Model and design of a double frequency piezoelectric resonator

A novel design of a multifrequency mechanical resonator with piezoelectric materials for energy harvesting is presented. The electromechanical response is described by a finite element model, which predicts the output voltage and the generated powe

Trade-off analysis and design of a Hydraulic Energy Scavenger

In the last years there has been a growing interest in intelligent, autonomous devices for household applications. In the near future this technology will be part of our society; sensing and actuating will be integrated in the environment of our houses by means of energy scavengers and wireless microsystems. These systems will be capable of monitoring the environment, communicating with people and among each other, actuating and supplying themselves independently. This concept is now possible thanks to the low power consumption of electronic devices and accurate design of energy scavengers to harvest energy from the surrounding environment. In principle, an autonomous device comprises three main subsystems: an energy scavenger, an energy storage unit and an operational stage. The energy scavenger is capable of harvesting very small amounts of energy from the surroundings and converting it into electrical energy. This energy can be stored in a small storage unit like a small battery or capacitor, thus being available as a power supply. The operational stage can perform a variety of tasks depending on the application. Inside its application range, this kind of system presents several advantages with respect to regular devices using external energy supplies. They can be simpler to apply as no external connections are needed; they are environmentally friendly and might be economically advantageous in the long term. Furthermore, their autonomous nature permits the application in locations where the local energy grid is not present and allows them to be ‘hidden' in the environment, being independent from interaction with humans. In the present paper an energy-harvesting system used to supply a hydraulic control valve of a heating system for a typical residential application is studied. The system converts the kinetic energy from the water flow inside the pipes of the heating system to power the energy scavenger. The harvesting unit is composed of a hydraulic turbine that converts the kinetic energy of the water flow into rotational motion to drive a small electric generator. The design phases comprise a trade-off analysis to define the most suitable hydraulic turbine and electric generator for the energy scavenger, and an optimization of the components to satisfy the systems specification

Mountain Search and Rescue with Remotely Piloted Aircraft Systems

Remotely Piloted Aircraft Systems (RPAS) also known as Unmanned Aerial Systems (UAS) are nowadays becoming more and more popular in several applications. Even though a complete regulation is not yet available all over the world, researches, tests and some real case applications are wide spreading. These technologies can bring many benefits also to the mountain operations especially in emergencies and harsh environmental conditions, such as Search and Rescue (SAR) and avalanche rescue missions. In fact, during last decade, the number of people practicing winter sports in backcountry environment is increased and one of the greatest hazards for recreationists and professionals are avalanches. Often these accidents have severe consequences leading, mostly, to asphyxia-related death, which is confirmed by the hard drop of survival probability after ten minutes from the burying. Therefore, it is essential to minimize the time of burial. Modern avalanche beacon (ARTVA) interface guides the rescuer during the search phase reducing its time. Even if modern avalanche beacons are valid and reliable, the seeking range influences the rescue time. Furthermore, the environment and morphologic conditions of avalanches usually complicates the rescues. The recursive methodology of this kind of searching offers the opportunity to use automatic device like drones (RPAS). These systems allow performing all the required tasks autonomously, with high accuracy and without exposing the rescuers to additional risks due to secondary avalanches. The availability of highly integrated electronics and subsystems specifically meant for the applications, better batteries, miniaturized payload and, in general, affordable prices, has led to the availability of small RPAS with very good performances that can give interesting application opportunities in unconventional environments. The present work is one of the outcome from the experience made by the authors in RPAS fields and in Mechatronics devices for Mountain Safety and shows the design, construction and testing of a multipurpose RPAS to be used in mountain operations. The flying, multi-rotors based, platform and its embedded avionics is designed to meet environmental requirements such as temperature, altitude and wind, assuring the capability of carrying different payloads (separately or together) aimed to: • Avalanche Beacon search with automatic signal recognition and path following algorithms for quick buried identification. • Visual (visible and InfraRed) search and rescue for identifying missing persons on snow and woods even during night. • Customizable payload deployment to drop emergency kits or specific explosive cartridge for controlled avalanche detachment. The resulting small (less than 5kg) RPA is capable of full autonomous flight (including take-off and landing) on a pre-programmed, or easily configurable, custom mission. Furthermore, the embedded autopilot manages the sensors measurements (i.e. beacons or cameras) to update the flying mission. Specific features such as laser altimeter for terrain following have been developed and implemented. Remote control of the RPA from a ground station is available and a possible infrastructure, based on cloud/on-line architecture, for the real application is presented

