Issue 4

JTAM, Sofia, vol. 47 Issue 4 (2017)

Finding the Optimal Parameters for Robotic Manipulator Applications of the Bounded Error Algorithm for Iterative Learning Control

Kaloyan Yovchev
Faculty of Mathematics and Informatics, Sofia University, Sofia, Bulgaria

This paper continues previous research of the Bounded Error Algorithm (BEA) for Iterative Learning Control (ILC) and its application into the control of robotic manipulators. It focuses on investigation of the influence of the parameters of BEA over the convergence rate of the ILC process. This is performed first through a computer simulation. This simulation suggests optimal values for the parameters. Afterwards, the estimated results are validated on a physical robotic manipulator arm. Also, this is one of the first reports of applying BEA into robots control.

JTAM, Sofia, vol. 47 Issue 4 pp. 03-11 (2017), [Full Article]

Development of Hand-Held Surgical Robot ODRO-2 for Automatic Bone Drilling

George Boiadjiev1,2, Ivan Chavdarov3, Kamen Delchev2, Tony Boiadjiev4, Rumen Kastelov5, Kazimir Zagurki3
1Faculty of Mathematics and Informatics, Sofia University, 5 J. Boucher Blvd, 1164 Sofia, Bulgaria
2Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bl. 4, 1113 Sofia, Bulgaria
3Institute of System Engineering and Robotics, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bl. 2, 1113 Sofia, Bulgaria
4Institute of Information and Communication Technologies, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bl. 2, 1113 Sofia, Bulgaria
5Orthopaedic and Trauma Clinical Centre of Ministry of Interior, 79 Skobelev Blvd, 1606 Sofia, Bulgaria

This paper represents the development of a prototype robotic system for automatic bone drilling in orthopaedic surgery. A new design of the mechanical structure is proposed, answering the surgical requirements for the robot dimensions and weight to be as small as possible. The new structure design is based on idea of parallelism of the axis of the linear actuator and the axis of the rotary one. The control system is improved by using a new microcontroller. A new type of linear drive and a new force sensor (load cell) are built in, so that the quality characteristics of the “Orthopaedic bone Drilling Robot” (ODRO) are not only the same as previous its two versions, but becomes better. An experimental setup is arranged and experiments are executed to test and to verify the robot quality features and functional capabilities.

JTAM, Sofia, vol. 47 Issue 4 pp. 12-22 (2017), [Full Article]

Experimental Research of Rotational-And-Frictional Boring of Big Holes in Large Parts

K. T. Sherov1, M. R. Sikhimbayev2, B. S. Donenbayev1, A. A. Sagitov1, S. S. Ainabekova1
1Karaganda State Technical University, B. Mira str. 56, 100027, Karaganda, Kazakhstan
2Karaganda Economic University, Akademicheskaya str., 9, 100009, Karaganda, Kazakhstan

When producing large-dimensional parts of heavy machines, the largest specific weight in the general labour input is made by the operations, connected with machining the main holes, i. e. holes of large diameter. To the holes of large diameter of large-dimensional parts, there are specified high requirements in the aspect of accuracy of the size, shape and arrangement. Machining of holes still remains one of the topical problems of present day mechanical engineering, in particular machine-building enterprises of the Republic of Kazakhstan. Solving the problem of ensuring accuracy and quality of machining large holes of large-dimensional parts requires the development of new resource-saving technologies of machining. In this work there are presented the results of studying a resource-saving method of rotation-friction boring of large diameter holes. There has been achieved good results in providing the quality indicators, when machining by the proposed method of rotation-friction boring with the use of the tool (a disk cutter) made of steel 90CrSi5 in comparison with well-known boring of holes. The diagram of chip formation of cutting and the results of studying the zone of chip formation by the metallographic method is also presented.

JTAM, Sofia, vol. 47 Issue 4 pp. 23-36 (2017), [Full Article]

Calculation of Stress-Deformed Condition in Polymer Nanocomposites Filled with Microcapsules with Lubricant

I. V. Kolesnikov1, V. V. Bardushkin2, Ph. V. Myasnikov1
1Rostov State Transport University, Rostov-on-Don, Russia
2National Research University of Electronic Technology, Moscow, Russia

The article suggests the technology of modifying a polymer matrix by microencapsulation, i. e. the introduction of microparticles (lubricants with nano-additives in polymer shells) into nanocomposites matrix, to form multilevel structures on the tribounit surface. Besides, it suggests the method of predicting the operational elastic properties of multicomponent matrix composites with microcapsules, filled with a liquid substance. The method is based on the generalized singular approximation of the theory of random fields and allows, taking into account the geometric dimensions of the inclusions in the shell. It contains the results of numerical modelling of the effective elastic characteristics (Young’s modulus and Poisson’s ratio) of composites, based on phenylone with dispersed inclusions (microcapsules), which are glycerin-filled spherical shells of the kapton. The paper investigates the effect of the geometric dimensions of microcapsules and the volumetric content of components on the operational elastic properties of tribocomposites. The developed antifriction nanomaterials with microcapsules are able to create an oriented lubricating coating on the friction surfaces, apply lubrication to a certain friction area and carry out the lubrication portion wise precisely in the necessary contact zone of the bodies.

