New Wireless Bridge Sensors Powered By Passing Traffic

Source:

http://www.sciencedaily.com/releases/2007/10/071019175317.htm

ScienceDaily (Oct. 22, 2007) — Clarkson University researchers have developed technology that uses the vibrations caused by passing traffic to power wireless bridge monitoring sensors.

Wireless battery-powered sensors that monitor bridges and report changes that may lead to failure are easy to install, but it is unwieldy to provide power for the sensors. Each bridge needs at least several sensors, many installed in hard-to-access locations. Replacing millions of batteries could become a problem, adding to the expense of maintaining the bridges. The Clarkson researchers have found a way around this problem.
"We have completely eliminated the battery from the equation," says Assistant Professor Edward S. Sazonov, who developed the technology along with Professor Pragasen Pillay. "Hermetically sealed wireless sensors powered by bridge vibration can remain on the bridge without need of maintenance for decades, providing continuous monitoring of such parameters as ice conditions, traffic flows and health status."
The two electrical and computer engineering professors, along with graduate students Darrell Curry and Haodong Li, used the New York State Route 11 bridge, a steel girder structure, which runs over the Raquette River in Potsdam, N.Y., as a case study.
Energy was harvested by locating an electromagnetic generator on a girder. The harvester responded to one of the natural vibration frequencies of the bridge. Each time a car or a truck passed over the bridge, even in a different lane from the sensor installation, the whole structure vibrated and excited the mover in the generator, producing electrical energy. Harvested electrical energy powered unique wireless sensors that increased energy output of the harvester and consumed only microwatts of power while performing useful tasks.
Sazonov and Pillay have been invited to present their work at the Transportation Research Board of the National Academies Meeting in Washington, D.C., in January. The board provides support for their research.
They are also working on using the energy harvesting technology to power the various sensors in passenger cars.
Wireless monitoring of bridges and overpasses has gained much attention in the past few years. Bridge collapses happen suddenly and unpredictably, often leading to tragic loss of human life. In 2006, the Federal Highway Administration listed 25.8 percent of the nation\'s 596,842 bridges as either structurally deficient or functionally obsolete. While many of these bridges will remain in service for years, they need monitoring and rehabilitation. Currently, bridge monitoring is performed through periodic visual inspections. In the tragic example of I-35W Mississippi River bridge collapse, the bridge passed a visual inspection a year prior to failure.
Adapted from materials provided by Clarkson University.

Fausto Intilla

www.oloscience.com

Hydrogen Storage Model Speeds Development Of Alternative Fuel Vehicles

Source:

http://www.sciencedaily.com/releases/2007/10/071003100601.htm

Science Daily — Researchers at the UCLA Henry Samueli School of Engineering and Applied Science have developed a model that could help engineers and scientists speed up the development of hydrogen-fueled vehicles by identifying promising hydrogen-storage materials and predicting favored thermodynamic chemical reactions through which hydrogen can be reversibly stored and extracted.
Because of global environmental changes associated with man-made carbon dioxide emissions and the limited resources of fossil fuels, developing alternate and renewable energy sources is important for a sustainable future. Hydrogen is a potential source of clean energy for future use in passenger vehicles powered by cheap and energy-efficient fuel cells, but its widespread adoption has been hindered by the need to store it on-board at very high densities.
A promising solution to this problem involves storing hydrogen within a material in the form of a chemically bound hydride, for example lithium hydride (LiH). Unfortunately, simple binary hydrides, in which hydrogen combines with light elements such as lithium, sodium, magnesium or others, do not adequately satisfy the requirements for on-board storage, as the hydrogen-yielding reaction requires heating the material to impractically high temperatures.
Because of this, researchers have turned to multicomponent hydride mixtures with higher volumetric and gravimetric densities, better operating temperatures and improved reaction rates for practical hydrogen storage. However, this flexibility comes at the price of drastically increased complexity associated with the large number of competing reactions and possible end-products other than hydrogen.
Thus, predicting desirable hydrogen storage with multicomponent mixtures has proved difficult. For example, the recently studied lithium hydride compound Li4BN3H10 was found to have as many as 17 hydrogen-release reactions, of which only three were found to be feasible — and none were in the desired range of temperatures and hydrogen pressures for practical on-board storage in hydrogen-powered vehicles.
The research team used modern quantum mechanical theories and high-powered computers to develop an algorithm that can automatically and systematically pinpoint phases and reactions that have the most favored thermodynamic properties — that is, those that can release hydrogen at ambient temperatures using the waste heat from a proton exchange membrane (PEM) fuel cell. The team tested the method on the well-studied Lithium-Magnesium-Nitrogen-Hydrogen system, predicting all experimentally observed pathways in the system. The researchers say this method can also be applied to other multicomponent hydrogen systems.
The new method, published in Advanced Materials, was developed by Alireza Akbarzadeh, a UCLA postdoctoral researcher in the department of materials science and engineering; Vidvuds Ozolins, UCLA associate professor of materials science and engineering; and Christopher Wolverton, professor of materials science and engineering at Northwestern University in Illinois.
"The development of an algorithm that goes beyond chemical intuition and finds all hydrogen storage reactions 'in silico' is crucial and will help the scientific and engineering community to develop revolutionary new hydrogen-storage materials," Akbarzadeh said. "This is a major achievement in the field, which can boost up the search for the best reversible solid-state hydrogen storage."
"We are steadily approaching the moment when we will be able to theoretically design materials with desired properties, just like a tailor makes a suit to fit the customer's needs," Ozolins said. "This will bring in a qualitatively new era of collaboration between theory and computation, experiment and technology development."
The research was funded by grants from the U.S. Department of Energy.
Note: This story has been adapted from material provided by University of California, Los Angeles.

