Vehicle Vital Signs
Written by Peter Buxbaum
MLF 2010 Volume: 4 Issue: 3 (April)
Onbooard Systems Monitor and Help
Diagnose System Performance and Problems.
U.S. military land, sea and air platforms face deployment for stretches of months at a time. It is important for the armed services to know that any given vehicle, vessel or aircraft is ready for duty in advance of deployment. Similarly, it is advantageous once in theater for commanders to be apprised in advance of potential problems with a platform that may require maintenance.
The armed services deploy, and industry provides, a number of automated diagnostic tools that measure critical functions within these platforms and are able to give the green light for deployment or alert personnel of upcoming problems before they become critical.
These automated tools provide a number of advantages, according to Don Flynn, director of military vehicles at BAE Systems. “They reduce costs by allowing maintenance to be performed before a catastrophic failure occurs,” he said. “It is easier and cheaper to replace an oil filter or a fan belt before you reach system failure.”
Onboard diagnostic tools also help make logistics more efficient and promote higher levels of readiness by allowing maintainers to order parts in advance. “You can track usage and health data so maintainers can have parts ready when vehicles come in for work,” said Flynn. Otherwise, a vehicle would have to be brought back to the maintenance shop if needed parts were not on hand after inspection.
The Electronic Maintenance System (EMS) is an Armyowned system that allows asset maintainers to perform troubleshooting, maintenance and diagnostics. EMS Next Generation is the third version of EMS that has been deployed or will be deployed to dozens of Army, Marine Corps, and joint tactical and combat vehicles. Working with EMS is the Maintainer’s Advanced Diagnostics System, a configuration of software applications that reads sensor values from a variety of sources and uses them to determine the state of an asset.
O’Neil & Associates, a company based in Miamisburg, Ohio, provides software that runs these systems. “Most tactical vehicles have onboard computers for the engine, transmission, anti-lock braking system, and central tire inflation system,” explained Bob Heilman, O’Neil’s president. “Onboard computers are controllers whose primary function is to broadcast information about what is going on in that controller to the vehicle’s onboard network. Our software collects and interprets that data and communicates it to the other systems.”
O’Neil’s software resides on the maintenance support device, which is separate from the onboard computers, or on the computer themselves. The software gathers information from the onboard system and is able to detect faults, such as decreasing oil pressure or high differential pressure on fuel filters, and to communicate those to Army systems. The Army systems can run prognostics for the problem detected and, if appropriate, generate a work order to fix the unit before it breaks.
The Army is in the process of releasing a capability that will allow data from onboard computers to be wirelessly communicated to a maintenance computer.
The O’Neil software can also perform tests on systems that are more intrusive than merely reading data. “The software can tell the computer controlling the engine to shut off the fuel injector,” for example, in order to isolate a problem, said Heilman.
BAE Systems offers a product for use on military vehicles called the NeuralNostics Fleet Manager, which was originally developed for commercial vehicles. NeuralNostics is software that runs statistics-based algorithms and is applicable to any military ground vehicle, according to Flynn. The BAE product also gathers data from various onboard sources and interprets them.
“If a parameter is drifting from where it should be, the operator can be informed to take action,” said Flynn, “or the system can be interrogated when the vehicle comes back to the motor pool and the fleet manager can look at an anomalies report that the system generates.”
NeuralNostics is a self-learning system that generates a baseline for a vehicle, depending on its operating conditions, through an analysis of the statistics available through the onboard computers. “The vehicle manufacturer may say that 10 to 40 pounds per square inch is the normal range for oil pressure,” Flynn explained. “But for vehicles running at high RPMs in a hot environment, the system may determine that 20 to 25 psi is the correct range. If the oil pressure starts to fall below that range, the system will send that information to the operator or the maintainer so they can look into whether the oil pump needs to be changed.”
Alerts are sent to operators through onboard displays. Fleet managers can access the tool through an internet connection. The system has been demonstrated on three United Kingdom military ground platforms but not yet fielded in a military setting. Flynn said the value of the system in preemptively detecting upcoming problems can be demonstrated in as little as two days.
The U.S. Navy uses a patented technology called SWAN (stress wave analysis) on its Landing Craft Air Cushion (LCAC) class hovercraft and to determine the pre-deployment readiness of those vessels. The technology, provided by Curtiss-Wright Controls in Santa Clarita, Calif., is hooked up to the component to be tested—in this case, rightangle gear boxes—and the LCAC is run at high speed for about five minutes. The Navy determined that the gear boxes were the key component of the craft that needed to be checked before deployment.
“This test measures the health of the gear boxes,” said Curtis Reichenfeld, the company’s chief technical officer. “It gives the green light to deploy. These boats go out for six to eight months at a time. They don’t want it to fail during operation.”
SWAN is acoustic-based, as opposed to a vibration-based system. “The biggest thing about being acoustic-based is that it is blind to normal vehicle vibration,” said Reichenfeld.
The system detects structure born sound through a series of sensors and processes it with artificial software. "This provides an actual measurement of the true condition of equipment,” said Reichenfeld. “It allows for proactive asset management rather than reactive management by detecting and monitoring machine degradation long before vibration or other technologies.”
The acoustic, spark plug-sized sensor is tuned to the high frequency 30 KHz to 40 KHz range. “It is listening for acoustic emissions characteristic of metal on metal contact,” said Reichenfeld. “We measure and filter acoustic emissions to remove any vibration content. We can actually get down to the particular bearing or gear having an issue.”
The end result is a stress wave energy measurement that is correlated to a red, yellow or green health status. Green means the LCAC is ready to go; yellow or red means the system has detected abnormal levels of friction.
In the case of the LCAC, SWAN is used as a portable system that is installed when the craft undergoes the operational test runs. Like other diagnostic systems, it can also be permanently installed on a platform for constant monitoring.
The original military application for which the SWAN diagnostic system was developed is the U.S. Army, and it was intended for application to helicopter drive train components. The hardware and operating system software are readily adaptable to numerous other applications, noted Reichenfeld.
“On radar systems, it is able to measure increases in friction as the antenna rotates,” he said. “It can also be installed on anything having to do with generators, engines and pumps.” In the case of one industrial application, at a power generation plant, sensors communicate wirelessly to a central computer that processes the data, determines the health status and provides a display of the results.
Curtiss-Wright will be demonstrating SWAN for electro-mechanical actuators onboard Air Force aircraft, and is looking to expand its application to ground vehicles and unmanned aerial vehicles as well. ♦