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Cobots and Simulation Software for Non-Destructive Evaluation

Albert Nubiola
By Albert Nubiola Founder, RoboDK
To increase available working area, two UR cobots are fixed onto a linear actuator from Festo. (All images provided by RoboDK)

In aircraft manufacturing, the issue of safety always prompts innovative new processes, including those used to ensure every fuselage has undergone thorough inspection. A team at NASA’s Langley Research Center is now using multiple collaborative robots (cobots) from Universal Robots equipped with simulation software from Montreal-based RoboDK to automate and streamline the inspection of aircraft fuselages.

The team began using RoboDK a few years ago, deploying a UR10 cobot in an infrared inspection system. At the time, NASA was creating the first proof-of-concept, demonstrating that the automated setup could do as good a job or better than manual inspection with less labor. The project advanced over the past two years, and the team now uses dual cobots combined with an external axis and a more complex type of infrared inspection.

The inspection task that the team performs is a type of “non-destructive evaluation.” As the name suggests, this refers to a large group of testing processes that are used to detect flaws in a manufactured product without destroying it. In particular, the team at Langley performs infrared detection, which involves heating the fuselage and then using an infrared camera to detect flaws in the heated material.

“In conventional tomography, you heat a large area and then inspect one section at a time,” explains branch head Elliott Cramer. “Currently, most of these inspections are done on a point-by-point basis. You’ll inspect a small area, then move over the surface either manually or with some kind of scanning system.”

Using dual robots has allowed the team to change their method to line scan tomography, which involves moving a heating element and an infrared camera in a consistent line. “This is actually a moving inspection that’s very well suited to the use of robotics,” Cramer notes.

The Benefit of Two Cobots Over One

NASA started out using only one cobot with one sensor; the new inspection method now requires two cobots (both UR10s) working together. One cobot holds a heating element, which it moves in a consistent line along the fuselage; the other one holds a FLIR infrared camera.

This moves the fuselage immediately behind the heating element. The captured image is used to form a scan, which the team analyzes to detect defects in the material. To increase the task’s working area, the two cobots are fixed onto a Festo linear actuator. This allows them to move along a much longer length of the fuselage and ensures that the robots move at exactly the same speed.

A digital representation of the scanning process that illustrates the commands used by the cobots.

Compared to performing the scans manually, there are several benefits to using robots in this type of inspection: repeatability, speed, accuracy, autonomy and coverage.

One of the major problems with manual scanning is that the sensor can never be positioned in exactly the same place every time. Repositioning the sensor by hand to double check a reading is time consuming. Using cobots removes this problem. “The main advantage is repeatability if you need to go back to an inspection location again, either to reinspect or with another technique,” adds Cramer. “Having the robots do it allows you to go back very accurately.”

Another issue with manual inspection is that it takes a long time. Improving throughput was a core aim of this application. “The goal of this project is to increase the rate of inspection and the accuracy of inspection that’s currently going on, whether that’s done in the manufacturing environment right after the fuselages have been made or at a later time during in-service inspection of the aircraft,” Cramer explains. “You can now cover large areas and handle the complex curves of the aircraft, but much more rapidly. This is designed to speed that process up but still get the same accuracy.”

The team’s previous manual inspection required several technicians working together. This was quite inefficient. However, even with multiple people, it wasn’t certain that they would achieve full coverage of the aircraft fuselage due to the inaccuracies caused by manually placing the sensor. Cramer says both of these problems have been overcome by using the robotic system. “It can autonomously go off and do the inspection once it’s been programmed, ensuring 100% coverage.”

How NASA Uses RoboDK

Because it’s easy to combine multiple UR cobots with RoboDK and incorporate external axes into the programming, RoboDK plays a key part in NASA’s inspection application. NASA’s inspection process is:

  1. With a Creaform optical scanner, engineers create a surface map of the fuselage. This is done manually.
  2. Using the scanned data, NASA is able to accurately locate the fuselage in space and relative to the robots.
  3. The team creates the path in RoboDK, which automatically generates the cobot code.
  4. The cobots perform the inspection task and build an infrared scan of the fuselage.
  5. Using Matlab, engineers analyze the scan for defects.

NASA has achieved an impressive improvement of its inspection process using UR cobots and RoboDK. And the team has further plans for the application.

“One of the other things that we’re working toward is the ability to automatically map the data that we collect to an image of the fuselage,” Cramer says, underscoring the importance of having a digital record. “That will ensure the long-term durability of those vehicles as they fly. The ultimate goal is to increase the safety of air travel.”

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