EADS Germany is the world market leader in commercial and military Helicopter Laser Radar (HELLAS) Obstacle
Warning Systems. The HELLAS-Warning System has been introduced into the market in 2000, is in service at German
Federal Police and Royal Thai Air Force. HELLAS was also successfully evaluated by the Foreign Comparative Test
Program (FCT) of the U.S. Army and other governmental agencies.
Currently the successor system for military applications, HELLAS-Awareness, is in qualification phase. It will have
extended sensor performance, enhanced real-time data processing capabilities and advanced human machine interface
(HMI) features. Flight tests on NH90 helicopter have been successfully performed. Helicopter series integration is
scheduled to begin from 2009. We will give an outline of the new sensor unit concerning detection technology and
helicopter integration aspects. The system provides a widespread field of view with additional dynamic line of sight
steering and a large detection range in combination with a high frame rate. We will show the HMI representations.
This HELLAS system is the basis for a 3 dimensional see-and-remember-system for brown-out recovery. When landing
in sandy or dusty areas the downwash of the helicopter rotor causes clouds of visually-restrictive material that can
completely obstruct the pilot's outside reference, resulting in a complete loss of situational awareness and spatial
orientation of the pilot which can end up in total loss of aircraft control and dangerous accidents. The brown-out
recovery system presented here creates an augmented enhanced synthetic vision of the landing area with the surrounding
which is based on HELLAS range image data as well as altimeter and inertial reference information.
EADS Germany is the world market leader in commercial Helicopter Laser Radar (HELLAS) Obstacle Warning Systems. The HELLAS-Warning System has been introduced into the market in 2000, is in service at German Border Control (Bundespolizei) and Royal Thai Airforce and is successfully evaluated by the Foreign Comparative Test Program (FCT) of the USSOCOM. Currently the successor system HELLAS-Awareness is in development. It will have extended sensor performance, enhanced realtime data processing capabilities and advanced HMI features. We will give an outline of the new sensor unit concerning detection technology and helicopter integration aspects. The system provides a widespread field of view with additional dynamic line of sight steering and a large detection range in combination with a high frame rate of 3Hz. The workflow of the data processing will be presented with focus on novel filter techniques and obstacle classification methods. As commonly known the former are indispensable due to unavoidable statistical measuring errors and solarisation. The amount of information in the filtered raw data is further reduced by ground segmentation. The remaining raised objects are extracted and classified in several stages into different obstacle classes. We will show the prioritization function which orders the obstacles concerning to their threat potential to the helicopter taking into account the actual flight dynamics. The priority of an object determines the display and provision of warnings to the pilot. Possible HMI representation includes video or FLIR overlay on multifunction displays, audio warnings and visualization of information on helmet mounted displays and digital maps. Different concepts will be presented.
Although much research has been done on fiber-optic gyroscopes
(FOG), these sensors often show bias errors, i.e. the offset
rotation rate varies with temperature and other environmental
parameters. A low coherence light source is used to avoid
undesirable interferences between error signals. Nevertheless in
the standard FOG design it is possible that unintentionally
optical paths match which may cause bias errors. The parasitic
interferences may originate from reflections and polarization
cross-coupling, whether intended or not. A new simulation tool for
modeling interferometric fiber optic sensors with inclusion of
polarization and coherence effects is presented. It allows for the
first time to model the FOG signal quantitatively considering
temperature dependence, light source parameters and all
perturbations and interferences between them with the
corresponding degree of coherence. An analysis of the gyroscope
design is made which leads to a localization of a bias error
source which has not been described yet. This problem may occur in
every FOG with an integrated optics circuit (IOC) and a Lyot
depolarizer. Reflection paths from the IOC match phase differences
gained in the depolarizer and lead to temperature dependent bias
errors. Guidelines for an optimum design avoiding the perturbing
interferences are given.
The nonlinear effect in a fiber-optic gyroscope has been measured with a single mode laser diode, a multi mode laser diode with an erbium-doped fiber amplifier and an erbium-doped fiber source. The experimental results confirm the estimations obtained from our improved theoretical treatment. The predicted dependency on the number of spectral lines and their power has been observed. The maximum phase error per power difference in the sensing coil is 1.3 μrad/μW corresponding to a rotation rate error of 0.3(°/h)/μW. The use of the multi mode laser diode reduces the errors by a factor of 5 according to its spectral shape. For the broadband erbium-doped fiber source the effect is zero within the error ranges. These theoretical and experimental results contradict predicted nonlinear gyro errors derived in literature.