Fausto Intilla
www.oloscience.com

Nanotubes Can Detect And Repair Cracks In Aircraft Wings, Other Structures

Source:

http://www.sciencedaily.com/releases/2007/09/070927132550.htm

Science Daily — Adding even a small amount of carbon nanotubes can go a long way toward enhancing the strength, integrity, and safety of plastic materials widely used in engineering applications, according to a new study.

Researchers at Rensselaer Polytechnic Institute have developed a simple new technique for identifying and repairing small, potentially dangerous cracks in high-performance aircraft wings and many other structures made from polymer composites.
By infusing a polymer with electrically conductive carbon nanotubes, and then monitoring the structure’s electrical resistance, the researchers were able to pinpoint the location and length of a stress-induced crack in a composite structure. Once a crack is located, engineers can then send a short electrical charge to the area in order to heat up the carbon nanotubes and in turn melt an embedded healing agent that will flow into and seal the crack with a 70 percent recovery in strength.
Real-time detection and repair of fatigue-induced damage will greatly enhance the performance, reliability, and safety of structural components in a variety of engineering systems, according to principal investigator Nikhil A. Koratkar, an associate professor in Rensselaer’s Department of Mechanical, Aerospace and Nuclear Engineering.
Details of the project are outlined in the paper “In situ health monitoring and repair in composites using carbon nanotube additives,” which was published online this week by Applied Physics Letters. Rensselaer graduate students Wei Zhang and Varun Sakalkar were co-authors of the paper. The team has been working on the project for more than 18 months.
The majority of failures in any engineered structure are generally due to fatigue-induced microcracks that spread to dangerous proportions and eventually jeopardize the structure’s integrity, Koratkar said. His research is looking to solve this problem with an elegant solution that allows for real-time diagnostics and no additional or expensive equipment.
Koratkar’s team made a structure from common epoxy, the kind used to make everything from the lightweight frames of fighter jet wings to countless devices and components used in manufacturing and industry, but added enough multi-walled carbon nanotubes to comprise 1 percent of the structure’s total weight. The team mechanically mixed the liquid epoxy to ensure the carbon nanotubes were properly dispersed throughout the structure as it dried in a mold.
The researchers also introduced into the structure a series of wires in the form of a grid, which can be used to measure electrical resistance and also apply control voltages to the structure.
By sending a small amount of electricity through the carbon nanotubes, the research team was able to measure the electrical resistance between any two points on the wire grid. They then created a tiny crack in the structure, and measured the electrical resistance between the two nearest grid points. Because the electrical current now had to travel around the crack to get from one point to another, the electrical resistance – the difficulty electricity faces when moving from one place to the next – increased. The longer the crack grew, the higher the electrical resistance between the two points increased.
Koratkar is confident this method will be just as effective with much larger structures. Since the nanotubes are ubiquitous through the structure, this technique can be used to monitor any portion of the structure by performing simple resistance measurements without the need to mount external sensors or sophisticated electronics.
“The beauty of this method is that the carbon nanotubes are everywhere. The sensors are actually an integral part of the structure, which allows you to monitor any part of the structure,” Koratkar said. “We’ve shown that nanoscale science, if applied creatively, can really make a difference in large-scale engineering and structures.”
Koratkar said the new crack detection method should eventually be more cost effective and more convenient than ultrasonic sensors commonly used today. His sensor system can also be used in real time as a device or component is in use, whereas the sonic sensors are external units that require a great deal of time to scan the entire surface area of a stationary structure.
Plus, Koratkar’s system features a built-in repair kit.
