Vol 22, No 2 (2023)

Design models and algorithms have been developed to estimate the spatial direction of the reorientation of spacecraft for optoelectronic observation of the Earth’s surface during object shooting, taking into account the relative movement of the surveillance objects in the field of view of the spacecraft. Modeling is simplified due to the choice of such coordinate systems in which the spacecraft is stationary and the surveillance objects move relative to it. The direction of rotation of the spacecraft with a given angular velocity is found at the point of the upcoming intersection of the optical axis of the observation equipment on the Earth’s surface with the surveillance object moving in the selected coordinate system. The models and algorithms were developed in order to expand the capabilities of Samara University’s existing software package for evaluating the target indicators and design characteristics of observation spacecraft. Based on the developed re-targeting models, algorithms have been developed for selecting the sequence of shooting observation objects according to the criterion of their  maximum number on the orbit of the spacecraft flight and counting the captured objects to assess the performance of survey. An example of the implementation of one of the graphic windows of the software with the developed models and algorithms is given, in which the process of re-targeting the spacecraft is visualized, which is one of the ways to verify the adequacy of the developed models and algorithms.

The paper presents a method for determining the frictional moments of the oscillation groups of the most widespread domestically made liquid propellant engine steering units. This is a topical issue requiring investigation to improve the efficiency and reliability of oscillation groups. The reason for the occurrence of an additional axial force in the radial bearings of the articulated joints that leads to an overestimation of the actual values of the moments relative to the theoretical values is shown. The procedure for calculating the maximum axial force and the accompanying increase in the moment, confirmed by the analysis of the results of the bench test of the experimental steering unit, is presented. An assessment of the range of axial forces in the absence of blocking of the axial movement of the bearing was carried out with a simultaneous analysis of the suitability of the existing methods for calculating the increase in the frictional moment for the obtained ratios of axial and radial loads. The direction of further research of low-speed radial bearings is determined, aimed at increasing the reliability of calculations and developing measures to minimize the frictional moment of production oscillation units.

The purpose of this work was to develop effective methods for calculating the wear rate of raceways and roller bearings under dynamic loads. The wear of the working surfaces of rolling bearings in many practical cases is an important critical factor affecting their performance and durability. However, only a limited number of publications are devoted to this issue. In most of them, Archard's law, which has been experimentally confirmed during hydrodynamic friction of bearing steels, is used to calculate the wear rate of the contacting surfaces. Based on this law, the article presents a method of direct step-by-step calculation of the wear rate at variable contact loads and sliding speeds. In accordance with it, the change in the normal force, sliding speed and thickness of the oil film in contact is determined in the dynamic calculation of the bearing, and the finite element method is used to calculate the contact pressure field. The multi-mass model of bearing dynamics includes a contact friction model that allows adequately reproducing the conditions of hydrodynamic contact of solids. The direct calculation method involves a large number of calculations that make the impact of individual factors on the wear rate opaque. Therefore, along with it, a method for calculating the wear rate by averaged parameters is proposed. Using these two methods, the wear calculations of the raceway of the inner ring and the rollers of a double-row tapered roller bearing were performed. The comparison of the results confirms the acceptable accuracy of the calculation according to the averaged parameters.

A method for selecting parts and assembly units (hereinafter briefly referred to as parts) in sets for assembling a batch of electrohydraulic servo drives is presented, based on the measured (individual) mechanical and hydraulic characteristics of the parts. The preparatory stage is described: construction of a mathematical model of the product, determination of the parameters of parts and adjustments that have the greatest impact on the parameters of end products, formation of a system for assessing the quality of products in the batch, mathematical formulation of the task of selecting parts. The task of selecting parts is formulated as the assignment problem in the maximin formulation. A deterministic algorithm for solving the problem is presented, based on the branch and bound method and taking into account the fact that adjustments are made during the assembly of drives. A significant reduction in the number of steps (iterations) when searching for the optimal distribution of parts across assembly sets achieved due to the chosen mathematical formulation of the task, as well as due to the chosen strategy of selecting parts in the next assembly set. We suggest that an assembly set should include, first of all, the “most troublesome” parts the parameters of which do not allow obtaining a set, the projected quality indicator of which will be higher than the established value. At the same time, the negative impact of these parts on the product parameters is compensated by combining them with other parts in one assembly set. The results of mathematical modeling of assembling 992 drives with random formation of assembly sets and with individual selection of parts are presented. Modeling shows that as a result of implementing individual selection of parts in accordance with the described method, a significant reduction in the spread of parameters of end products within batches can be expected, as well as improvements in functional performance of the products. The presented method of individual selection of parts can be used in the assembly of various products.

One of the most important tasks in the manufacturing of aerospace products is the control of their geometric parameters at various stages of production and assessment of their compliance with the requirements of design documentation. The use of laser automated measuring systems makes it possible to increase the measurement speed and to use the product digital model as a reference point.  The best results in solving such problems can be obtained using laser automated measuring systems, such as laser scanners and laser trackers. In this paper a two-position measurement system is applied to control the aluminum alloy fuel component tank of the designed launch vehicle with two modes of static loading, corresponding to different transportation conditions. In this case, the linear dimension error should not exceed 150 µm. A mathematical model of a multi-position measuring system is constructed and measurement uncertainty equations are obtained. In this case, the error function value that represents the difference between the errors in determining the coordinates of the reference points and the controlled points of the measurement object should be minimal. This mathematical model will be further used for numerical modeling that will allow selecting the optimal configuration of a measuring system for multi-position control of the tank geometric parameters in the static loading process.

The energy efficiency of controlled vibration protection systems is defined as the ratio of the vibration safety indicator they achieve to the cost of energy resources necessary to achieve the desired indicator. To solve the optimization problems of controlled vibration protection, a sufficient condition for the optimality of the accepted functional and, accordingly, the minimum principle, was used, the step-by-step implementation of which, in the course of numerical integration of the initial equations of the state of the system, makes it possible to reproduce the optimal control numeric arrays and the related components of the system state. The algorithm of the step-by-step procedure of the minimum principle was used to optimize the dynamic processes in the vibration protection system with indirect control of the viscous resistance damper and the potential energy recuperator. It has been established that the optimal controls that allow eliminating resonant phenomena in these systems are positional functions of a singular type, the relay switching of which in vibration protection systems with a controlled damper and recuperator is associated with a change in the sign of the absolute and relative velocity of the object and with a change in the sign of the velocity and relative displacement of the object.