Giuliana Mattiazzo

ISWEC: Design of a prototype model with gyroscope

The extraction of energy from ocean waves has been investigated in Europe since the 1970s. Hundreds of devices have been proposed, many have been tested in some form or other and a few of these have been commercialized. In this paper a gyroscopic wave energy converter is studied and a procedure to design a prototype model to be tested at the wave tank at the University of Edinburgh is outlined. A linearized model of the device is extrapolated and used as a mathematical tool in the design process. The final version of the prototype model is verified using the complete nonlinear model.

Control of a six-axis pneumatic robot

The article presents a control system for a six-degree of freedom (DOF) anthropomorphic robot powered entirely by pneumatic actuators. The control uses digital valves driven by pulse width modulation (PWM) to regulate air flow to the actuators. The robot is equipped with position sensors, which are used to provide feedback signals for local fuzzy controllers actuating the individual servoaxes. Trajectory tracking is guided by a module, which computes the robots inverse kinematics, generating the references for the servoaxes. Experimental results illustrated in the article indicate that the controller is effective both in controlling single axes, and in tracking a trajectory.

Numerical Model of an Air-jet Loom Main Nozzle for Drag Forces Evaluation

The flow field inside an air-jet loom main nozzle is studied numerically, by means of a two-dimensional model implemented in the commercial computational fluid dynamics (CFD) code Fluent. In order to determine which physical model could allow a better prediction of the nozzle behavior, preliminary simulations were carried out on a basic geometry configuration, changing flow models and comparing results with available experimental data. Having done the model setup, simulations aimed at evaluating drag force on the weft yarn were performed on various geometry configurations; in particular, the influence of acceleration tube length, shape and size on drag force was evaluated. Results gave some guidelines for future prototyping and experimentation.

A fuzzy controlled pneumatic gripper for asparagus harvesting

Abstract The paper presents a grasping unit for asparagus harvesting based on a commercially available pneumatic gripper. Highly reliable low-cost tactile sensors were developed to determine contact pressure during grasping. Experimental tests were conducted on all system components in order to achieve a thorough knowledge of the physical ptsenomena which determine system behaviour. A fuzzy control system was developed on the basis of this experimental data. The paper then presents and discusses experimental data for grasping tests with different sizes of asparagus and different reference contact pressures to demonstrate the versatility and robustness of the system.

Productivity analysis of the full scale inertial sea wave energy converter prototype: A test case in Pantelleria Island

Wave power is one of the most rich and promising sources of renewable energy for the future. Approximately 2000 TWh/year can be produced through the exploitation of the wave energy potential. In the past four decades, hundreds of Wave Energy Converters have been proposed and studied, but so far a conclusive architecture to harvest wave power has not been identified. Many engineering problems are still to be solved; these include survivability, durability, and effective power capture in a variable wave climate. Reacting body devices use the inertia of a large mass to generate the reaction needed from the power take off (PTO). Heretically, in the case of a simple inertial mass, optimal control adjusts the dynamic parameters of the PTO, such as the spring constant and energy absorbing damping, to maximize energy absorption. The ISWEC (Inertial Sea Wave Energy Converter) uses a gyroscope to create an internal inertial reaction that is able to harvest wave power without exposing mechanical parts to the harsh o...

Design and experiments of linear tubular generators for the Inertial Sea Wave Energy Converter

Sea waves are one of the most interesting and well distributed renewable energy sources in the world. At the current state of the art, several devices have been proposed for wave power exploitation and some have been commercialized. The Inertial Sea Wave Energy Converter is a wave energy converter composed of a floating body slack-moored to the seabed using a gyroscope as a reference frame to produce electric power. In this work the gyroscopic wave energy converter is equipped with two linear tubular generators exploiting the reciprocating movement between the gyroscopic system and the hull to generate power. The linear generators are designed for a 3 kW device. Experimental tests on a small scale prototype are performed

