Hybrid enhanced and synthetic vision system architecture for rotorcraft operations

The ability to conduct rotorcraft search and rescue (SAR) operations can be limited by environmental conditions that affect visibility. Poor visibility compromises transit to the search area, the search for the target, descent to the site and departure from the search area. In a collaborative program funded by the Canadian Department of National Defence, CAE and CMC Electronics designed, and together with the Flight Research Laboratory of the National Research Council of Canada integrated and flight-tested an enhanced and synthetic vision system (ESVS) to examine the potential of the ESVS concept for SAR operations. The key element of the ESVS was a wide field-of-view helmet-mounted display (HMD) which provided a continuous field-of-regard over a large range of pilot head movements. The central portion of the display consisted of a head-slaved sensor image, which was fused with a larger computer generated image of the terrain. The combination of sensor (E) and synthetic (S) imagery into a hybrid system allows the accurate detection of obstacles with the sensor while the synthetic image provides a continuous high-quality image, regardless of environmental conditions. The synthetic image can also be generated at a high resolution, thereby providing a high-quality image over a large instantaneous field-of-view to support orientation and situation awareness more akin to flight in Visual Meteorological Conditions (VMC) than conventional Instrument Flight Rules (IFR) operations. Components of the proof-of-concept system included a daylight CCD camera, PC image generators, an onboard geographic database generated from Canadian Digital Elevation Data, a navigation system based on differential GPS, and a prototype HMD based on laser-illuminated ferro-electric LCDs. The exercise served to highlight issues of importance to the success of a hybrid system, including: image stability, differential system latencies, relative quality of E and S images and their effect on the fusion process, texture interactions between E and S images, and symbology integration. Test results obtained during 80 hours of flight-testing in the NRC Bell 205 were promising, and a second-generation architecture is being developed. This paper presents the architecture and component technologies of the ESVS 2000 TD, as well as lessons learned and future applications for the hybrid approach.