Dynamical Characteristics of a Hydraulic Soft Actuator With Three Degrees of Freedom

In recent years, increasing attention and expanding research have been devoted to the study and application of soft actuators. Inherent compliance equips soft actuators with such advantages as incomparable flexibility, good environmental adaptability, safe interaction with the environment, etc. However, the highly nonlinear also bring challenges to modeling of dynamics. This study aims to explore the dynamical characteristics of an underwater hydraulic soft actuator. The actuator has three fiber-reinforced elastomer chambers distributed symmetrically inside. By controlling the pressure in the chambers through a hydraulic power system, the actuator can achieve spatial motion with three degrees of freedom. To describe the relationship between the input pressure combination and the actuator movement, a dynamic model considering the nonlinearity of viscoelastic material is developed based on Lagrangian method and constant curvature hypothesis. A series of experiments are carried out, including single-chamber actuation and multi-chamber actuation. The test results verify the effectiveness and precision of the model. Finally, the effects of the geometrical features on dynamic response are investigated through model-based simulation, which can provide guidance to parameter optimization. The proposed dynamic model can also contribute to behavior analysis, performance prediction, and motion control of the hydraulic soft actuator.

SYNTHESIS OF HIGH-CLASS MECHANISMS OF VARIABLE STRUCTURE BASED ON DYNAMIC ANALYSIS

This paper presents the model of a high class variable structure mechanism. These mechanisms have not gained widespread acceptance in practice, despite obvious improvements in the ability to transmit motion and power. The article presents a synthesized high class mechanism. The block diagram of the formation of the mechanism is shown, the results of synthesis are presented. It is shown that with a relatively compact kinematic scheme, it is possible, with one drive, to create a system with several working links providing various technological operations, that is, on the basis of one mechanism, it becomes possible to create automatic mechanisms. In these studies, the development of a methodology for the dynamic design of the variable structure mechanism based on the analysis of dynamics and assessment of the influence of nonlinear factors on the quality of the machine as a whole was carried out. To study the motion of such variable structure mechanism, mathematical modeling of dynamics with discontinuous coefficients and nonlinear external forces is used.

The Current State and Tendencies of Development of the Enterprises in Ukraine According to Their Sizes

In the conditions of the formation of a market economy in Ukraine, a significant role is given to the development of entrepreneurship as the driving force for the intensification of the activities of economic entities. An analysis of the current state and tendencies in entrepreneurship development of Ukraine was carried out taking into account the criteria for the division of enterprises into micro, small, medium-sized and large in conformity with the legislation of Ukraine. The information base of the research was statistics published on the website of the State Statistics Service of Ukraine for the period 2010-2019. The article describes the dynamics for 2010-2019 of such indicators of efficiency of large, medium and small (including micro) enterprises of Ukraine: level of profitability (unprofitability) of operational activity of enterprises; level of profitability (unprofitability) of all activities of enterprises; proportion of enterprises that received net profit; structure of distribution of capital investments; number of enterprises; volume of sold products (goods, services) of enterprises. The structural distribution of indicators of efficiency of Ukrainian enterprises by type of economic activity for 2019 is displayed. With the help of econometric modeling of dynamics of the number of enterprises, volumes of capital investment and sold products of Ukrainian enterprises for 2010-2019, a trend equation (polynominal type) is built. Summarizing the results of researches, Ukrainian enterprises were divided into large, medium, small and micro enterprises by the value of performance indicators during 2010-2019. To characterize the level of riskiness of activities for each category of enterprises, variation coefficients for the performance indicators of Ukrainian enterprises for the period 2010-2019 were computed. The advantages and disadvantages of organization and functioning of enterprises of different categories are systematized. For the balanced development of the market economy, the need for cooperation and the formation of an efficient mechanism for interaction of all forms of entrepreneurship – small, medium and large, each of which has its own advantages and disadvantages, is substantiated.

MODELING OF DYNAMICS OF PSYCHOLOGICAL STATE OF THE PERSONNEL OF DISABLED SUBMARINE IN DIFFERENT ACCIDENT PERIODS

Aim: theoretical study and modelling of dynamics of psychological state of the personnel of disabled submarine in different accident periods.Materials and methods: theoretical analysis of literature sources in the context of psychological states of a person in emergency cases, including in seafarers divers, and materials describing chronology of accident progression at submarines.Results and discussion: from the results of analysis of studies of psychological states and available information about accidents at submarines, systematization of theoretical data was carried out and factors affecting the change of psychological states of submarine personnel in different accident periods were described.

A new forecast model for fluctuating Pattern of Covid-19 spread in South Asia

Exponential growths are observed in several natural phenomena, including cosmological expansion of the universe, nuclear fission, population growth, global viral spread, and financial markets fluctuations. Several deterministic and stochastic methods have been used for the modeling of dynamics of these phenomena. Global reliable data are essential to parameterise a defined model so as to enhance confidence in model outputs. Four-parameter logistic model comes out to be best forecast model for the total Covid-19 infected people in Pakistan and India. Five-parameter logistic model is best forecast model for Bangladesh. Simulation results revel that maximum total number of cases will be about 1.0, 0.6 and 0.25 million in India, Pakistan and Bangladesh respectively. Covid-19 infected rate will be closed to 11000, 8000 and 2000 cases per day during peak period in these countries.