August 17, 2012 by Aaron Strauss
A team of mechanical engineering faculty at Drexel University received a $649,999 grant from the National Science Foundation to research the logistics of applying robotic arms to unmanned aerial vehicles, according to an Aug. 1 University press release.
Paul Oh, head of the Department of Mechanical Engineering and Mechanics, leads the project with the help of fellow professors M. Ani Hsieh, James Tangorra and Jin Kang. Their goal is to pave the way for the design of UAVs, also known as drones, which can perform a wide range of dexterous tasks near ground level, particularly in areas where human intervention is dangerous. One example of such a task, according to Oh, is infrastructure repair.
“Instead of hoisting someone up to a bridge, these robots might be equipped to fly up to the bridge and start welding,” Oh was quoted as saying in the press release.
The challenge Oh’s team faces is that robotic arms will exert forces on an aircraft that can destabilize it in flight. The team will seek to determine how feasible it is with the current state of aviation technology to design an aircraft that can remain stable despite these forces. Because a UAV with arms will need to be able to hover at a fixed point in the air, it would need to be designed as a rotary-wing aircraft, or rotorcraft, as fixed-wing aircraft cannot maintain altitude without forward motion.
The primary tool in this research will be a gantry system that can mimic the movements of a UAV. It can move and rotate in any direction, just like a rotorcraft. Oh and his team will install robotic arms on the gantry, and they will easily be able to measure all of the forces and torques at play in the system. Collecting the necessary data from these experiments will be easier with the gantry than it would be with tests using actual UAVs. An added advantage of the gantry is that it will be less expensive than experimenting with actual UAVs, which would inevitably crash and be severely damaged.
“The gantry serves as our surrogate rotorcraft, and instead of crashing it into the ground, we’ll be able to not have the expense and the destruction a crash would have, but we would just be able to simply reset. Now this is very important because when we suspend arms from the gantry, we’ll be able to see very clearly what’s happening to the aircraft before it crashes,” Oh said.
The researchers have already developed two prototype UAVs to help them determine what needs to be done to achieve a UAV that can reliably remain stable in flight while using robotic arms. The first prototype utilized a buoyancy envelope and a quadrotor, which is a system of four propellers. The second used only a quadrotor because the buoyancy envelope was found to be unnecessary.
Oh identified two central questions that the prototypes are intended to help answer, “[Can] we practically realize something like this? And if we can’t, then what are the fundamental gaps that research needs to uncover?”
The study is scheduled to take place over the next three years.