Leveraging Robotics

Battelle's Multi-Use Robotic System provides the Air Force with the capability to automate the inspection, paint removal and re-coating of integral wing fuel tanks.

The Air Force had a problem. B52 airplanes had been functioning for 40 years without any issues with the wing fuel tanks, and then suddenly, around 2002, they began noticing defects in the coatings and paint within the tanks. The problem was potentially devastating: the peeling paint could clog fuel filters and cause engine flameout.

It was quickly determined that the issue was caused by a switch from JP5 jet fuel to JP8 jet fuel, the latter of which contains additives that are detrimental to the paint inside the fuel tank.

At first, discussions centered on the fuel and paint formulations themselves, but soon evolved to how the more than 100 airplanes with the problem would be fixed. The government initially estimated that it would take 8,000 to 10,000 man hours per airplane to strip the paint and repaint each fuel tank with a new formulation. After further investigation, the Air Force narrowed down the project to only a portion of the tank that had the problem, and the estimates fell to 3,000 to 4,000 man hours per airplane. This was still not satisfactory.

Conversations began between the Air Force and Battelle, an independent research and development company specializing in virtually all areas of scientific development.

The discussions led to a program involving a robotic solution to the B52 fuel tank problem. A group was formed at Battelle to develop an autonomous robotic system that would be able to enter the fuel tanks, inspect, strip the paint, and repaint problem areas.

The system is modular in design to enable it to be assembled within an 11" x 17" opening, and weighs less than 30 lb per component.

"For this system to be useful, it had to be modular, so that operators could take it in in pieces, and assemble it quickly in limited light conditions," explains Tim Lastrapes, Program Manager of the Multi-Use Robotic System (MURS) program. "We ran an umbilical cord from our system to an outside computer station that, once the operator sets up the system inside, he then gets back out of the airplane and runs the robotic system from a remote console." The robot is assembled inside the tank, with no tools, in less than 15 minutes. The fact that there are no tools is significant because this leaves little potential for Foreign Object Damage (FOD), which is one of the top safety issues relative to aircraft safety of flight. The MURS includes an industrial robot arm on a carriage that rides back and forth on portable rail segments, which are sized according to necessity depending on the size of the tank to be serviced.

"Once we have the rails set up and the carriage put on it, and the robot hooked on the carriage and set up to its umbilical, the robot goes down and back on the rail to determine how many rails it has, and that gives us an idea how long the tank is," says Darren Krasny, Software Control Lead for the MURS program at Battelle. "Once it does that, it does an initial scan of the wing tank that it's inside." The 3D laser scanner attached to the robot is used for non-destructive inspection (NDI), and to scan the environment into the computer software program so that the robot knows its surroundings at all times.

The robot glides along the rail system while scanning the environment, and the program automatically computes the volume of the tank, enabling the robot to then move autonomously throughout the tank to complete its work. The scanning technology has capability for resolution down to 0.007". This allows the MURS to detect paint peeling off of the walls of the tank, as well as other imperfections in the metal.

"Once we've scanned in the environment and we've adjusted the working volume for the robot to match the scan data, we have all we need for the robot to go from anyplace inside the tank to any other place and do it autonomously without crashing into itself or into the environment," Krasny says. "The operator points and clicks on the screen, and the robot computes its own path." The robotic arm has seven degrees of freedom that are all autonomous; no programming is needed for each individual step. The point-and-click program allows operators less intervention. The robot is also designed to do the inspection, incorporate paint strippers, and spray heads to repaint. Battelle is investing some of its own R&D money into the program to support additional applications for the future. One area of potential is to optimize the software to support general environments as well as outside aircraft locations.

Depending on funding, the group hopes that the technology will be coming to market by the end of 2009.

Battelle
Columbus, OH
battelle.org