Paweł Hołobut

Paweł Hołobut
Institute of Fundamental Technological Research · Department of Mechanics of Materials

About

22
Publications
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141
Citations

Publications

Publications (22)
Article
The aim of this study is to analyse the joint effect of reinforcement shape and packing on the effective behaviour of particulate composites. The proposed semi-analytical modelling method combines the Replacement Mori–Tanaka scheme, by means of which the concentration tensors for non-ellipsoidal inhomogeneities are found numerically, and the analyt...
Preprint
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We present a distributed framework for predicting whether a planned reconfiguration step of a modular robot will mechanically overload the structure, causing it to break or lose stability under its own weight. The algorithm is designed to be executed by the modular robot itself and is based on an distributed iterative solution of mechanical equilib...
Article
Full-text available
We present a distributed framework for predicting whether a planned reconfiguration step of a modular robot will mechanically overload the structure, causing it to break or lose stability under its own weight. The algorithm is executed by the modular robot itself and based on a distributed iterative solution of mechanical equilibrium equations deri...
Conference Paper
Full-text available
Large-scale 3D autonomous self-reconfigurable modular robots are made of numerous interconnected robotic modules that operate in a close packing. The modules are assumed to have their own CPU and memory, and are only able to communicate with their direct neighbors. As such, the robots embody a special computing architecture: a distributed memory an...
Article
Full-text available
The issue of applicability of the Morphologically Representative Pattern (MRP) approach to elastic-plastic composites is addressed. The extension to the regime of non-linear material behaviour is performed by employing the concept of incremental linearization of the material response in two basic variants: tangent and secant. The obtained predictio...
Article
Full-text available
We propose a methodology of planning effective shape shifting and locomotion of large-ensemble modular robots based on a cubic lattice. The modules are divided into two groups: fixed ones, that build a rigid porous frame, and mobile ones, that flow through the frame.Mobile modules which flow out of the structure attach to the frame, advancing its b...
Chapter
This paper presents the measurement and model updating of a pedestrian’s center of mass trajectory. A mathematical model proposed by the authors is updated using the actual trajectory of a pedestrian. The mathematical model is based on the principle that a human’s control capability tries to maintain balance with respect to the pedestrian’s center...
Conference Paper
Full-text available
We discuss selected mechanical aspects of self-reconfiguration of densely-packed modular robots. The change of connection topology and transport of modules are fundamental mechanisms for these systems, which determine their desired emergent behavior, e.g., movement, shape change or interaction with their surroundings. At the same time, reconfigurat...
Article
Effects of particle packing and size on the overall elastic properties of particulate random composites are analyzed. In order to account for the two effects the mean-field Morphologically Representative Pattern (MRP) approach is employed and an additional interphase surrounding inclusions (coating) is introduced. The analytical mean-field estimate...
Article
Full-text available
We propose a new class of modular-robotic structures, intended to produce forces which scale with the number of modules. We adopt the concept of a spherical catom and extend it by a new connection type which is relatively strong but static. We examine analytically and numerically the mechanical properties of two collective-actuator designs. The sim...
Conference Paper
Full-text available
Module localization is an important aspect of the operation of self-reconfigurable robots. The knowledge of spatial positions of modules, or at least of the overall shape which the modules form, is the usual prerequisite for reconfiguration planning. We present a general, decentralized algorithm for determining the positions of modules placed on a...
Conference Paper
Full-text available
We present a new human-structure interaction (HSI) model of walking on a flexible surface. A human is considered as a mass point, located at the body's center of mass (COM). The mass moves along a predefined trajectory, which deforms together with the surface on which the human walks. The forces of motion, equal to the sum of inertial and gravitati...
Article
The purpose of this work is the development of an efficient and high-sensitive damage localization technique for truss structures, based on the rank-revealing QR decomposition (RRQR) of the difference-of-flexibility matrix. The method is an enhancement of the existing techniques of damage detection, which rely on the set of so-called damage locatin...
Conference Paper
Full-text available
A collective actuator is a self-reconfigurable modular-robotic structure which produces useful mechanical work through simultaneous reconfiguration of its constituent units. An actuator is additionally called scalable if its force-to-weight ratio does not depend on the number of its member modules. In this work, we consider scalable collective actu...
Conference Paper
Full-text available
The term Programmable Matter (PM) describes the class of future meta-materials of programmable and controllable properties and behavior, e.g., able to autonomously transform into an arbitrary shape. The robotic approaches towards PM are based on the concept of cooperation of millions of micro-robots (modules), acting at a very fine length-scale and...
Technical Report
The report presents several approaches to model triethylene glycol dehydration process withe the use of high power microwave generator. Thermodynamic and lumped parameters models are proved through a set of simulations to be the most accurate.
Article
In the paper, we show how some basic informational quality measures (e.g. the Shannon entropy and the relative entropy/Kullback–Leibler divergence) defined for stochastic dynamical systems change in time and how they depend on the system properties and intensity of random disturbances. First, the Liouvillian systems (when randomness is present in t...
Article
A stochastic analysis of hydrogen-assisted fatigue crack growth in steel plates is presented. First, a simplified deterministic model of the process is proposed. It captures the basic empirical property that the influence of hydrogen diminishes, as the crack growth rate increases. However, it only applies to cases, when diffusion is rate limiting....
Chapter
The objective of this paper is to show how some basic informational quality measures (such as entropy and relative entropy / Kullback divergence) of stochastic dynamical systems depend on the system properties and characteristics of the external/internal randomness. First, the Shannon entropy flow in dynamic systems with random initial states is co...
Article
A method of predicting fatigue crack growth in hydrogen-charged thin steel plates is proposed. It consists in computing modified stress intensity factors which reflect the presence of hydrogen, and using them in a fatigue crack growth equation for an uncharged plate. The modification accounts for both, hydrogen embrittlement of crack tips and hydro...
Article
Full-text available
A method of optimization intended to speed up motions of non-redundant hydraulic manipulators along prescribed paths of their end-effectors is presented. A parametric path of the end-effector of a non-redundant manipulator determines the corresponding path in the mani-pulator joint-space. The optimization problem therefore reduces to fin-ding the o...
Article
Full-text available
The paper presents a control method, which makes a hydraulic arm robustly track a desired joint space path at high speed. Optimisation for speed is performed for the worst expected dynamic condition. The reference trajectory is given as a parametric function in a manipulator's joint space. Portions of the trajectory are online shrunk or stretched i...

