Posts Tagged ‘sonar’
Wednesday, December 12, 2012 @ 03:12 PM gHale
Using a combination of water pressure and computer vision technology, a new “sense-ational” sensory device is able to give users a 3-D image of nearby objects and map its underwater surroundings.
The sensor can potentially replace the expensive “eyes and ears” on Autonomous Underwater Vehicles (AUVs), submarines and boats that currently rely on cameras and sonars to gather information about the environment around them.
The low-powered sensor is unlike cameras which cannot see in dark or murky waters or sonars whose sound waves pose harm to some marine animals.
These extremely small sensors (each sensor is 1.8mm x 1.8mm) are now seeing use in AUVs developed by researchers from Singapore-MIT Alliance for Research and Technology (SMART), a research center funded by the National Research Foundation. The center is developing a new generation of underwater “stingray-like” robots and autonomous surface vessels.
The new sensors, made using Microelectromechanical Systems (MEMS) technology, will make such robots smarter and prolong their operational time as they are able to conserve battery power.
Associate Professor Miao Jianmin from the School of Mechanical and Aerospace Engineering, and his team of four have spent the last five years in collaboration with SMART to develop micro-sensors that mimic the row of “feelers” on both sides of the Blind Cave Fish body.
Associate Prof Miao said the line of sensors present on the fish’s body is the reason why it can sense objects around it and still travel at high speeds without colliding with any underwater obstacles.
“To mimic nature, our team created microscopic sensory pillars wrapped in hydrogel — a material which is similar to the natural neuromasts of the blind cave fish — into an array of two rows of five sensors,” Prof Miao said.
“This array of micro-sensors will then allow AUVs to locate, identify, and classify obstacles and objects in water through water pressure and also to optimize its movement in water by sensing the water flow.”
The new sensor array, which costs less than $100 to make, is also more affordable than sonars, which can detect faraway objects but not nearby objects and cost thousands of dollars.
Partnering with Miao to develop the sensors and to adopt it for use on AUVs is Professor Michael Triantafyllou from SMART. Triantafyllou, from SMART’s Center for Environmental Sensing and Modeling (CENSAM), is an expert on creating underwater robots modeled after aquatic animals.
Current problems with AUVs include poor navigation in murky or cloudy waters such as those off the coast of Singapore, as underwater cameras can only see a short distance, Triantafyllou said.
“Other methods like underwater lights and cameras, acoustic navigation, and sonars also work, but they are very expensive and require very high levels of power that drain the batteries. The new sensors are much cheaper and only require small amounts of power. Also, sensors like sonar are loud and invasive and they may harm aquatic animals that also use sound waves to navigate,” the Massachusetts Institute of Technology professor added.
The aim of the AUVs is for environmental sensing, to detect environmental pollution, contaminants and to monitor the overall water quality in Singapore’s waters. The AUVs will have chemical sensors installed to detect the chemical condition of water (dissolved oxygen, nutrients, metals, oils, and pesticides), and biological sensors to monitor water conditions such as harmful bacteria and pathogens.
Other potential application of these MEMS sensors, which specializes in near-field detection include defense applications. These can detect nearby submarines without the use of sonar that gives away one’s location.
Wednesday, September 8, 2010 @ 06:09 PM gHale
It is all about fighting off terrorism and searching areas man can’t get into. Oh yeah, it is also about winning a competition.
In less than two years, an unmanned aircraft search and rescue competition will take place in a remote area in Australia.
And Kevin Kochersberger, director of the Unmanned System Lab (USL) at Virginia Tech, is getting ready now as he hopes to take a student design team and win the $50,000 prize money.
Kochersberger first USL team won second place in the 2008 outdoor aerial robotic competition and they came home with $17,000 in prize money, partially because no team among the 40 entrants won the first prize.
The Association of Unmanned Vehicle System International altered the competition the next year to an indoor event. The entrants must fly their autonomous unmanned vehicle, a quad-rotor vertical takeoff and landing aircraft, safely into and through a building. Each year, the students are building upon the previous teams’ research.
In 2012, the sixth international competition will work under the following real-life scenario: Credible information from an intelligence agency indicates highly sensitive information detailing plans to sabotage the control of the Eurasian banking system is contained on an unsecured USB flash drive kept in a remote and highly secured office. The mission of the autonomous vehicle is to remove the flash drive by entering through an upper-story broken window. Added to the complicated task, the vehicle must be able to read Arabic, and then decide how to proceed once inside the building.
Alex Marshall, of Charlottesville, Va., a graduate of mechanical engineering, was the mechanical sub-team leader in 2010, and it was his responsibility to work on a pick-up mechanism for the most recent version of the design. “It’s really cool to be building something from scratch. Last year’s model was badly damaged when it was shipped to the competition, and wires went everywhere. They had used a sonar-like device to locate the walls when the machine was flying. This year we are using a laser range finder.”
The change in the sensing mechanism is making the new aircraft much bigger and bulkier, and the hardware is more expensive, Marshall said. The real trick is the rules of the competition demand the design be below a maximum weight limit of 1500 grams.
Marshall spent much of his time developing the pick-up device that would snatch a USB flash drive randomly placed inside the building, and replace it with a decoy.
Other groups on the team are navigational and vision experts. The navigation team creates a stable and intelligent vehicle flight. Requirements for the vehicle’s vision in this competition are the ability to recognize a security sign and its indicated direction, identify the flash drive and its position as related to the vehicle, understand if an LED light and a laser grid shut off button is on or off, and be able to communicate to the controller, who does not have visual contact.
“I have learned how the different sub-teams working on different aspects of this project must be able to mesh their ideas together,” Marshall said. The entire team meets twice a week, but we spend about 10 to 12 hours a week, sometimes more, on this project. We give updates to Dr. K, and he helps us define our short term goals.”
Marshall said there are often disagreements, but the students have to work toward a final design that is palatable to all of the sub-teams. “It is essential that we remain in touch with each other so the final design comes together nicely and works,” he grinned.
He cited as an example one requirement that demands the quad-rotor to have 240 degrees of unobstructed viewing power. His participation in the mechanical team makes him responsible for this criterion, but he also must ensure his colleagues on the vision and navigational teams do not include components that will eventually obstruct this view.
Click here to learn more about unmanned systems research at Virginia Tech.
Wednesday, September 1, 2010 @ 06:09 PM gHale
Speakers made from carbon nanotube sheets a fraction of the width of a human hair can generate sound and cancel out noise at the same time, which is perfect for submarine sonar to probe the ocean depths, while making it invisible to enemies.
Thin films of nanotubes can generate sound waves via a thermoacoustic effect, said Ali Aliev, Ph.D. of the MacDiarmid NanoTech Institute at the University of Texas at Dallas. Every time an electrical pulse passes through the microscopic layer of carbon tubes, the air around them heats up and creates a sound wave.
Chinese scientists first discovered that effect in 2008, and applied it in building flexible speakers. The Chinese nanoscientists stuck a sheet of nanotubes onto the side of a flag, and attached it to an mp3 player. They used the nanotube-coated flag to play a song while it flapped in the breeze. But they did not test its ability to operate under water.
Taking the next step, Aliev’s group showed nanotube sheets produce the kind of low-frequency sound waves that enable sonar to determine the location, depth, and speed of underwater objects.
They also verified speakers can tune into to specific frequencies to cancel out noise, such as the sound of a submarine moving through the depths.