Introduction. The article investigated one of the problems of creating exoskeletons — controlling the properties of magnetic rheological fluid in links of variable length with adjustable stiffness. Based on the research of domestic and foreign authors, the development and urgency of the topic was evaluated. The disadvantage of known exoskeleton models has been specified, i.e., the use of absolutely solid links, whose dynamics does not convey the dynamics of the human musculoskeletal system.

   The scientific research aimed at the formation of a new direction in the development of exoskeletons that accurately simulate the biomechanics of movements.
   Materials and Methods. Different states of structures of variable-length links with a magnetorheological fluid were studied. It has been noted that the links work on the principle of magnetic shock absorbers and consist of a piston rod, electromagnetic coils, and a housing filled with magnetorheological fluid. The ordering effect of an external magnetic field on the particles of a magnetorheological fluid was visualized and mathematically presented. The significance of such factors as time, charge density, magnetic field strength, as well as vectors of electric and magnetic induction, electric intensity and electric current density for this system was shown. The input parameter affecting the behavior of the magnetorheological fluid was determined. This was the magnetic field intensity. It was shown that the viscosity of the liquid varied depending on the shape of the magnetic particles (oblong or oblate ellipsoid).
   Results. The dependences that were fundamental for solving the task were investigated and visualized. The magnetic field strength and the angle between the vector directed along a straight line connecting the centers of two micron particles, and the vector of the external magnetic field strength were taken as the basic parameters. It was shown how the magnetic moment, voltage and its antisymmetric part depended on them. It was established that to control the properties of a magnetorheological fluid, it was required to change: – the external magnetic field intensity; – the angle between the external magnetic field intensity and the orientation vector between the dipoles. Two values of force were compared: one – for a given link design, and the other — fixed when walking in the lower leg of a person. The consistency of these indicators was established.
   Discussion and Conclusion. The scientific research results allowed us to present: – a method for controlling the properties of a magnetorheological fluid by an external magnetic field; – a variable-length link model with adjustable stiffness. The results obtained can be used in modeling multilink structures to create comfortable exoskeletons that interact synchronously with the human musculoskeletal system as a single human-machine system. The development is applicable to solving significant social and economic problems.

   This study aims at developing the concept of fragmentation of the frame to assess the load-bearing capacity of the floors.

   As a rule, a frame-rod design scheme is used under the finite element
modeling of high-rise buildings made of monolithic reinforced concrete. Numerical experiments using volume-rod and volume-plate models of a repeating structural fragment were performed on a test example of a six-span three-storey monolithic reinforced concrete frame. Practical recommendations have been developed for the refined strength calcula-
tion of the floors of monolithic reinforced concrete frames of multistorey buildings.
   Materials and Methods. Computational experiments were performed using the ANSYS Mechanical software package, in which the finite element method was implemented in the form of a displacement method. A plate-rod ensemble of finite elements was used to simulate the stress-strain state of a monolithic reinforced concrete frame. The refined calculation of the coupling zone of the floor slab and column under static loading was performed using solid, beam, truss and plate elements.
   Results. An engineering technique has been developed for numerical analysis of the stress-strain state of the coupling of the floor and the column of the reinforced concrete monolithic frame under static loading. The most accurate result was provided by a finite element model constructed using beam finite elements as reinforcing rods.
   Discussion and Conclusions. The developed technique of numerical modeling of the coupling of the floor and the column made it possible to estimate the real strength margin of this node, taking into account the real geometry of reinforcing grids, as well as to clarify the bearing capacity of a monolithic reinforced concrete frame under various loading scenarios.

   Introduction. A new scheme of a flat statically determinate regular lattice is proposed. The lattice rods are hinged.

   The study aims at deriving a formula for the dependence on the number of panels of the first natural oscillation frequency of nodes endowed with masses, each of which has two degrees of freedom in the lattice plane. The rigidity of all rods is assumed to be the same, the supports (movable and fixed hinges) — nondeformable.

   Another objective of the study is to find the dependence of the stresses in the most compressed and stretched rods on the number of panels in an analytical form.
   Materials and Methods. An approximate Dunkerley’s method was used to determine the lower bound for the lattice natural frequency. The lattice rigidity was found in analytical form according to Maxwell-Mohr formula. The rod stresses and the reactions of the supports were determined from the equilibrium equations compiled for all lattice nodes. Generalization of the result to an arbitrary number of panels was performed by induction using Maple symbolic math operators for analytical solutions to a number of problems for lattices with different number of panels.
   Results. The lower analytical estimate of the first oscillation frequency was in good agreement with the numerical solution for the minimum frequency of the oscillation spectrum of the structure. Formulas were found for the stresses in four most compressed and stretched rods and their linear asymptotics. All required transformations were made in the system of Maple symbolic math.
   Discussion and Conclusions. The obtained dependence of the first frequency of lattice oscillations on the number of panels, mass and dimensions of the structure has a compact form and can be used as a test problem for numerical solutions and optimization of the structure.

