Kent Rosser

Bioinspired optical sensors for unmanned aerial systems

Insects are dependant on the spatial, spectral and temporal distributions of light in the environment for flight control and navigation. This paper reports on flight trials of implementations of insect inspired behaviors on unmanned aerial vehicles. Optical flow methods for maintaining a constant height above ground and a constant course have been demonstrated to provide navigation capabilities that are impossible using conventional avionics sensors. Precision control of height above ground and ground course were achieved over long distances. Other vision based techniques demonstrated include a biomimetic stabilization sensor that uses the ultraviolet and green bands of the spectrum, and a sky polarization compass. Both of these sensors were tested over long trajectories in different directions, in each case showing performance similar to low cost inertial heading and attitude systems. The behaviors demonstrate some of the core functionality found in the lower levels of the sensorimotor system of flying insects and shows promise for more integrated solutions in the future.

Vertically displaced optical flow sensors to control the landing of a UAV

We report on an optical device to aid landing of Unmanned Aerial Systems. Optical flow calculates a measure of observed angular movement of the image seen by the sensor. Optical flow can be converted to range if speed of the sensor is known. Our approach eliminates this requirement by using two optical flow sensors displaced vertically to calculate range. The initial implementation was tested on an instrumented UAV with promising results. We show that the sensor provides useful range measurements at a height of several meters. We argue that this technique is comparable to vision techniques such as stereo in this application. We show alternate implementations with optics that do not require vertical displacement.

Autonomous Chemical Vapour Detection by Micro UAV

The ability to remotely detect and map chemical vapour clouds in open air environments is a topic of significant interest to both defence and civilian communities. In this study, we integrate a prototype miniature colorimetric chemical sensor developed for methyl salicylate (MeS), as a model chemical vapour, into a micro unmanned aerial vehicle (UAV), and perform flights through a raised MeS vapour cloud. Our results show that that the system is capable of detecting MeS vapours at low ppm concentration in real-time flight and rapidly sending this information to users by on-board telemetry. Further, the results also indicate that the sensor is capable of distinguishing “clean” air from “dirty”, multiple times per flight, allowing us to look towards autonomous cloud mapping and source localization applications. Further development will focus on a broader range of integrated sensors, increased autonomy of detection and improved engineering of the system.

Semiautomatic calibration and alignment of a low cost, 9 sensor inertial magnetic measurement sensor

As UAVs and sensor networks become ubiquitous, cost and accuracy will be increasingly traded. We have developed techniques for calibration that consider this problem. Our technique performs a nonlinear optimization through all variables associated with zeroth and first order affects on accuracy of the sensors. The optimization is constrained by the known properties of the magnetic and gravitational fields. A miniature autopilot is presented as an example of the pressing need for automation of calibration.

Flight Test of a Polarisation Compass Integrated into an Unmanned Aerial Vehicle Autopilot

Abstract We report on the first successful development and implementation of an automatic polarisation compass as the primary heading sensor for a UAV. Polarisation compassing is the primary navigation sense of many flying and walking insects, including bees, ants and crickets. Manually operated polarisation astrolabes were fitted in passenger airliners operating over the arctic prior to the implementation of the global positioning system, to compensate for the overall degradation of navigation sensors in polar regions. The device we developed demonstrated accurate determination of the direction of the Sun, with repeatability of better than 0.2 degrees. These figures are comparable to any solid state magnetic compass, including flux gate based devices. Flight trials were undertaken in which the output of the polarimeter was the only heading reference used by the aircraft as it flew GPS waypoints and fixed heading commands without GPS.