Putting the Buzz in Navigation

Getty Images A bee arrives at a flowering bush, rapidly explores it and assesses which flowers to visit. For an insect with a tiny brain and a lifespan measured in weeks, it's an impressive display of navigational skill, learning, and selective perception. A growing body of research into insect vision and cognition has provided not only basic insights into biology and problem solving, but also some surprising robotics, aviation, and military applications as well. Bees and dragonflies use ingenious tricks for perceiving and navigating their world in three dimensions1 and have proven to be fruitful subjects. Dragonflies, which have acute vision and superb flying skills, use a strategy known as active motion camouflage based on a visual illusion to conceal themselves when shadowing prey and escaping from predators. Akiko Mizutani, Australian National University's (ANU) biorobotics laboratory, and colleagues reported that male dragonflies (Hemianax papuensis) adjust their flight paths so that to a rival or prey they appear not to move at all, a trick used by fighter pilots to assume a favorable aerial combat position without being noticed.2 Australia's major public military research agency, the Defense Science and Technology Organisation (DSTO), and the US Office of Naval Research are supporting that research in a project aimed at developing techniques for automatic flight maneuvers, with possible applications in unpiloted aerial vehicles. Researchers at the biorobotics laboratory, led by Mandyam V. Srinivasan, and at DSTO are also working with other US agencies, including the Defense Advanced Research Projects Agency, the Navy Air Weapons Center, the Air Force, and NASA, to develop other insect-inspired technologies that may one day be used in aerial vehicles in warfare and to explore the surface of Mars. BEE POWER Bee vision and navigation, in particular, are receiving renewed appreciation for such applications. Bees were once thought capable of seeing only about 100 colors but are now known to have color vision roughly equal to that of humans. They have the additional capacity to detect ultraviolet radiation, notes Adrian Dyer, another Australian researcher with a special interest in bee vision. One team, headed by Lars Chittka, at Queen Mary University of London, studied bumblebee foraging and reported that some bees go for a fast, high-risk strategy, while others are slower and more careful.3 When tested on color discrimination tasks in a virtual flower meadow, bees punished for making mistakes slowed down and performed better. "We also discovered that bees can discriminate between blue colors just as well as we can if they learn to take their time," says Dyer, a team member. On the other hand, "studying human vision is difficult," he continues. "Bumblebee eyes do one job very well: finding the right flowers. So by studying bees we can learn about our own vision and gain insights into how we might design minute vision systems for robots and other machines." Bees, well known as essential pollinators for many agricultural crops, also have potential as drug and bomb detectors, he says. Another team recently reported a series of experiments in which bees rapidly learned to discriminate topologically different patterns and to generalize the learned cue onto other novel patterns.4 They suggested, therefore, that topology may be a fundamental component of the vocabulary by which visual systems represent and characterize objects. APIAN OPTICS Srinivasan and colleagues have been actively studying bee vision and navigation for more than a decade, unraveling a number of principles by which insects see, control flight, and navigate. They have learned that bees distinguish objects from backgrounds by sensing what they perceive as relative motion occurring at the boundary between object and background.5 As a person, animal, or insect moves through the world, almost everything seen is also moving on the retina. The pattern of this retinal motion, called optic flow, is dependent on the motion of the observer. Bees use optic flow to calculate the rate at which they must slow their flight speed so that it is close to zero at touchdown.6 Bees flying through a specially designed tunnel can maintain equidistance to the sidewalls by balancing the apparent speeds of the images of the walls. By holding constant the average image velocity in each eye, the bees regulated their flight speed. By controlling how much information the bee received from each eye as it flew along the tunnel, the ANU researchers identified the key role that optic flow occupies in navigation.7 GETTING CLEVER Foraging bees gauge the distance they have flown, not by monitoring their energy expenditure as once thought, but by integrating optic flow. They possess a vision-driven "odometer" that can integrate variations in wind, body weight, and energy expenditures.8 © Jenny Rasmussen, www.tinybirds.com A 'wandering glider' in flight "Insects cope remarkably well with their world, despite possessing a tiny brain that carries far fewer