OREGON STATE UNIVERSITY

engineering and technology

OSU ember research: Smaller branches pack the fastest, biggest fire-spreading punch

CORVALLIS, Ore. – As the West tallies the damages from the 2017 wildfire season, researchers at Oregon State University are trying to learn more about how embers form and about the blaze-starting potential they carry.

Preliminary findings indicate the diameter of the branches that are burning is the biggest single factor behind which ones will form embers the most quickly and how much energy they’ll pack.

“Increased population in the wildland-urban interface means increased risk to life and property from wildland fires,” said Tyler Hudson, a graduate student in the College of Engineering. “Spot fires started by embers lofted ahead of the main fire front are difficult to predict and can jump defensible space around structures.”

Research shows smaller-diameter branches are better at producing embers, also known as firebrands.

“Embers are wildfires’ most challenging mode of causing spread,” said David Blunck, assistant professor of mechanical engineering. “By understanding how embers form and travel through the air, scientists can more accurately predict how fire will spread. We have a multiscale approach that involves burning samples in a laboratory setting, larger burns – burning 10-foot-tall trees – and then working with the U.S. Forest Service to participate in prescribed burns.”

In his lab, Blunck’s research group controls multiple parameters which can influence generation rates: fire intensity, crosswind velocity, species of tree, diameter of the sample, fuel condition (natural vs. processed), and moisture content of the fuel.

“Fire intensity had little effect on the time needed for ember generation,” Hudson said. “And natural samples and dowels with similar diameters can have quite different ember generation times.”

Using samples of Douglas fir, western juniper, ponderosa pine and white oak with diameters of 2 and 6 millimeters, the researchers determined that 2-millimeter samples generated embers roughly five times as fast as 6-millimeter samples.

This trend can be explained by the observation that the bending stress is proportional to 1 divided by the cube of the diameter – thus, the larger the diameter, the smaller amount of bending stress and a lesser likelihood of breakage, and ember creation. Moreover, smaller diameters have less fuel that needs to be burned.

In the field, researchers can track embers’ energy “from the time they leave the tree until they get to their destination,” Hudson said, using techniques ranging from infrared videography to measuring scorch marks on squares of fire-resistant fabric placed on the ground at varying distances from the fire. 

Blunck, Hudson and fellow mechanical engineering graduate student Mick Carter presented their preliminary findings in April at the 10th edition of the biennial U.S. National Combustion Meeting in College Park, Maryland.

In August, Blunck was among a group of collaborators receiving a $500,000 grant from the National Institute of Standards and Technology “for the development of a computer model that will define patterns for firebrand distribution during wildland-urban interface fires and their likelihood of igniting nearby structures.”

This past fire season in Oregon, roughly 2,000 fires combined to burn more than a half-million acres – that’s about 1,000 square miles, an area the size of Rhode Island.

One of the most devastating of those blazes was the Eagle Creek fire in the Columbia River Gorge, which scorched nearly 50,000 acres and threatened the historic Multnomah Falls Lodge – and provided a terrifying illustration of what embers can do.

“The fire jumped the river and started burning in Washington because of embers,” Blunck said. “We estimate that the fire jumped 2 miles across the river.”

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Ember research

With ‘material robotics,’ intelligent products won’t even look like robots

CORVALLIS, Ore. – Robots as inconspicuous as they are ubiquitous represent the vision of researchers in the new and burgeoning field of material robotics.

In an invited perspective paper published today in Science Robotics, Oregon State University researcher Yiğit Mengüç and three co-authors argue against looking at robotics as a “dichotomy of brain versus body.”

Mengüç and collaborators from the University of Colorado, Yale University and École Polytechnique Fédérale de Lausanne take a view that seeks to dissolve the basic assumption that robots are either “machines that run bits of code” or “software ‘bots’ interacting with the world through a physical instrument.”

“We take a third path: one that imbues intelligence into the very matter of a robot,” said Mengüç, assistant professor of mechanical engineering in OSU’s College of Engineering and part of the college’s Collaborative Robotics and Intelligent Systems Institute. “The future we’re dreaming of is one of material-enabled robotics, something akin to robots themselves being integrated into day-to-day objects.”

Such as footwear, for example.

