1,721,018 research outputs found
A selective negative derivative feedback algorithm to improve stability for inertial actuators
Full text linkInertial actuators are widely used in active vibration control, since they don't need to react off the base structure. Then, unlike reactive actuators, they can be used as modules that can be directly installed on a vibrating structure. In many cases, inertial actuators are used to develop some stand-alone active dampers. Such devices are embedded with sensors and a microcontroller, in order to independently perform the vibration control task. This kind of control unit is commonly adopted to implement decentralized architectures. In this work, the main goal was to limit instability phenomena related to the dynamics of inertial actuators. The proposed solution also aims to improve the performance of a decentralized control strategy through a partial sharing of data between devices, without the use of cables. First, the formulation of the modified Negative Derivative Feedback resonant controller is derived; then, the steps of the control strategy are explained, which are based on a preliminary modal identification of the structure and the assignment of a compensator for each resonance frequency to be controlled. Finally, the proposed method is validated with experimental results from a clamped-clamped beam
A method to overcome wireless communication limits in decentralized active control applications
Full text linkIn this work the use of many stand-alone devices is considered for active vibration control. A stand-alone device represents a control unit which is able to independently perform the vibration control task, since it is embedded with sensors, an inertial actuator and a microcontroller, in which the control algorithm is implemented. The developed active controller is also embedded with a wireless module, in order to share information with other devices within the network. The proposed solution aims to improve the performance a decentralized control architecture and it is based on the optimal control theory. The Linear Quadratic Regulator works with the fullstate of the system, which is provided through a state estimation. A state recovery algorithm is then adopted to improve the quality of the estimation without placing a hefty burden on the wireless channel. Numerical analysis is made in order to study the advantages of this method. Finally, the proposed solution is validated with experimental results from a clamped-clamped beam
Application of a virtual inerter in active vibration control using inertial actuators
Full text linkIn this paper the application of an inerter to a control system based on inertial actuators is investigated. Since the dynamics of this kind of actuators affects the stability of the controlled system, the application of the inerter aims to limit instability problems by shifting down the resonance frequency of the actuator. The interaction of this passive element with the other vibration modes of the structure under control is not negligible. The inerter should be physically placed in parallel with the elastic suspension of the actuator and the transducer; in this paper, the inerter behavior is simulated by the inertial actuator through an acceleration feedback. First, the study is carried out on a two degrees-of-freedom model and stability considerations are made; then, the approach is implemented on the Finite Element model of a clamped-clamped beam which is also used as experimental test rig. Finally, the proposed solution is validated with experimental results
Wireless sensor nodes for freight trains condition monitoring
No full textObjective of the present work is to present the design and the laboratory tests of Wireless Sensor Nodes (WSNs) equipped with three different on-board energy production systems, to be installed on freight trains for condition monitoring and structural diagnosis of the railway vehicle. The three sensor nodes are designed to be completely energetically autonomous, exploiting three different energy sources easily available on a moving train: Solar, Wind and Mechanical vibration power. a PCB board hosts different ICs, able to convert the uncontrolled and unregulated power sources in order to properly feed all the on-board components and possibly to charge the battery. The electronics for the acquisition, elaboration and wireless transmission of data, is presented and analyzed in terms of performances and consumptions. The three WSNs, based on the different energy sources, are designed and compared in terms of fatigue behavior and performances by means of laboratory tests
Follicular factors influence oocyte fertilizability by modulating the intercellular cooperation between cumulus cells and oocyte
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
A Software-in-the-Loop Simulation of Vehicle Control Unit Algorithms for a Driverless Railway Vehicle
Full text linkThe realization of the first prototype of a vehicle requires several tests of the algorithms implemented on the electronic control unit (ECU). This represents an important step for conventional vehicles, which becomes fundamental when dealing with unmanned vehicles. Since there is no human supervision, most critical tasks are handled by the control unit, which results in higher complexity for the control algorithms. In this work, a software-in-the-loop (SiL) test bench is used to validate the control algorithms of a vehicle control unit (VCU) for a driverless railway vehicle (DLRV). The VCU manages the control of the traction motors, pneumatic braking systems, and range extender, as well as control of the hybrid powertrain configuration to guarantee a high level of availability via the use of redundant systems. The SiL test bench has been developed in a Simulink real-time environment, where the vehicle model is simulated along with its fundamental subsystems. The model communicates with the VCU through a CAN bus protocol in the same way that it will operate with a real vehicle. The proposed method can be used to simulate many mission profiles for the DLRV, which may last several hours each. Moreover, this kind of test bench ensures a high time resolution, which allows one to find solutions for problems which occur with a time scale that is much smaller than the simulation time scale
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