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<title>Engineering &amp; Instrumentation</title>
<link href="http://drs.nio.org/drs/handle/2264/4" rel="alternate"/>
<subtitle/>
<id>http://drs.nio.org/drs/handle/2264/4</id>
<updated>2017-07-09T18:05:14Z</updated>
<dc:date>2017-07-09T18:05:14Z</dc:date>
<entry>
<title>Seabed resident event driven profiling system (SREP). Concept, design and tests</title>
<link href="http://drs.nio.org/drs/handle/2264/5070" rel="alternate"/>
<author>
<name>Mascarenhas, A.A.M.Q.</name>
</author>
<author>
<name>Afzulpurkar, S.</name>
</author>
<author>
<name>Maurya, P.K.</name>
</author>
<author>
<name>Fernandes, L.</name>
</author>
<author>
<name>Madhan, R.</name>
</author>
<author>
<name>Desa, E.S.</name>
</author>
<author>
<name>Dabolkar, N.A.</name>
</author>
<author>
<name>Navelkar, G.S.</name>
</author>
<author>
<name>Naik, L.</name>
</author>
<author>
<name>Shetye, V.G.</name>
</author>
<author>
<name>Shetty, N.B.</name>
</author>
<author>
<name>Prabhudesai, S.P.</name>
</author>
<author>
<name>Nagvekar, S.</name>
</author>
<author>
<name>Vimalakumari, D.</name>
</author>
<id>http://drs.nio.org/drs/handle/2264/5070</id>
<updated>2017-02-14T21:30:16Z</updated>
<published>2016-01-01T00:00:00Z</published>
<summary type="text">Seabed resident event driven profiling system (SREP). Concept, design and tests
Mascarenhas, A.A.M.Q.; Afzulpurkar, S.; Maurya, P.K.; Fernandes, L.; Madhan, R.; Desa, E.S.; Dabolkar, N.A.; Navelkar, G.S.; Naik, L.; Shetye, V.G.; Shetty, N.B.; Prabhudesai, S.P.; Nagvekar, S.; Vimalakumari, D.
The seabed resident event driven profiling system (SREP) described here offers a novel, optimized approach to profiling in coastal waters from seabed to sea surface during the rough seas encountered in the southwest monsoon season (June-Sept). It consists of a winch system and a tethered instrumented profiler. The winch system launches and retrieves the profiler. The tethered profiler is programmed to move up and down the water column to sample and transmit water column properties when it reaches the sea surface. It uses standard oceanographic sensors to measure vertical structure at ~0.25m resolution. The major challenges addressed in this paper are long endurance of three months, underwater acoustic communications between the sea bed and the profiler unit and data transmission by the profiler to the shore
</summary>
<dc:date>2016-01-01T00:00:00Z</dc:date>
</entry>
<entry>
<title>Range-based underwater vehicle localization in the presence of unknown ocean currents: Theory and experiments</title>
<link href="http://drs.nio.org/drs/handle/2264/4927" rel="alternate"/>
<author>
<name>Bayat, M.</name>
</author>
<author>
<name>Crasta, N.</name>
</author>
<author>
<name>Aguiar, A.P.</name>
</author>
<author>
<name>Pascoal, A.M.</name>
</author>
<id>http://drs.nio.org/drs/handle/2264/4927</id>
<updated>2016-05-02T21:31:23Z</updated>
<published>2016-01-01T00:00:00Z</published>
<summary type="text">Range-based underwater vehicle localization in the presence of unknown ocean currents: Theory and experiments
Bayat, M.; Crasta, N.; Aguiar, A.P.; Pascoal, A.M.
