Search results for "vector [correlation function]"
showing 10 items of 339 documents
A method of desingularization for analytic two-dimensional vector field families
1991
It is well known that isolated singularities of two dimensional analytic vector fields can be desingularized: after a finite number of blowing up operations we obtain a vector field that exhibits only elementary singularities. In the present paper we introduce a similar method to simplify the periodic limit sets of analytic families of vector fields. Although the method is applied here only to reduce to families in which the zero set has codimension at least two, we conjecture that it can be used in general. This is related to the famouss Hibert's problem about planar vector fields.
Development of a Fractional PI controller in an FPGA environment for a Robust High-Performance PMSM Electrical Drive
2021
This paper proposes the application of a Fractional Order PI (FOPI) in the speed loop of a high performance PMSM drive to obtain both speed tracking and load rejection performance with a 1-DOF Proportional Integral (PI) controller and 2-DOF Integral Proportional (IP) controller. Hardware validation was implemented in Field Programmable Gate Array on the LabVIEW environment, based on the National Instruments System-on-Module sbRIO-9651 with Xilinx Zynq-7020. Simulation and experimental results are presented to comparing the performance of a PI, IP and FOPI controllers in the speed loop of a Field Oriented Control (FOC) of a Permanent Magnet Synchronous Motor (PMSM).
Control Strategy for Induction Motor Drives Based on Decoupling Techniques
1989
Abstract In this work a new closed loop, synchronous microprocessor-based controller is proposed for field oriented controlled induction motor drives, using a PWM voltage source inverter. This controller is based on a non linear state feedback compensator which gives decoupling of both rotor current and rotor flux, and direct and inquadrature components of the stator current vector. The compensator has a linearizing effect on the synchronous model of the electromagnetic circuit of the motor. It follows that the control laws can be obtained using optimal control techniques for linear systems. The controller in question gives directly the conduction sequences of the inverter supplying the ind…
Robust, direct torque control of induction motor drives in application to industrial manipulator
2002
The paper analyses the application of three-phase small induction motors as the drives for industrial manipulator joints and their control related problems. By introducing a robust control to the whole systems in which the direct torque control is applied to driving motors, the solution presented is not only realistic but also yields high quality of trajectory tracking. The problem is widely illustrated by simulated results of manipulator's operation with that kind of drives including several control system options.
Practical Implementation of a Synchronous PWM Strategy for Low Switching Frequency FOC of im Drives with ATSAM3X8E Microcontroller
2021
This paper presents a practical implementation of synchronous PWM modulation algorithm for an induction motor field oriented control powered by a DC/AC inverter and implemented on a low-cost microcontroller, the ATSAM3X8E. In particular, a simple algorithm, capable to calculate automatically an optimized set of frequency modulation indexes will be presented. Hysteresis bands are also introduced in the algorithm in order to avoid multiple changeovers during modulation index transitions. Experimental tests and their results will be shown and discussed, highlighting the benefits of the present algorithm, such as reduction of current harmonic content, reduction of current ripple and, consequent…
A Novel Artificial Mosaic Generation Technique Driven by Local Gradient Analysis
2008
Art often provides valuable hints for technological innovations especially in the field of Image Processing and Computer Graphics. In this paper we present a novel method to generate an artificial mosaic starting from a raster input image. This approach, based on Gradient Vector Flow computation and some smart heuristics, permit us to follow the most important edges maintaining at the same time high frequency details. Several examples and comparisons with other recent mosaic generation approaches show the effectiveness of our technique.
p-VARIATION OF VECTOR MEASURES WITH RESPECT TO BILINEAR MAPS
2008
AbstractWe introduce the spaces Vℬp(X) (respectively 𝒱ℬp(X)) of the vector measures ℱ:Σ→X of bounded (p,ℬ)-variation (respectively of bounded (p,ℬ)-semivariation) with respect to a bounded bilinear map ℬ:X×Y →Z and show that the spaces Lℬp(X) consisting of functions which are p-integrable with respect to ℬ, defined in by Blasco and Calabuig [‘Vector-valued functions integrable with respect to bilinear maps’, Taiwanese Math. J. to appear], are isometrically embedded in Vℬp(X). We characterize 𝒱ℬp(X) in terms of bilinear maps from Lp′×Y into Z and Vℬp(X) as a subspace of operators from Lp′(Z*) into Y*. Also we define the notion of cone absolutely summing bilinear maps in order to describe t…
Octupolar excitation of ion motion in a Penning trap: A theoretical study
2014
Abstract High-precision Penning-trap mass spectrometry uses the resonant conversion of the magnetron motional mode into the cyclotron motional mode to determine the cyclotron frequency of the ions under investigation. Usually the conversion process is performed by interaction of the ions with external quadrupolar rf-fields. Recently it was found that conversion by means of octupolar rf-fields entails a tremendous increase in mass resolution and is thus of great interest. However, the conversion results depend in an intricate way on the amplitudes and phases of the octupolar rf-field and of the motional modes of the ions. Experimental progress was hampered by the lack of an underlying theory…
Fast relaxation phenomena and slow mode in extended thermodynamics of superfluids
2003
A macroscopic monofluid model of liquid helium II which is based on extended thermodynamics was formulated in previous works, both in the presence and in the absence of dissipative phenomena. In all these studies, the time evolution of the nonequilibrium stress tensor was neglected, putting the relaxation times @t"0 and @t"2 of the nonequilibrium pressure and of the stress deviator equal to zero. In this work, the time evolution of these fields is not neglected and the complete model with 14 fields is studied, in the linear approximation. The propagation of waves is studied and a dispersion relation of degree 14 is obtained. The solutions of this equation are carried out, perturbing the sol…
A relativistic approach to gravitational instability in the expanding Universe: second-order Lagrangian solutions
1994
A Lagrangian relativistic approach to the non--linear dynamics of cosmological perturbations of an irrotational collisionless fluid is considered. Solutions are given at second order in perturbation theory for the relevant fluid and geometric quantities and compared with the corresponding ones in the Newtonian approximation. Specifically, we compute the density, the volume expansion scalar, the shear, the ``electric" part, or tide, and the ``magnetic" part of the Weyl tensor. The evolution of the shear and the tide beyond the linear regime strongly depends on the ratio of the characteristic size of the perturbation to the cosmological horizon distance. For perturbations on sub--horizon scal…