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FIGURE A - Click to Expand
FIGURE B - Click to Expand
FIGURE C - Click to Expand
FIGURE D - Click to Expand
ASC's dust penetrating 3D Flash LIDAR
- Initial pulse maps dust cloud surface ("hit" mode)
- Subsequent pulses interrogate within the dust cloud (SULAR mode)
- Range is provided to hazards and dust cloud
- Intensity map provides even more data for situational awareness
- TigerEye returns "hit" mode range, "SULAR" range and Intensity Map of field of view
3D Flash LIDAR Obscuration Penetration Tests
ASC 3D Flash LIDAR cameras have several operational modes implemented by means of the camera control software: the Trigger mode is where all pixels operate independently, a Delay-trigger mode where the Trigger mode is made operational only after a specified range and a Gated mode where the trigger is suppressed and the pulse sampling occurs in all pixels simultaneously (Figure A). This latter mode is appropriate for penetrating obscuration where the return from the obscuration surface could “trigger” all the pixels. This mode can be utilized during landing for dust, smoke or fog penetration. Notice the 10 degree diffuser being used with a 45 degree lens and the ability of the camera to image completely through 10 meters of dense artificial fog. The distance from the camera to the back wall was ~17.3 meters.
For the test in Figure A, we used artificial fog generated using vaporized water and a glycerin-based fluid injected into a heated block. It produced about ~3um sized vapor particles. The rolling door was closed completely and the fog machine was used for 15 minutes to create maximum saturation of the air. The test was begun by starting the 3D Flash LIDAR in Obscuration Penetration Mode and then the door was opened. The resulting visibility for the initial 2 minutes was reduced to less than 15cm inside the room. During the test, the wind was blowing from the right side of the picture across the front of the room at approximately 5kts per hour).
In a separate test, ASC created a tent that was 4 meters x 8 meters (narrow across the front opening). Shown in Figure B, the test used “corn starch” to simulate large dust particles (~15um) and inserted a “dummy” into the tent. This test was hazardous because of the fire potential caused by having a fine, flammable material (the corn starch dust) suspended in air. There was little wind for the Corn Starch Test.
In both cases, the terminal settling velocity of an aerosol or "artificial smoke" particle increases rapidly with particle size. The settling velocity is proportional to the square of the particle diameter. The settling velocity for the 3um artificial fog due to gravity is about 1000mm per hour. For the 15um cornstarch dust, it is about 33,000mm (33cm) per hour.
ASC performed 3 days of tests in Yuma, Arizona USA for helicopter brownout testing in April 2010. These tests (shown in Figure 10) were the most difficult because the particle sizes ranged from submicron (0.2um) to 80um for the small particles to small “pebbles” and “rocks” that were kicked up by the helicopter’s rotor blades. The ASC 3D Flash LIDAR cameras penetrated 50 meters to the requested targets (see insets in Figure C & D) and captured both range and intensity of the targets in real-time. It is possible to see the dust cloud developing in 3D.
Dust Penetration Testing at Yuma Proving Grounds
- Directed to monitor a target at 150 feet
- Used a TigerEye camera with external laser
- Camera imaged horizontally across dust clouds
- ASC 3D Flash LIDAR never lost sight of the target
- The TigerEye monitored the front of the dust cloud, as well as the target
- ASC 3D Flash LIDAR and software hold promise for brownout conditions
- Additional testing and exploitation recommended to create a deployment solution