In the next 12 months Australian researchers expect to fly and land an unmanned air vehicle that uses stereo imaging to replicate optic flow techniques used by insects for guidance and control at low speeds.
Insects are known to use optic flow, the rate of images passing their compound eyes, to determine speed and altitude. However, during approach and landing optic flow is not useful as most insects slow to a hover just prior to touch-down, bringing the image flow rate to zero.
The Brisbane based-University of Queensland researchers have already flown an unmanned rotorcraft at up to 27kt (50km/h) using optic flow but when applying this for landing, UAVs require a different solution. The flight used forward looking vision that employed a convex mirror to present to the imaging system a view of the ground that removed the flow gradient.
This gradient, a difference in the rate of flow of the ground dependent on its distance forward from the vehicle and caused by the forward looking view, causes problems for optic flow calculation.
The stereo imaging approach for UAV landing uses two convex mirrors to present two images, with no flow gradient, that can be compared when the rate of optic flow slows to almost zero. The calculation of the difference in those two images gives information on the speed and distance to the landing point in the last few seconds of flight.
"It's the same algorithm [for optic flow analysis and stereo image comparison]. Flights so far have been open loop, to obtain data, to collate information. Now we will close the loop to control the aircraft. That will happen over the next year," says University of Queensland's professor of visual neuroscience, Mandyam Srinivasan, speaking on 14 March at the 1st US-Asian demonstration and assessment of micro aerial and unmanned ground vehicle technology, held in Agra, India. Although the work is being carried out at the University of Queensland, the project is managed by the University of Maryland and funded by the US Army.
Source: FlightGlobal.com
