Application of computer systems for modeling dynamic processes of lifting machines

The main task of mechanical engineering is to organize the production of a range of machines to meet the needs of all industries. These are power, transport, lifting and transport units, agricultural machinery, construction industry, etc. Among them, one can single out devices in which the relative movement of their parts is assigned, that is, kinematic pairs are included in the calculation models. The real operating conditions of machines are varied, but most often they are associated with periodic starts-stops, which determines the relevance of the study of unsteady modes. The analysis of the operation of such models becomes more complicated. For successful design results, mathematical modeling of individual processes in mechanisms is carried out. One of the first calculations is dynamic. Modern, available CAD / CAE systems for modeling and analysis provide automation capabilities, building more realistic design models. The paper discusses the approbation of the use of CAD for modeling the dynamics of a jib crane with a set of four units: platform, boom, sleeve and rod. The developed model is combined: the platform and the sleeve correspond to the kinetostatic model, and the boom and rod are elastic. The crane is designed to perform lifting operations in a vertical plane, with the possibility of relative movement in 3 rotational and one translational kinematic pairs. The performed calculations of the static, modal and dynamic analyzes of the links of the mechanism confirm the adequacy of their models. Among them is the task of instantaneous load application, which is typical for the "lifting and picking" operating mode of crane lifting mechanisms. The deformation of the entire structure in one of the boom positions is also considered. The determination of the reaction forces in the hydraulic cylinder provides important information for the selection of the power unit.

Method of analysis of the current state of inertial characteristics of an autonomous mobile robot of variable configuration

The features of the dynamics of an autonomous mobile robot (AMR) of variable configuration with the relative movement of attachments are considered. Analysis of the current state of inertial characteristics during AMR operation will ensure stable movement along a given trajectory, successful implementation of technological operations by attachments, and preservation of the robot's functionality when operating under undetermined or extreme conditions. At the design stage, the analysis of the inertial characteristics of the AMR will make it possible to refine the parameters of the mathematical model, improve the algorithms for adaptive control and correct the commands for the actuators. Figs.: 2. Tabl.: 2. Bibliogr.: 10 titles. Keywords: autonomous mobile robot, inertial characteristics.

ROTATION JOINTS FRICTION IN A TRANSVERSAL MOBILE COUPLING

The transversal mobile couplings are used in movement and torque transmission between two main shafts having parallel axis, with the possibility to undertake misalignments in the transversal plane. These shaft misalignments are usually named transversal movements. The paper presents, starting from some kinematic aspects regarding relative movements between the coupling parts, the kinematic equations useful in determining position of the intermediary elements, depending by the transversal misalignments. Following this, using the inside relative movement in rotation joints between parts and corresponding adequate materials, the friction coefficient is studied. The friction which appears in coupling’s rotation joints between the involved parts has an important influence on their dynamic behaviour, wear and lifetime. The most significant friction and also wear is given by the alternant rotation movements in joints between parts, at the ends of their angular stroke. Due to this, the study of the friction between some materials to be used in coupling manufacturing is required, but also difficult because of some particularities, as reduced rotation in joints, for reduced transversal misalignments between the main shafts. There are presented, in the paper final part, the results and conclusions.

Smart Clothing as a Noninvasive Method to Measure the Physiological Cardiac Parameters

In response to global aging, there have been improvements in healthcare, exercise therapy, health promotion, and other areas. There is a gradually increasing demand for such equipment for health purposes. The main purpose of smart clothing is to monitor the physical health status of the user and analyze the changes in physiological signals of the heart. Therefore, this study aimed to examine the factors that affect the measurement of the heart’s physiological parameters and the users’ comfort while wearing smart clothing as well as to validate the data obtained from smart clothing. This study examined the subjective feelings of users (aged 20–60 years) regarding smart clothing comfort (within 12 h); the median values were comfortable and above (3.4–4.5). The clothing was combined with elastic conductive fiber and spandex to decrease the relative movement of the fiber that acts as a sensor and increase the user’s comfort. Future studies should focus on the optimization of the data obtained using smart clothing. In addition to its use in medical care and post-reconstructive surgery, smart clothing can be used for home care of older adults and infants.

Design and Analysis of Parallel Mechanism with Linear Drives Located on the Base at Specified Angles

The article considers a novel parallel mechanism with drives located on the base at different angles to its plane. This arrangement allows performing a relative movement between objects under water or in space (in aggressive environments). The new mechanism topology is compact for transportation and efficient for operation in aggressive environments. Structural synthesis has been performed; the number of degrees of freedom of the output link was calculated. A general approach to solving the inverse kinematics problem of positions is proposed and an example for a kinematic chain is shown. Denavit — Hartenberg matrices are used to solve the problem of positions. The position of the output link described by this matrix is used to represent the points of this link in the base coordinate system. The constraint equations are applied, which are the distances between the points of the base and the output link.

