Totka Bakalova

A Model of the Dynamic Error as a Measurement Result of Instruments Defining the Parameters of Moving Objects

Abstract The present paper considers a new model for the formation of the dynamic error inertial component. It is very effective in the analysis and synthesis of measuring instruments positioned on moving objects and measuring their movement parameters. The block diagram developed within this paper is used as a basis for defining the mathematical model. The block diagram is based on the set-theoretic description of the measuring system, its input and output quantities and the process of dynamic error formation. The model reflects the specific nature of the formation of the dynamic error inertial component. In addition, the model submits to the logical interrelation and sequence of the physical processes that form it. The effectiveness, usefulness and advantages of the model proposed are rooted in the wide range of possibilities it provides in relation to the analysis and synthesis of those measuring instruments, the formulation of algorithms and optimization criteria, as well as the development of new intelligent measuring systems with improved accuracy characteristics in dynamic mode.

A Gyro-Free System for Measuring the Parameters of Moving Objects

Abstract The present paper considers a new measurement concept of modeling measuring instruments for gyro-free determination of the parameters of moving objects. The proposed approach eliminates the disadvantages of the existing measuring instruments since it is based, on one hand, on a considerably simplified mechanical module, and on the other hand, on the advanced achievements in the area of nanotechnologies, microprocessor and computer equipment. A specific measuring system intended for measuring the trim, heel, roll, and pitch of a ship has been developed in compliance with the basic principles of this concept. The high dynamic accuracy of this measuring system is ensured by an additional measurement channel operating in parallel with the main channel. The operating principle of the additional measurement channel is based on an appropriate correction algorithm using signals from linear MEMS accelerometers. The presented results from the tests carried out by means of stand equipment in the form of a hexapod of six degrees of freedom prove the effectiveness of the proposed measurement concept

A Kalman Filter-Based Algorithm for Measuring the Parameters of Moving Objects

Abstract One of the most complex problems in measuring equipment is related to the provision of the required dynamic accuracy of measuring systems determining the parameters of moving objects. The present paper views an algorithm for improving the dynamic accuracy of such measuring systems. It is based on the Kalman method. The algorithm aims to eliminate the influence of a number of interference sources, each of which is of secondary significance. However, their total effect can cause considerable distortion of the measurement signal. The algorithm model is designed for gyro-free measuring systems. It is based on one of the most widely used elements in the dynamic systems, namely the physical pendulum, due to which measuring systems of high dynamic accuracy and low cost can be developed. The presented experimental results confirm the effectiveness of the proposed algorithm with respect to the dynamic accuracy of measuring systems of this type.

Monitoring Changes in the Tribological Behaviour of CrCN Thin Layers with Different CH4/N2 Gas Ratios at Room and Elevated Temperatures

Totka Bakalova1, Nikolay Petkov2, Hristo Bahchedzhiev2, Pavel Kejzlar1, Lukáš Voleský1 1Faculty of Mechanical Engineering, Department of Material Science, Technical University of Liberec, Studentska 2, 461 17 Liberec, Czech Republic. E-mail: totka.bakalova@tul.cz, pavel.kejzlar@tul.cz, lukas.volesky@tul.cz 2Central Laboratory of Applied Physics, Bulgarian Academy of Sciences, 61, St. Peterburg Blvd. 4000 Plovdiv, Bulgaria. E-mail: petkovnik@gmail.com, hristo_bah@abv.bg

Cathodic Arc Deposition of TiCN Coatings - Influence of the C2H2/N2 Ratio on the Structure and Coating Properties

TiCN thin coatings with various different carbon contents were deposited using cathode arc evaporation of pure titanium in a mixture of N2 and C2H2gasses at a constant pressure of 1.5 Pa. The analyses show a transition from a stoichiometric to a non-stoichiometric coating structure with an increasing C2H2 content. Moreover, the increase in the acetylene in the gas mixture leads to a decrease in the crystal phase from pure polycrystalline to pure amorphous. Nanohardness changes from 30.4 to 4.4 GPa and the cohesive failure of the coatings is in the range of 61 - 72 N. The tribology is estimated by the Ball-on-Disc method and an Si3N4 ball as the counterpart. The measured coefficient of friction is in the range of 0.2 - 0.56.

