drone is certainly lightweight enough: the quadrotor and the gripper-claw combined weigh less than a pound and a half.
The GRASP team are not newcomers to the field of out-there robots — like the autonomous microchopper swarm the team designed to fly in formation. Now the researchers believe swooping eagle-bots could make for drones that “achieve immediate silence in stealth operations,” and help “improve mission duration by reducing hover time,” (.pdf) according to a recent paper by GRASP team members Justin Thomas, Joe Polin, Koushil Sreenath and Vijay Kumar, which the team will present at the IDETC/CIE tech conference in August. The drones could also be used in “rescue operations where speed and time are critical, and in operations requiring [an unmanned aerial vehicle] to quickly swoop down and pick up an object of interest.”
To build the gripper-claw, the team first created a two-pronged fork surrounding a spherical chamber. When attached to a servomotor, the prongs could open and close, and scoop up a plastic ball into the chamber. But the gripper wasn’t very efficient when attached to the drone, and would fail to pick up a ball when traveling faster than one meter per second.
So the team redesigned the gripper. They created a three-fingered claw made of thermoplastic with a rubber skin, which improved its grip. The claw was also more flexible than the two-pronged fork, allowing it to pick up a wider variety of objects. And to improve its ability to pick up objects when traveling at faster speeds, the researchers attached the claw to a rotating arm, which simulates how an eagle draws its claws back while diving, reducing the relative speed between itself and its target.
Still, the drone didn’t grapple as well as an eagle — but it was close. By making these few modifications, the researchers were able to triple the speed at which the gripper could grapple objects while on the move.
What comes next depends on whether the researchers want to improve the quadrotor’s vision, boost its landing skills or further improve the gripper. The researchers suggest that adding a motion-capture system could allow the robot to track its prey and “make in-flight corrections using data from an on-board camera.” Another option is for “autonomous detection of candidate sites for perching and controlled landing on perching sites.” This, the researchers write, would be less energy-intensive and quieter than hovering. The final improvement could mean using a manufacturing process called shaped deposition to improve its grip.
So the researchers already have a drone with an eagle’s ability to swoop down and grip its prey. And they want the next version to be stronger, more accurate and able to find its way to a perch — and do it real stealthy-like.