When a crack is detected, Koratkar can increase the voltage going through the carbon nanotubes at a particular point in the grid. This extra voltage creates heat, which in turn melts a commercially available healing agent that was mixed into the epoxy. The melted healing agent flows into the crack and cools down, effectively curing the crack. Koratkar shows that these mended structures are about 70 percent as strong as the original, uncracked structure – strong enough to prevent a complete, or catastrophic, structural failure. This method is an effective way to combat both microcracks, as well as a less-common form of structural damage called delamination.
“What’s novel about this application is that we’re using carbon nanotubes not just to detect the crack, but also to heal the crack,” he said. “We use the nanotubes to create localized heat, which melts the healing agent, and that’s what cures the crack.”
Koratkar said he envisions the new system for detecting cracks to eventually be integrated into the built-in computer system of a fighter jet or large piece of equipment. The system will allow the operator to monitor a structure’s integrity in real time, and any microcracks or delamination will become obvious by provoking a change in electrical resistance at some point in the structure.
The system should help increase the lifetime, safety, and cost effectiveness of polymer structures, which are commonly used in place of metal when weight is a factor, Koratkar said. There is also evidence that carbon nanotubes play a passive role in suppressing the rate at which microcracks grow in polymeric structures, which is the subject of a paper Koratkar expects to publish in the near future.
The research is team is now working to optimize the system, scale it up to larger structures, and develop new information technology to better collect and analyze the electrical resistance data created from the embedded grid and embedded carbon nanotubes.
The ongoing research project is funded in part by the National Science Foundation and the U.S. Army.
Note: This story has been adapted from material provided by Rensselaer Polytechnic Institute.

Fausto Intilla

www.oloscience.com

New Material For Aircraft Wings Could Save Billions

Source:

http://www.sciencedaily.com/releases/2007/09/070926094727.htm

Science Daily — Building aircraft wings with a special aluminium fibre combination makes them nearly immune to metal fatigue. The application of this technology, partly developed at Delft University of Technology, will lead to substantial savings.

The unusual qualities of this special material (called CentrAl, an abbreviation of Central Reinforced Aluminium) can make a significant contribution to the development of truly energy-efficient, 'green' aircraft. Lower fuel consumption and reduction of maintenance costs could lead to worldwide savings as high as $100 billion.
Fatigue is a phenomenon that affects materials after long-term exposure to cyclic loading. As a result of varying loads, fractures eventually occur. The new, high-quality CentrAl aluminium constructions are stronger than the carbon fibre reinforced plastic (CFRP) constructions that have recently been used in aircraft wings such as the Boeing 787. By using CentrAl wing constructions, the weight can be reduced by another 20 per cent compared to CFRP constructions. Furthermore, using CentrAl results in considerably lower manufacturing and maintenance costs.
The CentrAl concept comprises a central layer of fibre metal laminate (FML), sandwiched between one or more thick layers of high-quality aluminium. This creates a robust construction material which is not only exceptionally strong, but also insensitive to fatigue. The CentrAl technique allows for simple repairs to be carried out immediately, as is the case in aluminium constructions, -- but not the case when using CFRP constructions.
This patented new concept is one of the results of an intensive collaboration between the company GTM Advanced Structures, founded in The Hague in 2004 and specialising in new aircraft materials and constructions, the American aluminium company Alcoa, and the Faculty of Aerospace Engineering of Delft University of Technology.
During a conference in Delft (Conference on Damage Tolerance of Aircraft Structures: 25-28 September 2007), GTM and Alcoa have presented the new concept to international experts in the field of metal fatigue and damage sensitivity of aircraft constructions. The US Air Force, Alcoa and GTM will also shed new light on the fact that the new CentrAl materials create possibilities for so-called 'Carefree structures'.
These are aircraft constructions that are less sensitive to damage caused, for example, by fatigue, hail storms, other weather phenomena, trucks that collide with the aircraft and corrosion. Carefree aircraft constructions will be characterised by significantly reduced maintenance costs.
Note: This story has been adapted from a news release issued by Delft University of Technology.

