RBF-based supervisor path following control for ASV with time-varying ocean disturbance

1028-1036A robust model-free path following controller is developed for autonomous surface vehicle (ASV) with time-varying ocean disturbance. First, the geometrical relationship between ASV and virtual tracking point on the reference path is investigated. The differentiations of tracking errors are described with the relative motion method, which greatly simplified the direct differential of tracking errors. Furthermore, the control law for the desired angular velocity of the vehicle and virtual tracking point are built based on the Lyapunov theory. Second, the traditional proportional-integral-derivative (PID) controller is developed based on the desired velocities and state feedback. The radial basic function (RBF) neural network taking as inputs the desired surge velocity and yaw angular velocity is developed as the supervisor to PID controller. Besides, RBF controller tunes weights according to the output errors between the PID controller and supervisor controller, based on the gradient descent method. Hence, PID controller and RBF supervisor controller act as feedback and feed forward control of the system, respectively. Finally, comparative path following simulation for straight path and sine path illustrate the performance of the proposed supervisor control system. The PID controller term reports loss of control even in the unknown disturbance

Underwater dual manipulators-Part I: Hydrodynamics analysis and computation

1098-1103This paper introduces two 4-DOF underwater manipulators mounted on autonomous underwater vehicle (AUV) with grasping claws, such that the AUV can accomplish the underwater task by using dual manipulators. Mechanical design of the manipulator is briefly presented and the feature of the simple structure of dual manipulators is simulated by using Solid Works. In addition, the hydrodynamics of the manipulator is analyzed, considering drag force, added mass and buoyancy. Then, hydrodynamic simulations of the manipulator are conducted by using 3-D model with Adams software, from which the torque of each joint is calculated. This paper presents an integrated result of computed torques by combining the theoretical calculation and simulation results, which is instrumental in determining the driving torque of the manipulators

Underwater dual manipulators-Part II: Kinematics analysis and numerical simulation

1104-1112This paper introduces dual-arm underwater manipulators mounted on an autonomous underwater vehicle (AUV), which can accomplish the underwater handling task. Firstly, the mechanical structure of the dual-arm system is briefly introduced, wherein each 4-DOF manipulator has an additional grasping function. In addition, the kinematics model of the manipulator is derived by using the improved D-H method. Secondly, the working space of the underwater dual-arm system is analyzed, which is obtained by using Monte Carlo method. The cubic polynomial interpolation and the five polynomial interpolation trajectory planning methods are compared in the joint space. Finally, with the help of the Robotics Toolbox software, the numerical test is conducted to verify the functions of the underwater dual-arm manipulator system

Cooperative Acoustic Navigation Scheme for Heterogenous Autonomous Underwater Vehicles

International audienceCooperative Acoustic Navigation Scheme for Heterogenous Autonomous Underwater Vehicle

An integrated, self-contained microfluidic cassette for isolation, amplification, and detection of nucleic acids

A self-contained, integrated, disposable, sample-to-answer, polycarbonate microfluidic cassette for nucleic acid-based detection of pathogens at the point of care was designed, constructed, and tested. The cassette comprises on-chip sample lysis, nucleic acid isolation, enzymatic amplification (polymerase chain reaction and, when needed, reverse transcription), amplicon labeling, and detection. On-chip pouches and valves facilitate fluid flow control. All the liquids and dry reagents needed for the various reactions are pre-stored in the cassette. The liquid reagents are stored in flexible pouches formed on the chip surface. Dry (RT-)PCR reagents are pre-stored in the thermal cycling, reaction chamber. The process operations include sample introduction; lysis of cells and viruses; solid-phase extraction, concentration, and purification of nucleic acids from the lysate; elution of the nucleic acids into a thermal cycling chamber and mixing with pre-stored (RT-)PCR dry reagents; thermal cycling; and detection. The PCR amplicons are labeled with digoxigenin and biotin and transmitted onto a lateral flow strip, where the target analytes bind to a test line consisting of immobilized avidin-D. The immobilized nucleic acids are labeled with up-converting phosphor (UCP) reporter particles. The operation of the cassette is automatically controlled by an analyzer that provides pouch and valve actuation with electrical motors and heating for the thermal cycling. The functionality of the device is demonstrated by detecting the presence of bacterial B.Cereus, viral armored RNA HIV, and HIV I virus in saliva samples. The cassette and actuator described here can be used to detect other diseases as well as the presence of bacterial and viral pathogens in the water supply and other fluids

Meta-analysis Followed by Replication Identifies Loci in or near CDKN1B, TET3, CD80, DRAM1, and ARID5B as Associated with Systemic Lupus Erythematosus in Asians

Systemic lupus erythematosus (SLE) is a prototype autoimmune disease with a strong genetic involvement and ethnic differences. Susceptibility genes identified so far only explain a small portion of the genetic heritability of SLE, suggesting that many more loci are yet to be uncovered for this disease. In this study, we performed a meta-analysis of genome-wide association studies on SLE in Chinese Han populations and followed up the findings by replication in four additional Asian cohorts with a total of 5,365 cases and 10,054 corresponding controls. We identified genetic variants in or near CDKN1B, TET3, CD80, DRAM1, and ARID5B as associated with the disease. These findings point to potential roles of cell-cycle regulation, autophagy, and DNA demethylation in SLE pathogenesis. For the region involving TET3 and that involving CDKN1B, multiple independent SNPs were identified, highlighting a phenomenon that might partially explain the missing heritability of complex diseases

Contrôle coordonné de flottille de véhicules sous-marins sous-actionnés autonomes (AUVs)

