Lubomir Dimitrov

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• PhD
• Professor at Technical University of Sofia

For reliable autonomous train operation, detecting and classifying obstacles on or near rail tracks, and accurately estimating the distance to these obstacles, is essential. This task is more challenging in low-light conditions, common for freight trains that operate primarily at night. This paper proposes a novel method, FuzzyH, for estimating the...

Abstract. The positive emotional impact of a product on the consumers raises their desire to own it. An approach for user experience design of cheese packages is presented. It includes a questionnaire for measuring user experience. By a partial least squares regression model optimal values of package design elements providing most positive emotiona...

This study explores the dynamic behavior and vibration stability of a complex moving mechanical oscillator coupled with a three-part viscoelastically connected continuous beam-foundation system. Elastic waves generated by the oscillator can destabilize the system, a scenario common in high-speed trains and vehicles. The paper presents an improved a...

This article covers a comprehensive study in the field of website traffic prediction where machine learning is used. It also additionally focuses on a specialized neural network structure utilizing LSTM layers and an attention layer, explicitly crafted for the processing of time series data. The paper extensively discusses LSTM layers and their abi...

In the dynamic times of paradigm shift, which are characterized by rapid technological progress as well as the digitalization of the world, the future-oriented and technology-savvy manufacturing companies strive to optimally integrate IT applications into the success of the company. Enterprise Resource Planning (ERP) consolidates all business areas...

The load distribution in bevel gears depends on many factors, one of which is the deformation of the gear wheel body, which most researchers have neglected. The effect of rim deformation is not reflected in the ISO and AGMA standards. Many CAD Software packages include a finite element analysis module. Building a 3-D model of a gear bevel wheel is...

The choice of the option of further use of damaged equipment - replacement or repair, is always a difficult task. Rapid technological advances have made it imperative to explore the redesign option. The movement towards a circular economy has added the option of repurposing. It is proposed to compare these options using the diagram Damage - Cost -...

The problem of “rectangling” or “polygonal action” has not been solved for chain drives, either bush roller chains or toothed chains. The search for a fundamentally new chain design was carried out using the heuristic method of enhancement creative activity. It is shown how, using the heuristic techniques that make up the method, the designer comes...

Although vehicles as a whole are symmetric, car crashes rarely follow the symmetric line (crashes are axisymmetric). In this paper, we examine car crashes by an updated Momentum 360 method, and car symmetry helps us easily find out what happens within the accident. We propose an improvement of the Momentum 360 method by taking into account the fric...

This paper describes the prioritization of iterative processes in corporate information systems. The processes are distributed, and each node is a peer. The nodes coordinate their actions through the etcd replicated key-vale store. The nodes are synchronized over NTP and iterate at certain points in time. The paper outlines the main ways of setting...

The permanent consumption increasing of energy, foods, techniques and other goods and serviced worldwide leads to the intensifier of their production and to the constant market expansion. In turn, the processes taking place in some of these productions are responsible for the deterioration of the quality of the environment. Over the last decade, sc...

This paper proposes a new structure and substantiates the choice of a technique for controller design using fractional integration and fractional differentiation. The method of fractional integration is based on extrapolation using a series of integrating and differentiating links, the time constant of which changes symmetrically from one step to a...

Active control systems of today's cars have been used over a vast domain of applications, as they seem to represent a complex compromise between car handling, stability and ride comfort. Finding a balance between these three components is of paramount importance to stability, a well-known prerequisite, directly proportional, for road safety. Active...

Globally, statistical analysis reports show that the most serious vehicle collisions mainly constitute of two-vehicle accidents. The dynamic and kinematic model of car crashes is particularly challenging when requirements for improved accuracy of the analysis are introduced. For more sophisticated models the more accurate the analysis, the more var...

It is well known that analog-to-digital conversion contains several error components (uncertainties). The error generated by time quantization, according to the theory, can be completely eliminated by observing the Nyquist relation between the upper limit of the signal converted spectrum and the conversion frequency. In practice, when recovering a...

It is a very difficult task to control oscillating objects. Even when using the most efficient methods for calculating the controller, a problem of compromise choice in the resulting systems must be solved: what should be preferred, high speed or absence of overshoot and oscillations. Ensuring the fulfillment of both of these requirements is diffic...

