Auv

The goal of this project was to improve UAV efficiency through use of biomimetic design. This was achieved through the application of a hydraulically actuated soft robotic fin. Drawing inspiration from the manta ray, a custom actuator was developed to achieve a feasible, lifelike locomotion method. The actuator was incorporated into a prototype robot to assess the performance and ease of integration.

There have been increased interests in the research on mechanical and control system of underwater vehicles in the recent past. These ongoing research efforts are motivated by more pervasive applications of such vehicles including seabed oil and gas explorations, scientific deep ocean surveys, military purposes, ecological and waters environmental studies, and also for entertainments. However, the performance of underwater vehicles with screw type propellers is not prospective in terms of its efficiency and maneuverability. The main weaknesses of this kind of propellers are the production of vortices and sudden generation of thrust forces which make the control of the position and motion difficult.
On the other hand, fishes and other aquatic animals are efficient swimmers, posses high maneuverability, are able to follow trajectories, can efficiently stabilize themselves in currents and surges, create less wakes than currently used underwater vehicle, and also have a noiseless propulsion. The fish’s locomotion mechanism is mainly controlled by its caudal fin and paired pectoral fins part. They are classified into BCF (Body and/or Caudal Fin) and MPF (Median and/or paired Pectoral Fins). The study of highly efficient swimming mechanisms of fish can inspire a better underwater vehicles thruster design and its mechanism.
There have not been many studies on underwater vehicles or fish robots using paired pectoral fins as thruster. The work presented in this paper represents a contribution in this area covering study, design and implementation of locomotion mechanisms of paired pectoral fins in a fish robot. The performance and viability of the biomimetic method for underwater vehicles are highlighted through in-water experiment of a robotic fish.

Underwater glider moves vertically by change in buoyancy and moves horizontally due to wings. In this paper, we validate the experimental lift and drag characteristics of a glider from the literature using Computational Fluid Dynamics (CFD) approach. This approach is then used for the assessment of the steady state characteristics of a glider under development. Flow behavior and lift and drag force distribution at different angles of attack are studied for Reynolds numbers varying from 105 to 106. The state variables of the glider are the velocity, gliding angle and angle of attack which are simulated by making use of the hydrodynamic drag and lift coefficients obtained from CFD. The effect of net change in buoyancy is examined in terms of the gliding angle, glider velocity, angle of attack and glider saw-tooth trajectory.

Autonomous Underwater Vehicles (AUVs) are robots able to perform tasks without human intervention
(remote operators). Research and development of this class of vehicles has growing, due
to the excellent characteristics of the AUVs to operate in different situations. Therefore, this study
aims to analyze turbulent single fluid flow over different geometric configurations of an AUV hull,
in order to obtain test geometry that generates lower drag force, which reduces the energy consumption
of the vehicle, thereby increasing their autonomy during operation. In the numerical
analysis was used ANSYS-CFX® 11.0 software, which is a powerful tool for solving problems involving
fluid mechanics. Results of the velocity (vectors and streamlines), pressure distribution
and drag coefficient are showed and analyzed. Optimum hull geometry was found. Lastly, a relationship
between the geometric parameters analyzed and the drag coefficient was obtained.

This work proposes a nonlinear suboptimal diving control scheme for autonomous underwater vehicles (AUVs) in presence of hydrodynamic parameter uncertainties and disturbance. The controller is designed via the state-dependent Riccati equation (SDRE) method that regulates the system’s states by minimization of the related quadratic cost function. To compensate the system’s restoring force (gravity/buoyancy), the common SDRE control law is supplemented with a discontinuous control law analogous to sliding surface notion. We applied the proposed controller to a well-known AUV model (REMUS). Simulation results demonstrate the effectiveness of the proposed controller under system’s parameter uncertainties and disturbance with appropriate regulation and tracking performance.

Recently problems requiring control unmanned underwater vehicles (UUV) at large angles of inclination (pitch and roll), become more frequent. Traditional attitude control systems use Euler angles. However, the performance of traditional systems decreases with the increasing of the tilt angles, which delays their use for new tasks. To solve this problem, stability analysis of the UUV's attitude control system according to the generalized Nyquist stability criterion is carried out. The analyses showed that the stability of the system depends on the UUV inclination along the roll. However, at large angles of inclination, the roll channel is subject to perturbations from the yaw and pitch channels. The roll control system synthesis is solved as the ∞-optimization problem with the requirements of low sensitivity to perturbations from other channels. The simulation results on the full non-linear UUV Aqua-MO model confirmed the efficiency of the approach in question and demonstrated the best quality in comparison with PD controller. The obtained stability condition and synthesis approach allow to expand the working angles and improve the quality of the existing UUV control systems. These results are useful for the development of new systems as well.

