Long-line laser scanner speeds complex aircraft cockpit modeling
Direct Dimensions, Inc. (DDI) was recently contacted by a 3D animation company that specializes in aircraft cockpit ergonomics and human factors analysis to create a 3D model of an existing cockpit within a large commercial aircraft. Due to aircraft scheduling constraints, the two engineers who traveled onsite to complete the project had a limited amount of time to complete the scan of the cockpit. They were done in eight hours.
DDI was called in to scan the entire cockpit, providing enough detail to recreate an animation scenario of the controls and pilot movements during a very tight pre-specified time period. Special attention was required in showing the pilots’ positions and range of motion to various controls in order to create an animation and other analyses. The final model was used to make an animated 3D visualization of pilot interaction with the aircraft controls. Arrangements were made so that the specific model aircraft was available for the project.
Specializing in on-site laser scanning and conversion of complex three-dimensional data into 3D computer models, the 13-year-old Baltimore, MD-based company has a strong presence on the East Coast, with businesses shipping parts to them for scanning and modeling from all over the country.
They frequently do onsite projects like the cockpit scan with portable scanning equipment such as Laser Design’s Surveyor FA-Series portable scanner and the SLP-2000 probe with the super-long 8-in. laser line for larger projects.
With customers in virtually every industry including aerospace/military, automotive, general industrial, consumer products, medical, and a strong art and architecture focus, DDI laser scans parts of all sizes from small to very large, and shapes from simple to complex, to use in many applications including reverse engineering, inspection, and design.
Without Laser Design’s long laser line scanning technology, such an undertaking might take several days to accomplish.
In addition to the difficult time constraint for the onsite scanning process, a physical challenge was the tight size of the cockpit. Within these close quarters the DDI engineers needed to set up the LDI laser probe on the Faro arm providing vantage points to the entire cockpit and all the critical controls.
Also, scanning the dark colors and reflective surfaces of the controls was a concern. Some laser probes can have trouble capturing dark or shiny objects. The main control wheel was especially problematic because it was dark and shiny.
Lay public viewers expect to see 3D animations perfectly replicate reality like they see in a courtroom animation or as used on the nightly news. But modeling reality is an inexact science and enormously difficult when dealing with a real-world scene rather than a fictional locale, as in most video games. “This was not as much an engineering project,” says the senior project lead, “as it was a multimedia project, recreating a real-world scene to be used for 3D animation.”
Once the scanning process was completed, the huge data set was to be reverse-engineered into an accurate 3D model of the cockpit so that when it was animated the scene would look very realistic. Fortunately DDI has the data processing software, computers, and expertise to work with the extremely large data sets that were produced from this cockpit scan.
The eight-hour solution
Using the fast and accurate Laser Design SLP-2000 laser, with an extra-long laser line length of up to 12 in. and an 8-ft Platinum Faro articulated arm, the engineers planned and then set up the scan environment in the cockpit. The data collection phase of the project proceeded very efficiently using the SLP-2000 laser, which captured accurate detail and excellent resolution of cockpit controls and features.
Scanning free-form shapes and irregular surfaces, such as those found in a cockpit, is an application especially well suited to a non-contact laser scanner on an articulating arm. Because the scanning system projects a line of laser light onto surfaces while cameras continuously triangulate the changing distance and profile of the laser line as it sweeps along, the problems of missing data on an irregularly shaped surface are minimal. The operator moves the Laser Design SLP-2000 laser line back and forth over the scan area until the entire surface is captured. An operator continuously monitors the capture progress on a computer screen. The system measures details and complex free-form geometry so that the object can be exactly replicated digitally. Laser scanners measure quickly, picking up over 75,000 coordinate points per second, and generate huge numbers of data points to accurately describe the scanned objects without the need for templates or fixtures.
First, since an aircraft cockpit is a relatively confined environment, the setup was somewhat cramped. The portability and the ease of use of the Laser Design SLP-2000 laser on the Faro arm system were essential to completing the project under the severe time restrictions. The Faro arm was positioned in the center-back of the cockpit because the laser could scan most of the geometry from that vantage point. The pilot and co-pilot controls move in unison when either side is being used, so to scan the movements of the pilot’s side of the cockpit without blocking the view, an assistant sat on the co-pilot’s side to work the controls, and vice versa. The movements of the controls, especially the rudder, were paramount to document, and by having one seat empty, the scanner had a clear view of the controls when they were operated from the other cockpit seat. The customer even brought in a representative pilot to be scanned and to work the controls to provide a reference for accurately visualizing the conditions and actions in the cockpit for the animation.
Secondly, although the cockpit was very small for setup and performing a scan, it was a relatively large and detailed space to scan in such a short period of time. The locations of the flight controls (sticks and pedals), the seats, and pilots needed to be accurate within a tight tolerance for the animation to be correct. The DDI engineers had to determine how to gather enough data at the required accuracies in the required locations and do it quickly enough to finish within the time constraints.
With the Laser Design SLP-2000, the engineers initially performed test scans at a high density, processed the data on the laptop computer to check its accuracy and validity, then decided that a lower density would still provide the resolutions required to document the positions of the controls and the pilots and be much quicker. The SLP laser’s extra-long line length gathered thousands of 3D point cloud coordinates at ultra-high speeds. The DDI engineers coordinated the airplane control locations with the hard geometry of the floor and bulkhead to provide the important reference points and ensure the accuracy of the model created from the 3D digital scan data.
Another scanning challenge was the dark colors of the controls. The control wheel was especially problematic because it was dark and also shiny. Laser Design’s SLP laser probe design utilizes CMOS array technology (instead of the older CCD array used in most competitive probes), which allows a wider range of specular surfaces to be scanned.
However, the DDI engineers also decided to use one of their experienced-based special scanning methods, blue painter’s tape, to cover the handle to acquire even better data.
With a scanning strategy in place, the DDI engineers began the series of scans required to cover the entire interior of the cockpit. They set up the various scanning passes, verified the data as they went along, filtered the data at the correct rate for the application, and completed the onsite portion of the job — all in the eight-hour timeframe, an admirable achievement.
The results
After scanning the entire cockpit and returning to their facility in Baltimore, DDI’s engineers used point-cloud processing software to process the massive raw scan files into a highly accurate polygonal model in STL format. By merging all the scan files together, a digital cockpit emerged that was an exact replica of the original aircraft cockpit. From that model, they then created a low-resolution version for use by the customer in 3D Studio Max to produce the animation sequences.
The senior engineer explained, “Success meant knowing where key items were within less than 1/8 in. The customer needed to illustrate the specific positions of controls and objects, but not the fine details.” With the cockpit model, the animators could create a timeline and accurately depict a sequence of events.
“From a scanning perspective, the results we obtained under challenging conditions were very good,” commented the DDI engineer. “We have been called in again by the same customer to document other vehicles digitally, so they have joined Direct Dimensions’ list of satisfied customers.”
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