Staff

Abstract:
This paper introduces MorphoGen — an integrated reliability-based topology optimization and nonlinear finite element analysis system for 2D and 3D domains. The system’s key innovation is its seamless prototyping of scientific formulations for computational problems in topology optimization. Its layered and object-oriented architecture, based on the template method design pattern, facilitates effortless modifications of algorithms and the introduction of new types of finite elements, materials, and analyses. MorphoGen also offers flexible handling of objective functions and constraints during topological optimization, enhancing its adaptability. It empowers researchers and practitioners to explore a wide range of engineering challenges, fostering a deeper understanding of complex structural behaviors and efficient design solutions. There are many topology optimization software and open source codes, especially based on the classical SIMP method. Unlike these codes our package is freely distributed among users and since it is distributed on the MIT licence, which allows for its easy modification depending on the particular needs of the users. For this purpose, we use the topology optimization algorithm proposed for the first time in our previous paper (Blachowski et al., 2020). The algorithm is based on a fully stress design-based optimality criteria and can be applied for topology optimization of either linearly elastic and elastoplastic structures. Additionally, the novelty of the proposed system is related to its ability of solving optimal topology under various constraints such as displacement, stresses and fatigue in both deterministic and probabilistic cases. Another application are modular structures, which reduce design complexity and manufacturing costs as well as rapid reconfiguration. However, in the realm of structural optimization, modular systems are more challenging due to various: modes of operation of the modules and the stresses configurations. Moreover, this area of research is dramatically less explored. Thus the effectiveness of MorphoGen for structural engineering is demonstrated with examples of topological shape optimization of two Extremely Modular Systems: a planar robotic manipulator Arm-Z and spatial free-form ramp Truss-Z.

Keywords:
Stress Constrained Topology Optimizatio,Extremely Modular System,Object-oriented software architecture,MATLAB-based array programming,First Order Reliability Analysis

Abstract:
Arm-Z to koncepcja hiperredundantnego manipulatora robotycznego opartego na sekwencji szeregowo połączonych identycznych modułów. Każdy moduł ma tylko jeden stopień swobody (1-DOF) – skręt względem poprzedniego. Moduły systemu Arm-Z mogą być masowo produkowane i łatwo wymieniane w przypadku awarii. Sterowanie Arm-Z jest stosunkowo trudne, dlatego zwykle wymaga stosowania metod inteligencji obliczeniowej. W artykule przedstawiono kilka koncepcji kinetycznych obiektów małej architektury opartych na Arm-Z: spiralną kolumnę o regulowanej wysokości, system nadążania słonecznego, kinetyczną rzeźbę bioniczną i kinetyczny zraszacz/fontannę. Prezentowane koncepcje są zasadniczo nisko-technologiczne (“low-tech”). W każdym przypadku moduł bazowy jest przymocowany do podstawy (podłoża). Dla prostoty napęd jest przykładany bezpośrednio do pierwszego modułu, a następnie przenoszony za pomocą wewnętrznych przekładni na kolejne moduły. Każdy moduł jest wyposażony w zestaw cylindrycznych i stożkowych kół zębatych z zębami prostymi o profilu spiralnym (do połączeń miedzy modułami).

Keywords:
Arm-Z, hiperredundancja, manipulator, mała architektura, systemy modularne

Abstract:
Arm-Z to koncepcja hiperredundantnego manipulatora robotycznego składającego się z przystających modułów o jednym stopniu swobody (1-DOF) i realizującego (prawie) dowolne ruchy w przestrzeni. Zasadnicze zalety Arm-Z to: ekonomizacja (dzięki masowej produkcji identycznych elementów) oraz odporność na awarie (po pierwsze – zepsute moduły mogą być łatwo zastąpione, po drugie – nawet gdy jeden lub więcej modułów ulegnie awarii – manipulator taki może ciągle wykonywać, prawdopodobnie w stopniu ograniczonym, zakładane zadania). Podstawową wadą systemu Arm-Z jest jego nieintuicyjne, bardzo trudne sterowanie. Innymi słowy, połączenie koncepcji nietrywialnego modułu z formowaniem praktycznych konstrukcji oraz sterowanie ich rekonfiguracją (transformacją ze stanu A do B) są bardzo złożone obliczeniowo. Mimo to prezentowane podejście jest racjonalne, zważywszy powszechną dostępność wielkich mocy obliczeniowych w kontraście z wysokimi kosztami i „delikatnością” niestandardowych rozwiązań i urządzeń. W artykule nakreślono ogólną koncepcję manipulatora Arm-Z i zaprezentowano wstępne prace zmierzające do wykonania prototypu.

