Floats like a butterfly. Stings like a bee -The new surveillance robots are small and smart enough to fool nature as well as opponents. For the last five years, the DelFly team at the Delft University of Technology in the Netherlands has been designing miniature insect-like robots that fly around and stream live video back to their base controller. The team's aim is to maximize aerodynamic efficiency and minimize onboard instruments.
It got a chance to put one of its creations into action two years ago, when a fire ruined the university's architecture building. The 14-storey building was beyond repair, but held valuable book and furniture collections. Video footage of the interior could help determine whether it was worth the risk of recovering them. A week after the fire, team leader Bart Remes sent Del- Fly a 17-gram craft with a 28-centimetre wingspan, flapping up along the side of the building. At each floor, he paused it to peer in at the destruction through broken windows. When the DelFly was at the eighth floor, a crow dove from the roof and attacked it, slashing the thin Mylar film ofits wings and sending it tumbling down to the ground At first, Remes was shocked by the attack, but then he realized that the crow had given the Del- Fly the ultimate seal of approval. "It was quite impressive to see that nature itself thought we were part of nature," he says
The DelFly team is just one of a number around the world working to develop ever-smaller flying robots or unmanned aerial vehicles (UAvs). Some mimic insects. Others are minimized planes or helicopters. S others inspiration from seeds. Ultimately, these minimize flyers could investigate areas too dangerous for humans-burned-out buildings, collapsed mines, chemical spills and beam back valuable information.
But first, there are major design challenges to surmount. The DelFly team has made only partial progress towards its goal of a fully autonomous flyer that can survey the interior of an unknown building on its own. Using two mini-cameras one directed forwards and the other pointed downwards the DelFly II can avoid some obstacles by recognizing how far away they are and by following patterns on the ground, but it still requires significant human guidance via remote control
The cameras also help the craft to steady itself on turns without the use of an on-board gyroscope .The base controller performs all image processing, further m on-board burdens. "We try avoid adding extra components, which add more weight, consume more power and make the system more complex , says Rick Ruijsink, one of DelFly's developers.
Smaller than DelFly Il is DelFly Micro, weighing just over 3 grams ncluding a camera -and with a wingspan of just 10 centimetres. As crafts get smaller, maximizing efficiency becomes more critical and construction more difficult. Modeling of airflow around the wings also remains a challenge. The unusual "clap and fling" motion of the DelFlies, where a pair of wings on each side of the body meet each other and then flap apart, is especially difficult to model. So far, the Micro can fly forwards, but unlike the DelFly II it has yet to master hovering and flying backwards. "We hope to be able to do that this year," says Ruijsink