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Kinematic synthesis of the mechanism for static balancing of an input torque in three positions

Buśkiewicz Jacek

Archive of Mechanical Engineering

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2022

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LXIX, nr 4

571--594

EN

The aim of this work is to design the links-spring mechanism for balancing, in the three positions of the operating range, a rotary disc subjected to a torque. An energy-related approach towards the conditions of the mechanical system balance for a discrete number of positions leads to the formulation of a task of searching for a four-bar linkage which guides a coupler point through the prescribed positions, where, at the same time, geometrical conditions (specifying the spring tension) and kinematic conditions (defining the radial component of the tension change rate) are satisfied. The finitely and infinitesimally separated position synthesis is considered, however, only a component of the coupler point velocity is essential. A general method was proposed for determining the four-bar mechanism geometry. Mechanism inversion was applied in order to reduce the number of designed variables and simplify the solution method. The system of complex algebraic equations defines the problem. Linear, symbolic transformations and a systematic search technique are utilized to find multiple local optimal solutions. The problem is solved using Mathematica software.

2

Numerical and experimental analyses of a lighting pole in terms of passive safety of 100HE3 class

Jedliński Tomasz, Buśkiewicz Jacek, Fritzkowski Paweł

Vibrations in Physical Systems

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2020

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Vol. 31, nr 3

art. no. 2020307

EN

Nowadays trends related to the road safety make the lighting poles producers meet rigorous requirements that decrease the risk of death and injury of vehicle drivers in case of the impact. New requirements are in force from 1 January 2015, when Road and Bridge Research Institute informed that each pole liable to a direct vehicle impact has to meet Standard PN-EN 12767. The article presents the design of a novel, safe lighting pole. The novelty lies in the pole simplicity, which results in the manufacturing technology the cost of which is comparable to that of the conventional pole. Compared to the conventional poles of thickness 3 mm and greater, this one is made of thin-walled steel sheet of increased strength parameters and specially designed sleeve that is fixed to the base plate. The crash tests carried out on the track for the impact experiments proved that the requirements of the standards in the driver highest safety class and in the high vehicle kinetic energy absorption were satisfied both for the speed impact 35 km/h and 100 km/h. The numerical model for simulations of the vehicle behaviour during and after the impact was implemented in software Ansys LS-Dyna. The simplifications of some elements were of negligible influence on the analysed phenomena. The comparative parameters were ASI, THIV and exit velocity of the vehicle. The numerical results were close to the empirical ones, therefore they confirmed that finite element analysis can be successfully applied at the stage of elaborating of the initial concepts of the road lightning poles. It follows that the number of expensive crash tests can be reduced.

3

Analysis of the relationship between selected stability assessment indicators on the example of leaning out the human body from the upright position

Matuszewska Agata, Buśkiewicz Jacek

Vibrations in Physical Systems

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2020

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Vol. 31, nr 2

art. no. 2020219

EN

The objective of this paper is to study the margin of stability when trying to lean out the body forward and backward. The centre of mass of the body, the velocity of the centre of mass and extrapolated centre of mass were calculated for four participants. The analyzed movement was recorded by using BTS Motion Capture system. Recordings, in which participants were unable to return to the upright position, were also observed. In these cases, it was verified the usefulness of extrapolated centre of mass for predicting the foot support area that enables maintaining the body balance. The relationship between the applied stability indicators and anthropometric parameters was determined. The preliminary results obtained confirm the validity of the use of selected parameters in tests and in assessment of the stability of the human body, and indicate the directions of further tests for a larger group of participants and other movement activities.

4

Zastosowanie systemu analizy ruchu BTS do określenia chwili utraty stabilności

Matuszewska Agata, Liszkowski Jakub, Walczak Tomasz, Buśkiewicz Jacek

Aktualne Problemy Biomechaniki

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2019

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z. 17

69--76

PL

W pracy przeprowadzono próbę wyznaczenia chwili utraty stabilności dla upadków z pozycji statycznej. Pozycją początkową, jaką przyjmowała osoba badana, było stanie na dwóch nogach z rękami wzdłuż tułowia. Rejestracji ruchu dokonano dzięki wykorzystaniu systemu BTS. W celu wyznaczenia chwili utraty stabilności zaproponowano i opracowano własne miary i parametry, bazujące na pomiarach wykonanych z użyciem platform dynamometrycznych oraz systemu analizy ruchu. Dla analizowanego przypadku ruchu wielkości te pozwoliły na szacunkowe wyznaczenie chwili utraty stabilności.

EN

Assessing of human stability loss was performed at this work in case of falls from a static position. At the beginning patient takes the starting position as standing on two legs with hands along the thorax. Human motion registration was performed by using BTS system. In order to determine the instant of human stability loss the new measures and parameters were proposed, which based on measurements from force platforms and motion analysis system. These parameters allowed to assess the instant of stability loss for analyzed motion.