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Thursday, August 21st, 2014

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    12:00a
    Unlocking the potential of simulation software

    With a method known as finite element analysis (FEA), engineers can generate 3-D digital models of large structures to simulate how they’ll fare under stress, vibrations, heat, and other real-world conditions.

    Used for mapping out large-scale structures — such as mining equipment, buildings, and oil rigs — these simulations require intensive computation done by powerful computers over many hours, costing engineering firms much time and money.

    Now MIT spinout Akselos has developed novel software, based on years of research at the Institute, that uses precalculated supercomputer data for structural components — like simulated “Legos” — to solve FEA models in seconds.

    A simulation that could take hours with conventional FEA software, for instance, could be done in seconds with Akselos’ platform.  

    Hundreds of engineers in the mining, power-generation, and oil and gas industries are now using the Akselos software. The startup is also providing software for an MITx course on structural engineering.

    With its technology, Akselos aims to make 3-D simulations more accessible worldwide to promote efficient engineering design, says David Knezevic, Akselos’ chief technology officer, who co-founded the startup with former MIT postdoc Phuong Huynh and alumnus Thomas Leurent SM’ 01.

    “We’re trying to unlock the value of simulation software, since for many engineers current simulation software is far too slow and labor-intensive, especially for large models,” Knezevic says. “High-fidelity simulation enables more cost-effective designs,  better use of energy and materials, and generally an increase in overall efficiency.”

    “Simulation components”

    Akselos’ software runs on a novel technique called the “reduced basis (RB) component method,” co-invented by Anthony Patera, the Ford Professor of Engineering at MIT, and Knezevic and Huynh. (The technique builds on a decade of research by Patera’s group.)

    This technique merges the concept of the RB method — which reproduces expensive FEA results by solving related calculations that are much faster — with the idea of decomposing larger simulations into an assembly of components.

    “We developed a component-based version of the reduced basis method, which enables users to build large and complex 3-D models out of a set of parameterized components,” Knezevic says.

    In 2010, the firm’s founders were part of a team, led by Patera, that used that technique to create a mobile app that displayed supercomputer simulations, in seconds, on a smartphone.

    A supercomputer first presolved problems — such as fluid flow around a spherical obstacle in a pipe — that had a known form, but for dozens of different parameters. (These parameters were automatically chosen to cover a range of possible solutions.) When app users plugged in custom parameters for problems — such as the diameter of that spherical obstacle — the app would compute a solution for the new parameters by referencing the precomputed data.

    Today’s Akselos software runs on a similar principle, but with new software, and cloud-based service. A supercomputer precalculates individual components, such as, say, a simple tube or a complex mechanical part. “And this creates a big data footprint for each one of these components, which we push to the cloud,” Knezevic says.

    These components contain adjustable parameters, which enable users to vary properties, such as geometry, density, and stiffness. Engineers can then access and customize a library of precalculated components, drag and drop them into an “assembler” platform, and connect them to build a full simulation. After that, the software will reference the precomputed data to create a highly detailed 3-D simulation in seconds. 

    In one demonstration, for instance, a mining company used components available in the Akselos library to rapidly create a simulation of shiploader infrastructure — complete with high-stress “hot spots” — that needed inspection. When on-site inspectors then found cracks, they relayed that information to the engineer, who added the damage to the simulation, and created modified simulations within a few minutes.

    “The software also allows people to model the machinery in its true state,” Knezevic says. “Often infrastructure has been in use for decades and is far from pristine — with damage, or holes, or corrosion — and you want to represent those defects,” Knezevic says. “That’s not simple for engineers today, since with other software it’s not feasible to simulate large structures in full 3-D detail.”

    Ultimately, pushing the data to the cloud has helped Akselos, by leveraging the age-old tradeoff between speed and storage: By storing and reusing more data, algorithms can do less work and hence finish more quickly.

    “These days, with cloud technology, storing lots of data is no big deal. We store a lot more data than other methods, but that data, in turn, allows us to go faster, because we’re able to reuse as much precomputed data as possible,” he says.

    Bringing technology to the world

    Akselos was founded in 2012, after Knezevic and Huynh, along with Leurent — who actually started FEA work with Patera group back in 2000 — earned a Deshpande innovation grant for their “supercomputing-on-a-smartphone” innovation.

    “That was a trigger,” Knezevic says. “Our passion and goal has always been to bring new technology to the world. That’s where the Deshpande Center and the MIT innovation ecosystem are great.”

    From there, Akselos grew with additional help from MIT’s Venture Mentoring Service (VMS), whose mentors guided the team in fundraising, sales, opening a Web platform to users, and hiring.

    “We needed a sounding board,” Knezevic says. “We’d go into meetings and bounce ideas around to help us make good decisions. I think all our decisions were influenced by that type of discussion. It’s a real luxury that you don’t have in other places.”

    In expanding their visibility, and to get back into the academic sphere, Akselos has teamed with Simona Socrate, a principal research scientist in mechanical engineering at MIT, who is using the startup’s software — albeit a limited version — in her MITx class, 2.01x (Elements of Structures).

    Feedback from students has been positive, Knezevic says. Primarily, he hears that the software is allowing students to “build intuition for the physics of structures beyond what they could see by simply solving math problems.”

    “In 2.01x  the students learn about axial loading, bending, and torsion — we have apps for each case so they can visualize the stress, strain, and displacement in 3-D in their browser,” he says. “We think it’s a great way to show students the value of fast, 3-D simulations.”