Fausto Intilla

www.oloscience.com

Bridge Strengthening Research

Source:

http://www.sciencedaily.com/releases/2007/09/070914163132.htm

Science Daily — These days, a drive across a bridge is not always a pleasure cruise. Mindful of the war on terrorism, it can often be a cautious experience.

In one scenario, someone sets off a series of bombs to weaken the cables and the key structural connections of a major city bridge, all during rush hour. Not easy to do, but now thinkable. This summer, the possibility of sabotage was quickly examined—then dismissed—when the I35W bridge in Minneapolis tragically collapsed into the Mississippi River.
As authorities monitor and stand guard over bridges, the Homeland Security Science & Technology Directorate is looking to scientists and engineers for the security technologies of tomorrow. What if, for instance, we could one day not only guard bridges but fortify them? Like Superman’s blue suit, what if the cables and connections on bridges could be shielded with protective sleeves or covers, making them nearly impossible for the villains to penetrate?
This is the goal of the Directorate's bridge-strengthening research. Through a partnership with the U.S. Army Corps of Engineers’ Engineer Research and Development Center, the Directorate’s Infrastructure and Geophysical Division is testing current bridge designs and investigating advances in steel and reinforced concrete to explore whether such shields could work.
The first step is to determine which bridges and materials are most vulnerable, says Stanley Woodson, who oversees the project at the Center’s Geotech and Structures Lab. A major focus, he says, are the cables and the support columns—or towers—that are used in the cable-stayed design of bridges. Unlike the cables of a suspension bridge, which are attached from tower to tower, the cables in a cable-stayed bridge are connected directly to accessible points along the horizontal bridge deck.
"In controlled experiments, Woodson’s team has been re-creating the forces holding up these bridges and blowing up samples of their cables using various kinds of explosives," say Dr. Mary Ellen Hynes, director of the research. "They then use sophisticated software to analyze the impact and results."
“We tension the cables just like a real bridge,” Woodson explains. “We want to see just how they’d react in an actual terrorist event.”
The next step will be more complicated, says Woodson: Determining what material would suffice for another layer of protection, and what form it should take. “We’re looking at the practical as well as the innovative,” he says, recognizing the potential for high costs.
By the end of 2008, Woodson and his team will be imitating concrete bridge towers and subjecting them to the same explosive testing.
Note: This story has been adapted from a news release issued by Department of Homeland Security.

Fausto Intilla

www.oloscience.com

Skyray 48 Takes Flight

Source:

http://www.sciencedaily.com/releases/2007/09/070919174711.htm

Science Daily — Calm excitement filled the ground control station. Engineers stared intently at their computer screens as the pilot, sitting next to them, flexed his fingers on the controls. Ground crew tending the aircraft finished putting away their equipment. Preparations for the first flight of the unmanned X-48B Blended Wing Body research aircraft were complete.

