Civil servant

Australian researchers have designed an unmanned aerial vehicle using low-cost systems, making it affordable for civil as well as military use.

The helicopter-like Mantis, designed by the Commonwealth Scientific and Industrial ResearchOrganisation (CSIRO), can be told in advance where to go and what to do, and will then launch, complete the task and return without further assistance.

The UAV could be used for tasks that may be dangerous for humans, like monitoring power lines, traffic and forest fires, and difficult jobs such as 3D site mapping and inspection of bridges and buildings. A swarm of vehicles could even be used to locate survivors during air sea rescue searches.

‘The major task in developing Mantis’, said Dr. Peter Corke of CSIRO Complex Systems Integration, ‘was to produce an inertial sensing system and a computer vision system to control and provide flight stability and to guide the aircraft.’

‘The inertial sensing system behaves somewhat like our inner ear, providing balance and indicating the orientation of the helicopter in the air. The instrument, custom developed by CSIRO, uses low-cost MEMS (Micro-Electro-Mechanical Systems) sensors and is fabricated from magnesium alloy and weighs only 75 g.’

‘This is much lighter than current technology and is one of the major reasons we were able to make the brains of the Mantis light enough to be carried by such a small helicopter’, Dr. Corke says.

The vision system uses two miniature cameras, and CSIRO-developed software running on a medium-powered onboard computer.

‘Just as we use our two eyes to estimate the distance of an object, the helicopter uses the data from the two cameras to estimate its height above ground, a very important thing to know.’

‘The on-board computer also observes the changes in the image over time and from this it estimates its speed over the ground’, says Corke.

While Mantis can connect with the global GPS network it is not solely reliant on a GPS signal for operation, reducing the cost of the design, adds Dr. Corke.

The military are also interested in UAVs, and this technology has received a lot of media attention this year. Dr. Corke says, ‘They have, however, generally used very precise GPS guidance equipment, which require an expensive unit onboard the aircraft as well as expensive equipment on the ground’.

‘While GPS may seem like an ideal technique to use, it has many drawbacks in practice, particularly in built environments near large structures which can obscure or reflect the signals from the GPS satellites.’

By reducing the weight of the computer system, the Mantis helicopter measures just 1.5m long and just over 50cm high.

On the web