State and Perspectives of Underwater Robotics - Role of Laboratory for Underwater Systems and Technologies

The state and perspectives of underwater robotics is presented. The role and achievements of Laboratory for underwater systems and technologies (LABUST) in this domain is described. Two LABUST projects are shortly described

3D Line Following for Unmanned Underwater Vehicles

When designing guidance controllers for unmanned underwater vehicles, an assumption is often made that the vessel operates at a constant depth. However, in many applications the desired depth often changes with the position of the vessel in the horizontal plane. This paper addresses the problem of three dimensional line following with the application to underactuated underwater vehicles. The problem is resolved by separating the desired line into two components. The main contribution of this paper is the design of 3D line following controllers for underactuated underwater vehicles. The control design is based on constant controlled surge speed and a simplifi ed decoupled model of an under water vehicle. Detailed design procedure is presented. The simulation results are obtained from a complex, coupled model, which proves that the proposed algorithm can be used on real vehicles

Identifikacija bespilotnih ronilica korištenjem postupka vlastitih oscilacija

Control of underwater vehicles is a challenging task since these systems demonstrate highly coupled and nonlinear behavior in uncertain and often unknown environment. In order to successfully design higher levels of control hierarchy, sufficiently accurate parameters of a mathematical model describing the vessel is required. These parameters vary significantly depending on the payload; hence conventional, time-consuming identification methods are tedious. This paper introduces a self-oscillation based method for determining inertia and drag parameters for underwater vehicles. The procedure is easily implementable in field conditions and gives satisfactory results. Both linear and nonlinear models of yaw, heave and surge degree of freedom can be identified. Experimental results obtained from yaw identification experiments on a real underwater vehicle will be presented. In addition to this, the same methodology will be used to determine which model describes the vehicle dynamics more suitably. Modifications of the proposed algorithm for systems with delays and discrete-time systems will be described, together with an estimate of parameter error bounds due to quantization levels.Upravljanje bespilotnim ronilicama predstavlja zahtjevan zadatak budući da ronilice pokazuju snažno spregnuto i nelinearno ponašanje u nepredvidljivim i često nepoznatim okruženjima. U svrhu uspješnog projektiranja viših razina u njihovoj upravljačkoj hijerarhiji, potrebno je dovoljno dobro poznavati parametre matematičkog modela plovila. Ovi se parametri mogu znatno mijenjati ovisno o opremi i drugim uvjetima tijekom misije, stoga su uobičajeni, vremenski zahtjevni identifikacijski postupci neprikladni. Članak opisuje postupak koji koristi vlastite oscilacije za određivanje inercije i otpornosti bespilotnih ronilica. Postupak je lako primjenjiv u terenskim uvjetima i daje zadovoljavajuće rezultate. Linearan i nelinearan model zaošijanja, zaranjanja i napredovanja mogu´ce je identificirati. U radu su prikazani eksperimentalni rezultati dobiveni na identifikacijskim ekperimentima zaošijanja na stvarnoj ronilici. Uz navedeno, ista metodologija je iskorištena za odlučivanje o modelu koji prikladno opisuje stvarnu ronilicu. U radu su opisane i preinake predloženog algoritma za sustave s transportnim kašnjenjem i diskretne sustave, kao i procjene pogrešaka u određivanju parametara koje su posljedica kvantizacije

Application of an ASV for Coastal Underwater Archaeology

Coastal underwater archaeological sites are by nature dynamic, and often subject to disturbance from the action of waves, currents, sediment, and human activity. The need to document such sites comprehensively, accurately, and quickly has been the driving force behind technological advances in predisturbance site mapping since the 1960s. Certain challenges remain constant: the need for technology to be affordable and robust, with efficient post-processing as well as data acquisition times. Non-engineers must be able to interpret the results and publish them according to archaeological conventions. Large ancient shallow water port sites, submerged settlements, and landscape surveys present additional difficulties because of the volume of data generated. In this paper we present results of two expeditions to map the submerged Herodian structures at Caesarea Maritima, Israel, using a robotic vehicle, the Autonomous Surface Vehicle (ASV) Pladypos, which was developed to address these challenges. This vehicle carries high-resolution imaging and remote-sensing tools to produce photomosaics and microbathymetry maps of the seafloor, as well as performing precise geo-referencing. The results were later integrated into a GIS

