77 research outputs found
Development and integration of a novel IP66 Force Feedback Joystick for offshore operations
No full textIntervention activities in underwater environments are of great importance in many areas, such as the exploration, monitoring and documentation of sea resources, historical treasures or industrial applications. The use of robotic systems and automatic procedures is becoming fundamental, since the work conditions for divers are risky and often unfeasible, and several kind of works are every way impossible for humans. One of the most important objectives of the underwater robotic research consists in making technological systems friendly and easy to use by all kind of experts. This paper presents the development and test of a Force Feedback (FFB) Joystick aimed at supporting ROVs pilots during their work. Reaction forces on the joystick axes, based on specific error parameters, let the pilot understand in real-time the underwater environment where the robot is moving and thruster velocity saturation limits, thus improving significantly the efficiency of the given mission. The present work describes the design, assembly and programming of the joystick, and its test within a virtual environment simulating the real time control of Internet-enabled smart ROVs operating in remote locations. Results obtained with this kind of applications are discussed, and potentiality of the systems are underlined for future developments
A Decentralized Control Algorithm for Swarm Behavior and Obstacle Avoidance in Unknown Environments
No full textIn this paper a decentralized control algorithm for swarm behavior and obstacle avoidance in unknown environment is presented. The proposed technique is based on the concept of Null Space Based behavioral approach to merge different swarm tasks. In particular, the
algorithm focuses on the possibility of sharing sensors’ data in order to avoid obstacles that can be detected in the environment. The effectiveness of our approach is investigated by means of numerical simulations with different typology of environment
Preliminary study of a novel magnetic sensor for safety in industrial robotics
No full textIn this paper a novel magnetic sensor for industrial robotics is presented. The main aim of the sensor is to detect the presence of human beings in order to avoid the collision between workers and the robot. The sensor consists in such an artificial skin to conform at the robot shape, made by several turns of a wire covered by a dielectric. The sensor made in this way has no exposed metal parts, so it is safe from an electrical point of view and has no tips that could be caught up by surrounding objects. This sensor in mainly based to the magnetic field variation due to the presence of the target. At first, a laboratory prototype of this sensor was built to perform a preliminary set of measurements. Furtherly a prototype implementation was realized and tested in a realistic scenario
Thruster Fault Diagnosis and Accommodation for Overactuated Open-Frame Underwater Vehicles
No full text
Control Algorithm for Parallel Connected Offshore Wind Turbine Generators
No full textA control algorithm for Parallel Connected Offshore Wind Turbines with permanent magnet synchronous Generators (PCOWTG) is presented in this paper. The algorithm estimates the optimal collective speed of turbines based on the estimated mechanical power of wind turbines without direct measurement of wind speed. In the proposed topology of the wind farm, direct-drive Wind Turbine Generators (WTG) is connected to variable low-frequency AC Collection Grids (ACCG) without the use of individual power converters. The ACCG is connected to a variable low-frequency offshore AC transmission grid using a step-up transformer. In order to achieve optimum wind power extraction, the collective speed of the WTGs is controlled by a single onshore Back to Back converter (B2B). The voltage control system of the B2B converter adjusts voltage by keeping a constant Volt/Hz ratio, ensuring constant magnetic flux of electromagnetic devices regardless of changing system frequency. With the use of PI pitch compensators, wind power extraction for each wind turbine is limited within rated WTG power limits. Lack of load damping in offshore wind parks can result in oscillatory instability of PCOWTG. In this paper, damping torque is increased using P pitch controllers at each WTG that work in parallel with PI pitch compensators
SMART ROVLATIS: flexible survey platform for surface and Uunderwater operations
No full textThis paper describes a novel vehicle designed for operation flexibility in high-resolution near
seabed survey from shallow inshore waters out to the continental shelf edge. The vehicle can be operated
in surface tow or as a thrusted pontoon. With buoyancy module release the vehicle becomes neutrally
buoyant and is operated as a survey class remotely operated vehicle (ROV) depth rated to 1,000m. Special
features of the system include: deployment interoperability for small inshore boats and larger research
vessel; fault tolerant thruster control; novel high frequency short range sonar; onboard computer control
enabling real-time disturbance reaction; topside augmented reality system support. The paper includes test
results from the off shore sea trials with the ROVLATIS in March 2009
Improved real-time adaptive multi-sonar controller
No full textIn this thesis an adaptive automatic controller which precisely synchronizes the pinging sequence of
multiple sonar devices is described. The acquisition and fusion of multiple datasets from the same
seabed region has been proved to afford a better data analysis and interpretation, while their
combined analysis provides complimentary information that helps resolving ambiguities upon the
studied data. Moreover, the concurrent collection of datasets reduces the survey time and cost. The
interest of this study is the design, development and validation of a system which allows the
simultaneous operation of multiple high-frequency sonars. It employs previously acquired
bathymetric data (multiple depth measurements) to generate geo-referenced Digital Terrain Model
data-subsets on the fly. These are subsequently used to accurately predict the transmission-
reception timing of the payload sensor acoustic pulses by finding the intersection of the outer part
of their beams with the previously explored terrain. The distance from the devices to their
corresponding intersections are translated into travel time values. Using these times, the controller
synchronizes the trigger of the instruments in a non-interfering fashion. In addition, it reduces the
errors in the calculations normally associated with sensor misalignments and platforms movements.
The controller is transparent and modular (object-oriented), thus enabling ease of integration with
the existing systems and facilitating test, upgrade and/or change of different system modules
independently. Tests and simulations were carried out to evaluate the scheduler system
performance. In most cases, the algorithm can handle the maximum theoretically achievable ping
rate imposed by the device beam geometries. However, if the computational time exceeds a
threshold, the ping rate is reduced accordingly. As a consequence of this ping rate reduction the
platform speed must be reduced to maintain required survey resolution
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