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Herein, we report the successful surgical treatment of the case of a 13-year-old patient with combined pulmonary artery stenosis, critical stenosis of the xenopericardial conduit and aortic valve insufficiency after two previous operations (radical correction of the common arterial trunk during the neonatal period and replacement of the right ventricular excretory tract conduit with branch plasty at three years of age). According to echocardiography, the peak pressure gradient across the conduit was 110 mmHg, along with aortic valve regurgitation of the third degree. According to computerised tomography angiography, there was narrowing of the right pulmonary artery up to 3 mm distally along with total calcification of the conduit and branches of the pulmonary artery with an intimate fit to the chest wall. The trunk of the pulmonary artery was replaced with a valve-containing conduit CARBOMEDICS СARBO-SEAL No.25 (LivaNova PLC, London, United Kingdom); right pulmonary artery plasty was performed with a xenopericardial patch; aortic valve was replaced with CARBOMEDICS СARBO-SEAL No.23 (LivaNova PLC, London, United Kingdom), a mechanical prosthesis, and supracoronary prosthetics were used for the ascending aorta. The duration of cardiopulmonary bypasswas 309 minutes, cross-clampwas 142 minutes and circulatory arrest was 49 minutes, with 26°C hypothermia. Extubation was performed 10 hours after surgery, and he spent 3 days in intensive care. The duration of hospitalisation was 26 days. He was examined after 6 months, and there were no complaints. The presented clinical case shows that implantation of a mechanical prosthesis is justified with repeated reoperations on the outflow tract of the right ventricle and the pulmonary trunk, and it may be the surgery of choice.Received 3 September 2020. Revised 1 October 2020. Accepted 5 October 2020.Funding: The study did not have sponsorship.Conflict of interest: Authors declare no conflict of interest.Author contributionsDrafting the article: S.A. Belash, M.M. AmariLiterature review: S.A. Belash, M.M. AmariIllustrations: S.S. Shevchenko, A.K. ShadrinCritical revision of the article: K.O. Barbukhatti, S.A. Belash, N.B. Karakhalis, V.A. PorkhanovFinal approval of the version to be published: K.O. Barbukhatti, S.A. Belash, S.S. Shevchenko, M.M. Amari, N.B. Karakhalis, A.K. Shadrin, V.A. Porkhanov

This paper introduces a new approach to control of nonlinear non-stationary multichannel plant with lumped parameters and additive perturbations. Controlled plant is represented as a set of equations in matrix-vector form, with number of output variables equal to the number of controlled variables. The problem is stated as follows: to control plant output provided that output variables and state variables are observable. Plant equations are converted into a state dependent coefficient (SDC) form, then method of correction of plant dynamics and compensation of perturbations is used. A variant of conversion to the SDC form based on E. A. Barabashin’s method is suggested. Reverse models of the plant are defined with respect to reference and deviation channels. Algebraic equations are presented, which, when solved, yield reverse models. Definitions of etalon filters are introduced, allowing a physical implementation of a controller when used in conjunction with reverse models. Conditions to which matrices of etalon filters must conform are considered. It was found by examples that part of coefficients of etalon filters can be chosen arbitrarily. Using the method of correction of controlled plant dynamics and perturbations, utilizing reverse models and etalon filters, a physically implementable controller algorithm was constructed. Then it was transformed to physically implementable form using equivalent transformations. Components of the final algorithm are obtained by the means of algebraic transformations of functional matrices of the plant and etalon filter. Equations for closed control system are presented. It follows from these equations that system is asymptotically stable and that transient processes correspond with their respective etalon filters. Even though compensation method was used, a multichannel closed-loop control system was obtained. An advantage of suggested method is that it allows a simple procedure for the control algorithm synthesis using evident physical initial data. The efficacy of obtained algorithms was verified using several examples. Computer simulation showed that control systems are robust and comply with specified requirements. Directions for further research were suggested.