Cette thèse traite de la question du contrôle du mouvement d'engins non-holonomes et sous-actionnés évoluant de manière coordonnée et autonome. Les différentes approches considérées sont le suivi de trajectoire (Trajectory Tracking TT) et le suivi de chemin (path following PF). Une nouvelle méthode de contrôle est proposée. Dénommée Path-Tracking (PT), elle permet de cumuler les avantages de chacune des deux précédentes méthodes, permettant de cumuler la souplesse de la convergence induite par le suivi de chemin avec le respect des contraintes temporelles du suivi de trajectoire. L'étude et la réalisation de la commande démarre avec l'étude du cas du robot nonholonome de type Unicycle' et se base sur les principes de Lyapunov' et de Backstepping'. Ces premiers résultats sont ensuite étendus au cas d'un véhicule sous-marin sous-actionné de type AUV (Autonomous Underwater Vehicle'), en analysant les similarités cinématiques entre ces deux types de véhicules. De plus, il est montré la nécessité de prendre en compte les propriétés dynamiques du système de type AUV, et la condition de Stern dominancy' est établie de façon à garantir que le problème est bien posé et ainsi que la commande soit aisément calculable. Dans la cas d'un système marin sur-actionné, qui peut ainsi effectuer des tâches de navigation au long cours et de positionnement désiré (Station keeping'), une commande hybride est proposée. Enfin, la question du contrôle coordonné d'une formation d'engins marin est abordée. Les colutions de commande pour les taches de suivi de chemin coordonné (coordinated path following') et de coordinated path tracking' sont proposées. Les principes du leader-follower' et la méthode des structures virtuelles sont ainsi traitées dans un cadre de contrôle centralisé, et le cas décentralisé est traité en utilisant certains principes de théorie des graphes.In this dissertation, the problems of motion control of underactuated autonomous vehicles are addressed,namely trajectory tracking (TT), path following (PF), and novelly proposed path tracking whichblending the PF and TT together in order to achieve smooth spatial convergence and tight temporalperformance as well.The control design is firstly started from the benchmark case of nonholonomic unicycle-type vehicles,where the Lyapunov-based design and backstepping technique are employed, and then it is extendedto the underactuated AUVs based on the similarity between the control inputs of two kinds of vehicles.Moreover, dealing with acceleration of side-slip angle is highlighted and stern-dominant property of AUVsis standing out in order to achieve well-posed control computation. Transitions of motion control fromunderactuated to fully actuated AUVs are also proposed.Finally, coordinated formation control of multiple autonomous vehicles are addressed in two-folds,including coordinated paths following and coordinated paths tracking, based on leader-follower andvirtual structure method respectively under the centralized control framework, and then solved underdecentralized control framework by resorting to algebraic graph theory

Dynamic Response of a SPAR-Type Floating Wind Turbine Foundation with Taut Mooring System

Compared with the traditional catenary or semi-taut mooring lines, the taut mooring system is more advantageous in many aspects, such as reduction of mooring line loads, erosion and fatigue damage during the powering productions of the floating wind turbines. This paper presents a taut mooring system made of synthetic fiber mooring lines, which can experience large elongations for a spar-type floating wind turbine. A finite element method (FEM)-based tensile mooring line model is proposed to study the mooring statics and dynamics of the floating wind turbine. A time domain modelling method coupled with the developed mooring line model is adopted to study the dynamics of a spar-type floating wind turbine foundation moored by the taut mooring system under regular waves. A systematic dynamic response and structural analysis are conducted based on variations in the mooring length and pretension. Additionally, comparative performance analyses are investigated for two mooring configurations with different numbers of mooring lines: two-point and three-point taut mooring system. It is found that factors, such as mooring length, pretension and the number of mooring lines, have significant impact on the in-plane and out-of-plane motion responses of the foundation

Underwater dual manipulators-Part II: Kinematics analysis and numerical simulation

This paper introduces dual-arm underwater manipulators mounted on an autonomous underwater vehicle (AUV), which can accomplish the underwater handling task. Firstly, the mechanical structure of the dual-arm system is briefly introduced, wherein each 4-DOF manipulator has an additional grasping function. In addition, the kinematics model of the manipulator is derived by using the improved D-H method. Secondly, the working space of the underwater dual-arm system is analyzed, which is obtained by using Monte Carlo method. The cubic polynomial interpolation and the five polynomial interpolation trajectory planning methods are compared in the joint space. Finally, with the help of the Robotics Toolbox software, the numerical test is conducted to verify the functions of the underwater dual-arm manipulator system

Numerical study on hydrodynamic performance of ducted propeller based on improved body force model

ObjectivesThe paper aims to solves the limitations of the Goldstein body force method in a hydrodynamic simulation of a ducted propeller. MethodsAn analysis of the reason for the distortion of the duct hydrodynamic simulation is carried out based on the wing theory, and a correction method based on the mass flow and body force distribution model is proposed. The RANS method is then used to study the simulation accuracy of two kinds of improved body force method. ResultsThe results show that the average relative error of the total thrust coefficient of the two improved body force methods under open water conditions is about 5%. The average relative error of the resultant forward force of the two improved volume force methods behind the underwater vehicle are 1.8% and 11.6% respectively. ConclusionsThe simulation accuracy of a ducted propeller based on the improved body force method in open water and behind an underwater vehicle is greatly improved compared with the traditional method. The proposed method can accurately simulate the hydrodynamic performance of a ducted propeller, laying the foundation for the efficient dynamic maneuverability simulation of underwater vehicles