ISWEC: Design of a Prototype Model for Wave Tank Test

The extraction of energy from ocean waves has been investigated in Europe since the 1970s. During the research process hundreds of devices have been proposed and a few of them have been built full scale and deployed to the ocean. Unlike other renewable energies, so far there has not been a device standing out to be the most suitable to exploit wave power. One of the practical problems to be solved in a Wave Energy Converter (WEC) is durability in the harsh marine environment. This could be critical if parts of the converter such as turbine rotors or auxiliary floats are needed to move or to react while exposed to seawater and spray. One method to solve the problem is to use a WEC composed just by one sealed floating body carrying a gyroscope. The inertial effects of the gyroscope are activated by the float motion and are used to drive a generator. The whole system operates in the clean environment inside the float. In this work a procedure to design the ISWEC device (Inertial Sea Wave Energy Converter) is outlined. The mechanical equations describing the system are linearized, studied in the frequency domain and used as a mathematical tool in the design process. The method is then applied iteratively to design a scaled prototype model to be tested in the wave tank at the University of Naples. The final version of the prototype model is then scaled up to evaluate the performances of a full scale device.Copyright

One Degree of Freedom Gyroscopic Mechanism for Wave Energy Converters

Sea waves are one of the most interesting and well distributed renewable energy sources in the world. At the current state of the art, all the existing sea wave energy conversion systems are designed to operate offshore, mainly in the oceans where the waves’ height is definitely high. In the Mediterranean Sea, waves are generally low, except under particular meteorological conditions. Thus, it is necessary to develop devices that can exploit other properties of the waves instead of their height, like wave slopes. In this work a solution for this application is analysed, based on a conversion device characterised by floating positioning (without fixed link or basement at depth level), vertical axis geometry (to exploit any kind of wave, regardless of their direction, without the need for orientation systems), working principle based on an inertial system obtained by a rotor thanks to gyroscopic effect (that can be tuned to maximise the efficiency of the transformation process), and ability to work even with low amplitude waves (up to 0.5 m) typical of the Mediterranean Sea. The work follows three steps: first of all, the mechanical system is described with an analytical approach, secondly the mathematical model is implemented, and, finally, it’s tested in simulated sea environments. A system analytical model will be shown and some numerical results will be remarked.© 2008 ASME

Wave Tank Testing of a Pendulum Wave Energy Converter 1:12 Scale Model

Wave Energy is a widespread, reliable renewable energy source. The early study on Wave Energy dates back in the 70’s, with a particular effort in the last and present decade to make Wave Energy Converters (WECs) more profitable and predictable. The PeWEC (Pendulum Wave Energy Converter) is a pendulum-based WEC. The research activities described in the present work aim to develop a pendulum converter for the Mediterranean Sea, where waves are shorter, thus with a higher frequency compared to the ocean waves, a characteristic well agreeing with the PeWEC frequency response. The mechanical equations of the device are developed and coupled with the hydrodynamic Cummins equation. The work deals with the design and experimental tank test of a 1:12 scale prototype. The experimental data recorded during the testing campaign are used to validate the numerical model previously described. The numerical model proved to be in good agreement with the experiments.

Stochastic Control of Inertial Sea Wave Energy Converter

The ISWEC (inertial sea wave energy converter) is presented, its control problems are stated, and an optimal control strategy is introduced. As the aim of the device is energy conversion, the mean absorbed power by ISWEC is calculated for a plane 2D irregular sea state. The response of the WEC (wave energy converter) is driven by the sea-surface elevation, which is modeled by a stationary and homogeneous zero mean Gaussian stochastic process. System equations are linearized thus simplifying the numerical model of the device. The resulting response is obtained as the output of the coupled mechanic-hydrodynamic model of the device. A stochastic suboptimal controller, derived from optimal control theory, is defined and applied to ISWEC. Results of this approach have been compared with the ones obtained with a linear spring-damper controller, highlighting the capability to obtain a higher value of mean extracted power despite higher power peaks.