Active control systems of today’s cars have been used over a vast domain of applications, as they seem to represent a complex compromise between car handling, stability and ride comfort. Finding a balance between these three components is of paramount importance to stability, a well-known prerequisite, directly proportional, for road safety. Active...

Globally, statistical analysis reports show that the most serious vehicle collisions mainly constitute of two-vehicle accidents. The dynamic and kinematic model of car crashes is particularly challenging when requirements for improved accuracy of the analysis are introduced. For more sophisticated models the more accurate the analysis, the more var...

Large spherical roller bearings are typically used in heavy low speed industrial applications. This sort of sophisticated bearings has achieved nowadays too high dynamic capacity, thanks to the latest modern bearing production technologies and the usage of highest quality bearing steels. Heavy industrial machines from chemical, mining or cement pla...

When solving problems of controlling an object with delay, it is often necessary to approximate a pure delay link with a minimum phase link in order to ensure the possibility of using analytical methods for regulator design. There are many approximation methods based on the Taylor series expansion, as well as modified methods. The most famous one i...

The features of using Role-playing games in educating students - prospective teachers are considered. In practical classes on teaching methods of various disciplines, Role-playing games are often used, associated with conducting a fragment of a lesson or a full lesson. Typically, these practical classes are organized on an empirical level. The vers...

The analysis of the concepts used for engineering analysis of existing product samples is given: Remanufacturing, Repair, Reverse engineering, Redesign, Repurposing. In all cases, there is a decryption phase consisting analysis of technical state and identification. The identification involves the analysis of a design, the identification of units t...

The paper provides a rationale for the use of low-power wireless communication to create non-invasive bionic limb prostheses. The need for such a connection is dictated, on the one hand, by the expediency of using sensors located in various parts of the body, often very remote from each other, on the other hand, by the desire to free the disabled p...

Despite the development of medicine, as well as robotics aimed at helping people with disabilities, most disabled people with missing limbs cannot hope for a full life with the help of bionic prostheses, since these products are made strictly individually, and their control requires expensive surgeries to implant sensors. In addition, such prosthes...

Designing of regulators (controllers) is relevant in many areas of technology. The analytical calculation of the regulators does not justify itself, since it is possible only for objects that have the simplest models; there are relatively few such objects. For objects with a complex model, the method of numerical optimization is most effective. The...

Electrical research in geology is used quite widely and with great efficiency. The use of ready-made signal recorders for these purposes is possible, but not effective enough, since in any case, they need to be modified to provide additional functions. Such functions include the synchronization of measurements with signals from positioning systems...

The compatible work is considered and the obtained results of the known algorithms generating unobstructed trajectories of different length and smoothness are investigated. Their operation is performed within the framework of the developed software product LSTr. The use of the analyzed set of these algorithms on the set of considered sections of th...

It is well known that analog-to-digital conversion contains several error components (uncertainties). The error generated by time quantization, according to the theory, can be completely eliminated by observing the Nyquist relation between the upper limit of the signal converted spectrum and the conversion frequency. In practice, when recovering a...

It is a very difficult task to control oscillating objects. Even when using the most efficient methods for calculating the controller, a problem of compromise choice in the resulting systems must be solved: what should be preferred, high speed or absence of overshoot and oscillations. Ensuring the fulfillment of both of these requirements is diffic...

Intelligent production is the future of industrial production. It is the leading way to a new industrial era and it best defines the concept of the Fourth Industrial Revolution. Getting the real-time data on quality, resources and costs it provides significant advantages over classical production systems. Intelligent production must be built on sus...

The positive emotional impact of a product on the consumers raises their desire to own it. A hybrid framework for emotional user experience package design of educational toys was created. It combines traditional static with new dynamic user experience design. A questionnaire for measuring traditional static user experience was created. Dynamic emot...

In this paper, a model of a car impact against a fixed roadside objects/safety barrier is presented and discussed to solve a mixed task: to determine the pre-impact velocity of the vehicle center of mass taking into consideration the recorded post-impact final rest position. The principle of conservation of mechanical energy was applied, whereas th...

The paper describes a frequency synthesizer for expanding applications and improving the accuracy of a laser device for measuring ultra-small displacements. Such devices are used to measure Earth’s crust deformations. The specified device allows measuring the increment of lengths based on 25 m in two mutually orthogonal directions. Year-round use o...