IMPLICAÇÃO DE ANÁLISES TRIBOLÓGICAS NA REALIZAÇÃO DA MANUTENÇÃO PREDITIVA

In predictive maintenance, interventions are dependent on information from the monitoring of parameters, their main advantage is the reduction of periodic stops, increasing the time of availability of equipment and decreasing costs. Subjects such as wear, lubrication and surfaces with relative movement are studied by tribology. The purpose of this article was to investigate the relationship between tribology and predictive maintenance. The basis for scientific foundation was bibliographic research in studies by different authors. Thus, it is concluded that tribology has significant relevance in performing predictive maintenance, especially in view of the analysis of lubricating oil and wear of particles. These analyzes and correct implementation were considered, being a fundamental point for companies that seek to increase their competitiveness. However, scarcity was observed in practical case studies, which demonstrates that the relationship between maintenance and tribological factors needs to be studied more deeply.

Comparing the physical principles of action of suspension damping devices based on their influence on the mobility of wheeled vehicles

This paper reports the comparison of two physical principles of action of suspension damping devices based on their influence on the mobility indicators for an 8×8 wheeled machine. A radical difference between these principles of action is the dependence of resistance forces on the speed of the relative movement of working bodies (internal friction: hydraulic shock absorbers) or on the relative movement of working bodies (external friction: friction shock absorbers). Widespread hydraulic shock absorbers have certain disadvantages that do not make it possible to further increase the mobility of wheeled or tracked vehicles without the use of control and recuperation systems. In turn, in friction shock absorbers, the use of new materials has eliminated many of their shortcomings and thus can provide significant advantages. It was established that the application of friction shock absorbers for a given wheeled vehicle did not significantly affect the speed compared to hydraulic ones. The main factor that prevented the implementation of the advantages of friction shock absorbers was the insufficient suspension travel. However, friction shock absorbers absorbed 1.76...2.3 times less power, which reduced the load on nodes and increased efficiency (autonomy). In addition, a more uniform load on suspensions was ensured, which improved their resource, and, due to the prevailing vertical oscillations of the suspended body over the longitudinal-angular ones, the geometric passability improved as well. The comparison of two physical principles of action of damper suspension devices in a wheeled vehicle has shown that the use of friction shock absorbers could provide significant advantages in resolving the task relates to improving the mobility and would fundamentally affect the choice of the suspension energy recuperation system if it is applied.

Comparative analysis of three categories of four-DOFs exoskeleton mechanism based on relative movement offsets

Purpose The purpose of this paper is to evaluate three categories of four-degrees of freedom (4-DOFs) upper limb rehabilitation exoskeleton mechanisms from the perspective of relative movement offsets between the upper limb and the exoskeleton, so as to provide reference for the selection of exoskeleton mechanism configurations. Design/methodology/approach According to the configuration synthesis and optimum principles of 4-DOFs upper limb exoskeleton mechanisms, three categories of exoskeletons compatible with upper limb were proposed. From the perspective of human exoskeleton closed chain, through reasonable decomposition and kinematic characteristics analysis of passive connective joints, the kinematic equations of three categories exoskeletons were established and inverse position solution method were addressed. Subsequently, three indexes, which can represent the relative movement offsets of human–exoskeleton were defined. Findings Based on the presented position solution and evaluation indexes, the joint displacements and relative movement offsets of the three exoskeletons during eating movement were compared, on which the kinematic characteristics were investigated. The results indicated that the second category of exoskeleton was more suitable for upper limb rehabilitation than the other two categories. Originality/value This paper has a certain reference value for the selection of the 4-DOFs upper extremity rehabilitation exoskeleton mechanism configurations. The selected exoskeleton can ensure the safety and comfort of stroke patients with upper limb dyskinesia during rehabilitation training.

EMDA: A Python package for Electron Microscopy Data Analysis

An open-source Python library EMDA for cryo-EM map and model manipulation is presented with a specific focus on validation. The architecture of the library and its programmable and command-line interfaces are presented. The use of several functionalities in the library is presented through several examples. The utility of local correlation as a metric for identifying model errors and unmodeled regions in maps, and how it is used as a metric of map-model validation is demonstrated. The mapping of local correlation to individual atoms, and its use to draw insights on local signal variations are discussed. EMDA`s likelihood-based map overlay is demonstrated by carrying out a superposition of two domains in two related structures. The overlay is carried out globally to bring both maps into the same coordinate frame and then locally to estimate the relative movement of domains. Finally, the map magnification refinement in EMDA is presented with an example to highlight the importance of correcting map magnification in structural comparison studies.