“Shoes that are able to intelligently support your gait, change stiffness as you’re running or walking, or based upon the surface you’re on or the biomechanics of your foot,” Mengüç said. “That’s one potential product. Examples of that kind of material intelligence abound in nature, where complex functionality results from systems of simple materials.

“The point here with something like a self-adjusting shoe is it no longer resembles a robot – that’s kind of the direction of ubiquity we’re imagining.”

Mengüç notes that as technology becomes more capable it tends to follow a pattern of disappearing into the background of everyday life.

“Take smartphones,” he said. “Autocorrect, a very small and impoverished version of artificial intelligence, is ubiquitous.

“In the future, your smartphone may be made from stretchable, foldable material so there’s no danger of it shattering. Or it might have some actuation, where it changes shape in your hand to help with the display, or it can be able to communicate something about what you’re observing on the screen. What I would see as success for material robotics is where the technology we make is not static anymore – all these bits and pieces of technology that we take for granted in life will be living, physically responsive things, moving, changing shape in response to our needs, not just flat, static screens.”

At present, the authors note, two distinct approaches remain for creating composite materials that match the complexity of functional biological tissue: new materials synthesis and system-level integration of material components. 

Materials scientists are developing new bulk materials with the inherent multifunctionality required for robotic applications, while roboticists are working on new material systems with tightly integrated components.

“The convergence of these approaches will ultimately yield the next generation of material-enabled robots,” Mengüç said. “It’s a natural partnership that will lead to robots with brains in their bodies – inexpensive and ever-present robots integrated into the real world.”

Joining Mengüç in authoring the paper were Nikolaus Correll of the University of Colorado, Rebecca Kramer of Yale, and Jamie Paik of École Polytechnique Fédérale de Lausanne in Switzerland.

They were invited to contribute their thoughts on the state and direction of material robotics after organizing a workshop on the subject at the “Robotics: Science and Systems” conference held in July at the Massachusetts Institute of Technology. 

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OSU researcher part of DARPA grant for autonomous drone swarms

CORVALLIS, Ore. – An Oregon State University computer science professor is part of a team that will receive up to $7.1 million to develop a drone swarm infrastructure to help the U.S. military in urban combat.

The contract is part of the Defense Advanced Research Project Agency’s OFFSET program, short for Offensive Swarm-Enabled Tactics. The program’s goal, according to DARPA’s website, is “to empower … troops with technology to control scores of unmanned air and ground vehicles at a time.”

Julie A. Adams of OSU’s College of Engineering is on one of two teams of “swarm systems integrators” whose job is to develop the system infrastructure and integrate the work of the “sprint” teams that will focus on swarm tactics, swarm autonomy, human-swarm teaming, physical experimentation and virtual environments.

Raytheon BBN, a key research and development arm of the Raytheon Company, a major defense contractor, leads Adams’ team. The team also includes Smart Information Flow Technologies, a research and development firm. Northrop Grumman, an aerospace and defense technology company, heads the other team of integrators.

Adams, the associate director for deployed systems and policy at the college’s Collaborative Robotics and Intelligent Systems Institute, is the only university-based principal investigator on either team of integrators.

Researchers envision swarms of more than 250 autonomous vehicles – multi-rotor aerial drones, and ground rovers – to gather information and assist troops in “concrete canyon” surroundings where line-of-sight, satellite-based communication is impaired by buildings.

The information the swarms collect can help keep U.S. troops more safe, and civilians in the battle areas more safe as well.

“I specifically will work on swarm interaction grammar – how we take things like flanking or establishing a perimeter and create a system of translations that will allow someone to use those tactics,” Adams said. “We want to be able to identify algorithms to go with the tactics and tie those things together, and also identify how operators interact with the use of a particular tactic.

“Our focus is on the individuals who will be deployed with the swarms, and our intent is to develop enhanced interactive capabilities: speech, gestures, a head tilt, tactile interaction. If a person is receiving information from a swarm, he might have a belt that vibrates. We want to make the interaction immersive and more understandable for humans and enable them to interact with the swarm.”

Adams noted that China last summer launched a record swarm of 119 fixed-wing unmanned aerial vehicles.