Years of research, design, construction, wind tunnel and ground tests coalesced into this one moment of time.
Radios crackled. "Tower, Skyray 48 in position, lakebed runway 23, request clearance for takeoff..."
"Skyray 48 roger, main base winds 220 at 6, report airborne, lakebed 23..."
"Wilco"
"Five, four, three, two, one, brakes..."
Quickly, the manta ray-shaped aircraft rolled down the dry lakebed runway trailing a plume of dust as it picked up speed, its three small jet engines whining.
With an excitement that only comes with an aircraft's first flight, the triangular red, white and blue X-48B leapt into the air, obviously wanting to fly.
"Skyray 48's airborne," Boeing pilot Norm Howell called, matter-of-factly. And with that, years of toil blossomed into the sweet fruit of success on July 20, 2007 at NASA's Dryden Flight Research Center on Edwards AFB, Calif.
One of the latest cutting-edge experimental aircraft, or X-Planes, the X-48B BWB is a collaborative effort of the Boeing Co., NASA's Fundamental Aeronautics Program, and the Air Force Research Laboratory. The 21-foot wingspan, 500-pound, remotely piloted plane is designed to demonstrate the viability of the blended wing shape. And demonstrate it has.
After completion of six flights, the X-48B team began a four-week maintenance and modification period during which removable leading edges with extended slats are being replaced with slatless leading edges in order to mimic a slats-retracted configuration. The change requires a software update to the flight control software. In addition, the team is removing and replacing all of the aircraft's flight control actuators for maintenance purposes.
NASA is interested in the potential benefits of the aircraft - increased volume for carrying capacity, efficient aerodynamics for reduced fuel burn, and, possibly, significant reductions in noise due to propulsion integration options. In these initial flights, the principal focus is to validate prior research on the aerodynamic performance and controllability of the shape, including comparisons of flight test data with the extensive database gathered in the wind tunnels at NASA's Langley Research Center in Virginia.
The Subsonic Fixed-Wing Project, part of NASA's Fundamental Aeronautics Program, has long supported the development of the blended wing body concept. It has participated in numerous collaborations with Boeing, as well as several wind tunnel tests for different speed regimes. The team is focused on researching the low-speed characteristics of the design and expanding its flight envelope beyond the limits of current capabilities.
In addition to hosting the X-48B flight test and research activities, NASA Dryden is providing engineering and technical support -- expertise garnered from years of operating cutting-edge air vehicles. NASA assists with the hardware and software validation and verification process, the integration and testing of the aircraft systems, and the pilot's ground control station. NASA's range group provides critical telemetry and command and control communications during the flight, while the flight operations group provides a T-34 chase aircraft and essential flight scheduling. Photo and video support complete the effort.
The composite-skinned, 8.5 percent scale vehicle can to fly up to 10,000 feet and 120 knots in its low-speed configuration. The aircraft is flown remotely from a ground control station by a pilot using conventional aircraft controls and instrumentation, while looking at a monitor fed by a forward-looking camera on the aircraft.
Up to 25 flights are planned to gather data in these low-speed flight regimes. Then, the X-48B may be used to test the aircraft's low-noise and handling characteristics at transonic speeds.
Two X-48B research vehicles were built by Cranfield Aerospace Ltd., in England, in accordance with Boeing specifications. The vehicle that flew on July 20, known as Ship 2, was also used for ground and taxi testing. Ship 1, a duplicate, was used for the wind tunnel tests. Ship 1 is available for use as a backup during the flight test program.
So far, so good as the Skyray 48 team works through the late summer heat of the Mojave Desert as they continue blazing a trail with this futuristic aircraft design.
Note: This story has been adapted from a news release issued by National Aeronautics And Space Administration.

Fausto Intilla

www.oloscience.com

Safer Car Controls

Source:

http://www.sciencedaily.com/releases/2007/09/070909215312.htm

Science Daily — The number of electronic components in cars is growing rapidly. To ensure that vehicle electronics will work properly in future despite the overabundance of software and its increasing complexity, researchers are remodeling it and making it even safer.