    Commercially, Akselos is expanding, hiring more employees in its three branches — in Boston, Vietnam, and Switzerland — building a community of users, and planning to continue its involvement with edX classes.

    On Knezevic’s end, at the Boston office, it’s all about software development, tailoring features to customer needs — a welcome challenge for the longtime researcher.

    “In academia, typically only you and a few colleagues use the software,” he says. “But in a company you have people all over the world playing with it and testing it, saying, ‘This button needs to be there’ or ‘We need this new type of analysis.’ Everything revolves around the customer. But it was good to have that solid footing in academic work that we could build on.”

    12:00a
    Delivery by drone

    In the near future, the package that you ordered online may be deposited at your doorstep by a drone: Last December, online retailer Amazon announced plans to explore drone-based delivery, suggesting that fleets of flying robots might serve as autonomous messengers that shuttle packages to customers within 30 minutes of an order.

    To ensure safe, timely, and accurate delivery, drones would need to deal with a degree of uncertainty in responding to factors such as high winds, sensor measurement errors, or drops in fuel. But such “what-if” planning typically requires massive computation, which can be difficult to perform on the fly.

    Now MIT researchers have come up with a two-pronged approach that significantly reduces the computation associated with lengthy delivery missions. The team first developed an algorithm that enables a drone to monitor aspects of its “health” in real time. With the algorithm, a drone can predict its fuel level and the condition of its propellers, cameras, and other sensors throughout a mission, and take proactive measures — for example, rerouting to a charging station — if needed.

    The researchers also devised a method for a drone to efficiently compute its possible future locations offline, before it takes off. The method simplifies all potential routes a drone may take to reach a destination without colliding with obstacles.

    In simulations involving multiple deliveries under various environmental conditions, the researchers found that their drones delivered as many packages as those that lacked health-monitoring algorithms — but with far fewer failures or breakdowns.

    “With something like package delivery, which needs to be done persistently over hours, you need to take into account the health of the system,” says Ali-akbar Agha-mohammadi, a postdoc in MIT’s Department of Aeronautics and Astronautics. “Interestingly, in our simulations, we found that, even in harsh environments, out of 100 drones, we only had a few failures.”

    Agha-mohammadi will present details of the group’s approach in September at the IEEE/RSJ International Conference on Intelligent Robots and Systems, in Chicago. His co-authors are MIT graduate student Kemal Ure; Jonathan How, the Richard Cockburn Maclaurin Professor of Aeronautics and Astronautics; and John Vian of Boeing.

    Tree of possibilities

    Planning an autonomous vehicle’s course often involves an approach called Markov Decision Process (MDP), a sequential decision-making framework that resembles a “tree” of possible actions. Each node along a tree can branch into several potential actions — each of which, if taken, may result in even more possibilities. As Agha-mohammadi explains it, MDP is “the process of reasoning about the future” to determine the best sequence of policies to minimize risk.

    MDP, he says, works reasonably well in environments with perfect measurements, where the result of one action will be observed perfectly. But in real-life scenarios, where there is uncertainty in measurements, such sequential reasoning is less reliable. For example, even if a command is given to turn 90 degrees, a strong wind may prevent that command from being carried out. 

    Instead, the researchers chose to work with a more general framework of Partially Observable Markov Decision Processes (POMDP). This approach generates a similar tree of possibilities, although each node represents a probability distribution, or the likelihood of a given outcome. Planning a vehicle’s route over any length of time, therefore, can result in an exponential growth of probable outcomes, which can be a monumental task in computing.

    Agha-mohammadi chose to simplify the problem by splitting the computation into two parts: vehicle-level planning, such as a vehicle’s location at any given time; and mission-level, or health planning, such as the condition of a vehicle’s propellers, cameras, and fuel levels.

    For vehicle-level planning, he developed a computational approach to POMDP that essentially funnels multiple possible outcomes into a few most-likely outcomes.

    “Imagine a huge tree of possibilities, and a large chunk of leaves collapses to one leaf, and you end up with maybe 10 leaves instead of a million leaves,” Agha-mohammadi says. “Then you can … let this run offline for say, half an hour, and map a large environment, and accurately predict the collision and failure probabilities on different routes.”

    He says that planning out a vehicle’s possible positions ahead of time frees up a significant amount of computational energy, which can then be spent on mission-level planning in real time. In this regard, he and his colleagues used POMDP to generate a tree of possible health outcomes, including fuel levels and the status of sensors and propellers.

    Proactive delivery

    The researchers combined the two computational approaches, and ran simulations in which drones were tasked with delivering multiple packages to different addresses under various wind conditions and with limited fuel. They found that drones operating under the two-pronged approach were more proactive in preserving their health, rerouting to a recharge station midmission to keep from running out of fuel. Even with these interruptions, the team found that these drones were able to deliver just as many packages as those that were programmed to simply make deliveries without considering health.

    Going forward, the team plans to test the route-planning approach in actual experiments. The researchers have attached electromagnets to small drones, or quadrotors, enabling them to pick up and drop off small parcels. The team has also programmed the drones to land on custom-engineered recharge stations.

    We believe in the near future, in a lab setting, we can show what we’re gaining with this framework by delivering as many packages as we can while preserving health,” Agha-mohammadi says. “Not only the drone, but the package might be important, and if you fail, it could be a big loss.”

    This work was supported by Boeing.

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