“Right now we don’t have the infrastructure available for testing the capabilities of large swarms,” Adams said. “Advances have been made with indoor systems, including accurately tracking individual swarm members and by using simulations. Those are good first steps but they don’t match what will happen in the real world. Those approaches allow for testing and validation of some system aspects but they don’t allow for full system validation.”

The integrators’ objective is for operators to interact with the swarm as a whole, or subgroups of the swarm, and not individual agents – like a football coach orchestrating his entire offense as it runs a play.

“What the agents do individually is simple; what they do as a whole is much more interesting,” said Adams, likening a drone swarm to a school of fish acting in concert in response to a predator. “We’ve got these ‘primitives’” – basic actions a swarm can execute – “and we’ll map these primitives to algorithms for the individual agents in the swarm, and determine how humans can interact with the swarm based on all of these things. We want to advance and accelerate enabling swarm technologies that focus on swarm autonomy and how humans can interact and team with the swarm.” 

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Traffic signal countdown timers lead to improved driver responses

CORVALLIS, Ore. – Countdown timers that let motorists know when a traffic light will go from green to yellow lead to safer responses from drivers, research at Oregon State University suggests.

The findings are important because of mistakes made in what traffic engineers call the “dilemma zone” – the area in which a driver isn’t sure whether to stop or keep going when the light turns yellow.

A traffic signal countdown timer, or TSCT, is a clock that digitally displays the time remaining for the current stoplight indication – i.e., red, yellow or green. 

Widely adopted by roughly two dozen countries around the world, traffic signal countdown timers are not used in the U.S. Crosswalk timers for pedestrians are allowed, but TSCTs are prohibited by the Department of Transportation.

“When you introduce inconsistencies – sometimes you give drivers certain information, sometimes you don’t – that has the potential to cause confusion,” said David Hurwitz, transportation engineering researcher in OSU’s College of Engineering and corresponding author on the study.

There were more than 37,000 traffic fatalities in the United States in 2016. Around 20 percent of those occurred at intersections, he said.

It’s not known exactly how many U.S. intersections are signalized because no agency does a comprehensive count, but the National Transportation Operations Coalition estimates the number to be greater than 300,000.

A significant percentage of those feature fixed-time signals, which are recommended in areas with low vehicle speed and heavy pedestrian traffic.

Traffic signal countdown timers work well at fixed-time signals, Hurwitz said, but they may not be practical for actuated signals; at those intersections, he said, a light typically changes only one to four seconds after the decision to change it is made – not enough time for a countdown timer to be of value.

In this study, which used a green signal countdown timer, or GSCT, in Oregon State’s driving simulator, the clock counted down the final 10 seconds of a green indication.

A subject pool of 55 drivers ranging in age from 19 to 73 produced a data set of 1,100 intersection interactions, half of which involved a GSCT. The presence of the countdown timer increased the probability that a driver in the dilemma zone would stop by an average of just over 13 percent and decreased deceleration rates by an average of 1.50 feet per second.

“These results suggest that the information provided to drivers by GSCTs may contribute to improved intersection safety in the U.S.,” Hurwitz said. “When looking at driver response, deceleration rates were more gentle when presented with the countdown timers, and we did not find that drivers accelerated to try to beat the light – those are positives for safety. Drivers were significantly more likely to slow down and stop when caught in the dilemma zone. The results in the lab were really consistent and statistically convincing.”

The findings, published recently in Transportation Research Part F: Traffic Psychology and Behaviour, build on a 2016 paper in Transportation Research Part C: Emerging Technologies.

The earlier results, which arose from a related research project, showed drivers were more ready to go when the light turned green at intersections with a red signal countdown timer, which indicates how much time remains until the light goes from red to green. The first vehicle in line got moving an average of 0.82 seconds more quickly in the presence of a timer, suggesting an intersection efficiency improvement thanks to reduction in time lost to startups.

The papers comprised dissertation work by then Ph.D. student Mohammad Islam, who now works for a Beaverton, Oregon-based company, Traffic Technology Services. Amy Wyman, an OSU Honors College undergraduate who completed her degree in 2017, collaborated on the publication.

TTS, whose chief executive officer, Thomas Bauer, is also an OSU College of Engineering alumnus, has developed a cloud-computer-connected countdown timer for the automotive industry.

