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Collision Avoidance

DETAILED CASE STUDY: COLLISION AVOIDANCE

Boeing paints each airliner to order so the purchaser can incorporate logos, specified colors or other custom designs.

In the painting hangars, a crew of painters moves along the plane on eight moveable platforms called “stackers,” four on each side of the plane. The stackers hang from rigging in the ceiling, and the painters control their movement.

the-pointPROJECT DETAILS

Client: The Boeing Company

Project duration: About 12 months

Team
Client: 1 engineer
Concept Systems: 2 engineers

Concept Systems’ time on site: About 60 days for first hangar; about 20 days each for two subsequent hangars.

Pain points

  • Took several days to update system before painting could begin on a new plane design.
  • Constrained ability of painters to move, even though there was room.
  • Outdated method of registering the position of the plane was no longer compatible with other upgrades in the hangar.
  • Limited online visualization of the plane and the platforms.

Results

  • A new plane design can be commissioned into the collision avoidance system just once for all three hangars, and the whole process takes much less time than it used to.
  • The system can be updated onsite by Boeing engineers to account for any changes made to painting platforms.
  • A new method for registering the position of the plane is compatible with new hangar configuration.
  • Position of the plane and painters can be viewed as 3-D graphics in real time.

Technology used

  • Rockwell Automation ControlLogix processors
  • Proximity Query Package
  • Open Graphics Library
  • Theodolite
  • Visual C++.NET

The work must go quickly to ensure a quality, uniform paint job. In fact, the entire fuselage is painted in minutes.

But the human-directed movements of the stackers must be constrained to prevent them from ever colliding with the plane — or with each other. A collision can mean time-consuming repairs and possibly having to send the plane back to another hangar to be fixed.

Moreover, the painters, quite skilled in their own right, need to focus on the task at hand. So moving the stackers needs to be easy and safe, and not distract them from their work.

The old system

Boeing had a collision-avoidance system in place, but it was dated. It used a very coarse 3-D virtualization of the plane, essentially constructing it out of two-inch cubes, as if the plane were built from Legos. This blocky modeling of what in reality is a smooth, curved surface occasionally prevented painters from moving the platform exactly where they wanted it, even though there was room.

Additionally, when a new airplane model came into production, it would take several days to update and test the system to accommodate the dimensions of the new plane. Each of the three painting hangars would have to be updated separately. While this work was going on, the hangar was out of service.

Finally, the old system used a series of plates on the floor to find the position of the plane in the building, so the system could register it relative to the painting platforms. While this generally worked well, Boeing was making other changes in the hangar that made the floor-based registration system unworkable.

Boeing hired Concept Systems to figure out a more up-to-date and efficient collision-avoidance solution.

A new solution from existing technologies

Concept Systems developed a system that integrated various existing technologies — both hardware and software.

One of the breakthroughs was finding software developed at the University of North Carolina called the Proximity Query Package (PQP), which can detect approaching collisions between two different computer-generated objects.

“Discovering PQP was a big breakthrough,” said Scott VanDelinder, the principal Concept engineer on the project. “It was funny, because I worked up an adaptation using University of North Carolina’s example, which had graphics of a rabbit and a doughnut, showing how they couldn’t touch each other. Boeing still teases us about that, how we showed them this image of a rabbit. But it allowed them to see instantly how this would work. That was a key moment.”

The PQP engine provides measurements of the nearest points between two models being compared. Boeing provided the data for the aircraft to develop the models. We wrote the software applications to present the models to PQP based on airplane registration and stacker position feedback, and then based on the distance results make the decisions about movement go/no-go. The OpenGL provides a layer of visualization on top of all this to help validate and troubleshoot the system.

Now, information about the exact size and shape of the plane can be exported from Boeing’s design software and then rendered as a 3-D graphic in OpenGL. It similarly renders the stacker platforms for validation and troubleshooting the system.

Adding a theolodite, and putting it all together

To register the exact position of the plane in the hanger, Concept systems employed a surveying instrument called a theodolite. Because the theolodite can be moved around, it first locates fixed points in the hangar to know its own location. Then it finds reflective stickers that have been applied in specified places on the airplane. It then determines the exact position of the plane relative to the hangar and thus to the stacker platforms.

This data, along with the information about the aircraft model and flap positions, etc., are used to create a 3-D computer rendering of the situation in the hanger. Then PQP is used to detect and avoid any approaching collisions between the various objects.

So inputs from the painters, using controls on the stacker platform, are run through a programmable automation controller (PAC), working in conjunction with a supervisory computer, known as a collision avoidance module (CAM). The CAM examines the movement requests and makes precise and complex “decisions” about what movements and speeds are allowable. Platforms can move within four inches of the surface of the plane, but no closer. The stacker platforms move more slowly as they get nearer the plane.

“We like to gather technology that’s available out there, and make it work it together,” VanDelinder said. “You don’t need to recreate the wheel on everything. And that’s what we were able to do in this case.”

The results

Because the virtual representations of the aircraft surfaces are extremely accurate, the problems that had plagued the old system and caused painters to lose time to unexpected movement limitations have been eliminated.

The system also includes a simulator, so that engineers can perform exhaustive testing of a new aircraft model using the full software system in an offline environment. This has cut the time needed to update the system to accommodate a new plane design to one day for all three hangars.

Additionally, technicians and supervisors can view live interaction between any stacker platform and the aircraft in real time. The 3-D objects can be rotated, panned and zoomed.

The system is easier for Boeing to update, as well. Since the original installation, Boeing has occasionally made changes to the stacker platforms, and a Boeing engineer was able to go into the software and make the necessary adjustments — and test them — something he said he never would have been able to do using the old system.