Application of Heterogeneous Robotic System for Underwater Oil Spill Scenario

The tragic Deepwater Horizon accident in the Gulf of Mexico in 2010 as well as the increase in deepwater offshore activity have increased public interest in counter-measures available for subsurface releases of hydrocarbons. To arrive at proper contingency planning, response managers urge for a system for instant detection and characterization of accidental releases. Along these lines, this paper describes the application of a heterogeneous robotic system of unmanned vehicles: autonomous underwater vehicle (AUV), unmanned surface vehicle (USV) and unmanned aerial vehicle (UAV) extended with the oil spill numerical modeling, visualisation and decision support capabilities. A first set of field experiments simulating oil spill scenarios with Rhodamine WT was held in Croatia during the early autumn 2014. and the second set of experiments were held in Spain during the summer 2015. The objectives of this experiment were to test: effectiveness of the system for underwater detection of hydrocarbons, heterogeneous multi-vehicle collaborative navigation and communication as well as decision support system, visualisation of the system components and detected spill

MECHANICAL DESIGN OF AN AUTONOMOUS MARINE ROBOTIC SYSTEM FOR INTERACTION WITH DIVERS

SCUBA diving, professional or recreational, remains one of the most hazardous activities known by man, mostly due to the fact that the human survival in the underwater environment requires use of technical equipment such as breathing regulators. Loss of breathing gas supply, burst eardrum, decompression sickness and nitrogen narcosis are just a few problems which can occur during an ordinary dive and result in injuries, long-term illnesses or even death. Most common way to reduce the risk of diving is to dive in pairs, thus allowing divers to cooperate with each other and react when uncommon situation occurs. Having the ability to react before an unwanted situation happens would improve diver safety. This paper describes an autonomous marine robotic system that replaces a human dive buddy. Such a robotic system, developed within an FP7 project “CADDY – Cognitive Autonomous Diving Buddy” provides a symbiotic link between robots and human divers in the underwater. The proposed concept consists of a diver, an autonomous underwater vehicle (AUV) Buddy and an autonomous surface vehicle (ASV) PlaDyPos, acting within a cooperative network linked via an acoustic communication channel. This is a first time that an underwater human-robot system of such a scale has ever been developed. In this paper, focus is put on mechanical characteristics of the robotic vehicles

Cooperative Robotics in Marine Monitoring and Exploration

Marine robotics play a great role in modern exploration of marine environments. The Laboratory for Underwater Systems and Technologies of the Faculty of Electrical Engineering and Computing of the University of Zagreb is involved in marine robotics research and is currently participating in a number of marine robotics related projects. This paper addressed the issue of using multiple cooperative marine robots (surface and underwater) for marine monitoring and exploration within the scope of CroMarX project. The project brings a new dimension to marine monitoring and exploration by introducing cooperative marine robots that increase operational efficiency. The main objective of the CroMarX project is to investigate and develop cooperative control algorithms in the area of marine robotics, taking into account both unmanned surface marine vehicles (USVs) and an unmanned underwater vehicle (UUV) for the purpose of marine monitoring and exploration