Several cars in the German luxury carmaker Audi’s 2017 lineup already feature the timer, which can be viewed both on the instrument panel and via a heads-up display. The system is currently operational in several U.S. cities including Portland.

Unlike the traffic-signal-mounted timers, the onboard clocks are allowed in the U.S. 

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The "dilemma zone"

Assessment shows metagenomics software has much room for improvement

CORVALLIS, Ore. – A recent critical assessment of software tools represents a key step toward taming the “Wild West” nature of the burgeoning field of metagenomics, said an Oregon State University mathematical biologist who took part in the research.

Metagenomics refers to the science of genetically studying whole communities of microorganisms, as opposed to sequencing single species grown in culture.

“Microbes are ridiculously important to life,” said David Koslicki, assistant professor of mathematics in the OSU College of Science. “They not only can cause terrible things to happen, like blight and disease, but in general, overwhelmingly, microbes are our friends. Without them doing their jobs, crops couldn’t grow as well, it would be hard to digest our food, we might not get sleepy at appropriate times. Microbes are so fundamental to life, to health, we really need to know as much as we can about them.”

Koslicki, a leader in a university-wide research and education program known as OMBI – the OSU Microbiome Initiative – described the findings, published recently in Nature Methods, as “sobering." 

“There are not a lot of well-established, well-characterized computational techniques and tools that biologists can use,” he said. “And the assessment showed that a lot of the tools being used do not do nearly as well as had been initially thought, so there’s definitely room for improvement there.

“That said, depending on the situation that a biologist is interested in, there are definitely different tools that have proven to be the best so far.”

Metagenomics is a relatively new field that developed quickly once next-generation sequencing grew inexpensive enough that looking at entire microbial communities became economically feasible, said Koslicki.

“The typical view of biology is a wet lab and everything like that, but a whole other facet has to do with these high-throughput ways of accessing genetic material,” he said. “You end up with a ton of data, and when you end up with a ton of data, you introduce new problem: How do I get the important information out of it? You have to come up with an algorithm that allows biologists to answer the questions they find important: What critters are there, how many are there, what are they doing, are there any viruses? We need to answer those questions and not just answer them quickly but also have some sort of idea how accurate the answer is.”

The dizzying array of tools biologists are using to try to answer those questions is “kind of like the Wild West,” Koslicki said. “If you want to learn what bacteria are in a sample, there are no less than three or four dozen different tools people have come up with, and in a rather disjointed manner. You have teams of statisticians, mathematicians, biologists, microbiologists, engineers all looking at this from their own perspectives and coming up with their own tools. Then the end-user biologist comes along and is faced with 40 different tools, and how do they know how good they are at answering the questions they need answered?”

Koslicki’s research, known as the CAMI challenge – critical assessment of metagenome interpretation –was aimed at ranking those tools to provide a road map for biologists.

“The challenge engaged the global developer community to benchmark their programs on highly complex and realistic data sets, generated from roughly 700 newly sequenced microorganisms and about 600 novel viruses and plasmids and representing common experimental setups,” he said. “This was an independent initiative. Typically when tools are compared, it’s attached to the publication of a new method that’s compared to other tools that do worse, so the new method looks good. There hasn’t been a lot of independent research into which tools actually work, how well they work, what kind of data do they well on, etc.”

The UK Engineering and Physical Sciences Research Council, the U.S. Department of Energy, the Cluster of Excellence on Plant Sciences, the Australian Research Council, the European Research Council, the Agency for Science, Technology and Research Singapore, the Lundbeck Foundation, and the National Science Foundation supported this research.

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Oregon State to host grid energy storage symposium

CORVALLIS, Ore. – Leaders in energy storage technology will converge on the Oregon State University campus Nov. 5-6 for a symposium to discuss opportunities and challenges for next-generation, large-scale grid energy storage systems in the Pacific Northwest and nationwide.

The meeting, expected to draw 100 to 150 participants, is intended to serve as a forum for industry representatives, utility companies, academic and government researchers, and policymakers to discuss energy storage and potential major applications in the region.

