IROS 2013: UAVs Get a Grip With Full-Size Robot Arms


As amazing as flying robots are, there's a limited amount of useful stuff that they can do today. Oh, they're great for surveillance and inspection, there's potential to use them to deliver stuff, and in some specialized circumstances we've seen them cooperatively building structures. But to really be useful in the way that we've come to expect from robots, they're going to need to be able to move a variety of objects at will, picking them up and putting them down whenever and wherever they need to. We saw some of the first examples of this at IROS, giving a whole new meaning to the term “mobile manipulator.”

The easiest way to put a mobile manipulator on a UAV is to just bolt a robot arm right on there, which is what DLR (the German Aerospace Center) is trying out. They've got a 7-DOF KUKA industrial arm mounted upside-down underneath an autonomous, turbine-powered mini helicopter. Using an on-board vision system, the robot is able to detect and grasp a pole stuck into the ground. This is tricker than it sounds, because even as the helicopter moves the base of the arm, whenever the arm moves, it changes the center of gravity of the system and moves the helicopter as well:

In terms of practicality, this is simply the very first step, but DLR is looking forward to some heavy lifting:

We think that for many practical applications the usage of a fully actuated arm with a payload of about 10 kg is required. So the setup we presented in this paper is a starting point for practical investigations of these applications and for developing of corresponding technologies.

“First Analysis and Experiments in Aerial Manipulation Using Fully Actuated Redundant Robot Arm,” by Felix Huber, Konstantin Kondak, Kai Krieger, Dominik Sommer, Marc Schwarzbach, Maximilian Laiacker, Ingo Kossyk, Sven Parusel, Sami Haddadin, and Alin Albu-Schaffer from the Institute of Robotics and Mechatronics, DLR, was presented earlier this month at IROS 2013 in Tokyo, Japan.



Meanwhile, over in South Korea, a much smaller arm on a much smaller UAV is already autonomously moving objects from place to place with a two degree of freedom arm:

After taking off, the quadrotor moves to an object. It is assumed that the position of the object is known in advance (measured by Vicon beforehand in this case), which will soon be relaxed using vision. Once the quadrotor arrives at the designated position, the robotic arm moves to the position of the object and grabs it. 

While grabbing the object, the quadrotor moves to the next place to reach where the object is laid down. When the quadrotor gets close enough to the designated location, the robotic arm manipulates the object to release it at the desired position. Here, the releasing point is located inside of a shelf where only a two or higher DOF robot arm can reach. After completing the above missions, the quadrotor goes back to the place where it took off and lands.

The trick to this is dealing with the quadrotor and the arm as a single combined system, as opposed to to discrete systems that are controlled independently. The researchers came up with an adaptive controller that can compensate for movement of both the arm and the helicopter to allow for successful grasps. The paper's intro sums things up nicely:

By combining the mobility of the aerial vehicle with the versatility of a robotic manipulator, the utility of mobile manipulation can be maximized.

That's right: look out all you ground-based mobile manipulators, because flying robot arms are coming for you.

“Aerial Manipulation Using a Quadrotor with a Two DOF Robotic Arm,” by Suseong Kim, Seungwon Choi, and H. Jin Kim from Seoul National University, Seoul, South Korea, was presented this month at IROS 2013 in Tokyo, Japan.




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