Friday 04 August, 2000
Flying Microbats
If you look up into the skies around Pasadena, California, you may see something flying which looks like a little bird, but is actually a miniature robot. The Microbat is the work of a team from the California Institute of Technology and the company Aerovironment. Their work to date has taken them to the final of the Technical Innovation Competition run by the influential American science magazine Discover. Science In Action's Molly Bentley spoke to Joel Grasmeyer, one of the team working on the project, about the design of the current model, and the ambitions of the team for the future application of their innovation.
Emulating Nature
During the development of the Microbat, the team took their inspirations from the world around them, believing that nature could potentially inspire their own designs. In fact, the initial approach to the project, as defined in the research group's abstract, is "to learn from nature". Joel Grasmeyer explains this inspiration:
"We originally got the ideas for this project by looking at some of the designs of nature - birds, bats and insects - because obviously nature does it very well. If you look at a hummingbird, it can hover in gusty wind conditions in front of a flower and stay perfectly still, and yet with those same wings and body it can fly all the way across the Gulf of Mexico."
The developers also have a respect for nature and are aware that what they have achieved is far less advanced than the natural world. When electrical engineer Yu-Chong Tai discussed the Microbat with Discover magazine, he told them:
"My team really understands how far we are behind nature. Nature had several hundred million years to perfect a flying machine. We've had only two."
How does it work?
The Microbat is 15 centimetres long and weighs just 11 grammes, but it can fly at a top speed of around 15 kilometres per hour. Despite this seemingly fragile makeup, Grasmeyer believes that the machine is both stable and strong:
"It's very stable and it's very strong. [The wings are] designed to deflect... If it was too stiff it wouldn't fly, and if it was too heavy it wouldn't fly."
The power behind the Microbat comes from a 1.5 volt nickel cadmium battery, similar to that used in many small electronic devices, and the motor is taken from a pager. Grasmeyer explains this further:
"We have a whole bunch of electronics that have been mutilated to build this bird, and then we built our own custom gearbox and transmission, which turns the rotary motion of the motor into an oscillating motion of the wings."
| "We originally got the ideas for this project by looking at some of the designs of nature" - Joel Grasmeyer | |
The flight of the Microbat does not always run smoothly. When demonstrated to Science In Action, the machine veered off course and crashed. However, these are early days for the Microbat, which is currently only a free-flight model. Due to its lightweight design, temperature variations and wind speed can drastically effect the flight path, and so it has to be "tweaked" every time it is flown. Grasmeyer compares this to a paper aeroplane:
"If you flew it without adjustments it might peel off to one side because of a natural warp in the paper. But then, if you start bending other parts of the surface or the tail control surfaces, you can get it to fly straight or to turn left or do anything you want it to."
The Future - Spy In The Sky?
The pitfalls of the Microbat as a free-flight machine are evident, but the work to date has convinced them of the feasibility of the basic design and concept. The team will be working on developing the Microbat over several years. They already know where they expect to be in one year's time, and where they want to be in the future.
"Our goal is to add remote control in the next year of work... The final goal, maybe five to ten years down the road, is to be able to fly one of these inside a building."
There are plenty of practical opportunities for the Microbat to be put to use in the future. It is said that the US government and Department of Defense are both looking into the use of miniature flying machines for use as airborne spies. However, the team behind the Microbat are keen to point out the humanitarian possibilities for their invention.
"The eventual goal is to fly maybe inside a damaged building after an earthquake to look for people that are trapped inside. You could go into a hostage situation with a little camera the size of a sugar cube on the nose and it would look ahead, maybe with a 45 degree angle of view."
To be able to use the Microbat in this way, the Microbat team have already made some cameras that weigh around 1 gramme and can send back live colour video to the controller. As Grasmeyer says:
"It's literally the fly on the wall!"
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| Micro Devices |
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The Tai Group at the California Institute of Technology identified the following MEMS (micro-electro-mechanical-system) devices for potential inclusion in the final microbat design:
Shear-stress sensors
Semiconductor Strain Gauges
MEMS Body/Wings:
Micro balloon actuators
MEMS Acoustic microphones
Visual Imager (Camera) |
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