Investigation on the performances of a twin arm tensioning device

In the present work, an experimental analysis of the performances of a twin arm tensioner is conducted. The investigated device is used in an automotive belt drive system mounting a belt starter generator. This configuration represents the latest trend of micro-hybrid technologies and is devoted to keep the tension of the belt within a reasonable range, while obtaining the highest possible efficiency in both motor and generator modes. At first, the functionality of a twin arm tensioner is investigated with a static model. Afterward, the performances of a real tensioner are experimentally assessed through a dedicated test rig in quasi-static conditions. The system is benchmarked in terms of angular displacement of the tensioner arms, belt tensions on the corresponding spans, and sliding arc in different operating conditions. Finally, experimental and simulation results are compared. It is shown that the proposed static model is able to capture the behavior of the real device and highlight its functionality. </jats:p

Feedforward and Modal Control for a Multi Degree of Freedom High Precision Machine

High precision industrial machines suffer the presence of vibrations due to several noise sources: ground vibration, acoustic noise, direct force disturbances. In the last years the need of higher processing quality and throughput result in a continuing demand for higher accuracy. Therefore vibration isolation systems became mandatory to satisfy these requests. In general, machine supports are designed for high stiffness to obtain a robust machine alignment with respect to its surroundings. However, in the presence of significant ground vibration levels the support stiffness is commonly sacrificed to reduce their transmission to the payload stage. Efforts to go towards these issues are recorded in several applications and the solutions are different for any particular situation, depending on the nature of the vibration sources, the amount of the disturbances and the machine environment. This chapter focuses on the evaluation of a vibration isolation device on the working cell of a micro-mechanical laser center, using active electromagnetic actuators. The machine is composed by two main parts: a frame support and a payload stage where the laser cutting is performed. The machine potential in terms of accuracy and precision is reduced by the presence of two main vibration sources: the ground and the stage itself. The active device should meet two main goals: the payload vibrations damping and the reduction of the transmissibility of ground disturbances. In this work the phases followed to design, realize and validate the device are illustrated with a particular attention to the mechatronics aspects of the project and to the control strategies. The chapter starts on the description of the common solutions and of the techniques described in literature. The requirements analysis and a trade-off phase on the available opportunities for vibration isolation are described. An analysis of the plant components is reported in the second section along with an exhaustive explanation of a) actuation subsystem consisting in four voice-coils, two per axis; b) sensing subsystem aimed to measure the absolute velocities of the frame support and of the stage are measured by means of eight geophone sensors. The considerations leading to the choice of this sensing system are reported along with the signal conditioning block. The active control is performed with a digital platform based on DSP and FPGA. The core of the chapter is the description of the modeling approach and of the control strategies design. The bond-graph approach is used to represent the system behavior, in particular the interactions between the mechanical and electrical subsystems are illustrated. The realized model includes the plant, the sensing, the control and the actuation blocks. The plant is considered as a classical two mass-spring-damper system resulting on a multi-input multi-output system (MIMO), considering disturbances from the stage and the ground and the actuators action between the two masses. Time and frequency domain computations are carried out from the model to evaluate vibration levels and displacements and to identify which parameters need to be carefully designed to satisfy the requirements. The control strategy is focused on the attenuation of the effects of microvibrations on the stage caused by different sources. The technique consists in a combination of two actions, the goal being the minimization of the ground vibrations transmission and the payload vibrations damping: • A single-axis decentralized action consisting in a modal controller used to compensate the high-pass band dynamic of the geophone sensors and to control the vibrations. • A feedforward action working on the disturbances coming from the payload and from the ground. This control is not generated in on-line, but computed in advance from the data of machine responses to the direct disturbances coming from the floor and the stage and resulting in vibrations on the payload and on the frame. The first action itself is aimed to perform active isolation and vibration that nevertheless could be not sufficient for severe specifications applications. The feedforward action is hence used to face this shortcoming by suppressing direct disturbance. The controller design phases along with its performance evaluation are described. The chapter concludes on the illustration of the results obtained with the proposed modeling and control strategy

Gruppo elettrovalvola perfezionata per impianti fluidici di condizionamento e relativo gruppo contabilizzatore

Un gruppo servovalvola definente un condotto collegabile ad una linea di un impianto termoidraulico tramite mezzi di collegamento filettati rilasciabili, comprende un dispositivo a turbina alloggiato nel condotto, una prima pluralità di magneti permanenti portati da un rotore del dispositivo a turbina, una seconda pluralità di poli magnetici accoppiati magneticamente alla prima pluralità di magneti permanenti, una centralina di controllo collegata ai poli magnetici, una batteria collegata alla centralina di controllo per essere caricata tramite il dispositivo a turbina, un trasmettitore collegato alla centralina di controllo per trasmettere / ricevere dati a distanza, un attuatore di regolazione fluidica configurato per regolare il flusso nel condotto e controllato / alimentato tramite la centralina di controllo e la batteri