Geometrical Synthesis Research Articles

Metaheuristic Approach to Synthesis of Suspension System of Mobile Robot for Mining Infrastructure Inspection.

The article describes the problem of geometric synthesis of the inspection robot suspension system, designed for operation in difficult conditions with the presence of scattered obstacles. The exemplary application of a mine infrastructure inspection robot is developed and supported by the ideas. The brief introduction presents current trends, requirements and known design approaches of platforms enabled to cross the obstacles. The idea of a nature-inspired wheel-legged robot is given, and the general outline of its characteristics is provided. Then the general idea of kinematic system elements selection is discussed. The main subject of geometrical synthesis of the chosen four-bar mechanism is described in detail. The mathematical model of the suspension and connections between the parts of the structure is clarified. The well-known analytical approach of brute force search is analyzed and validated. Then the method inspired by the branch and bound algorithm is developed. Finally, a novel application of the nature-inspired algorithm (the Chameleon Swarm Algorithm) to synthesis is proposed. The obtained results are analyzed, and a brief comparison of methods is given. The successful implementation of the algorithm is presented. The obtained results are effectively tested with simulations and experimental tests. The designed structure developed with the CSA is assembled and attached to the prototype of a 14-DOF wheel-legged robot. Furthermore, the principles of walking and the elements forming the control structure were also discussed. The paper is summarized with the description of the developed wheel-legged robot LegVan 1v2.

Simulation of a cylindrical-conical gear train on parallel axes with an adjustable side clearance

The geometrical synthesis of a cylindrical-conical transmission on parallel axes with external gearing is considered on the basis of the blocking contour method, which makes it possible to determine solutions for the right and left ends of the wheel. The use of the calcula-tion for cylindrical-conical wheels is described. We used our own algorithm for constructing the blocking contour and engagement in the Math CAD program, and a 3D model of the trans-mission in the KISSsoft program. For a better example, the contour and engagement in the 3D model are given.

Geometric synthesis of the folding bridge mechanism

In London there is a folding bridge composed of eight platforms articulated between them. One platform is fixed to base (a platform from one end). The platforms have the shape of isosceles trapezoid. When the bridge is folded the large bases of the trapezoids form an octagon. The driving mechanism of the bridge is composed by motor dyads (active RRTaR groups) and RRR dyads. For the eight platform bridge the maximum piston stroke is less than the platform height (trapeze height). In this case, the connections between the hydraulic cylinders and the other elements are usually made, i.e. at the ends of the cylinder. If we want to make a folding bridge with fewer moving platforms, there are situations when the piston stroke is greater than the height of the trapeze. In this case must be performed the geometrical synthesis of the mechanism such that the folded bridge forms desired geometric figures (square, pentagon etc.).

Geometrical synthesis method and parametric optimization of galloping robot leg mechanism

Subject of Research. The paper presents geometrical synthesis results of kinematic schemes for a femur and a whole leg mechanisms of a cheetah robot, which is able to jump in place and run at various speed. We substantiate the topology of mechanisms, describe their operation principles, characteristics and distinctive features, involving the controlled reconfiguration of mechanisms for changing the trajectory of the ground-contact point, and the use of flexible elements and links with variable length to ensure energy-efficient locomotion. Method. A structure scheme of the whole cheetah robot leg was obtained by attaching four movable links to the femur mechanism, imitating large and small tibial bones, metatarsus and sartorius muscle. The obtained structure was decomposed into three mechanism components: a “minitaur”, two-rocker four-bar lambda mechanism and a rocker-slider mechanism. The kinematic schemes of the above-mentioned mechanisms were synthesized by the method of extreme discrete positions with the result that the kinematic scheme of the whole leg with intermediate positions was obtained. The parametric optimization algorithm was described and the minitaur objective function was given using mathematical programming. Main Results. The kinematic scheme of the whole cheetah robot leg is obtained in the first approximation without taking into account the robot dynamics, location of flexible elements and their resonance necessary for the resonance behavior in order to achieve energy-efficient movement. Modeling results of the robot dynamics according to the synthesized scheme are given. Stable behavior is obtained both while jumping in place and running. Practical Relevance. The study is carried out for the development of an energy-efficient four-legged galloping cheetah robot performing energy recovery with the help of flexible elements. The synthesized kinematic scheme is applicable for detailed analyzes of dynamics, kinetostatics, energy recovery and losses upon impact with the ground surface, and for the robot prototype design.