Keywords:
Arm-Z, odporność na awarie, sterowanie kształtem ogólnym, systemy modularne

Abstract:
Arm-Z is a concept of a hyper-redundant manipulator based on linearly joined sequence of congruent modules by oblique swivel joint mechanism. Each module has one degree of freedom only, namely a twist relative to the previous module in the sequence. Although the concept of this type of manipulator is relatively old and simple, its control is very difficult an nonintuitive, which results in a limited use in industrial practice. This paper presents a simple simulation of Arm-Z in Mathematica programming environment which demonstrates a few simple but potentially useful movements.

Keywords:
Arm-Z, Extremely Modular System, hyper-redundant manipulator, Mathematica, oblique swivel joint

Abstract:
This paper presents a concept of an extremely simple planar manipulator composed of 24 congruent modules. Each module has only two possible discrete positions in relation to the previous module: left (− π 6 ) or right ( π 6 ). However, despite its conceptual simplicity, this manipulator can perform relatively demanding tasks, for example as an inspection device. The manipulator is placed in an experimental environment, and the goal is to place its tip in close proximity to five given points without collisions. Despite the constraints of its motion, the manipulator effectively “crawls” inside the working space and visits assigned points. The control of the manipulator is executed by manual placing to desired configurations and interpolating the intermediate transitions. The preliminary results are promising and show that for certain practical types of tasks, the functionality and precision of this extremely simple manipulator could be sufficient, e.g., visual inspection, provision of survival supplies, placing of explosives, etc.

Keywords:
discrete manipulator,hyper-redundant,snake robot,modular

Abstract:
Arm-Z is a hyper-redundant manipulator based on a sequence of linearly joined identical modules. Each module has only one degree of freedom—a twist relative to the previous module. Arm-Z can be potentially economical, as the modules can be mass-produced. Arm-Z is also robust, as the malfunctioning module can be replaced. Moreover, if some modules malfunction, the device can still execute tasks with certain accuracy. However, the disadvantage of Arm-Z is a non-intuitive and difficult control. This paper presents a concept of a modular tracking device comprised of four identical modules. As an example, the Sun-tracking setup is used with possible application for solar energy harvesting.

Keywords:
Extremely modular system, Arm-Z, Hyper-redundant manipulator, Sun-tracking

Abstract:
Arm-Z - a hyper-redundant manipulator based on linearly joined sequence of congruent units is presented. Each unit has 1-DOF (one degree of freedom) only, namely a twist relative to the previous unit in the sequence. Arm-Z has a potential of being economical and robust. The control of Arm-Z, however, is not intuitive and difficult. This paper presents the preliminary results of designing a prototype of a modular Sun-tracking device comprised of four congruent units with possible application as a solar energy harvester or a Sun-shade.

Keywords:
Extremely modular system, Arm-Z, Hyper-redundant manipulator, Rapid prototyping, Low-tech

Abstract:
Arm-Z is a concept of a hyper-redundant manipulator based on linearly joined sequence of congruent units. Each unit has only one degree of freedom (1-DOF), namely a twist relative to the previous unit in the sequence. Since each module is identical, Arm-Z has a potential of being economical and robust: the modules can be mass-produced and, in case of failure, easily replaced. However, the control of Arm-Z is nonintuitive and difficult, thus it usually requires application of computational intelligence methods. This paper presents a number of concepts for kinetic street furniture based on Arm-Z: a spiral column of adjustable height, a sun-tracking shade/solar energy harvester, bio-mimicry sculpture, kinetic sprinkler/fountain. The proposed concepts are low-tech in principle. Therefore in each case, the first module in the sequence is fastened to a solid base (ground). For simplicity, the drive is applied directly to the first module and transferred to subsequent units by internal gears. Each module is equipped with a set of cylindrical and bevel gears with straight teeth with involute profile (for connecting the modules).