This paper addresses the problem of range-based autonomous underwater vehicle (AUV) localization in the presence of unknown ocean currents. In the setup adopted, the AUV is equipped with an attitude and heading reference system, a depth sensor, and an acoustic device that provides measurements of its distance to a set of stationary beacons. We consider the situation where the number of active beacons is not known in advance and may vary with time. The objective is to simultaneously localize the AUV and beacons, that is, to find their positions underwater. We start by deriving conditions under which it is possible to reconstruct the initial condition of the system under study. We consider the design model where the states evolve continuously with time, but the range measurements are only available at discrete instants of time, possibly in a nonuniform manner. For trimming maneuvers that correspond to AUV trajectories with constant linear and angular velocities expressed in the body frame, we show that if either the position of one of the beacons or the initial position of the AUV is known, then even without depth information the system is weakly observable (i.e., the set of states that are indistinguishable from a given initial configuration contains only a set of finite isolated points). If depth measurements are also available, then the system is observable even in the presence of unknown constant ocean currents. Equipped with these results, we then propose a novel observer for simultaneous AUV and beacon localization. The mathematical setup exploited borrows from minimum-energy estimation theory applied to continuous-time processes with discrete measurements, projection filters, and multiple-model estimation techniques. Convergence analysis of the resulting observer system yields conditions under which the estimation errors converge to a small neighborhood of the origin (whose size depends on the magnitude of the process and measurement noise). The results of field experiments with a robotic marine vehicle show the efficacy of the simultaneous AUV/multiple beacon localization system proposed
</summary>
<dc:date>2016-01-01T00:00:00Z</dc:date>
</entry>
<entry>
<title>Complementary terrain/single beacon-based AUV navigation</title>
<link href="http://drs.nio.org/drs/handle/2264/4806" rel="alternate"/>
<author>
<name>Maurya, P.</name>
</author>
<author>
<name>Curado, T.F.</name>
</author>
<author>
<name>António, P.</name>
</author>
<id>http://drs.nio.org/drs/handle/2264/4806</id>
<updated>2016-05-02T21:30:37Z</updated>
<published>2015-01-01T00:00:00Z</published>
<summary type="text">Complementary terrain/single beacon-based AUV navigation
Maurya, P.; Curado, T.F.; António, P.
This paper describes work done towards the development of advanced geophysical-based navigation systems for autonomous underwater vehicles (AUVs). The specific problem that we tackle is that of combining terrain-aided navigation (TAN) with single-beacon navigation (SBN) techniques. The resulting complementary TAN/SBN system has the potential to overcome some of the problems that arise with TAN navigation only, when an AUV undergoes motions that lead it temporarily across areas where the terrain below is not sufficiently "rich" in terms of topographic features. The key contribution of this paper is a formal analysis of the benefits of using complementary filtering, in opposition to TAN navigation only. To this effect, we exploit key tools of estimation theory, and in particular the Cramér-Rao lower bound inequality to obtain a lower bound on the minimum covariance of the estimation error that can be obtained with any unbiased estimator. For a real terrain profile we compute and compare the Cramér-Rao lower bounds for TAN only and TA/SB-based navigation. The increase in the expected performance that can be achieved with the second solution is clearly visible. The efficacy of the new solution proposed is illustrated with the help of computer simulations
</summary>
<dc:date>2015-01-01T00:00:00Z</dc:date>
</entry>
<entry>
<title>Effect of wind turbine on TLP flating platform response</title>
<link href="http://drs.nio.org/drs/handle/2264/4786" rel="alternate"/>
<author>
<name>Chodnekar, Y.P.</name>
</author>
<author>
<name>Mandal, S.</name>
</author>
<author>
<name>Rao, K.B.</name>
</author>
<id>http://drs.nio.org/drs/handle/2264/4786</id>
<updated>2016-05-02T21:30:29Z</updated>
<published>2015-01-01T00:00:00Z</published>
<summary type="text">Effect of wind turbine on TLP flating platform response
Chodnekar, Y.P.; Mandal, S.; Rao, K.B.
Ever increasing population of India demands high production of electrical energy which puts immense pressure on our limited stock of non-renewable sources of energy and makes us dependent over imports from foreign countries. The present study focuses on the innovative concept of renewable offshore wind energy wherein the hydrodynamic analysis of Tension Leg Platform (TLP) Floating Offshore Wind Turbine (FOWT) which supports 5MW wind turbine tower is carried out using ‘ANSYS Workbench 14.5’. The six degree responses of the structure are obtained in operational conditions considering rated wind velocity of 11.4m/s in an irregular wave environment. Two cases are mainly considered, the first-one with incident wave and wind combined action along 0degree (case 1) and the second–one with incident wave and wind combined action along 45degree (case 2). The effect of wind turbine on TLP responses is compared in between 10 different geometric models; 5 models (A’, B’, C’, D’, E’) considering only the TLP platform and 5 models (A, B, C, D, E) considering the same platforms along with wind turbine tower. It is observed that TLP FOWT has higher translational motions (surge, sway, and heave) as compared to rotational motions (roll, pitch, and yaw). The metacentric height improves drastically after adding weight to concrete ballast. Higher reserve buoyancy helps reduce surge, sway, roll and yaw. The direction of the incident wave and wind does not affect heave response and remains same when incident wave and wind acts at 0degree or 45degree. Higher reserve buoyancy increases pitch response only when incident wave and wind is acting at 0degree but the reverse effect is observed when incident wave and wind is acting at 45degree
</summary>
<dc:date>2015-01-01T00:00:00Z</dc:date>
</entry>
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