Geometrical synthesis of four-bar gear train with related gears

The method of optimal geometric synthesis of four-bar cylindrical gear with related gears with one external and one internal gearing is proposed. The method is based on a new calculation system that increases the number of synthesis output parameters to six, which makes it possible to considerably expand the domain of existence of the synthesis problem solution with the simultaneous synthesis of two gearing. The software implementing the proposed technique is described. To solve the problem of nonlinear mathematical programming the library of Optimization Toolbox functions included in Matlab is used. Examples of calculations are given.

Geometrical synthesis of spatial six-link guiding mechanisms

The study considers problems of geometric synthesis of spatial hinge-lever six-link mechanisms with linear displacement of the final link performing the guiding function. The variants of arranging the mechanisms and their design features to provide the maximum course of the final link with minimum lengths of levers have been found. The geometric parameters of the mechanism in its generalized form have been determined and specified the kinematics and layout schemes. The influence of geometric parameters and layout variants on the kinematic parameters of the mechanisms has been studied. Dependencies have been obtained to determine the geometric parameters of the basic mechanism by the specified course of the final link and the permissible angles of transmission in the hinges of the levers. Parametric dependencies are provided in the article to help calculate accurately the optimal geometry of the mechanism by the criterion for minimizing the lengths of the levers at acceptable transmission angles and the required range of displacements. A scheme has been proposed for calculating spatial dimensional chains for determining the shape of the parts. 3D modeling has revealed the variability of geometric parameters, which helped formulate layout versions of the mechanism. A technique for geometric synthesis has been developed and variants of spatial hinge-lever six-link mechanisms in dynamics have been modeled in accordance with this technique, which made it possible to show the features of the motion of the links. The carried out research has determined possible ways of developing new variants of spatial hinge-lever six-link mechanisms, and it has opened new possibilities of their application as a guiding mechanism. The results of the research can be used in designing platforms for lifts, robot manipulators, machine tools, and in mechatronics

Mechatronic System for Locomotion Rehabilitation

The purpose of this study is to develop computational mathematical models for virtual prototyping of an actuation system from an exoskeleton human knee joint. These models are a part of the virtual and experimental prototype of a mechatronic system for locomotion rehabilitation in case of disabled persons. Experimental tests were performed on a group of persons without locomotion deficiencies. The obtained database was used to develop geometrical kinematic synthesis of the exoskeleton actuation mechanisms for knee’s joint and also ankle.

Cam Mechanism Design for a Human Leg Exoskeleton

The purpose of this study is to design and correlate, from theoretical aspects, a mathematical model for virtual prototyping of an actuation system from an exoskeleton human ankle joint. This model is a part of the virtual and experimental prototype from a mechatronic system for locomotion rehabilitation in case of disabled persons. Experimental tests were performed on a group of persons without locomotion deficiencies in order to obtain the pattern curve for cam mechanism design and also to validate the proposed prototype. The obtained database was also used to develop geometrical kinematic synthesis of the exoskeleton actuation mechanisms for other joints such as hip and knee.