Influence of Coating Deposition Parameters on the Mechanical and Tribological Properties of TiCN Coatings

This paper is a continuation of our previous work. The article presents an investigation of the influence of coating deposition parameters, in particular a variation with 50% of both cathodic arc current and bias voltage, on the mechanical and tribological properties of TiCN coatings deposited by the cathodic arc evaporation of metals at a constant gas ratio. The thicknesses of the coatings are measured by the Calotest method using a 30-mm hard steel ball. The determined values are in the range of 734 – 1534 nm. Surface morphology and chemical composition are estimated by a Scanning Electron Microscope (SEM) and an Energy Dispersive Spectrometer (EDS) of SEM. The determined values of nanohardness are in the range of 10 - 23 GPa and adhesion values are in the range of 28 - 70 N. Tribology of the TiCN coatings is investigated with three different load forces (3N, 5N and 8N) by the CETR UMI Multi-Specimen Test System from Bruker with an Si3N4 ball counter-body. The friction coefficient is measured in the range of 0.19 - 0.23. Coating wear and wear of the counter-body are calculated, according to the standard EN1071-13:2010, wherein the values of the latter are in the range of (2.5 - 30) x 10-6 mm3.

Influence of Coating Process Parameters on the Mechanical and Tribological Properties of Thin Films

Titanium carbonitride (TiCN) thin films with differing C content were deposited by cathodic arc evaporation of pure Ti in a gas composite environment of N2 and C2H2. Scanning electron microscopy (SEM), scratch test, mechanical profilometer and “ball-on-disc” tribometer methods were used to characterize the surface, the coefficient of friction (CoF) of the TiCN thin films and the evaluated wear. An increase of the C2H2 fraction in the gas environment leads to a continuous increase in the deposition rate of the TiCN thin films, as well as an increase in the adhesion of the films to the substrate and the values of the CoF. Tribological test results (when tested against Si3N4 balls) show an increase in the friction coefficient of the TiCN from 0.08 to 0.32, with increasing carbon concentration in the film. The CoF decreases rapidly to 0.06 at a C content of 20.6 at.%, N 38.4 at.% and Ti 41.0 at.%.

The Impact of the Deposition Parameters on the Mechanical Properties of Thin Carbon Layers

The article describes the effect of the pressure in the chamber during the deposition of thin layers on the basic mechanical properties of thin layers based on carbon. Monitoring parameters are mainly nanohardness, coefficient of friction and adhesion between the layer and substrate. This parameters are observed using nanohardness tester and scratch tester. All observed layers had the same thickens of layers. Carbon layers generally have poor adhesion to the substrate. To improve the adhesion, is used the interlayer of titanium which is between the substrate and carbon layer. Carbon layers are mostly used for their very good sliding properties especially in cases where can not be used process fluids or where is necessary to reduce the friction between the two materials. The carbon layer can also be used in medicine (for their biocompatibility), for machine tools (for their hardness and abrasion resistance) or as barriers layers (for their high chemical resistance).

Tribological Properties and the Abrasion Resistance Thin Films of Chromium Nitride

Chrome nitride (CrN) and CrN/Cr thin films were grown on EN ISO HS6-5-2 tool steel, which has been used as a substrate material. It is a high-speed Mo-W steel with high toughness. Chrome nitride thin films were deposited using a RF PA CVD/Magnetron Sputtering (MS) system at a gas flow ratio of 15/13 sccm of Ar/N2. During the deposition process the pressure in the vacuum chamber was 0.9 Pa, the deposition Ubias and deposition time were different. The parameters of the process influence properties of the thin films were microstructure, hardness and adhesion to the substrate, etc. Optimal selection of process parameters is needed to achieve particular property combinations. The basis of the tribological measurements was the “ball-on-disc” testing method. Tribological testing (EN1071-13:2010) was conducted using a ball made from Si3N4 with a diameter of 6.350 mm, with a constant load of 3N at room temperature and humidity of 40±2 %. A Zeiss AXIO Imager M2 light optical microscope and a Dektak XT TM mechanical profilometer were used to evaluate the wear of the friction pairs at a load of 6mg and the size of the measured area of 200x1000 μm. The basis of the tribological measurements is the “ball-on-disc” testing method. Tribological testing (EN1071-13:2010) was conducted using a ball made from Si3N4 with a diameter of 6.350 mm, with a constant load of 3N at room temperature and humidity of 40±2 %. A Zeiss AXIO Imager M2 light optical microscope and a Dektak XT TM mechanical profilometer were used to evaluate the wear of the friction pairs at a load of 6mg and the size of the measured area of 200x1000 μm.

Biocompatibility of Surfaces of TiCN Thin Films

A series of titanium carbonitride (TiCN) films with differing C content were deposited by cathodic arc evaporation of pure Ti in a gas composite environment of N2 and C2H2. The increase of the C2H2 fraction in the gas environment leads to a continuous increase in the deposition rate of the TiCN thin films, as well as an increase in the adhesion of the films to the substrate. To evaluate the interaction of the material with the bacteria Escherichia coli CCM 3954 a method was used based on the ČSN EN ISO 56 0100 standard. The bacteria were inoculated in a liquid culture medium. It was observed that the monitored surfaces support the development of bacterial populations of E. coli depending on the type of TiCN thin films.