Wind turbine blade inspection robots have a number of similarities with regards to the technology they use to overcome the challenges associated with their tasks.
Basically-speaking, all of the robots need to be able to maintain a steady grip on the blade to make sure that the images they attain are accurate, they also need to be remotely controllable and have a delivery system for getting them into position for the inspection.
Most inspection robots use some form of suction to adhere to the blades as they move across them, which also ensures they remain stable during the inspection.
Different inspection robots use different technologies for the actual inspection tasks – from high-precision video cameras for external, visual inspection to ultrasonic or infrared arrays that allow subsurface defects to be detected. Robotic inspection technologies can even include an ’electronic skin’ to “feel” the surface of a blade and collect data on the surface structure. Aside from inspection, these robots can also be used to carry out basic maintenance tasks, such as cleaning and resurfacing the blades.
As mentioned above, wind turbine inspection robots differ in design when it comes to how they are deployed and how they traverse the blades but, before we go into this in more detail, we need to mention the use of drones…
Drones have also been investigated as a solution for inspecting wind turbines. They are already used to inspect other large structures that are difficult or dangerous for humans to inspect, such as bridges, monuments and towers.
These drones use high resolution cameras and infrared sensors to detect heat signatures in the blades. As the sunlight diffuses through the blade, the difference in thermal properties demonstrate where subsurface damage has occurred.
However, for more accurate inspection, suction-based inspection robots are still preferred so, while a drone may be able to detect a potential defect, a crawling robot may still need to be deployed.
Drones have also been used to deliver inspection robots to wind turbine structures.
It is one thing to test a robot on a demonstration turbine blade in laboratory conditions, but these inspection robots need to be able to cope with extreme environments when deployed on a wind turbine in service.
The methods used to deploy and move the robot across the blade differ between different designs, but generally either use a legged crawling design or a tracked or wheeled design.
BladeBUG, for example, is a six-legged robot invented by entrepreneur Chris Cieslak. The robot uses suction cups on its feet to attach itself to wind turbine blades. These cups can change shape as the crawler moves along the blade, with a camera allowing the operator to see what is happening as they control it with a gaming controller. These robots can also be deployed at offshore wind farms using drones.
The International Climbing Machine, by contrast, is a remote controlled tank-like robot that can withstand high winds and successfully navigate over bolts and other obstacles. It uses an on-board vacuum suction system to create a seal as the caterpillar tracks drive it along the surface of the structure.
The Innovate UK-funded MIMRee (Multi-Platform Inspection, Maintenance and Repair in Extreme Environments) project is an example of various technologies coming together to aid wind turbine inspection. This project used an unmanned vessel, drone and crawling robot to create a complete system for transporting, deploying and retrieving a blade crawling robot as well as carrying out visual inspection via drone. Once the drone has been used for a preliminary inspection it can return to the unmanned vessel to pick up the crawling robot and place it on the turbine blade for a closer inspection such as high-resolution imaging and non-destructive sensing, including ultrasound.
Robots provide a number of advantages for wind turbine blade inspection, including being able to offer a safer, close-up inspection compared to humans and can also carry and use a range of inspection tools including cameras, sensors and artificial intelligence.
In addition, robots with scanners are able to find damage that cannot be seen with visual inspection by a human access team, locating smaller defects inside the blade, before they break to the surface.
Robots can also be deployed in conditions that would be unsuitable for humans to scale a wind turbine structure, while the turbines do not need to be shut down for maintenance when a robot is used.
Aside from the cost and the energy loss associated with shutting down a turbine, there is also a need to pay for crew transport vessels when using human inspectors. To offer some perspective, it is estimated that the MIMRee robotic system outlined above could save an average wind farm £26m over the course of its lifetime.
Robotic inspection offers detailed images of a structure, which are often superior to those attained by high-powered telescopes that can be hindered by poor light, cloud cover or precipitation.
As well as inspection, these robots can be used for other additional tasks, such as smoothing out the blade’s material and applying protective surface coatings.
Robots are changing routine maintenance procedures for wind turbines, leading to fewer dangerous ascents for human inspection teams and offering a cost-effective method of checking for surface and subsurface problems.
The move towards greater automation in wind turbine inspection follows the trend across industry to use robots for work that is dull, dirty or dangerous, improving safety, preventing costly performance problems, and reducing operating costs at the same time.