Search

International audience

In this paper we consider the stabilization problem of a beam clamped on a moving inertia actuated by an external torque and force. The beam is modelled as a distributed parameter port-Hamiltonian system (PDEs), while the inertia as a finite dimensional port-Hamiltonian system (ODEs). The control inputs correspond to a torque applied by a rotating motor and a force applied by a linear motor. In this paper we propose the use of a strong dissipation term in the control law, consisting of the time derivative of the restoring force at the clamping point. After a change of variables, the closed loop system shows dissipation at the boundaries of the PDEs. In this preliminary work we show that the closed loop operator is the generator of a contraction C 0 -semigroup in a special weighted space, with norm equivalent to the standard one. Further, we prove the asymptotic stability of the closed loop system and we show the effectiveness of the proposed control law in comparison with a PD controller with the help of numerical simulations.

Virtual conference; International audience; The paper deals with the characterization of a dummy 'output function' associated with the stable component of the zero-dynamics of a linear square multi-input multi-output system. With reference to the 4-Tank dynamics, it is shown how such a procedure, applied to the linear tangent model of a nonlinear plant, may be profitably applied to assure local stability in closed loop.

In this article the new frontier in Spatial Power Amplifiers is shown, with particular attention to the their Space Applications. These amplifiers have in fact the characteristic of High RF Power, Solid State Technology and High Power Density due to the small sizes that can be reached. We will show the performances of three amplifiers employing the spatial combining technique, two prototypes in the X-Band and one in the Ka-Band, with a brief description of the design approach. These amplifiers belong to the Single Waveguide group of the SPC family, thus a WR90 and a WR28 waveguides are employed. Very good performances are obtained from these prototypes, with a very high power density due their small sizes.

This paper deals with the design and realization of a coaxial Wideband Spatial Power Combiner. It is composed by 16 amplifier modules in order to potentially deliver 50dBm in the 3.5–20GHz. New tips have been adopted to reduce reflections and loss and to avoid resonance occurring in the whole operating bandwidth. Only the passive elements have been assembled and characterized.

Galileo program is approved by the European Commission and the European Space Agency (ESA). The activities related to GSTBV2 experimental satellite as well as the implementation of the in orbit validation phase are in progress. Atomic clocks represent critical equipment for the satellite navigation system and clocks development has been continuously supported by ESA. The rubidium atomic frequency standard (RAFS) and the passive hydrogen maser (PHM) are at present the baseline clock technologies for the Galileo navigation payload. This article gives a general overview on the RAFS and the PHM developments and evolution up to now. It also provides updated information on the performance measurement results and qualification status

This paper focuses on the possibility to obtain a broad-band naval structural antenna as integration of one or more wire radiating elements together with an existing super-structure such as the funnel or a big mast which are rather common in many ship scenarios. The funnel in particular, has typically cylindrical, pyramidal as well as conical shape, and diameter (5 m-10 m) and height (10 m-25 m) comparable with HF wavelengths. Such a structure is therefore a good candidate to host antennas or even to become part of a radiating system. The integration solution which is here proposed potentially yields a broadband structural antenna for HF naval communication. Such a system has the possibility to be driven by one or multiple-sources and to communicate along the horizon and by near vertical-incidence sky-wave (NVIS at 2-7 MHz) depending on the frequency used and on the particular service to be carried out. A structural solution also offers the advantages of limited space requirements and the intrinsic compensation of the pattern distortion due to the presence of the naval environment, which is instead partly embedded into the antenna system

The paper derives the theoretical expression of the cavity pulling factor in Galileo space passive hydrogen Maser, based on the 'single frequency modulation'. The sensitivity of the cavity pulling vs. the phase selection is deduced in order to account for the experimental errors in the phase adjustments. The theoretical calculation shows the new phase setting exists to achieve a zero cavity pulling, and the preliminary experimental results comparing with the two phase selection are presented.