SNAG biomimetic robot grasps like a falcon

Researchers in the US have designed a biomimetic clawed robot known as SNAG that can land and perch on branches as well as grasp objects like tennis balls.

Described in Science Robotics, SNAG (stereotyped nature-inspired aerial grasper) is based on the legs of a peregrine falcon. 3D printed structures mimic bones, while motors and fishing line replicate the bird’s muscles and tendons. Each of the robot’s legs has a motor for moving back and forth and a second motor for grasping. A tendon-like mechanism in the legs converts the energy from impact with the branch into grasping force, triggering a high-speed clutch in around 20 milliseconds. Once the claws are locked on to the branch, an accelerometer confirms the landing and initiates a balancing algorithm to stabilise the robot.

“It’s not easy to mimic how birds fly and perch,” said William Roderick, a graduate student from the labs of Stanford University engineers Mark Cutkosky and David Lentink. “After millions of years of evolution, they make take-off and landing look so easy, even among all of the complexity and variability of the tree branches you would find in a forest.”

The researchers attached SNAG to a quadcopter drone to test how the grasping platform could catch and carry objects, as well as perch on various surfaces. During COVID-19, Roderick moved equipment from Lentink’s lab at Stanford to rural Oregon where he set up a basement lab for controlled testing. He sent SNAG along a rail system that launched the robot at different surfaces and at different speeds to see how it performed in various scenarios. Roderick also confirmed the robot’s ability to catch objects thrown by hand, including a prey dummy, a small bean bag and a tennis ball.

The research was funded by the Air Force Office of Scientific Research and the National Science Foundation. Some of the many potential applications for the biomimetic robot include search and rescue operations and wildlife monitoring, with a perching robot likely to be able to get close to birds in their natural habitat and allow for new methods of research.

“Part of the underlying motivation of this work was to create tools that we can use to study the natural world,” said Roderick, both of whose parents were biologists. “If we could have a robot that could act like a bird, that could unlock completely new ways of studying the environment.”