Conditions of exact tracking by the linear system output of the standard model of a reduced order

A problem is considered for an exact tracking by the output of a linear stationary system presented in the space of states of the standard model of a reduced order in comparison with the dimension of the system state vector. A minimum possible order of the standard model is defined, at which it is possible to perform the exact tracking of it by the output, conditions are defined of the exact tracking by the output of the standard model of a reduced order, and also a set of the control laws that ensure the exact tracking and the internal stability of the system. The solution relies on the method of canonization of matrices. A methodical example is given.     

Design of modified PD algorithm to control angular motion of large space structure

Consideration was given to the design of an algorithm to control orientation of the large space structure (LSS) in the presence of infralow (less than 0.01Hz) frequencies of elastic oscillations exerting considerable influence on the quality of transients due to closeness of the LSS eigenfrequencies to the frequency of control of the object’s “rigid” motion. Procedure for designing a modified PD-algorithm for orientation of the LSS with infralow frequencies of elastic structural oscillations was described. Methods were proposed for calculation of the coefficients of additional components of the modified algorithm and determination of the LSS eigenfrequency boundary to the right of which the orientation control system is robust to the deviations of the object frequencies or inaccuracy of their definition. Some examples of mathematical modeling of the processes of the relay gyroforce control of LSS orientation using the proposed algorithm were given.     

Robust control of composite beams

The structure uncertainty effect is considered on actively controllable composite beam that is a part of the structure of a civil building in a seismodangerous zone. The solution of the problem for active control of vibrations of the composite beam is based on the introduction of a simplified model of sensors and an actuator, which are implemented in the form of piezoelectric plates pasted on two opposite planes of the beam. A suggestion is made of the practical approach that affords the robust control of the composite beam and is founded on the modern H ₂- and H _∞-methods of the theory of control. The effectiveness of the suggested approach for the suppression of vibrations of the composite beam under consideration is illustrated by the examples of numerical modeling.     

Problems of boundary observability of elastic vibrations described by the system of telegrapher equations

Problems are solved for the observability of elastic vibrations described by various boundary problems for the system of telegrapher equations. The initial conditions that generate observable vibrations are found in the explicit form. The necessary time period of an observation is defined. The solutions of observation problems are given in the case of the classical and generalized solutions of the class L ₂ of appropriate boundary problems.     

Low temperature photoluminescence and infrared dielectric functions of pulsed laser deposited ZnO thin films on silicon

C-axis oriented ZnO thin films were grown on silicon (100) and (111) substrates by pulsed laser deposition. Low temperature photoluminescence spectra show besides the peaks of free excitons, of defect bound excitons, and of a donor-acceptor pair transition a new doublet at 3.328/3.332 eV. The doublet seems to originate from the columnar textured ZnO film structure. A corresponding structural dependence of the broadening parameter of the infrared dielectric functions was derived from spectroscopic ellipsometry in the spectral range from 380 to 1200 cm^− 1. The wave numbers of the E₁ transverse optical and A₁ longitudinal optical phonon modes of the ZnO films on silicon are determined to be 406 and 573 cm^− 1, respectively. These values are slightly smaller than those of single-crystalline ZnO thin films on sapphire.     

General three-dimensional image simulation and surface reconstruction in scanning probe microscopy using a dexel representation

The ability to image complex general three-dimensional (3D) structures, including reentrant surfaces and undercut features using scanning probe microscopy, is becoming increasing important in many small length-scale applications. This paper presents a dexel data representation and its algorithm implementation for scanning probe microscope (SPM) image simulation (morphological dilation) and surface reconstruction (erosion) on such general 3D structures. Validation using simulations, some of which are modeled upon actual atomic force microscope data, demonstrates that the dexel representation can efficiently simulate SPM imaging and reconstruct the sample surface from measured images, including those with reentrant surfaces and undercut features.     

Total cross section of solid mesitylene, toluene and a mixture of them at thermal neutron energies

The total neutron cross sections of mesitylene, toluene and a solution 3:2 by volume of mesitylene and toluene were measured at the electron LINAC based pulsed neutron source of Centro Atómico Bariloche. Measurements were performed at 180 K, 120 K and 31.6 K for mesitylene and at 120 K and 31.6 K for toluene and a solution 3:2 by volume of mesitylene and toluene. The systems are potential moderator materials to be considered in the design of a cold neutron source due to their high resistance to radiation and the richness in low-energy excitations of their frequency spectra, that lead to produce an enhanced cold neutron flux.     

New measurement and evaluation of the excitation function of Ni(p,n) reaction for the production of Cu

One of the radioisotopes for which a growing interest exists in nuclear medicine is ⁶⁴Cu. Its branched decay makes it suitable for both diagnostic and therapeutic purposes. Activation cross sections of the proton induced reaction on enriched ⁶⁴Ni have been studied using the stacked foil technique up to 24 MeV. The experimental cross sections are compared with values available from literature. Thick target yields, based on the discrete measured values of the cross sections are calculated and allow a better estimation of the optimum production parameters.     

Methods of intelligent diagnosis for control of flexible moving craft

A new approach to the control of moving flexible mechanical systems based on the methods of intelligent diagnosis and forecast was proposed. While observing the requirements on stability and performance of control of the main (“rigid”) craft motion, this approach also stabilizes its elastic oscillations. A notion of the “model” function of the effect of basic control on the elastic oscillations in the presence of the dominating mode was introduced. The loop for adaptive adjustment of the basic algorithm of power-optimal control of the flexible craft motion was designed. For the proposed method of control of the elastic multifrequency moving craft such as the large space structure, some results of modeling were presented.     

Using the method of phase biplane to study dynamics of interactions of the elastic structural oscillations of the flexible spacecraft with the control system

A modal-physical representation of the mathematical model of flexible spacecraft enabling one to specify a diversity of the distinctions of the dynamics of controllable motion of the flexible objects was determined. The method of phase biplane enabling strict analysis of the dynamics of relay control of orientation of a flexible object with one dominating mode was described and extended to the method of the fuzzy phase biplane for approximate study of the dynamics of the multifrequency flexible spacecraft. Consideration was given to some important questions concerning the impact of structural flexibility on stability and performance of the control system of orientation of flexible spacecraft.