Geometrical Synthesis of the Planetary Rotor Hydrocar Containing the Round and Non-Round Central Gearwheels

Объемные гидромашины - насосы и двигатели - широко используются в самых разных технических системах. Одним из видов таких машин являются планетарные роторные гидромашины (ПРГМ). ПРГМ содержат два центральных зубчатых колеса (как правило, некруглых) и расположенные между ними плавающие сателлиты. При этом числа волн M и N центральных колес могут быть как различными, так и одинаковыми. При проектировании и расчете ПРГМ основной задачей является геометрический расчет их зубчатых звеньев. Ранее такая задача была решена для случая, когда оба центральных колеса некруглые, а центровые траектории сателлита изменяются по простейшему закону «косинуса». В данной статье предлагается методика синтеза центроид звеньев ПРГМ, содержащих круглое и некруглое центральные колеса. При этом необходимо обеспечить совместимость волнообразной центроиды эпициклического колеса с заранее заданной центроидой круглого солнечного колеса (или наоборот). Разработанный метод геометрического синтеза ПРГМ позволяет получить профили зубчатых звеньев ПРГМ с помощью стандартных программных комплексов. Метод будет востребован на этапе проектирования планетарных роторных гидромашин (насосов и гидродвигателей) конструкторами предприятий машиностроительной отрасли.

KINEMATICS OF THE V MECHANISM USED FORELECTRIC SWITCHERS BASED ON SPECIALISED SOFTWARE

This paper is representing a continuing research of the doctoral thesis "Geometrical analysis and synthesis of mechanisms in the electrotechnical field". Using two Mathcad programs as mathematics analysis software and Solidworks as graphical analysis software it is dimensioned the new kinematics scheme of the high voltage V mechanism. Kinematic analysis is based on the mathematical model presented in the doctoral thesis mentioned above and graphical modeling and analysis is conducted to compare and complete the research regarding the V mechanism triadic chain 5R + T type.

Synthesis of a Watt II six-bar linkage in the design of a hand rehabilitation robot

As a result of neurological disorders such as stroke, brain and spinal cord injuries, disability in body regions might occur. In case of similar situations, rapid therapeutic training in early stages has chance to prevent permanent disability by retraining motor movements. In regular treatments, therapists help to carry out regular exercises to train motor movements of the disabled region. However, continuous increase in cases, tough working conditions, dependability on expertise and human body limitations make the procedures cumbersome and ineffective. Incorporating robots into therapeutic training not only allows executing treatments in a delicate repeatability but also opens new possibilities in terms of exercise types and speeds. In the light of recent developments in robotic rehabilitation this paper presents the design of a hand rehabilitation robot for human four fingers that solely targets hand disabilities by utilizing real grasping motion data of the forefinger into kinematic synthesis of Watt II six-bar linkage. During the design geometrical synthesis was used for the first loop in order to attain continuous input rotation and the body-guidance synthesis was used for the second loop for the end effector to follow the desired trajectory in desired orientations.

KINEMATICS OF THE V MECHANISM USED FORELECTRIC SWITCHERS BASED ON SPECIALISED SOFTWARE

This paper is representing a continuing research of the doctoral thesis "Geometrical analysis and synthesis of mechanisms in the electrotechnical field". Using two Mathcad programs as mathematics analysis software and Solidworks as graphical analysis software it is dimensioned the new kinematics scheme of the high voltage V mechanism. Kinematic analysis is based on the mathematical model presented in the doctoral thesis mentioned above and graphical modeling and analysis is conducted to compare and complete the research regarding the V mechanism triadic chain 5R + T type.

Geometrical Synthesis of the Distribution Mechanisms

In this study the author presents shortly some few original trigonometric methods to make the synthesis of some main distribution mechanisms. One presents four main modules of distribution mechanisms, with rotary cam and translated or rotated tappet plane or with roll, used with priority at the distribution mechanisms from the heat engines with internal combustion. These types of distribution mechanisms can improve the changes of gases and may decrease significantly the level of vibration, noises and emissions. As long as we produce electricity and heat by burning fossil fuels is pointless to try to replace all thermal engines with electric motors, as loss of energy and pollution will be even larger. However, it is well to continuously improve the thermal engines, to reduce thus fuel consumption. At the heat engine with internal combustion a great loss of power is realized and by the distribution mechanism, reason for that we must try to improve the functionality of this mechanism. The synthesis of these types of distribution mechanisms can be made shortly by the Cartesian coordinates, but to determine these coordinates we need and some trigonometric parameters of the mechanisms.

