Researchers unveil drones that minutely inspect high-rise buildings

A German research body has developed a sophisticated flying robot that can inspect tall structures in minute detail in just a fraction of the time it would take humans to do it.

The remotely controlled "octocopter", so called because of its eight rotors, inches along the structure’s exterior taking thousands of photographs to detect cracks and defects. In hours it can complete a task that a team of surveyors would need days and expensive access equipment to perform.

This means more security for buildings and people– Christian Eschmann, Fraunhofer Institute

"For a 20 by 80 meter wide façade, a test engineer needs about two to three days," said Christian Eschmann, researcher at the Fraunhofer Institute for Non-Destructive Testing IZFP in Saarbrücken, Germany. "Our octocopter needs three to four hours for this."

The institute says many buildings, factories and bridges in Germany were built in the postwar years and now show signs of ageing. Equipped with a high-resolution camera, the drone examines a structure’s façade for cracks, defective joints, or chipped and crumbling concrete. 

Such inspections used to be a difficult and laborious process, with engineers using their naked eyes to mark cracks manually on 2D maps. It was an error-prone procedure and required getting to places often accessible only by helicopters, cranes, industrial climbers and scaffolding.

"To inspect their condition and prevent hazards to people, a lot of effort still has to be devoted to buildings that are difficult to access," says Eschmann. 

The octocopter also has sensors that adjust for wind gusts, helping it keep a stable altitude and avoid crashing into the building. The image yield is high: a mere 15-minute flight can result in up to 1,200 photos. The digital images are then combined to create 2D and 3D models.

The institute says it has been working on the drone since 2011, but publicised the work just this month.

There is more work to be done. Next on the research agenda is software for damage recognition, image processing and documentation. 

The octocopter must also be controlled manually. This is a big limitation because the controller must maintain visual contact with the device, which limits how high it can go. Eschmann and his team are now working on navigation sensors that would allow the drone to follow a predetermined route. 

"It’s a bit like flying on rails," said Eschmann, adding that this will take at least another year of development.

He said the drone could not completely replace humans. "Our micro-airplane is no substitute for experts or a close-up inspection. However, the octocopter accelerates the test procedure and enables permanent monitoring and documentation from the beginning. 

"Design defects and warranty claims can be identified at an early stage, so appropriate repair measures can be taken in time. This means more security for buildings and people."

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