A robotic insect with four wings is the first to be able to control itself in all three axes of movement like a bee. The inventors hope it may be useful for rescue operations, or probing dangerous environments, but landing on the ceiling like a fly is still beyond its reach.
Conquering flight has been a human obsession since the ancient Greeks and myth of Icarus. We have been able to get off the ground with fixed wings in airplanes, hovered with rotating wings in helicopters and even managed to build devices that take to the air with flapping wings
But imitating the flight of insects has been a huge engineering challenge.
Anyone who has tried to swat a fly or mosquito knows how manoeuvrable flying insects are, with the ability to fly forwards, quickly change direction, hover and even fly backwards with ease.
Modern drones can accomplish many of those feats, but they use propellers and are quite large. Achieving that using flapping wings on an insect scale has been difficult because micro-robots must be lightweight while incorporating motors that drive and control the wings.
Researchers at Washington State University have built a mechanical bee about the size of a thumb that uses four carbon fibre and Mylar wings that are individually controlled and beat at 100 to 160 beats per second.
WATCH: High speed video of flies manoeuvring to land upside down on a surface. Courtesy Science
It is the first robotic insect to fly to have control of pitch, roll and yaw in the same way that insects do to fly straight up and down, hover, move forward, back, and side to side. In aerodynamics, pitch is analogous to what you do with your head when you nod up and down saying yes; roll is when you tilt your head side to side to suggest “I don’t know,” and yaw is moving your head side to side to convery “no”.
For the researchers designing the robot, yaw was the most difficult to achieve because the movements of all four wings had to be closely coordinated. They must flap back and forth to produce lift, and angle to produce the twisting yaw motion at the same time.
This experimental prototype is still tethered by a wire for power. But now that the flight control has been achieved we may see future robotic insects enter collapsed buildings to search for survivors, survey hazardous areas or possibly even perform artificial pollination.
Taking a lesson from nature is common in science, usually with the knowledge that nature is much better at it than we are. And there is still one manoeuvre where the insects outperform the robots. They can land on the ceiling.
For many years there was an unsolved mystery of how flies can turn themselves upside down to land on a ceiling. It’s a feat that requires lightning fast movement and coordination that was very difficult to observe.
Now, thanks to high speed photography, the mystery has been solved.
It turns out that the insects don’t actually fly upside down to do it. They can use a couple of different methods. One of the ones recorded involved reaching up over their heads with their front legs as they approached the ceiling, grabbing on, and using momentum to swing their bodies upwards in a half backflip. The fly has to coordinate this in 50 milliseconds — much faster than the blink of an eye.
That means a robot would have to coordinate its wings and legs to accomplish the same stunt.
Of course nature has had millions of years of evolution to perfect things like insect flight. So there is still some work to do before we completely catch up.