1,721,012 research outputs found
OBSERVERS FOR DISCRETE-TIME NONLINEAR-SYSTEMS
No full textThe problem of observers for discrete-time nonlinear systems has been considered and a simple, easy-to-implement algorithm is given whose convergence properties are guaranteed for autonomous and forced systems. Some numerical examples show the effectiveness of the proposed observer
ADAPTIVE CONTROL OF D.C. ACTUATORS FOR ROBOTICS
No full textThis paper presents a model reference adaptive control method which is particularly appropriate in the control of electrical drives. The control algorithm has been developed taking into account both the control problems (such as the influence of a discrete control action on the behavior of a continuous system) and the hardware and software structures of the computing device, which is generally a multiple processor system in order to satisfy real-time requirements.
This approach allows the realization of simple and modular microprocessor-based adaptive controllers.
To evaluate the effectiveness of the adaptive control method, the paper presents the results of simulations which bave been carried out in the case of a D.C. drive and compares performances obtained with the adaptive controller and a P.I.D. regulator. To obtain from the simulations results which match with the actual behavior of the D.C. motor, its mathematical
model takes into account the saturation of the magnetic care and the parameter variations
A predictive model of iron oxide nanoparticles flocculation tuning Z-potential in aqueous environment for biological application
No full textIron oxide nanoparticles are the most used magnetic nanoparticles in biomedical and biotechnological field because of their nontoxicity respect to the other metals. The investigation of iron oxide nanoparticles behaviour in aqueous environment is important for the biological applications in terms of polydispersity, mobility, cellular uptake and response to the external magnetic field. Iron oxide nanoparticles tend to agglomerate in aqueous solutions; thus, the stabilisation and aggregation could be modified tuning the colloids physical proprieties. Surfactants or polymers are often used to avoid agglomeration and increase nanoparticles stability. We have modelled and synthesised iron oxide nanoparticles through a co-precipitation method, in order to study the influence of surfactants and coatings on the aggregation state. Thus, we compared experimental results to simulation model data. The change of Z-potential and the clusters size were determined by Dynamic Light Scattering. We developed a suitable numerical model to predict the flocculation. The effects of Volume Mean Diameter and fractal dimension were explored in the model. We obtained the trend of these parameters tuning the Z-potential. These curves matched with the experimental results and confirmed the goodness of the model. Subsequently, we exploited the model to study the influence of nanoparticles aggregation and stability by Z-potential and external magnetic field. The highest Z-potential is reached up with a small external magnetic influence, a small aggregation and then a high suspension stability. Thus, we obtained a predictive model of Iron oxide nanoparticles flocculation that will be exploited for the nanoparticles engineering and experimental setup of bioassays
A ROBUST OBSERVER FOR DISCRETE-TIME NONLINEAR-SYSTEMS
No full textThis paper extends the results developed in (Ciccarella et al., 1993) and presents a robust observer for discrete time nonlinear systems. A simple, robust and easy to implement algorithm is given whose convergence properties are guaranteed for autonomous and forced systems. Combined parameter and state estimation is made for a numerical example, which compares the robust observer to the observer given in (Ciccarella et al., 1993)
ASYMPTOTIC LINEARIZATION AND STABILIZATION FOR A CLASS OF NONLINEAR-SYSTEMS
No full textThis paper presents a nonlinear output feedback which asymptotically linearizes the class of nonlinear, continuous-time, affine in the control systems having relative degree equal to the state space dimension. Moreover, we show that any set of eigenvalues can be assigned for the asymptotic closed-loop linear system. The controller is based on a nonlinear observer, presented in a previous paper, and on the linearizing state feedback proposed by Isidori and computed in the estimated state. The main result obtained is equivalent to the separation theorem in the linear case
A LUENBERGER-LIKE OBSERVER FOR NONLINEAR-SYSTEMS
No full textA state observer is proposed for nonlinear continuous time systems which extends the well known Luenberger observer. In particular, on the basis of simple assumptions on the regularity of the system equations (observability and the global Holder condition for suitable functions), which are generally satisfied for physically meaningful dynamic systems, the global asymptotic convergence of the estimated state towards the true state is shown. Finally, some examples of applications are also reported showing the effectiveness of the proposed observer
Use of readily available chiral compounds related to the Betti base in the enantioselective addition of diethylzinc to aryl aldehydes
No full textReadily available members of the family of chiral non-racemic aminonaphthols related to the Betti base 1 were tested as complexing agents in the catalytic enantioselective addition of diethylzinc to aryl aldehydes. The use of these bases gave high ee values (up to >99%). The highest ee values were obtained with the tertiary aminonaphthol 2. An important role was played by the solvent. The effect of the nature and the position of the substituents on the aromatic ring of the aldehyde was also investigated
The Betti base: absolute configuration and routes to a family of related chiral nonracemic bases
No full textCoexistence of FTTC and FTTDp Network Architectures in Different VDSL2 Scenarios
No full textVery high speed Digital Subscriber Line type 2 (VDSL2) systems can achieve significant bit rate values depending on the access network architecture and how far-end crosstalk (FEXT) interference suppression is implemented. The so-called vectoring technology recently became an implementation reality. It was introduced to dynamically suppress ‘self-FEXT’ in a cable of twisted pairs on both downstream (DS) and upstream (US) signals. In the DS direction, crosstalk pre-compensation precedes modulation, and in the US cancellation follows demodulation. However, vectoring allows to effectively eliminate crosstalk if lines belong to the same vectored group. When this condition is not satisfied, in general, even very few uncontrolled interferers can cause significant performance degradation. In this paper, we evaluate by simulation the VDSL2 performance in scenarios of coexistence between Fibre-To-The-Cabinet (FTTC) with vectoring and Fibre-To-The-Distribution point (FTTDp) architectures. We consider two different combinations of VDSL2 band plans assigned to the FTTC and FTTDp networks. We analyse VDSL2 performance in both cases of absence of spectrum management and implementation of the Downstream Power Back-Off (DPBO) technique. We also study the throughput trade-off between the two VDSL2 systems due to DPBO. Results show that, to protect VDSL2 FTTC systems, DPBO must be configured on VDSL2 FTTDp, whereas the investment required to bring the optical fibre to the distribution point could be justified by the improved performance achievable with the FTTDp architecture, even with the VDSL2 band profiles currently used. The presented coexistence analysis can be useful with reference to the G.fast spectrum allocations currently under definition. © 2014 The Authors. Transactions on Emerging Telecommunications Technologies published by John Wiley & Sons, Ltd
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