The rapid development of electrical engineering industries for aviation has resulted in a gradual transition to the autonomous electrohydraulic drives, among which an electro-hydrostatic drive is currently considered to be the most advanced. However, high requirements for dynamic parameters of modern unstable and low-stability aircrafts put restriction on implementation of electro-hydrostatic drives in the industry.

A combined control hydraulic drive arisen from the electro-hydrostatic drive development solves the problem of low dynamic parameters. High dynamics for combined control is achieved through the use of double (throttle and electric power) control with each of them being predominant depending on the input signal value.

Due to small knowledge of the drive with combined control, the article proposes to use a multi-criterion optimization method in order to obtain optimal results in its development. This will allows an adequate estimate of drive performance for its comparison with analogues and a justification of the feasibility of further research as well.

The article describes all the stages of multi-criteria optimization of the combined control drive using the LP-search method. Optimization is carried out taking into account the requirements for modern aircrafts. As criteria, were taken three values , which, in the authors' opinion, provide the most complete description of the entire drive quality (a drive power consumption in the "neutral", an efficiency of the hydraulic part of the drive in the mode of electric power control, a value of ITAE when driving with a small signal). As a result of optimization, the Pareto front was obtained in three coordinates, corresponding to effective solutions, after which a compromise between the criteria was found, and the optimal solution was chosen.

The design solution of the combined control drive, obtained after optimization, meets all the requirements for modern aircrafts and has both the high power performance and the high dynamics. Nevertheless, this study should be considered incomplete because of not taking into account a number of parameters, including weight-size and drive reliability ones.

One of the most important trends in development of machine engineering is to improve load capacity of mechanisms, assemblies and parts without increasing their overall dimensions and weight. This is also relevant to the most promising items so far, i.e. orbital roller drives (ORD), which are the rotational-to-progressive motion converters widely used in vehicles. The previously published article suggested increasing a load capacity (by about 15%) through reducing a thread turn section angle of the threaded ORD components and change of the radius of roller thread turn section outline. Due to such ORD modification, a number of the most critical ORD parameters are to be changed thereby demanding further research. Further, the article published suggests a method considering the abovementioned changes to calculate the dimensions of ORD main components and their tolerance ranges.

Though this method being not complete as the increment of ORD center-to-center spacing in relation to its rated value, required for assembly, is unknown; and to determine the ORD center-to-center spacing increment, outer diameters of the roller and screw threads are to be known. Hence, these two methods are interconnected.

This article presents the numerical calculation method, mathematical support and method to determine the increment of ORD center-to-center spacing and initial contact point of the mating roller and screw thread turns. Due to considerable scope of calculations, the method was turned into the software.

Similar calculation methods and techniques were developed to a particular case, where the thread turn section angle of the threaded components was of 90°, and the roller thread turn section outline was a circular arc centered to the roller axis. Hence the developed numerical calculation method, mathematical support and technique refer to the general case which is to determine the ORD center-to-center spacing increment and initial contact point of the mating roller and screw thread turns. Taking this into account, the calculations for a particular case were performed as test calculations during the software development. The results obtained matched the calculation results for a particular case published in several papers.

Using a developed calculation technique, the calculation method to determine dimensions of ORD main components and their tolerance ranges may be completed for a general case considering the arbitrary turn section angle of threaded ORD components and radius of roller thread turn section outline.

The paper conducts a feasibility analysis for using a topology optimization (TO) when designing the gears for advanced engines.

The goal of TO is to find an optimal material distribution in designing area for given loads with constraints consideration. This study performs 3D computations using a finite-element analysis.

Optimization of the certain statements of the problem has been provided. In case 1 an increasing rigidity of diaphragm of the helical gear with decreasing mass was specified, as a criterion. As a result of optimization there were two conical sections getting into one thin wall, connected at the face where the axial force is applied. Some aviation engine and helicopter transmission schemes have a similar embodiment of a diaphragm of the helical gear. In case 2 the frequency detuning was carried out. The result is a complicated design, containing closed cavities, so it is hard to manufacture it by traditional manufacturing methods. Case 3 solves a problem of increasing torsional rigidity with mass restrictions. The optimized design has a splitting diaphragm and a closed cavity.

The final calculation is carried out for case 1. As a result, maximum displacements for initial and optimized designs are obtained. The analysis and comparing results have shown that the optimized design has over 2 times increased diaphragm rigidity as compared to the initial design, with mass being 10 % less and equivalent stresses reduced by 13%.

With development of compressed air drying equipment, the task of numerical modeling of dynamic sorption-regeneration processes is increasingly emerging at the design stage. The dynamic problem has no analytical solution and can be solved only by numerical methods.

The paper presents a numerical method and a program developed to calculate dynamics of heat and mass transfer during adsorption drying of compressed air.

As a basis, a simplified physical model of sorption kinetics is used which assumes that inside the granules of the adsorbent there is a complete equalization of parameters such as temperature and moisture content at any time. The parameters of thermal conductivity and diffusion inside the adsorbent granules are incomparably higher than similar parameters on the surface of granules.

Based on the thermodynamic approach, a physical and a mathematical model of adsorption have been developed to calculate dynamic non-isothermal processes in adsorption drying apparatuses. The presented results of calculations confirm the possibility to analyze dynamics of heat and mass transfer processes in the dryer column in the moisture adsorption mode under various initial and boundary conditions, including those that vary within the drying cycle.

The thermal physics parameters and a cutting temperature belong to the output performances to characterise a process and allow a rational selection of machining modes and conditions. In machining hard-to-cut materials the utmost cutting temperature is a technological restriction and defines tool wear rate and intensity. The cutting temperature also has impact on the heat extension of tool and the finished machining.

The subject is to study thermal physics parameters and cutting temperature when machining the plastic materials by a hard-alloy tool. The objective is to develop a technique to calculate these parameters. A calculation method for the analysis of process parameters is used.

Calculation results for the cutting temperature were compared with experimental ones published in the literature sources. A novelty of the technique is that there is no need in conducting the experimental studies to calculate the thermal physics parameters. Calculation is based on using known mechanical and thermal physics characteristics of machined and tool materials. The calculation results are parameters, namely heat flow intensities in the conditional shear plane, on the contact surfaces of tool, temperatures of theses surfaces, averaged cutting temperature - depending on the cutting speed, thickness of cutting layer, tool wear value.

A sequence of calculations is implemented in the developed software in the programming algorithmic language with results in graphic and tabular representations. The calculation technique is designed for conducting research activities and engineering designs in the field of machining.