   Introduction. The safety problem and the situation with accidents during the operation of elevator installations are elucidated. The role of elevator rope defects as a factor of dangerous incidents is indicated from the point of view of statistics. The malfunctions of the elevator mechanical equipment related to the defective indices of the ropes are listed. There is a difference in the documentary fixation of defective indices and rejection rates of ropes of lifting structures.
   Materials and Methods. The well-known approaches to the control of ropes of lifting structures were described. It was emphasized that visual inspection control (VIC) was required to identify such rejection rates of steel elevator ropes as geometry change, corrosion and wear, wire breaks, temperature exposure, etc. The rejection rate was presented in the form of a mathematical system. The technical condition of elevator ropes during the operation was integrally assessed by the totality of identified defects at a fixed length. The decision to create a software and hardware complex (PAC) for the practical implementation of visual and measuring control was validated.
   Results. The developed PAC VIC laboratory sample consisted of a hardware part, a video stream processing module, communicator for the server connectivity, specially designed software, and a client mobile application. PAC VIC implemented the following functions: – automatic detection and classification of the major significant rope defects based on a deep convolutional artificial neural network; – demonstration of a three-dimensional image of a rope and an image scanning algorithm with distortion compensation, according to which the metric characteristics of defects were fixed; – integral assessment of the technical condition of the rope according to the totality of detected defects; – color interpretation of the actual technical condition of the rope with subsequent transmission to the user's mobile device. Preliminary tests have shown the suitability of the PAC VIC for identifying defects. The reliability of the results for the identification and qualification of defects exceeded 80%. Work on deep learning of the system continues.
   Discussion and Conclusions. PAC VIC of elevator ropes provides eliminating the risks of visual control caused by the psychophysical state of a person. It works remotely and contactless. The solution proposed by the authors automatically evaluates the rejection rates according to five criteria: external wire breaks, surface wear, rope diameter change, undulation, traces of temperature exposure. An important result of the VIC of steel ropes using computer vision and artificial intelligence is an increase in reliability and safety during the operation of elevator equipment.

   Introduction. Composite materials are the main way to reduce the weight of the aircraft structure and improve its flight performance. Methods of non-destructive testing enable to assess the technical condition of composite materials, as well as to determine stress concentrators in them to make a decision on the further operation of this control object. The paper presents an analysis of the use of composite materials in the aircraft design and ways to improve their flight performance through the application of composites. An acoustic-emission method for assessing crack resistance based on invariants was described.

   The study aimed at increasing the accuracy and efficiency of assessing the crack resistance of aircraft structures made of composite materials through the use of the acoustic emission method of non-destructive testing.
   Materials and Methods. The nomenclature of composite materials used in aircraft was given, and their physical and mechanical properties were compared. The acoustic emission method of non-destructive testing of composite materials based on invariant ratios was used.
   Results. A method for assessing the crack resistance of primary structural elements based on the invariants of acoustic emission processes, and a program apparatus complex based on it has been developed.
   Discussion and Conclusions. The results obtained can be used to determine the strength characteristics of composite materials by the acoustic emission method of non-destructive testing to assess the technical condition of primary structural elements in mechanical engineering, shipbuilding, and aircraft construction. The paper is recommended to researchers involved in the development of aircraft.

   Introduction. The key stages of sludge processing technology are the destruction of conglomerates into metal and non-metal components, as well as the grinding of component particles to obtain secondary raw materials of the required granulometric composition. The use of a rotating electromagnetic field for processing grinding sludge makes it possible
to exclude the application of various means of destruction and grinding, avoiding contact interaction of agglomerates and the walls of the working chamber. Thus, the material consumption of technical means is reduced, and the efficiency of the destruction process is increased.

   The study aimed at establishing the features and basic patterns of sludge waste processing in devices with a rotating electromagnetic field.
   Materials and Methods. For the research, grinding sludge was used, which was a collection of conglomerates of arbitrary shape, consisting of 80-85 % of metal chips. An induction method was applied based on establishing the connection of the EMF induced in an induction sensor and the magnetic induction of a rotating electromagnetic field. The influence of induction on the nature of interaction between sludge particles in a rotating electromagnetic field was evaluated by changing the relative EMF signal induced in an inductive sensor.
   Results. As a result of experimental studies conducted using the induction method, it has been found that the dynamic characteristics of sludge waste conglomerates depend on the induction of a rotating field to a certain value. With an increase in the size of sludge conglomerates, with the same size of ferromagnetic particles entering it, the magnitude of the magnetic field induction required for their destruction decreased. With a decrease in the particle size of conglomerates, the field induction required for the destruction of conglomerate bonds increased. An increase in the number of particles in the conglomerate reduced the value of induction. The degree of destruction of the conglomerate and the grinding of its ferromagnetic particles depended on the duration of the rotating electromagnetic field induction.
   Discussion and Conclusions. The proposed induction method makes it possible to investigate the influence of electromagnetic field parameters on the change in the state of the magnetic vibrating layer, as well as to evaluate the kinematic characteristics of ferromagnetic medium particles in the magnetic vibrating layer.