Underwater Object Tracking Using Sonar and USBL Measurements

In the scenario where an underwater vehicle tracks an underwater target, reliable estimation of the target position is required. While USBL measurements provide target position measurements at low but regular update rate, multibeam sonar imagery gives high precision measurements but in a limited field of view. This paper describes the development of the tracking filter that fuses USBL and processed sonar image measurements for tracking underwater targets for the purpose of obtaining reliable tracking estimates at steady rate, even in cases when either sonar or USBL measurements are not available or are faulty. The proposed algorithms significantly increase safety in scenarios where underwater vehicle has to maneuver in close vicinity to human diver who emits air bubbles that can deteriorate tracking performance. In addition to the tracking filter development, special attention is devoted to adaptation of the region of interest within the sonar image by using tracking filter covariance transformation for the purpose of improving detection and avoiding false sonar measurements. Developed algorithms are tested on real experimental data obtained in field conditions. Statistical analysis shows superior performance of the proposed filter compared to conventional tracking using pure USBL or sonar measurements

A Search Strategy and Vessel Detection in Maritime Environment Using Fixed-Wing UAVs

In this paper, we address the problem of autonomous search and vessel detection in an unknown GNSS-denied maritime environment with fixed-wing UAVs. The main challenge in such environments with limited localization, communication range, and the total number of UAVs and sensors is to implement an appropriate search strategy so that a target vessel can be detected as soon as possible. Thus we present informed and non-informed methods used to search the environment. The informed method relies on an obtained probabilistic map, while the non-informed method navigates the UAVs along predefined paths computed with respect to the environment. The vessel detection method is trained on synthetic data collected in the simulator with data annotation tools. Comparative experiments in simulation have shown that our combination of sensors, search methods and a vessel detection algorithm leads to a successful search for the target vessel in such challenging environments

THE INCIDENCE OF PERIPARTAL HYSTERECTOMY IN FIVE CROATIAN HOSPITALS DURING SIXTEEN-YEAR PERIOD

Uvod: Peripartalna histerektomija (PPH) najdramatičniji je kirurški zahvat u modernoj opstetriciji i obično se obavlja kada se konzervativnim mjerama nije uspjela postići kontrola krvarenja. Navodi se trend porasta učestalosti u razvijenim zemljama. Cilj rada: Odrediti učestalost PPH u pet hrvatskih bolnica tijekom dvaju osmogodišnjih razdoblja u odnosu prema načinu dovršenja porođaja. Metode: Retrospektivnom analizom prikupljeni su podaci iz pismohrana pet hrvatskih bolnica. U istraživanje su uključeni svi porođaji podijeljeni u dva osmogodišnja razdoblja, od 1998. do 2013. Rezultati: Od ukupno 153.302 porođaja tijekom obaju promatranih razdoblja u 70 (0,46‰) slučajeva učinjen je hitni PPH. PPH nakon vaginalnog porođaja u prvom razdoblju iznosio je 0,21‰, a u drugom razdoblju 0,16‰. Učestalost PPH nakon carskog reza u prvom razdoblju iznosio je 1,91‰, a u drugom razdoblju 2,04‰. Rasprava i zaključak: Nema porasta pojavnosti PPH usporedbom dvaju osmogodišnjih razdoblja premda postoji statistički značajan porast učestalosti carskog reza (s 14,2% na 16,0%). Carski je rez čimbenik rizika za PPHIntroduction: Peripartal hysterectomy (PPH) is a life saving surgical procedure that is performed when conservative measures fail to control bleeding. According to literature data there is an increase in incidence among developed countries. Aim: To define the rate of PPH during two eight-year periods in five Croatian hospitals in respect to mode of delivery. Methods: Patients data were collected retrospectively from the medical records of the five Croatian hospitals. We analyzed data from 1998 to 2013, and divided them in two eight-year periods. Results: In 70 cases out of 153,302 deliveries urgent PPH was performed. PPH after vaginal deliveries was found in 0.21‰ and 0.16‰ and PPH after caesarean section was 1.91‰ and 2.04‰ in the first and second period, respectively. Discussion and conclusion: There is no increase of PPH rate in the two analyzed periods, although there is a statistically significant increase of caesarean section rate. Caesarean section presents higher risk for PPH