1,721,071 research outputs found
Zero Reaction Torque Trajectory Tracking of an Aerial Manipulator through Extended Generalized Jacobian
Full text linkFeatured Application: Inspection of structures, e.g., offshore/nuclear/eolic plants, bridges, and tall buildings. Placement and retrieval of sensors. Assembly of structures in places not accessible/safe for humans. Aerial manipulators are used in industrial and service robotics tasks such as assembly, inspection, and maintenance. One of the main challenges in aerial manipulation is related to the motion of the UAV base caused by manipulator disturbance torques and forces, which jeopardize the precision of the robot manipulator. In this paper, we propose two novel inverse kinematic control methods used to track a trajectory with an aerial manipulator while also considering resultant UAV base motions. The first method is adapted from the generalized Jacobian formulation used in space robotics and includes the change in system momentum resulting from gravity and UAV control forces in the inverse kinematic control equation. This approach is simulated for a 2 and 3 degree-of-freedom aerial manipulator tracking trajectories with the end-effector. Although the end-effector position error is approximately zero throughout the simulated task, we see significant undesired UAV base motions of several centimeters in magnitude. To ameliorate this by exploiting the kinematic redundancy, we modify the generalized Jacobian by adding an additional task constraint which minimizes the reaction torques from the manipulator, to form the extended generalized Jacobian. While the second approach results in improved precision and reduced base motion by an order of magnitude as compared to the generalized Jacobian, a drawback is the reduction in the available workspace as the solution seeks to minimize the manipulator center of gravity translation. We also demonstrate and compare both approaches in a load picking task. All the algorithms are completed computationally faster than real time in the MATLAB simulations, illustrating their potential for application in real-world experiments
DEVELOPMENT OF A HYBRID HARVESTER FOR COLLECTING ENERGY FROM WIND AND VIBRATIONS IN LIGHT VEHICLES
No full textA bicycle experiences road-excited vibrations and is impacted by a wind flow. Both these phenomena can be exploited for energy harvesting. Previous research showed that the tuning of the harvester to road-excited vibrations requires a low natural frequency that can be achieved by means of a large tip mass. This tip mass can be used to equip the harvester with a bluff body for energy harvesting from wind-excited vibrations. The interaction between the bluff body and the wind flow generates a vortex shedding phenomenon that at a certain wind velocity is able to excite the harvester in resonance condition. Moreover, the turbulence of the incoming wind is able to excite the bluff body in the high velocity range (buffeting excitation). The paper deals with mathematical and experimental analyses for the development of a hybrid piezoelectric harvester able to scavenge energy from road-excited vibrations and wind. A multi-physical mathematical model that takes into account the couplings between the mechanical, electrical and fluid domains is developed. The coupled equations are solved in Matlab and are used for the harvester design. Two prototypes are developed and tested. The results of experimental tests carried out in a wind tunnel and in open space show the potentialities of the proposed harvester layout
LE NUOVE FRONTIERE DEL SISTEMA ANESTESIOLOGICO: IL SISTEMA DI EMERGENZA, I TRAPIANTI E LA TERAPIA ANTALGICA DOMICILIARE atti congresso
No full text
Surfactant therapy and intravenous zanamivir in severe respiratory failure due to persistent influenza A/H1N1 2009 virus infection.
No full textn
Pasetto, A.: Exploring the environment of high Rotation Measure Active Galactic Nuclei through wide-band radio spectropolarimetry observations
Full text linkIn this Thesis I present an observational study of a sample of radio AGN sources. I study their radio polarization properties in a wide frequency range by observing with the 100-m Effelsberg telescope and the Very Large Array (VLA) interferometer. The aim was 1) to define a sample of candidates to contain an extreme environment around the SMBH and, 2) to study their environment by modeling of the polarization properties within a wide frequency range. I select sources with no detectable flux polarization at 1.4GHz in the NVSS survey, characteristic of strong depolarization due to a high value of Rotation Measure (RM) and thus, of an extreme medium in these sources. I performed single dish observations at 10.45 GHz using the 100-m Effelsberg telescope. At this high frequency, I detected polarized flux density on 30 sources, which became our high-RM candidates. Single dish follow-up in the 2 to 15 GHz frequency range, were performed to characterize their radio spectra and to determine their RMs. The polarization angle behavior deviates significantly from the lambda^2 law, suggesting that several Faraday screens are present in the intervening medium. I studied the most interesting high-RM cases through wide-band high sensitive observations at C and X bands using the JVLA. I modeled the polarization properties constructing a set of models which are combinations of simple internal and the external Faraday screens. This new approach of polarization study allows to spectrally resolve multiple polarized components of unresolved AGN with the result to trace some clumpy and dense region surrounding them. This new spectropolarimetry approach can be adopted as a new way to trace clumpy and dense regions surrounding the AGN
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
- …