The sight of a shiny new car suggests streamlined high-tech devices. But appearances are deceptive. Under the hood, all is confusion. Around 100 microprocessors control auxiliary functions such as ABS, ESP or the headlight that can shine around corners. Almost as many control units send their commands to fuel injection systems, airbags and other functional modules.
Components from numerous manufacturers are scattered throughout the car body. Vehicle development engineers attempting to unite all the different systems into a working entity face a truly Herculean task, for each control unit carries its own software. Experts expect the volume of software in new cars to continue to increase by as much as 300 percent in the next four years.
The Fraunhofer Institute for Software and Systems Engineering ISST in Berlin has joined the international development initiative AUTOSAR (Automotive Open System Architecture) on behalf of the BMW Group. All the well-known car manufacturers and suppliers are members of the partnership. The goal of AUTOSAR is to pare down the ballast of in-car software and make it easier to handle.
The idea behind it is that vehicle functions will first be defined and linked together independently of their specific platforms. Only at the next stage are these functions to be assigned to the vehicle’s existing control units. After this the infrastructural software, likewise standardized, needs to be “fine-tuned”. However, the actual information processing takes place at a higher level, on the AUTOSAR Virtual Functional Bus. This approach simplifies matters tremendously and reveals a way of structuring the growing confusion of software.
“At long last, AUTOSAR gives software integrators in the automotive industry something that developers in other sectors, in the form of standardized development libraries, have had at their fingertips for decades,” says Markus Hardt, head of the department for reliable technical systems at the ISST. But before AUTOSAR can take to the road in tomorrow’s cars, it has to be tested to ensure it functions in a stable manner.
To enable this, Markus Hardt and his colleagues are developing the “aXBench”, a test platform that simulates the AUTOSAR architecture’s mode of operation and suggests an optimal distribution of functions. The “aXBench” enables the scientists to imitate and evaluate the correct functioning of control units, the swift transmission of data between the middleware and the receiver, and even true-to-life details such as hardware and software response times.
Note: This story has been adapted from a news release issued by Fraunhofer-Gesellschaft.

Fausto Intilla

www.oloscience.com

Student Hopes To Break Human Land Speed Record Using Bullet Shaped Bicycle

Source:

http://www.sciencedaily.com/releases/2007/08/070829191414.htm

Science Daily — This October, Jerrod Bouchard will attempt to become the fastest college student to be propelled by his or her own power.

Bouchard, a senior in mechanical engineering at the University of Missouri-Rolla, will try to break the collegiate human-powered land speed record of 61.5 mph Oct 1-6 in Battle Mountain, Nev.
Seated in a bullet-shaped bicycle, Bouchard will be pedaling down a remote highway in Battle Mountain that is said to be one of the straightest, fastest and smoothest surfaces in the world.
Like a NASCAR driver, Bouchard is working with a talented crew to make sure his vehicle is sound. Members of the team include aerodynamics designer Andrew Sourk, a senior in aerospace engineering from St. Joseph, Mo.; team leader Craig George, a senior in electrical engineering from St. Joseph; and composite specialist Matt Brown, a senior in mechanical engineering from Rolla. Bouchard, who is from Camdenton, Mo., is the chief engineer.
Bouchard, Sourk, George and Brown are all members of UMR’s Human-Powered Vehicle Team, which won East Coast and West Coast championships in collegiate human-powered racing last spring. The Battle Mountain endeavor is a separate challenge that was born out of the larger team’s success.
Human-powered vehicles are recumbent bicycles with aerodynamic shells. All summer, the four-man UMR team has been designing and building a new vehicle for the record-breaking attempt. Recently, Bouchard and his crew took the new bike to the Massachusetts Institute of Technology, where they tested it in a wind tunnel. They are also planning to test it at Gateway International Raceway in St. Louis.
Battle Mountain has been the site of many record-breaking performances by professional, collegiate and amateur riders. The records are sanctioned by the International Human-Powered Vehicle Racing Association.
“Our forecasted performance is looking extremely optimistic,” Bouchard says, “and we are confident that we will break the current record.”
Note: This story has been adapted from a news release issued by University of Missouri-Rolla.

Fausto Intilla

www.oloscience.com

Drive-by-wire And Human Behavior Systems Key To New Urban Challenge Vehicle

Source:

http://www.sciencedaily.com/releases/2007/08/070810194840.htm

Science Daily — Virginia Tech's entry in DARPA's Urban Challenge is moving forward to the qualifying rounds, thanks in part to a custom-designed drive-by-wire control system and unique navigation software that makes the vehicle's driving decisions almost human."VictorTango," a team of Virginia Tech engineering and geography students, is among 36 semi-finalists selected by DARPA (Defense Advanced Research Projects Agency) to vie for the $2 million Urban Challenge prize. Qualifying rounds begin Oct. 26 at the former George Air Force Base in Victorville, Calif., and the final event will take place Nov. 3.