 “This meeting brings together the thought leaders who are driving the implementation of novel energy storage systems for the grid, wave power, and other sustainable energy technologies,” said conference chair Zhenxing Feng, assistant professor of chemical engineering in OSU’s College of Engineering. “These are the enabling technologies that can make the dream of 100 percent renewable energy into a reality.”

The symposium is being organized by Oregon State with assistance from the Joint Center for Energy Storage Research, a public/private partnership established by the U.S. Department of Energy in 2012. Topics for discussion include the status of current battery technology, challenges and opportunities in the emerging sectors of transportation and the energy grid, energy resilience in the electrical grid, special needs in Oregon, and commercialization and manufacturing opportunities throughout the region.

Invited presenters include researchers from Argonne National Laboratory, Pacific Northwest National Laboratory and Idaho National Laboratory, as well as representatives from industry, such as Lebanon, Oregon-based Entek International LLC.

The agenda includes keynote speakers, panel discussions, breakout sessions and a poster session networking event. Also planned are tours to a local utility company and Oregon State’s state-of-the-art facility for energy storage and materials characterization research.

More information and registration are available online at cbee.oregonstate.edu/energy-storage-symposium. 

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Keith Hautala, 541-737-1478

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Ocean Sentinel

Testing wave energy

New blue pigment discovered at Oregon State earns EPA approval

CORVALLIS, Ore. – The vibrant YInMn blue pigment discovered at Oregon State University has been approved for commercial sale by the Environmental Protection Agency.

The Shepherd Color Co., which licensed the pigment from OSU, announced that the EPA has granted the company a “low volume exemption” that paves the way for the pigment, commercially known as Blue 10G513, to be used in industrial coatings and plastics.

YInMn refers to the elements yttrium, indium and manganese, which along with oxygen comprise the pigment. It features a unique chemical structure that allows the manganese ions to absorb red and green wavelengths of light while only reflecting blue.

The pigment, created in OSU’s College of Science, has sparked worldwide interest, including from crayon maker Crayola, which used the color as the inspiration for its new Bluetiful crayon.

The pigment is so durable, and its compounds are so stable – even in oil and water – that the color does not fade. Those characteristics make the pigment versatile for a variety of commercial products; used in paints, for example, they can help keep buildings cool by reflecting the infrared part of sunlight.

The EPA approval announced this week does not include making the pigment available for artists’ color materials, but Shepherd is in the process of seeking approval for its use in all applications and is confident that will happen, company spokesman Mark Ryan said.

YInMn blue was discovered by accident in 2009 when OSU chemist Mas Subramanian and his team were experimenting with new materials that could be used in electronics applications.

The researchers mixed manganese oxide – which is black in color – with other chemicals and heated them in a furnace to nearly 2,000 degrees Fahrenheit. One of their samples turned out to be a vivid blue. Oregon State graduate student Andrew Smith initially made these samples to study their electrical properties.

“This was a serendipitous discovery, a happy accident,” said Subramanian, the Milton Harris Chair of Materials Science at OSU. “But in fact, many breakthrough discoveries in science happen when one is not looking for it. As Louis Pasteur famously said, ‘In the fields of observation, chance favors only the prepared mind.’

“Most pigments are discovered by chance,” Subramanian added. “The reason is because the origin of the color of a material depends not only on the chemical composition, but also on the intricate arrangement of atoms in the crystal structure. So someone has to make the material first, then study its crystal structure thoroughly to explain the color.”  

Subramanian notes that blue is associated with open spaces, freedom, intuition, imagination, expansiveness, inspiration and sensitivity.

“Blue also represents meanings of depth, trust, loyalty, sincerity, wisdom, confidence, stability, faith, heaven and intelligence,” he said. “Through much of human history, civilizations around the world have sought inorganic compounds that could be used to paint things blue but often had limited success. Most had environmental and/or durability issues. The YInMn blue pigment is very stable and durable. There is no change in the color when exposed to high temperatures, water, and mildly acidic and alkali conditions.”

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Blue pigment

YInMn blue

Study shows high cost of truckers not having enough places to park and rest

CORVALLIS, Ore. – A pilot study by Oregon State University illustrates the high economic cost of having too few safe places for commercial truck drivers to park and rest.

