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A robot inspects a wind energy converter's rotor blades for possible damage.

(© Fraunhofer IFF)

Wind turbines must withstand intense natural forces all year round. But inspecting the rotor blades for damage is no easy task: The heights involved are enough to make anyone dizzy and the human eye cannot possibly detect all problems.

Now researchers at the Fraunhofer Institute for Factory Operation and Automation (IFF) have found a solution to this conundrum: They have developed a new robot that inspects wind energy converters and detects the most minute damage – even below the surface.

The robot, called RIWEA, hauls itself up a rope foot by foot until it reaches a wind turbine's giant rotor blades. Then it goes to work. It thoroughly inspects every inch of the rotor blades' surface. Nothing escapes it. It registers any crack and any delamination in the material and relays their exact positions. In this capacity, a robot is clearly superior to humans.

The IFF researchers are experts in robotics, for instance to clean facades, inspect sewer lines or assist humans. Their new "windbot" RIWEA is made mostly of glass fiber reinforced plastics.

Rotor blades are pummeled by the elements and must withstand wind, inertial forces and erosion.

Humans have hitherto inspected wind turbines at regular intervals. In this daunting task, technicians must closely examine large surfaces – a rotor blade can be up to 60 meters (197 feet) long – in airy heights.

"Our robot is not just a good climber," said Norbert Elkmann, coordinator of the Fraunhofer project. "It is equipped with a number of advanced sensor systems. This enables it to inspect rotor blades closely."

Are there cracks in the surface? Are the bonded joints and laminations in order? Is the bond with the central strut damaged?

The inspection system consists of three elements: An infrared radiator conducts heat to the surface of the rotor blades. A high-resolution thermal camera records the temperature pattern and thus registers flaws in the material.

In addition, an ultrasonic system and a high-resolution camera are also on board, thus enabling the robot to also detect damage that would remain hidden to the human eye. A specially developed carrier system ensures that the inspection robot is guided securely and precisely along the surface of a rotor blade.

"It is a highly complex platform with 16 degrees of freedom, which can autonomously pull itself up ropes," said Elkmann.

The advantage of this system: It can perform its job on any wind energy converter – regardless of whether it is large or small, on land or offshore. The robot always delivers an exact log of the rotor blades' condition, keeping humans safe and not missing any damage.

The Fraunhofer-Gesellschaft is the largest organization for applied research in Europe. Comprised of more than 80 research units, including 57 Fraunhofer Institutes, at 40 different locations in Germany, it also has research centers and representative offices in Europe, the United States, Asia and in the Middle East.

Source: Young Germany/Fraunhofer-Gesellschaft

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