Mobile inspection robots creep over pipelines on magnetic wheels and use special sensors to detect critical spots: what sounds futuristic is already reality. Yet when these robots need to be maintained and inspected, until now the only resort was humans. Scientists at the German Aerospace Center (DLR) now were able to integrate an industrial robotic gripper arm with seven degrees of freedom into a free-flying helicopter system for the EU project ARCAS (Aerial Robotics Cooperative Assembly System) for the first time. This makes it possible to safely inspect and service the robots on the pipelines. Similar systems could also be used to service satellites or even to construct habitats on other planets.
Replacement for the human hand
Humans have long wanted to employ intelligent tools to inspect pipelines and industrial facilities. The reason is simple: To get to difficult-to-reach places, scaffolding would have to be built, which is time-consuming, expensive and extremely dangerous. This is why more and more robots are doing this work. This is where the scientists as the DLR Institute of Robotics and Mechatronics from Oberpfaffenhofen start. Their vision: to replace human hands at hard-to-reach or hazardous places with the gripper arm system on an autonomous helicopter.
Video: Demonstration of the technology
In order to reach the desired position, the system navigates autonomously with GPS. Once there, it switches to a precise image processing system based on several built-in cameras. The inspection robot can thus be precisely located and the gripper arm precisely positioned on the object. With the current state of development of the system, it is possible to precisely grasp the magnetic maintenance robot down to one centimeter. Once seized by the arm, the helicopter can autonomously transport the maintenance robot to a safe place or, in the future, it can also repair it on-site while hovering above it.
Force-torque sensors are also installed in each of the seven joints of the arm. They ensure that the robotic arm retracts independently if objects in the environment are accidentally touched. Objects with a mass of up to eight kilograms can be grasped. The developed algorithms combine the control of the robotic gripper arm with the control of the helicopter in order to minimize mutual influence. This ensures the stability of the overall system and the high gripping precision.
Demonstration of grasping with a maintenance robot model:
The dual-rotor helicopter by SwissDrones vewas used for this research work.
However, the system not only can be used to repair maintenance robots. The possible applications are as versatile as they are exciting: multiple gripper arms could repair defective satellites from one or more mobile platforms, install new modules on the ISS or help build a moon habitat. In the opinion of the DLR scientists, the mathematical and technological questions are very similar in these applications and the new technology is only the beginning of completely new possibilities.
Some of the research work was conducted as part of the DLR HELMAN (HELicopter based MANipulator). During the ensuing AEROARMS project (AErial RObotics System integrating multiple ARMS and advanced manipulation capabilities for inspection and maintenance) the technology will be developed for industrial applications. The project is part of the EU program Horizon2020. Alongside the DLR, the Universität Sevilla, LAAS-CNRS, Consorzio C.R.E.A.T.E., FADA-CATEC, TÜV Nord, UPS-CSIC, Elektra UAS, Alstom Inspection Robotics and Sensima Insepction SARL are involved.