Over a seven-year period on one 290-mile stretch of highway alone, at-fault truck crashes resulted in approximately $75 million of “crash harm,” research conducted by the OSU College of Engineering for the Oregon Department of Transportation shows.

“Current crash data collection forms don’t have an explicit section for truck-parking-related crashes, but we can operate under the assumption that specific types of at-fault truck crashes, such as those due to fatigue, may be the result of inadequate parking,” said the study’s lead author, Salvador Hernandez, a transportation safety and logistics researcher at Oregon State.

Hernandez and graduate research assistant Jason Anderson analyzed Oregon’s portion of U.S. Highway 97, which runs the entire north-south distance of the state along the eastern slope of the Cascade Range.

Highway 97 was chosen, Hernandez said, because the idea for the study originated from ODOT’s office in Bend, which is near the highway’s Oregon midpoint. An impetus for the research was the 2012 passage of “Jason’s Law,” which prioritized federal funding to address a national shortage of truck parking.

Jason’s Law is named for truck driver Jason Rivenburg, who was robbed and fatally shot in South Carolina in 2009 after pulling off to rest at an abandoned gas station.

For “property-carrying drivers,” as opposed to bus operators, federal rules require drivers to get off the road after 11 hours and to park and rest for at least 10 hours before driving again.

“Around the country, commercial drivers are often unable to find safe and adequate parking to meet hours-of-service regulations,” Hernandez said. “This holds true in Oregon, where rest areas and truck stops in high-use corridors have a demand for truck parking that exceeds capacity. That means an inherent safety concern for all highway users, primarily due to trucks parking in undesignated areas or drivers exceeding the rules to find a place to park.”

Researchers looked at what other states were doing in response to the parking issue, surveyed more than 200 truck drivers, assessed current and future parking demand on Highway 97, and used historical crash data to identify trends and hot spots and to estimate crash harm.

“Crash trends in terms of time of day, day of the week, and month of the year follow the time periods drivers stated having trouble finding places to park,” Hernandez said. “In Oregon, if we do nothing to address the problem and freight-related traffic continues to grow, we’ll face greater truck parking shortages. A possible solution is finding ways to promote public-private partnerships, the state working together with industry.”

A solution is not, Hernandez said, simply waiting for the day autonomous vehicles take over the hauling of freight as some predict.

“There are many issues yet to be worked out with autonomous commercial motor vehicles,” he said, “and even if autonomous commercial motor vehicles become commonplace, we’re still going to need truck drivers in some capacity. For now and in the foreseeable future, we need truck drivers and safe and adequate places for the drivers to park and rest.” 

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OSU partners with ODOT on system for better transit planning

CORVALLIS, Ore. – Public transit planners throughout the nation should soon be rolling toward more informed decision making and better service thanks to a partnership between Oregon State University’s College of Engineering and the Oregon Department of Transportation.

The university and state transportation officials have teamed up on an extension to the General Transit Feed Specification, commonly known as the GTFS. The extension is called GTFS-ride.

OSU will release open-source tools for GTFS-ride data storage and analysis sometime this fall, said J. David Porter, professor of industrial engineering at Oregon State. With those tools, planners can see in general how well transit networks are functioning and also easily access specific information about where riders tend to get on and off.

In existence for just over a decade, the GTFS defines a common data format for public transportation schedules and related geographic information. Mobile developers use the publicly available data to create applications that riders can use to learn, for example, when the next bus is arriving.

The 12-month OSU-ODOT partnership resulted in the GTFS-ride extension, which defines a common format for fixed-route transit ridership. The extension will support the creation of common tools for enhancing transit planners’ ability to analyze and share ridership data.

“The main motivation for the project was ODOT and in particular their Rail and Public Transit Division didn’t feel they had enough access to ridership data to be able to make informed decisions about funding and improvement projects,” said Porter, who teamed with OSU graduate students Ben Fields, Sylvan Hoover and Phillip Carleton on the project.

“GTFS-ride extends GTFS and incorporates additional files and fields for transit agencies to reflect their ridership information. It will enable agencies at many different levels of maturity and technological capability to represent ridership in a standardized way that will facilitate information sharing and the use of common software tools. Planners will be able to better understand what a change to a single network does to the entire state network.”