Urban Challenge teams are attempting to develop vehicles that can maneuver a 60-mile course of simulated military supply missions in less than six hours -- with no human intervention allowed past the starting line. The vehicles will have to obey California traffic laws, merge into moving traffic, navigate traffic circles, negotiate intersections, and avoid a variety of obstacles.VictorTango has converted two Escape hybrids donated by Ford Motor Co. into autonomous vehicles by outfitting them with a "drive-by-wire" system, a powerful computer system, laser scanners, cameras, and a GPS (global positioning system), said Patrick Currier, a mechanical engineering (ME) graduate student. The students dubbed the vehicles "Odin" after the chief god in Norse mythology."The drive-by-wire system allows the computers to control the throttle, brake, steering, and shifting and to drive the vehicle," Currier said. "This system was custom developed by the team and is unique in that it is completely hidden from view, enabling Odin to retain full passenger capabilities." TORC Technologies LLC, a company in Virginia Tech's Corporate Research Center founded by alumni of the university's robotics program, has worked with VictorTango to develop the software for the vehicle's computer system. VictorTango and TORC developed Odin's sophisticated navigational software, which is modeled on human behavior. "To successfully navigate in an urban environment, Odin processes all of the sensor information, classifies the situation, and then chooses a behavior, such as passing another vehicle, staying in the lane, or parking," Currier explained. This "human-like" system makes Odin capable of choosing the best course out of millions of possible courses, he said.The team has outfitted Odin with four computers that perform specialized sensor processing and hardware interface tasks and two powerful servers that provide the primary computing power. Three laser scanners mounted on the vehicle's bumpers can scan a combined 360-degree field of view 12.5 times per second to detect obstacles. "These scanners are capable of detecting and tracking cars at a distance of up to 100 meters and are Odin's primary method of detecting other vehicles," Currier said.Four more laser scanners are mounted on Odin's roof rack -- two to detect small obstacles such as curbs and potholes and two to check the vehicle's blind spots when it changes lanes or merges into traffic.Two cameras mounted on the roof rack serve two purposes -- they enable Odin to sense its location and identify its proper position in the traffic lane, and can also positively determine if an obstacle detected by the scanners is another vehicle.Odin's GPS has been coupled with an inertial measurement unit and wheel speed sensors to measure movement in all directions. "This system provides Odin with accurate position, even if the GPS signal is temporarily lost," Currier said."Odin is now capable of driving on a marked road, following moving traffic, passing stopped vehicles, handling four-way intersections, and performing three-point turns," Currier said. The vehicle is being fine-tuned so that it can merge with moving traffic, pass moving vehicles, and park. Currier is one of 10 graduate students on the Virginia Tech team, which also has included as many as 50 undergraduates. The students are guided by four faculty advisers, three of them from Virginia Tech -- professor Alfred Wicks and assistant professor Dennis Hong of the College of Engineering's ME department, and geography department chair Bill Carstensen of the College of Natural Resources. The team's founding adviser, Charles Reinholtz, a former Virginia Tech Alumni Distinguished Professor of ME and engineering education and now the chair of ME at Embry-Riddle Aeronautical University in Florida, continues to work with VictorTango. In October 2006 VictorTango was one of only 11 "track A" teams chosen to receive $1 million contracts to develop autonomous vehicles capable of conducting simulated military supply missions in an urban setting. In all, 89 teams from universities and industry entered the competition in 2006. In addition to the $1 million from DARPA and the two Escapes from Ford, the Virginia Tech team received a $100,000 grant from Caterpillar and additional sponsorship from National Instruments and several other corporations. VictorTango qualified for the semi-finals during a site visit DARPA judges made to Virginia Tech earlier this year. The team's vehicle successfully demonstrated its fully autonomous capabilities, driving a road course and interacting with human-driven vehicles.DARPA is sponsoring the Urban Challenge as a more sophisticated follow-up to the two Grand Challenge competitions, which were held in 2004 and 2005 in the Mojave Desert. Virginia Tech competed in both of those contests, and the university's two entries placed eighth and ninth in 2005. "The Urban Challenge will be far more difficult to navigate than the open desert in the Grand Challenge," Currier said. "In the Grand Challenge, the vehicles followed a GPS 'bread crumb' trail and the obstacles they maneuvered around were static. In the Urban Challenge, vehicles must obey the rules of the road and avoid moving traffic."

Note: This story has been adapted from a news release issued by Virginia Tech.

