Sea Technology

DEC 2013

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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Ingvar Tjostheim / MoogFocaloferscombinatonunits thatincludeelectricalandfberpasses forthemarineindustry.Thissoluton isidealforremotelyoperated vehicles,winchesandsubsea equipment. TheModel176 electricalslipringis comprisedofpowerandsignal electricalpassesandprovides superiorperformanceandreliability indemandingenvironments. Designedforthemarineenvironment, theModel176ishighlyconfgurable andcanbecustomizedforspecifc applicatons. Integratedwithourfberoptcrotary jointsandfuidrotaryunions,the 176slipringcanprovideacomplete rotatnginterfacesoluton. Model 176 Electrical Slip Ring Features: • • • • • • • • Passesratedto5kV Stainlesssteelenclosure Sealedhousingdesign testedtoIP66standards Accommodatesvarious wireandcabletypes Maintenancefree operaton Optonalfameproof/ explosion-proofcapability HeathandUsage MonitoringSystemopton Pressurecompensated subseaopton Looking for more? Scan to view marine slip ring specifcatons. +1-902-468-2263 | 18 st / December 2013 for generating at-sea data to demonstrate relaxation in required pointing accuracy of the receiver and to validate the newly developed simulation tools. The two-axis scanned CW laser transmitter housing consists of a variable-power (20 to 800 milliwatts) single-mode, low-noise OEM 532-nanometer laser and a 5-millimeter, 2-axis galvanometer scanner with fast axis scan speeds up to 500 lines per second and a total optical scan angle of 60 degrees in both axes. For the results presented here, scan speeds of 500 lines per second, which are realistic for mobile platforms, were used. For our tests, the transmitters were deployed on a self-powered profling lander that comprises the laser transmitter mounted on a pan-tilt unit and a suite of optical sensors for inherent optical properties (IOP) and radiometry characterization. The lander sits on three folding legs for stability and to keep it above loose sediments, and can be tracked from the support vessel via acoustic positioning. The system can be controlled by acoustic modem from the support vessel to turn the transmitter on and off, modify scan job and laser power, adjust the pan-tilt unit and retrieve sensor samples. The PMT signals can be acquired on the surface vessel via a laptop connected to a digitizer for real-time image and data display. Initial experiments in summer 2012 with the prototype distributed serial laser imager were conducted in the large electro-optic turbidity test tank at Harbor Branch using a robotic positioning system. Three placements of the laser housing were used in these tests: beside the receiver (i.e., near-monostatic) 11 meters from the target, 5 meters in front of the receiver (6 meters from the target) and 7 meters in front of the receiver (4 meters from the target). One important observation is apparent in the clear water case, in which the shadow of the 19-centmeter-diameter laser housing is visible on the lower portion of the checker pattern, but diminishes as the scattering coeffcient increases. Because such a shadow could result from a small UUV deploying the transmitter, these results show that there will not be a signifcant problem with self-shading even in fairly clear water. The coastal Atlantic Ocean tests were performed 8 miles off Fort Pierce, Florida, at a depth of 18 meters. The surface vessel performed a series of passes over the lander to exercise orientation and distance between the transmitter and receiver in the horizontal axis, while continuously acquiring four-channel images up to the detection limit in order to determine the image acquisition range. The system operator could view the PMT signals being acquired and the waterfall images in real time. In addition to ensuring that the sensor parameters and system log of events were accurately synchronized, great care was taken to accurately measure the static and dynamic aspects of the test geometry and relevant environmental parameters (e.g., IOPs) so that the results can be used to validate the new radiative transfer code. For the multichannel imaging results, which were taken at dusk on September 20, 2012, the slant range between the target and the vessel-mounted receiver was 32 meters. This corresponds to almost 30 beam attenuation lengths between the target and the receiver. Image one was formed with the PMT assembly pointing downward, albeit with no direct overlap with the lander and its laser transmitter and technical target. Images two through four exhibit various levels of contrast between the near-feld and far-feld image, depending on the orientation of the lander and pointing di-

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