At present, each transit agency in Oregon uses a mix of proprietary tools and locally developed solutions to analyze and report transit ridership data; there has been no standardized format for representing ridership.

“The old way of doing things made taking advantage of and sharing transit ridership data difficult,” said Hal Gard, administrator of ODOT’s Rail and Public Transit Division. “The GTFS-ride data standard will make it possible for organizations at all levels to get easy access to detailed ridership data.”

A description of the GTFS-ride standard is available at https://github.com/ODOT-PTS/GTFS-ride/blob/master/spec/en/reference.md, and a companion open source GTFS-ride validation tool is available at https://github.com/ODOT-PTS/transitfeed-ride.

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New algorithm, metrics improve autonomous underwater vehicles’ energy efficiency

CORVALLIS, Ore. – Robotics researchers have found a way for autonomous underwater vehicles to navigate strong currents with greater energy efficiency, which means the AUVs can gather data longer and better.

AUVs such as underwater gliders are valuable research tools limited primarily by their energy budget – every bit of battery power wasted via inefficient trajectories cuts into the time they can spend working.

“Historically, a lot of oceanography data sets and sampling came from using ships, which are expensive and can only really be out for a few days at a time,” said Dylan Jones, a third-year Ph.D. student in Oregon State University’s robotics program and lead author on the study. “With autonomous underwater vehicles, you can get months-long monitoring. And a way to extend those vehicles’ missions is through smarter planning for how they get from one point of interest to another.”

Jones and Ph.D. advisor Geoff Hollinger, assistant professor of mechanical engineering in OSU’s College of Engineering, have built a framework for the vehicles to plan energy-efficient trajectories through disturbances that are strong and uncertain, like ocean currents and wind fields.

The framework involves an algorithm that samples alternate paths, as well as comparison metrics that let a vehicle decide when it makes sense to switch paths based on new information collected about environmental disturbances.

The researchers tested the framework in a simulated environment – a data set of currents from the Regional Ocean Modeling System – and also on a windy lake with an autonomous boat.

The results, recently published in IEEE Robotics and Automation Letters, show that the algorithm can plan vehicle paths that are more energy efficient than ones planned by existing methods, and that it’s robust enough to deal with environments for which not much data is available.

Findings also indicate that three of the framework’s five path comparison metrics can be used to plan more efficient routes compared to planning based solely on the ocean current forecast.

“We generalized past trajectory optimization techniques and also removed the assumption that trajectory waypoints are equally spaced in time,” Jones said. “Removing that assumption improves on the state of the art in energy-efficient path planning. 

“These are under-actuated vehicles – they don’t go fast in relation to the strong ocean currents, so one way to get them to travel more efficiently is to go with the flow, to coast and not use energy,” he added. “We’re building more intelligence into these vehicles so they can more reliably accomplish their missions.”

Jones notes that overcoming strong disturbances is a critical component of putting any kind of robot in a real-life environment. Past planning algorithms haven’t always considered the dynamics of the vehicle they were planning for, he said.

“Sometimes we make assumptions in the lab or do simulations that don’t translate in the real world,” Jones said. “Sometimes a disturbance is too strong to be overcome, or sometimes it can be overcome but the path deviates so significantly that it would put the robot in a danger area. We have to consider all the possible locations of a robot. There are smarter ways of considering these various disturbances, and this gives us a better way of planning paths that are least affected by disturbances.”

Any disconnect between the controller and the planner can be dangerous, Jones said.

“The way we see this work going is to bridge that gap – how do we look at paths that are easier for controllers to follow, and how do we make controllers follow paths better?” he said. “We can be more energy efficient when we consider the whole environment, planning paths so that the controller of the vehicle doesn’t have to work as hard.”

Future research will also deal with “informative path planning” – planning paths that initially gather information about the environment and disturbances that the algorithm can use later to plan more energy-efficient routes.

“How do we combine these two ideas – planning a path for energy efficiency while also trying to gather information that will inform efficient path planning?” Jones said. “There will be tradeoffs and it might come down to, do I pay five hours now to save six hours later on? Another possible research direction is to look at a multivehicle situation where one vehicle can scout ahead and relay information to one or more others – they could possibly have a low shared energy cost by intelligently assigning goals and sharing information.”

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AUV paths planned by framework