This paper presents the impact of introducing a two-controller on the linearized autonomous underwater vehicle (AUV) for vertical motion control. These controllers are presented to overcome the sensor noise of the AUV control model that effect on the tolerance and stability of the depth motion control. Linear quadratic Gaussian (LQG) controller is cascaded with AUV model to adapt the tolerance and the stability of the system and compared with FOPID established by the improved whale optimization algorithm (IWOA) to identify which controlling method can make the system more harmonize and tolerable. The developed algorithm is based on improving the original WOA by reshaping a specific detail on WOA to earn a warranty that the new IWOA will have values for the update position lower than the identified lower-bound (LB), and upper-bound (UB). Furthermore, the algorithm is examined by a set of test functions that include (unimodal, multimodal and fixed dimension multimodal functions). The ...

The fourth edition of the REP exercise, REP13, took place off the coast of Sesimbra, Portugal, but continued further south from the Portimãoairfield. It involved participants from the Portuguese Air Force Academy, MBARI (USA), University of California at Berkeley (USA), Evologics(DE), and the Norwegian University of Science and Technology (NOR). Several large and small propeller-driven ASVs, AUVs with different sensors and acoustic modems were deployed from NRP Bacamarte, a ship from the Portuguese Navy. Several drifters and fish tags were also deployed for estimating surface currents and for vertical profiling.

The benthic communities of the deep insular shelf at the Hind Bank marine conservation district (MCD), an important spawning aggregation site for groupers, were studied with the Seabed autonomous underwater vehicle (AUV) at depths between 32 and 54 m. Four digital phototransects provided data on benthic species composition and abundance of the insular shelf off St. Thomas, US Virgin Islands. Within the western side of the MCD, well-developed coral reefs with 43% mean living coral cover were found. The Montastrea annularis complex was dominant at all four sites between 33 and 47 m, the depth range where reefs were present. Maximum coral cover found was 70% at depths of 38--40 m. Quantitative determinations of sessile benthic populations, as well as the presence of motile megabenthic invertebrates and algae were obtained. The Seabed AUV provided new quantitative and descriptive information of a unique coral reef habitat found within this deeper insular shelf area.

Inverse simulation allows system inputs to be found to give model outputs that match required time histories. Examples include inputs needed for specific aircraft manoeuvres or movements of a robot arm and such cases lead to investigations that differ from conventional simulation studies. Inverse simulation has been used for aircraft and helicopter flight mechanics modelling for some time and provides alternatives to analytical methods of inverse modelling used in control applications. The approach is suitable for linear and nonlinear multi-input multi-output models as well as for single-input single-output descriptions. Methods include a so-called “differentiation” approach, techniques that are termed “integration” methods, approaches involving the solution of differential algebraic equations and a method based on feedback system principles. The feedback approach is given particular emphasis, through an example involving a dynamic model of an unmanned underwater vehicle.

A critical problem in planning sampling paths for autonomous underwater vehicles (AUVs) is correctly balancing two issues. First, obtaining an accurate scalar field estimation and second, efficiently utilizing the stored energy capacity of the sampling vehicle. Adaptive sampling approaches can only provide solutions when real time and a priori environmental data is available. In this paper we present an analysis of adaptive sampling methodologies for AUVs. In particular, we analyze various sampling path strategies including systematic and stratified random patterns within a wide range of sampling densities and their impact in the energy consumption of the vehicle through a cost-evaluation function. Our study demonstrates that a systematic spiral sampling path strategy is optimal for high-variance scalar fields for all sampling densities and low-variance scalar fields when sampling is sparse. In addition, our results show that the random spiral sampling path strategy is found to be optimal for low-variance scalar fields when sampling is dense.

Abstract The design, testing, and mission execution of a network of autonomous underwater vehicles (AUV) is a difficult process. The design of low-level controllers requires high-fidelity hydrodynamic models for simulation, but the testing of a large network of AUVs with high-...