Mobile Sensor-Scanner Gauges Engine Condition Indicators in 3D

Researchers at the Fraunhofer Institute for Applied Optics and Precision Engineering IOF (Fraunhofer IOF) have developed a portable sensor-scanner for building comprehensive 3D models of complex structures such as aircraft engines. The Fraunhofer IOF team collaborated with MTU Maintenance, a Langenhagen, Germany-based aircraft engine service provider, to develop the sensor, which is called goSCOUT3D.

MTU wanted to document the incoming and outgoing condition of its engines using a 3D digitalization process. The company had been using classic compact cameras that could provide only a partial record of an engine’s condition. The company wanted a user-friendly system capable of complete three-dimensional digitalization.

The developers of goSCOUT3D aim to make 3D surveying easier and more flexible. Courtesy of Fraunhofer IOF.

Virtual 3D models of actual objects can help industrial manufacturers such as MTU manage quality control. But the more complex an object, the more difficult it is for a sensor to measure and transfer the object’s shape and content to a 3D model. The goSCOUT3D sensor can build digital models that show a high level of detail, down to the smallest screws used in a piece of equipment.

The developers based their approach on the principles of photogrammetry, the science of making measurements, maps, or 3D models from photographs. Stefan Heist, group leader of 3D sensors at Fraunhofer IOF, said that in this measurement method, high-resolution 2D color images of a measured scene are taken from numerous angles.

After the sensor is manually guided once around the object, distinctive object points are identified in the photo sequence. “If these appear in several images, we can use the principle of triangulation to calculate the associated 3D points and ultimately the 3D data of the entire scene,” Heist said.

The goSCOUT3D resembles an oversize flashlight. A ring light is the most visually striking feature of the new sensor, which also offers a high-resolution color camera, an inertial measurement unit, and a display with touchscreen. Courtesy of Fraunhofer IOF.

To ensure that 2D images are processed quickly, the sensor includes an inertial measuring unit (IMU) to provide measurement data on the position and orientation of the object. “For the 3D acquisition, a large number of high-resolution individual images of good quality is required,” Heist said. “The corresponding processing of these individual images is typically very time-consuming.”

The data yielded by the IMU provides an approximation of the sensor’s movement, so that images with overlapping image content can be selected. “If one puts this prior knowledge into the photogrammetric evaluation, time can be reduced by more than half, especially for complex measurement objects,” researcher Marc Preißler said. With this information, goSCOUT3D can create a 3D model within a few minutes.

The goSCOUT3D sensor is operated manually; the user guides the sensor around the object, and the sensor takes measurements of the object and automatically creates a high-resolution, 3D model that incorporates information on the object’s shape, color, and texture. In addition to the IMU, the goSCOUT3D sensor features a high-resolution color camera and a touchscreen display. The integrated 20-MP color camera enables a high spatial resolution of less than 0.25 mm.

A ring light is also included to illuminate the measurement scene. The ring light enables the short exposure time required to allow over 1000 images to be captured and processed.

An MTU employee digitizes an engine using the goSCOUT3D photogrammetry device. Courtesy of MTU Maintenance.

“At a standard measuring distance of 1 m and an image field of about 1 m², we thus achieve an extraordinarily high recording speed of up to 6 m² of object surface per minute,” Preißler said. The ring light enables short exposure times, which are necessary for hand-held operation of the device.

The sensor head weighs about 1.3 kg. Power is supplied through rechargeable batteries, ensuring flexibility and mobility by enabling the sensor to operate for several hours without interruption.

Image of a turbine with the goSCOUT3D scanner’s trajectory depicted by the blue line. Courtesy of Fraunhofer IOF.

Frank Seidel, head of repair development at MTU Maintenance, said, “goSCOUT3D gives us a holistic and detailed view of our engines in 3D and 2D, including navigation options. The flexible usability of the scanning system in the production environment, the uniform documentation structure when recording the findings data, and its use in our quality and analysis tools will lead to a significant increase in efficiency.”

According to the Fraunhofer team, the potential applications for goSCOUT3D extend beyond the aerospace industry. The sensor-scanner could be valuable in the fields of medicine and scientific research. It could also be used to provide data for augmented reality applications.

The goSCOUT3D sensor-scanner was presented for the first time at OPIE ’23, in Yokohama, Japan, April 19-21. It is also being presented at CONTROL, in Stuttgart, Germany, May 9-12.