   Introduction. One of the tasks of two-link manipulators of industrial robots that move the end-effector along complex trajectories (e.g., robot welder) is associated with the need for careful programming of their movement. For these purposes, manual programming methods or training methods are used. These methods are quite labor-intensive, and they require highly qualified service personnel. A possible solution to the problem of programming the manipulator movements is the simulation of motion with the calculation of angular coordinates. This can help simplify the geometric adaptation of the manipulator in the process of debugging the control program.

   Therefore, this work aimed at calculating coordinates for programming the control system of a two-link manipulator operating in an angular coordinate system and moving the end-effector along a complex trajectory (e. g., when welding car bodies).
   Materials and Methods. A two-link robot manipulator designed for cyclically repeating actions in an angular coordinate system was considered. The manipulator consisted of two rotating links: “arm” and “elbow”, which were fixed on the base. The base could rotate, which provided a third degree of freedom. This configuration increased the working area of the manipulator and minimized the area for its placement in production. The movement of the manipulator end-effector could be performed if the kinematics provided its positioning along three Cartesian and three angular coordinates. For software control of robots, including welding robots operating in an angular coordinate system and performing the movement of the end-effector along a complex trajectory, it was required to calculate the angular coordinates of the movement of the end-effector of a two-link articulated manipulator. The robot control system should determine the position of the tool in the angular coordinate system, converting it for user friendliness into x, y and z coordinates of the Cartesian coordinate system.
   Results. The relations of angular and Cartesian coordinates have been obtained. They can be used for calculating when programming the control system of a two-link manipulator of an industrial robot and organizing the exchange of information between the user and the control system, as well as for checking the accuracy and debugging the movement of the end-effector of an industrial robot through feedback.
   Discussion and Conclusion. The presented results can be used for software control of a welding robot operating in an angular coordinate system and performing a complex trajectory of the end-effector of a two-link articulated manipulator (gripper). A manipulator operating in an angular coordinate system can be used for contact spot welding when moving the end-effector along a complex trajectory using a positioning or contouring control system. These systems control the movement of the end-effector along a given trajectory with the help of technological commands.

   Introduction. Robotic technologies serve as an important indicator of the technological and economic state of the country, they also affect the lives of individuals. Their development is a promising and urgent task affecting many aspects of the life of modern society. Currently, robotics is going through another stage of development, which has its own characteristics, new directions.

   The work aims at analyzing the situation and ways of development of this industry in the world and in our country, as well as the attitude of people to the use of robotic systems and their willingness to improve them.

   The topic under consideration is understudied.
   Materials and Methods. In the presented work, the historical aspects of the formation of unique robotic technologies are defined, the ratio of the number of manufacturers and consumers of robotic products in the world is specified, the areas of the robotic technology application are named. The central place in the research is given to the results of an online survey conducted by the authors. Its statistical analysis made it possible to study, using specific data, the factors that influence the spread of robotic systems and robotic technologies and contribute to them.
   Results. The survey results, on the one hand, showed a high assessment of the prospects of robotic systems given by the respondents, and confirmed that young people have an interest in robot-making technologies. On the other hand, they allowed us to note the high level of knowledge in the field of robotic technologies among engineering students and the presence of more than elementary knowledge of these technologies among representatives of other special fields. In the opinion of the authors, there are all prerequisites for the further successful development of these technologies.
   Discussion and Conclusions. The analysis of the use of robotics in the world and in our country, as well as the results of the survey conducted by the authors, enable to conclude that these technologies are developing and will continue to develop actively, and the interest of current students in this, confirmed by the answers to the questionnaire, will contribute to the wider introduction of robots into the lives of future generations.

   Introduction. In modern heavy-loaded friction units, metallopolymer coated bearings operating in the boundary friction mode are widely used. Their successful application is provided by the viscoelastic deformation of these coatings under load. To pass from boundary friction to liquid friction, it is required to create a bearing hydrodynamic wedge. Currently, the use of journal bearings with polymer-coated grooved support ring is hindered by the lack of a methodology for their calculation. This work analyzes a model of movement of a micropolar lubricant in the operating clearance of a journal
bearing with a nonstandard support profile having a PTFE composite coating with a groove on the bearing surface.