JTAM, Sofia, vol. 47 Issue 4 pp. 37-47 (2017), [Full Article]

Torsional Wave Propagation in a Pre-Stressed Structure with Corrugated and Loosely Bonded Surfaces

Manoj K. Singh, Sanjeev A. Sahu
Indian Institute of Technology (Indian School of Mines), Dhanbad-826004, Jharkhand, India

An analytical model is presented to study the behaviour of propagation of torsional surface waves in initially stressed porous layer, sandwiched between an orthotropic half-space with initial stress and pre-stressed inhomogeneous anisotropic half-space. The boundary surfaces of the layer and halfspaces are taken as corrugated, as well as loosely bonded. The heterogeneity of the lower half-space is due to trigonometric variation in elastic parameters of the pre-stressed inhomogeneous anisotropic medium. Expression for dispersion relation has been obtained in closed form for the present analytical model to observe the effect of undulation parameter, flatness parameter and porosity on the propagation of torsional surface waves. The obtained dispersion relation is found to be in well agreement with classical Love wave equation for a particular case. The cases of ideally smooth interface and welded interface have also been analysed. Numerical example and graphical illustrations are made to demonstrate notable effect of initial stress, wave number, heterogeneity parameter and initial stress on the phase velocity of torsional surface waves.

JTAM, Sofia, vol. 47 Issue 4 pp. 48-74 (2017), [Full Article]

Novel Dynamic Model Updating Technique for Damped Mechanical System

Shankar Sehgal, Harmesh Kumar
Department of Mechanical Engineering UIET, Panjab University, Chandigarh, 160 014, India

Response surface method and Derringer’s function approach have been combined together to develop novel structural dynamic model updating technique for a damped mechanical system. Response surface models have been incorporated instead of finite element models, in order to increase computational efficiency of proposed technique. Derringer’s function approach is useful in dealing successfully with multi-objective optimization type model updating problems. Few such undamped techniques have been recently developed for undamped mechanical systems by combining the benefits of response models with Derringer’s function approach. This paper presents the theory and numerical application of a damped updating technique, which is based upon response models and Derringer’s function approach. In this technique, updating process is formulated as an optimization problem, wherein desirability functions are formulated, based on natural frequencies, modal-assurance-criterion values, resonance and anti-resonance points of frequency response functions. Desirability functions are then optimized to evaluate updated elastic parameters in stage one and updated damping constants in stage two of proposed technique. By using this technique, total absolute errors in natural frequencies, modal-assurance-criterion values, elastic parameters and frequency response functions have been reduced to 0.02%, 0.00%, 3.69% and 0.11%, respectively.

JTAM, Sofia, vol. 47 Issue 4 pp. 75-85 (2017), [Full Article]

Prof. DSc Angel I. Baltov, Corresponding Member of the Bulgarian Academy of Sciences, and His Contributions to Solid Mechanics

Ana Yanakieva, Robert Kazandjiev
Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bl. 4, 1113 Sofia, Bulgaria

We are honoured herein to present the long and remarkable scientific career of Prof. Angel I. Baltov, a renowned researcher in the field of Solid Mechanics at the Institute of Mechanics, BAS. The short CV enclosed proceeds with an interview, where our colleague discloses the essential steps of his career.

JTAM, Sofia, vol. 47 Issue 4 pp. 86-92 (2017), [Full Article]

Academician Yatshko Ivanov One of the Doyens of the Bulgarian Science (Academician Yatshko Ivanov at 85 years old)

Dessislava Kostadinova, Vasil Kavardjikov
Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bl. 4, 1113 Sofia, Bulgaria

Living 85 years is a real challenge! Especially in the tense life we are leading today. What is this vitality of the scientist due to? If you ask him, he cannot give you a single answer. Surely he will say - Gen...

JTAM, Sofia, vol. 47 Issue 4 pp. 93-94 (2017), [Full Article]


the Seventy Fifth Anniversary of Prof. DSc Stefan Petrov Radev
the Eighty Fifth Anniversary of Prof. DSc Zaprian Dimitrov Zaprianov

JTAM, Sofia, vol. 47 Issue 4 pp. 95-95 (2017), [Full Article]