nerve cells than our own," says Srinivasan.9 He reasoned that this ability might provide the inspiration for some simple, effective, and inexpensive short-cut solutions to many applications. "The idea is rather than try and emulate human vision, we try to use some of the clever solutions that simpler organisms seem to have evolved." The latest product of that line of inquiry was realized last month when a joint DSTO-ANU team traveled to the United States to demonstrate a small unmanned delta-wing aircraft featuring information-processing technology drawn from insects at a NASA test range in the Mojave Desert northeast of Los Angeles. The demonstration was intended to show that small aircraft equipped with an array of simple sensors, including cameras, can avoid collision with the ground even over rough terrain, says project leader Javaan Chahl, of DSTO. Chahl and colleagues analyzed the ocelli, an obscure sensor organ in dragonfly heads, and found a complex optical and neural arrangement that helps the insects maintain level flight under adverse conditions. Chahl's team has developed electronic ocelli based on those found in dragonflies, according to DSTO, to measure the distribution of ultraviolet and green light to maintain level flight. They also have borrowed from the insect world to develop a sun compass that uses the polarization pattern of skylight. The success of the US forces' Global Hawk and Predator unmanned aircrafts during the Afghanistan and Gulf conflicts enhanced their standings as significant battle-zone assets for surveillance roles and remote-weapons platforms. But these craft are vulnerable, says a DSTO spokesperson, because they depend on several technologies, including radar; the satellite-based global positioning system (GPS), which can be used to compute position, velocity, and time; other active devices for navigation; and radio links to pilot controllers. Their transmissions can expose both the aircraft and their controllers to counter-attack and thus compromise their role in covert surveillance. The Chahl team, inspired by bee-vision systems, also has programmed computers for collision avoidance by determining the distance of objects using pattern recognition to assess the object's apparent speed. "The ocelli need weigh no more than a few hundred milligrams, and the collision avoidance sensor could weigh in the order of 5 grams," Chahl says. "These small sensors would allow many small aircraft, as light as 75 grams, to be carried to the surface of Mars." Thanks to entomological assistance, the autonomous aircraft guided by these sensors and systems have progressed over the past two years from being merely able to hover over landmarks in known locations to using controlled, autonomous, straight flight close to the ground in completely unstructured environments, without the need for GPS. "We can also hover at arbitrary height over unstructured terrain using vision and inertial guidance, again without GPS," Chahl says. They expect by the end of this year to be able to program the aircraft to take off and land using robotic vision, along with a functioning navigational sensor. Final test results are due next year. Bob Beale (bobbeale@bigpond.com) is a freelance writer in Sydney, Australia. References 1. M.V. Srinivasan, "How insects infer range from visual motion," in Visual Motion and its Role in the Stabilization of Gaze, F.A. Miles and J. Wallman (eds), Amsterdam: Elsevier, p. 139-56, 1993. 2. A. Mizutani et al., "Motion camouflage in dragonflies," Nature, 423:604, 2003. 3. L. Chittka et al., "Psychophysics: Bees trade off foraging speed for accuracy," Nature, 424:388, 2003. 4. L. Chen et al., "Global perception in small brains: topological pattern recognition in honey bees," Proc Natl Acad Sci, 100:6884-9, 2003. 5. M.V. Srinivasan et al., "Visual figure-ground discrimination in the honeybee: the role of motion parallax at boundaries," Proc R Soc Lond B, 238:331-50, 1990. 6. M.V. Srinivasan et al., "Range perception through apparent image speed in freely-flying honeybees," Vis Neurosci, 6:519-35, 1991. 7. M.V. Srinivasan et al., "Honeybee navigation en route to the goal: visual flight control and odometry," J Exp Biol, 199:237-44, 1996. 8. M.V. Srinivasan et al., "Visually mediated odometry in honeybees," J Exp Biol, 200:2513-22, 1997. 9. M.V. Srinivasan et al., "Honeybees link sights to smells," Nature, 396:637-8, 1998. function sendData() { document.frm.pathName.value = location.pathname; result = false if (document.frm.score[0].checked) result = true; if (document.frm.score[1].checked) result = true; if (document.frm.score[2].checked) result = true; if (document.frm.score[3].checked) result = true; if (document.frm.score[4].checked) result = true; if (!result) alert("Please select") return result; } .myradio{background-color : #94bee5} Please indicate on a 1 - 5 scale how strongly you would recommend this article to your colleagues? Not recommended 1 2 3 4 5 Highly recommended Please register your vote

Putting the Buzz in Navigation

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