   The study aims at establishing the dependence of the stable hydrodynamic regime on the width of the groove on the surface of the bearing profile.
   Materials and Methods. Tribological tests of journal bearings with a nonstandard bearing profile having a polymer coating with a groove on the surface were carried out on samples in the form of partial bushes (blocks). Using the equation of movement of a lubricant with micropolar rheological properties, as well as the continuity equation, new mathematical models were obtained that took into account the width of the groove, polymer coating, and nonstandard bearing profile.
   Results. A significant expansion of the applicability of design models of journal bearings with structural changes has been achieved. Polymer-coated bearings with a groove provided a hydrodynamic lubrication mode. The results obtained allowed us to evaluate the operational characteristics of the bearing: hydrodynamic pressure value, load capacity, and coefficient of friction.
   Discussion and Conclusions. The design of polymer coated journal bearing and a groove 3 mm wide on the surface of the liner provided a stable ascent of the shaft on the hydrodynamic wedge, which was validated experimentally. The experiments were carried out for journal bearings with a diameter of 40 mm with a groove 1–8 mm wide, at a sliding speed of 0.3–3 m/s and a load of 4.8–24 MPa.

   Introduction. Life expectancy is, by definition, the average number of years a person can expect to live from birth to death. It is therefore the best indicator for assessing the health of  human beings, but also a comprehensive index for assessing the level of economic development, education and health systems . From our extensive research, we have found that most existing studies contain qualitative analyses of one or a few factors. There is a lack of quantitative analyses of multiple factors, which leads to a situation where the predominant factor influencing life expectancy cannot be identified with precision. However, with the existence of various conditions and complications witnessed in society today, several factors need to be taken into consideration to predict life expectancy. Therefore, various machine learning models have been developed to predict life expectancy.

   The aim of this article is to identify the factors that determine life expectancy.
   Materials and Methods. Our research uses the  Pearson  correlation coefficient  to assess correlations between indicators, and we use multiple linear regression models,  Ridge regression, and Lasso regression  to measure the impact of each indicator on  life expectancy .  For model selection, the Akaike information criterion, the coefficient of variation and the mean square error were used. R² and the mean square error were used.
   Results. Based on these criteria, multiple linear regression was selected for the development of the life expectancy prediction model, as this model obtained the smallest Akaike information criterion of 6109.07, an adjusted coefficient of 85 % and an RMSE of 3.85.
   Conclusion and Discussion. At the end of our study, we concluded that the variables that best explain life expectancy are adult mortality, infant mortality, percentage of expenditure, measles, under-five mortality, polio, total expenditure, diphtheria, HIV / AIDS, GDP, longevity of 1.19 years, resource composition, and schooling. The results of this analysis can be used by the World Health Organization and the health sectors to improve society.

   Introduction. To develop new system modules of software to help employees with disabilities, it is required to work out an architectural solution for the interaction of all parts of the system. As a result of the analysis and design, it is necessary to obtain a software architecture that must meet a number of standard requirements. First of all, it should be safe. To do this, you should take into account the error logging system, event auditing, the possibility of disabling the functionality immediately after putting it into commercial operation, internal mechanisms for validating client input requests and server responses. This study is aimed at the development of basic system maintenance options, the analysis of exception cases under interacting with the user for further evaluation of the architecture efficiency, and the direct project development.
   Materials and Methods. The architectural decision was carried out using the Unified Modeling Language (UML), which helps to build visual images of the life cycle and interaction of all components of the system. The syntax of the UML deployment diagram was used to study the interaction of the main modules of the future system, and the syntax of the UML sequence diagram was used to process the lifecycle. A use case diagram was also applied to describe the main use cases. To study the interaction of the main modules of the future system, the UML deployment diagram syntax was used. For life cycle processing, the UML sequence diagram syntax was applied. In addition, a use case diagram was applied to describe the base use cases.
   Results. An architecture that has a scheme for the interaction of individual modules and systems, as well as options for using the software package for the future implementation of the software product, has been developed. The proposed system architecture meets the requirements of security, reliability (fault tolerance), and performance. The authors have fixed the functional requirements of the system of assistance to employees of enterprises with hearing problems for the possibility of their employment and work on the telecommunication Internet. Basic variations of system maintenance have been developed.
   Discussion and Conclusions. Building a competent architecture provides taking into account cases that go beyond the normal use of the system, and applying a fuzzy model to determine the system efficiency. Further in-depth description of deployment and operation options will enable to implement an efficient and productive system.