Speed control in DC and AC drives

<div><span lang="EN-US">Three speed-control strategies for DC and AC drives are presented in this study: a proportional<strong> </strong>integral derivative (PID) control strategy; an internal model control (IMC); and a state-space control by pole assignment with full state observer (ESSO). The three strategies are applied to a case study, demonstrating the potential of each one. Experimental identification was used to obtain the drive models used for the synthesis of the controllers. The three strategies showed satisfactory results when compared with the requirements imposed on the system, in addition to the good rejection of disturbances. However, the IMC strategy showed itself to be a little softer and with no maximum overshoot, which in some cases and some applications is usually a restriction.</span></div>

Failure analysis of flexible couplings by self-heating

Flexible couplings are applied in mechanical systems to reduce torsional vibrations. Failures in the flexible parts of the couplings are often incorrectly attributed to overloading of the couplings. The goal of the article is to prove by experimental analysis that self-heating occurs in flexible couplings. The self-heating of the flexible coupling and the consequent increase in the temperature of the flexible part is the cause of the failure. Experimental identification of self-heating was performed on three types of flexible couplings. Although these couplings are design different, they are used for a nominal torque of 150Nm.

Units of a person’s mental lexicon and the nature of connections between them

In the modern world, the interest of the scientific world on the interdisciplinary basis of speech perception on the part of psychology and Philology has increased significantly. It should be noted that, despite the increasing role of the English language in Kazakhstan at the present time, this problem is probably the least developed. The purpose of the article is to describe the results of scientific research on the process of entering a foreign word into the system of internal lexicon of a student at the level of professional training. Methodology used: experimental (identification of the threshold of the "educational" lexical minimum) and comparative (comparison of associative fields of English words of the profile for students of the direction, in general 1500 lexical units) were used. From the results the data obtained allow us to identify the specifics of the entry of a foreign language word into the system of the student's internal lexicon at the professional level. Keywords: psycholinguistics, mental lexicon, internal dictionary, foreign language, connections

Experimental identification of the material standard linear solid model parameters by means of dynamical measurements

A procedure for the experimental identification of the material standard linear solid model parameters by means of dynamic mechanical analysis test instrument measurements is presented. Since the standard linear solid material stress–strain functional D( ω) relationship in the frequency domain formally depends on the standard linear solid material parameters, a procedure able to identify these parameters from test measurement estimates is proposed in this work. Nevertheless, a critical, nonlinear and non-parametric approach is to be followed since the number of the material standard linear solid block components is generally unknown, and the material D( ω) shows a highly nonlinear dependency on the unknown standard linear solid material parameters. For these reasons, measurement and test model noise is expected to strongly influence the accuracy of the identification results. A multi-step procedure is presented, consisting first in the non-parametric identification of a frequency dependent, two degrees of freedom model instrument frame by means of a polynomial rational function, where polynomial order and parameters, such as polynomial coefficients and pole-residue couples, are optimally identified by means of an algebraic numerical technique and of an iterative stabilization procedure. Another procedure able to identify the material D( ω) polynomial rational functional relationship in the frequency domain is also proposed, taking into account the dynamic contribution of the instrument frame, of the inertial contribution of the distributed mass of the beam and of the lumped mass of the instrument force measuring system. An effective procedure, able to identify the standard linear solid material model parameters in the time domain from the identified material physical poles, is finally proposed. Some application examples, concerning the identification of the standard linear solid model of a known material and of an unknown composite material, are shown and discussed as well.