Projects

Projects (3)
Project
The scientific objective of the project is to formulate and implement an analytical micromechanical model that accounts for the evolution of damage in predicting the macroscopic response of a composite material. The developed micromechanical model will consider: the volume fraction of the phases, the degree of packing of inclusions, their size and shape, and the quality of adhesion between phases. Two research hypotheses are put forward in the project: I. The influence of shape of the inclusions in the mean-field micromechanical models can be taken into consideration by numerical concentration tensors obtained by the semi-analytical method of numerical homogenization. In micromechanical approach, which uses an inclusion-matrix concept, the effect of the inhomogeneity shape is contained in the concentration tensor. In the literature the concentration tensors are available for the ellipsoidal shape. Numerical concentration tensors will expand the scope of shapes (e.g. cuboid, cylinder, flake, cross, "potato") that could be considered in the modeling. II. Predictions of a non-linear response of a heterogeneous material related to damage evolution can be improved in comparison to conventional micromechanical models by adopting the Morphology-based Representative Pattern approach (MRP). The morphological characteristics of the microstructure affect the mechanism of material failure, therefore accounting for their influence is crucial in modeling damage evolution. Preliminary studies of the developed MRP model for the elastic and elastic-plastic composite material proved enhanced predictive capabilities of the model (as compared to standard ones). The goal of the project is to extend the MRP approach to include description of progressive damage in the material. To this end the linearization procedure, developed for the elastic-plastic composites, will be applied in modeling of the damage evolution. The project is supported by the projects of the National Science Center (NCN) Poland, number 2017/25/N/ST8/01968 .
Archived project
The aim of the research is development of the reliable and computationally efficient methods of multiscale/micromechanical analysis suitable for estimation of a non-linear thermomechanical response of strongly heterogeneous materials in which additional substructure develops. Two types of heterogeneous media are considered: polycrystalline metals and alloys of high specific strength, in which heterogeneity is mainly the result of strong anisotropy of single crystals, and metal/intermetallic matrix composites, in which it results from high contrast in phase properties. The elastic-(visco)plastic deformations within the large strain regime and resulting microstructure evolution (texture, formation of dislocation-induced cell substructure or twinninginduced layered substructure, and resulting grain refinement) are investigated. The scale effects related to the characteristic dimensions of microstructure features and the influence of quality of the interfaces between phases on the overall material response is accounted for.
Archived project
The purpose of the project is to make progress in the modelling and control of programmable matter (PM) - a class of future meta-materials, composed of microscopic active modules. Through proper programming of the modules, objects made of PM could potentially change shape, vary their physical properties, or actively respond to environmental stimuli.