Keywords:
Arm-Z, extremely modular system, low-tech, street furniture

Abstract:
Arm-Z is a concept of a robotic manipulator comprised of linearly joined congruent modules with possibility of relative twist. The advantages of Arm-Z are: economization (mass-production) and robustness (modules which failed can be replaced, also if some fail the system can perform certain tasks). Non-intuitive and difficult control are the disadvantages of Arm-Z. It has been introduced over six years ago. The theretofore research focused on the control of the virtual Arm-Z manipulator through the relative twists of its constituent units. This paper documents the fabrication and testing of the preliminary physical prototype of a simple Arm-Z, which has been built using relatively low-tech approach. The modules have been assembled from 3D-printed elements using PET-G filament. Each module is equipped with a transmission mechanism allowing to pre-set the spin of its twist (either positive/right or negative/left). Although the presented system is very simple it demonstrates certain meaningful kinematic actions and sets clear paths for the future research in the area of Extremely Modular Systems.

Keywords:
extremely modular system, arm-Z, hyper-redundant manipulator, rapid prototyping, low-tech

Abstract:
This contribution considers the problem of topology optimization of modular structures. A bionic trunk-like robotic “Arm-Z” manipulator is considered. The manipulator is modular, that is, it is composed of a sequence of identical modules. In geometric terms, each module is essentially an obliquely cut section of an elliptical pipe, so in the cutting plane it forms a circle. With respect to the previous module, it has a single degree of freedom: the relative twist. Therefore, the total number of the degrees of freedom of the entire manipulator equals the number of its modules. Such a manipulator belongs to the family of Extremely Modular Systems. The advantages of such systems are the economization (due to the possible mass production of modules) and robustness (replacement of a failed module instead of a complex repair).

Keywords:
Topology optimization, Modular manipulator, Multiple loadings, Geometric transformations, Kinematics, Stress constraints.

Abstract:
We show that the Soft Actor-Critic Reinforced Learning algorithm is able to find efficient motion patterns for a hyper-redundant robot consisting of 6 identical modules connected in a chain like fashion. The control is done by applying relative angular velocities between the modules. Analogous system has been studied before in the context of a robotic trunk-like manipulator.

Keywords:
Reinforced Learning, Robotic Locomotion, Hyperreduntant Modular Manipulator, Arm-Z, Extremely Modular System

Abstract:
This contribution concerns a snake-like robotic manipulator arm proposed first in [1]. The manipulator is composed of linearly but nonaxially joined identical modules with a possibility of relative twist, which amounts to one degree of freedom per module. It is an example of an extremely modular system [2], and its advantages are: economization (due to modularity and possible mass production) and robustness (easy repair by replacement of a failed module). The hitherto research involved the possible geometric transformations of the manipulator arm [3], but not its structural optimization. However, structural design of the involved modules is a challenging task, as the process has to take into account the relative position of the module along the arm, as well as the variety of global configurations of the deployed manipulator. It leads to a multi-load structural optimization problem with a significantly large number of loads. This contribution considers topology optimization of such a modular manipulator structure. Due to the large variety of possible load conditions, the initial analysis involves a 2D model of the structure with a discrete set of two possible relative arrangements of adjacent modules. Such a formulation allows the proposed approach to be preliminarily explored, tested and optimized in a numerically manageable simplified environment. The support of the National Science Centre, Poland, granted under the grant agreement 2019/33/B/ST8/02791 is gratefully acknowledged.