To conduct research by electrical prospecting, instruments for measuring and recording electric fields with unique characteristics are necessary. Such recorders should work with signals that vary over a very wide dynamic range, as well as over a wide frequency range. The acquisition of ready-made functionally complete recorders for these purposes i...

Various methodologies and tools applied to identification of vehicle and collision impact seek to present more and more accurate solutions to reproduce, restore, recreate and investigate the casualty. Modern computer technology and software provide the tools to solve specific problems developing mathematical modelling of complex mechanical systems...

The method of ANFIS (adaptive neuro fuzzy inference system)was applied to the data resulting from these measurements. The ANFIS process for variable selection was implemented in order to detect the predominant variables affecting the saturation magnetization prediction. This process includes several ways to discover a subset of the total set of rec...

Automation as a branch of engineering science forms and studies methods of control of objects, the main essence of which is to form the structure of the regulator and calculate its coefficients. The number of regulator structures is limited, the most common of them is a serial PID, i.e. a regulator having a proportional, integral and derivative cha...

The paper proposes a method for creating of adaptive automatic control systems based on the method of task separation and combination of solutions proposed by the authors. At the first stage, the task of designing an adaptive system is divided into subtasks, which are solved using robust regulators. At the final stage, decisions can be partially co...

A test-rig for the study of the parameters of the process of automated closing of containers with screw caps is designed and realized. The purpose of the developed test-rig is to study and manage the parameters of the process of automated closure of screw caps. The aim of the experiment is to create a regression model of the process of automated cl...

Methods of designing regulators for locked systems have been studied and developed for more than half a century. Recently, due to the development of computing and software, numerical optimization methods have come to the fore. These methods allow you to effectively calculate the controller for a known mathematical model of a particular object. The...

The application of heuristic methods in the design of transmissions is investigated. The structure of heuristic methods is revealed and the heuristic techniques that compose them are established. These techniques are combined into one generalized method, which allows replacing all the considered methods. A heuristic method specially allotted for th...

In this paper a new method of selection of robotic machine-assembly technology is presented. The core of the technology suggested is the method of fuzzy multi-criteria alternatives selection using the worst-case approach. The automation of the proposed solution is based on the original WMS (Worst Method Solution) software, developed by authors. In...

This article is dedicated to the development of a conceptual model for diagnosing priority areas of science and technology of the Russian Federation. The basic principles of the formation of the model and an enlarged list of controlled indicators allow to conduct a comprehensive assessment of the status and development of priority areas of science...

The current work presents the results of a study of some tribological parameters of Ultra-high-molecular-weight polyethylene (UHMWPE) samples containing different concentrations of multi-walled carbon nanotubes (CNTs) -0.5%, 0.75%, 1% and 1.5% in several instances of contact interaction with the counterpart.

Regardless of the high operational reliability of modern ball and roller bearings and advanced methods for their selection and durability calculation, a significant proportion of the failures in the electric motors, about 51% [1], are of mechanical nature. Often, mechanical damage leads to irreversible engine states and costly replacement. Careful...

As the industrial processes and their control are transitioning to their so called 4.0 version, we are witnessing a dramatic increase in disruptive or destructive attacks on those installations. Naturally, the global connectivity of the Industry 4.0 sensors and actuators, and the use of the Internet as the transfer medium for both the data acquisit...

This paper presents the construction of adequate 3-D computer models for simulation research and analysis of dynamic aspects of caliper disc brakes, as well as of drum brakes, actuated by a short stroke electromagnet or a hydraulic thruster, when these brake types are used in the hoisting mechanism of cranes. The adequacy of the 3-D models has been...

The book is intended for students enrolled in the direction of preparation 27.04.04 “Control in Technical Systems”, on the subject “Computer-aided design tools and control systems” (Bachelor, 4th year). The monograph includes training materials and guidelines for self-monitoring (questions for self-testing). The work on the instructions of the Mini...

Ultrasonic sensors allow us to equip robots with a means of perceiving surrounding objects, an alternative to technical vision. Humanoid robots, like robots of other types, are, first, equipped with sensory systems similar to the senses of a human. However, this approach is not enough. All possible types and kinds of sensors should be used, includi...