Ever wonder whether a diesel engine can be used to power a helicopter? Or if you can safely attach a 1-ton spray pod to a passenger turboprop plane with a cruising speed of 284 mph?
These are not the typical subjects of aviation feasibility studies, but they are practically meat-and-potatoes for Embry-Riddle Aeronautical University’s Applied Engineering Research Center (AERC) in Daytona Beach, FL.
The central tools in AERC’s explorations are Faro’s Platinum ScanArm and Geomagic Studio digital reconstruction software. The combination of Faro hardware and Geomagic software enables digital shape sampling and processing (DSSP), which describes the ability to traverse physical and digital worlds. AERC takes advantage of DSSP to create accurate digital replicas of assemblies and parts for which there is no CAD data, and then test them in the virtual world.
The spray pod project is AERC’s latest, and an example of the kind of challenges the testing lab routinely takes on.
A county agency approached AERC to develop a removable spray pod tank that could be attached to a King Air C90, a twin-turboprop plane produced by Beech Aircraft. The King Air has been in continuous production since 1964, but it is most often used for hauling passengers, not carrying a spray tank that weighs about 2000 lb when fully loaded with insecticide.
AERC purchased the Faro Platinum ScanArm in 2006 and teamed it with Geomagic Studio software to collect, process, store, and analyze 3-D data in digital form. The first project was the successful adaptation of a diesel engine for a small helicopter.
Before that, AERC had used a Faro Gold Arm with a hard-probe. It increased accuracy and saved time over the old methods—measuring by hand and marking points
with tape measures and T-squares—but there were still difficulties turning the point data from the Gold Arm into accurate surfaces within CATIA CAD/CAM software.
With the Faro Platinum ScanArm, AERC has the ability to collect 19,000 points per second with accuracy within hundredths of an inch. The ScanArm is fully integrated with Geomagic Studio, which provides patented processes for quickly converting point-cloud data into polygons and accurate surfaces.
According to Stephen Roth, Associate Director of AERC, no training was necessary with Geomagic.
For the spray pod project, AERC scanned the King Air inside and out, since the addition of the spray pod requires reinforcing the inner structure of the fuselage. The plane was also jacked up so the underside could be captured by the scanner. AERC had to plan for two opposing requirements: scanning large areas where very little detail is needed, and capturing areas where precise measurements within hundredths of an inch are needed for features such as rivet heads.
“This was our first large-scale project with the laser scanner,” said Roth. “One of the biggest challenges was determining the most efficient ways to capture the varying level of detail we needed from different parts of the fuselage.”
Multiple scans were used to capture the geometry of the King Air fuselage inside and out, in both relatively flat and highly curved areas, and in little and great detail. The scans were imported into Geomagic Studio, where they were automatically registered to closely fit one another. The scans were then merged and a polygon model of the fuselage was created. Geomagic Studio also enabled AERC to fine-tune the model, removing noisy data, filling holes, sharpening edges, and performing other edits.
Using a logical, step-by-step work flow in Geomagic, AERC engineers converted the polygon model into a NURBS surface model. First, regions were defined by unique colors separated by red boundary lines. Contour lines were extracted from the regions and used to create individual panels within the model. The panels were then used to create and refine a patch layout, to which grids were applied and the resolution of the NURBS surfaces determined.
Once the NURBS surface model was created, the transformation from physical to digital was complete, and the model was ready for importing into CATIA.
“The process was simple and automated,” said Monica Londono, a design engineer who was part of the project. “Geomagic gave us a true surface representation of the fuselage that we could seamlessly import into CATIA to use for designing the spray tank.”
The model created in Geomagic was used in CATIA to help create the optimal design for the spray tank, and to determine the best way to connect the spray tank to the fuselage. The completed tank model, connected to the fuselage, was loaded into CATIA FEA software to simulate loading and conduct structural analysis. When the spray tank design was completed to AERC’s satisfaction, it was sent out for CNC milling. The resulting physical prototype of the spray tank was an excellent match for the fuselage, according to Roth.
At this point, the tank has been built, mated to the King Air, and is currently undergoing testing by the FAA. Further verification will be provided by Geomagic Qualify computer-aided inspection software, which AERC will use to compare the manufactured spray pod to the CAD model to ensure that design integrity is kept intact.
“It’s hard to quantify exactly how much time we’ve saved and how much we’ve increased modeling accuracy with Faro and Geomagic,” said Roth. “[However], there have been major improvements in both areas.”
Bob Cramblitt, Cramblitt & Co., wrote this article for Aerospace Engineering.