The task of controlling the manipulation robot movement in one direction has been considered. Such task appears at cutting, welding, painting and other similar operations, when the robot instrument performs a program motion along the working surface and at the same time, it is necessary to keep a definite distance from this instrument to the surface automatically without excessive correction. A new algorithm of controlling the linear object of the second order of the general form has been obtained by dynamics and perturbations compensation method, which takes precedence over well-known decisions. The algorithm provides a zero static error of the system regulation and movement in acquisition of external effects within the accuracy of standard filters of the second order that is convenient for practical use. The first filter indicates movements of the system during the task performing; the second one provides perturbations compensation on state variables. A step-by-step procedure of the algorithm synthesis has been represented for the second order controlled object of the general form. Formulae for calculating regulator coefficients have been obtained. The obtained equations defining processes in a closed control system allow performing the analysis of the control quality and the dynamics of control changes depending on external influences. A method of equations identification of the robot motion in conditions when we know the maximum speed of its instrument movement and a dynamic error of the robot servosystem regulating has been developed. By this method, the robot equations are brought up to the Vyshnegradskiy’s form and then on the computer model a fundamental frequency and a decay factor can be easily chosen. The application of the obtained algorithm has been reviewed to create a system of automatic regulation of the robot instrument position. It has been clarified that defining free coefficients of these filters on position of filter fundamental frequency equation and a controlled object provides the given system operation speed at moderate amplitude of controlling actions. A mathematical modeling method has shown the advantages of regulation program quality, parametric and structural robustness of the obtained control system.

It is shown that, growth of the layer with compressive residual stresses at advanced surface plastic deformation of smooth samples leads to an increase in the endurance limit of the notched specimens due to an increase in the compressive residual stresses in their dangerous section. The study was conducted on the specimens with outer diameterDequal to 10 and 25 mm and on a 25 mm specimen with inner diameterd= 15 mm which were subjected to air shot blasting and roll-in. Residual stresses in smooth specimens were determined by the mechanical method. Circular incisions (R= 0.3 and 0.5 mm) were applied on hardened smooth samples with a shaped cutter. Residual stresses in notched specimens were determined by a numerical method calculating the redistribution of the residual stresses upon the incision. As the diameter of the samples increases with the same strengthening surface treatment,the depth of the layer with the compressive residual stresses increases due to an increase in the rigidity of the samples. The effect of surface hardening on the endurance limit of notched specimens was evaluated according to the criterion of the average integral residual stresses, which takes into account both the magnitude and completeness of the residual stresses. This criterion was calculated from the depth of the non-propagating fatigue crack that occurs in the surface layer in the dangerous section of the specimen during the fatigue test at the limit endurance. Fatigue tests are carried out in symmetrical cycle, the test base being 3 × 106cycles of loading. Estimation of the increment of the limit endurance of surface-hardened cylindrical specimens with semicircular notches gave the results acceptable for practice. The use of the proposed method can significantly reduce long-term and expensive fatigue tests.

Residual stresses in the dangerous section of toothed wheels made of materials and according to practices accepted in aviation engine construction have been determined using a mechanical method. The influence of the technology of manufacturing of toothed wheels, thermo-chemical treatment, hardening and coating on the residual stresses has been examined. Current technologies of manufacturing toothed wheels lead to significant dispersion of residual stresses, especially after thermo-chemical treatment. Therefore, the results have been statistically processed for each batch of parts and the average values are shown on the residual stress diagrams. We demonstrate the possibility of determining residual stress distribution in the dangerous section of a wheel tooth by the initial deformations of the reference specimen, which makes it possible to keep the part under examination unimpaired. A plate made of the same material as the toothed wheel and hardened simultaneously with the part under examination was used as a reference specimen. The influence of residual stresses on the fatigue resistance of toothed wheels by the average integral residual stresses criterion that takes into account both the value of residual stresses and the nature of their distribution in the dangerous section of toothed wheels was examined.

This paper introduces a new physical considerations-based approach to the development of control algorithms for dynamic plants, which involves a compensation principle as follows. Being external with respect to a controlled plant, control actions (compensating signals) are applied with the opposite sign to the corresponding variables of the inverse mathematical model of the plant. Regularization of the resulting system is performed by incorporating etalon filters in compensation loops. The described method is used to solve a control problem for the linear stable multidimensional plants with additive external influences and compensation of the perturbations affecting the output variables.

The operating principles of automated control system for glass-melting furnaces and drums for drying sand and dolomite are described.