Low Speed Linear Actuator for Accurate Orientation of Concentrated Solar Convertors

The accurate orientation of concentrated solar converters (e.g. solar parabolic dish, concentrated photovoltaic) requires small stepwise angular displacements at short intervals of time aiming to track accurately the sun. These tracking systems are usually operated, especially the elevation movement, by low speed linear actuators (LSLA) with special configuration. The main drawbacks of the known LSLA solutions refers to the high constructive complexity of the intermediate gear reducer and its relative low efficiency due to the high value of the kinematic ratio, required to harmonize high speed motors and low speed outputs. The paper presents a geometrical synthesis algorithm and kinematic simulations of a new LSLA variant, proposed by the authors, consisting of a classical electrical motor (AC or DC), a linkage reducer transmitting intermittently the motion to a final irreversible screw-nut transmission through backstopping clutches. Compared to the known solutions, the proposed actuator has the advantage of decreasing the structural, constructive and technological complexity of the intermediate gear reducer (between the motor and the irreversible screw-nut transmission) by replacing it with a linkage type speed reducer and backstopping clutches, achieving a fixed or adjustable high kinematic ratio.

Geodynamics of oroclinal bending: Insights from the Mediterranean

The Alpine Orogen in the Mediterranean region exhibits a series of orogenic curvatures (oroclines). The evolution of these oroclines is relatively well constrained by a plethora of geophysical and geological data, and therefore, their origin can inform us on the fundamental processes controlling oroclinal bending. Here, a synthesis of the geometry of Mediterranean oroclines, followed by a discussion on their geodynamic origin is presented. The geometrical synthesis is based on a new classification of Mediterranean oroclines, which defines a first-order orocline (Adriatic Orocline) by the general northward-convex shape of the Alpine Orogen from Cyprus to Gibraltar. Superimposed on the limbs of this orocline, are second-, third- and fourth-order oroclines. The major process that led to the formation of the Adriatic Orocline is the indentation of Adria into Europe, whereas second- and third-order oroclines (e.g., Western Mediterranean and Gibraltar oroclines, respectively) were primarily controlled by a combination of trench retreat and slab tearing. It appears, therefore, that the geodynamics of Mediterranean oroclines has been entirely dependent on plate boundary migration and segmentation, as expressed in the interlinked processes of indentation, trench retreat and slab tearing. The relative contribution of specific geodynamic processes, and their maturity, could be inferred from geometrical characteristics, such as the amplitude-to-width ratio, the orientation of the curvature (convex or concave) relative to the convergence vector, and their geometrical relationship with backarc extensional basins (e.g., in the concave side of the orocline). Based on the information from the Mediterranean oroclines, it is concluded that oroclinal bending commonly involves lithospheric-scale processes, and is not restricted to thin-skinned deformation. However, contrary to previous suggestions that assume that the whole lithosphere can buckle, there is no clear evidence that such processes occur in modern tectonic environments.

Mantis: hybrid leg-wheel ground mobile robot

Purpose – The aim of the research is the development of a small-scale ground mobile robot for surveillance and inspection; the main design goals are mobility in indoor environments with step climbing ability, pivoting around a vertical axis and without oscillations for stable vision, mobility in unstructured environments, low mechanical and control complexity. Design/methodology/approach – The proposed hybrid leg-wheel robot is characterized by a main body equipped with two actuated wheels and two praying Mantis rotating legs; a rear frame with two idle wheels is connected to the main body by a vertical revolute joint for steering; a second revolute joint allows the rear axle to roll. The geometrical synthesis of the robot has been performed using a nondimensional approach for generality's sake. Findings – The experimental campaign on the first prototype confirms the fulfilment of the design objectives; the robot can efficiently walk in unstructured environments realizing a mixed wheeled-legged locomotion. Practical implications – Thanks to the operative flexibility of Mantis in indoor and outdoor environments, the range of potential applications is wide: surveillance, inspection, monitoring of dangerous locations, intervention in case of terroristic attacks, military tasks. Originality/value – Different from other robots of similar size, Mantis combines high speed and energetic efficiency, stable vision, capability of climbing over high steps, obstacles and unevenness.