Fausto Intilla

www.oloscience.com

Full-time Sensors Can Detect Bridge Defects

Source:

http://www.sciencedaily.com/releases/2007/08/070811213550.htm

Science Daily — Networks of small, permanently mounted sensors could soon check continuously for the formation of structural defects in I-beams and other critical structural supports of bridges and highway overpasses, giving structural engineers a better chance of heading off catastrophic failures.A Sandia National Laboratories team is developing and evaluating a family of such sensors for use on a variety of safety-critical structures.

Full-time monitoring sensors already have been tested and proven by Sandia for use on aircraft structures.Over time, the stresses on a bridge caused by traffic, weather, and construction can result in the formation of tiny cracks in the steel and concrete structures of bridges. Exposure to wind, rain, and other elements can cause corrosion that can become a structural concern as well. Like nerve endings in a human body, permanently mounted, or in-situ sensors offer levels of vigilance and sensitivity to problems that periodic checkups cannot, says Dennis Roach, who leads the Sandia team.Structural health monitoring (SHM) techniques, as they are called, are gaining acceptance in the commercial aviation sector as a reliable and inexpensive way to alert safety engineers to the first stages of defect formation and give them the earliest possible warning that maintenance is needed. With sensors continually checking for the first signs of wear and tear, engineers can detect cracks sooner, do the right maintenance at the right time, and possibly prevent massive failures, he says.Where flaws formSandia’s SHM work is an extension of its decades of research in non-destructive inspection (NDI) technologies currently used in manual inspections of commercial aircraft — to scan for small cracks in the airframe, for example. The SHM sensors being developed or evaluated at Sandia can find fatigue damage, hidden cracks, erosion, impact damage, and corrosion, among other defects commonly encountered in bridges.The Sandia team already has developed or evaluated several types of inexpensive, reliable sensors that could potentially be mounted on important infrastructure, typically where flaws are expected to form. “If I usually get fatigue damage in a particular area, that’s where I am going to install a sensor,” Roach says.One promising SHM sensor, a Comparative Vacuum Monitoring (CVM) sensor, is a thin, self-adhesive rubber patch, ranging from dime- to credit-card-sized, that detects cracks in the underlying material. The rubber is laser-etched with rows of tiny, interconnected channels or galleries, to which an air pressure is applied. Any propagating crack under the sensor breaches the galleries and the resulting change in pressure is monitored.The CVM sensors — manufactured by Structural Monitoring Systems, Inc. (SMS) — are inexpensive, reliable, durable, and easy to apply, says Roach. More important, they provide equal or better sensitivity than is achievable with conventional inspection methods and can be placed in difficult to access locations, he says.Some other sensors being considered include flexible eddy current arrays, piezoelectric transducers that can interrogate materials over long distances, embedded fiber optics, and conducting paint whose resistance changes when cracks form underneath.Smart structures possible“When we set out to do NDI, in the back of our minds we knew that eventually we wanted to create smart structures that ‘phone home’ when repairs are needed or when the remaining fatigue life drops below acceptable levels,” Roach says. “This is a huge step in the evolution of NDI.”“These sensors have been tested and shown to detect defects and fatigue in metal structures where safety is of utmost concern,” says Roger Hartman, manager of Sandia’s Infrastructure Assurance and NDI Department. By combining networks of sensors of various types with other advanced materials work Sandia has done, such as using composite materials to repair damage to a highway bridge or watching for the first signs of fatigue using computerized prognostics and health management algorithms, “you begin to evolve a system approach to making important infrastructure elements safer and more reliable,” Hartman says. Ultimately, a structural engineer might plug a laptop or diagnostic station into a central port on a bridge to download structural health data. Eventually “smart structures” fitted with many sensors and augmented with PHM algorithms could self-diagnose and signal engineers that repairs are needed or that they will be needed in a defined time downstream.Sandia already is investigating applying SHM to a variety of structures. In addition to bridges and aircraft, SHM techniques could be used to monitor the structural well-being of spacecraft, weapons, rail cars, oil recovery equipment, pipelines, buildings, armored vehicles, ships, wind turbines, nuclear power plants, and fuel tanks in hydrogen vehicles, Roach says. “There is widespread recognition that SHM’s time has come, an opinion you would not have heard from many people a few years ago,” he says.Sandia is a National Nuclear Security Administration laboratory.

Note: This story has been adapted from a news release issued by Sandia National Laboratories.

Fausto Intilla

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