Although modern jet airliners may be at the cutting edge of technology, assembling them is, in many ways, still as much of a craft as 18th century shipbuilding, requiring loads of skill and manual labor to get the job done. The Fraunhofer Institute for Machine Tools and Forming Technology (IWU) in Chemnitz, Germany wants to bring airplane construction into the 21st century with a snake-like robot that can assemble airplane wings by reaching into narrow, hard to reach cavities.
Airplane manufacturer Airbus expects to see air traffic triple by 2030, with major airports handling close to half a million passengers a day and Fraunhofer says that current aircraft construction methods will have difficulty keeping up with the demand for new planes. One answer is to automate assembly, but wings pose some tricky problems that most industrial robots can’t handle because they’re too inflexible and their reach is too short to extend the up to five meters (16 ft) required inside the wings.
Modern wings aren't just metal planks sticking out of a fuselage. They’re a complex collection of fuel tanks, hydraulics, power cables, engine supports, ailerons, flaps, ribs, struts, spars, and stringers. This results in all manner of small, hollow chambers that workers need to get into to drill holes, attach bolts, and seal joints.
Needless to say, it’s extremely slow, hard work that has to be done in the presence of solvent fumes. Look in a modern airplane assembly or maintenance manual and you’ll find detailed instructions for workers on how to wiggle into a crawl space and reach a widget. As a result, major airliner manufacturers are leading employers of little people, who are hired to work in confined spaces, such as wings.
The Fraunhofer approach was to come up with a 60 kg (132 lb) robot with an arm that resembles an automated snake. It’s built in eight articulated sections with a total length of 2.5 m (8.2 ft), weight of 15 kg (33 lb), and ending in a hand or inspection camera. According to Fraunhofer, the key to the snake-like robot is a patented gear system with motors generating 500 Nm of torque integrated into each of the arm’s eight sections. These, combined with a cord-and-spindle drive system, allow each section to turn independently up to 90 degrees.
"The robot is equipped with articulated arms consisting of eight series-connected elements which allow them to be rotated or inclined within a very narrow radius in order to reach the furthest extremities of the wingbox cavities," says IWU project manager Marco Breitfeld. "That’s why we often refer to the system as a snake robot.”
Currently, the robot is undergoing mechanical design and testing and will be displayed at the Automatica trade show in Munich from June 3 to 6. The next stage in the project involves installing the robot on a mobile platform or rails, allowing it to travel along the length of the wing while working. Fraunhofer says that a full-scale version of the robot should be ready by the end of the year.