Spherical Planetary Ball Transmissions: Geometrical Synthesis

The paper examines theoretical problems of the development of transmissions with intermediate engaged rolling bodies in which speed reduction and load transfer are made through interaction of main gear units with balls. The distinctive feature of this type of gears is the execution of working surfaces (running ways) of the main gear units on the spherical surfaces. The design of spherical transmission with the constant reduction ratio is developed. The principle of its work is based on interaction of rolling bodies with running way of drive shaft, working surfaces of stopped gear unit and meridional grooves of driven shaft. The running way and working surfaces are made along the harmonic curves closed on sphere. The parametrical equations of interacting spherical curves of several types are received. One of these curves is an inclined circle along which a ring groove on sphere is made. Theoretical principles are illustrated by examples of design of reducer unit.

EM signal integrity via neural network analysis for the RFX-mod experiment

The RFX-mod electromagnetic measurement system is constituted of 744 independent probes whose signals are electronically conditioned by an integration/amplification section. During experimental sessions the probes integrity is controlled by a series of post-shot softwares which determine if a probe is still working or not and correct off-sets and drifts, but no method, apart from the visual inspection of a signal, is available to recognize if the corresponding channel in the integration/amplification section is about to break. In order to overcome this lack a neural network approach has been applied. The neural network implemented here is built performing a geometrical synthesis of a supervised Multi Layer Perceptron, then the trained net is used to predict a possible failure of the corresponding channel in the integration/amplification section. To perform the prediction the neural network is used as a non linear regressor, the synaptic weights of the trained net can be considered as a neural transform of the system, the variation of those weights in the test phase is symptom that the channel is not working properly. The procedure has been tested on a subset of electromagnetic signals and in this paper the results are presented.

Artificial Anisotropy in Circular Photonic Crystals and Applications

In this paper, we analyze the birefringence effect in circular photonic crystals (CphCs). The studied CphCs are dielectric rings (DRs) and photonic crystals with cylindrical air holes arranged in circular patterns. The dielectric concentric circular patterns admit two preferred propagation directions defined by an extraordinary and an ordinary refractive index, representing two electric field polarizations. These electric fields are diffracted inside the crystal or are localized in a central microcavity region. We prove the induced artificial anisotropy in DRs through the geometrical equivalence with the corresponding thin-film multilayer structure. The equivalence is obtained through the geometrical synthesis of the wavefront propagation inside the artificial anisotropic structure. As applications, we analyze a Si/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> DR Bragg reflector and a GaAs CphC microcavity resonator. The Bragg theory is validated by numerical time-domain approaches that are well suited to solve scattering problems. The microcavity resonance analysis and the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> -factor evaluation are performed by the finite-element method modeling.

Topological and Geometrical Synthesis of Three-Degree-of-Freedom Fully Parallel Manipulators by Instantaneous Kinematics

This paper presents a new synthesis procedure of fully parallel manipulators (PMs) of three degrees of freedom (DOFs) that could be implemented in a computer-aided synthesis process. Possible designs of PMs are represented by a set of unit joint twists at an initial configuration, called here topological and geometric parameters (TGPs). This makes it possible to represent PMs of all topologies and geometries in an easy and consistent way. The kinematic bond between the end effector (EE) and the base is then formulated as a set of equations involving TGPs, actuated-joint variables, and non-actuated-joint variables (passive joints). To achieve the required type of EE motion, possible topologies are first derived from tangent space analysis, and then the feasible topologies are retained by further displacement analysis. The geometries are determined such that the set of equations should be isoconstrained when passive-joint variables are taken as unknowns. The synthesis procedure of 3DOF PMs is illustrated with three numerical examples: one producing a new architecture of one translation and two rotations, while the other two producing existing architectures of translational PMs.